Karl Busch, a German scientist, invented the method of vacuum packaging during the 1950s. He first used this in packaging technology to extend the shelf life of meat products. During this period, vacuum packaging only serves as a means to extend the shelf life of food that individuals would consume during the days of war. A decade later, Busch introduced a machine that would allow manufacturers to vacuum pack food products in an industrial scale.

Today, vacuum packaging is one of the common methods of packaging food. Its wide range of applications include fruits and vegetables, dried fish, meat, and dairy products. In many households, a small home vacuum sealer can be used to vacuum pack leftovers.

Let’s discuss vacuum packaging in more detail.

What is vacuum packaging?

Vacuum packaging is a type of food preservation method that involves modifying the atmosphere inside the packaging―it particularly removes air or oxygen. Hermetically sealing the package results in a near-perfect vacuum. This packaging technology uses a highly flexible plastic packaging that molds to the contour of the product being packaged.

Vacuum packaging is based on the principle of air (oxygen) removal inside the food packaging. A wide range of microorganisms, from bacteria to fungi, require various things to live—including oxygen.

Microorganisms can be classified according to their oxygen requirements—aerobic and anaerobic. Aerobic microorganisms are those requirement air to grow, whereas anerobic microorganisms are those that can tolerate the absence of air. Both of these types can be found in foods and spoil them. So, by removing air, food can be preserved and extend its shelf life.

And since anerobic microorganisms can also be found in food vacuum packaging is often partnered with another type of preservation method to make it more effective. This is the reason why some vacuum-packed foods like pasta, frozen meals, and seafood, in the supermarket are put in display freezers.

Dried nuts, dried fruits, and cured meats in vacuum packaging, on the other hand, are shelf life stable because in addition to the lack of oxygen, the products are also low moisture and contain high concentration of sugar/salt. Hence, they can be placed at room temperature.

In addition to removing air available for microbial growth, vacuum packaging also controls the oxidation of fatty acids that results in rancidity in food. As the name suggests, oxidation occurs in the presence of oxygen. If present, it reacts with unsaturated fats that is commonly found in nuts, meats, and other similar products. This is what causes off flavor, off odors and other undesirable changes in food.

How does it work?

Vacuum packaging is the final step in the production process for most products. As much as possible, this is completed immediately to minimize exposure to elements, particularly air.

To do this, the food that has undergone the final process is placed in a suitable packaging. The packaging material should be impermeable to various external elements, including air and moisture. Commonly used for vacuum packaging include nylon, Polypropylene (PP), Polyethylene (PE), Polyester (PET), laminated films, and aluminum foil.

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With the product inside the packaging, it is brought inside a vacuum packaging chamber. This device can suck the air and oxygen out of the packaging by up to 99.8%. An effectively vacuum-packed container produces a skintight wall appearance. Thus, there should be no air pockets, especially along the edges.

After turning the packaging into a vacuum, the pack is closed by heat sealing or pulse sealing.

Special considerations

Vacuum packaging can be a good option as one way of food preservation. In general, vacuum-packed food stored can last from 6 months up to 2 years at freezing temperatures, and 1 or 2 weeks at refrigeration temperature.

Although this is the case for most products, there are several considerations when using vacuum packaging. For example, vacuum packaging should only be used for food that does not support the growth of Clostridium botulinum. This is because this bacterium is an anaerobic―it can survive inside a vacuum packaging.

Cl.botulinum is a bacterium that produces botulinum toxin, one of the most toxic substances known, and is commonly associated with improperly canned food products. Ingesting botulinum-contaminated food may result in paralysis or death.

As earlier mentioned, the storage temperature for vacuum-packed food should at refrigeration of at least 45°F (7°C) or lower. This should be maintained at all times. Anaerobic pathogens or disease-causing bacteria, including Cl.botulinum, are capable of increasing their growth rate exponentially as the temperature increases. Placing vacuum-packed foods at low temperatures not only slows their growth rate down, but it also inhibits toxin production.

Perhaps the best way to prevent food illness as a result of ingesting contaminated vacuum-packed food is to have the product shelf life to not exceed 10 days. The storage temperature requirement is best to be prominent on the package. And the shelf life determined by the initial processor should not be extended. This is particularly important for meat, seafoods, and other perishables.

Is the packaging compromised?

The common signs that a food has already spoiled include off odor, off flavor, discoloration, and undesirable texture (slimy, for example). In the case for vacuum packaging, its appearance can tell if something is already going bad.

A proper vacuum packaging is tightly sealed, skintight, and it contours to the product. For this reason, bulging or bloating inside the package can easily be seen. Bulging inside a vacuum packaging is concerning because it could be caused by gas produced by bacteria. Yes, microorganisms can produce gas bubbles, which is a byproduct of their metabolism. This is the same way yeast like Saccharomyces Cerevisiae produce bubbles during fermentation. But in this case, gas bubble might be caused by harmful microorganisms, particularly Cl.botulinum.

The post What Is Vacuum Packaging In Food Preservation? appeared first on The Food Untold.

Ohmic heating, also called Joule heating, is one of the few food processing methods that uses electricity. James Prescott Joule discovered that electricity gives off heat, and this heat is produced from resistance (ohms) in 1841. To put it simply, electricity is converted into heat energy. This discovery has led to believe that this process can be used to process and preserve food.

This has turned into fruition when Ohmic heating was used to pasteurize milk in the late 19th century. The process involved flowing milk between two plates of different electric voltages. At the turn of the 20th century, progress in Ohmic heating was considerably limited though.

This was due to various reasons, mainly technological constraints (lack of suitable electrode materials), lack of the understanding of the process, and financial considerations. In 1930s, the process was called “Electro-Pure”. In the 1950s, a process of sterilizing milk using Ohmic heating was developed. However, the process was discontinued because of the high operational costs and the excessive use of electricity.

Interest in Ohmic was revisited in the 1980s because there was a need for a process that could efficiently sterilize liquid–large particle mixtures. Today, Ohmic heating has become an attractive option for food manufacturing. This is in large part of the unending research and study about the technology.

Let’s discuss Ohmic heating further.

What is Ohmic heating?

Ohmic heating is a food process wherein electric current is converted into heat energy to heat the food. It is also known as Joule heating, electrical resistance heating or resistance heating, and electro-heating. A Ohmic heating device commonly consists of a power source, an electrode, and a way to contain the sample, a vessel or tube, for example.

Ohmic is performed by passing alternating current (AC) or direct current (DC) to the food material placed between electrodes. As the electricity hits the food, salts, water and other components resist this energy and generates heat.

This food process is based on the principle of electrical resistance. Electrical resistance is the measure of how resistant a material is to the flow of electric current. In the case of Ohmic heating, the food material is the electrical resistor. The resistance depends on various factors, including the composition of the food, and the amount of moisture present.

Because of this resistance, the electric energy is dissipated and converted into heat. This heat generation is rapid that allows quicker and uniform heating of food than in thermal-based food processes. Ohmic heating is particularly effective for liquid–particle mixtures as they allow uniform heat transfer.

Ohmic heating vs conventional heating methods

Conventional thermal processing methods such as boiling, sterilization, and canning have been known to cause product quality degradation because of slow convection and conduction heat transfer.

Slow heat transfers in conventional heat treatments are fully known in the food industry. In canning, food is heated by conduction, wherein heat is transferred from one material to another. In the case of canning, heat is transferred from the can to the food. This heat transfer is slow, especially if the can is considerably larger or the food is densely packed inside.

This is where Ohmic heating is a much better option. With Ohmic, the entire food mass can be heated volumetrically. It is possible to heat large portion of food by up to 1 in.3. And since Ohmic heating can heat food rapidly, it can transfer heat to the inner portion without difficulty.

This is unlike conventional methods that sometimes overprocess the surrounding liquid portion of the food being heated as it transfers heat to the inner portion. This uneven heating diminishes quality.

In nutrient retention for example, it has been studied that food that has undergone conventional heat treatments contain lower nutrients, particularly heat-sensitive ones.

One of the findings in this study is the reduction vitamin C in food processed under Ohmic and conventional heating. In conventional heating, the product’s vitamin C reduced by 13.58%. Ohmic heating, on the other hand, was not that different from unheated sample. Another study found heating under Ohmic helps retain significantly higher antioxidant activities and essential minerals essential minerals calcium, potassium, and phosphorus.

This just suggests that Ohmic heating is better at preserving food quality, especially nutrients, than conventional methods.

Uses and applications

The first use of Ohmic heating was for sterilizing milk in the 19th century. Since then, its usage than expanded to various sectors in the food industry. It is now also used for food items such as fruit juices, purees, meat, canned goods, and vegetables.

Let’s briefly discuss some of the processes Ohmic heating is used for.

Thermal processing

Pasteurization and sterilization have long been used for processing liquid like milk and fruit juices. Pasteurization involves temperatures that destroys and reduce the levels of spoilage microorganisms, whereas sterilization destroys all microorganisms, including beneficial ones (probiotics, for example).

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Integrating Ohmic heating with these thermal processes helps rapid and uniform heating to maintain product quality. In the United States, Ohmic heating is used to produce liquid egg product.

Fermentation

Fermentation is an anaerobic process that uses microorganisms to convert carbohydrates such as sugar into alcohol. Examples of fermented products includes kimchi, yogurt, and wine.

The application of Ohmic heating in fermentation has been less common than when used with thermal processes. One beneficial use of it in fermentation is the reduction of acidity in cocoa and coffee beans. While acidity may be desirable to some varieties of coffee, reducing its levels in many varieties often results in a smoother and rounded flavor. Arabica coffee is one example of coffee that naturally contain high acidity.

This study proved that using Ohmic heating can effectively reduce this acidity to a more desirable level. The time and temperature variations used in the study resulted in acid levels between 0.18% and 0.73%.

Thawing

Food thawing may be a relatively simple step in food preparation. But doing it in a much better way can help food processors save resources and retain quality. In most cases, there would be moisture loss or drip loss. This is evident when the food is drier. Drip loss is commonly associated with meat, seafood, fruits, and vegetables.

Drip loss occurs because the ice crystals that ruptured that cell walls turns into water and escapes from the food. There is more drip loss if air thawing is done because the process is very slow. With Ohmic heating, thawing is rapid because the heat is generated from the food itself, instead from the surface inward.

Another benefit of Ohmic heating for thawing is that there is not a need for water. Hence, no wastewater is generated. This also saves resource and operating cost.

Blanching

Similar to thawing, blanching may also result in moisture loss. However, the mechanism of how it occurs is different. With blanching, the elevated temperature ruptures the cell wall of the food that allows the water to escape and nutrients to leech into the blanching water.

With Ohmic heating, it is possible to reduce or prevent moisture loss and leeching. Its rapid heat generation allows uniform heating and prevents overcooking of the surface. A study found that blanching with Ohmic heating also removes the need of cutting (a process that is commonly done prior to blanching) large pieces of food, especially vegetables. The reason here is uniform and rapid heating that traditional blanching cannot achieve. This particularly important for delicate vegetables.

Extraction

Uneven temperatures can also lead to inefficient extraction of certain components from food materials. Examples of extraction are juicing from fruits, soymilk from soybeans, and beet dye from beets.

Traditional extraction methods apply heat from the outside to the inside of the sample. Since this manner of heat transfer is relatively slow, there is an extended processing time. Not only this affects the yield, it also affects the quality of extraction. This is especially true if what involved in the extraction are heat-sensitive compounds like vitamins.

With Ohmic heating, the quality of extract is better preserved. This statement is demonstrated in this study of Ohmic heating-assisted extraction of anthocyanins from black rice bran. Anthocyanins are natural pigments responsible for the color of eggplants, blueberries, purple grapes, and cherries. Anthocyanins are heat sensitive. But with Ohmic heating used in the study, the method had better colorant yield, as well as bioactive compound activity.

References:

V. Vaclavik, E. Christian (2014). Essentials of Food Science (4th edition). Springer.

S. Rahman (2007). Handbook of Food Preservation (2nd edition). CRC Press

P. Fellows (2000). Food Processing Technology (2nd edition). CRC Press

P. Zeuthen, L. Bogh-Sorensen (2003). Food Preservation Techniques. CRC Press

The post Ohmic Heating (Joule Heating) Of Food: How Does It Work? appeared first on The Food Untold.

Non-thermal based processing methods like high-pressure processing (HPP) are relatively novel techniques. Thermal-based ones have been used for the long time. But these non-thermal based techniques have been recently garnering attention in the food industry because they are able to preserve food while minimizing the loss of quality.

In this blog post, we’ll discuss the specifics of high-pressure processing. We’ll discuss how it works, its benefits, and its applications in the food industry.

What is high-pressure processing?

As the name suggests, high-pressure processing in a type of food processing method wherein extremely high pressure is used to eliminate harmful microorganisms and preserve the food. This type of processing method is innovative because it does not use heat or chemicals. The latter, in some instances, is not favorable because it can cause undesirable changes like browning or nutrient degradation. This is why high-pressure processing is desirable in certain food products like fruits, vegetables, and other perishable items.

The first high-pressure processed foods were fruits kiwi, strawberries, and apple jams, all of which produced by Meidi-ya Food Co., Japan. The color and taste of the jams was natural.

It is worth noting though that although HPP can prolong shelf life, it does not pasteurize food. That means after processing, the food must be kept at refrigeration temperature. This is especially true for low-acid foods like milk, vegetables, and soups. High-pressure processed food can last up to 120 days or 4 months.

HPP-made food products can more costly than used produced using other methods, mainly heat treatments. The factors that contribute to this include the especial packaging requirement, lower production capacity, and low market demands. All of this are which are expected for novel technologies. However, consumers may benefit from extended shelf life, quality, and the value-added products, which cannot be achieved with other processing methods.

Today, HPP is used mainly on food products with high moisture contents such as ready-to-drink meats, seafood, fruit juices, and prepared vegetables. HPP is not as effective in dry products because moisture is necessary to carry out the process.

How does it work?

HPP involves subjecting the food at extremely high hydrostatic pressure. Prior to this, the food is usually packed in a highly flexible sterile packaging container. And then, it is put in a chamber where it is pressurized. The pressure employed varies and can reach up to 87,000 lb per square inch (psi) for 3 to 5 minutes. This pressure that hits the food is uniform on all the sides. For this reason, the shape of the food is retained—not damaged or squished.

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How high-pressure processing works depends on the Le Chatelier’s Principle. According to this, any reaction or change or phase transition with an increased in volume will be favored at high pressures, and reactions that involved an increase in volume will be inhibited. However, because many food systems are complex, the changes and reactions that can occur under high pressure can be difficult to predict at times.

Fortunately, recent progress on research and study about HPP has led to knowing the various effects of high pressure on chemical and enzymatic reaction, microbial inactivation, and nutrient retention.

In terms on biological retention, for example, the membrane of the microorganism is the most probably area for disruption. Furthermore, high-pressure can also inactivate key enzymes, particularly those involved during DNA replication and transcription. The combination of these factors is lethal to vegetable microorganisms.

Why high-pressure processing?

HPP is similar to other kinds of processing methods—they destroy harmful microorganisms and extend the shelf life of various products. But as I have already mentioned, HPP can be a much better option for a few reasons.

HPP merely depends on high pressure to do its job. Hence, there is no covalent bonds that are broken during processing. When broken, covalent bonds tend to produce free radicals or chemical by-products. Free radicals are highly reactive molecules because they contain an unpaired electron. Prolonged exposure to free radical can be harmful to human health because they can damage cells and DNA.

Because HPP does not produce free radicals, HPP practitioners do not require approval from the Food and Drug Administration (FDA) and Food Safety Inspection Services to operate.

Another reason HPP can be a better option is nutrient retention. It is just one of the few non-thermal processes that do not use heat to process food. Other similar methods include osmotic dehydration, irradiation, and pulse electric fields.

HPP is particularly beneficial in processing foods that contain vitamin B, C, and antioxidants lycopene and beta carotene. These are nutrients that degrade at high temperatures. This behavior is demonstrated in this study, wherein strawberry and blackberry purees produced by HPP reduced antioxidant activity by only 5%, whereas thermally processed ones reduced by 25%.

References:

V. Vaclavik, E. Christian (2014). Essentials of Food Science (4th edition). Springer.

S. Rahman (2007). Handbook of Food Preservation(2nd edition). CRC Press.

R. Rajenran, A. George, N. Kalarikkal, S. Thomas (2019). Innovative Food Science and Emerging Technologies. CRC Press

The post High-Pressure Processing Of Food: How Does It Work? appeared first on The Food Untold.

Aluminum foil was first used in food in the early 20th century as packaging material for chewing gum and candies. Fast forward to the present, it can be used for preservation and cooking—grilling, baking, and grilling.

And yes, that answers the question—food wrapped in aluminum foil can be heated. But this depends entirely on the appliance you are working with. You can use aluminum foil in the oven and air fryer (but with caution), but not in the microwave oven.

Using aluminum foil in the oven

There are various ways you can utilize aluminum foil when working when an oven. You can either use it to a line baking sheet, as a wrapping, or a drip pan.

Aluminum foil is a great conductor of heat. It is why it is often used for in the baking to help cook the food much fast and evenly. This is particularly useful for food items that require consistent temperature all throughout the baking process.

One good example is during roasting of large cuts of meat. Due to the size, there should be consistent temperature for slow and even cooking. By wrapping the meat in aluminum foil, the moisture and heat get trapped. This allows the food to cook evenly.

While it is true that using aluminum foil in the oven is generally safe, it’s important to monitor both the cooking time and the type of food you’re preparing.

It’s advisable to limit the use of aluminum foil for shorter cooking periods. Although aluminum foil can handle high oven temperatures, prolonged exposure may cause it to react and dissolve into the food.

As for the kind of food items you should be worried about, acidic foods, such as citric fruits and vinegar may also lead to aluminum foil leeching. Temperature alone makes aluminum foil less reactive. But the presence of acidic substance such as those mention triggers a chemical reaction. This reaction dissolves aluminum foil, and elevated temperature accelerates it.

One study has found that aluminum-contaminated food may result in brain disorder such as Parkinson’s disease. So if you are going to cook something with an acidic ingredient, use an alternative such as stainless steel or glass.

Using aluminum foil in the air fryer

Aluminum foil also be placed in an air fryer the same way as in an oven. But there is a difference on how it many affect cooking. Ovens use radiant heat to cook food, whereas air fryers use hot air around the food to cook it.

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In an oven, you can easily wrap food completely. But the same cannot be done with working with air fryers. Instead of radiant heat, air fryers use hot air to cook. So while it is possible to put aluminum foil inside an air fryer, you should allow enough space to allow the hot air to circulate around the food.

If the foil blocks the flow of the hot air, the food will not be cooked properly. Furthermore, the cooking time will be longer. In some cases, the restricted air flow may cause the inside of the air fryer to overheat and cause component damage.

Using aluminum foil in the microwave

No, you really cannot use aluminum foil for cooking food in the microwave. Do not ever try. And here is why.

Microwave works differently than the first two kitchen appliances. It cooks food by emitting electromagnetic waves. These waves make the water molecules present in the food to vibrate. This vibration is very rapid that it generates heat strong enough to cook the food from the inside and out.

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While foods absorb the waves, metals like aluminum foils reflect them. And when the waves just bounce off, a strong electric force is formed between the foil and inside of the microwave. If this electric field becomes very strong, the air molecule inside become ionized. This means the molecules are broken down into charged particles, allowing electricity to cross between the foil and the microwave or to another portion of the foil. This reflection creates visible sparks inside the appliance.

This is a serious safety concern. The sparks could be in contact with something flammable inside, such as food oil, and cause fire. When this occurs, it is likely for the electronics and other essential components of the microwave to malfunction.

Conclusion

Oven and Air fryer

Aluminum foil is generally safe in ovens and air fryers (with caution). It helps cook food evenly, especially for larger cuts of meat in the oven. However, limit its use for shorter cooking times to avoid potential leaching into food. Be mindful of acidic ingredients as well. Opt for alternative materials like glass or stainless steel for acidic foods.

Microwave

Absolutely not recommended! Microwaves use electromagnetic waves that cook food from the inside out. Metals like aluminum foil reflect these waves, creating sparks – a serious fire hazard. Additionally, it can damage the microwave’s components.

The post Can Food Wrapped In Aluminum Foil Be Heated? (In the Oven/Air Fryer/Microwave) appeared first on The Food Untold.

Kimchi is a traditional Korean food made from various vegetables, usually cabbage. Its unique taste is a result from a weeks-long fermentation. If you freeze kimchi, would it be the same? Would it still be safe for consumption?

Fermentation is a preservation method wherein beneficial microorganisms consume the sugars present in food. In return, alcohol or acid are produced. In the case of making kimchi, lactic acid bacteria (LABs) convert the sugar in lactic acid. This acid is mainly responsible for the tangy and sour taste of kimchi. The initial fermentation process is usually allowed to take place for 1 to 2 days at room temperature.

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After that, the kimchi is transferred and stored at refrigerated temperature for several weeks to months. Refrigeration does not stop the fermentation process; it only slows down fermentation. This allows for the complex flavors to form. But if the kimchi has been stored in the refrigerator for an extended period, it may become strongly sour, and it is not really desirable.

Freezing kimchi for later use

This is when freezing is a great option. And yes, you can definitely freeze kimchi. Not only it prevents over fermentation, but it also extends its shelf life for roughly 1 year.

The traditional practice of storing of kimchi in Korea is either refrigeration or earthenware jar (onggi). The cool temperature involved with the two methods allow for natural fermentation of kimchi. Nowadays, the busy lifestyle in the country has changed how they store it. This is especially true for individuals who are used to making kimchi in large batches.

To prevent food waste, they would store kimchi in the freezer. If you wish to do the same, it is better that the kimchi has aged or fermented sufficiently. Remember that fermentation requires time in order for the texture, flavor, as well as nutrients to fully developed. If you store kimchi in the freezer before it reaches its maturity, fermentation stops, preventing it to reach its optimum quality.

Refrigeration temperature encourages slow fermentation, while freezing temperature stops it. The typical refrigeration temperature for storing kimchi is between 36°F (2°C) and 43°F (6°C). The freezing temperature, on the other hand, is at 32°F (0°C) and below. This lower temperature halts several reactions, particularly microbial activity.

As I have already mentioned, LABs are the main reason why kimchi undergoes fermentation. These bacteria are temperature sensitive. They thrive at room temperature and cool environments. And at freezing temperatures, they become inactive until the environment becomes tolerable again. However, the microbial population and their activity might be reduced due to stress and cell damage.

So while freezing is a safe and good option for storing kimchi for later use, make sure that it has been fermented fully. The texture, taste, and nutrients are locked once it is frozen and after thawing.

Proper freezing of kimchi

Want to make sure your kimchi is properly stored in the freezer? Here are several things you can do to.

Like any other frozen food, freeze kimchi by portions. This way, you will be able to take out the amount you only need. Frequent freezing and thawing gradually diminishes the quality of kimchi. During freezing sharp ice crystals penetrate the cells of the vegetables. Repeated freezing and thawing will repeat will ice crystal formation. Over time, the kimchi would become mushy and soft, and the flavor also is lost as a result of cell structure damage.

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To prevent this, place kimchi in airtight and freezer-safe container. You can also use freezer bags. These containers can keep air and moisture out. These and other freezer elements, when present inside the container, causes oxidation that negatively affects the texture and flavor of food.

Earlier, I said that frozen kimchi can last up to 1 year. It is true. But its quality might not be up to your liking. Most frozen foods, including kimchi, are actually good, in terms of quality for 3 to 6 months. So, you would want to consume frozen kimchi within this time frame. To make sure of it, label the container the date when it was first stored for easy tracking.

The post Can You Really Freeze Kimchi? appeared first on The Food Untold.

Food preservation has been a crucial practice throughout human history, dating back to ancient times when refrigeration and modern preservation methods were nonexistent. Ancient civilizations developed various techniques to preserve food, including salting, fermentation, and drying. In fact, there is evidence indicating that Middle Eastern and Oriental cultures were actively engaged in drying foods as far back as 12,000 B.C. Today, thanks to modern technology, a wide range of preservation techniques are available and continuously improving. One such effective food preservation technique is freezing.

By definition, freezing refers to the process of lowering the temperature of food items to below their freezing point, typically to around 0°C (32°F) or lower, in order to preserve them for extended periods. This preservation method involves storing food in a freezer or other cold environment where the low temperature inhibits microbial growth and enzymatic reactions that lead to spoilage. By freezing food, moisture within the food is converted into ice crystals, which slows down chemical reactions and microbial activity, effectively halting the deterioration of the food’s quality, flavor, and nutritional value.

Let’s discuss further.

HOW FREEZING WORKS

When food undergoes the freezing process, its water content undergoes a transformative phase change as the temperature drops. Initially, water molecules within the food coalesce and align to form ice crystals. These crystals disrupt the structural integrity of the food’s cells, causing them to expand. Consequently, the growth of microorganisms such as bacteria, yeast, and mold is significantly inhibited.

The inhibition happens because these organisms depend on water for their growth and reproduction. Water plays a vital role in life, serving as a medium for biochemical reactions, dissolving nutrients and waste products, and providing structural support to cells. When lacking adequate water, microorganisms cannot perform essential metabolic processes, absorb nutrients, or uphold cellular structure and function, thus hindering their growth and reproduction.

Moreover, enzymes that catalyze biochemical reactions within the food are rendered inert at low temperatures, further impeding degradation processes. When fruits are frozen, the enzymes responsible for ripening and softening, such as pectinase and cellulase, are deactivated due to the cold temperatures. For instance, in frozen strawberries, the enzyme polygalacturonase, which breaks down pectin and leads to fruit softening, is inhibited. As a result, the strawberries maintain their firm texture and structural integrity even after thawing, preserving their quality and preventing mushiness.

The rate at which food freezes plays a pivotal role in preserving its overall quality. Rapid freezing, facilitated by placing the food in a freezer maintained at a sufficiently low temperature, fosters the formation of small ice crystals. These small crystals exert minimal damage on the cellular structure of the food. Conversely, slow freezing permits the formation of larger ice crystals. These larger crystals can puncture cell walls, resulting in a loss of texture and moisture when the food is eventually thawed.

FREEZING FOOD PROPERLY

Ensuring proper freezing of food preserves its quality, taste, and nutritional content by minimizing the formation of ice crystals and averting freezer burn. Adhering to appropriate freezing methods like rapid freezing and employing airtight packaging helps extend food shelf life, and minimize waste.

Choosing the appropriate packaging

When choosing packaging materials for freezing food, focus on options that provide both moisture-proof, airtight seals and durability to endure freezing conditions without becoming brittle or cracking. Consider utilizing alternatives such as resealable plastic bags, vacuum-sealed pouches, freezer-safe containers, and aluminum foil. By utilizing moisture-proof, airtight packaging, you protect against freezer burn. Freezer burn is a phenomenon that occurs when moisture evaporates on the food’s surface, leading to the formation of ice crystals, dehydration, and oxidation. This process alters the texture, flavor, and appearance of the food.

Preparing food items for freezing

Proper preparation and packaging are vital steps to maximize the quality of frozen food. It helps to minimize the risk of spoilage and ensures that frozen food remains a convenient and nutritious option for consumption.

• Flash freezing

During flash freezing, the food is exposed to either very cold air or liquid nitrogen, which freezes it rapidly. This rapid freezing helps to form smaller ice crystals within the food, minimizing damage to its cellular structure. When doing this, arrange each food item or portion in a single layer on a baking sheet lined with parchment paper. Allow them to freeze until firm before transferring them into freezer bags or containers. This method prevents the items from clumping together, making it easier to portion and retrieve them when needed.

• Prepare food items in portions

To expedite the thawing process and minimize food waste, it’s advisable to partition food into smaller servings before freezing. This strategy not only promotes faster thawing but also lowers the likelihood of discarding excess food. Moreover, dividing food into smaller portions enables you to thaw precisely the amount required for a particular meal, rather than defrosting an entire batch unnecessarily.

• Prevent overcrowing

Overcrowding can impede airflow and disrupt the freezing process, potentially leading to uneven freezing and extended freezing times. This can compromise the quality of the frozen food, affecting its texture and taste. By allowing adequate space between items, you facilitate efficient cooling and freezing, preserving the freshness and quality of your stored food items. Additionally, organizing the freezer with ample space ensures easier access to items and reduces the risk of items becoming buried and forgotten, ultimately minimizing food waste.

PRACTICES FOR COMMONLY FROZEN FOODS

Baked goods

Wrap individual servings of baked goods, such as muffins, cookies, and bread, with plastic wrap or aluminum foil before storing them in freezer bags or containers. Wrapping them individually allows for easy retrieval and thawing of single servings without affecting the rest.

For larger baked items like cakes or pies, freeze them without covering on a baking sheet until they become firm. Afterward, tightly wrap them with plastic wrap and aluminum foil. Larger baked items, due to their size, require a different freezing approach. Freezing them uncovered initially allows them to set without trapping moisture, preventing soggy textures. Subsequently, tightly wrapping them with plastic wrap and aluminum foil ensures maximum protection against freezer burn and maintains their quality during storage.

Meats and seafoods

Divide meats and seafood into individual meal portions before adding seasoning or marinade according to preference. This step involves dividing larger cuts of meat or seafood into smaller, ready-to-cook portions. Doing so allows for easier handling and portion control during meal preparation.After portioning and seasoning, lay the individual servings in a single layer on a baking sheet. Freezing them in this manner helps prevent them from sticking together and allows for uniform freezing, ensuring that each portion freezes evenly. After the portions have frozen completely, transfer them into freezer-safe bags or containers. This step helps protect the portions from freezer burn and maintains their quality during storage.

Fruits and vegetables

Prepare fruits and vegetables by washing, peeling, and cutting them into desired sizes before subjecting them to blanching in boiling water, followed by rapid cooling in an ice bath. Blanching helps to partially cook the produce, which can help preserve color, texture, and nutrients before freezing.

Once blanched, remove any excess water from the produce to prevent ice crystals from forming during freezing. Patting them dry helps to remove surface moisture, which can lead to freezer burn if left behind.

Soup and stews

Ensure that soups and stews have cooled down entirely before transferring them into containers suitable for freezing, leaving a slight gap at the top to accommodate expansion. Allowing soups and stews to cool completely before freezing prevents condensation inside the containers, which can lead to freezer burn. Leaving space at the top allows for the expansion of liquids as they freeze, preventing the containers from cracking or bursting.

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Powdered milk, alternatively termed dried milk or milk powder, undergoes a processing method where the liquid component is extracted, resulting in a finely textured powder. In the United States, it must not exceed 5% moisture by weight. This powder can be reconstituted with water to yield a liquid milk suitable for consumption. Valued for its prolonged shelf life, convenient storage, and adaptability in diverse culinary and food manufacturing uses, powdered milk holds significance in various applications.

HOW IS IT MADE?

The process commences with the collection of fresh milk from dairy farms, typically sourced from cows, though other mammalian sources may also be utilized. After collection, the liquid milk undergoes a dehydration process, primarily achieved through techniques such as spray drying or roller drying.

Spray drying

The first step in spray drying involves preparing the milk by homogenizing it to ensure a uniform mixture. The liquid milk is then pumped through a specialized nozzle, breaking it into tiny droplets. These droplets are introduced into a drying chamber, where they come into contact with hot air. The heat causes the moisture in the droplets to evaporate quickly, leaving behind dried particles of milk solids. The size of the resulting powder can be controlled by adjusting the spray nozzle and regulating the drying conditions. This allows manufacturers to produce a range of powdered milk products with varying textures and applications.

Preserving nutritional content stands out as a primary benefit of utilizing spray drying in the production of powdered milk. This method is specifically engineered to reduce heat exposure, safeguarding essential nutrients like proteins, vitamins, and minerals from degradation. This ensures the maintained nutritional value of the end product.

Roller drying

Roller drying, also known as drum drying, is an alternative method for producing powdered milk. It is also used for the manufacturing for other dehydrated flakes and powders. In this process, liquid milk is applied onto the surface of a heated drum or roller. As the drum rotates, the milk spreads thinly and is simultaneously exposed to hot air, leading to the evaporation of moisture and the formation of dried milk solids.

The roller drying technique imparts distinct attributes to the produced powdered milk. The steady rotation of the drum ensures a uniform and consistent heat exposure, facilitating a controlled drying process. The resulting milk powder exhibits a flaky or sheet-like texture, proving advantageous for recipes that require specific textures. However, when compared to spray drying, roller drying might involve slightly elevated temperatures, potentially resulting in the loss of some heat-sensitive nutrients.

One notable aspect of roller drying is its suitability for specific types of milk-based products. For instance, roller drying is often preferred for the production of instant or quick-dissolving milk powders. The resulting flakes or sheets can be easily broken down into a fine powder that quickly dissolves when reconstituted with water.

FORTIFICATION

The production of powdered milk, while offering practical advantages, carries the potential for unintended consequences. The widely utilized methods of spray and drum drying, while efficient in dehydrating liquid milk, can unfortunately compromise the stability of certain heat-sensitive nutrients. This is where fortification comes in.

Fortification in food refers to the intentional addition of essential nutrients, such as vitamins and minerals, to enhance the nutritional content of a product. This process aims to address nutritional deficiencies, meet specific dietary requirements, and provide consumers with a more comprehensive and healthful food option. In the case of powdered milk, common fortifications include vitamin D, calcium, and vitamin A.

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The fortification process is not arbitrary; it is intricately regulated to meet specific nutritional standards. Regulatory bodies establish guidelines to ensure that fortified powdered milk provides a consistent and reliable source of essential nutrients.

This precision in fortification not only compensates for potential nutrient losses during production but also aligns the powdered milk with established nutritional benchmarks. This reassures consumers of its reliability as a convenient and nutrient-rich alternative to fresh milk. In the US, the quantity of vitamin A and D, if included, must not be less than 2,000 and 400 International Units per quart, respectively.

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Have you ever been curious about the nature of acrylamide and how it develops in the food we regularly consume? Acrylamide is a naturally occurring compound that emerges when specific foods undergo high-temperature cooking methods like frying, baking, or roasting. The concern surrounding acrylamide stems from its potential impact on our health, particularly its association with cancer risk.

The purpose of this blog is to unravel the chemistry behind acrylamide, its formation process, and the consequences it may have on human well-being. Furthermore, we will explore the latest scientific research on the potential health hazards linked to consuming acrylamide.

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By gaining insight into the chemistry and formation of acrylamide, we can better understand its impact on the human body. We will address common questions regarding the effects of acrylamide and explore strategies for reducing its presence in our diets.

WHAT IS ACRYLAMIDE?

Acrylamide forms through a chemical reaction known as the Maillard reaction. This reaction occurs when certain amino acids and sugars in food react at high temperatures, typically above 248°F (120°C).

Acrylamide forms during frying, broiling, baking, and roasting due to the high temperatures involved, which promote the Maillard reaction and acrylamide formation.

These cooking methods also create a dry heat environment that allows for water evaporation and concentration of sugars and amino acids, further facilitating acrylamide formation.

Boiling and steaming, with their lower temperatures and presence of liquid water, are less conducive to acrylamide formation due to the absence of dry heat and the dilution of sugars and amino acids. In facts, conducted studies did not detect acrylamide in unheated and boiled foods.

Acrylamide, when present in high concentrations, is acknowledged as a neurotoxin. Animal studies conducted with acrylamide concentrations thousands of times higher than those typically found in food did not show an increased risk of cancer, although the applicability of these findings to humans remains uncertain. Ongoing research is exploring the potential connection between acrylamide and certain types of cancer, suggesting a possible increased risk. Despite the inclination to minimize acrylamide intake, a preliminary study revealed its presence in 40% of the American diet.

Mitigating acrylamide consumption can present difficulties due to its formation during everyday cooking practices. Nevertheless, there are approaches that can aid in reducing its presence in our diets. These strategies encompass refraining from overcooking or charring foods, selecting cooking techniques that generate lower levels of acrylamide (such as steaming or boiling), and embracing a diverse diet that emphasizes fruits, vegetables, and whole grains.

THE CHEMISTRY BEHIND ACRYLAMIDE FORMATION

Acrylamide formation requires specific compounds to be present in the food during high-temperature cooking. The main compounds involved in the formation of acrylamide are sugars (particularly glucose and fructose) and the amino acid asparagine. Here’s a breakdown of the compounds required for acrylamide formation:

1. Sugars: Sugars are essential for the Maillard reaction, which is responsible for acrylamide formation. During high-temperature cooking, the sugars undergo a series of complex chemical reactions with other compounds, including amino acids, resulting in the browning, aroma, and flavor development in cooked foods.
2. Asparagine: Asparagine is an amino acid naturally present in many foods, particularly those rich in protein, such as potatoes, grains, and coffee beans. When combined with sugars during cooking, asparagine plays a crucial role in the formation of acrylamide. Under high heat conditions, the Maillard reaction occurs between asparagine and reducing sugars, leading to the production of acrylamide.

While sugars and asparagine are key components for acrylamide formation, it’s worth noting that not all foods that contain these compounds will necessarily produce significant amounts of acrylamide.

It’s important to note that the exact mechanisms and interactions involved in acrylamide formation are complex and not yet fully understood. Studies have shown that reducing sugars containing a free aldehyde group can react with asparagine at temperatures exceeding 212°F (100°C), resulting in the formation of an N-glycoside compound. This N-glycoside is subsequently cleaved at the C-N bond, leading to the production of an intermediate that ultimately yields acrylamide. A study conducted in 2003 proposed a pathway illustrating the transformation of N-glycoside into acrylamide. Moreover, it has been observed that substances such as 2-deoxyglucose, glyoxal, and glycerol can also combine with asparagine to synthesize acrylamide.

FOODS COMMONLY ASSOCIATED WITH ACRYLAMIDE

Acrylamide is found in a range of foods that undergo high-temperature cooking processes. Fried potato chips (16-30%), potato crisps (6-46%), coffee (13-39%), pastry and sweet biscuits (10-20%), bread and crisp bread (10-30%) are the main contributors to the dietary exposure of western populations to acrylamide. Other foods contribute less than 10%.

The proportion of each food item in the total intake of acrylamide varies depending on the composition of the food basket in different countries. For instance, in Sweden, coffee contributes 39% to the total exposure while in the Netherlands it is only 13%. In the United States, fried potato products account for 35% of exposure while coffee accounts for only 7%.

Here are the food items commonly associated with acrylamide formation:

Potatoes

When potatoes are cooked at high temperatures, such as frying or roasting, the naturally occurring sugars and the amino acid asparagine present in the potatoes undergo a chemical reaction known as the Maillard reaction. This reaction leads to the formation of acrylamide, resulting in the characteristic golden-brown color and crispy texture of potato products like French fries and potato chips.

Coffee

Acrylamide is naturally formed during the roasting of coffee beans. The high temperatures involved in the roasting process cause the Maillard reaction to occur, resulting in the formation of acrylamide. The amount of acrylamide in coffee is primarily determined by the duration and temperature of the roasting process. On average, coffee contains between 249 and 253 μg of acrylamide. A study indicated that coffee substitutes have the highest level of acrylamide at 818 μg/kg, followed by instant coffee at 358 μg/kg, and then roasted coffee at 179 μg/kg. I have discussed acrylamide in coffee in a separate post.

Baked Goods

Baked goods, such as cookies, crackers, bread, pastries, and cakes, contain ingredients like flour, sugar, and fats, which are prone to acrylamide formation when exposed to high heat during baking. The Maillard reaction between the sugars and amino acids in these ingredients leads to the production of acrylamide, contributing to the desirable texture and flavor of baked goods.

Snack Foods

Snack foods like pretzels, corn chips, and popcorn are often processed at high temperatures, making them susceptible to acrylamide formation. The combination of starches, sugars, and high-temperature cooking methods during snack food production can lead to the formation of acrylamide.

Potato chips, being the most popular among consumers, often exhibit elevated levels of acrylamide in comparison to other snacks. This disparity can be attributed primarily to the naturally higher concentrations of reducing sugars and asparagine amino acid present in potatoes.

In contrast, vegetable chips and tortilla chips generally contain lower amounts of acrylamide when compared to potato chips. This difference is primarily due to variations in their composition and cooking methods. A study revealed that the levels of acrylamide in potato chips ranged from 117 to 2762 parts per billion (ppb), whereas tortilla chips demonstrated acrylamide levels ranging from 130 to 196 ppb.

Breakfast Cereals

Certain breakfast cereals, especially those made from grains like oats or rice, can contain acrylamide. This is because these cereals often undergo processes such as toasting or extrusion at high temperatures, which can trigger the formation of acrylamide through the Maillard reaction.

HEALTH RISKS

The discovery of acrylamide as a neurotoxin and carcinogen in heated foods has raised concerns about its potential health effects. When ingested, acrylamide is metabolized in the body and can form reactive compounds that may bind to DNA and proteins. This can potentially lead to genetic mutations and cellular damage.

Research has indicated that the consumption of foods high in acrylamide is associated with a higher incidence of certain cancers in humans, including ovarian, endometrial, breast, and kidney cancers. This was confirmed in several studies presented. In a 2010 study conducted by Harvard School of Public Health (HSPH), it revealed a heightened risk of ovarian and endometrial cancer in non-smoking post-menopausal women who regularly consume food and beverages with elevated acrylamide levels.

However, our current knowledge about the comprehensive effects of acrylamide on human health is limited. The available evidence primarily stems from studies conducted on laboratory animals rather than direct investigations into human exposure to acrylamide from food sources. Various organizations, including the US Food and Drug Administration (FDA), European Food Safety Authority (EFSA), and the American Cancer Society acknowledge the necessity for further research to fully comprehend the complete impact of acrylamide on human health.

To date, evaluations of epidemiological studies conducted on diverse populations suggest that there is minimal evidence linking dietary acrylamide to the risk of developing most common types of cancer. However, ongoing research endeavors will provide further insights into the potential correlation between acrylamide levels in foods and an increased risk of cancer.

REDUCING ACRYLAMIDE IN YOUR DIET

Although it is challenging to completely eliminate acrylamide from the diet, there are several measures you can take to reduce its intake. Within the United States, the FDA governs the permissible levels of residual acrylamide in materials that come into contact with food. However, there are presently no specific regulations concerning the presence of acrylamide in food products themselves. In 2016, the FDA released guidelines aimed at assisting the food industry in minimizing acrylamide content in select foods. It’s important to note that these guidelines serve as recommendations rather than enforceable regulations.

At home, you can follow simple steps that can effectively lower your consumption of acrylamide:

Avoid Overcooking or Burning Foods

Acrylamide formation is more likely to occur when foods are overcooked or burned. The darker the food is, the more arcylamide has formed. To minimize acrylamide levels, be mindful of cooking times and temperatures. Cook food only until it turned golden yellow or light brown. (See above illustration as provided by the FDA). Avoid excessive browning or charring foods, as this can increase acrylamide formation. Or better yet, opt for cooking methods that retain moisture, such as steaming or boiling, which tend to produce lower levels of acrylamide.

Opt for Cooking Methods with Lower Acrylamide Production

Certain cooking methods are known to generate less acrylamide compared to others. Steaming, boiling, and microwaving are gentler techniques that can help reduce acrylamide formation. When applicable, choose these methods over frying, baking, or roasting at high temperatures.

For instance, when preparing potatoes, steaming or boiling them instead of frying or baking at high temperatures can significantly reduce acrylamide formation. By opting for gentler cooking methods like steaming or boiling, you can mitigate the risk of excessive acrylamide production while still enjoying delicious and nutritious dishes.

Embrace a Varied Diet

You can reduce your acrylamide exposure by include a variety of foods in your diet. Make sure to include plenty of fruits, veggies, and whole grains in your diet. These foods contain lower levels of acrylamide and have several nutritional benefits..

Instead of relying primarily on processed snacks like potato chips or French fries, include a variety of fruits, vegetables, and complete grains in your meals.

Storage and Preparation

Proper storage and preparation methods can also play a role in reducing acrylamide. Store potatoes and other starch-rich foods in a cool, dark place instead of the refrigerator. The asparagine content of potatoes and similar foods is not significantly affected by storage conditions. However, it is known that long-term storage of potatoes below about 39°F (4°C) increases the level of reducing sugars, which potentially increases acrylamide formation during cooking.

Additionally, soaking raw potato slices in water for 15-30 minutes before frying can help remove some of the starch and lower acrylamide levels. Starch is a precursor to acrylamide formation during cooking. By soaking the potatoes in water for 15-30 minutes prior to frying, some of the starch on the surface of the potato slices can be leached out.

The water acts as a medium for drawing out the excess starch, which may contribute to a reduction in acrylamide formation during the cooking process. It is important to note that this technique may not completely eliminate acrylamide, but it can be a helpful step in minimizing its levels. I have discussed this in a separate post further: Why Soaking Potatoes In Water Is Important.

References:

J. Provost, K. Colabroy, B. Kelly, M. Wallert (2016). The Science of Cooking: Understanding the Biology and Chemistry Behind Food and Cooking. John Wiley & Sons, Inc.

N. A. Michael Eskin, F. Shahidi (2013). Biochemistry of Foods (3rd edition). Academic Press.

P. Cheung, B. Mehta (2015). Handbook of Food Chemistry. Springer.

A. Zeb (2019). Food Frying: Chemistry, Biochemistry, and Safety.John Wiley & Sons Ltd.

S. Damodaran, K. Parkin (2017). Fennema’s Food Chemistry (5th edition). CRC Press.

H. Belitz, W. Grosch, P. Schieberle (2009). Food Chemistry (4th Edition). Springer.

J. Velisek (2014). The Chemistry of Food. John Wiley & Sons Ltd.

The post Acrylamide In Food: Chemistry, Formation, And Health Effects appeared first on The Food Untold.

In this piece, we will shed light on the truth about caffeine in black tea, separating reality from misconceptions. We’ll explore the fascinating world of tea chemistry and uncover the exact amount of caffeine present in your daily cup of tea. Whether you’re seeking to optimize your caffeine intake or simply intrigued by the scientific aspects of black tea, this article aims to provide you with comprehensive answers.

So, grab your favorite mug, get comfortable, and get ready to uncover the secrets behind black tea and its caffeine content.

CAFFEINE AND ITS EFFECTS

Caffeine is a naturally-occurring stimulant found in plants like tea leaves, belonging to a group of compounds called xanthines. It acts on the central nervous system, providing a boost in energy and alertness, making tea and coffee popular choices for combating fatigue and starting the day with vigor.

Black tea, derived from the leaves of the Camellia sinensis plant, is renowned for its robust flavor and aromatic qualities. But does black tea contain caffeine? Absolutely. Black tea ranks among the most popular caffeinated beverages globally, alongside coffee and green tea. However, compared to coffee, black tea generally contains a lower amount of caffeine. This makes it a milder choice for individuals who wish to moderate their caffeine intake.

Contrary to common misconceptions, the caffeine in tea is not a byproduct of the fermentation process. Instead, it naturally exists within the tea leaves themselves. Tea leaves typically contain 3.5% of caffeine. Coffee beans, in comparison contain 1.1 to 2.2% caffeine.

CAFFEINE LEVELS IN BLACK TEA

When prepared, the caffeine levels in black tea can vary between 40 to 120 milligrams per 8-ounce (240 ml) cup. This is notably lower than the caffeine content found in a typical cup of coffee, which usually contains around 95 milligrams of caffeine. However, among the types of tea, black tea contains the highest amount of caffeine. In one study, it found that a 200ml serving of black tea contained 63mg of caffeine. In contrast, white tea and green tea of the same volume were found to contain 49mg and 51mg of caffeine, respectively. Generally, the caffeine content is lowest in white tea due to the use of young leaves and buds, minimal oxidation during processing, and shorter steeping times during brewing.

Yes, one of the key factors that influence the caffeine content is the type of tea leaves used. Various varieties such as Assam, Darjeeling, and Ceylon, possess different levels of caffeine. For instance, Assam black tea, known for its bold flavor, tends to have a higher caffeine content compared to other types of black tea. Additionally, the growth conditions and altitude of the tea gardens can also impact the caffeine levels in the leaves.

The processing technique plays a crucial role, with black tea undergoing a more extensive oxidation process, often referred to as fermentation, which contributes to its unique flavor profile. Fully oxidized black teas generally have higher caffeine content compared to partially oxidized teas like Oolong or green tea.

Lastly, the brewing technique can also influence the caffeine content. Steeping the tea for a longer duration or using hotter water can result in a higher extraction of caffeine. Conversely, shorter steeping times and lower water temperatures can produce a milder cup of tea with slightly lower caffeine levels. Nonetheless, the difference in caffeine content resulting from brewing methods is generally insignificant.

FACTORS THAT AFFECT THE CAFFEINE LEVELS IN BLACK TEA

Various factors come into play when it comes to the caffeine levels in black tea. While the type of tea leaves used and the processing methods are key determinants, there are additional factors that contribute to the caffeine content. These factors allow for some customization based on personal preferences.

Firstly, the grade of tea leaves can impact the caffeine levels. Tea leaves are graded based on their quality, size, and shape. Higher-grade teas typically consist of more buds and young leaves, which tend to have higher caffeine content. Conversely, lower-grade teas often contain more mature leaves, which generally have lower caffeine levels.

Secondly, the duration and temperature of the brewing process play a vital role in extracting caffeine. As previously mentioned, longer steeping times and hotter water tend to yield higher caffeine levels in tea. To achieve a more subtle flavor and moderate caffeine content, one can adjust the steeping time or opt for slightly cooler water. Exploring various brewing techniques allows for the discovery of a personalized and optimal brewing approach.

Lastly, water quality also plays a role in caffeine extraction. Hard water, characterized by high mineral content, can hinder the release of caffeine from the tea leaves. Conversely, soft water with lower mineral content tends to enhance caffeine extraction. For those seeking to maximize caffeine content, using soft water or filtered water may prove advantageous.

The post Does Black Tea Really Contain Caffeine? appeared first on The Food Untold.

Milk, a vital and widely consumed beverage, has undergone numerous technological advancements to extend its shelf life while preserving its nutritional value. One such innovation is Ultra High Temperature (UHT) treatment, a process that revolutionizes milk preservation. UHT milk undergoes a rigorous heating process that eliminates harmful microorganisms, ensuring a longer shelf life without the need for refrigeration.

The science behind UHT milk involves a delicate balance of temperature, time, and the understanding of microbial growth. This innovative technology has revolutionized the dairy industry, making it possible to transport and store milk for extended periods without compromising safety or taste.

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This post will explore the scientific aspects of UHT milk and how it differs from conventional pasteurization. We will discuss the key stages involved in UHT treatment, including the heating process and its effects on the nutritional composition of milk. Furthermore, we will examine the microbiological factors, including the elimination of harmful bacteria and the importance of aseptic packaging in preserving the milk’s sterility.

Let’s dive in.

WHAT IS ULTRA HIGH TEMPERATURE (UHT) MILK?

When you visit a supermarket, you may notice two different types of milk storage: refrigerated milk and milk displayed on a shelf at room temperature. The distinction between these two types lies in the treatment they have undergone. Refrigerated milk has typically undergone pasteurization, while the milk on the shelf has been treated with the ultra-high temperature (UHT) method.

Ultra-High Temperature (UHT) milk refers to a type of milk that has undergone an intense thermal treatment process to achieve an extended shelf life without the need for refrigeration. This preservation method involves subjecting the milk to extreme heat of 284°F (140°C) for 4 seconds. This rapid heating is crucial as it ensures the destruction of bacteria, yeast, and molds that may be present in the milk. By eliminating these microorganisms, UHT milk remains safe for consumption over an extended period, even without refrigeration. A properly packaged UHT milk should last 3 to 6 months or longer.

This is the reason why UHT milk can be safely displayed on the shelf at room temperature. Sure, pasteurized milk has also been heat-treated, but the temperature is relatively lower. The temperature for milk pasteurization is 162°F (72°C) for 15 seconds. This does not completely sterilize the milk. Hence, some microorganisms, although significantly reduced in number, may still be present. These remaining microorganisms can multiply and cause spoilage if the milk is not refrigerated.

The advantages of UHT milk are significant. It allows for the distribution and availability of milk in the regions where refrigeration may be limited or unreliable. UHT milk also provides convenience for consumers, as it can be stored at room temperature until opened. An opened UHT milk under refrigeration has a shelf life similar to that of fresh milk, 7 to 10 days.

HOW IT IS MADE

The process begins with the collection of fresh milk from dairy farms. Quality control measures are implemented to assess the milk’s composition, including fat content, protein content, and absence of any abnormalities or contaminants.

The collected milk undergoes pre-treatment to remove any impurities or particles. This involves processes such as clarification, centrifugation, or filtration to ensure a clean milk base for further processing.

The pre-treated milk is then subjected to ultra-high temperatures. In UHT treatment, the milk is heated rapidly at 284°F (140°C) for 4 seconds. This time and temperature combination varies, depending on the manufacturer and brand.

Following the heating process, the milk is rapidly cooled to bring it back to a safe temperature. This step is crucial to halt the heating process and prevent any further undesirable changes in the milk’s composition.

During UHT processing, the sugars in the milk, such as lactose, can undergo caramelization due to the intense heat. This process leads to the formation of new compounds and the development of characteristic flavors and colors associated with caramelization. However, caramelization can contribute to a burnt or slightly cooked flavor, altering the natural sweetness of the milk. The milk may also lose some of its original creaminess or richness, resulting in a slightly thinner consistency.

Once cooled, the UHT milk is filled into sterilized containers through a process known as aseptic packaging.

With aseptic packaging, the packaging materials undergo sterilization to eliminate any microorganisms on their surfaces.

The aseptic carton or Tetra Pak is the most prevalent type of packaging used for aseptic packaging of UHT milk. These cartons have several layers, including a layer of paperboard, an aluminum foil layer, and layers of plastic film. This mix of components creates a barrier against light, oxygen, and bacteria, assuring the milk’s long shelf life and safety.

UHT MILK NUTRITIONAL COMPOSITION

UHT milk retains many of the essential nutrients, including proteins and calcium, found in fresh milk. But here is the thing though.

Although protein is still present in UHT milk, the intense heat during the UHT process denatures the proteins in the milk. Denaturation refers to the structural changes in proteins due to heat exposure. This leads to a loss of their original shape and function. The high temperatures used in UHT treatment can cause denaturation of the milk proteins, altering their structure. Denatured proteins may have reduced bioavailability. So proteins in UHT milk may be less efficiently digested and absorbed by the body compared to those in raw milk.

Furthermore, the heat treatment involved in UHT processing can impact the solubility of specific minerals, such as calcium. While UHT milk provides a similar calcium content as other milk types, the high temperatures used in UHT treatment can cause calcium to become insoluble, leading to the formation of precipitates or clumps. For this reason, the body may encounter challenges in effectively absorbing and utilizing the calcium in UHT milk when compared to raw milk.

In a 2013 study conducted in Korea, the effect of various heat treatments on the solubility of calcium in commercial milk products was investigated. The findings revealed that raw milk exhibited the highest calcium levels, measuring 450.2 mg/kg and 444.2 mg/kg after two rounds of ultrafiltration. In comparison, UHT milk only contained 370.3-380.2 mg/kg and 371.3 mg/kg of calcium after undergoing ultrafiltration.

However, it is important to note that UHT milk still contains significant amounts of calcium. To compensate for potential calcium loss, some UHT milk products may be fortified with additional calcium to ensure an adequate intake of this essential mineral.

MICROBIAL DESTRUCTION AND STERILITY

The key principle behind UHT milk is the concept of thermal processing. This relies on the understanding that microorganisms and enzymes are heat-sensitive. Raw milk may contain pathogenic bacteria such as Listeria, Campylobacteria, Salmonella, Brucella, Cryptosporidium, and E. coli. When milk is exposed to such high temperatures, the heat disrupts the structure of these microorganisms. This renders them inactive and incapable of causing spoilage. Additionally, UHT treatment also inactivates enzymes that can lead to undesirable changes in flavor, texture, and nutritional quality.

After undergoing the Ultra High Temperature treatment, milk has to be packaged in a way that maintains its sterility and prevents recontamination. This is achieved through a process called aseptic packaging.

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Aseptic packaging involves filling the UHT milk into pre-sterilized containers under hygienic conditions. These containers are designed to create a barrier against any microorganisms or external contaminants that could compromise the milk’s safety and quality. Aseptic packaging is crucial in preserving the long shelf life of UHT milk without the need for refrigeration.

The containers used for aseptic packaging are typically made of materials such as cartons, bottles, or pouches. These packaging materials undergo a sterilization process to eliminate any microorganisms present on their surfaces. The sterilization techniques can include heat treatment, chemical sterilization, or a combination of both.

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