Yogurt is a popular and extensively consumed dairy product recognized for its numerous health advantages, including probiotics that aid digestion. However, yogurt, like any perishable food item, can reach its expiration date, leaving consumers concerned about the risks of consuming old yogurt.

While we understand your concerns regarding expired food, it’s important to clarify that the “best by” date on yogurt packaging is intended to provide guidance on optimal freshness and quality. It does not necessarily mean that the yogurt becomes immediately toxic or unsafe to consume once the expiration date has passed. It’s worth noting that many food products in the market feature labels such as “Use-By,” “Best if Used By,” or “Sell-By,”. These are related to food quality rather than food safety. These dates indicate the recommended timeframe for consuming the product while it is at its peak quality. If you would like further information on this topic, I have previously addressed it in an earlier blog post, which you can read here.

HOW LONG BEFORE EATING EXPIRED YOGURT BEFORE YOU GET SICK?

Now back to the question. How long after eating expired yogurt before you get sick?

Well, according to FoodSafety.gov, yogurt should be consumed within 1 to 2 weeks from the date of purchase if refrigerated, and 1 to 2 months if frozen. Again the concern here is freshness and quality. When yogurt reaches its expiration date, the manufacturer no longer guarantees its freshness, quality, or taste. Consuming yogurt after its expiration date may provide various health hazards, albeit the severity of these risks varies. And there is no exact timeframe for how long it takes to get sick after eating expired yogurt, as it can vary depending on several factors. But in most cases, eating expired yogurt will cause no harm, provided that the dairy product has been properly stored (unopened and refrigerated or frozen).

As yogurt ages, the probiotics, which are beneficial bacteria, continue to ferment it. If the yogurt has passed its expiration date, you may notice a more pronounced sourness and acidity compared to its usual taste. This increased acidity is due to the production of additional lactic acid during the fermentation process. Although it might appear that the yogurt has gone bad, this is not the case. Expired yogurt, as long as it remains uncontaminated, will not cause any harm. This implies that only the live bacteria cultures intentionally added during the fermentation process are present.

The primary probiotic bacteria commonly found in yogurt cultures are Lactobacillus bulgaricus and Streptococcus thermophilus. These strains are responsible for the fermentation and transformation of milk into yogurt, contributing to its unique flavor and texture. While the taste and acidity of expired yogurt may differ, it can still be safely consumed as long as no external contaminants are present.

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But what if the yogurt has been contaminated with harmful bacteria?

Harmful bacteria called pathogens can contaminate yogurt and cause foodborne diseases in ingested. Symptoms of foodborne infections include minor stomach ache, vomiting, diarrhea, abdominal pain, and fever.

It’s important to note that consuming contaminated yogurt does not automatically guarantee that you will fall ill immediately. The onset and severity of symptoms can be affected by factors such as the level of spoiling and a person’s vulnerability to foodborne pathogens. Young children, persons with weakened immunity, and older people are more susceptible to food poisoning.

KEEPING YOGURT SAFE FOR CONSUMPTION

It’s essential to store yogurt correctly to reduce any possible risks. Make sure to put it in the fridge as soon as you as you purchase it. Yogurt should be appropriately stored at refrigerated temperatures to guarantee the viability of the bacterial cultures. Store yogurt in the refrigerator at or below 40°F (4°C). Keep it tightly sealed to prevent cross-contamination and maintain its freshness. Once opened, consume the yogurt within the recommended timeframe specified on the packaging. Yogurt’s live bacterial count can be reduced by heat, prolonged air exposure, and extended storage times. Hence, yogurt should be used before the expiration date.

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But if you did not consume the yogurt timely, you can observe signs of spoilage. It is best to discard yogurt if there is mold growth, unusual color, off-putting odor, or curdling. Visually inspect yogurt for any visible signs of spoilage even if the yogurt hasn’t reached its expiration date. When in doubt, throw it.

The post How Long After Eating Expired Yogurt Before You Get Sick? appeared first on The Food Untold.

Yogurt is a dairy product made by fermenting and coagulating milk. Our ancestors figured out by accident that fermentation makes bread and beer. Historians believed that yogurt was invented 5000 years ago in Mesopotamia (modern-day Iraq). However, its origin is not singular. In ancient Greece, the Greeks produced oxygala, one form of yogurt. In ancient Egypt, Egyptians learned that fermenting milk is still safe to consume and that it provides similar health benefits to fresh milk. Some historians also claimed that yogurt originated in Turkey. In fact, yogurt got its name from the obsolete Turkish word “yogmak”, which means to thicken”.

Today, yogurt manufacturing is done by cultivating one or more pasteurized dairy products like cream, milk, skim milk, or milk with the fat removed with a bacterial culture. The process is similar to making buttermilk and sour cream. However, the incubation period and the types of bacteria is different.

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Microorganisms in yogurt exist in friendly form (good bacteria), known as probiotic flora. They convert lactose, a sugar found in milk, into lactic acid. The tart, acidic flavor of yogurt is a result of the production of lactic acid. Just like cheese, yogurt depends on the growth of bacteria to produce flavor compounds, ripening enzymes, and acidity. The more bacterial strains, the stronger the acidic flavor. The acid also contributes to the thickening of the milk, giving it a consistency yogurt is known for.

Starter cultures used in making yogurt are lactic acid bacteria (LABs). The lactase enzyme, which is necessary to break down lactose into its component sugars, glucose and galactose, is absent in most bacteria. LABs, however, readily digest lactose and utilize glucose as an energy source.

Here are the common starter cultures used in yogurt.

STREPTOCOCCUS THERMOPHILUS AND LACTOBACILLUS BULGARICUS

The process of making yogurt commercially entails gradually acidifying previously heated milk. The milk must be heated prior to inoculation to kill any competing microbes, often at 85°C to 90°C for 5–20 minutes. This causes the whey proteins to lose their natural properties and permits disulfide exchange events with the cysteine-containing caseins. These processes alter the micellen surface, which improves the coagulum’s acidified textural characteristics.

 

The two most widely used bacteria strains in the United States are Streptococcus thermophilus and Lactobacillus bulgaricus. The Food and Drug Administration (FDA) requires that these two specific LABs must be present in the product to be called yogurt. These LABS co-exist in the milk in a stable associative relationship called photocooperation, wherein there is an exchange of metabolites and/or stimulatory factors.

S. thermophilus grow preferentially in milk because most strains have fewer nutritional requirements. In fact, no growth of Lb. bulgaricus is seen during the initial exponential growth of Thermophilus.

The growth of S. thermophilus (less acid tolerant) slows down in the second phase when the pH of the milk starts to drop, and it provides a variety of growth factors, including formate, pyruvate, folate, CO2, and even some long-chain fatty acids that encourage the growth of Lb. bulgaricus. The latter then releases cytoplasm and cell wall peptidases and proteases, which hydrolyze caseins into peptides and amino acids, respectively.

Since S. thermophilus strains lack extracellular proteases, cocultures with Lb. bulgaricus strains significantly accelerate their growth as they serve as an amino acid source to support a second exponential growth phase for S. thermophilus. In the third growth phase, the growth of Lb. bulgaricus continues.

HOW STARTER CULTURES ARE ADDED

The addition of starter culture happens after pasteurization and homogenization of milk.

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Any competing bacteria are eliminated during the heat treatment, which typically lasts 5–20 minutes at 185°F (85°C) – 194°F (90°C). This heating process enables disulfide exchange events with the cysteine-containing caseins and denatures the whey proteins as well. These reactions modify the micelle surface and contribute to favorable textural characteristics in the coagulum.

After pasteurization is homogenization typically at pressure between 15 and 20 MPa using a single-stage homogenizer. This technique successfully reduces fat globule size, increases fat surface area, and covers the surface with mostly proteins; casein micelles cover approximately 25% of the surface. In addition to evenly blending all the ingredients. Homogenized milk yogurt is firmer, smoother, and more stable (has less wheying and creaming) during storage.

After homogenization, the mixture is cooled to incubation temperature between 104°F (40°C) to 113°F (45°C) and then pumped into fermentation tanks.

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The starter culture (3% w/w of S. thermophilus and Lb. bulgaricus in a 1:1 ratio) is either introduced to the fermentation tanks or is metered directly into the mixture while pumping. However, fermentation can be in retail containers (set-style) or in bulk tanks (stirred). A temperature around 42°C is maintained for 2 to 2.5 hours. During this period, the titratable acidity and/or pH of the yogurt must be checked. Once a pH of 4.6 or titratable acidity of 0.85 to 0.90% is reached, there should be a solid mass of gel that has formed. At this point, the yogurt is cooled to around 41°F (5°C). The product can be stored or further processed to produce other forms of yogurt.

References

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

Experts from Mayo Clinic, University of California, Los Angeles, and Dole Food Company, Inc (2002). Encyclopedia of Foods. Academic Press.

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

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

Starter cultures are essential ingredients in yogurt making.

The post Starter Cultures In Yogurt appeared first on The Food Untold.

Yogurt is one of the best foods ever invented by humans. Like pickles, sauerkraut, kimchi and tempeh, yogurt is super healthy for being one of the best sources for probiotics. Probiotics are live microorganisms that are beneficial to the human body—they give you a healthy digestive tract, strong immune system and much more! This is the very reason why health-conscious individuals always have yogurt in their grocery list every week, at least.

You can easily avail yourself of a cup of yogurt from a nearby store, like most people do.   But you may opt for homemade ones rather than store-bought. And this second option is highly recommended. Why?

Is homemade better than store-bought?

There is no denying that yogurt is super healthy. But as companies move forward, they tend to make sure the consumers have the undying support to their brand. They may make some tweaks to their formulations to appeal to a larger audience. Like for example, some yogurt brands may have more amount of sugar added to adjust the sweetness. Naturally occurring sugar like lactose in milk is okay. But added sugar during processing to adjust the flavor might just be bad for some, especially those at risk of developing diabetes or even cancer.

Artificial coloring is also an issue with commercial yogurt.  Plain yogurt can be boring. So manufacturers add artificial color to better the appearance. But that is just all, nothing else.

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It would be better if they use natural colors, but artificial ones just make food more vibrant. As much as possible, you must avoid using artificial coloring as they generally are unhealthy—they usually cause allergies.

Ideally, yogurt should only consist of milk and active live culture and they are what you’ll only need to make homemade yogurt.

How to make homemade yogurt

What you need:

• 1 liter of whole milk
• About 45 ml Plain yogurt
• 1 liter canning jar
• Saucepan

Choosing live active culture

Hold on, if you’re using whole milk, it’s better to use raw milk. Old whole milk bought from the store may have a high bacteria count, which may affect the yogurt culture entirely.

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There are many brands of yogurt that do not do good in making homemade yogurt. Some do not truly have an active culture. Read the labels if the yogurt you’re getting indicates that it has an active culture. Another thing to take note of is to never pick sweetened or flavored yogurt. There is not much live culture in it to start with.

Process:

• Pour in milk in a saucepan
• Bring to 180°F (82°C) while stirring constantly to prevent scorching.
• Remove saucepan from heat and let it cool to 115°F (46°C)
• Once temperature is reached, put 3 tablespoons or 45 ml of yogurt in the jar
• Slowly put milk into the jar while stirring to blend the yogurt and the milk
• Make sure to wipe the jar rim
• Cover with lid and apply band
• Incubate the jar for 8 hours at 100°F to 113°F (37°C to 45°C)
• Check if the yogurt is already firm. If not, incubate it for another hour
• When the yogurt has already set, chill it for at least 6 hours before serving.

Remember that during incubation, the yogurt needs a warm place (around 100°F to 113°F). Since yogurt is temperature-sensitive, a steady temperature must always be observed. Have a thermometer to ensure the incubation temperature is maintained all throughout. If the temperature is cooler than this, incubation may take longer (up to 12 hours). You can place your jar in an oven if it can maintain the temperature required.

You can store the yogurt in the fridge for 3 weeks.

The post How To Make Homemade Yogurt appeared first on The Food Untold.