How long can opened yogurt last in the fridge? (Shelf life)

In this brief guide, we are going to answer the question “How long can opened yogurt last in the fridge” with an in-depth analysis of the shelf life of opened yogurt. Moreover, we are going to discuss tips for properly storing yogurt.

How long can opened yogurt last in the fridge?

Yogurt typically maintains its quality for approximately one to two weeks when stored in the refrigerator at a temperature of around 40 ºF. Alternatively, it can be stored in the freezer at 0 ºF for one to two months. However, if yogurt is exposed to suboptimal manufacturing practices or unfavorable storage conditions, it may spoil more rapidly.

It’s worth noting that yogurt having a pH level above 4.3 can provide an environment conducive to the growth of pathogenic microorganisms. Importantly, these microorganisms might be present in the yogurt even before you open the package.

Moreover, opening the yogurt package typically doesn’t lead to significant changes in the intrinsic or extrinsic factors of the product, such as pH, water activity (aw), or atmospheric conditions. Consequently, the growth rate of pathogenic bacteria’s vegetative cells in opened yogurt may not differ significantly from that in an unopened package. (1, 2)

What factors affect yogurt shelf life?

Several factors can impact yogurt shelf life. Spoilage agents like yeast and molds can contaminate fresh yogurt products through various avenues, such as during processing. This contamination can occur from added fruit preparations, packaging materials, or filling operations.

Additionally, compromised packaging, like faulty seals, can provide an entry point for spoilage organisms into the yogurt. The equipment used for filling yogurt varies, ranging from open fillers without specific precautions against contamination to ultraclean fillers that operate in a controlled atmosphere.

Furthermore, packaging materials undergo decontamination treatments, which may include exposure to UVC light, infrared light, or sterilization using H2O2 vapor or steam. Fruit preparations, commonly added to yogurt, also have the potential to introduce yeasts and molds into the yogurt products.

The technology used for the production and incorporation of fruit preparations into yogurt can vary, ranging from simple to highly sophisticated systems. In cases where standard procedures cannot ensure contamination-free operations, some fruit preparations may incorporate preservatives, like sorbic acid, where regulatory guidelines permit their use (3)

What is yogurt shelf life?

Yogurt typically remained fresh in the refrigerator for approximately 20 days while retaining its desired qualities. However, recent efforts within the industry have aimed to extend this shelf life to around 35 days.

During this prolonged period, specific changes occur in the yogurt: the bacterial count decreases, acidity levels rise, syneresis (liquid separation) may happen, and occasionally, unwanted flavors may develop. In the literature, various combinations of time and temperature during the yogurt production process have been explored to achieve this extended shelf life.

One approach involves subjecting the milk to a heat treatment at approximately 75°C and then utilizing aseptic packaging, which can preserve the product for up to 2 months when stored at 5°C. Alternatively, using Ultra High Temperature (UHT) treatment for the yogurt product ensures its stability for several months, even when stored at room temperature. (4)

How does yogurt spoil?

Spoilage can occur due to the activities of yeasts that can withstand acidic conditions, occasionally accompanied by molds. Yeasts are commonly present in various environments and may contribute to gas formation and “doming” in fruit yogurt containers.

The natural sugars found in fruits provide ample substrates for fermentation, whereas in plain yogurt, lactose is the primary sugar source. Because only a limited number of yeasts can ferment lactose, certain lactose-utilizing species can thrive on surfaces that haven’t been adequately cleaned.

In warmer regions where accelerated spoilage is expected, the product’s sell-by date is often limited to 4-5 days after production, as opposed to the typical 2-3 weeks. Alternatively, if regulations permit, sorbic acid is added as a preservative, which has proven to be highly effective against yeasts. (5)

How to spot bad yogurt?

Yogurt spoilage becomes evident through changes in its physical, chemical, and sensory properties, making it unfit for consumption. The main contributors to the spoilage of dairy products such as yogurt and cheese are typically the proliferation of yeasts and molds. (6)

The growth of fungi can induce unwanted flavors and modifications in its visual characteristics. Yeast-induced spoilage in yogurt, coupled with the accumulation of CO2, can lead to expansion and, ultimately, even expulsion of the contents from the container. (7)

Prolonged storage at temperatures above 5°C can cause excessive acidity due to continuous starter activity. Bacteria tolerant to high acidity can produce lactic acid, elevating levels to 1.7% or higher, depending on the strain. These levels often surpass the taste preferences of most consumers. (5)

Will spoiled yogurt make you sick?

Consuming yogurt that has gone bad can lead to food poisoning, characterized by symptoms like nausea, vomiting, stomach discomfort, and diarrhea. While numerous microorganisms can play a role in yogurt and dairy product spoilage, a specific set of bacteria can potentially cause severe illness in consumers.

Normally, these symptoms should show noticeable improvement or completely subside within three days. Nevertheless, if the symptoms persist and the condition worsens, it is advisable to promptly seek medical assistance from your healthcare provider. (8, 9)

Conclusion

In this brief guide, we answered the question “How long can opened yogurt last in the fridge” with an in-depth analysis of the shelf life of opened yogurt. Moreover, we discussed tips for properly storing yogurt.

References