Can a milkshake go bad in the fridge?

In this brief article, we are going to answer the question “Can a milkshake go bad in the fridge?” and discuss the risks of eating bad milkshakes as well as the shelf life of milkshakes in the fridge.

As dairy containing sugar and other ingredients, milk shakes are very perishable and susceptible to microbial spoilage. Regardless of its flavor, milk shakes can go bad in the fridge.

Can a milkshake go bad in the fridge?

Yes, a milkshake can go bad in the fridge. Although it stays fresh in the fridge for a few days, it still has a short shelf life.

The exact shelf life of the milkshake will depend on several factors, including the preparation methods, the ingredients used and the storage conditions.

Milk shake is a sweet, cold beverage which is usually made from milk, ice cream, or iced milk and may include fruits and other flavorings, such as chocolate syrup and alcoholic beverages (1,2).

The exact shelf life of milkshakes in the fridge can be only estimated, as it depends on several factors. These factors are being discussed in the following sections of this article.

What determines how fast milkshakes go bad in the fridge?

The main factors that determine how long fast milkshakes go bad in the fridge are (1,2,3,5): 

• The quality of the ingredients: milk shakes can be produced with the addition of many different ingredients. Each ingredient can carry different microorganisms, which may affect the shelf life of the milkshake
• The initial microbial load of the milk: the spoilage of milk is caused in most of the cases, by bacteria. With a higher initial population of bacteria in the milk, it will spoil faster. By using a previously-stored milk to produce the milk shake, its shelf life will be reduced
• The type of milk used to produce the milkshake: Milk can be processed through pasteurization, sterilization or ultra high temperature sterilization. Each of these thermal treatments have different effects on extending the shelf life of the milkshake. Through sterilization, the microbial load of the milk is lower than when milk is pasteurized. This can affect the shelf life of the milkshake
• The property of the ingredients used: Milkshakes produced using fruits and vegetables can have increased shelf lifes, as these ingredients contain antioxidants which can extend the shelf life of the milkshake. Similarly, stabilizers such as carrageenan and other hydrocolloids may extend the shelf life of milk products
• The thermal history of the milk shake: the shelf life of the milkshake can be extended when thermally treated. In a study, the shelf life of an untreated milkshake was 18 days in the fridge, while the thermally treated milkshake had a shelf life of over 50 days  

How to know if the milkshake has gone bad?

To know if the milkshake has gone bad, you should be able to identify the possible signs of spoilage in the milkshake.

The possible signs of spoilage related to milkshakes are similar to the ones related to the spoilage of milk, as milkshakes can be contaminated with the same microorganisms (1).

The typical signs of spoilage in milkshake are (2,3,8):

• Off-odors such as sour, fruity, bitter, rancid, yeasty, acetone-like are used to describe spoiled milk or spoiled milk products 
• Changes in the texture,such as limpidity, turbidity, coagulation, gelation, increased viscosity and syneresis due to the increase of acidity, reduction of the pH and consequently precipitation of the milk proteins
• The alteration of flavor is also a possible sign. Spoiled milk can have off-flavor such as sour, bitter, soapy or rancid
• Formation of a biofilm on the surface of the milkshake
• Occurring of phase-separation 

What are the risks of consuming a bad milkshake?

The risks of consuming a bad milkshake are of experiencing a foodborne illness. 

Pathogens such as Salmonella ssp., Enterococcus spp. Staphylococcus aureus, Streptococcus agalactiae, Listeria monocytogenes, Yersinia enterocolitica, and Escherichia coli O157:H7 and coliforms are possible bacteria that grow in milkshakes and are able to cause negative effects on health (1,2). 

 L. monocytogenes has been reported to cause several episodes of food outbreaks involving the consumption of ice cream and milkshakes (3).

Gastrointestinal symptoms, such as diarrhea, abdominal cramping, and other symptoms, such as fever, vomiting and headache are some of the possible symptoms experienced in a foodborne disease (4).

Is It Possible to Freeze and Thaw a Milkshake?

Yes, it is possible to freeze milkshakes (7). Similarly to milk, you can freeze milkshake in a food container or in ice cube trays. The shelf life of frozen milkshakes can be only estimated, because it depends on several factors. The estimated shelf life is 3 months (6).

A milkshake may be frozen and thawed, and it’s the ideal storage option if you want to retain its consistency. Remove the milkshake only when you’re ready to consume it and use cold thawing procedures to guarantee it defrosts safely.

The milkshake should be kept away from the freezer door and in an airtight container before being put into the freezer, as well as away from the door itself.

An airtight container prevents other items in your freezer from contaminating or ruining your milkshake’s flavor. Alternatively, you may preserve your milkshake with plastic wrap or a bag.

The simplest method for cold thawing a milkshake is to transfer it from the freezer to the refrigerator. Allow it to remain in the refrigerator for around 20-30 minutes, or until you’re pleased with the defrosted drink’s consistency.

Conclusion

In this brief article, we answered the question “Can a milkshake go bad in the fridge?” and discussed the risks of eating bad milkshakes as well as the shelf life of milkshakes in the fridge.

References

1. El-Gendi, M.A.R.W.A., Marium Mansy. Microbiological Risks Of Milk Shake Sold In Assiut City Restaurants. Assiut Veter Med J, 2017,63, 67-74.
2. Velázquez-Ordoñez, Valente, et al. Microbial contamination in milk quality and health risk of the consumers of raw milk and dairy products. Nutrition in Health and disease-our challenges Now and Forthcoming time. 2019.
3. González-Tejedor, Gerardo A., et al. Quality changes and shelf-life prediction of a fresh fruit and vegetable purple smoothie. Food bioprocess technol, 2017, 10, 1892-1904.  
4. Castillejo, Noelia, et al. Red fresh vegetables smoothies with extended shelf life as an innovative source of health-promoting compounds. J food sci technol, 2016, 53, 1475-1486. 
5. Pouillot, Régis, et al. Infectious dose of Listeria monocytogenes in outbreak linked to ice cream, United States, 2015. Emerg infect dis, 2016, 22, 2113. 
6. Maddox, M. Freezing milk and dairy products. University of Florida.
7. Freezing and food safety. United States Department of Agriculture. 
8. Strohman, Deena Ruthanne. Flavor changes in stored extended shelf-life flavored milks. Diss. University of Minnesota, 2014.