Spoiled milk? Not anymore

Tired of throwing spoiled milk down the sink? Scientists from Cornell University have just  found a way to help you avoid doing that. They have done so by modeling when precisely milk goes bad and how to prevent this. The discovery is expected to help drastically reduce food waste and emissions from the highly carbon-intensive dairy industry.

In a paper published in The Journal of Dairy Science the researchers focus on the spore-forming bacteria that can survive the pasteurization process. Researcher found that while germinating and multiplying inside the liquid, the bacteria create a sour taste and bad smell, which signals us that the milk has gone bad.

To create the model they identified 14 subtypes of the spore-forming bacteria, characterized by how well they germinated and spread at a fridge temperature of 6°C and studied their growth curves under different regimes. Surprisingly, the team witnessed that small temperature changes play a critical role in the growth of bacteria: cooling the milk creates unfavorable conditions for its growth, thereby extending milk’s useful lifespan.

Using simulation experiments, researchers found that milk stored at just slightly lower temperatures had drastically longer lifespans, compared to milk stored in a regularly fridge. Stored at 6°C, around 66% of milk went bad within 21 days. Just by decreasing the temperature to 4°C, scientists were able to reduce that spoilage rate to an impressive 9% within the same period, while increasing the milk’s overall lifespan to one month. Other methods, like micro-filtration, can also reduce the initial spore load and thus increase milk’s useful lifespan.

The immediate value of the model is quite obvious, yet its long-term potential may prove invaluable for managing the lifespans of other foods, and not just dairy products. This might one day provide producers and consumers with unprecedented levels of control over the food stored in their fridges. 

It is expected that a tool based on the model may not only prove beneficial to consumer wallets but also decrease the amount of wasted milk, considering that 20% of dairy products are discarded worldwide annually. It will now be worthwhile to explore how increased emissions from decreasing temperatures in freezers across the industry and households might be countered by emission reductions from food waste saved from the bins. The research also curiously resonates with other arguments for freezing food, as occasionally a more sustainable option compared to fresh.

Scientific discoveries rarely get immediate traction and no doubt for some time yet many people will continue to rely on  subjective sniff-tests or looks at the date on packages. The researchers suggest, though, that one day we might find out the exact spoilage day of milk just by scanning the bar-code in the store.