Got Milk? The Impact of Temperature Malfunctions to Prevent Spoiled Food

Even if you’ve never had spoiled milk (and we hope you haven’t), you probably have a good idea of just how unpleasant the experience is thanks to popular media. Milk spoils very easily,  turning everyone’s favorite milkshake treat dangerous thanks for foodborne illness. Preventing spoiled food with temperature monitoring in the food industry is crucial, but to what extent?

Prevent Food from Spoiling During the Farm-to-Table Journey

The supply chain of milk is a sensitive one. While it normally begins on a farm, this product makes many stops before becoming the milk you see on your shelves. Trucks transport the milk to a dairy processor where it’s tested for temperatures and certain bacteria. If the milk passes, it will be pasteurized, homogenized, packaged, and shipped to retail stores.

During this process, there are numerous instances where the milk may be exposed to temperature excursions, especially during distribution. Throughout the process, it should be kept in a temperature-controlled environment. There should be temperature monitoring within the shipping container as well as the truck itself. If the temperature isn’t constantly monitored, there are ways to install refrigerator malfunction alerts so milk isn’t exposed to unsafe temperatures—negatively impacting the milk’s freshness.

But there are possibilities for milk to spoil in plenty of stages beyond distribution. In a retail environment alone, this product can be compromised due to missed expiration dates, power outages, fridge failure, doors being left open, or a spacing issue within the unit. To test out these potential situations, we conducted an experiment to show what happens when milk is exposed to unsafe temperatures, even for a small amount of time.

Our Milk pH Experiment to Prevent Spoiled Food

We began this experiment on July 17, 2017, and concluded on July 20, 2017. For our experiment, we used six quart-sized containers of milk. We divided them into two sets of three levels of refrigeration: a control milk, a one-hour milk, and a four-hour milk. The control stayed in the fridge throughout the experiment, simulating a quart of milk that is kept consistently in a temperature-controlled environment and was only removed from the fridge to be measured. The one-hour and four-hour quarts of milk were left outside the fridge for one and four hours, respectively, every other day.

The purpose of this was to simulate temperature excursion events, such as cooling system failure during transportation or power outage in a store.  Throughout our experiment, we recorded the milk’s pH and temperature. The pH was the primary indicator of whether the milk was spoiled. The milk was considered spoiled when it reached a pH below 6.

The Benefits of Refrigerator Monitoring on Milk

The graph above shows the average ph of each set of milk throughout three days. You can see that the pH of all the milk decreased over the course of the experiment. However, the four-hour milk decreased in pH faster than the other milks, meaning that it became more acidic and spoiled more quickly. The one-hour and control milk varied by 0.1 pH after the first day, while the milk left out for four hours varied from the control by 0.3 pH or more.

Milk is typically at a pH between 6.7 and 6.5 and shows extreme qualitative signs of spoils when it reaches below a pH of 6. It’s pretty alarming that the four-hour milk dropped to that pH value in only two days. This means that even with short time periods of exposure to out-of-range temperatures, the freshness of the milk is negatively impacted—and fast.

If the temperature is impacted by power outage during transport or there’s a loss of power overnight, products like milk are put at risk for spoiling. Without continuous monitoring in place, you may not be aware of power loss or temperature excursions—which means you may potentially sell spoiled milk, or other products, to consumers.

Table 1, “The Qualitative Signs of Spoilage,” shows the qualitative signs of spoilage when the milk was disposed of on July 20.

Table 1: The Qualitative Signs of Spoilage

When the milk was disposed of, the four-hour milk showed extreme signs of spoilage that were not as clear or noticeable in the one-hour and control milk.

While the results of this experiment are nothing new, the speed at which the milk spoiled was astonishing. One hour exposed to room temperature can cause the milk to lose a day of freshness, even though the milk then spent 23 hours inside a cold fridge. This means that exposing milk to out-of-range temperatures, even for short periods of time, can greatly impact its freshness. Whether it’s in transit or during power outages in retail, exposing milk to unsafe temperatures can put your consumers at risk. It’s also important to note that the milk’s pH didn’t increase once the milk was returned to the refrigerated environment, showing that there is no way to revert to the “fresh” state of milk.

How to Protect Your Food Inventory from Spoiling

Temperature monitoring is extremely important for the transportation and storage of milk from the dairy farm to the store. Any possible interruption in the cold chain, such as a cooling system malfunction or power outage, will severely impact the freshness of the milk—and, potentially, the health of the consumer.

The most obvious signs of spoilage are qualitative: smell, look, taste. Unfortunately, these aren’t plausible options for store retailers to test if they suspect milk has been exposed to a temperature excursion. With continuous monitoring, a retailer can use real-time, continuous data to determine if the milk was exposed to a temperature excursion and potentially at the point of spoilage.

Food spoilage has consequences both physically and financially, and everyone is affected—from  those consuming the spoiled foods to those selling the spoiled foods. You can prevent foodborne illnesses from spoiled food, which can lead to damage to the company that sold the product. Did we mention brand image is also at risk here? These consequences are easily avoidable with continuous temperature monitoring throughout the cold chain.     

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