How Good Is the Quality of Low-Temperature Pasteurized Fresh Milk? A Look at the Key Checkpoints in Dairy Pasteurization Methods

Fresh milk pasteurization methods can be simply divided into 2 types: low-temperature pasteurization and high-temperature pasteurization, each with its own supporters. Consumers who support low-temperature pasteurization believe that fresh milk not subjected to high-temperature pasteurization can retain more nutrients, while consumers who support high-temperature pasteurization believe that fresh milk spoils easily and that only high-temperature pasteurization can ensure hygiene and safety. Experts clarify that low-temperature pasteurized fresh milk requires an excellent milk source and must be cared for at every checkpoint to avoid souring. As for the difference in nutritional content compared with high-temperature pasteurized fresh milk, it is only about a 3% difference.

I-Mei Fresh Milk, the fourth-largest dairy company in the country, was recently temporarily removed from Costco shelves after consumers reported that the fresh milk turned sour before its freshness period had passed. I-Mei General Manager Kao Chih-ming issued a statement on the official website saying that the product at Costco uses H.T.S.T. high-temperature short-time pasteurization, with a pasteurization temperature of 84°C ± 5 degrees, to retain more nutrients, but if the product loses temperature control at any stage of purchase and consumption, it can easily sour and clump.

Low-Temperature Pasteurization Puts Raw Milk Quality First: The Lower the Total Bacterial Count, the Better

Chen Ming-ju, a professor in the Department of Animal Science and Technology at National Taiwan University and a domestic dairy processing expert, explained that the H.T.S.T. high-temperature short-time pasteurization method, commonly known as low-temperature pasteurization, is suitable for milk sources of good quality, and the total bacterial count should be as low as possible. The domestic standard for the total bacterial count of raw milk must be below 100,000, but raw milk intended to be made into fresh milk by low-temperature pasteurization must have a total bacterial count as low as 10,000 to 20,000, otherwise there will be concerns, because after low-temperature pasteurization raw milk still has residual bacteria. When packaged into cartons or cans of fresh milk, the bacteria will continue to grow, and once they grow to a certain level, the fresh milk will sour. Therefore, in addition to requiring raw milk of excellent quality, the shelf life should not be set too long, so as to urge consumers to finish drinking it as early as possible.

The only way to achieve an extremely low total bacterial count is through good pasture management. The pasture environment and milking equipment must be clean, and the dairy cows must also be healthy. Once the udder becomes inflamed, the total bacterial count and somatic cell count in the raw milk will soar. How the pasture stores raw milk while waiting for the milk collection truck to pick it up is also very important.

There are now also quite a few dairy farmers who produce and sell their own milk, and a small number of these pastures use low-temperature pasteurization, such as Lao Die Fresh Milk. According to consumers' actual experience, after taking the bag out of refrigerated storage and carrying it home, during the roughly half hour in between, the fresh milk is at ordinary temperature, and after getting home it is put into the refrigerator again; they have never experienced the fresh milk spoiling.

For Fresh Milk, Buying a Small Bottle Is Better Than Buying a Large Bottle: Drink It All Soon After Opening

Another pasteurization method for raw milk is high-temperature pasteurization, namely U.H.T. ultra-high-temperature pasteurization, at a temperature of 125°C to 135°C. This is the pasteurization method commonly used by domestic dairy companies. Chen Ming-ju said that fresh milk made by ultra-high-temperature pasteurization has less strict requirements for raw milk, and the cold chain for transport and the storage conditions are relatively more relaxed; after buying fresh milk, you do not necessarily have to rush straight home to put it in the refrigerator. Taiwan's summer temperatures are on the high side, making it more suitable to use high-temperature pasteurization to produce fresh milk.

The cold chain is an important key to preserving fresh milk. Chen Ming-ju said that from the factory to the store and then to after the consumer buys it and puts it into the home refrigerator, maintaining a low temperature below 7 degrees is key. But if the store's refrigeration unit is an open type, consumers should observe and pay more attention when buying to see whether the temperature fluctuates. After buying, put it into the refrigerator as soon as possible, and set the refrigeration temperature a bit lower, but not to the point of freezing.

If you buy fresh milk at Costco, the store is very large; even if fresh milk is the last thing you pick up, by the time you finish checking out and then walk to the parking lot, it also takes some time. Chen Ming-ju suggests using ice cubes and a cooler bag to keep the fresh milk at a low temperature. If there are few people at home, do not buy large bottles either; it is recommended to buy small bottles with a capacity of less than 1 liter, and drink them up as soon as they are opened. Otherwise, a large bottle of 2 liters or 1 gallon of fresh milk takes too long to drink and will only increase the risk of spoilage.

2 Pasteurization Methods: The Difference in Fresh Milk's Nutritional Content Is Not Obvious

As for the difference in nutritional content, Chen Ming-ju said that after the 2 pasteurization methods, there is no obvious difference in the nutritional content of fresh milk. The main nutrients in fresh milk are protein and calcium, and these will not be destroyed by U.H.T.; only vitamin A, D, and the B group will oxidize due to high temperature, but these vitamins are not considered the main nutrients of fresh milk.