Since the late s, the vast majority of commercially produced milk is pasteurized. The pasteurization process kills many of the most harmful strains of bacteria known to cause foodborne illness , including E. Over time, these small bacterial communities can multiply and eventually cause your milk to spoil.
When milk begins to spoil, it develops an unpleasant, rancid odor. The scent is hard to miss and gets stronger with time.
The taste also begins to change, as the natural sweetness of fresh milk is quickly replaced by a somewhat acidic or sour flavor. With enough time, the texture and color of milk that has spoiled will change as well. It may begin to develop a slimy, chunky texture and dingy, yellow color.
The rate at which milk spoils depends on many factors, including the number of spoilage bacteria present, temperature at which the milk has been stored, and light exposure 1. Milk spoils due to an overgrowth of bacteria that compromises its quality. You know your milk is spoiled if it has an unpleasant odor or taste or changes texture. The terms spoiled and sour are often used interchangeably to describe milk that has gone bad, but there may be a subtle difference between the two — depending on who you ask.
Spoiled milk usually refers to pasteurized milk that smells and tastes off due to the growth of bacteria that survived the pasteurization process. On the other hand, sour milk often refers specifically to unpasteurized, raw milk that has begun to naturally ferment.
Much like spoiled milk, the fermentation of raw milk occurs due to various species of lactic-acid-forming bacteria, a small percentage of which are considered probiotics and may offer minor health benefits 3. Pasteurized milk is raw milk that has been heated to a specified temperature and time to kill pathogens that may be found in the raw milk. Pathogens are microorganism such as bacteria that make us sick. Raw milk can contain pathogens such as Campylobacter, E.
Raw milk includes milk from cows, goats, sheep and other dairy animals. By law, all milk sold to the public must be pasteurized and packaged in a licensed dairy plant.
Only vitamins A and D may be added to the milk, no other additives or preservatives can be legally added to milk. Vitamin A improves eyesight, helps you to see better at night or in dim light, and helps you to tell colours apart. Vitamin D helps your body absorb calcium and reduces the risk of osteoporosis. According to a US Centre for Disease Control and Prevention study, the rate of outbreaks caused by unpasteurized milk and products made from it was times greater than outbreaks linked to pasteurized milk.
Children and younger adults were found to be more affected by the illnesses. Raw milk may contain pathogens that can cause disease or illness. Some people say they grew up drinking raw milk and never became sick from it. However, public health authorities know of many cases of people who became sick from drinking raw milk. Mandatory pasteurization of milk has eliminated large outbreaks of milk borne disease in Canada.
Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. Key concepts Chemistry Food Science Proteins Enzymes Introduction Have you ever poured yourself a cup of milk and instead of a smooth liquid, all you get is clumps? Only use about one fifth of the pineapple. Cut the flesh in smaller pieces and grate it. Alternatively, you can use a juicer or blender. When it starts to boil, carefully take it out of the microwave and let it cool down.
Take a fresh lemon and use the lemon squeezer to make lemon juice. Once it starts boiling, carefully take it out and let it cool down. It should contain one tablespoon of milk. How does the milk look? What happens if you gently swirl the milk in the cup? Do you notice anything unusual? Use a clean teaspoon to add one teaspoon of the freshly squeezed lemon juice to your milk in cup 1. Swirl the cup slightly. Does the milk change when you add the lemon juice?
If yes, does the change occur immediately or after awhile? When you swirl the cup a little bit, what do you observe at the wall of the cup?
Take your second cup of milk and this time add one teaspoon of the heated lemon juice. Do you see the same reaction happening as before? How does the milk change? Is the reaction as fast as the previous one? Use your third cup of milk, and with a clean teaspoon add one teaspoon of pineapple juice to the milk.
Observe what is happening for about five minutes. Does the milk curdle with pineapple juice? Is the reaction fast or slow compared with that of the lemon juice? To the fourth cup of milk add a teaspoon of heated pineapple juice and swirl the cup slightly. Again, observe the cup for about five minutes. Do you get a similar result again or is it different?
In bad milk, the pair taste awful. If the now steadily spoiling milk is not discovered and thrown out, yeasts and molds can then begin to multiply in the acid environment, and finally Bacilli begin to feed on the milk proteins, further boosting the pH and spewing out smelly ammonia-containing by-products.
Milk, by this point, has gone from merely bad to worse. And if you drink it, it can make you sick. The result was the Milkmaid , a streamlined quart bottle sitting on a metal base the Smartbase containing an array of pH and temperature sensors. Based on information from the sensors, a microcontroller in the base slowly changes an LED from reassuring green to alarming orange, as the milk segues from good to gicky.
Apparently nobody wanted to worry about changing the milk-bottle battery. All rights reserved. Because bad milk is … really bad. Share Tweet Email. Why it's so hard to treat pain in infants. This wild African cat has adapted to life in a big city. Animals Wild Cities This wild African cat has adapted to life in a big city Caracals have learned to hunt around the urban edges of Cape Town, though the predator faces many threats, such as getting hit by cars.
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