In a similar way, as water in food freezes, organic molecules are concentrated and expelled. Thus, the iceberg is composed of fresh water, and the surrounding sea water becomes a saltier and denser brine. As the sea water freezes, salt is removed. On a large scale, this happens to icebergs in the ocean. Depending on how rapidly something is frozen, salts can sometimes be concentrated, as pure water freezes at a higher temperature than water with things dissolved in it – like sugars and salts. This phenomenon is called "salt rejection". Many of us would be familiar with "freezer burn" on meats and other foods, as well as ice crystals on frozen food.
There's a suite of chemical processes happening in the freezer, too.įreezing causes physical changes to foods, often enhancing their breakdown. When fermenting a food, we intentionally contaminate it with microbes of known characteristics, or provide conditions that favour the growth of desirable microbes and subsequent production of aromatic compounds.īy contrast, uncontrolled food spoilage is problematic, especially when the contaminating microbes can cause disease.įreezing changes the food It is not only microbial growth that can lead to undesirable odours. They are the pleasant aromas that we sense when we eat, but VOCs can also be produced by bacteria.įor example, many of us would be familiar with the smells that come from fermentation – a microbial process. These are generally referred to as volatile organic compounds (VOCs). Second, the fats and flavours that are part of the food itself can and will be released. First, as microbes start to grow, several pungent chemicals are produced. It's also worth noting that many microbes will survive freezing and start growing again once conditions are favourable – for example, if you remove the food, partially thaw it, and return it to the freezer. This can happen if there is a power outage for more than a few hours, or if you put something hot straight in the freezer.įood spills and open containers provide an opportunity for microbes to get to work. Typically, the culprits are microbes – bacteria, yeasts and moulds.Īlthough a freezer dramatically slows down the growth of most common spoilage microbes, some can still thrive if the temperature rises above -18 degree Celsius (the recommended freezer temperature). Have you ever noticed a funky smell in your freezer? Where does it come from and what can be done to fix the problem? Hardy microbes and pungent chemicals There are several causes for bad smells coming from your freezer. Unfortunately, this is not always the case. Melbourne, May 5 (The Conversation) Most people would expect a freezer can keep perishable food fresh and safe from spoilage for many months.
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