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8.1.1: Food Spoilage

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    As discussed previously in the food safety and Foodborne illness sections food can go bad and when food goes bad- people can get sick. Aside from potential illness that can be the result of food spoilage another issue is food waste. Food waste is estimated to be the largest portion of the items found in U.S. landfills and also estimated to somewhere around 40% of all food purchased by U.S. households ends up in the trash.

    Since the beginning of time, humans have tried to extend the life of their food. Ancient Egyptians fermented grains and dried fish, meat has been salted (cured) and stored for long hunting trips, canning made its way into the forefront to help feed troops which eventually gave way to the modern day "meal ready to eat" (MRE) used by modern day troops and even freeze drying foods for NASA astronauts.

    While we may not be NASA astronauts or needing food to fuel us on the battlefield reducing food waste at home is an important idea in ending wastes. For that reason, we will focus more on the food preservation methods that may be taken by everyday people rather than commercialized processes.

    When discussing food spoilage there are three categories of foods based on their perishability. There are foods that will spoil quicker than others.

    Perishable: Will keep for hours or days (e.g. flesh meats, eggs, milk) think about foods that need refrigeration.

    Semi-perishable: will keep for a couple of weeks or months (e.g. processed grains, root vegetables and some fruits) Think items that can be kept out of the freezer or refrigerator and are shelf-stable for a short while.

    Nonperishable: These foods will keep for awhile. Some of which have undergone methods of preservation that will be discussed later. Foods in this category include canned fruits and vegetables, dried fruits, beans, honey, salt and spices, and whole grains.

    Food spoilage can occur in three main ways. There may be biological changes, chemical changes, or due to physical changes with the food. Foods may also be damaged due to pests, bugs, and animals. Some sources cite animal/pest damage in the physical category while others acknowledge it as a category all of its own. For the purposes of this class we will discuss this separately but not a primary cause of food spoilage.

    Physical: Physical changes can occur when food is subjected to varying and sometimes big swings in temperature changes. Think back to when we discussed what happens with ice cream and freezer burn. Ice cream may melt (or become soft) and refrozen but this occurs at a cost. The ice crystals may from on the ice cream which destroys some of the texture and flavor of the product. Other types of physical damage include light exposure (e.g. potatoes or onions allowed to sprout in sunshine) and mechanical damage.

    Chemical: Both enzymatic and non-enzymatic reactions are in this category. Chemical reactions may be caused by proteolytic enzymes. Recall that proteolytic enzymes otherwise known as proteases break down proteins found in foods. Other ways this can occur is through lipases (breaking down of fats) and Oxidizing compounds.

    Biological: Biological food spoilage include many of the things that we spoke about in Foodborne illness section. Microorganisms, yeast, molds, and bacteria. Now keep in mind that some of these things such as yeasts and bacteria may be used strategically in food preservation methods (fermentation!) however, as we have discussed previously- there are good and bad bacteria and some yeast growth will make us sick if not done properly. Other: In this "other" category food may be spoiled if affected by animals, pests, or bugs. Weevils in flour would be an example of this or a wormy apple.

    More information on this topic may be found at the following page: Food Spoilage Resource Citation: %20create%20beer.

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    8.1.1: Food Spoilage is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.