Fermented foods are foods that have been preserved through fermentation, the process of using bacteria to create lactic acid in food products. Fermentation is key to the pickling process as well as to culturing milk to make dairy products, such as yogurt. Fermentation is also used to create alcoholic beverages. Lowering the pH levels of fermented foods is important, because it ensures that they will be safe to consume. A low pH corresponds to a high degree of acidity, which creates an antimicrobial effect. If fermented foods are not sufficiently acidic, they can be unsafe to consume.
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What Is Fermentation?
Fermentation is the process of converting sugar into an alcohol or acid. Fermentation is used to change juice into wine, grains into beer, dough into bread and cucumbers into pickles. Yeast is used to ferment wine, beer and breads, while lactic acid is used in pickling and yogurt making. Fermentation is one of the oldest methods of food preservation.
pH is important to the process of fermentation. The measure of acidity present in food is its pH level. Foods with a pH reading above 7 are alkaline, while foods with a pH reading below 7 are acidic. The more acidic the food, the more resistant it is to microbial growth. Therefore, foods with a low pH level ferment more safely than higher-pH foods, which may be vulnerable to contamination.
Foods with a pH below 4.7 are very bacteria resistant. Thus, foods with a low pH are easy to sterilize. Fermentation lowers the pH of foods by increasing the level of lactic acid present in them, which makes them safe for consumption. Vinegars or other weak acids (such as lemon juice) are sometimes added during the process of fermentation to make sure that the food's pH is kept at safe levels. This process is known as pickling.
Bacteria grow best at pH values of roughly 7.0. Besides citrus and some berries, most foods do not naturally possess low pH levels. Insufficiently low pH levels can cause fermented foods to become infected with botulism. Eating botulism-contaminated foods can lead to potentially fatal illnesses.
Types of Fermented Foods
Types of fermented foods include bean-based dishes, such as tofu or soy sauce; dairy-based fermented foods, such as yogurt, cheese and kefir; fish-based fermented foods, such as fish sauce; fruit-based fermented foods, such as vinegar, wine and cider; grain-based fermented foods, such as beer, sourdough bread or vodka; meat-based fermented foods, such as sausage, pepperoni and salami; and vegetable-based fermented foods, such as sauerkraut and pickles.
Fermentation was first used in the Middle East to create alcoholic beverages. Estimates place the invention of fermentation for these purposes as far back as 7000 BCE. Fermented foods were developed several thousand years later in China and the Middle East. Bread making first originated in Egypt, and pickling first started in China. Fermented foods remain popular today.