Which of the following foods does not support bacteria growth?
- Raw carrots
- Cooked vegetables
- Liquid milk
- Canned milk
Answer: Raw carrots doe not support bacteria growth as the condition of raw food is not suitable for bacteria to grow whereas; cooked food has high water activity and favorable temperature for bacteria growth.Raw foods have a longer shelf-life than any other cooked foods
Bacteria, just like every other living organism, requires food for growth, so food is a medium for which bacteria can grow. However, there are favorable conditions in which bacteria can grow. The conditions which are factors for bacterial growth are as follows: Water/moisture, Temperature, pH, oxygen, and nutrients.
Bacteria can grow in food only when the food condition provides a favorable environment for their survival and multiplication. Some foods don’t support bacteria growth because these food conditions are not favorable for bacteria to multiply.
Furthermore, it is necessary to understand bacterial growth and why bacteria can grow on certain foods in the first place.
In essence, Bacterial growth is the multiplication of bacteria colonies, a process of splitting/fission of bacteria cells by a process known as binary fission. Pathogenic bacteria are harmful when they increase and grow in food; there are some useful bacteria present in our body known as Normal body flora, which helps defend the body against pathogenic ones. Pathogenic bacteria can gain entry into the body when food contaminated with bacteria is eaten.
To fully know foods that don’t support the growth of bacteria among varieties of food that exist, a technique is to know what makes some foods suitable for bacteria growth.
- Water Availability/Moisture content
A requirement for the growth of bacteria is water needed to break down consumed food nutrients. The water activity of a food is a condition that determines the growth of bacteria infood. Water activity is the water not bound to food molecules. Moisture content is the original water composition of the food itself, while water activity is the water content that is unbound to the food molecules—for instance, raw rice grains and cooked rice. The water activity of cooked rice is higher than that of raw rice since water has been added for it to cook, increasing the water activity.
Foods with higher water activity are more likely to support bacteria growth, while foods with little water activity are not ideal for bacteria growth. Cooked rice would support bacteria growth, unlike raw rice.
- Nutrients/Energy source
Bacteria require nutrients as an energy source for growth. Foods contain essential macro-nutrients in the form of carbohydrates, proteins, sugar and starch. Foods rich in nutrients like raw dairy and milk products are easily susceptible to bacteria growth.
Temperature suitable for bacteria to grow rapidly is between 40-140℉ known as Temperature Danger Zone. Food in this temperature would most likely support the growth of bacteria. A major food preservative measure is freezing because bacteria can’t grow or multiply to cause spoilage; frozen foods don’t support bacteria growth.
Air and oxygen are required for bacteria to grow. However, some bacteria can grow in conditions without oxygen. Foods in condition without air does not support bacteria growth. Canned foods are made to be completely free of air from the environment, so bacteria can’t even gain access to the food for growth. As long as canned foods are not dented or have openings, it can not support the growth of bacteria or any microorganisms since it has been made sterile.
pH is the measure of alkalinity or acidity on a scale ranging from 0(highly acidic) to 14(highly alkaline). Bacteria grow best at a neutral pH of 7, while foods that have pH below 4.5 do not easily support bacteria growth. Bacteria grows easily in foods that are neutral to slightly acidic; foods that are highly acidic, like lemons and vinegar, won’t support bacteria growth.
These factors and conditions are what determines if any kind of food will support bacteria growth.
Foods that are not suitable for bacteria growth:
Raw Vegetables and Fruits
Raw vegetables, as well as raw fruits, do not facilitate bacteria growth. As earlier stated, raw foods contains little water activity, unlike cooked foods whose water activity has been increased by cooking. Such raw foods like raw carrots, raw onions, raw garlic, ginger, potatoes and other raw foods do not support bacteria growth. Raw foods have a longer shelf-life than any other cooked foods. The condition of raw food is not suitable for bacteria to grow whereas; cooked food has high water activity and favorable temperature for bacteria growth.
Dry food doesn’t provide moist condition for bacteria reproduction and growth so they don’t support bacteria growth. Examples of such foods include food in powdered or granular form;
Rice grains, Wheat flour, grains, Nuts, Pecans, dried dairy products like powdered milk, egg powder. Dry foods lack moisture therefore they don’t support condition for bacteria growth.
Freezing kills bacteria making frozen foods free from bacteria growth and reproduction. Freezing subject foods to a low temperature which bacteria can’t survive. As a result, any frozen food won’t support bacteria growth. Once beef, meat, or any food is stored in the freezer, it renders all bacterial activities inactive, so any frozen foods won’t support bacteria growth.
The absence of air in canned foods does not aid any growth of bacteria, but once opened or dented, it can cause bacterial contamination. Canned foods have a long shelf-life due to the sterilized condition from the outside environment with sealed containers made from metal, glass, or aluminum. Foods such as canned milk, canned peas, canned tomato paste, or any foods stored in can do not support bacteria growth.
Dried spices stored in dry clean containers never gets contaminated because it does not support bacteria growth. Spices contain low protein and nutrients required for bacteria to grow. Many dry spices like clove, Oregano, thyme, cinnamon have antibacterial conditions against food spoilage bacteria and won’t facilitate their growth.
Foods that have low pH levels and highly acidic by the addition of acids are acidified foods. Any food product that contains a combination/addition of vinegar or other acids doesn’t support bacteria growth—foods like pickles, sauces, tomatoes, peppers, tropical fruits.
The following foods support the growth of bacteria in diverse forms.
- Cooked meat, beef
- Cooked grains or legumes
- Cooked vegetables
- Raw dairy milk, eggs, cheese, and other products
Bacteria growth in food is mostly the cause of food spoilage. Although bacteria cannot be seen without microscope aid, food spoilage can be determined by the change in smell, appearance, texture, or taste.
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