Foods develop bacterial growth when moisture, warm temperatures, high pH levels, and oxygen from the air provide conditions for growth.
Food rich in protein, sugar and nutrients helps bacteria to thrive. Foods that do not support bacterial growth have a low pH level, no protein, and nutrients that help bacteria grow.
Foods that do not support bacterial growth are raw fruits and vegetables, frozen meats, frozen poultry, frozen seafood, and frozen produce. Other foods included in this group are dry foods, canned foods, dry spices, and acidic foods.
Salt, sugar, vinegar, and alcohol have properties that produce high acidity and antibacterial properties that stop bacteria from growing. Controlling food contamination and illness from bacteria prevents food borne illness.
What is Bacterial Growth?
When bacteria develop in food, water and moisture must be present. Water in food connects to the food molecules. Foods cooked with water will promote the growth of bacteria.
Food high in nutrients, sugar, and protein gives bacteria what it needs to grow. Leaving food out on the counter, table, or outdoors at temperatures of 40 to 140 degrees promotes the growth of bacteria. Oxygen from the air or in refrigerators often causes spoilage.
The pH scale measures the acidity and alkalinity of food. Food with low pH levels do not promote bacterial growth. Foods preserved in vinegar, salt, and acidic solutions do not develop bacterial growth due to high acid levels.
Bacteria need time to grow, and a cell can divide into two cells under the right conditions in 20-30 minutes. Once you have eaten, the food digested continues to produce bacteria and toxins in the body.
When looking for signs of bacterial growth on food, look for mold, slime, an unpleasant smell, strange taste, foam, cans that swell, and brown or black spots on produce. When food has these signs of spoilage, discard it.
Foods That Do Not Promote Bacterial Growth
Raw Fruits and Vegetables
Raw fruits and vegetables do not have the moisture that cooked food does. Some types of fruits and vegetables only last a few days and need to be used quickly.
Refrigerate them and keep them away from humid and warm temperatures.
Vegetables with less moisture, like carrots, potatoes, onions, garlic, ginger, squash, do not spoil, and can be kept longer. Refrigerate fruits and eat within a week to prevent bacterial growth.
Berries, peaches, and melons will grow bacteria or mold when left too long in the refrigerator.
Frozen fruit and vegetables do not develop bacteria because the cold temperatures in the freezer prevent moisture and air from getting in.
Once defrosted, fruit and vegetables should be eaten, refrigerated, or cooked. Canned fruits and vegetables last several months due to lack of air and the sterilization process. Fruits and vegetables preserved in salt or sugar solutions last several months.
Frozen Meats, Poultry and Seafood and Salted and Cured Meats
Freezing beef, pork, lamb, chicken, turkey, and seafood in the freezer keeps temperatures cold, and moisture and air from creating bacteria.
When you buy these foods, it is important to freeze what you do not plan to use immediately. Preserved and smoked meats like sausage, salami, pepperoni, and ham are preserved to prevent bacterial growth.
They should be refrigerated or kept in a cool dry place.
Dry Foods Grains, Rice, and Flour
Pasta does not promote bacterial growth when it is dry. Pasta made from white flour, whole wheat flour, and other grains stays well in dry cool areas.
White, brown, or other types of rice can be stored in plastic or glass containers. White, whole-wheat flour and gluten free flour, if stored properly, do not grow bacteria.
Store dry items, including dry milk and eggs, in airtight containers or in the refrigerator after opening. After cooking grains, store them in containers with lids in the refrigerator.
Nuts, Seeds, and Beans
Nuts, seeds, and dry beans lack moisture and do not promote bacterial growth. They store well in covered containers in the pantry for several months.
Cooked beans should be refrigerated or frozen to keep them safe for eating. Nuts and seeds often have salt or sugar added as an ingredient that preserves food. These are all reasons they do not promote bacterial growth.
Dry Herbs and Spices
Dried spices refer to the seeds, bark, fruit, or roots of the plant. Herbs refer to the plant’s stems, leaves, or flowers.
Dried herbs and spices have no moisture or air because they are packaged in plastic containers or glass with lids. Spices and herbs last many years when stored properly.
Pickles, peppers, and other vegetables preserved in solutions with vinegar, acid, or salt do not develop bacteria. The acid stops bacteria from growing and so do salt solutions.
Storing these foods in an airtight glass jar prevents moisture and air from promoting the growth of bacteria. They can be stored for several months safely.
How long can food last before it supports bacterial growth?
It depends on the type of food it is, how it is packed and stored. Storing food in the refrigerator, freezer, or a dry, cool place prevents bacterial growth.
Food packaged in airtight containers will last longer. Frozen and refrigerated food will last longer than food stored at room temperature.
What are ways to keep food from growing bacteria?
Storing food in the refrigerator or freezer will keep it from growing bacteria. Washing food before cooking it and cooking at the right temperature keeps bacteria from growing.
Store food in containers after cooking with lids in the refrigerator. When food has signs of bacterial growth, it is important to throw it away and sterilize the container.