Unit Food Science

Problem Area Processing Animal Products

Lesson Salt as a Food Preservative

Student Learning Objectives 1. Describe the uses of salt as a food preservative and explain why salt is an effective food preservative. 2. Discuss the relationship between moisture content in meat products and microbial activity.

Terms Aerobic Bacteria Condensation Dehydration Food spoilage Mold Plasmolysis Proteolytic enzyme Spores Terminal treatment Yeast

What are the uses of salt as a food preservative and why is salt an effective food preservative? A. Chemical preservatives, such as salt, are used when terminal treatment (thermal processing, freezing, drying, fermentation, or refrigeration) is not a suitable preservation method. Chemical preservatives are also used to reduce the intensity (amount needed) of a terminal treatment.

B. Salt enhances flavor and improves keeping quality. Salt inhibits microbial growth by causing dehydration, removal of water from a molecule by the action of heat or a dehydrating agent. Most microbes and bacteria require moisture to survive. Salt also preserves food by: 1. Reducing water available to microorganisms. 2. Increasing osmotic pressure created in the aqueous environment surrounding the microbial cell. The increase in osmotic pressure causes plasmolysis, a partial dehydration where the protoplast of a cell shrinks away from the wall following water loss due to exposure of a solution of higher osmotic pressure. 3. Reducing the solubility of oxygen in water. 4. Sensitizing cells to carbon dioxide. 5. Interfering with the action of proteolytic enzymes, enzymes that catalyze the breakdown of proteins into simpler substances.

What is the relationship between moisture content in meat products and microbial activity? Moisture content in meat products has a direct relationship to microbial activity. A. Food deterioration is a broad term that includes reduction in nutritional safety or aesthetic appeal. Food spoilage is the deterioration of a food product due to microorganisms, enzymes, environment (heat and cold), light and other radiation, oxygen, moisture (or lack of it), industrial contaminants, macroorganisms, and time.

B. Microorganisms such as bacteria, yeast, and molds, that are on or in food products are frequently a major cause of food spoilage. Bacteria are microscopic, relatively simple microorganisms that have a primitive nucleus. Yeast is a collective name for those fungi which possess a vegetative body (thallus) consisting of simple individual cells. Mold is any type of various wooly fungus growths. Microorganisms are found in the soil, water, air, and on the exterior of nearly everything that is not sterilized. Microorganisms are usually not found within living tissue.

C. Bacterial spores, an asexual, reproductive body that is resistant to unfavorable environ-mental conditions and produces a new vegetative individual when the environment is favorable, are far more resistant to adverse conditions and most processing methods than mold or yeast spores. Sterilization methods are aimed at these highly resistant bacterial spores. D. When food is contaminated, several types of microorganisms are present together to produce acid, gas, putrification, or discoloration. Putrid odors are produced when microorganisms digest proteins.

E. Bacteria, yeasts, and molds prefer warm, moist conditions. Some bacteria and all molds require oxygen for growth and survival, a condition known as aerobic. Most food- associated bacteria multiply best at temperatures between 16 and 38 degrees C. The slightest amount of condensation, liquid forming from a vapor, on the surface of food can become a hot spot for the rapid multiplication of bacteria or growth of mold. Moisture trapped in packaging containers supports the growth of microorganisms.

Review/Summary What are the uses of salt as a food preservative and why is salt an effective food preservative? What is the relationship between moisture content in meat products and microbial activity?