Food Preservation PDF

Understanding Food Amy Brown Chapter 7: Food Preservation Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Food Spoilage Biological Changes Yeast: A fungus (a plant that lacks chlorophyll) that is able to ferment sugars and that is used for producing food products such as b...

Understanding Food Amy Brown Chapter 7: Food Preservation Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Food Spoilage Biological Changes Yeast: A fungus (a plant that lacks chlorophyll) that is able to ferment sugars and that is used for producing food products such as bread and alcohol. Fermentation: The conversion of carbohydrates to carbon dioxide and alcohol by yeast or bacteria. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Food Spoilage Chemical Changes Chemical reactions or changes also contribute to food deterioration. Enzymes play a significant role in catalyzing these reactions and can be categorized by the substance on which they act (substrate) or their mode of action. An example: – Proteases, also called proteolytic enzymes, split proteins into smaller compounds. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Food Spoilage Physical Changes The most common physical changes occurring in foods as they spoil are evaporation, drip loss, and separation. Dehydrate: To remove at least 95% of the water from foods by the use of high temperatures. Freeze-dry: To remove water from food when it is in a frozen state, usually under a vacuum. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Food Preservation Methods Drying is the food preservation process that consists of removing the food’s water, which effectively inhibits the growth of microorganisms. Like: – Sun Drying Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Food Preservation Methods Commercial Drying The most important types of commercial drying are: – Conventional: heat. – Vacuum: pulls the water out. – Osmotic: water drawn out by osmosis. – Freeze-drying: ice crystals vaporize. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Food Preservation Methods Sublimation: The process in which a solid changes directly to a vapor without passing through the liquid phase. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Food Preservation Methods Cure: To preserve food through the use of salt and drying. Sugar, spices, or nitrates may also be added. Fermentation Pickling uses vinegar to preserve foods. Edible coating: Thin layer of edible material such as natural wax, oil, petroleum-based wax, etc. that serves as a barrier to gas and moisture. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Food Preservation Methods Carbohydrates are required for the fermentation process. Throughout Asia, vegetables are still commonly fermented. In North America, foods most often preserved by fermentation are cucumbers, olives, and cabbage. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Food Preservation Methods The purpose of edible coatings is fourfold: 1. To increase shelf life by acting as a barrier to moisture, oxygen, carbon dioxide, volatile aromas, and other compounds whose loss would lead to deterioration. 2. To impart improved handling characteristics, such as the ability to bend more easily without breaking. 3. To improve appearance through increased gloss and color. 4. To serve as a vehicle for added ingredients such as flavors, antioxidants, antimicrobials, etc. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Food Preservation Methods Canning is a two-step process: – First the food is prepared by being packed into containers, which are then sealed. – Then the containers are “canned,” or heated to ensure that all microorganisms are destroyed. Sterilization: The elimination of all microorganisms through extended boiling/heating to temperatures much higher than boiling or through the use of certain chemicals. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Cold Preservation Refrigeration slows down the biological, chemical, and physical reactions that shorten the shelf life of food. For safety purposes, refrigerators should be kept between just above freezing to no more than 40°F (4°C). All perishable foods should be refrigerated as soon as possible, preferably during transport, to prevent bacteria from multiplying. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Cold Preservation Freezing makes water unavailable to microorganisms. The chemical and physical reactions leading to deterioration are slowed by freezing. Rancid: The breakdown of the polyunsaturated fatty acids in fats that results in disagreeable odors and flavors. Freezer burn: White or grayish patches on frozen food caused by water evaporating into the package’s air spaces. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Heat Preservation Pasteurization: A food preservation process that heats liquids to 160°F (71°C) for 15 seconds, or 143°F (62°C) for 30 minutes, in order to kill bacteria, yeasts, and molds. Ohmic heating: A food reservation process in which an electrical current is passed through food, generating enough heat to destroy microorganisms. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Other Preservation Methods Irradiation: A food preservation process in which foods are treated with low doses of gamma rays, xrays, or electrons. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Other Preservation Methods How is irradation is used: Sterilization of medical equipment (instruments, surgical gloves, alcohol wipes, sutures, etc.) Sterilization of consumer products (adhesive bandages, contact lens cleaning solutions, cosmetics, etc.) Foods for immune-compromised hospital patients (e.g., AIDS, cancer, or transplant patients) Some foods for astronauts, who cannot risk foodborne illness Spices and seasonings used in products such as sausage and certain baked goods Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Other Preservation Methods Pulsed Light exposes the food to intense, very brief flashes of light, which disrupt the cell membranes of bacterial cells, but not that of the surrounding food. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Other Preservation Methods High-pressure processing of foods inactivates foodborne microorganisms at low temperatures without the use of chemical preservatives. Pascalization: A food preservation process utilizing ultrahigh pressures to inhibit the chemical processes of food deterioration. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Other Preservation Methods Ozonation Ozone (an oxidizing agent) is commercially produced by exposing oxygen to an electrical current. Ozone is an effective disinfectant and sanitizer for many food products. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning Other Preservation Methods Aseptic and modifiedatmosphere packaging (MAP) – Hermetically sealed: Foods that have been packaged airtight by a commercial sealing process. Slide Development: Lonnie M. Lowery, Ph.D. Copyright 2003 Thomson Learning