食品科學(xué)和技術(shù)(英文)(文件)
【正文】 Dating system 1. Different code dates: Date of manufacture (pack date), Date the product was displayed (display date), Date by which the product should be sold (sell by date), Last date of maximal quality (use by date), Date beyond which the product is no longer acceptable (use by date or expiration date). 2. Use of these code dates requires a need to predict and monitor shelflife. Models for predicting shelflife are particularly useful for new products without a distribution history. V. Major causes of food deterioration A. Microanisms (bacteria, yeasts and molds) B. Insects and rodents C. Heat and cold can cause deterioration of food if not controlled. D. Moisture and dryness E. Oxygen F. Light G. Time A. Microanisms (bacteria, yeasts and molds) More types of microanisms can spoil food than cause foodborne disease. Sources of these microanisms: soil, water, air, food itself, humans, food equipment environment. Healthy living tissue (internally) is usually sterile, hence the presence of spoilage anisms is mostly the result of contamination. Bacterial endospores are most difficult to inactivate. Heat and moisture will increase growth and activities of microanisms. Molds as pared to bacteria can generally grow at: lower pH (more acid conditions), lower moisture contents (dryer conditions), higher salt concentrations, and lower temperatures (in refrigerated foods). Molds usually only a problem with spoilage, not safety, but Aspergillus flavus and Aspergillus parasiticus produce aflatoxins which are potent hepatocarcinogens. Molds require oxygen for growth. B. Insects and rodents Insects destroy 5 to 10% of . grain crop annually (in other parts of the world it can reach 50%)。 samples are coded so that source or identity of food sample is unknown to taster. Most mon is the triangle test (a preference test): Selecting the sample that differs from two others (total of 3 samples). Usually no more than 5 samples tested at one sitting。 liquid foods are easiest to dry. ? Mashed potatoes and tomato puree processed by drum drying (drum heated from within, applied layer of food flashes off its moisture on contact with heated drum, and thin film of food scraped off drum with long knives). ? Peas and diced onions dried by moving through a long tunnel oven (subject of overheating and shrinkage), but a preferred method is, ? vacuum freezedrying (used for coffee), food frozen, dehydrated under vacuum from the frozen state. Forming foods made into specific shapes (., fish sticks) Application of pressure within an appropriate form. Range of pressures used, varies considerably dependent upon the product. For example: Extrusion {Breakfast cereals Extrusion cooking} Formulated dough or mash is extruded under high pressure with heat. Packaging (food containers) To protect food from microbial contamination, physical dirt, insect invasion, light, moisture pickup or loss, flavor pickup or loss, and physical abuse (damage). Containers include metal cans, glass and plastic bottles, paper and paperboard, plastic and metallic films, and binations of these. Packaging is automated. New processes To increase the range of options within each unit operation, to improve quality or increase efficiency. Examples include: supercritical fluid extraction, ohmic heating, and high hydrostatic pressure processing. QUALITY FACTORS IN FOODS Appearance factors Textural factors Flavor factors Additional quality factors Appearance factors A. Size and shape ? Size: Easily measured (., fruits and vegetables can be sized according to the openings they can pass through。 crystallization of sugar crystals from sugar cane juice) Liquid from a solid (., extracting juice from a fruit。Food Science and Technology By Gilsonl 10/23/2023 Definition Food science: Scientific study of food from “ farm to fork” . Food technology: Use of the information generated by food science to produce safe, nutritious and wholesome food. FOOD SCIENCE Multidisciplinary Engineering Chemistry/Biochemistry Microbiology Nutrition Foods as edible biochemicals Touches on many other areas Globaliza
教學(xué)課件相關(guān)推薦
鄂ICP備17016276號(hào)-1