foodscienceandtechnology(ppt60)-電子商務(wù)(存儲(chǔ)版)
【正文】 ur transfer while avoiding humidity buildup and caking of product. ? Proper handling of spices to retain desirable aroma pounds. Cleaning often required for the simple removal of dirt and debris. A. Brushes, highvelocity air, steam, water, vacuum, magic attraction of metal contaminants, mechanical separation, filtration, etc. B. Water treatment: In soft drinks, water should be low in inanic salts, since these minimize carbon dioxide solubility and promote excessive escape of gas bubbles。 can be solidsolid, liquidliquid, solidliquid, gasliquid, etc. B. Many are “kitchenstyle” mixers, just bigger. Most mon used to mix solids into liquids to dissolve them is a propellertype agitator within a stainless steel vat. C. Mixing usually involves the generation of heat and in foods it is often desirable to minimize this temperature rise by some form of cooling. D. Some mixing requires high rpm Example: Mixer/beater found in ice cream freezers to incorporate air into ice cream mix to produce desired volume increase (overrun) required to attain desired texture Heat exchanging A. Reasons to heat: ? Cook ? Pasteurize ? Preservation (., blanching) ? Drive off moisture (evaporate) ? Develop flavors ? Inactivate natural toxic substances (soybean meal) B. Need to control application of heat (often necessary to heat and rapidly cool the product) ? Rapid heating and cooling often require maximum contact of the food with the heating/cooling source (., heat exchangers in the pasteurization of milk). ? Steamjacketed stainless steel kettle or tank often used for heating liquid foods (mixing propeller usually included to prevent scorching and even distribution of temperature). ? Canning using a retort (pressure cooker) ? Roasting circulating hot air C. Cooling ? Again, a heat exchanger can be used, but with cold water pumped through the unit. ? Commercial blast freezers reach 26C ? Liquid nitrogen: 196C Evaporation to concentrate foods 2 to 3fold A. To remove water, to recover desirable food volatiles, and to remove undesirable volatiles. B. Can be solar (raisins), heated kettle (water from a sugar syrup). C. Very mon in the industry: Vacuum evaporation reduced pressure allows liquids to boil at lower temperatures (the lower temperature causes less damage to food quality). Drying to take foods to near total dryness (often 2 to 3% water) Examples ? Dried milk processed by spray drying (atomized liquid mixed with heated air)。 extreme conditions may be used to speed things up. FOOD DETERIORATION AND ITS CONTROL Food deterioration includes declines in anoleptic desirability/aesthetic appeal, nutritional value, and safety (., product quality)。 bananas, lemons, squash and tomatoes are subject to “chill injury” at 10C. D. Moisture and dryness Excessive moisture can lead to undesirable microbial growth. Surface moisture from high relative humidity can cause lumping, caking, browning, crystallization, and stickiness. High moisturebarrier films can trap moisture from respiration and transpiration in fruits amp。 vegetables if allowed to freeze resulting in discoloration, and texture changes。 sense of taste bees dulled. Statistical analysis of results is usually employed. 5. In addition to flavor, taste panels judge texture, color, packaging, sample arrangement, etc. Additional quality factors A. Nutritional quality ? Chemical or instrumental analyses for specific nutrient。 vegetables), but labor costs are high. B. Electronic photocell equipment used to detect and reject offcolor products (., potato chips, peanuts, eggs)。 British patents issues for killing bacteria in food with ionizing radiation (1905). In ., first mercial freezing of fruit and fish. 1910s: In ., first largescale mercial pasta production. 1920s: Clarence Birdseye develops quickfreezing process for foods and first mercializes blanched frozen vegetables. Food fortification begins by fortifying table salt with iodine (1924). 1930s: Freezedrying process invented to preserve food. Vitamin D first added to milk through ultraviolet radiation (1933). 1940s: Mass production of food using automation takes off. Concentrated, frozen, and dehydrated foods produced in mass quantities for shi
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