Food processing heating

Food processing—Heat and chemicals used during processing can affect amino acid availability. For example, loss of available lysine can occur from mild heat treatment in the... 

Food processing firms producing heat-preserved, frozen, dehydrated, or chemically preserved foods may be classified by their finished products. Companies may be further grouped based on whether they process raw materials into ingredients, such as in poultry and meat processing plants, or whether they take these ingredients and convert them to ready-to-eat consumer products. 

Vacuum Treatment. Milk can be exposed to a vacuum to remove low boiling substances, eg, onions, garlic, and some silage, which may impart off-flavors to the milk, particularly the fat portion. A three-stage vacuum unit, known as a vacreator, produces pressures of 17, 51—68, and 88—95 kPa (127, 381—508, and 660—711 mm Hg). A continuous vacuum unit in the HTST system may consist of one or two chambers and be heated by Hve steam, with an equivalent release of water by evaporation, or flash steam to carry off the volatiles. If Hve steam is used, it must be cuUnary steam which is produced by heating potable water with an indirect heat exchanger. Dry saturated steam is desired for food processing operations. 

Fig. 8. Combustion turbines with process heat recovery (a) represents direct use of exhaust gas for process heating where industrial process includes refinery, chemicals, food processing, and ethanol production and (b) exhaust-to-water heat exchanger where industrial process includes material drying,...

Acid cleaners based on sulfamic acid are used in a large variety of appHcations, eg, air-conditioning systems marine equipment, including salt water stills wells (water, oil, and gas) household equipment, eg, copper-ware, steam irons, humidifiers, dishwashers, toilet bowls, and brick and other masonry tartar removal of false teeth (50) dairy equipment, eg, pasteurizers, evaporators, preheaters, and storage tanks industrial boilers, condensers, heat exchangers, and preheaters food-processing equipment brewery equipment (see Beer) sugar evaporators and paper-mill equipment (see also Evaporation Metal surface treati nts Pulp). 

Saccharin is acidic and not very soluble in water. For improved solubiUty, the food industry prefers the sodium or calcium [6485-34-3] salt. Sodium saccharin [128-44-9] is so widely used that it is often referred to simply as saccharin. The aqueous solubiUties of both salts are about the same, ie, 0.67 g/mL. Saccharin, stable to heat over a wide pH range, can withstand most food processing (qv) conditions. Interactions between saccharin and other food ingredients have not been reported. 

Another development features a nonmetallic belt [Pla.st. Des. Process., 13 (July 1968)]. When rapid heat transfer is the objective, a glass-fiber, Teflon-coated construction in a thickness as httle as 0.08 mm (0.003 in) is selected for use. No performance data are available, but presumably the thin belt permits rapid heat transfer while taking advantage of the nonsticking property of Teflon. Another development [Food Process. Mark., 69 (March 1969)] is extending the capa-bihty of belt solidification by providing use of subzero temperatures. 

Kneading Devices These are closely related to the agitated pan but differ as being primarily mixing devices with heat transfer a secondary consideration. Heat transfer is provided by jacketed construction of the main body and is effected by a coolant, hot water, or steam. These devices are applicable for the compounding of divided solids by mechanical rather than chemical action. Apphcation is largely in the pharmaceutical and food-processing industries. For a more complete description, illustrations, performance, and power requirements, refer to Sec. 19. 

As predicted by the Arrhenius equation (Sec. 4), a plot of microbial death rate versus the reciprocal or the temperature is usually linear with a slope that is a measure of the susceptibility of microorganisms to heat. Correlations other than the Arrhenius equation are used, particularly in the food processing industry. A common temperature relationship of the thermal resistance is decimal reduction time (DRT), defined as the time required to reduce the microbial population by one-tenth. Over short temperature internals (e.g., 5.5°C) DRT is useful, but extrapolation over a wide temperature internal gives serious errors. 

The system shown is heavily used in food processing applications such as milk or chocolate crumb production, sugar substitutes, modified starch, and alginates. In addition to food processing applications, such a system is used in the processing of heat-sensitive pharmaceuticals, polymer suspensions like latex, in processing pigments and dyestuffs, and pesticides. 

---