食品科技英文雙號作業

 The process of spray drying is primarily comprised by four stages: atomization, spray-air contact, moisture evaporation from spray, and recovery of the dried powder. The atomization may be carried out by an atomizer such as rotating disk, and rotating, two-fluid and high pressure nozzles. A cyclone or other dust collection methods can be utilized for recovery of the dried powder. In order to prevent food ingredients from damage by heat, a non-heat spray dryer has been developed in which the hot air in the drying chamber is replaced by nitrogen gas or by ambient air with very low relative humidity (1~3%).
The unit operation of concentration can be conducted by means of evaporation, freeze concentration, membrane separation, and osmotic dehydration. During evaporation, the solvent, such as water, is eliminated in the vapor form by heating.  This process is commonly practiced at reduced pressure to maintain the quality of foods being concentrated by preventing the constituents of foods from heat damage, especially such heat-susceptible as colorants, flavor components, vitamins and other nutrients.
The main advantages of blanching are as follows :
To prevent enzymatic browning and off-flavors by inactivation of relevant enzymes that are naturally present in the vegetable and fruit.
To drive out gases originally existed in the tissues of vegetable and fruit.
To diminish initial count of microbes.
To fasten some natural colors such as chlorophyll.
In addition to blanching, sulfiting treatment is another main pretreatment for manufacturing dried vegetable and fruit products. It can be conducted by burning sulfur or soaking raw materials in a solution of sulfite. The smoke of sulfur dioxide is formed upon sulfur burning and circulated in a smoking chamber where the vegetable and fruit are subjected to the treatment. Both enzymatic and non-enzymatic brownings can be prevented by this manner.
Low temp preservation can be classified into cold storage, chill storage, and frozen storage. The cold storage and the chill storage are commonly operated in the temperature ranges from 2 to 15℃ and -5 to 2℃, respectively, while the frozen storage is usually operated at -18℃ or even below. The use of chilled brine as a cold dip or spray is commonly applied to chill seafood.
The hydrolyzed vegetable proteins (HVPs) can be chemically produced by adding acid, followed by neutralization with alkali, centrifugation, filtration, drying and polishing.  Preparation of hydrolysate from vegetable proteins can also be achieved through enzyme treatments.