A Study on Heat and Mass Transfer During Deep-Fat Frying

• Main Authors: Yang,Jing-Iong, 楊景雍
• Other Authors: Lee,Yeun-Chung
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/66818552948248611863

碩士 === 國立臺灣大學 === 農業機械工程學系 === 84 === The significant changes of phase transformation of liquid water to vapor and evaporation of moisture of moisture result in primary weight loss during deep-fat frying. During the procedure of deep-fat frying, the characteristics of heat transfer in fried foods is similar to freezing operation. In a manner analogous to freezing operation, the phase of frying may be viewed as the growth of a dried layer, comparable to the growth of an ice layer in freezing. The interface between the dried region (crust) and the undried region (core) in frying operation is at the boiling point of water, comparable to the freezing point in freezing operation. In both cases, the interface is a moving boundary. By measuring the temperature alterbation, the conductive type of heat transfer in the core region of fried foods and the event of moving boundary are found. During deep-fat frying, the temperature of fried products rises gradually. In the meanwhile, the role of mass transfer develops more and more significantly, but the freezing model can not meet the occurrence of moisture loss during deep- fat frying. In this study, the moisture loss during deep-fat frying related to the square root of frying time is found. Likewise, drying, another type of dehydration, shows a similar outcome. In view of the mentioned above , the established drying models can provide a foundation for deep-fat frying research. Because the complex mechanism, higher cost and limitation of general consumers' acceptance, few researchers have studied on vacuum (reduced pressure) deep-fat frying. Since the special texture and taste of the fried products are produced by this operation, the heat and mass transfer in foodstuffs during vacuum frying are investigated in this study. According to the results, compared with deep-fat frying under atmospheric pressure, the heat and mass transfer in foodstuffs under vacuum indicates a quite different outcome.