Dependence on humectants heat transfer co efficient and kinetics of moisture removal in deep fried products

Abstract

newline Addition of various humectants viz., sorbitol, mannitol and glycerol newlinesignificantly altered the deep-fat-frying characteristics of the doughnuts in different newlinefrying media and the time taken for frying of doughnuts, the moisture contents, fat newlineabsorption, specific heat and thermal diffusivity of the doughnuts was markedly newlineaffected and reduced when compared with control samples. On the contrary the oil newlineuptake ratio, thermal conductivity and heat~transfer co-efficients were increased with newlineaddition of different humectants On a whole, addition of humectants shortened the newlineprocessing time thereby decreasing the duration of exposure to higher temperature newlineduring frying, moisture loss and fat absorption. Addition of humectant also called for newlinelonger shelf-life of the doughnuts after packing in craft paper, plastic jars and newlinepolyethylene bags. The control samples (without humectants) and those containing newlineSO per cent sorbitollmannitol had shelf-life below 30 days while, those containing 40 newlineand 50 per cent level of the above humectants remained well upto one and half newlinemonth of storage. Whereas, the samples containing various levels of glycerol newlineremained well upto three months of storage. The protein, fat, and ash contents newlinedeceased during storage for 30, 60 and 90 days while, moisture, free fatty acids and newlineperoxide values increased during storage. Regarding the acceptability of the newlinedoughnuts, the scores for colour, texture, appearance, flavour, taste and overall newlineacceptability were higher in fresh doughnuts with lower levels of humectants and, newlinethese decreased with storage.