Although deep-fat frying is a common unit operation that is extensively used for food preparation in both household and commercial cooking, in recent year, the existing of health conscious about the high consumption of fat from fried food is extremely concerned. So that the researches in the reduction of oil absorption in fried food have been widely conducted. As a result, by using a state diagram of food, there was a noticeable progress for understanding concerning to the mechanism of oil uptake on deep-fat frying process. It was found that the development of porosity inside food matrix due to water vaporization influences on oil absorption in frying and post-frying process. From study using wheat flour-water mixture model food with varying initial moisture content, it can be said that the oil absorption in the sample containing the initial moisture content less than 60% was governs by the capillary action in frying process, while that in the sample containing initial moisture content more than 60% was governs by vapor condensation pressure due to cooling in post-frying period. And also, it was revealed that the effect of initial moisture content on the alteration of surface roughness of fried sample, subsequently affects on oil absorption in post-frying process.

View full abstract

It is well known that frying oil gradually deteriorates when used many times, and that the flavor of such rancid oil is bad. The quality of foods fried in such oil is reduced and it becomes toxic as oxidation progresses. In order to access the deterioration of frying oil, we measure the viscosity, acidic value, carbonyl value and etc. But these chemical or physical values cannot be measured easily, and we have no instruments for this in the kitchen. To assess the life span of good taste results for frying oil used for cooking, members of the research group on frying have been looking into an easy method of sensory evaluation, namely, flavor scores based upon the provisional standard methods for the analysis of fats, oils and related materials (Japan Oil Chemists' Society). As the color of the frying oil and the taste of the fried materials varies case by case, it has been revealed that using the judging flavor score 3 of frying oil is a useful and easy method for accessing its life span in the domestic kitchen.

View full abstract