During frying

Skim milk was initially used as the aqueous phase in margarine. Where the law allows, margarines may contain caseinates, whey proteins, or soy proteins as the proteins component in the aqueous phase. The addition to margarine of 0.01—0.1 wt % sodium caseinate in place of milk has been proposed to eliminate sticking during frying. Substituting soy proteins for milk would have the same effect. 

The mechanism of NPYR formation has been studied by Coleman (37) and Bharucha et al. ( ). Coleman (37) reported that the requirement for a high temperature, the inhibitory effects of water and antioxidants, and the catalytic effect of a lipid hydroperoxide are consistent with the involvement of a free radical in the formation of NPYR. Similarly, Bharucha et al. (29) suggested that, since both NPYR and NDMA increase substantially towards the end of the frying process, N-nitros-amine formation during frying of bacon occurs essentially, if not entirely, in the fat phase after the bulk of the water is removed and therefore by a radical rather than an ionic mechanism. These authors speculated that, during the frying of... 

The inhibition of formation of NPYR and NDMA in fried bacon by the use of cure-solubilized a-tocopherol (500 mg/kg) has been demonstrated by Fiddler et al. (50). Walters et al. (53) also reported reduced levels of N-nitrosamines in the vapors during the frying of bacon in fat containing a-tocopherol. It has also been shown that a-tocopherol is dispersed quite effectively during frying of bacon slices therefore, application to bacon may be made by spray or dip to overcome the problem of water insolubility (51). Controlled addition of this antioxidant may be an effective and practical way of reducing the concentration of N-nitrosamines in cooked... 

Oleomargarine, another commercially important emulsion, presents problems with its behavior during frying. 

Vapors horn cooking. About 90% of NDMA and 75% of NPYR formed in cooked bacon is lost through evaporation during frying (44,45). It has been calculated that the airborne nitrosamine levels in a typical kitchen could be as high as 56 ng/m3 of NDMA and 560 ng/m3 of NPYR (16). However, the exposure would be of short duration (<1 hr.) and the total nitrosamine intake would be small. 

Mass transfer during frying is not only characterized by the movement of water in the form of vapor from the food into the oil, but also by the movement of oil into the food. Frying is a dehydration process where water escape leaves empty spaces within the crust structure, which in turn determines the volume available for oil absorption. In fact, the amount of oil uptake has been shown to be directly proportional to... 

There has been much research to examine the different factors affecting oil absorption during frying and many empirical studies have correlated oil absorption measurements with process and/or product characteristics. According to the oil absorption mechanisms explained in the previous section, some factors that may be relevant to the amount of oil absorbed will be now presented. 

Gamble, M. H., Rice, P., and Selman, J. D. (1987). Relationship between oil uptake and moisture loss during frying of potato slices from c.v. Record U.K. tubers. Int. J. Food Sci. Technol. 22, 233-241. 

Kochhar, S. P. (1999). Safety and reliability during frying operations Effects of detrimental components and fryer design features. In "Frying of Food" (D. Boskou and I. Elmadfa, eds.), pp. 253-269. Technomic Publishing Inc., Lancaster. 

Moyano, P. and Berna, A. (2002). Modeling water loss during frying of potato strips Effect of solute impregnation. Drying Technol. 20(7), 1303-1318. 

Pokorny, J. (1980). Effect of substrates on changes of ftas and oils during frying. La Rivista Italiana delle Sostanze Grasse. 57, 222-225. 

Sahin, S., Sastry, S. K., and Bayindirli, S. K. (1999). Heat transfer during frying of potato slices. Lebensmittel-Wissenschaft Technologic. 32,19-24. 

Taiwo, K. A., Baik, O. -D., Farinu, A. O. (2007). Kinetics of heat and mass transfer and color development of pre-treated sweet potatoes during frying. Trans. ASABE, 50, 129-135. 

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