During frying temperature

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... 

Factors which affect heat and mass transfer during frying are the thermal and physical-chemical properties of the food and oil, the food geometry, and the oil temperature. Many variables are involved in the traditional flying process of potatoes ... 

Figure 11.1 Oil uptake versus moisture content during frying of potato slices. Lines connect experimental data corresponding to the same frying temperature. 1 20°C, O 150°C, A 180°C (reprinted with permission from Lebensmittel-Wissenschaft und-Technologie, 2006, 39, 285-291).

TABLE 1. Oil Temperature Profile During Frying French Fries. 

The typical oil temperature profile during frying French fries is shown in Table 1. The frying test was conducted in a countertop twin fryer (Model 5301 A, Star Manufacturing International, Inc., Hobson Lane, Smithville, TN). Each pan had an oil capacity of 15 pounds. The total thermal capacity of the fryer was 45,000 BTUs (11,364 CHUs) per hour (1). 

Depending on the product, the restaurant fryers are operated at 335 to 375°F (168-190.6°C). During slow hours, the fryers are maintained on standby mode to keep the oil temperature relatively low. The oU is always maintained at the frying temperature during rush hours. 

The restaurant owner or manager must review the test data from the company that manufactures the treatment chemicals and make sure that the soap content in the oil after treatment is not higher than before the treatment. The treatment temperature for oil is also critical, especially if the material contains citric acid. Citric acid is a metal chelator and is expected to remove the excess metal ions that are chemically transferred into the fryer oil during frying. Citric acid breaks down if the oil temperature is above 284°F (140°C). Fryer oil, transferred to the filter sump, can be very hot (300°F/149°C). This can break down citric acid at this high temperature and make it ineffective. 

Virgin olive oil shows a remarkable resistance to oxidation and polymerisation during domestic deep-frying of potatoes or in other uses at frying temperatures. Compared to vegetable oils such as sunflower, cottonseed oil, com and soybean oil, olive oil shows a significantly lower rate of alteration as demonstrated by measurements of viscosity, total polar compounds and loss of... 

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