Thermooxidative decomposition of Indian mustard oil

摘要

Like other edible oils, the Indian mustard oil is also susceptible to oxidation when exposed to UV rays (photo oxidation), enzymes (enzymatic oxidation) or air/oxygen (auto oxidation). The chemical change that takes place, involves formation of free fatty acid, aldehydes, ketones and polymeric compounds which affect the flavour and the nutritive value of the fried food and stability of oils. While being used for frying during food preparation, many changes (oxidation, isomerisation, polymerisation, hydrolysis etc.) may occur in cooking oil besides formation of volatile and non volatile compounds which in turn influence the fried food quality and its nutritional parameters. Knowing the oxidative stability of Indian mustard oil (rapeseed oil) is important and ths has been measured by TG- DSC technique. The data obtained at four different heating rates of 5°, 10° and 20℃ min~(-1) under N_2 /O_2 purging. There has been marked changes in the pattern when the heating is done after doping with turmeric powder. Like the T_(on) and T_p values and also, the area under the peak which increase with the heating rate, there is also marked accompanying broadening of the peak. T_f was very high for slow heating rate, slow decrease in ?T were observed with increase in the heating rate. The data have been used (applying the Kissinger and OFW methods) for approximation of the kinetic parameters (E, A ). These along with the values of the onset and peak temperatures (T_(on) and T_p) can be used for suggesting optimum temperatures for safe cooking in air involving mustard oil.