Challa Ravi Kiran; Dr Sundresan, A(Cochin University of Science and Technology, June , 2015)
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Abstract:
Deep fat frying process is one of the widely followed cooking practices throughout the
world. Cooking oils serve as a medium for frying food for transferring heat and makes fried
food tasty and palatable. Frying process is a most complex process involving numerous
physicochemical changes which are complicated to understand. Frying leads to thermal
degradation of oil through thermo-oxidation, hydrolysis, and polymerization. Hydrolysis
results in formation of free fatty acids whereas oxidation process produces hydroperoxides
and small molecular carbonyl compounds. This whole process leads to the formation of polar
compounds and degradation of antioxidants that further degrades frying oil. Eventually,
through mass transfer process these degradation products accumulate into fried food and
reduce the nutritional quality of both oil and food. Thus, the frying process is of research
interest calls for detailed systematic study which is chosen for the present study. The primary
objective of this study is to understand the mechanism of degradation and characterization ofdegraded products which helps in arriving at the limits for frying oil utilization in terms of
number of frying cycles. The mechanistic studies and the knowledge on the degraded
products help to understand the way to retard the deterioration of oil for stability and
enhancement of frying cycles. The study also explores the formation of the predominant
polar compounds and their structural elucidation through mass spectrometry. Oxidation of oil
is another important factor that ignites the degradation phenomena. One of the best ways to
increase thermal stability of any oil is addition of potent antioxidants. But, most of the natural
and synthetic antioxidants are unstable and ineffective at frying temperatures. Therefore, it is
necessary to screen alternative antioxidants for their activity in the refined oils which are devoid of any added antioxidants. In this context, this study discussed the efficacy of several
natural and synthetic antioxidants to retard the formation of polar compounds and thermooxidation
during prolonged frying conditions. Similarly, the advantage of blending of two
different oils to improve the thermal stability was explored. The present study brings out the
total picture on the type of degradation products formed during frying and the ways of
retarding the determination to improve upon the stability of the oil and enhancement of frying
cycles.