EFFECT OF AIR FRYING AS HEAT PRE-TREATMENT ON THE PHENOLIC COMPOUNDS OF DE-OILED LOWER-GRADE YELLOW MUSTARD SEEDS

Lower grade yellow mustard seeds (LGYMS), a by-product of the mustard milling process have potential as value-added products in food, feed, and agro-allied industries. Roasting in the presence of dry air is one of the easiest and simplest methods of heat treatment manifesting low operational costs. The under-utilized by-products of mustard, in addition to hot air treatment, can be used for the efficient release and extraction of bioactive phenolic compounds. This study investigated the effects of hot air treatment with different extraction temperatures (120, 140, 160 and 180 °C) and time (5, 10, 15 and 20 min) on phenolic compounds in defatted LGYMS. In lower grade yellow mustard meal fraction (LGYMM), sinapine was the major phenolic compound and its concentration decreased significantly (p < 0.05) with prolonged time. The concentration of majority of the phenolic compounds significantly (p < 0.05) decreased with increased temperature-time with exception at 180 °C where three thermo-generative compounds were detected. SA was present in trace amounts from 120° C to 160° C and was absent in all the time ranges at 180 °C. The highest antioxidant activity was observed for the extracts at 180 °C for 15 and 20 min. Interestingly, canolol was absent in the meal fractions of LGYMM and suggests the role of an oil-based medium as necessary for canolol formation. This study demonstrated that air frying (preheating) of LGYMM at 180 °C for 15 and 20 min proved to be the optimum condition to obtain the maximum antioxidant potential.