Kamal Gandhi

Effect of added herb extracts on oxidative stability of ghee (butter oil) during accelerated oxidation condition

The antioxidant activities of vidarikand (Pueraria tuberosa), shatavari (Asparagus racemosus) and ashwagandha (Withania somnifera) extracts (aqueous and ethanolic) were evaluated and compared with BHA using β-carotene bleaching assay, DPPH assay and Rancimat method. Phenolic contents of ethanolic extracts of herbs were high compared to their aqueous extracts. The ethanolic extracts showed more antioxidant activity (β-carotene–linoleic acid model system) than their aqueous counterparts. In DPPH system also, ethanolic extracts were superior to that of aqueous extracts. The ethanolic extracts of the herbs were more effective in preventing the development of the peroxide value and conjugated diene in ghee compared to their aqueous extracts. Ethanolic extracts of herbs showed the higher induction period as compared to their aqueous counter parts in the Rancimat. Antioxidant activity of the herbs decreased in the order vidarikand > ashwagandha > shatavari. Thus, the ethanolic extract of vidarikand was having the maximum antioxidant activity among all the herbs.

Effect of Operational Parameters on Determination of Oxidative Stability Measured by Rancimat Method

Operational parameters of Rancimat, including sample weight (3, 6, 9 g), airflow rate (10, 15, 20 L/h) and temperature (110, 120, 130°C) were evaluated to determine their effects on oxidative stability index, temperature coefficient, Q10 number, and shelf life prediction of ghee (anhydrous milk fat). These parameters showed statistically significant effects on the oxidative stability index. It was observed that when the sample weight and airflow rate at a given temperature were at saturated air condition, the oxidative stability indexes showed no significant differences (p < 0). As the temperature increased, oxidative stability index decreased and average coefficient of variation was minimal at 120°C. The conditions under which the ghee sample was saturated with air and had a relatively lower oxidative stability index, was with sample weight of 6 g, temperature at 120°C and an airflow rate of 15 L/h. Temperature coefficient and Q10 number were independent of sample weight and air flow rate, however, they had a significant effect on shelf life prediction of ghee.