Some factors affecting lipase activity in goat milk

Abstract

The influence of different temperatures (20 °C, 37 °C and 50 °C), pasteurization (71 °C for 15 s), boiling (100 °C), agitation for 5 and 10 min, pH changes (milk on acidic and alkaline side of pH), certain chemicals (copper sulphate, silver nitrate, lead nitrate and sodium chloride) on the lipase activity in local goat and cow milks was investigated. There were no significant ( P > 0.01) differences in gross chemical composition between local goat and cow milks. Lipase activity in goat milk (2.76 μeq/ml) was non-significantly lower than in cow milk (3.78 μeq/ml) at 37 °C. Lipase activity in cold milk (5 °C) was non-significantly ( P > 0.01) lower in goat milk (2.50 μeq/ml) compared to cow milk (3.22 μeq/ml). Effect of different temperatures (20 °C and 50 °C) on lipase activity was non-significantly ( P > 0.01) lower in goat milk (2.63 μeq/ml at 20 °C and 2.46 μeq/ ml at 50 °C) than in cow milk (3.65 μeq/ml and 3.43 μeq/ml, respectively). Pasteurization and boiling milk caused a non-significant ( P > 0.01) decrease in lipase activity in goat (0.47 μeq/ml and 0.10 μeq/ml) and cow (0.53 μeq/ml and 0.12 μeq/ ml) as compared to fresh goat (2.76 μeq/ml) and cow (3.78 μeq/ml) milks examined at 37 °C. Agitation showed non-significantly lower lipase activity in goat milk (6.52 μeq/ml) at 5 min and at 10 min (7.23 μeq/ml) than in cow milk at 5 min (7.17 μeq/ml) and 10 min (8.04 μeq/ml). Effects of added chemicals were more pronounced in cow milk than goat milk, but copper sulphate had more inhibition effect on lipase activity than lead, silver and sodium. Lipase activity in goat milk (4.13 μeq/ml) on the alkaline side of pH was non-significantly higher than in cow milk (3.96 μeq/ml), while it was non-significantly lower in goat milk (2.01 μeq/ml) and cow milk (2.64 μeq/ml) on the acidic side of pH. It can be concluded that lipase activity can be enhanced by agitation and alkaline side of pH or reduced by heating, pasteurizing, boiling, cooling, addition of certain chemical and the acidic side of pH.