The influence of some pH values and substratum on sunflower seeds lipase activity

Abstract

The activity of sunflower seeds lipase on its own substratum (sunflower oil), and on other substrata, belonging to seven plant species, searched under certain conditions of temperature and pH, was the purpose of this work. Dried sunflower seeds (SMC =10%) – used as lipase source, and refined oils from seeds of eight plant species (sunflower, pumpkin, soya bean, sesame, almond, maize, walnut and peanut) – used as substratum for enzyme, has represented the biological material in this work. The lipase activity, expressed as μm oleic acid/gram product/min., was determined at 20ºC and three pH values (5.5, 7.4 şi 9.5), by means of titrating of fatty acids (released from oils by enzyme, in a certain time interval) with a solution of KOH. At pH 5.5, the highest enzyme activity was registered on soya been oil, followed, in order, by walnut, maize, peanut and sunflower oils (very close values for the last three ones). In this pH value, the lowest lipase activities was on pumpkin, almond and sesame oils (all very close values). At pH 7.4, the gratest lipase activity value was registered on walnut oil, followed by peanut and maize oils, and the lowest ones on soya bean and sunflower oils (close values). At pH 9.5, the highest lipase activities have been on sunflower oil, followed by walnut, pumpkin, soya bean and maize oils (close values), and the least ones on sesame and almond oils (close values). The analyse of the sunflower seeds lipase activity on the eigth substrata (sunflower, pumpkin, soya bean, sesame, almond, maize, walnut and peanut oils) at 20ºC, has highlighted the highest values at pH 5.5 and the lowest ones at pH 9.5.The sunflower seeds lipase activity, at 20ºC, was influenced both by pH values and substratum nature.