Effect of roasting and microwave pre-treatment on the yield, quality, total phenols and antioxidant capacity of oil from red pumpkin seed (Cucurbita Pepo L) by mechanical pressing.

Abstract

Pumpkin seeds (Cucurbita pepo L.) contain rich oil, which was considered as a rich source of bioactive compounds. Although pumpkin seed oil obtained from mechanical pressing expressed a good aspect in quality, oil yield was a concerned disadvantage. In this study, investigations of thermal pre-treatment were applied at different conditions by mechanical pressing, subsequently compared with control sample in order to get the highest quality and quantity. The aim of this work was to evaluate the yield and physiochemical properties of oil by different pre-treatment factors and extraction methods. The fresh pumpkin seeds were treated with microwave duration time (1-3 min), roasting time (30-60 min), roasting temperature (90-130oC) and applied hot or cold pressing to get a crude oil. The optimal condition for pumpkin seed oil extracted by hot and cold pressing were microwave in 2 minutes and roasting in 45 minutes, respectively. The best oil product by using hot press extraction got a highest oil yield (25.55%) and a good quality with free-fatty acid (3.17% as oleic acid), peroxide value (9.5 meqO2/kg), antioxidant capacity (66.89%), total phenolic content (51.4 mgGAE/100g) and total carotenoid content (3361.37 mgβ-carotene/kg). Similarly, the best oil product which using cold pressing got a quantity at 39.94% with free-fatty acid (3.53% as oleic acid), peroxide value (4.17 meqO2/kg), antioxidant capacity (42.15%), total carotenoid content (1671.6 mgβ-carotene/kg) and total phenolic content (73.93 mgGAE/100g). The predominant fatty acids were found in oil included oleic acid, linoleic acid, palmitic acid and stearic acid. Key words: antioxidant capacity, mechanical pressing, pumpkin seed oil, thermal pre-treatment, total carotenoid content, total phenolic content.