Abstract
A commercial enzyme preparation consisting of pectolytic, cellulotic and hemicellulotic enzymes was applied to the oil extraction by cold pressing from apricot kernel, flaxseed and grape seed. The effects of enzyme pre-treatment varied depending on the different oil seed used as raw material. Although the increase in free fatty acidity can be considered as a negative effect (from 0.37 to 0.52), the decrease in peroxide number and p-anisidine values, increase in oil yield (22.75%), higher levels of total carotenoids and tocopherols, as well as a remarkable increase in phenolic content (x1.68) and radical scavenging effect (including hydrophilic and lipophilic-induced and total antioxidant capacity) showed that the use of enzyme application in the cold pressing of apricot kernel oil would be beneficial. Many of these positive results could not be achieved in the pressing of flaxseed or grape seed oils under the same conditions. A high negative correlation (r=-92.2) was found between p-anisidine value and δ-tocopherol for grapeseed oil. Hydrophilic and lipophilic antioxidant capacity, total phenolics, and total carotenoids negatively correlated well (r values above 80) with peroxide values for apricot seed oil. Correlation results showed that carotenoids play an important role in the oxidative stability of the oils, where it was much more evident for apricot seed oil (r=-97.5).
Highlights
The cold pressing of oils can be carried out in a screw press or hydraulic press and any organic solvent or external heat is not implied
The pre-treatment of mixed enzyme formulation on apricot kernel resulted in 47.33% oil recovery which was 14.22% more than that obtained without enzymes as reported in the study of Bisht et al (2015)
An enzymatic treatment for 9 hours at 50% moisture along with pre-heating, grape seed oil extraction yield was raised by 59.4% in comparison to the yield obtained from the control without enzymes (Tobar et al, 2005)
Summary
The cold pressing of oils can be carried out in a screw press or hydraulic press and any organic solvent or external heat is not implied. Oil production is mostly done by solvent extraction; for some oils such as virgin olive oil, sesame oil or rapeseed oil, pressing is preferred due to their specific properties. Mechanical pressing has the advantage of safety and simplicity throughout the process, it is less harmful, requires a short time period, and only a small amount of raw materials is necessary for extraction from different oilseeds (Oyinlola et al, 2004). The pressed materials have better natural properties; end products are free of chemicals such as free fatty acids, trans fatty acids and oxidative products (Khan and Hanna, 1983). The higher degree of naturalness of the product obtained and the fact that it is rich in bioactive components explains why these products are increasingly found in markets which sell less processed foods
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