The Study Of Melt Fractionation Technology And The Properties Of Virgin Coconut Oil

The coconut is the important tropical crops and food energy in Hainan province where the natural coconut oil products have become the direction of the development of coconut industry. The natural coconut oil is rich in medium-chain fatty acid with a variety of functions properties, especially lauric acid (its content have reach at the level of45.1%to53.2%). This paper discussed the dry fractionation process and antimicrobial activity of virgin coconut oil. This was significant for the depth development of coconut oil and the deep processing and comprehensive utilization of coconut.First, this paper tested the some physical and chemical indexes of virgin coconut oil and found that its moisture content, impurities, and the acid value, peroxide value and other indicators were very low. The results showed that the raw material was in line with the VCO requirements of the APCC, the Philippines, Canada and the Ministry of Agriculture, even far below the standards, with high quality. The fatty acid composition included caproic acid, bitterness, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and other unsaturated fatty acids and a small amount of unsaturated fatty acids, the highest content of lauric acid (47.78%), followed by myristic acid (17.77%). This was similar with fresh coconut meat and Indonesia coconut oil fatty acid composition.The most important process in coconut oil dry fractionation was the formation and growth of crystals. Lower stirring speed (100rpm), there was uneven crystallization and the formation of partial crystallization,even agglomeration which brought about difficulties of separation, and the fractionation products had no significant difference; in the medium speed range (150-300rpm), crystallization was uniform and stable and easier to separation, the difference between melting point of fractionation products had also increased; under high speed (500rpm), the formation of crystals was not easy and the separation efficiency was unsatisfactory. The cooling rate was the key to obtain a stable crystalline form. Of the low cooling rate, the distribution of crystals was uniform, and easily separated; with cooling rate increasing, the solid fat yield showed an increasing trend. The residence time was related to the viscosity, polycrystallinity, the nature of a triglycerides stable crystalline form, the cooling rate and the different speed achieving the balance and other factors. With extension of residence time, the solid fat yield showed an increasing trend. The crystallization temperature had a significant impact on the and melting point and the solid fat yield. Under low crystallization temperature, nucleation and crystal growth rate were fast, but the viscosity increased and separated difficultly. In the experimental conditions, the proper dry fractionation process of coconut oil as follows: stirring rate200rpm, the cooling rate of8℃/h, and the best crystallization temperature was23℃when the residence time was12h.The RVA was used to determine the viscosities of coconut oil and blended oil with different rotational speed and temperature. In the range of50-350rpm, the model of palm oil viscosity and testing-speed was that μ=0.19S-1400.99/S+76.02. The viscosity of oil decreased with the increase in testing-temperature, and the correlation between viscosity and temperature was lnμ=3.33+45.85/(T+13). The viscosity of palm oil decreased with the addition of coconut oil, that the more addition of coconut oil, the greater the viscosity decreased. For the determination of palm oil viscosity, the best of condition was that testing-temperature25℃, testing-speed in the range of150rpm-200rpm, and testing-time5-7min.The filter paper disc method was used to survey the antimicrobial properties of coconut oil. The results that0.2g/mL of concentration of coconut oil significantly inhibited the four tested strains. The inhibitory effect on Escherichia coli was the strongest and the inhibition zone diameter reached at20.5mm; the zone of inhibition to Bacillus subtilis was17.75mm which was the least. Compared with the check experiment, the antibacterial activity of coconut oil was stronger than the GMC and lauric acid. Using plate method to determine the MIC, it's found that different concentration of coconut oil had different degrees of inhibitory effect on different tested strains. The MIC of Staphylococcus aureus and Bacillus subtilis were respectively0.17g/mL and0.15g/mL; The MIC of E.coli and yeast were both of0.13g/mL.