Effect of heating time on changes in physicochemical properties and fatty acid composition of red palm oil

Abstract

Crude Palm Oil (CPO) contains approximately 50% saturated fatty acids and approximately 40% unsaturated fatty acids. Unsaturated fatty acid content is known to be effective in lowering blood cholesterol levels. Palm oil also contains -carotene which is very beneficial for health. Palm oil processing is defined by three stages, namely degumming, bleaching and deodorization. The bleaching process is carried out at 90–105oC using 1-2% bleaching earth and deodorization at 240-270oC. The high concentration of bleaching earth and deodorization temperature causes carotene to be degraded leading to low carotene content in the final product. The effort to maintain the carotene content is to process CPO into red palm oil (RPO). The content of carotene and fatty acids contained therein will be damaged in the presence of high heat, ascertain this, a study was conducted on the effect of heating time on the chemical properties of red palm oil. The study was conducted using a completely randomized block design with prolonged heating treatment (0, 2, 4, 6, 8 and 10 hours) at 180oC and repeated 3 times and then the fatty acid content, peroxide value, iodine number and functional groups formed in bulk red palm oil purchased online were observed. The results showed that increasing the heating time can decrease the iodine number but increase the acid number and peroxide value. Heating at 180oC for 10 hours produced iodine, acid and peroxide value of 57.72, 9.56 and 12.55, respectively. The results of the analysis using Fourier Transform Infra-Red (FTIR) showed the presence of free fatty acids at wave number 722 cm-1 and peroxide numbers at wave number 2.854 cm-1. The test results using gas chromatography showed that linoleic acid decreased by about 3.23% during heating for up to 10 hours, while saturated fatty acids increased by about 0.32%. Key words: Cooking oil, Free fatty acid, Iodine number, Peroxide number, polymerization