Effect of Storage Life of Rice Bran on the Quality of Oil

Sharmin Akter

doi:10.11648/j.jfns.20170501.12

Abstract

Rice is one of the staple food in Bangladesh. The most important milling by-product of rice is ‘rice bran' which is an excellent source of edible oil. Due to the poor storage facility in the rice milling industry, the quality of rice bran gets deteriorates rapidly. This study examines the deterioration level of rice bran during the storage period in average room temperature (31°C). Raw, partially parboiled and parboiled rice bran was collected right after milling. Oil is extracted by ‘hexane solvent extraction' method from the 1st day of storage period for one week with the interval. Free fatty acid level, lipase activity, Iodine value and the pH value was determined from the collected rice bran oil. The preliminary result of this study showed that the deterioration level is rapidly increased during the 1 week of storage and the maximum deterioration level was found in raw rice bran. The free fatty acid (FFA) level, the degree of unsaturation and pH was respectively 17.25%, 92g Iodine/100ml oil and 3.10, whereas in parboiled rice bran it was respectively 4.23%, 101.1g Iodine/100ml oil and 6.23. Since the parboiled rice bran undergoes through a traditional stabilization method of parboiling and drying before milling, it might be a reason for the lower level of deterioration. The oil collected right after milling also showed a lower lipase activity. This study can be concluded by considering that, the less the storage time the better is the quality of the oil.

Highlights

Rice bran, which includes the pericarp, the aleurone and sub-aleurone layers, parts of the germ and the embryo as well as small portions of the starchy endosperm [1, 2], is a major co-product of rice milling process accounting for 5–8% of milled rice [3]
This paper presented data on the lipase activity of rice bran due to free fatty acid content, degree of unsaturation and pH level of three different types of rice bran following storage period
Partial parboiled rice bran was collected from Madina auto rice mill located in Tangail, and Un-parboiled rice bran was collected from BRRI (Bangladesh Rice Research Institute)

Summary

Introduction

Rice bran, which includes the pericarp, the aleurone and sub-aleurone layers, parts of the germ and the embryo as well as small portions of the starchy endosperm [1, 2], is a major co-product of rice milling process accounting for 5–8% of milled rice [3]. 10% of the weight of rough rice, is rich in oil (15- 22%), depending on the milling procedure and the rice variety [1, 4]. Raw rice bran contains active lipolytic enzymes- lipases, which hydrolyses the triglycerides and releases free fatty acid from the rice bran. The lypolytic action of the enzymes is responsible for the deterioration of the rice bran and oil during storage, as the cause rancidity due to the increase of FFA [5]. Rapid increase in the free fatty acid occurs within hours and reaches 7-8% within 24 hours, followed by about 5% increase per day [6, 7]. Lipase activity is enormously affected by different kind of relative factors such as moisture, temperature, pH, time and water activity [8,9,10]

Objectives

Methods

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Discussion

Conclusion