| The problem of high acid value has been the difficulty of rice bran oil in its refining process. The enzymatic method to deacidification for rice bran oil is under mild conditions with the less destruction of the trace elements and high selectivity. Up to now, the acyl acceptor of enzymatic deacidification was usually glycerol, monoglyceride and so on, although they can achieve the purpose of deacidification, but it did not in conformity with the related national food laws and regulations, and no practical significance. This paper studies the process of deacidification of rice bran oil with high acid value, the immobilized lipase as the catalyst, and the phytosterols as the acyl acceptors, then to prepare the low acid value of rice bran oil riched in phytosterol esters and its applications. Thus, the relevant research results are as follows:In hexane solvent system, the immobilized Lipozyme RM IM was the reaction catalyst, and the ratio of phytosterols and free fatty acid of rice bran oil was 1:1 with 4?-sodium molecular sieves as the dehydrating agent. The optimal reation conditions: Lipozyme RM IM 3%wt(of rice bran oil), hexane 1 m L/g(of rice bran oil), 4?-sodium molecular sieves 0.1 g/g(of rice bran oil), temperature of reaction 80 oC, reaction time 72 h. Under this condition, phytosterol esters content increased from 1.48% to 30.1%, and the content of free fatty acid was decreased from 15.80% to 1.42%, the acid value was reduced from 32.023 mg KOH/g to 2.88 mg KOH/g.Rice bran oil enriched in phytosterol esters after esterifiable reaction had the basic physical and chemical properties as follows: color and lustre Y31 R5.1, iodine value 104.52 g/100 g, saponification value 182.57 mg KOH/g, unsaponifiable substance 40.17 g/kg, the peroxide value 2.06 mmol/kg. The basic component content: triglycerides 60.44%, phytosterols 3.21%, 1,3-diglycerides 2.54%, 1,2-diglycerides 1.97%, monoglyceride 0.32%, γ-oryzanol 1.705%, vitamin E 1548 mg/kg. The trace elements such as vitamin E and γ-oryzanol were little damaged. Those indicators accorded with national 4th level of rice bran oil standard, and the rice bran oil after reaction was rich in phytosterol esters and phytosterols.The storage stability studies of rice bran oil after esterifiable reaction compared with the rice bran oil before reaction and four-grade rice bran oil indicated that the change degree of composition of fatty acid, acid value, iodine value, peroxide value and vitamin E content were least in them in the process of accelerated oxidation. Rancimat accelerated oxidation experiments showed that the shelf life of rice bran oil after reaction was 16459 h(685.8 d), significantly higher than the rice bran oil before reaction 6356 h(264.8 d) and four-grade rice bran oil 2348 h(97.8 d), and described rice bran oil rich in phytosterol esters had a good oxidation stability.The organogel prepared with phytosterols and γ-oryzanol in rice bran oil without trans-fatty acids was a very promising shortening substitute. The organogel can exhibit a good hardness property. The organogel formed with the ratio of phytosterols and γ-oryzanol for 40:60, molar ratio of 1:1, was provided with the maximum hardness and the melting point, and the minimum brittleness. The hardness and the melting point of the organogel increased with the increment of the amount of phytosterols and γ- oryzanol, and the brittleness were the opposite. The mixture of phytosterol esters and phytosterols can not lead to form gel in rice bran oil. The presence of phytosterol esters exhibited antagonistic to hinder gel forming. The hardness and the viscosity increased as the amount of phytosterol esters decreased, and the melting point and the brittleness were the opposite. In addition, with the cooling process applying a shear, organogel would reduce the hardness, the viscosity and the melting point, increased brittleness, and broke up the fiber network structure. It was the β crystal form indicated from X ray diffraction pattern. As the result of polarized light, the morphology of organogel was typical clover form, and stable shape.The relationship curve of phytosterol + γ-oryzanol organogel between Solid Fat Content(SFC) and temperature is different from the commercial shortenings. SFC curve of commercial shortenings reflects the content of saturated fatty acid ester after hydrogenation. SFC can be as high as 80% at 0 oC, and the solid fat to melt at 45 oC; The SFC curve of organogel oil reflects the content of phytosterol + γ-oryzanol fiber network structure. SFC is decreased more slowly in the process of heating because the melting point of the structure is higher than shortenings.This research concerning deacidification with phytosterols as acyl acceptor complied with the relevant national food regulations, and has the wide applicable prospect. Besides, the preparation of rice bran oil rich in phytosterol esters possessed many benefitial functional compositions to human body, nutrient-rich, with excellent anti-oxidation ability and resistant storage. Beyond this, the organogel prepared with phytosterols and γ-oryzanol was a new kind of special grease with great potential. This study provided a theoretical basis for improvement of organogel’s physical properties by investigating the impact factors. |
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