【作者】 姚梅桑；

【导师】 胡秋辉；

【作者基本信息】 南京农业大学 ， 食品科学， 2008， 硕士

【摘要】 本研究采用普通米糠和富硒米糠为原料。首先优化了微波处理米糠的工艺参数,并将处理和未处理的米糠进行储藏对照;其次采用正交设计优化超临界CO₂萃取米糠油的工艺参数,并研究了米糠萃取物的iN Vitro抗氧化活性;最后采用精炼工艺,比较了粗米糠油和精炼米糠油的理化品质和脂肪酸组成。研究结果如下:1.优化微波处理米糠的工艺参数,选取加热功率、处理时间和料层厚度三个因素。微波处理普通米糠和富硒米糠的较佳工艺参数:加热功率1000 W,加热时间90 s,料层厚度20 mm。其中加热时间、加热功率是对微波稳定化效果影响较大的两个因素。2.将微波处理和未处理的米糠进行储藏对照,研究微波处理对米糠贮藏性能的影响。结果表明,随着贮存时间的延长,普通米糠和富硒米糠处理组的游离脂肪酸值（FFA）要显著低于对照组的。其中微波处理并冷藏（0-5℃）条件下的米糠,其游离脂肪酸值（FFA）最低,小于11%。然而,冷藏（0-5℃）对脂酶活性的抑制作用并不显著,无法有效防止米糠的酸败。3.不论是普通米糠还是富硒米糠,影响超临界CO₂萃取米糠油的主要因素顺序为:萃取压力＞萃取时间＞萃取温度＞CO₂流量。普通米糠和富硒米糠的油脂最高得率分别为15.62%和20.78%。由于考虑设备和费用,确定普通米糠油和富硒米糠油的最佳的工艺参数:萃取温度45℃,萃取压力35 MPa,流量45 kg/h,时间90 min。4.从清除DPPH自由基和抑制亚油酸氧化方面来评价粗米糠油的抗氧化活性。普通米糠油的清除DPPH自由基能力比富硒米糠油高,但是普通米糠油和富硒米糠油的抑制脂质过氧化能力并没有显著性差异,并与α-tocopherol相当。5.根据硒含量,发现硒不溶于萃取物（主要成分是油脂）中,而存在于萃余物中。因此,硒含量对米糠油的抗氧化能力没有显著贡献。普通米糠油的谷维素含量显著高于富硒米糠油的,而且超临界萃取物的谷维素含量显著高于正己烷提取物的。6.通过精炼工序（脱胶、脱蜡和脱酸）后,普通米糠和富硒米糠油的游离脂肪酸值在0.5-1.0 mgKOH/g范围内,而且胶蜡含量和磷含量显著下降。发现精炼后的米糠油的品质提高,主要体现在不饱和脂肪酸含量升高,而且饱和脂肪酸含量下降。更多还原

【Abstract】 In the present study, regular and selenium-enriched rice brans were used as experimental materials. Firstly, the microwave heating parameters of rice bran samples were optimized, and raw and stabilized rice bran samples were compared during the storage. Secondly, the optimum extraction conditions of rice bran oil from both materials were obtained through an orthogonal design by supercritical carbon dioxide extraction （SC-CO₂）, and in vitro antioxidant activities of the resulting extracts were investigated. Finally, comparisons of the physiochemical properties and the fatty acid compositions were conducted by refining method between refined rice bran oils and crude rice bran oils. The results were shown as follows:1. The microwave heating parameters of rice bran samples were optimized by choosing the key factors, including power, time and thickness. The optimized parameters for microwave heating of the regular and selenium-enriched rice bran were as follows: power 1000 W, time 90 s, thickness 20 mm. Among these factors, time and power were the main factors influencing the microwave stabilization.2. The effect of microwave heating on storage characteristics of stabilized and raw samples was studied during the storage times. The results indicated that free fatty acid levels （FFA） of stabilized samples were significantly lower than that of raw samples with time prolonged. And the lowest FFA levels of < 11% were observed in the stabilized samples when stored in the refrigerator （0-5℃）. However, chilled storage （0-5℃） did not significantly inhibit the lipase activity and prevent the rancidity of rice bran.3. The main factors influencing extraction yield by supercritical carbon dioxide extraction ranged in the following order: extraction pressure > extraction time > extraction temperature > CO₂ flow rate. The highest yields of regular and selenium-enriched rice bran oil reached 15.62% and 20.78%, respectively. Taking the equipments and cost into account, the optimized parameters for both regular and selenium-enriched rice bran oil were: extraction temperature 45℃, extraction pressure 35 MPa, CO₂ flow rate 45 kg h^-1 and extraction time 90 min.4. Antioxidant capacity of crude rice bran oil were evaluated by the scavenging DPPH radical and the lipid peroxide inhibition. Regular rice bran oil exhibited higher ability of scavenging DPPH radical in contrast with selenium-enriched rice bran oil. However, there were no significant differences on lipid peroxide inhibition between regular and selenium-enriched rice bran oil as well asα-tocopherol.5. Based on selenium content, it was concluded that selenium was not retained in the extracts but in the remains. Therefore, the selenium did not significantly contribute to antioxidant activity of rice bran oil. Moreover, the oryzanol content of regular rice bran oil was significantly higher than that of selenium-enriched rice bran oil, and the oryzanol of the SC-CO₂ extracts was higher than that of the Soxhlet extracts.6. The FFA levels of refined regular and selenium-enriched rice bran oil ranged from 0.5 to 1.0 mg KOH/g after refining process （degumming, dewaxing and deacidification）. The contents of gum & wax and phosphrous were significantly decreased. In conclusion, the quality of refined rice bran oil was improved, which was mainly attributed to the increased unsaturated fatty acid and decreased saturated fatty acid contents.更多还原