小米糠(胚)制油及油脂品质研究

小米糠按谷子加工过程的工序不同可分为细糠和抛光粉两部分,两部分混合后的混合糠即小米糠全糠,因其中含有小米胚,因此也称小米胚。细糠和抛光粉中主要组分的质量分数分别为粗脂肪11.56%和8.6%,粗蛋白10.63%和12.41%,粗纤维20.5%和2.25%;分别采用压榨法和溶剂浸出法提取细糠、抛光粉和混合糠中的油脂,检测结果显示,小米糠油的酸价为17.58～45.43 mgKOH/g,过氧化值为0.083～0.226g/100 g,其中抛光粉所制取小米糠油的酸价和过氧化值明显高于细糠及混合糠所制取小米糠油;小米糠油中含量最多的是亚油酸(67.13%～68.81%),其次为油酸(12.86%～14.71%)、棕榈酸(7.43%～8.21%)。小米糠油中8种VE组分齐全,α-生育酚和γ-生育酚含量较高,VE总含量为789～1287 mg/kg;谷维素质量分数为0.40%～0.59%;甾醇质量分数为1.68%～2.08%,其中谷甾醇含量最高(779～932 mg/100 g),其次是谷甾烷醇;角鲨烯含量为102.45～126.22 mg/kg。小米糠油是营养丰富的食用植物油。此外,小米糠蛋白质中除赖氨酸外其余的必需氨基酸评分(AAS)均大于100,小米糠蛋白是一种优质的蛋白质资源。     

Effect of refining of crude rice bran oil on the retention of oryzanol in the refined oil

The effect of different processing steps of refining on retention or the availability of oryzanol in refined oil and the oryzanol composition of Indian paddy cultivars and commercial products of the rice bran oil (RBO) industry were investigated. Degumming and dewaxing of crude RBO removed only 1.1 and 5.9% of oryzanol while the alkali treatment removed 93.0 to 94.6% of oryzanol from the original crude oil. Irrespective of the strength of alkali (12 to 20° Be studied), retention of oryzanol in the refined RBO was only 5.4–17.2% for crude oil, 5.9–15.0% for degummed oil, and 7.0 to 9.7% for degummed and dewaxed oil. The oryzanol content of oil extracted from the bran of 18 Indian paddy cultivars ranged from 1.63 to 2.72%, which is the first report of its kind in the literature on oryzanol content. The oryzanol content ranged from 1.1 to 1.74% for physically refined RBO while for alkali-refined oil it was 0.19–0.20%. The oil subjected to physical refining (commercial sample) retained the original amount of oryzanol after refining (1.60 and 1.74%), whereas the chemically refined oil showed a considerably lower amount (0.19%). Thus, the oryzanol, which is lost during the chemical refining process, has been carried into the soapstock. The content of oryzanol of the commercial RBO, soapstock, acid oil, and deodorizer distillate were in the range: 1.7–2.1, 6.3–6.9, 3.3–7.4, and 0.79%, respectively. These results showed that the processing steps—viz., degumming (1.1%), dewaxing (5.9%), physical refining (0%), bleaching and deodorization of the oil—did not affect the content of oryzanol appreciably, while 83–95% of it was lost during alkali refining. The oryzanol composition of crude oil and soapstock as determined by high-performance liquid chromatography indicated 24-methylene cycloartanyl ferulate (30–38%) and campesteryl ferulate (24.4–26.9%) as the major ferulates. The results presented here are probably the first systematic report on oryzanol availability in differently processed RBO, soapstocks, acid oils, and for oils of Indian paddy cultivars.     

Preferential extractability of γ‐oryzanol from dried soapstock using different solvents

BACKGROUND: γ‐Oryzanol from rice bran has lately gained potential importance because of its proven health benefits. Thus the extractability of γ‐oryzanol from the soapstock of crude rice bran oil is important from the perspective of future large‐scale production, which would give value addition to this by‐product obtained from the rice bran oil industry. The aim of the present study was to investigate the extraction of γ‐oryzanol from the drum‐dried soapstock of rice bran oil using various solvents. RESULTS: It was found that γ‐oryzanol could be extracted most effectively using ethyl acetate, followed by dichloromethane and ethyl methyl ketone. All components of γ‐oryzanol have an alcohol group in the ferulate portion giving rise to relatively high polarity, thereby increasing the extraction in more polar solvents efficiently. Ethyl acetate showed maximum extractability of γ‐oryzanol by the Soxhlet method. To quantify γ‐oryzanol, reverse phase high‐performance liquid chromatography (RP‐HPLC) was used for fingerprinting the γ‐oryzanol analogues with respect to standard γ‐oryzanol. CONCLUSION: A new RP‐HPLC method for determining the individual components of γ‐oryzanol has been reported that can be used for performing an online characterisation of γ‐oryzanol analogues by liquid chromatography/mass spectrometry. Copyright © 2008 Society of Chemical Industry     

Study on the composition of rice bran oil and its higher free fatty acids value

The compositions of rice bran oils (RBO) and three commercial vegetable oils were investigated. For refined groundnut oil, refined sunflower oil, and refined safflower oil, color values were 1.5–2.0 Lovibond units, unsaponifiable matter contents were 0.15–1.40%, tocopherol contents were 30–60 mg%, and FFA levels were 0.05–0.10%, whereas refined RBO samples showed higher values of 7.6–15.5 Lovibond units for color, 2.5–3.2% for unsaponifiable matter, 48–70 mg% for tocopherols content, and 0.14–0.55% for FFA levels. Of the four oils, only RBO contained oryzanol, ranging from 0.14 to 1.39%. Highoryzanol RBO also showed higher FFA values compared with the other vegetable oils studied. The analyses of FA and glyceride compositions showed higher palmitic, oleic, and linoleic acid contents than reported values in some cases and higher partial glycerides content in RBO than the commonly used vegetable oils. Consequently, the TG level was 79.9–92% in RBO whereas it was >95% in the other oils studied. Thus, refined RBO showed higher FFA values, variable oryzanol contents, and higher partial acylglycerol contents than commercial vegetable oils having lower FFA values and higher TG levels. The higher oryzanol levels in RBO may contribute to the higher FFA values in this oil.     

近红外光谱法快速测定米糠油中谷维素的含量北大核心CSCD

为了简便、快速、准确地测定米糠油中的谷维素含量,以LS/T 6121.2—2017的高效液相色谱法为测定米糠油中谷维素含量的参比方法,采用近红外光谱分析技术结合偏最小二乘法建立了米糠油中谷维素含量的定量分析模型。结果表明:所建定量分析模型的决定系数为99.81%,预测标准差为0.02849%,交叉验证标准差为0.03113%;利用99个验证集样品对定量分析模型进行外部独立验证,预测决定系数为99.81%,预测标准差为0.03090%,用该定量分析模型检测样品绝对误差在-0.081%~0.057%之间,相对误差在-11.86%~9.84%之间。所建立的定量分析模型预测效果较好,准确度较高,可用于米糠油中谷维素含量的测定。     

高效液相色谱法测定米糠油中谷维素含量

高效液相色谱法适用于油中微量组分的定量检测,为探索适合企业内米糠油谷维素的测定方法,建立新HPLC-UV(高效液相色谱-紫外)测定方法。色谱条件如下:采用ZORBAX NH_2柱,流动相为乙醇,流速0.8~1.0 mL/min,检测波长324 nm。结果表明,米糠油中杂质不干扰样品出峰,谷维素各组成成分在同一时间出峰,且出峰时间小于10 min,线性范围为0.032 1%~1.284 0%,线性相关系数R~2=0.999 1,平均回收率为98.57%,相对标准偏差(RSD)=0.15%(n=4)。该方法稳定,专属性强,准确可靠,适用于米糠油等含谷维素油脂的测定。     

谷维素对3种食用植物油的抗氧化效果研究

从米糠油皂脚中提取纯化谷维素,按不同比例添加到大豆油、菜籽油和油茶籽油中,分别采用Schaal烘箱法和油脂氧化分析仪对3种植物油氧化稳定性进行测定,同时考察在植物油氧化过程中,谷维素对其脂肪酸组成的影响,并与常见的油脂抗氧化剂进行对比。结果表明:油脂中分别添加0.1%和0.5%谷维素均对大豆油、菜籽油和油茶籽油的氧化诱导期具有延长作用,其中对油茶籽油的作用最显著;在Schaal烘箱实验中,谷维素能够有效延缓大豆油和油茶籽油过氧化值的升高,并且对油中多不饱和脂肪酸的氧化有抑制作用,但对菜籽油的抗氧化作用不显著。     

Separation of vitamin E and γ-oryzanols from rice bran by normal-phase chromatography

Five commercial silicas [Nova-Pak, μPorasil (Waters, Milford, MA), Kromasil (Eka Nobel, Bohus, Sweden) Spherisorb (Sigma, St. Louis, MO) and Select-KP (Biotage, Charlottesville, VA)] were tested for their efficiency in separating vitamin E and γ-oryzanol components from saponified rice bran extracts, with the perspective of future large-scale purification of the various compounds. The effects of mobile phase composition, eluent flow rate, column temperature and the physical properties of the silica on the selectivity and analysis time were studied. All silicas except Select-KP gave baseline separation of the vitamin E components with isooctane/ethyl acetate (97.5∶2.5) at room temperature. However, only the 4-μm Nova-Pak spherical silica gave adequate resolution of the oryzanols into two distinct fractions with an analysis time ofcirca 20 min. Other analytical conditions, i.e., the content of the polar modifier in the mobile phase, temperature and flow rate, can be used to optimize the separation once the silica had been chosen. Speed of separation is enhanced by increasing the polarity of the eluent, temperature and flow rate, while the selectivity is reduced only slightly. The Nova-Pak silica appears resistant to deactivation from both residual water in the mobile phase and polar components left over after sample clean-up and is suitable for preparative separation of the target compounds.