EFFECT OF PROCESSING ON CONSTITUENTS AND OXIDATIVE STABILITY OF MARINE OILS

Changes in the contents of neutral and polar lipids, α-tocopherol, free fatty acids and color of seal blubber oil (SBO) and cod liver oil (CLO) during different processing steps of alkali-refining, bleaching, and deodorization were monitored. Refined, bleached and deodorized (RBD) SBO and CLO contained approximately 39 and 71% less polar lipids than their crude counterparts, respectively. There was also a reduction of 98.5 and 97.4% in the corresponding free fatty acids content of RBD-SBO and RBD-CLO. The content of α-tocopherol in both oils decreased during processing, especially at the bleaching and deodorization steps. The oxidative stability of SBO and CLO following each processing step was determined by measuring peroxide and 2-thiobarbituric acid reactive substances values. Results so obtained indicated that crude oils were most stable while their refined-bleached counterparts were least stable, perhaps due to the removal of endogenous natural antioxidants such as α-tocopherol during processing of oils.     

Comparative study of soybean oil refining using rice hull silicate and commercial adsorbents

To obtain an edible grade of soybean oil, impurity removal processes are important steps in refining. To remove coloring compounds and free fatty acids, commercial adsorbents (silica gel, activated carbon, aluminum oxide, alumina silicate, acid clay, and zeolite) and rice hull silicate (RHS) were evaluated with respect to their adsorption removal efficiencies for lutein. Various doses of commercial adsorbents and RHS were individually added to degummed soybean oil to remove lutein. The commercial adsorbents and RHS substantially reduced lutein amounts in degummed soybean oil. Silica gel was the most effective adsorbent, followed by acid clay, and RHS. Treatments with adsorbents also reduced the residual free fatty acid (FFA) content. Aluminum oxide was the most effective in removal of FFA (approximately 40% reduction). RHS and rice hull ash (RHA) showed similar deacidification effects. RHS can be used as an alternative bleaching agent as it was effective in reducing the residual FFA content in soybean oil.     

Characteristics of flaxseed hull oil

Oils from two commercial flaxseed hulls extracted by six procedures were evaluated for physicochemical characteristics. Oil yield ranged from 9% to 28% depending on solvent and extraction. Lipid fractionation of crude flaxseed hull oil yielded 92.5% neutral lipids, 3.1% phospholipids, 2.4% acidic lipids and 2.1% free fatty acids. Flaxseed hull oil exhibited three thermal transitions between −35 and −13 °C with solvent dependent polymorphism. Thermal oxidation by differential scanning calorimetry (DSC) revealed three step oxidation of flaxseed hull oil with mean onset and oxidation temperatures at 121 and 150–253 °C, respectively depending on the extraction procedure. Flaxseed hull oil exhibited two-fold difference (0.6–1.2 μm Trolox equivalent/g) in antioxidant activity measured by a photochemiluminescence (PCL) assay. Supercritical CO₂ extracted the most oil with the highest antioxidant capacity of all evaluated procedures resulting in a defatted flaxseed hull containing the highest (53 mg/g) secoisolariciresinol diglucoside (SDG) level.     

蒙脱土对植物油脱色效果的综合评价北大核心CSCD

为了开发高效、环保的食用油脱色剂,以一种环保方法(半干法)生产的蒙脱土为研究对象,研究其在不同脱色条件(脱色温度、脱色时间和脱色剂添加量)下对大豆油、葵花籽油和菜籽油品质的影响。结果表明:该蒙脱土具有吸附色素和过氧化物从而降低油脂红值和过氧化值的作用,与脱色前相比,大豆油、葵花籽油和菜籽油的红值最大降幅分别为77.4%、92.3%和87.2%,过氧化值最大降幅分别为82.7%、83.2%和91.2%;蒙脱土用于3种植物油的脱色,植物油中总甾醇和总生育酚含量下降,而酸值总体上缓慢上升。进一步研究发现,在相同的脱色条件下,蒙脱土对大豆油、葵花籽油和菜籽油的酸值、总甾醇含量和吸油率的影响结果均优于活性白土,尤其是吸油率几乎是活性白土的一半。蒙脱土可替代活性白土用于对色泽要求不是很高的植物油脱色中。     

精炼工艺对玉米油微量成分变化的影响

以在超级脱胶结合白土预脱色-复脱色以及双塔脱臭脱酸工艺生产线上取样的玉米毛油、脱胶油、脱蜡油、脱色油、脱臭油为研究对象,对其游离脂肪酸、磷、金属离子、色素、生育酚含量及过氧化值进行测定,考察精炼工艺对玉米油微量成分变化的影响。结果表明:双塔脱臭脱酸工艺可以明显降低玉米油中游离脂肪酸含量;超级脱胶工艺可去除玉米油中约95%的磷脂;脱胶和脱色可明显降低金属离子含量;大部分色素在脱色工段被去除;经脱臭后,成品油中总生育酚损失19. 9%;脱胶使玉米油过氧化值升高,脱色和脱臭可使过氧化值明显降低。说明应根据玉米毛油品质选择合适的精炼工艺,以最大限度地保留有益微量成分,去除有害成分,做到适度精炼。     

油脂脱色过程对反式酸形成和不饱和度的影响

脱色过程对油脂的品质具有多方面的影响,吸附剂在发生吸附的同时对油脂的分解和脂肪酸的异构化等反应具有一定的催化作用。采用FT-IR检测技术对油脂脱色过程中反式酸和不饱和度的变化进行了综合评价,在油脂脱色体系中,脂肪酸异构化反应是温度和吸附剂共同作用的结果,吸附剂在此过程中起到了催化作用,温度对反式酸的形成起到了关键作用,脱色过程对亚油酸和亚麻酸等多烯脂肪酸的破坏导致了油脂总不饱和度的降低。     

一级大豆油低温表现影响因素探讨

从化学组成角度探讨了一级大豆油的化学组分对其低温表现的影响,重点分析了脂肪酸组成与低温表现的相关性,考察了不同工段的油品以及不同白土添加量所得油品的低温表现情况.结果表明:在相同工艺条件下,油脂的饱和脂肪酸含量与凝固时间呈明显的负相关;随着加工工序的进行,从毛油到成品油,油品的低温表现逐渐下降;随着白土添加量的增大,所得油品越易凝固.     

Deacidification effects of rice hull-based adsorbents as affected by thermal and acid treatment

Rice hull ash (RHA) was evaluated as a source of adsorbent for edible oil processing, especially its application in reducing free fatty acid (FFA). RHA300, RHA400, RHA500, RHA600, RHA700, RHA800 and RHA900 were prepared by burning rice hulls at 300, 400, 500, 600, 700, 800 and 900 °C, respectively. Increased pyrolysis temperature resulted in an increase in pH (increased alkalinity) of RHAs from 9.53 to 9.98. RHA500 was the most effective in reducing residual FFA, followed by RHA400 and RHA300. About 30-46% reduction of FFA was observed in degummed soybean oil and more than 80% reduction in degummed oil-hexane miscella at 5 g/100 g oil of RHA500. On heating of the ash greater than 500 °C the loss of adsorptive capacity for FFA was shown in case of RHA800 and RHA900. RHA500 reduced about 50% FFA of commercial vegetable oils such as olive oil and corn oil. There was no significant adsorptive difference between the kinds of fatty acids dissolved in isooctane. Acid activation for RHA500acid did not improve the FFA adsorption relative to nonactivated RHA500.     

Effects of Bleaching on the Properties of Roasted Sesame Oil

ABSTRACT: Improvement in quality of roasted sesame oil was studied. Roasted sesame oil was bleached at 70 °C, 85 °C, or 100 °C for 20 min with acid-activated clay at 0.5%, 1.0%, or 3.0% (w/w) and then centrifuging at 12096 × g at 4 °C for 10 min. The color of the roasted sesame oil became lighter and the viscosity of oil decreased by bleaching. Bleaching caused a significant increase in the smoke point of the oil, from 170 °C to a range of 183 °C to 191 °C. Bleaching increased palmitic acid and decreased linoleic acid contents of roasted sesame oil. Bleaching decreased free fatty acid (FFA) and conjugated dienoic acid (CDA) contents and carbonyl values (CV) of roasted sesame oil. The more the acid clay was used, the lower were the FFA and CDA contents and CV of the oil. Amount of acid clay in bleaching of roasted sesame oil had higher effects on the color, viscosity, smoke point, FFA and CDA contents, and CV of roasted sesame oil than the bleaching temperature. Bleaching did not show a significant effect on tocopherol contents of the sesame oil. Bleaching tended to decrease sesamolin contents and increase sesamol contents in the roasted sesame oil. As the amount of acid clay and the bleaching temperature increased, the contents of sesamin and sesamolin in the oil decreased while sesamol contents increased.     

Comparison of the adsorbent performance between rice hull ash and rice hull silica gel according to their structural differences

The microstructures of rice hull ash (RHA) and rice hull silica (RHS) were studied to understand its adsorption for free fatty acids (FFA) of degummed soybean oil. RHAs such as RHA300, RHA500, RHA700 and RHA900 were produced by heating rice hulls at temperatures of 300, 500, 700 and 900 °C, respectively. RHS500 was formed by alkali extraction of amorphous silica from RHA500. Heating temperature affects the pore development of RHAs, resulting in elongated large pores, as evident from the SEM data. A characteristic feature of amorphous material is shown in the XRD patterns of RHAs and RHS500 except RHA900. Although RHA500 has much lower surface area and pore volume compared to RHS500, it showed similar effectiveness in reducing FFA content of degummed soybean oil. It might be ascribed by higher macroporosity of RHA500 compared with RHS500, which was shown in the results of N₂ adsorption.     

黑豆油理化指标及脂肪酸组成分析

黑豆系为食药两用植物种籽,为更好开发和利用黑豆资源,分别对南北黑豆油理化指标、脂肪酸组成及甘油三酯组成进行测定。结果表明,黑豆含油量为17%左右,粗蛋白含量达46%左右,粗纤维含量为4.5%左右;黑豆油富含油酸和亚油酸,不饱和脂肪酸含量高达80%以上。     

植物油中的色素及吸附脱色研究进展北大核心CSCD

植物油中的色素不仅会影响油脂的色泽,还会降低油脂的品质和贮藏稳定性。脱色过程是去除油脂不良色泽的重要工序,而吸附脱色是油脂企业加工过程中最常用的脱色方法。概述了植物油中色素的来源以及色素的存在对油脂营养和安全性的影响,简要介绍了膜脱色法、光能脱色法、超声辅助脱色法、热脱色法、吸附脱色法等常见的脱色方法,综述了活性白土、活性炭、凹凸棒土(石)、硅胶和复合脱色剂等吸附剂的应用研究进展,总结了吸附脱色目前所存在的问题,如脱色过程中废白土处理率低、深色油脂脱色难,并提出了解决建议(提高废白土中油脂的回收利用,开发针对性的脱色方法等),最后针对目前油脂工业脱色技术的现状和在脱色过程中需要解决的问题进行了思考和展望。     

Determination of Frying Quality of Vegetable Oils used for Preparing Falafel using Infrared Spectroscopy and Multivariate Calibration

The frying qualities of palm and soybean oils are determined using infrared spectroscopy and multivariate calibration. Compare to soybean oil, palm oil is more resistive to the chemical and physical changes and this is attributed to the high degree of unsaturation of soybean oil (61.9%) compare to palm oil (13.8%). After 48 h in service, the oil samples were effectively clustered into two groups using principal component analysis which indicated that both oils still maintain their chemical identities. Partial least squares regression (PLS1 and PLS2) a long with mid-FTIR data are used for predicting free fatty acid, viscosity, and total polar compounds of the used oils without running expensive standard procedures. PLS1 and PLS2 outperformed PCR and MLR for predicting the quality indicators of the frying oils. For palm oil and at the optimum calibration conditions, the obtained accuracies (SD) are 105.6% (0.05), 99.8% (1.10), and 103.9% (0.16) for free fatty acid, viscosity, and total polar compounds, respectively. The proposed method is simple, less-expensive, and has comparable accuracy/precision with standard procedures that often used for monitoring frying oils.     

响应面试验优化油脂分段脱色工艺

利用多次吸附平衡可有效降低油脂的色泽原理,采用单因素试验探究分段脱色工艺对大豆油脱色效果的影响,然后通过响应面法获得最佳脱色工艺参数。在添加总量一定时,将活性白土分3 段进行添加,通过改变每段添加量比例,确定最佳吸附平衡的条件;在搅拌速率为150 r/min时,活性白土添加总量1.27%、脱色温度100 ℃、脱色总时间60 min,脱色油脂酸值为0.12 mg KOH/g,过氧化值为3.26 mmol/kg,色泽为黄18、红1.45,相对于常规脱色工艺活性白土用量减少9.29%,提高了油脂的精炼率。     

凹凸棒石油脂脱色行为及其机理

以凹凸棒石为大豆油脱色吸附剂,通过对其物理特性、脱色热力学和吸附动力学分析,探讨凹凸棒石吸附剂的吸附行为与脱色机理。结果表明,凹凸棒石吸附剂主要为短晶束和单晶形,其孔径集中分布于1.5～10.0?nm的范围内;脱色热力学分析表明,随着脱色温度升高,凹凸棒石的色素吸附能力逐渐增强,但温度不能改变吸附剂对色素类物质的作用方式;吸附动力学分析表明,叶绿素等微量成分在凹凸棒石上的吸附速率较快,正己烷纯溶液体系中吸附速率依次为叶绿素＞亚油酸＞磷脂＞类胡萝卜素,而大豆油体系中吸附速率依次为叶绿素＞类胡萝卜素＞游离脂肪酸＞磷脂。由此可知,凹凸棒石油脂脱色主要通过孔径填充吸附,并伴随有部分氢键吸附和化学吸附。     

部分食品煎炸用油的反式脂肪酸比较

为探究不同品种食用油和煎炸食品对反式脂肪酸形成的影响,本文使用5种食用油(葵花油、大豆油、菜籽油、棕榈油、花生油),在一定温度下炸制14批次油条,又依次使用大豆油炸制豆腐、油条和鸡腿,对2种情况下产生的煎炸油进行气相色谱分析,比较反式脂肪酸含量。结果表明:炸油条过程中,食用油中反式脂肪酸的含量均随着煎炸时间的延长而增加,葵花油中反式亚油酸总含量最多(约12 mg/g),花生油中反式油酸含量最低(约0.6 mg/g),在煎炸过程中,大豆油中反式脂肪酸的含量无显著变化,保持在3.5 mg/g左右。比较可知,不同种类食用油在加热过程中产生的反式脂肪酸含量有较大差异,而使用大豆油分别炸制豆腐、油条和鸡腿时,煎炸油中的反式脂肪酸无显著差异,说明油炸过程中的反式脂肪酸主要来源于食用油中不饱和脂肪酸的氧化裂解和异构化,与煎炸食品关系不大。从反式脂肪酸的生成量来看,烹饪过程中长时间煎炸建议使用大豆油,而不适宜使用葵花油。     

Effects of post-drying methods on pomelo fruit peels

Process conditions of alkali refining, bleaching, and deodorization of crude chufa oil extracted from chufa (Cyperus esculentus L.) tubers grown in Korea were optimized to obtain an edible grade vegetable oil. The overall scope of refining conditions was similar to other vegetable oils. The degumming process, however, could be omitted since phospholipids were removed during alkalirefining and bleaching processes. RBD (alkali-refined, bleached, and deodorized) chufa oil fully satisfied Korean quality standards for edible vegetable oil. Chufa oil contained a high level of oleic acid, along with palmitic acid and linoleic acid. Physicochemical properties of chufa oil were similar to olive oil. The order of oxidative stability of chufa oil was crude>deodorized>degummed>refined>bleached oil. RBD chufa oil was virtually colorless and bland tasting, and was considered suitable for edible purposes.     

摄食不同来源磷脂对大鼠脂质代谢及脑内磷脂脂肪酸组成的影响

研究了摄食不同来源磷脂对大鼠脂质代谢及其脑内磷脂脂肪酸组成的影响。雄性SD大鼠按体重随机分为大豆油对照组(添加9%)、牛乳磷脂组(添加5%)、大豆磷脂组(添加5%)、蛋黄磷脂组(添加5%),喂食3周。检测了血清总胆固醇(TC)、甘油三酯(TG)、高密度脂蛋白胆固醇(HDL-C)、游离脂肪酸(FFA)及肝脏TC、TG、磷脂(PL)的含量,并用气相色谱法测定了脑内磷脂脂肪酸的组成变化。结果显示:与大豆油对照组相比,3种磷脂均不同程度提高了大鼠体重、脏器指数,蛋黄磷脂效果显著;3种磷脂不同程度降低了血清TC、TG和FFA含量,牛乳磷脂降低血清FFA显著,大豆磷脂降低血清TC、TG显著,蛋黄磷脂降低FFA显著,大豆磷脂显著提升了血清HDL-C含量;3种磷脂不同程度降低了肝脏TC、TG、PL含量,牛乳磷脂与大豆磷脂降低肝脏TG、TC显著,而蛋黄磷脂降低肝脏TG显著;3种磷脂对脑内磷脂脂肪酸组成的影响各不相同,牛乳磷脂显著提高了脑内磷脂饱和脂肪酸含量,而大豆磷脂和蛋黄磷脂提高了DHA等多不饱和脂肪酸含量。研究表明,3种磷脂均有降血脂、肝脂作用,以大豆磷脂作用尤为明显,大豆磷脂和蛋黄磷脂的益智作用可能优于牛乳磷脂。     

The composition of lipids from rice hulls and from the surface of rice caryopsis

Samples of hulls, of whole and ground caryopsis and of bran obtained from the Brazilian rice variety IAC 1246, were extracted with hexane and the characteristics and composition of the corresponding lipids were determined. The lipids from rice hulls showed a four times higher content of unsaponifiable matter and of free fatty acids than those from rice bran and rice caryopsis. There were also differences in the fatty acid composition as evidenced by the presence of 2–3% of saturated C₂₂ and C₂₄ acids and a lower proportion of unsaturated acids in the rice hull lipids. On the other hand there was a close resemblance between the rice hull lipids and those on the surface of the caryopsis. Chromatographic analysis of the unsaponifiable matter of lipids from rice hulls and caryopsis surface disclosed the presence of hydrocarbons, alcohols and sterols in ascending order, the sterols consisting of about 50% of β-sitosterol, 20–40% of campesterol, 10–20% of stigmasterol and 2–3% of cholesterol. On the basis of the above results it was concluded that a preliminary solvent extraction of paddy rice in order to remove the waxy lipids from the hulls and the caryopsis surface would benefit the subsequent milling process and improve the quality of the brown rice and of crude rice bran oil.     

磷脂与游离脂肪酸对油脂烟点和氧化稳定性的影响

考察了磷脂含量、游离脂肪酸含量、游离脂肪酸碳原子数和不饱和度对花生油和山茶油烟点和氧化稳定性的影响。结果表明:磷脂含量对油脂烟点影响很大,含量越高,烟点越低,对油脂氧化稳定性表现出不同规律,其对花生油氧化稳定性有一定的提高作用,而对山茶油则影响不大;游离脂肪酸含量越高、游离脂肪酸碳原子数越少和不饱和度越大,油脂的烟点越低、氧化稳定性越差,并且相对于氧化稳定性,对烟点的影响要大得多。