脱臭过程对油脂反式脂肪酸含量的影响

针对我国油脂企业的实际工业化生产现状,通过对国内油脂企业实际生产过程脱臭前后反式脂肪酸的分析,初步探讨了工业化生产中不同脱臭条件下油脂反式脂肪酸的形成,以期为有关油脂反式脂肪酸的深入研究及我国制定相应的反式脂肪酸限量标准提供基础数据。     

不同食用油氧化稳定性比较研究

为了比较不同食用油的氧化稳定性,选取紫苏油、亚麻籽油、核桃油、菜籽油和芝麻油5种食用油为原料,以烘箱法为对照,分别采用涂膜法和模拟法以过氧化值和酸值为考察指标对其氧化稳定性进行评价,并对其氧化过程中的脂肪酸组成变化进行探讨。结果表明:5种食用油氧化稳定性从高到低依次为:芝麻油菜籽油核桃油亚麻籽油紫苏油;在氧化初期,多不饱和脂肪酸含量减少,单不饱和脂肪酸含量和饱和脂肪酸含量有不同程度的增加,多不饱和脂肪酸含量对食用油氧化稳定性具有明显的影响,特别是亚麻酸含量;在评价氧化稳定性的方法中,烘箱法操作简便但无法反映氧化实际情况,涂膜法检测过程高效且实时,模拟法可反映食用油在使用中的实际氧化过程。     

食用油使用过程中存贮条件对其氧化稳定性的影响研究

研究了大豆油、菜籽油、棕榈油等几种食用油在使用过程中不同存贮条件下的氧化稳定性。将食用油启封,放置在不同的环境里,检测其过氧化值和酸值的变化。结果表明:避光存贮31 d,食用油的过氧化值均低于8 mmol/kg,酸值(KOH)达到0.26~0.35 mg/g;而在室内日光直接照射的条件下存贮31 d,各食用油的过氧化值均高于10 mmol/kg,酸值(KOH)达到0.35~0.45 mg/g。实验表明,启封后的食用油,存贮于避光处可以连续使用30 d以上,而置于室内日光直接照射条件下,其连续使用期只有3周。对比实验中,棕榈油氧化稳定性优于其他油脂。     

Use of antioxidants for enhancing oxidative stability of bulk edible oils: a review

Edible oils industry is using synthetic and natural antioxidants to enhance the oxidative stability of bulk edible oils. Due to safety concerns of BHA, BHT and TBHQ, there is an ongoing effort to find an effective and safe replacement. Finding a safe antioxidant or its synergistic mixture, which delays, retard or prevent the oxidation of bulk oil without changing the colour or flavour upon addition is a challenge. In this review, a brief account of chemical basis of oxidative deterioration of the stored oil is given. The effectiveness of most widely experimented antioxidants such as tocopherols, carotenoids, ascorbic acid and its derivatives, lignan compounds, flavonoids, polyphenols and phenolic acids in various edible oils have been reviewed. Further, the synergistic and antagonistic combination of these antioxidants in controlling oxidative degradation of edible oils has been discussed.     

不同脂肪酸组成的食用油热氧化稳定性研究

为研究高温加热对不同脂肪酸组成的食用油氧化稳定性的影响,用170℃高温连续三天分别加热富含饱和脂肪酸的棕榈油、富含多不饱和脂肪酸的花生油以及富含单不饱和脂肪酸的山茶油,检测其酸价、碘值、过氧化值、p-茴香胺值、全氧化值、维生素E含量及脂肪酸组成的变化。结果表明:经过加热处理的三种食用油与未加热处理的相比,7个指标均存在显著性差异（p<0.05）。加热过程中,山茶油的过氧化值增加量最大,且加热对花生油的酸价、碘值、p-茴香胺值、全氧化值影响最大;维生素E含量急剧降低;脂肪酸组成的变化明显,反式脂肪酸的增加量最高,高达1.53%。三种食用油的热氧化稳定性依次为:山茶油>棕榈油>花生油;食用油氧化稳定性可能主要由其脂肪酸的组成（COX值）决定,当COX值相近时维生素E含量影响其氧化稳定性。      

Effect of fatty acid profile in vegetable oils and antioxidant supplementation on dairy cattle performance and milk fat depression

This study was conducted to evaluate the effect of dietary supplementation of unprotected vegetable oils differing in fatty acid profiles with or without a commercial antioxidant (Agrado Plus, Novus International, St. Charles, MO) on dairy cattle performance, milk fatty acid profiles, and milk fat depression. Twenty-four multiparous Holstein cows were blocked by production (high and low) and assigned to Agrado Plus or no Agrado Plus diets as the main plot in this experiment. The 6 cows in each of the fixed effect groups (high with and without Agrado, low with and without Agrado) were then assigned to a 6 × 6 Latin square as a split plot with 21-d periods. The 6 dietary treatments in the split-plot Latin square were no added oil (control), or 5% DM as oil from palm (PO), high-oleic safflower (OSAF), high-linoleic safflower (LSAF), linseed (LNSD), or corn (CO). Added oil replaced corn starch in the total mixed ration. Diets were formulated to have similar crude protein and neutral detergent fiber, and consisted of 41.2% alfalfa silage, 18.3% corn silage, and 40.5% concentrate mix (dry matter basis). Feeding Agrado Plus did not affect milk, milk fat, or milk protein production or milk fatty acid composition in this study. No significant differences were found between oil feeding versus control for dry matter intake, milk yield, and milk protein yield, but oils other than PO significantly decreased milk fat concentration and proportion and yield of milk short- and medium-chain fatty acids (C_<16). Feeding PO effectively maintained milk fat yield (1.18 kg/d) and concentration (3.44%), whereas the oils rich in linoleic acid (CO and LSAF) significantly decreased milk fat yield (0.98 and 0.86 vs. 1.14 kg/d) and concentration (3.05 and 2.83 vs. 3.41%) compared with control. Similar lactation performance between OSAF and LNSD suggests that oleic and linolenic acids are roughly equal in potency of milk fat depression.     

几种特种食用油脂的营养价值及功效

分别介绍了油荼籽油、红花籽油、米糠油、葡萄籽油等几种具有代表性的特种油脂的化学组成及特点,并分析和总结了各特种食用油脂的营养价值与功效。     

不同熔点棕榈油脂肪酸组成和SFC测定分析

分析七种不同棕榈油脂肪酸组成及在0℃~25℃(5℃间隔)温度下固体脂肪含量(SFC)及其变化规律。结果表明:随熔点降低,棕榈酸含量有逐渐降低趋势,而油酸和亚油酸含量则逐渐上升;饱和脂肪酸含量逐渐减少,而不饱和脂肪酸含量则逐渐升高;低熔点棕榈油营养价值要比高熔点棕榈油高;在不同温度段,SFC值增加幅度有所不同。该试验为棕榈油进一步深加工研究提供参考数据。     

Effects of intravenous infusion of conjugated diene 18:3 isomers on milk fat synthesis in lactating dairy cows

It has been previously established that trans-10, cis-12 conjugated linoleic acid plays an important role in milk fat depression (MFD). However, in many situations of dietary induced MFD, the reduction in milk fat synthesis is much greater than what would be predicted based on the milk fat concentration of trans-10, cis-12 18:2. These observations suggest that other biohydrogenation intermediates could be implicated in MFD. The objective of this study was to evaluate the effects on milk fat synthesis of an intravenous administration of 2 conjugated diene 18:3 isomers (cis-9, trans-11, cis-15 and cis-9, trans-13, cis-15 18:3), which are intermediates in ruminal biohydrogenation of α-linolenic acid. Three multiparous Holstein dairy cows (days in milk = 189 ± 37 d; body weight = 640 ± 69 kg; mean ± standard deviation), fitted with indwelling jugular catheters, were randomly assigned to a 3 × 3 Latin square design. For the first 5 d of each period, cows were infused intravenously with a 15% lipid emulsion providing 1) cis-9, trans-11, cis-15 18:3 + cis-9, trans-13, cis-15 18:3 + trans-10, cis-12 18:2 (CD18:3 + CLA); 2) cis-9, cis-12, cis-15 18:3 + cis-9, cis-12 18:2 as a control (ALA + LA); or 3) cis-9, cis-12, cis-15 18:3 + trans-10, cis-12 18:2, as a positive control (ALA + CLA). Milk production was recorded, and milk was sampled daily at each milking for analyses of fat, protein, lactose, milk urea nitrogen, and somatic cell count. Dry matter intake, milk yield, and milk protein were not affected by treatment. Over the experimental period, milk fat content was decreased by 7% for cows that received either ALA + CLA or CD18:3 + CLA compared with ALA + LA. The temporal pattern of milk fat content showed a linear decrease during the infusion period for ALA + CLA and CD18:3 + CLA treatment groups. The transfer efficiencies of conjugated diene 18:3 isomers into milk fat averaged 39 and 32% for cis-9, trans-11, cis-15 18:3 and cis-9, trans-13, cis-15 18:3, respectively. The CD18:3 + CLA treatment had no effect on milk fat concentration beyond that attributable to its trans-10, cis-12 18:2 content. In conclusion, results from the current study offered no support for a role of either cis-9, trans-11, cis-15 18:3 or cis-9, trans-13, cis-15 in MFD.     

Preparation of liposomes from milk fat globule membrane phospholipids using a microfluidizer

The isolation of milk fat globule membrane (MFGM) material from buttermilk on a commercial scale has provided a new ingredient rich in phospholipids and sphingolipids. An MFGM-derived phospholipid fraction was used to produce liposomes via a high-pressure homogenizer (Microfluidizer). This technique does not require the use of solvents or detergents, and is suitable for use in the food industry. The liposome dispersion had an average hydrodynamic diameter of 95 nm, with a broad particle-size distribution. Increasing the number of passes through the Microfluidizer, increasing the pressure, or reducing the phospholipid concentration all resulted in a smaller average liposome diameter. Changing these variables did not have a significant effect on the polydispersity of the dispersion. Electron microscopy showed that the dispersions formed had a range of structures, including unilamellar, multilamellar, and multivesicular liposomes. The composition of the MFGM phospholipid material is different from that of the phospholipids usually used for liposome production in the pharmaceutical and cosmetic industries. The MFGM-derived fraction comprises approximately 25% sphingomyelin, and the fatty acids are primarily saturated and monounsaturated. These differences are likely to affect the properties of the liposomes produced from the phospholipid material, and it may be possible to exploit the unique composition of the MFGM phospholipid fraction in the delivery of bioactive ingredients in functional foods.     

马鲁拉油与6种植物油理化性质、脂肪酸组成、营养物质比较

比较了马鲁拉油和6种常见植物油(橄榄油、花生油、玉米油、葵花籽油、紫苏籽油、亚麻籽油)的脂肪酸组成、理化性质及角鲨烯、维生素E和β-谷甾醇等营养物质含量的差异。结果表明:马鲁拉种仁出油率高达51.93%;马鲁拉油中角鲨烯和β-谷甾醇含量分别为2.5 mg/100 g和183.5 mg/100 g;马鲁拉油中的油酸含量高达76.94%,橄榄油中油酸含量为67.39%;与常见植物油相比,马鲁拉油富含单不饱和脂肪酸,脂肪酸比例均衡,且富含营养物质,适于人体的吸收,具有开发应用的潜力。     

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。     

Hot topic: Enhancing omega-3 fatty acids in milk fat of dairy cows by using stearidonic acid-enriched soybean oil from genetically modified soybeans

Very long chain n-3 fatty acids such as eicosapentaenoic acid (EPA; 20:5n-3) are important in human cardiac health and the prevention of chronic diseases, but food sources are limited. Stearidonic acid (SDA; 18:4n-3) is an n-3 fatty acid that humans are able to convert to EPA. In utilizing SDA-enhanced soybean oil (SBO) derived from genetically modified soybeans, our objectives were to examine the potential to increase the n-3 fatty acid content of milk fat and to determine the efficiency of SDA uptake from the digestive tract and transfer to milk fat. Three multiparous, rumen-fistulated Holstein cows were assigned randomly in a 3 × 3 Latin square design to the following treatments: 1) control (no oil infusion); 2) abomasal infusion of SDA-enhanced SBO (SDA-abo); and 3) ruminal infusion of SDA-enhanced SBO (SDA-rum). The SDA-enhanced SBO contained 27.1% SDA, 10.4% α-linolenic acid, and 7.2% γ-linolenic acid. Oil infusions provided 57 g/d of SDA with equal amounts of oil infused into either the rumen or abomasum at 6-h intervals over a 7-d infusion period. Cow numbers were limited and no treatment differences were detected for DMI or milk production (22.9 ± 0.5 kg/d and 32.3 ± 0.9 kg/d, respectively; least squares means ± SE), milk protein percentage and yield (3.24 ± 0.04% and 1.03 ± 0.02 kg/d), or lactose percentage and yield (4.88 ± 0.05% and 1.55 ± 0.05 kg/d). Treatment also had no effect on milk fat yield (1.36 ± 0.03 kg/d), but milk fat percentage was lower for the SDA-rum treatment (4.04 ± 0.04% vs. 4.30 ± 0.04% for control and 4.41 ± 0.05% for SDA-abo). The SDA-abo treatment increased n-3 fatty acids to 3.9% of total milk fatty acids, a value more than 5-fold greater than that for the control. Expressed as a percentage of total milk fatty acids, values (least squares means ± SE) for the SDA-abo treatment were 1.55 ± 0.03% for α-linolenic acid (18:3n-3), 1.86 ± 0.02 for SDA, 0.23 ± <0.01 for eicosatetraenoic acid (20:4n-3), and 0.18 ± 0.01 for EPA. Transfer efficiency of SDA to milk fat represented 39.3% (range = 36.8 to 41.9%) of the abomasally infused SDA and 47.3% (range = 45.0 to 49.6%) when the n-3 fatty acids downstream from SDA were included. In contrast, transfer of ruminally infused SDA to milk fat averaged only 1.7% (range = 1.3 to 2.1%), indicating extensive rumen biohydrogenation. Overall, results demonstrate the potential to use SDA-enhanced SBO from genetically modified soybeans combined with proper ruminal protection to achieve impressive increases in the milk fat content of SDA and other n-3 fatty acids that are beneficial for human health.     

基于气相色谱的植物油特征脂肪酸高温热氧化特性研究

利用自制高温热氧化装置和气相色谱法分别测定棕榈酸、油酸、亚油酸、亚麻酸在不同温度下的氧化降解曲线,同时采用微分法对热氧化降解反应动力学方程的参数(氧化活化能Ea,反应级数n,反应速率常数k,指前因子A)进行了计算,进而确定了反映棕榈酸、油酸、亚油酸、亚麻酸在高温下热氧化降解历程的宏观反应动力学模型。结果表明:棕榈酸热氧化降解反应动力学模型为r_A=-dcA/dt=9. 292×10~(66)exp(-648. 492/RT) c_A~(6. 504);油酸热氧化降解反应动力学模型为r_A=-dc_A/dt=3. 213×10~(59)exp(-548. 724/RT) c_A~(5.201);亚油酸热氧化降解反应动力学模型为r_A=-dc_A/dt=2. 865×10~(57)exp(-515. 468/RT) c_A~(3.220);亚麻酸热氧化降解反应动力学模型为r_A=-dc_A/dt=4. 451×10~(39)exp(-350. 851/RT) c_A~(2.108)。4种脂肪酸的动力学方程分别反映了其化学反应速率与反应温度和底物浓度的关系,同时揭示出不同脂肪酸热氧化的特性:随着不饱和度的升高,脂肪酸的热氧化稳定性降低;不饱和度越高,脂肪酸热氧化受自身浓度的影响越小;不饱和度越高,温度对其反应速率的影响越大。     

Technical note: Estimation of milk fatty acid yield from milk fat data

Most publications reporting milk fatty acid (FA) yields estimate these yields from milk fat yields and a coefficient estimating the proportion of FA in milk fat. The most widely used coefficient is, in fact, the proportion of fatty acyl radicals (i.e., FA from which the OH group has been removed) in milk triglycerides, equivalent to a mean proportion of 88% FA in milk fat. From a metabolic point of view, because the digestive flows and mammary FA uptake consist of nonesterified FA, it is more logical to estimate the FA proportion rather than the fatty acyl proportion in milk fat. From 588 milk FA profiles, we estimated a mean proportion of 94.4% FA in milk triglycerides. Moreover, when the other milk lipid classes (phospholipids, diglycerides, etc.) were taken into account, the proportion of FA in milk total lipids was estimated at 93.3%, almost independently of the milk FA profile. The use of this coefficient to estimate the secretion of milk FA on the basis of milk fat yield data is more physiologically relevant for milk FA secretion studies.     

n‐3 Omega fatty acids: a review of current knowledge

The very long chain polyunsaturated fatty acids (PUFAs) (C18–C22) and n‐3 Omega PUFAs are apparently widely accepted as a part of modern nutrition because of their beneficial effects on metabolism. Most significantly, the reported protective effect of the n‐3 omega fatty acids in relation to cardiovascular inflammatory diseases and cancer has led people to consider these fatty acids more beneficial than other dietary supplements. Unfortunately, there is a lack of studies relating to the physical performance increasing effect in sports diets, cholesterol‐reducing effect in meat technology, effects on human serum profile, the application dose and the side effects with/without omega‐6 PUFAs, which has left us with several crucial unanswered questions. We still do not know the correct dose of n‐3 omega and the correct ratio of n‐3 omega to n‐6 omega or their possible contraindications when combined with drugs, other foods and herbal supplements. Another reported aspect of n‐3 omega PUFAs is that they protect and even enhance the effect in medical treatment of important diseases such as Alzheimer’s, multiple sclerosis and cancer. These reports led to PUFAs becoming one of the most accepted and consumed food supplements. Despite this weight of evidence and the considerable current use, there is still a need for studies, which will determine whether the n‐3 omega fatty acids are in fact important functional supplements with no adverse effects. This review will attempt to outline the current position of n‐3 omega fatty acids in the field of clinical nutrition and healthcare and outline the studies needed to determine whether there are significant advantages in taking them as food supplement without any adverse effects.     

The oxidative stability of omega-3 oil-in-water nanoemulsion systems suitable for functional food enrichment: A systematic review of the literature

There is growing demand for functional food products enriched with long chain omega-3 polyunsaturated fatty acids (LCω3PUFA). Nanoemulsions, systems with extremely small droplet sizes have been shown to increase LCω3PUFA bioavailability. However, nanoemulsion creation and processing methods may impact on the oxidative stability of these systems. The present systematic review collates information from studies that evaluated the oxidative stability of LCω3PUFA nanoemulsions suitable for use in functional foods. The systematic search identified seventeen articles published during the last 10 years. Researchers used a range of surfactants and antioxidants to create systems which were evaluated from 7 to 100 days of storage.

Nanoemulsions were created using synthetic and natural emulsifiers, with natural sources offering equivalent or increased oxidative stability compared to synthetic sources, which is useful as consumers are demanding natural, cleaner label food products. Equivalent vegetarian sources of LCω3PUFA found in fish oils such as algal oils are promising as they provide direct sources without the need for conversion in the human metabolic pathway. Quillaja saponin is a promising natural emulsifier that can produce nanoemulsion systems with equivalent/increased oxidative stability in comparison to other emulsifiers. Further studies to evaluate the oxidative stability of quillaja saponin nanoemulsions combined with algal sources of LCω3PUFA are warranted.     

Validation of a rapid milk fat separation method to determine the fatty acid profile by gas chromatography

An improved rapid method for separating lipids from milk to determine the fatty acid composition using 2 centrifugations at room temperature (20°C) was compared with the ISO-IDF reference procedure based on solvent extraction. The new method is useful for research and routine quality control and has a number of advantages over the reference procedure—mainly no solvents are required and it saves time. Applicability of the rapid separation method was confirmed in fats with different physical characteristics from ewe and goat milk samples. Minor differences were found in the proportions of some fatty acids in the reference and centrifugation methods. Milk fat separated by centrifugation at room temperature did not differ in fatty acid composition from milk centrifuged at 4°C.