Roasting affects phenolic composition and antioxidative activity of hazelnuts (Corylus avellana L.)

The potential effect of skin removal and roasting on individual and total phenolic content, and on antioxidative potential of 6 hazelnut cultivars were investigated. HPLC-MS identification of individual phenolics confirmed the presence of 7 flavan-3-ols (catechin, epicatechin, 2 procyanidin dimers, and 3 procyanidin trimers), 3 flavonols (quercetin pentoside, quercetin-3-O-rhamnoside, and myricetin-3-O-rhamnoside), 2 hydrobenzoic acids (gallic acid, protocatechulic acid), and 1 dihydrochalcone (phloretin-2'-O-glucoside). Flavonols were only detected in whole hazelnut kernels. The content of individual phenolics, with the exception of gallic acid, was always highest in whole unroasted hazelnuts and was significantly reduced after skin removal. Similarly, total phenolic content and antioxidative potential decreased when skin was removed. Roasting had a significant negative effect on individual phenolics but not on the total phenolic content and antioxidative potential of kernels. From a health promoting phytochemical composition of hazelnuts the consumption of whole unroasted kernels with skins should be preferential to peeled kernels either roasted or unroasted. Practical Application: A significant reduction in the antioxidative potential and total phenolic content is detected after hazelnut skin removal but not after roasting, suggesting that hazelnut kernels should be consumed whole. In hazelnut skin, many phenolic compounds are located, which are not present in flesh and, therefore, the health properties of hazelnuts are strongly affected by skin removal. Thermal processing and roasting conditions used in this study had a lesser effect on the individual phenolic composition of the kernel and thus roasted and unroasted hazelnuts without skin contain comparable amounts of health promoting compounds.     

Nut and kernel traits and chemical composition of hazelnut (Corylus avellana L.) cultivars

BACKGROUND: Nut and kernel traits and chemical composition of 24 Italian and foreign hazelnut cultivars were analysed in 2002–2004 in order to study the effect of genotype and environment on nut quality. Nuts were sampled in a germplasm collection in the Italian province of Viterbo. RESULTS: Quantitative and qualitative determinations of sugars, organic acids and lipids revealed good nutritional and health potential of the nuts, with several differences among cultivars and years. The total contents of oil and sugars ranged from 563.69 to 656.36 g kg^?1 dry weight (DW) and from 39.80 to 59.51 g kg^?1 DW respectively. Fatty acid profile and sugar and total phenolic contents varied with the year. Significantly higher palmitic acid concentration (6.18%) was found in the hot summer year 2003; lower saturated fatty acid concentration (8.20%) and higher unsaturated/saturated acid ratio (11.27) were observed in the coolest year (2004). These differences among years were highlighted by discriminant analysis. CONCLUSION: The information relating to secondary components such as sugars, organic acids and phenolics was useful for discriminating among cultivars and years. Owing to the effect of these compounds on sensory attributes perceived by consumers, their concentration and the varietal differences can be considered primary determinants of nut quality and should be valued when planning the cultivar choice for new plantations. Copyright © 2008 Society of Chemical Industry     

California almond shelf life: lipid deterioration during storage

The effects of storage conditions on the lipid deterioration in California almond nuts and sliced were studied. Natural whole almonds with or without polyethylene (PE) packaging and blanched whole almonds and sliced with PE packaging were stored in 10 different storage conditions which were combinations of different temperatures and relative humidity levels. The peroxide values (PVs), iodine values (IVs), and free fatty acids (FFAs) were monitored during the storage. The PVs in the natural samples did not change noticeably whereas the blanched samples changed greatly, indicating that skins may have played a significant role. The IVs decreased slightly in the 1st 150 d of storage and then leveled off. The slightly faster changes in IVs in the blanched samples coincided with the greater changes in PVs in the blanched samples. The natural samples exhibited much higher FFA levels than the blanched samples after storage. In general, FFA increased with increasing storage time, temperature, and humidity. Highest levels of FFA were observed in the samples stored at high temperature and high humidity. PRACTICAL APPLICATION: The results reported in this article provide useful information that almond producers and processors could use to develop their storage and transport processes.     

Fatty acid and glyceride composition of Astrocaryum vulgare kernel fat

The kernel composition, lipid classes, fatty acid composition, fatty acid distribution on triglycerides and triglyceride composition of kernel fat from Astrocaryum vulgare Mart palms grown in Nigeria have been studied. Kernels had a high fat content. Lauric acid was the predominant fatty acid in the whole fat and was also the major fatty acid in the triglycerides and in the 2-monoglycerides derived from them by pancreatic lipase hydrolysis. All the fatty acids exhibited a preference for the 1-and-3, positions of triglycerides, except for lauric which showed a preference for the 2-position and oleic which exhibited a random distribution. The trisaturated triglycerides were the predominant triglyceride type and the fatty acid composition of the various triglycerides suggested an absence of completely unsaturated triglycerides.     

不同部位冷却猪肉中脂肪酸组成与脂肪氧化的变化

研究英系大白阉公猪后腿肉、里脊肉和五花肉3个部位中肌间脂肪和皮下脂肪含量,并对其脂肪酸组成进行了分析,同时研究了腿肉在(4±0.5)℃避光贮存条件下脂肪氧化程度的变化,及其与脂肪酸组成的关系。结果表明,不同部位猪肉肌间和皮下脂肪酸组成均没有显著性差异(p>0.05);在(4±0.5)℃避光贮存期间(0～5d),肌间脂肪氧化程度显著高于皮下脂肪氧化程度(p<0.05),随着贮存时间的延长,到第5天时,后腿肉肌间脂肪TBA值已达到0.5mg/kg,其它部位肌间脂肪TBA值亦接近0.5mg/kg,而各部位皮下脂肪TBA值均在0.2mg/kg以下。一般来讲,当生肉的TBA值超过0.5mg/kg时,人就能感觉到有氧化异味。因此,控制肌间脂肪氧化是保证冷却肉良好品质的关键。     

Development of lipid oxidation during manufacturing of horse mackerel surimi

When fatty fish are transformed into surimi, lipid oxidation takes place, decreasing the quality of the product. This study was aimed to identify the critical stages of the process in terms of the development of lipid oxidation. Horse mackerels were transformed into surimi on a pilot line and samples taken (hand‐skinned fillets = minced fillets, mince, washed and refined minces, paste, surimi and washing water). Most of the lipids were removed during the process and neutral lipids were lost in higher proportion than polar lipids. As a consequence, total lipids of surimi contained more polyunsaturated fatty acids (338 ± 19 g kg^?1) than total lipids of the minced fillets (220 ± 8 g kg^?1). Thiobarbituric acid reactive substances (TBARS) was higher in the minced fillets than in the mince because less subcutaneous fat and dark muscle were removed during hand‐mincing, indicating that the settings of the skinning–deboning machine can strongly influence the final quality of the product. Concentrations of lipid oxidation products increased significantly during the next stages of surimi processing. The increase was more pronounced for TBARS than hydroperoxides. Concentrations in hydroperoxides were similar in mince and washed mince (15.3 ± 2.8 and 16.6 ± 2.8 mmoles kg^?1 lipid) and increased in refined mince (29.6 ± 2.8 mmoles kg^?1 lipid). TBARS accounted for 2.7 ± 1.0 mg kg^?1 lipid in mince, 40.4 ± 2.3 mg kg^?1 lipid in washed mince and 237 ± 7 mg kg^?1 lipid in refined mince. Hydroperoxides and TBARS were found in appreciable amounts in washing water (76.9 ± 4.7 mmoles kg^?1 lipid and 479 ± 8 mg kg^?1 lipid respectively), when they decreased in surimi (27.3 ± 3.8 mmoles kg^?1 lipid and 44.2 ± 0.8 mg kg^?1 lipid respectively) compared with refined mince. This shows that the last dewatering stage is crucial to ensure surimi quality. Copyright © 2005 Society of Chemical Industry     

Total lipid,fatty acid composition and lipid oxidation of Indian white shrimp (Fenneropenaeus indicus) fed diets containing different lipid sources

BACKGROUND: Seafood is an important constituent of the human diet. In Iran, Indian white shrimp (Fenneropenaeus indicus) is the major cultured shrimp species as a result of market demand, local availability and growth rate. It is mainly reared using commercial feed. The purpose of this study was to evaluate the effects of replacing 50% of the fish oil by vegetable oils in shrimp feed on total lipid, fatty acid composition and lipid oxidation of shrimp muscle. RESULTS: No significant differences in total lipid content (6.1–7.3 g kg^?1) were found between edible tissues of shrimp fed different diets. The major fatty acids in shrimp muscle were palmitic, oleic, lionoleic, stearic, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. Higher levels of EPA and DHA were observed in muscle of shrimp fed a diet containing fish oil. Oxidative rancidity, measured as thiobarbituric acid reactive substances, for all shrimps did not exceed 0.2 mg malonaldehyde kg^?1 muscle tissue, which was low and acceptable. CONCLUSION: This study had shown that the fatty acid composition of feed directly affects the fatty acid composition of Indian white shrimp muscle. Farmed Indian white shrimp can be considered as a species of low fat and shrimp muscle was quite stable to oxidation during storage. Copyright © 2009 Society of Chemical Industry     

泡酒肥肉浸制过程中脂肪氧化和脂肪酸组成的变化

泡酒肥肉是豉香型白酒(玉冰烧)生产过程\     

Technical note: a rapid lipid separation method for determining fatty acid composition of milk

A rapid method for milk lipid separation followed by transmethylation to produce fatty acid methyl esters from bovine milk samples is presented. Fat is separated by a nonsolvent method using centrifugation. The method was compared with the popular hexane:isopropanol solvent extraction method, and fatty acid proportions were statistically identical for both methods. In 108 replicates, variance accounted for by using the 2 methods was of a similar magnitude to variance due to repeat separations or repeat injections onto the gas chromatography column. It is concluded that the proposed method is accurate, simple, rapid, safe, economical, and especially suitable for large numbers of samples.     

Control of lipid oxidation in extruded salmon jerky snacks

A shelf-life study was conducted to evaluate the effect of antioxidants on oxidative stability of extruded jerky-style salmon snacks. Deterioration of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) due to lipid oxidation is a major concern for this healthy snack. A control jerky with no added antioxidants and 4 jerkies with antioxidants (rosemary, mixed tocopherols, tertiary butylhydroquinone, and ascorbyl palmitate) added as 0.02% of the lipid content were extruded in duplicate in a Coperion ZSK-25 twin screw extruder. Salmon jerkies from each formulation were placed in 3 mil barrier pouches, flushed with nitrogen, and stored at 35 °C and 75% relative humidity. Lipid oxidation was evaluated as by peroxide value and malonaldehyde content. Other chemical analyses included total fatty acid composition, lipid content, moisture, water activity, pH, and salt. Astaxanthin and CIE L*, a*, b* color were also analyzed at 4-wk intervals. Rosemary inhibited peroxide formation better than did other antioxidants at week 8; no treatment inhibited malonaldehyde levels. All jerkies had lower astaxanthin levels after 8 wk, but rosemary-treated jerky had higher pigment concentrations than did the control at weeks 4 and 8. Protection of omega-3 lipids in these extruded jerkies must be improved to offer consumers a convenient source of these healthful lipids. Practical Application: Salmon flesh can be extruded to produce a jerky that provides 410 mg of omega-3 lipids per serving. Natural antioxidants such as rosemary should be added at levels over 0.02% of the lipid content to help control lipid oxidation. Astaxanthin and CIE a* values correlated well with lipid stability and could be used to monitor quality during storage if initial values are known.     

热处理对核桃仁脂氧化酶类活性的影响

为研究微波、远红外和热风3种处理对核桃仁脂氧化酶类活性的影响,以核桃仁为原料,采用不同强度的微波、远红外和热风对核桃仁进行热处理,测定核桃仁脂氧合酶(LOX)、过氧化物酶(POD)和过氧化氢酶(CAT)活性变化。结果表明:微波、远红外和热风3种处理均能够有效地降低核桃仁LOX、POD和CAT活性。3种热处理最优条件分别为:微波385 W处理3min,远红外90℃处理30min和热风90℃处理90min,其中微波灭酶效果最好。     

焙烤工艺对核桃仁品质的影响

以‘温宿185’薄皮核桃为原料,以焙烤后核桃仁的酸值、过氧化值、总酚含量、色泽为指标,并结合模糊数学综合评价法研究焙烤温度、焙烤时间对脱皮与未脱皮核桃仁品质的影响。结果表明:120~140℃、焙烤10~30 min核桃仁的过氧化值和酸值较低;120~150℃条件下随焙烤时间的延长,未脱皮核桃仁与脱皮核桃仁的酸值(KOH)分别在150℃/30 min和150℃/25 min达到最高点,与120℃/10 min相比酸值(KOH)分别上升了0.303、0.107 mg/g;随焙烤温度的升高,核桃仁色泽加深,总酚含量变化不显著,但酚类物质的浸泡液对核桃仁的品质有显著影响;通过模糊数学感官评价法得出核桃仁的最佳焙烤条件为焙烤温度130℃、焙烤时间25 min,在此条件下核桃仁的综合得分为94.10分。焙烤不仅赋予了核桃仁独特的风味,还进一步提升了核桃仁加工制品的品质。     

改性脂质的阴离子交换树脂脱酸工艺研究

以高酸值改性脂质为目标油脂,研究了2种阴离子交换树脂对高酸值改性脂质进行脱酸精制的可行性,并将其与液-液萃取脱酸法联合,以简化液-液萃取脱酸的工艺流程及减少溶剂消耗量。通过单因素实验初步优化了改性脂质的阴离子交换树脂脱酸工艺参数:脱酸温度30℃;反应时间5h;树脂/改性脂质的质量比为2:1;改性脂质/正己烷溶液的浓度为0.2g/mL。改性脂质经液-液萃取联合阴离子交换树脂脱酸后,其罗维朋色度及脂肪酸组成较之未脱酸前没有显著的变化。      

Potato starch edible films to control oxidative rancidity of polyunsaturated lipids: effects of film composition, thickness and water activity

The objective of this work was to study the effect of potato starch-based films acting as oxygen barrier on the oxidative rancidity of vegetable oil, as an example of a food rich in polyunsaturated fatty acids. The effect of glycerol (Gly) content (0%, 10%, 20%, 30%), film thickness (30, 60, 100 μm) as well as environmental relative humidity (RH) (50% or 75%) were analysed. Results obtained confirmed that potato starch films delayed the rancidity in vegetable oil. Films without Gly provided the same protection as films with 10% Gly. Films with higher Gly content were not as effective oxygen barrier. It is likely that the fact that film protective capability diminished with increased RH or Gly content was due to the increasing moisture content of the films. Despite that fact, potato starch films can be considered a very efficient oxygen barrier even at RH as high as 75%.     

不饱和脂肪酸的氧化机理研究

本文主要研究了天然油脂衍生物脂肪酸-油酸，十八碳混合烯酸，芥酸，花烯酸的氧化及其机理，着重考查了这几种脂肪权在深度氧化条件下，其脂肪链结构对PV变化的影响；实验证明：脂肪酸可以深度氧化，天然油脂中的游离脂肪酸对氧化不存在明显的影响。有利于油脂的技术开发。     

冬枣核油的营养成分和抗氧化能力分析

对冬枣核油的脂肪酸组成和营养成分进行分析,并测定了其中极性成分与非极性成分的抗氧化能力。结果表明:冬枣核油含有11种脂肪酸,不饱和脂肪酸含量为74. 79%,其中油酸与亚油酸的含量较均衡,分别为39. 34%和33. 74%;冬枣核油中含有14种不皂化物,其中含有在普通植物油中不常见的γ-谷甾醇,占总不皂化物的53. 11%;冬枣核油中共检出3种生育酚和2种生育三烯酚,其中γ-生育酚含量(106. 34 mg/kg)最高,其次为α-生育酚(31. 48 mg/kg);冬枣核油中非极性成分抗氧化能力高于极性成分,其清除DPPH自由基和ABTS自由基的能力分别为114. 95mgTE/kg和207. 8 mgTE/kg。     

新疆南疆扁桃仁中蛋白质与脂类营养分析

为客观分析评价新疆南疆扁桃仁中蛋白质和脂类营养特性,以新疆南疆主栽品种莎车1号、莎车9号和石头扁桃仁为研究对象,运用氨基酸自动分析仪和GC-MS对扁桃仁中氨基酸和油中脂肪酸组成及含量进行了分析测定。结果表明:莎车1号、莎车9号和石头扁桃仁中粗蛋白含量较高,分别为27.17%、29.15%和31.13%;氨基酸组成全面且含量丰富;粗脂肪含量丰富,分别为53.76%、50.64%、49.26%;油中不饱和脂肪酸含量较高,分别为93.78%、94.14%、93.38%。因此,新疆南疆扁桃是一种极具开发价值的高品质植物蛋白资源和油料作物。     

Lipophilic compounds and thermal behaviour of African mango (Irvingia gabonensis (Aubry-Lecomte ex. O'Rorke) Baill.) kernel fat

Irvingia gabonensis kernels are a promising oleiferous source. Their total lipid content was 72.3%. C14:0 and C12:0 represented the most abundant fatty acids. Triacylglycerols with ECN 32 and 46–48 were identified for the first time by HPLC-DAD-ESI-MSⁿ. Comprehensive GC-FID and GC-MS analyses revealed novel insights into minor lipids like phytosterols and tocochromanols. Among the latter, γ-tocopherol was found to be the major vitamer. β-Sitosterol and stigmasterol were the prevailing phytosterols in the kernel fat. The high saturation level of the fat resulted in a sharp differential scanning calorimetry melting curve with a high melting temperature of 42.1 °C. The fat remained solid over a wide temperature range and still contained 66.6% solid fats at 35 °C. Consequently, kernels of the African mango provide a viable source for the recovery of solid fats applicable in the food industry as sustainable alternatives to replace palm-based fats or hardened vegetable oils.