紫外光谱法测定芝麻素与芝麻林素含量

本实验采用紫外分光光度法测定芝麻油中木酚素类物质芝麻素与芝麻林素的含量.根据木酚素类化合物在200～400nm紫外区有特征吸收,利用其吸收的强弱,以芝麻油中含量最高的芝麻素为对照品,通过标准曲线的绘制和假设检验,得到芝麻素的浓度与吸光度之间的显著的线性关系,由回归方程计算芝麻素的最低检测极限为1.95μg/mL,平均加样回收率为99.31%,RSD为1.87%;在提取后的40分钟内进行稳定性试验,RSD（%）为0.3%.重现性试验结果RSD为2.85%,精密度试验结果RSD为0.22%.     

Natural antimicrobial/antioxidant agents in meat and poultry products as well as fruits and vegetables: A review

Synthetic preservatives are widely used by the food industry to control the growth of spoilage and pathogenic microorganisms and to inhibit the process of lipid oxidation extending the shelf-life, quality and safety of food products. However, consumer's preference for natural food additives and concern regarding the safety of synthetic preservatives prompted the food industry to look for natural alternatives. Natural antimicrobials, including plant extracts and their essential oils, enzymes, peptides, bacteriocins, bacteriophages, and fermented ingredients have all been shown to have the potential for use as alternatives to chemical antimicrobials. Some spices, herbs and other plant extracts were also reported to be strong antioxidants. The antimicrobial/antioxidant activities of some plant extracts and/or their essential oils are mainly due to the presence of some major bioactive compounds, including phenolic acids, terpenes, aldehydes, and flavonoids. The proposed mechanisms of action of these natural preservatives are reported. An overview of the research done on the direct incorporation of natural preservatives agents into meat and poultry products as well as fruit and vegetables to extend their shelf-life is presented. The development of edible packaging materials containing natural preservatives is growing and their applications in selected food products are also presented in this review.     

Utility of 4-chloro-7-nitrobenzofurazan for the spectrofluorimetric determination of butylated hydroxyanisole and propyl gallate in foodstuffs

Abstract: A spectrofluorimetric method is presented for the determination of 2 synthetic phenolic antioxidants (SPAs), butylated hydroxyanisole (BHA), and propyl gallate (PG) in foodstuffs. The proposed method is based on the derivatization of SPAs with 4‐chloro‐7‐nitrobenzofurazan (NBD‐Cl) in phosphate buffer of pH 9.0 to yield a highly fluorescent brown product. The optimum experimental conditions have been studied carefully. Linear calibration curves were obtained over the concentration range of 0.20 to 40 μg mL^?1 for BHA, and 0.80 to 50 μg mL^?1 for PG, using NBD‐Cl reagent. The detection limits were 18 ng mL^?1 for BHA, 55 ng mL^?1 for PG. Intra‐day and inter‐day relative standard deviations at 3 different concentrations were determined. The high recovery values indicate the accuracy of the proposed methods, and low relative standard deviation values indicate good precision. The results presented in this report show that the applied spectrofluorimetric method is acceptable for the determination of the 2 SPAs in the foodstuffs. Other SPAs, tertiary butyl hydroquinone and butylated hydroxytoluene in foodstuffs do not interfere with the proposed method. Practical Applications: In this spectrofluorimetric method, NBD‐Cl as a derivation agent is used to detect synthetic phenolic antioxidants. The method specificity has been greatly improved; there was no interference from other commonly used phenolic substances.     

岩藻黄素在水、油模型体系中稳定性的研究

研究了温度、抗氧化剂及气体环境对水、油模型体系中岩藻黄素稳定性的影响,并对岩藻黄素的降解动力学进行分析。结果表明,不同贮藏条件下岩藻黄素在油体系中比在水体系中表现出更强的耐贮藏性;岩藻黄素在低温贮藏下相对稳定,随温度升高,降解加快;水溶性抗氧化剂抑制降解效果从高到低依次为:植酸钠>茶多酚>维生素C;脂溶性抗氧化剂抑制降解效果从高到低依次为:特丁基对苯二酚>丁基羟基茴香醚>维生素E>二丁基羟基甲苯>没食子酸丙酯。不同气体贮藏环境实验表明,两种体系中氮气能够抑制岩藻黄素降解,而氧气促进岩藻黄素降解。降解动力学分析结果表明,上述不同条件下岩藻黄素的降解遵循一级反应动力学模型。      

纳米银-聚乙烯复合包装中银对2 种抗氧化剂向食品模拟物迁移的影响

探究纳米银-聚乙烯复合包装中纳米银成分的存在对2 种抗氧化剂（Irganox1076和Irgafos168）向食品模拟物迁移规律的影响。将含有抗氧化剂的聚乙烯包装膜和同时含有抗氧化剂与纳米银的复合包装膜裁成正方形若干,分别浸泡于正己烷和体积分数95%乙醇溶液2 种食品模拟物中,密封后在20、40 ℃以及70 ℃条件下进行迁移实验。食品模拟物中2 种抗氧化剂的加标回收率在79.3%～108.0%之间,相对标准偏差在0.7%～5.3%之间。2 种抗氧化剂的迁移会随着迁移温度的升高以及迁移时间的延长而增加直至达到迁移平衡,且其在正己烷模拟物中的迁移量大于在体积分数95%乙醇模拟物中的迁移量;含纳米银聚乙烯塑料比不含纳米银聚乙烯塑料中的抗氧化剂向食品模拟物中的迁移量小,表明纳米银成分的存在可以抑制包装中的抗氧化剂向食品模拟物中的迁移。     

柑橘在体外模拟胃肠消化过程中总多酚、总黄酮及总抗氧化活性的变化规律

通过体外模拟胃肠消化法模拟柑橘在胃肠道的消化过程,测定模拟胃肠消化过程中总多酚、总黄酮的释放量及总抗氧化活性的变化规律。结果显示,柑橘多酚主要是游离酚,有机化学提取法释放的多酚高于模拟胃肠消化法。模拟胃消化3 h后,与消化0 h相比,宽皮柑、脐橙和金橘的多酚最大释放量是其1.02、0.93、1.21 倍,黄酮最大释放量是其1.46、2.37、2.16 倍,最大抗氧化活性是其1.10、1.23、1.62 倍。体外模拟肠消化4 h后,与胃消化0 h和肠消化0 h相比,宽皮柑、脐橙和金橘的多酚释放量分别为其0.99、0.80、1.29 倍和91%、81%、90%,黄酮的最大释放量分别为其73%、39%、64%和51%、17%、39%,最大抗氧化活性分别为其1.67、1.09、1.76 倍和1.31、0.88、1.22 倍。这表明柑橘在模拟胃肠消化过程中,胃蛋白酶、胰酶、胆汁及胃酸均可以促进抗氧化活性物质释放。     

Role of fermentative and antioxidant metabolisms in the induction of core browning in controlled‐atmosphere stored pears

Pears (Pyrus communis L cv Blanquilla) were stored at various CO₂ concentrations to induce core browning. The severity of core browning and the products and enzymes associated with fermentative and antioxidant metabolisms were determined immediately after harvest and in healthy and damaged fruits after storage. The incidence and severity of brown core increased with CO₂ concentration. Acetaldehyde and ethanol concentrations and alcohol dehydrogenase (ADH, EC 1.1.1.1) activity increased in all fruits during storage, but more in fruits with brown core than in healthy fruits. Pyruvate decarboxylase (PDC, EC 4.1.1.1) activity decreased slightly during this time. Ascorbate contents decreased whereas glutathione concentrations increased during storage in fruits with brown core compared to the same fruits at harvest. Superoxide dismutase (SOD, EC 1.15.11) activity increased during storage but was not affected by brown core. In contrast, a significant increase in both ascorbate peroxidase (APX, EC 1.11.1.11) and glutathione reductase (GR, EC 1.6.4.2) activities and a significant decrease in catalase (CAT, EC 1.11.1.6) activity were found in damaged fruits. Malonaldehyde (MDA) and 4‐hydroxyalkenal (4‐HNE) contents increased significantly in the damaged fruits as a result of peroxidation. Collectively, our results suggest that brown core in pears is indirectly correlated with fermentation and involves oxidative damage which may be a causal factor in brown core development. © 2001 Society of Chemical Industry     

Catecholoximes as powerful antioxidants for highly unsaturated lipids

Several oximes and oximeethers of hydroxylated benzaldehydes and acetophenones were investigated for their antioxidative potential and compared with further standards. Radical scavenging activity was determined using a photometric assay based on the colored radical 2, 2‐diphenyl‐1‐picrylhydrazyl and a superoxide anion quenching assay using luminol amplified chemiluminescence. The activity against lipid autoxidation was measured by accelerated autoxidation of soybean oil, evening primrose oil, and squalene. All tested catecholoximes show good to excellent antioxidative properties. 3, 4‐Dihydroxybenzaldoxime shows the best overall performance and is a very powerful radical scavenger and lipid antioxidant.     

Flavonoids quercetin,myricetin, kaemferol and (+)‐catechin as antioxidants in methyl linoleate

The antioxidant effect of the flavonoids quercetin, myricetin, kaemferol, (+)‐catechin and rutin on methyl linoleate oxidation was investigated. In addition, the synergistic effects of flavonoids and α‐tocopherol were studied. Oxidation was monitored by conjugated diene measurement and by determining the formation of hydroperoxide isomers by HPLC. The antioxidant activity of flavonoids in non‐polar methyl linoleate differ from that previously reported in water‐containing systems, such as LDL and liposome systems. The activity of antioxidants (10–1000 μM ) measured by hydroperoxide formation decreased in the order: myricetin>quercetin>α‐tocopherol>(+)‐catechin >kaemferol=rutin. The antioxidant activity of flavonoids increased as the number of phenolic hydroxyl groups increased. In addition to the number of hydroxyl groups, other structural features such as the 2,3 double bond in the C‐ring and a glycoside moiety in the molecule had an effect on the antioxidant activity. Myricetin and rutin, especially had a synergistic effect with α‐tocopherol. Myricetin, quercetin and rutin protected α‐tocopherol from decomposition, myricetin being the most protective. The relative hydrogen‐donating activity measured by the ratio of cis,trans‐ to trans,transhydroperoxide isomers formed during oxidation decreased in the order: α‐tocopherol >myricetin>quercetin. Hydroperoxide isomeric distribution of the samples containing kaemferol or rutin did not differ from the control. Thus, although α‐tocopherol was the most effective hydrogendonor, myricetin and quercetin were more effective antioxidants in inhibiting the hydroperoxide formation in methyl linoleate. © 1999 Society of Chemical Industry     

Oxidative stability of potato chips: effect of frying oil type,temperature and antioxidants

The effect of type of frying oil and temperature on the oxidative stability of potato chips during storage was studied. Cottonseed oil, soybean oil, olive kernel oil and palmolein were used as frying media. The chips were packaged in metallized cellophane bags and incubated at 63 °C. At definite time intervals the absorbed oil was extracted and analyzed for peroxide value, Totox number and conjugated diene content. Olive kernel oil and palmolein absorbed into the chips showed better stability, whereas soybean oil presented the higher oxidation rate. Frying temperature (170, 180 or 190 °C) did not affect the oxidation rate during storage, with the exception of conjugated diene formation which was greater for chips fried at 190 °C. Ground oregano or oregano extract, obtained by petroleum ether extraction, were added to the chips as antioxidants. Both retarded significantly the oxidation rate of the oil absorbed into the chips, with results comparable to tertiary butylhydroquinone (TBHQ) during storage at 63 °C for 7 days; however TBHQ proved significantly more effective after that time. © 1999 Society of Chemical Industry