木糖-草鱼肽美拉德反应产物的抗氧化性

为了探讨美拉德反应对草鱼肽抗氧化性的影响,该文以分子量小于5 KDa的草鱼肽为原料,加入木糖进行美拉德反应,并与单独加热的样品进行比较。分别检测分析了不同反应时间的热降解产物和美拉德反应产物的还原力、氧自由基吸收能力(ORAC,oyxgen radical absorbance capacity)值及挥发性成分组成,并对反应产物中挥发性物质与其抗氧化活性之间的关系进行了探讨。试验结果表明:草鱼肽添加木糖反应比其单独加热的褐变程度更高,抗氧化性更强。且随着反应时间的延长,美拉德反应产物的抗氧化性能逐步增强,并产生了大量的呋喃、吡嗪等杂环化合物,通过相关性分析,发现美拉德反应产物的抗氧化性与上述挥发性组分含量显著相关(P0.95)。草鱼肽与木糖质量比为1∶1混合并在100℃下反应3 h具有较强抗氧化性。因此,美拉德反应修饰可使草鱼肽表现出更强的抗氧化性,是一种优秀的食品抗氧化原料。     

熟化枸杞子的加工工艺及功能特性

为了有效开发利用枸杞子资源,进一步提高枸杞子附加值,该文以新鲜枸杞子为原料,在传统干制工艺的基础上,基于美拉德反应原理,开发熟化枸杞子新产品,并对其活性进行检测。研究结果表明,熟化枸杞子三段式干制工艺为:干制预处理阶段温度为60℃,时间为12 h;熟化阶段温度为80℃,时间为24 h,相对湿度65%;定型阶段温度45℃,干制6 h即可。制备的熟化枸杞子为黑褐色、酸甜适口、抗氧化活性显著高于(P0.05)普通干制枸杞子,其总还原能力、羟自由基清除能力、DPPH自由基清除能力分别是普通干制枸杞子的1.87倍、1.45倍和2.21倍,是一种较好的抗氧化食品,枸杞子的附加值得到了有效提高,并且该熟化枸杞子的制备工艺简单、成果易转化,具有很好的应用前景。     

鲣鱼蒸煮液美拉德反应优化及氨基酸分析

为了制备风味良好的鲣鱼调味基料,本试验以鲣鱼蒸煮液(STCL)为原料,在酶解和脱腥基础上,采用感官评价、电子鼻技术结合主成分分析(PCA)及线性判别分析(LDA),通过正交试验优化美拉德工艺,并对鲣鱼蒸煮液酶解液美拉德产物进行氨基酸组成成分分析和必需氨基酸营养评价。结果表明,电子鼻技术结合LDA优于PCA,更能客观地区分不同条件下鲣鱼蒸煮液酶解液美拉德反应产物的风味差异;鲣鱼蒸煮液酶解液美拉德反应最优工艺条件为:添加木糖-葡萄糖1:2,在110℃下加热45 min,在此条件下,美拉德产物鱼香味浓郁,色泽呈黄棕色,氨基酸总量为7.036 g·100g^-1,必需氨基酸含量为2.888 g·100g^-1,必需氨基酸指数(EAAI)为64.034,说明鲣鱼蒸者液美拉德反应产物营养价值较高,是研发海鲜调味料的理想基料。本研究结果为鲣鱼调味基料的开发提供了一定的理论依据。     

利用电子自旋共振技术研究美拉德反应自由基变化

为寻求简便而准确地对食品加工和贮藏过程中的美拉德反应进行鉴定的方法,该文研究加热食品中葡萄糖和乳球蛋白建立的美拉德反应体系的自由基变化,主要考察影响美拉德反应的温度和pH值变化导致的自由基改变,从而确定美拉德反应与其自由基变化之间的相互关系。在3种不同温度、有无氧气和3种不同pH值条件下,利用电子自旋共振(electron spin resonance,ESR)光谱检测美拉德反应自由基变化趋势,结果随温度升高,自由基数量增加,反应速度加快;随pH值由酸性向碱性移动,自由基数量增加;自由基数量在无氧条件时多于有氧条件。当自由基积累到一定浓度,由于聚合反应生成高分子聚合物使信号强度下降,最后消失。比较美拉德产物与2种底物产生的自由基发现,无论类型、数量还是生成速率都存在明显差异。研究结果表明,采用自旋捕集剂对不稳定的自由基进行捕集来分析信号能够有效表征加热食品中美拉德反应初中期阶段的自由基变化,从而有效表征和分析美拉德反应过程。与传统研究美拉德反应的分析方法比较,ESR光谱是一种简便灵敏的分析方法,可以作为研究加热食品美拉德反应的重要方法之一。     

北京地区酱卤牛肉中挥发性风味物质剖面分析

为研究酱卤牛肉中挥发性风味物质的贡献程度,以北京地区老字号酱卤牛肉(稻香村、天福号、月盛斋、东来顺)为研究对象,探究各酱卤牛肉产品中风味物质的组成、质量浓度及整体贡献,并采用顶空固相微萃取-气相色谱-质谱联用技术对北京地区老字号酱卤牛肉中的挥发性风味成分进行定性定量分析。结果表明,4种酱卤牛肉产品中共鉴定出78种挥发性风味物质,其中气味活性物质(OAV ≥1)12种,分别为庚醛、壬醛、肉豆蔻醛、桉叶油醇、芳樟醇、(-)-4-萜品醇、L-α-松油醇、α-松油醇、草蒿脑、茴香脑、1-甲基萘、2-戊基呋喃,被确定为主体风味物质。因具有相对较高的OAV和特殊风味,壬醛、桉叶油醇、芳樟醇、草蒿脑、茴香脑被认定为北京地区老字号酱卤牛肉的特征风味物质,酮类、酯类和部分醇类为修饰风味物质。对12种气味活性物质进行主成分分析和聚类分析,发现不同酱卤牛肉的风味轮廓差异显著,可明确区分其整体风味情况;气味活性物质可聚为4类,其分别来源于原料肉中脂肪的氧化降解、美拉德反应,以及香辛料的添加等。本研究结果为酱卤牛肉产品的风味调控提供了理论参考。     

混菌发酵黑青稞甜醅工艺优化及品质特性研究

为改善单一菌株发酵制备青稞甜醅的风味与口感,提高其质量品质,本试验采用米根霉和酵母菌为发酵菌株,以氨基酸态氮含量及感官评分为指标,确定混菌发酵黑青稞甜醅的最佳工艺条件,并比较单一菌株发酵黑青稞制品与混菌发酵黑青稞制品中酚类物质含量、抗氧化活性及风味物质组成的差异。结果表明,混菌发酵黑青稞制品最佳发酵条件为:发酵温度33℃,发酵时间48 h,菌种比例(酵母菌J7∶米根霉)1∶1.20,接种量6.81%,在此条件下混菌发酵黑青稞制品的氨基酸态氮含量为9.32 mg·100 g^-1,感官评分为95.48分。与单一菌株发酵黑青稞制品相比,混菌发酵黑青稞的黄酮含量(32.22 mg·100 g^-1)、 多酚含量(230.68 mg·100 g^-1)及DPPH自由基清除能力(95.03 μmol·L^-1)显著提高。气相色谱-质谱(GC-MS)分析结果表明,酵母菌单独发酵的黑青稞中共检出33种挥发性风味物质,米根霉单独发酵的黑青稞中共检出41种挥发性风味物质,混菌发酵的黑青稞中共检出46种挥发性风味物质,其中酯类和醇类是3种发酵方式黑青稞制品的主要风味组分。混菌发酵黑青稞的醇类、酯类和酸类种类及含量均显著高于其余两种发酵方式,其相对含量分别达到59.09%、29.44%和6.46%,风味更丰富。综上分析,混菌发酵使黑青稞制品在功能及风味方面具有一定的优势。本研究结果为混菌发酵黑青稞制品的开发和应用奠定了基础。     

广东石豆兰不同溶剂提取物抗氧化及与总黄酮、总酚含量的关系

为明确广东石豆兰的抗氧化能力及抗氧化成分,以鳞茎为材料,以甲醇、乙醇、丙酮和乙酸乙酯为提取剂得到4种提取物,测定了4种提取物中总黄酮、总酚含量及其抗氧化活性,并分析了两者之间的关系。结果表明,石豆兰总酚含量高于总黄酮,乙醇为总酚和总黄酮2种物质的最佳提取溶剂;甲醇提取物对羟基自由基清除力和对Fe²⁺的螯合力最强,对DPPH自由基清除效果最差;丙酮提取物具有最强的总还原力和清除超氧阴离子的能力,而清除羟基自由基能力最弱;乙酸乙酯提取物清除DPPH自由基的能力最强,但总还原力、清除超氧阴离子的能力、Fe²⁺的螯合力最弱。此外,除了DPPH自由基外,其他4个抗氧化指标与总黄酮或总酚含量呈正相关(0.185<r<0.969),总还原力与总黄酮含量呈显著相关。本研究结果为广东石豆兰抗氧化物质的提取及进一步开发利用提供了参考依据。     

黑水虻幼虫蛋白质的制备及体外抗氧化活性

本文主要研究黑水虻幼虫蛋白质的制备及其体外抗氧化活性。以黑水虻幼虫为原料,采用碱提酸沉法提取黑水虻幼虫蛋白质,并于等电点沉淀,沉淀复溶后再浓缩、透析、冻干。分别测定了其总还原力,超氧阴离子自由基清除活性、羟基自由基清除活性、DPPH自由基清除活性、ABTS自由基清除活性、金属离子螯合能力及脂质体系中抗氧化能力,并将其体外抗氧化能力与维生素C(测定金属离子螯合能力时与EDTA)和卵清白蛋白进行比较。结果显示:BSFLP的等电点在4.8左右,并且该法所提蛋白纯度较高,表明利用碱提酸沉法对黑水虻幼虫进行蛋白的提取的方法可行。BSFLP的总还原力约是VC的0.013倍,是OVA的1.319倍;BSFLP的超氧阴离子自由基清除活性强于OVA,而弱于VC;其清除羟基自由基、清除DPPH自由基、清除ABTS自由基、螯合亚铁离子、亚油酸体系中抑制过氧化的IC50分别为2.577、3.965、0.228、0.876、5.050 mg·m L-1,也均介于VC(或EDTA)和OVA之间,说明BSFLP具有较高的体外抗氧化活性。本文为黑水虻的进一步研究与综合利用及抗氧化功能蛋白食品的研发提供了一定的依据。     

超微粉碎对青稞麸皮粉多酚组成及抗氧化活性的影响

为评价超微粉碎对青稞麸皮多酚、体外抗氧化活性和淀粉消化酶抑制活性的影响。该研究制备了3种粒径分别为335.94、72.52、22.69μm的青稞麸皮粉体,对3种粉体的多酚、黄酮含量及其组成、体外抗氧化活性与淀粉消化酶活性抑制率进行测定。结果表明:与粗粉相比,2种微粉的多酚(游离酚、结合酚)、黄酮和总酚含量均显著高于粗粉(P0.05)且粒径越小,含量越高;青稞麸皮粉共检出19种酚酸,其中游离酚以阿魏酸和藜芦酸为主,结合酚以阿魏酸和苯甲酸为主;随着粒径的减小,粉体多酚提取物的抗氧化活性(DPPH·自由基清除能力、FRAP还原能力、ABTS~+·自由基清除能力)及对α-葡萄糖苷酶、α-淀粉酶抑制率均显著增强(P0.05);粉体多酚组成及含量与体外抗氧化活性及淀粉消化酶活性抑制率存在一定的相关性。相关分析结果表明:青稞麸皮游离酚提取物中2,4-二羟基苯甲酸、藜芦酸是清除DPPH·自由基、抑制α-葡萄糖苷酶活性的主要贡献物质,阿魏酸是抑制α-葡萄糖苷酶及α-淀粉酶活性的主要物质;结合酚提取物中2,4-二羟基苯甲酸是抑制α-淀粉酶活性的主要物质。该结果显示超微粉碎一定程度上可提高青稞麸皮中多酚含量、体外抗氧化活性及淀粉消化酶抑制率,可作为青稞麸皮食品的一种有效前处理加工手段。     

鱼粉加工压榨液经酶解发酵后的风味变化

为实现鱼粉加工副产物的高值化利用,本研究对鱼粉加工压榨液经酶解发酵后的挥发性风味及游离氨基酸含量进行了分析。结果表明,鱼粉加工压榨液经酶解发酵后,其滋味成分、游离氨基酸含量、呈味强度和呈鲜能力明显增加,且其牛磺酸含量高达0.263 g·100mL^-1,远高于市售鱼露。挥发性风味分析表明,酶解和发酵显著改善了鱼粉加工压榨液的风味,其醛醇类化合物、吡嗪类以及含硫类化合物含量均有所增加,酮类物质含量下降,其风味与市售鱼露相当。本研究为鱼粉加工压榨液或其他水产品下脚料的综合利用提供了有效手段。     

Chemical and antioxidant properties of casein peptide and its glucose Maillard reaction products in fish oil-in-water emulsions

Maillard reaction products (MRPs) were prepared by reacting casein peptides with different concentrations of glucose at 80 °C for up to 12 h. The chemical properties of MRPs and their effects on lipid oxidation in fish oil-in-water emulsions were investigated. Increasing browning development and absorbance in 294 nm in the MRPs caused an increase in DPPH radical scavenging, but a decrease in iron chelation, which could be related to the loss of free amino groups in the peptides. The MRPs produced with longer reaction time or higher glucose concentrations were less effective in inhibiting lipid oxidation in emulsions at pH 7.0 compared to casein peptides alone. However, the antioxidant activity of MRPs in emulsions at pH 3.0 was not decreased by prolonged heating. The bitterness of MRPs was less than that of the original casein peptides, and bitterness decreased with increasing heating time and glucose concentrations. Therefore, the Maillard reaction was a potential method to reduce the bitterness of casein peptides while not strongly decreasing their antioxidant activity.     

Progress of the Maillard reaction and antioxidant action of Maillard reaction products in preheated model systems during storage

The progress of the Maillard reaction and the effect of Maillard reaction products (MRPs) on lipid oxidation in preheated model systems containing pregelatinized starch, glucose, lysine, and soybean oil have been studied during storage. The samples, either containing all components or excluding one or more of them, were heated at 100 degrees C for 90 min and then stored for up to 180 days at 25 degrees C. Browning indices and lipid oxidation were measured, and the results showed that, in samples containing oil, the Maillard reaction had a significant rate also at room temperature and confirmed the ability of MRPs to retard peroxide formation. Under the conditions adopted the rate of the Maillard reaction was increased by the presence of the oil and its oxidation products. The antioxidant action of the MRPs was also evaluated using a peroxide scavenging test based on crocin bleaching. The results demonstrated that antioxidant activity developed with increased browning of the samples.     

A new procedure to measure the antioxidant activity of insoluble food components

The measurement of antioxidant activity was limited to soluble components to date. Functional groups, which are bound to insoluble matters, may exert antioxidant activity by a surface reaction phenomenon. This hypothesis was tested on the insoluble matters of foods, food ingredients, and Maillard reaction products (MRPs). Insoluble matters were prepared by consecutive washes with water and methanol followed by a lyophilization of the insoluble residue. The measurement was performed by a new procedure using 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazil (DPPH) colored radicals. These insoluble matters always showed antioxidant activity. Alkali hydrolysis reduced up to 90% the antioxidant activity of cereal-based insoluble matters, thus confirming that fiber-bound compounds have a major role in their antioxidant activity. The antioxidant activity of the insoluble MRPs was not significantly affected by processing conditions, but severe treatments increased the ratio between insoluble and soluble matters. The contribution of insoluble matter to total antioxidant activity was limited for fruits and vegetables, but it was relevant for cereal-based foods and increased over 50% for dietary-fiber-rich ingredients.     

Effects of carnosine on volatile generation from Maillard reaction of ribose and cysteine

Carnosine occurs naturally in meat and meat products in significant quantity, and it possesses strong antioxidant activity that inhibits lipid oxidation and enhances shelf life. In this study, the effects of carnosine on thermal flavor generation were investigated using the model system of cysteine and ribose, which was heated to the roasting temperature of 180 degrees C for 2 h at pH 5 and pH 8.5. The results indicated that carnosine affected volatile formation in a complex manner. Volatiles identified from the liquid phase of the reaction systems of ribose and cysteine showed that the sulfur-containing compounds such as thiophenes, thiazoles, and polysulfides were the most abundant compounds. The addition of carnosine into the reaction mixtures in general caused a reduction in contents of thiophenes and some important meaty flavor compounds such as 2-methyl-3-furanthiol, 2-furfurylthiol, and their associated dimers. On the other hand, it facilitated the generation of several important nitrogen-containing volatiles such as pyrazine, methylpyrazine, 2,6-dimethylpyrazine, and other alkyl pyrazines and thiazoles, which are known to elicit roasty and nutty flavor notes. The results suggested that carnosine acts as a nitrogenous source to facilitate the formation of nitrogen-containing compounds, possibly by degradation to form ammonia.     

Redox-related cytotoxic responses to different casein glycation products in Caco-2 and int-407 cells

Sugar-casein glycation products (GPs) were generated by Maillard reaction (MR) with different monosaccharide sources [e.g., glucose (Glc), fructose (Fru), and ribose (Rib)] and prolonged heating (e.g., 27 days at 55 degrees C) to produce Maillard reaction products (MRPs) that varied in opponent (L, a, b) color measurement and changes in pH, available lysine, and amino-sugar ratio. Theses results signified different rates of three sugar and casein glycation. Sugar-casein GPs from aldohexose, ketohexose, and aldopentose sugar sources were recovered on day 18 of heating and compared for bioactive properties using human embryonic intestinal cell (Int-407) and adenocarcinoma cell (Caco-2) lines. Glu- and Fru-casein GPs produced significant (p < 0.05) decreases in antioxidant superoxide dismutase (SOD), glutathione peroxidase, and glutathione reductase enzyme activities in the Int-407 cell line, whereas no effect on antioxidant enzymes was obtained from Rib-casein GP. Moreover, the Caco-2 cell antioxidant enzyme status was not affected by the presence of sugar-casein GPs, regardless of sugar source. The reduction in antioxidant enzyme activity of Int-407 cells by Glu and Fru- casein GPs corresponded to a significant (p < 0.05) reduction in Int-407 cell viability. In contrast, no change in Caco-2 cell viability was observed with sugar-casein GP. This finding demonstrates that the noted variable cytotoxic, sugar specific effects of casein GP were related to reductions in critical antioxidant enzyme activities. Moreover, the source of intestinal cell line was an important factor to show the effect of sugar-casein GPs on redox-related cytotoxicity.     

Antioxidant properties of roasted coffee residues

The antioxidant activity of roasted coffee residues was evaluated. Extraction with four solvents (water, methanol, ethanol, and n-hexane) showed that water extracts of roasted coffee residues (WERCR) produced higher yields and gave better protection for lipid peroxidation. WERCR showed a remarkable protective effect on oxidative damage of protein. In addition, WERCR showed scavenging of free radicals as well as the reducing ability and to bind ferrous ions, indicating that WERCR acts as both primary and secondary antioxidants. The HPLC analyses showed that phenolic acids (chlorogenic acid and caffeic acid) and nonphenolic compounds [caffeine, trigonelline, nicotinic acid, and 5-(hydroxymethyl)furfuraldehyde] remained in roasted coffee residues. These compounds showed a protective effect on a liposome model system. The concentrations of flavonoids and polyphenolic compounds in roasted coffee residues were 8,400 and 20,400 ppm, respectively. In addition, the Maillard reaction products (MRPs) remaining in roasted coffee residues were believed to show antioxidant activity. These data indicate that roasted coffee residues have excellent potential for use as a natural antioxidant source because the antioxidant compounds remained in roasted coffee residues.     

Comparison of volatile compounds isolated from the skin and flesh of four potato cultivars after baking

Four potato cultivars, Cara, Nadine, Fianna, and Marfona, were selected. Potatoes were baked in their skins prior to separating the skin and flesh and preparing extracts of the volatile flavor compounds using a modified Likens--Nickerson apparatus. The concentrated extracts were analyzed by gas chromatography--mass spectrometry. Volatiles were identified and classified according to their origin, that is, lipid, sugar degradation and/or Maillard reaction not involving sulfur amino acids, sulfur compounds, methoxypyrazines, and other compounds. Quantitative and qualitative differences were observed between isolates from flesh and skins and among cultivars grown at different sites. Strongest isolates from skin were obtained for Nadine. For flesh, Cara gave isolates approximately 10-fold more concentrated than the other three cultivars. For skin, sugar degradation and/or the Maillard reaction was by far the most important source in all cultivars except Nadine, for which 62% of the volatiles were accounted for by the sesquiterpene solavetivone. Lipid and sugar degradation and/or the Maillard reaction were the main origins of volatiles in flesh. Calculated aroma values for a selection of the key potato volatiles identified reinforce the effects of cultivar and growing site on baked potato flavor.     

Effect of lipid composition on meat-like model systems containing cysteine, ribose, and polyunsaturated fatty acids

This paper compares the volatile constituents of model systems containing the important meat aroma precursors cysteine and ribose, with and without either methyl linoleate, an n-6 fatty acid, or methyl alpha-linolenate, an n-3 acid, both of which are present in meat. Many of the volatile compounds formed from the reaction between cysteine and ribose were not formed, or formed in lower amounts, when lipid was present. This may be due to the reaction between hydrogen sulfide, formed from the breakdown of cysteine, and lipid degradation products. In addition, cysteine and ribose modified lipid oxidation pathways, so that alcohols and alkylfurans were formed rather than saturated and unsaturated aldehydes. Several volatile compounds, which have been found at elevated levels in cooked meat from animals fed supplements high in n-3 acids, were formed when methyl alpha-linolenate reacted with cysteine and ribose. The possible effects of increasing the n-3 content of meat upon flavor formation during cooking are discussed.