蛋白酶对黄酒发酵的影响及挥发性成分分析

为了改善黄酒生产工艺,本文研究风味蛋白酶(Flavorzyme)、中性蛋白酶(Neutrase)、复合蛋白酶(Protamex)对黄酒发酵及风味物质的影响。采用传统摊饭法进行黄酒酿造,糖酵期添加蛋白酶,30℃发酵3 d后,再15 d低温发酵30 d,经压榨、灭菌得成品黄酒。测定了黄酒挥发性成分,筛选32种香气化合物进行主成分分析(Principal Component Analysis,PCA)与聚类热图分析;并通过香气活力值(Odor Activity Value,OAVs)评价香气化合物对黄酒整体香气的贡献。结果表明,风味蛋白酶能促进酵母菌生长,提高酒精度,并促进挥发性成分生成,总酯含量上升了97.6%,与风味蛋白酶相关性高的琥珀酸二乙酯(r=0.992)、己酸乙酯(r=0.990)、乙酸异戊酯(r=0.987)和乙酸乙酯(r=0.982)等香气物质集中分布在第一象限,对第一主成分、第二主成分均有正向作用;风味蛋白酶提高了异戊醇、乙酸乙酯、肉豆蔻酸乙酯等物质对黄酒整体香气的贡献率(OAVs>1),减少了4-乙基愈创木酚辛辣、刺激的气味。发酵过程中风味蛋白酶的添加能改善黄酒风味品质。     

黄酒香气成分的影响因素分析

黄酒香气成分复杂,主要由酯、醛、醇类等构成,来源于原料、麦曲、微生物代谢及贮存过程中发生的生化反应。综述了国内学者对黄酒香气成分的研究,分析了黄酒香气的主要来源及影响因素,为黄酒香气成分的进一步研究提供参考。     

基于嗅辨仪与气质联用确定黄酒中的关键风味物质

用顶空固相微萃取,结合气相-质谱联用技术分析了黄酒中的挥发性风味物质。运用动态风味稀释嗅辨系统,对黄酒中的一些风味物质进行嗅觉阈值的测定,结合这些风味物质在黄酒中的含量进一步确定了这些物质的香气强度,从而确定了对黄酒香气有重要贡献的关键风味物质,结果发现这些关键风味物质的呈香强弱,不完全是与其物质的含量成正比的,而是可能与其香气强度呈正相关关系。利用动态风味稀释嗅辨仪得到的这一规律,对于预测未知风味物质的呈香强弱具有一定的指导意义。     

麦曲对黄酒风味影响的研究新方法

用酶制荆替代麦曲进行黄酒发酵试验,对挥发性香气成分及游离氨基酸进行检测,并与传统黄酒发酵试验进行对比.发现用酶制剂替代麦曲发酵时部分醇类、酯类、醛类、氨基酸类物质的含量与加麦曲时存在部分差异.试验结果表明,麦曲的加入对酯类物质和氨基酸类物质的含量影响明显,而对醛类物质和醇类物质的影响不大.本试验为黄酒麦曲对黄酒风味的研究提供了一种新的研究方法.     

红曲黄酒传统酿造过程挥发性风味组分及微生物菌群多样性分析

为探究红曲黄酒传统酿造过程中的挥发性风味组分及菌群结构动态变化规律,采用顶空固相微萃取-气相色谱-质谱联用技术、主成分分析和正交偏最小二乘法判别分析模型,系统比较传统酿造初期、中期和末期3 个时期酒醅样中的挥发性风味成分,同时运用二代高通量测序技术解析传统酿造过程不同时期的微生物菌群结构。结果表明：红曲黄酒传统酿造过程挥发性风味组分及菌群结构变化显著,优势菌群-挥发性风味组分的Spearman相关性分析发现：红曲黄酒中的挥发性风味物质大多与传统酿造中、末期中的优势菌群呈正相关。研究结果阐明红曲黄酒传统酿造过程中香气组分形成与微生物菌群之间的关系,确定与关键香气组分形成密切相关的微生物类型,为红曲黄酒中功能微生物的分离筛选和发酵调控提供基础数据。     

不同品种小米对黄酒风味影响的研究

为探究不同品种的小米原料对黄酒的挥发性风味成分的影响，该实验利用顶空固相微萃取（HS-SPME）提取技术和气相色谱-质谱联用（GC-MS）检测技术，测定了不同品种小米酿制的黄酒中的风味物质的种类和含量。结果表明，从5个品种小米黄酒共检测出222种风味物质，黄金1号、小香谷、大金苗、晋谷21及东方亮所酿小米黄酒分别检测出56、92、98、81、74种风味物质，酯类和醇类化合物为小米黄酒的主要风味物质，5个品种小米黄酒中共有的风味物质为β-苯乙醇、辛酸乙酯、己酸乙酯、丁二酸二乙酯、乙酸乙酯，各个品种的小米黄酒都有其独特的风味物质。说明不同品种小米对黄酒酿制中产生的挥发性风味成分种类与含量都有较大的影响，进而影响小米黄酒的综合口感。     

乙醇含量对广东黄酒香气成分的影响

该文研究了乙醇含量对黄酒挥发性香气成分的影响。采用顶空固相微萃取结合气质联用（HS-SPME-GC/MS）技术对在发酵过程中添加6个乙醇含量（25%vol、30%vol、35%vol、40%vol、45%vol、50%vol）的食用酒精发酵的黄酒进行检测。结果显示,除了发酵时添加50%vol食用酒精的黄酒样品,其他每个乙醇含量的黄酒样品的香气成分都有独特成分,加50%vol食用酒精的黄酒所含主要香气成分相对含量最高,达到了80.28%,而35%vol的相对含量最少,为39.09%;风味成分比例较大的酯类、醇类和工厂黄酒有约50%的相同成分,不同成分推测是受乙醇含量的影响,表明乙醇含量对黄酒挥发性香气成分的形成有较为明显的差别。     

新型松茸黄酒发酵过程中键合态与游离态香气成分分析

通过比较新型松茸黄酒不同发酵阶段(松茸提取液、前发酵前期、前发酵后期、后发酵后期)键合态、游离态香气物质的组成及含量的具体差异,为松茸类黄酒的风味特性研究提供科学依据。以自制新型松茸黄酒为研究对象,采用官能化聚苯乙烯/二乙烯苯萃取柱(Cleanert polar enhanced polymer-solid phase extraction, Cleanert PEP-SPE)对新型松茸黄酒游离态和键合态化合物进行分离,结合顶空固相微萃取技术结合气相色谱-质谱联用仪(headspace solid-phase microextraction combined with gas chromatography-mass spectrometry, HS-SPME-GC-MS),对不同发酵阶段的新型松茸黄酒中游离态、键合态挥发性物质的种类和含量进行检测分析。结果显示,发酵过程中键合态、游离态香气成分共127种,其中键合态香气成分77种,主要以醇类、醛类和酚类为主(未检测到吡嗪类和呋喃类);游离态香气成分107种,以醇类和酯类为主(未检测到2-甲基丁醛等部分醛类),分析表明两种形态挥发性组分存...     

中国黄酒中挥发性和不挥发性物质的研究现状与展望

简要回顾了中国黄酒风味成分分析的历史与现状.从微量成分的种类上看,中国黄酒中目前已经检测到的微量成分达100种以上,包括醇类、醛类、酸类、酯类、酚类、含氮化合物,以及其它化合物.近年来,顶空取样、液液萃取、色谱分离技术、固相微萃取等技术已经开始应用于黄酒的风味成分研究.随着先进技术的应用,必将对中国黄酒风味物质以及特征香味成分的研究起到决定性的作用.     

黄酒对猪肉炖煮过程挥发性风味物质变化的影响

基于电子鼻和固相微萃取-气相色谱/质谱联用技术(SPME-GC/MS)研究黄酒对猪肉炖煮过程挥发性风味物质变化的影响。主成分分析(PCA)、线性判别分析(LDA)方法对电子鼻数据进行分析,结果表明黄酒对炖煮猪肉的风味具有显著影响(P0.05),且LDA比PCA的区分度更清晰。SPME-GC/MS共从炖煮猪肉中分离鉴定出71种挥发性风味物质,包括醛类、醇类、脂肪烃类、酮类等。其中,醛类是主要的挥发性风味化合物,尤以己醛含量最高。采用"相对香气活度值(ROAV)"评价各挥发性风味物质对炖煮猪肉总体风味的贡献,得到13种主体风味成分(ROAV≥1):(Z)-2庚烯醛、(D)-柠檬烯、庚醛、苯甲醛、癸醛、辛醛、(E)-2-壬烯醛、壬醛、1-辛烯-3-醇,(E,E)-2,4-癸二烯醛,己醛,这些物质主要以脂肪香气为主。聚类分析(CA)方法将主体风味物质分为3类,分类结果表明,(E,E)-2,4-癸二烯醛和己醛是区分不同样品的关键挥发性风味物质。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.