Developments in instrumental techniques for food flavour evaluation: future prospects

Analytical instruments have enabled the discovery and quantification of many of the key taste and aroma compounds known today in food. Recent trends in instrument development have focused on following the temporal aspects of tastant (or odorant) release from foods, and their delivery to the sensory apparatus during eating. However, there is an increasing demand for detection systems that are not reductionist, but more holistic, with similar sensitivity and selectivity properties to the human sensory apparatus. The output from such detection systems would ideally provide an indication of quality, palatability and hedonistic appreciation. Advances in molecular biology may hold the key to future developments. Cloning of receptor proteins, individual receptors or the whole sensory organ may produce detection systems with similar function to the human sensory organs. However, it will be necessary to deconvolute the signals obtained from these systems to convert them into terms typically used to describe our perception of stimuli. © 2000 Society of Chemical Industry     

酸马奶中一株乳酸菌与一株酵母菌共生关系和风味代谢产物的研究

对内蒙古锡盟地区酸马奶中分离出的一株乳酸菌和一株酵母菌进行混合培养,测定了双菌培养体系中的风味代谢产物,以单菌培养作为对照。结果表明:酵母菌水解蛋白能力要强于乳酸菌;双菌培养基中有利于产出更多的风味物质;乳酸菌和酵母菌在发酵过程中都可以利用苹果酸和酒石酸作为碳源进行生长,在柠檬酸的利用上,乳酸菌可以进行柠檬酸代谢,而酵母菌以产生柠檬酸为特点,暗示了二者间的相互作用关系;在双菌培养基中甲酸、乙酸、丙酸的产量在不同时期都高于单菌培养过程中的生成量,提示出乳酸菌和酵母菌存在某种共生关系。     

酒花多酚-潜在的啤酒风味和风味稳定物质

从CO2萃取后的废酒花中获得的多酚提取物，可以在啤酒生产中评价它们的抗氧化力和潜在的风味特征。由LC-MS和LC-UV的分析数据可知获得的多酚提取物具有较高的选择性，且含有所有的多酚物质。采用固相萃取技术，提取的总多酚物质可以进一步被分级为原花青素、黄酮苷和异戊烯基黄酮。除原花青素外，所有多酚溶液都有很强的风味活性且对口感有利。在啤酒酿造过程中添加这些多酚提取物可以明显延长啤酒的风味稳定性？这些新的酒花制品能赋予啤酒独特的风味并提高啤酒的风味稳定性。     

Use of smear bacteria and yeasts to modify flavour and appearance of Cheddar cheese

The strains Staphylococcus saprophyticus DPC5671 and Corynebacterium casei DPC5298 were applied in combination with Debaryomyces hansenii DPC6258 to the surface of young Cheddar cheese curd to obtain two different smear-ripened cheeses. A surface microbiota developed over the incubation period, comprising of both yeast and bacteria; pulsed field gel electrophoresis confirmed that the inoculated strains of S. saprophyticus DPC5671 or C. casei DPC5298 were the dominant bacterial strains on the surface of the cheese at the end of the ripening period. The smear cultures changed the appearance and aroma, which were significantly different from the control cheese. The approach presented in this study represents a method for the development of new cheese varieties with novel aromas within a short ripening time.     

Methods and techniques in the research of tobacco flavour

This paper performs possible ways of tobacco-flavour investigations which allow to identify flavour components and to settle aroma factors and correlations with organoleptic evaluation. At first, the basic methods of tobacco flavour research based on the analysis of tobacco raw material, tobacco smoke, and headspace vapours were discussed. The methods of tobacco flavour investigation being useful in evaluation of tobacco quality were also reported. Hence, the instrumental methods and sensory methods of tobacco flavour research were shown. The usability of these methods in detecting the flavour components of tobacco and tobacco smoke as well as in evaluating the tobacco quality in practice was considered. Furthermore, the methods of tobacco flavour research and flavour evaluation used in our department were given. The quality of tobacco flavour was evaluated by means of a definite interpretation of the chemical analysis of tobacco or tobacco smoke. The investigations of tobacco flavour were also carried out by a method basing on a special treatment of tobacco, which modifies the chemical composition of the raw material and at the same time the sensory properties. In this case the components being responsible for the tobacco flavour could be investigated by detailed tobacco- and tobacco-smoke analysis connected with sensory evaluation.     

Potential impact of dairy yeasts on the typical flavour of traditional ewes' and goats' cheeses

The contribution of Debaryomyces hansenii, Kluyveromyces lactis and Kluyveromyces marxianus strains to the typical flavour of traditional ewes' and goats' cheeses was assessed. Fourteen yeast strains were grown in liquid medium mimicking cheese composition and volatile compounds were identified by gas chromatography-mass spectrometry. Yeasts were able to produce key volatile compounds characteristic of the cheeses from which they were isolated. Inter-species and inter-strain variations were observed. Under the conditions tested, D. hansenii produced the lowest levels of volatile compounds, with large intra-strain variations. Kluyveromyces strains primarily produced esters and alcohols. K. marxianus strains were associated with the production of acids, ethyl decanoate, 1-propanol and benzaldehyde, whereas K. lactis was correlated with the presence of ketones, ethyl acetate and secondary alcohols. In conclusion, this study shows the heterogeneous potential of dairy yeasts to contribute to final cheese flavour.     

Headspace flavour compounds produced by yeasts and lactobacilli during fermentation of preferments and bread doughs.

Production of volatile flavour compounds during fermentation with pure cultures of Saccharomyces cerevisiae and Candida guilliermondii, Lactobacillus brevis and Lactobacillus plantarum have been investigated, using wheat doughs and several preferements as substrates. For yeast, preferments consisted of 10% (w/v) glucose, maltose and sucrose solutions, whereas for lactobacilli they consisted of supplemented and unsupplemented (3% and 10% (w/v)) glucose solutions, and a 10% (w/v) wheat flour slurry. Seven volatile compounds (acetaldehyde, acetone, ethyl acetate, ethanol, hexanal+isobutyl alcohol, and propanol) were detected when using yeasts. All these compounds, except propanol, appeared for all the substrates assayed, with ethanol as the predominant component. Generally, S. cerevisiae produced higher amounts of the different components than C. guilliermondii. Both yeasts produced larger amounts of volatile flavour compounds during fermentation in glucose and sucrose solutions than in maltose or wheat dough. In general the yeasts examined produced more flavour components than the lactobacilli. For the lactobacilli the highest number of volatile flavour compounds were observed for substrates containing flour.     

发酵醋醅酵母菌的分离、生长特性及分子鉴定

从山西老陈醋发酵醋醅中分离纯化出2株酵母菌,编号分别为YW与YR-1.通过YW与YR-1在不同温度和pH值条件下的培养,采用浊度法测定培养菌液OD600值,确定最适生长温度与pH值,结果表明菌株YW最适生长温度为30℃,最适生长pH值为6.5;菌株YR-1最适生长温度为28℃,最适pH值为7.0.对菌株YW,YR-1的核糖体ITS+5.8S rDNA区的克隆与测序,获得菌株YW与YR-1的ITS+5.8S rDNA片段长度分别为607bp与602bp,序列已提交至Genbank(登录号为JX205095和JX205094).通过在Genbank数据库BLAST以及与亲缘关系较近模式菌株构建分子发育树,表明YW属于毕赤酵母属(Pichia),与Pichia guilliermondii亲缘关系最近,命名为Pichia guilliermondii YW; YR-1属于掷孢酵母属(Sporobolomyces),与Sporobolomyces camicolor亲缘关系最近,命名为Sporobolomyces carmicolor YR-1.     

Enumeration of yeasts in dairy products: a comparison of immunological and genetic techniques

Enzyme-linked immunosorbent assay (ELISA) and PCR techniques have been developed for the detection of spoilage yeast species in dairy products. Polyclonal antibodies against live yeast cells (AY) were raised in rabbits by inoculation of a mixture of 10 yeast species frequently associated with dairy products spoilage. AY antibodies were used for the development of two ELISA formats (indirect and double-antibody sandwich ELISA) for the detection of yeast species in milk and yogurt. A PCR assay was also developed for yeast detection in dairy products, using primers designed to amplify a conserved 250-base pair fragment of the 18S rRNA of the yeast species. The results obtained in this work show that ELISA techniques using polyclonal antibodies against viable yeast cells are of limited value for the detection and enumeration of spoilage yeast species in dairy products. On the contrary, PCR amplification of a conserved region of the 18S rRNA of the yeast species allows the homogeneous detection of all the yeast species tested and, combined with an overnight enrichment of samples, could be used for the detection of low levels of viable spoilage yeast species in dairy products.     

咖啡主要烘焙风味物质的形成及变化规律

咖啡以其独特的风味和功能特性受到人们的喜爱。烘焙温度及烘焙时间决定了咖啡的烘焙程度,并对咖啡风味物质的产生及变化产生重要影响。咖啡主要烘焙风味物质是与咖啡风味直接相关且代表性强的香气成分,本文通过综合分析烘焙程度与咖啡主要风味物质的形成和变化规律的关系,为系统了解和掌握精品咖啡烘焙工艺提供科学参考。     

咖啡主要烘焙风味物质的形成及变化规律

咖啡以其独特的风味和功能特性受到人们的喜爱。烘焙温度及烘焙时间决定了咖啡的烘焙程度,并对咖啡风味物质的产生及变化产生重要影响。咖啡主要烘焙风味物质是与咖啡风味直接相关且代表性强的香气成分,本文通过综合分析烘焙程度与咖啡主要风味物质的形成和变化规律的关系,为系统了解和掌握精品咖啡烘焙工艺提供科学参考。      

Processing characteristics and flavour of full lotus root powder beverage

BACKGROUND: Lotus root beverage is commonly made from raw lotus root (RLR). However, RLR production is strictly limited, because it is prone to decomposition and browning after its short harvest season. In this study an innovative beverage was prepared from full lotus root powder (FLRP) as a substitute for RLR in an attempt to solve this problem. RESULTS: The components of FLRP basically corresponded to those of RLR, but there was some loss of heat‐labile compounds. Using differential scanning calorimetry, a gelatinisation temperature range of 57.08–67.80 °C was determined for FLRP with an average particle size distribution of 70 µm. The optimal conditions for enzymatic treatment of FLRP beverage were determined by response surface methodology as an enzyme concentration of 2.2 g kg^?1 at 53 °C for 86 min. Turbidity decreased from 1082 to 280 nephelometric turbidity units following enzymolysis. Properties of FLRP beverage were also studied and a qualitative comparison of flavour compounds between RLR and FLRP beverages was made by electronic nose. CONCLUSION: Basic flavour compounds were consistent and flavour radar plots had approximately the same shape, area and proportion when all ingredients were identical apart from FLRP and RLR. Therefore, in terms of flavour, FLRP beverage appears to be a feasible substitute for RLR beverage. Copyright © 2010 Society of Chemical Industry     

产香酵母的筛选及其苹果酒发酵特性

从分离自赤霞珠葡萄酿酒不同时期发酵液中的酵母菌中筛选产香菌株,并对其苹果酒发酵特性进行研究。结果表明,经感官评定初筛,获得7株产香较优的酵母菌,并对其进行耐酒精、耐SO2和耐盐性能分析,其中菌株B2-13具有较好的发酵性能,经分子生物学鉴定菌株B2-13为葡萄酒有孢汉逊酵母（Hanseniaspora uvarum）。菌株B2-13发酵苹果酒酒精度为4.2%vol～5.5%vol,糖度为2.6～44 g/L,共鉴定出32种香气成分,主要有酯类（6种）、醛酮类（4种）、醇类（6种）、酸类（8种）等,其中异戊醇、苯乙醇含量最高,分别为0.36 mg/mL和0.16 mg/mL,另外还有赤霞珠干红葡萄酒的特有香气物质3-羟基-2-丁酮（0.16 mg/mL）。菌株B2-13是一株具有较好的苹果酒发酵和产香性能的酵母菌株,有良好的工业化生产应用前景。     

甘肃天然优良酵母菌株的发酵特性评价

以分离自甘肃的146株野生酵母为材料,通过杜氏管发酵法初筛出发酵力强、香味浓的24株菌作为供试菌株,其中23株酵母菌耐SO2浓度超过550mg/L;15株耐NaCl浓度高达28％;5株耐51℃高温：10株耐pH值为1．5-13;17株耐70％的葡萄糖;7株耐18％的乙醇,模拟发酵结果表明：菌株SQ5、SQ13、SQ14、SQ15、SQ24起始发酵快,其中菌株SQ24产酒精度为8％（vol）,SQ4产浓郁果香。以蛇龙珠和巨峰葡萄为原料酿酒,菌株SQ4、SQ14、SQ24发酵能力强,葡萄酒品质和理化指标达到国标要求,有望用于甘肃地方特色葡萄酒的生产。     

酒曲用嗜杀酵母的选育及其生长发酵特性研究

通过原生质体融合技术选育到一株嗜杀酵母Sa2,对Sa2的嗜杀特性及其和出发菌株(酿酒酵母1445)的生长发酵特性进行对比研究.结果表明,嗜杀酵母Sa2既对麸皮中的主要杂菌有不同程度的抑制作用,又不影响小曲根霉菌的正常生长;其最适生长发酵温度为30℃,最适pH值为6.5,Sa2与出发菌株相比表现出较好的耐酒精和耐糖特性;用Sa2发酵籼米酒醪酒精度可达15.2％vol.嗜杀酵母Sa2可以用于低碳模式(生料或生熟料混合)生产小曲.     

Influence of four different coagulants on the physicochemical properties,textural characteristics and flavour of tofu

The coagulation mechanism and quality characteristics of tofu depend on the choice of coagulant. The effects of using magnesium chloride (MgCl₂), calcium sulphate (CaSO₄), glucono-δ-lactone (GDL) and fermented soybean whey (FSW) as coagulants for tofu were investigated using solid-phase microextraction (SPME), two-dimensional gas chromatography coupled with mass spectrometry (GC×GC-MS), scanning electron microscopy (SEM) and analysis of textural characteristics and physicochemical properties. Results showed that GDL tofu exhibited the highest yield (202 g 100 g⁻¹) and moisture content (76.3%). FSW tofu had the highest protein content (18.5%), amino acid content (15.85%) and textural properties. GC×GC-MS analysis revealed the number of 49, 44, 55 and 63 flavour substances, respectively. In sensory evaluation tests, GDL tofu was reported to possess a smooth surface and white colour. The microstructure of FSW tofu was dense and uniform. Through the above technical researches, the study suggested FSW gave tofu the best quality, more unique flavour and more potential popular among consumers.     

Identification of yeasts associated with milk products using traditional and molecular techniques

An integrated approach including phenotypic (morphological, biochemical and physiological characterization) and genotypic (RAPD-PCR, sequencing of D1/D2 domain of 26S rRNA encoding gene) methods was used for the identification of yeasts isolated from different milk products. There were 513 isolates in all, 460 ascomycetous and 53 basidiomycetous yeasts. The yeast isolates were characterized on the basis of their biochemical and physiological properties, and the D1/D2 domain of 26S rDNA was sequenced in selected strains. Relying on the obtained results from both the data-sets, corresponding type strains were selected and compared with the respective yeast isolates from milk products by RAPD fingerprinting. The strains showing a degree of similarity >80% were considered conspecific. By means of the applied techniques it was possible to identify 92% yeast isolates at species level. Debaryomyces hansenii, Geotrichum candidum, Kluyveromyces marxianus, Yarrowia lipolytica and Candida zeylanoides are the most frequently isolated species. The majority of the yeasts were isolated from fresh and sour curd cheese. A comparison of the results obtained by phenotypic and genotypic investigation revealed that the identification based on classical methods was supported by genotypic characterization in only 54% of examined isolates. The results described in this work show that the applied molecular identification is a reliable approach to the identification of yeasts associated with milk products in contrast to the conventional biochemical and physiological tests. The identification of new yeast species requires additional genetic markers such as sequencing of different genes or DNA:DNA hybridization.     

Far infrared assisted refractance window drying of apple slices: Comparative study on flavour,nutrient retention and drying characteristics

In the present investigation, far infrared (FIR) assisted refractance window (RW) drying (FIR+RW) of apple slices (2 and 5 mm) was evaluated in comparison with RW and hot air (HA). FIR+RW reduced drying time by 50 and 69% compared to RW and HA, respectively. Also, FIR+RW drying retained a significantly higher amount of phenolics, flavonoids, ascorbic acid, and antioxidant activity, as compared to HA. Increase in FIR temperature from 50 to 60 °C reduced drying time by 10–19% without having any deleterious effect on quality. Colour, flavour, and microstructure of FIR+RW dried slices were comparable to that of RW. Nearly 46% saving in energy consumption was observed for FIR+RW drying compared to HA. Results suggested that FIR+RW drying can be explored as a potential technique for drying of fruits in a shorter time, with better retention of flavour, nutrients and also enhance energy efficiency.Industrial relevanceDried apple slices have a good market potential as a raw material in many processed foods and can be an alternative to deep fat fried chips for health-conscious consumers. This work focuses on assessing the efficacy of developed FIR assisted RW drying system in terms of drying time, energy, and quality attributes (colour, nutritional, flavour, microstructure) in comparison with conventional drying methods. The results showed that FIR assisted RW drying technique has great industrial potential in saving processing time as well as energy with better retention of quality of dried products.