Changes in the volatile compounds and chemical and physical properties of Yali pear (Pyrus bertschneideri Reld) during storage

Volatiles from stored Yali pear (Pyrus bertschneideri Reld) were studied using high-resolution gas chromatography and the solid-phase microextraction (SPME) method of gas chromatography/mass spectrometry (GC/MS). The dominant components were ethyl butanoate, ethyl hexanoate, α-farnesene, hexanal, ethyl acetate, hexyl acetate, ethanol and so on. By using GC-olfactometry, it was demonstrated that the volatile compounds from SPME were responsible for the aroma of Yali pear. The levels of sugars, organic acids, and phenolic acids in Yali pear were investigated using high-performance liquid chromatography. Fructose was the dominant sugar, followed by glucose and sucrose. With increasing storage time, sucrose levels decreased, however fructose and glucose levels did not changed remarkably. There was a slight decrease in flesh firmness during storage. The general soluble solids concentration, slightly decreased after 5 months storage. Some aroma volatile components increased during storage, while others decreased, especially the esters. The organic acids and phenolic acids also changed. Yali pear flavor was affected by changes in the levels of volatile compounds, and chemical and physical properties.     

茶树品种对筠连红茶品质的影响

本文主要探讨不同茶树品种对筠连红茶品质的影响。选择当地主栽的福选9号、乌牛早、早白尖5号和四川群体品种四个茶树品种的原叶,按四川工夫红茶工艺制成红茶成品,检测主要生化成分、挥发性物质、感官指标。结果显示:4个品种所制红茶的茶多酚含量在16.12%~17.22%之间,可溶性糖含量在4.50%~9.11%之间,总黄酮含量在2.29%~2.70%之间,其中四川群体品种的茶多酚和可溶性糖含量显著(P<0.05)高于早白尖5号,乌牛早可溶性糖含量显著(P<0.05)高于其它3种红茶,早白尖5号的总黄酮显著(P<0.05)低于乌牛早和福选9号;4种红茶氨基酸总量在27.42~39.04 mg/g之间,其中呈味氨基酸占64.08%~69.38%,具有较好的滋味物质基础,四川群体品种、乌牛早及早白尖5号鲜味氨基酸分别占53.15%、52.05%和55.13%,具有开发高鲜红茶潜质;福选9号、乌牛早、早白尖5号和四川群体品种共检测出醇、醛、酯、酮、碳氢化合物和其它化合物等6类61种挥发性成分,共有成分22种,其中醇类物质是4个品种红茶的主要挥发性香气成分,且芳樟醇及其氧化产物含量丰富;感官审评结果显示,四川群体品种、乌牛早和早白尖5号所制红茶鲜爽醇厚,优于福选9号。因此,四川群体品种、乌牛早及早白尖5号更适宜生产优质筠连红茶。     

GC-MS法分析柠檬蒸馏酒与发酵酒挥发性风味物质

采用定量描述性感官评价法对柠檬发酵酒与蒸馏酒进行感官评定,检测其理化指标,并利用气质联用（GC-MS）技术分析其挥发性风味物质组分及含量。结果表明,2种柠檬酒口感接近,除涩味外,苦、酸、甜味无显著差异（P＞0.05）;总酸、还原糖和可溶性固形物含量差异均显著（P＜0.05）;通过GC-MS技术从柠檬发酵酒与蒸馏酒中分别检测出40种、33种挥发性风味物质,且均以酯类物质种类（20种、15种）及相对含量（53.63%、48.43%）最高。与柠檬发酵酒相比,除检测到酯类、醇类、酸类、醛类物质外,柠檬蒸馏酒中还检测到烷烃类、杂环类及烯类物质。     

发酵乳储存期内风味模型的建立与检验

使用多变量统计方法,以发酵乳风味协调感为因变量,主要风味指标羰基化合物(乙醛、双乙酰),酸类物质(挥发酸、总酸度)以及发酵乳成分(糖、脂肪、蛋白质和非脂乳固体)为自变量,建立发酵乳风味模型。对8种风味指标进行多元线性回归和主成分分析,挑选对因变量影响大而相关性较小的风味指标为自变量。最终选择双乙酰、挥发酸、糖和脂肪含量为风味模型的自变量,建立风味协调感与主要风味指标的多元线性回归方程。该模型中各变量系数在统计意义上显著,且各系数无明显多重共线性。最终模型的调整R2为0.447。随机样品对该风味模型验证结果显示,模型观测值与风味协调性预测值有较好的拟合,平均误差为7.18%。     

SENSORY QUALITY OF GALA APPLES AS INFLUENCED BY CONTROLLED AND REGULAR ATMOSPHERE STORAGE

The sensory quality of Gala apples stored for up to 4 months in delayed controlled atmosphere (CA), regular atmosphere (RA), and a combination of sequential CA and RA storage (CR) was evaluated. Sensory analysis included difference and acceptance testing. Firmness, soluble solids and titratable acidity contents, and volatile flavor profiles were measured analytically. Acceptability decreased with storage time. Apples stored in RA were more acceptable than apples stored in CA or CR; the differences between storage treatment were not significant after 4 months of storage. Firmness decreased with storage time, but was not affected by storage treatment. Soluble solids and titratable acidity contents were not affected by storage treatment or time. Storage treatment, storage time, and lot had a significant effect on the volatile flavor profiles. CA storage and extended storage contributed to decreases in the content of volatile flavor compounds.     

基于GC-MS法的椰子水及其饮料的风味成分分析

为了对不同成熟度椰子(椰青、嫩椰子、成熟椰子)的椰汁及椰子水饮料中挥发性风味物质组分和含量进行分析,采用蒸馏萃取装置提取样品中的挥发性成分,并用气相色谱-质谱(GC-MS)联用分析技术进行分离鉴定。结果表明,共检测出67种香气成分,分为7大类化合物,包括酯类32种,有机酸11种,醇类7种,醛类3种,酮类3种,酚类4种,其他类7种。在检出的香气物质中,确定主体风味组分主要是醇类、酯类和酸类3类物质,相同的挥发性成分是2,3-丁二醇。不同样品中,这些微量香气成分的种类含量有较大差别,成熟椰子原汁中风味物质的种类和含量较多。因此,椰子水原汁的挥发性成分直接影响椰子水饮料的感官质量。本试验研究为椰子水及其饮料感官品质的深入研究提供了一定的理论依据。     

CULTIVAR AND HARVEST DATE EFFECTS ON FLAVOR AND OTHER QUALITY ATTRIBUTES OF CALIFORNIA STRAWBERRIES

“Aromas,”“Diamante” and “Selva” strawberries were harvested in early and mid‐season and evaluated for quality attributes, flavor components, fermentative metabolites and physiological characteristics. Preference and flavor tests by consumer panels were also conducted. Cultivar variation was greater than harvest date variation as were differences in color, concentrations of anthocyanins, firmness, total soluble solids, sugars, pH, titratable acidity (TA), organic acids and aroma compounds. “Diamante” and “Selva” had higher aroma quality than “Aromas” fruits. The levels of fermentative metabolites were too low to have an impact on the aroma quality. “Diamante” and “Selva” strawberries had better overall flavor quality and were more preferred by consumers than “Aromas.” These differences were consistent over two harvest dates.     

猕猴桃品质指标差异分析及GC-IMS分析果汁中挥发性物质

以金艳、红阳、东红及万州红心4 种猕猴桃为原料,比较样品间感官差异（外观、内部横切面形态）、品质差异（出汁率、可溶性固形物、总糖、pH值、可滴定酸、VC、总酚、花色苷、黄酮、单宁）,结合主成分分析与聚类分析法对样品分析,同时采用气相色谱-离子迁移谱（gas chromatography-ion mobility spectrometry,GC-IMS）技术对不同品种猕猴桃果汁中挥发性成分进行分析。结果表明,4 个品种出汁率、总酸等含量差异不明显,万州红心猕猴桃品种中总糖、VC、总酚、黄酮及花色苷含量较其他3 个品种高,金艳品种中单宁含量较高,主成分分析和聚类分析结果较一致,金艳聚为一类,红阳、东红及万州红心聚为一类;采用GC-IMS技术在4 种猕猴桃果汁中共检测出55 种挥发性物质,不同样品之间挥发性物质差异较大,按照挥发性成分进行主成分分析与聚类分析,对样品进行分类,结果与按照品质指标分类结果一致。     

Volatile flavor compounds in yogurt: a review

Considerable knowledge has been accumulated on the volatile compounds contributing to the aroma and flavor of yogurt. This review outlines the production of the major flavor compounds in yogurt fermentation and the analysis techniques, both instrumental and sensory, for quantifying the volatile compounds in yogurt. The volatile compounds that have been identified in plain yogurt are summarized, with the few key aroma compounds described in detail. Most flavor compounds in yogurt are produced from lipolysis of milkfat and microbiological transformations of lactose and citrate. More than 100 volatiles, including carbonyl compounds, alcohols, acids, esters, hydrocarbons, aromatic compounds, sulfur-containing compounds, and heterocyclic compounds, are found in yogurt at low to trace concentrations. Besides lactic acid, acetaldehyde, diacetyl, acetoin, acetone, and 2-butanone contribute most to the typical aroma and flavor of yogurt. Extended storage of yogurt causes off-flavor development, which is mainly attributed to the production of undesired aldehydes and fatty acids during lipid oxidation. Further work on studying the volatile flavor compounds-matrix interactions, flavor release mechanisms, and the synergistic effect of flavor compounds, and on correlating the sensory properties of yogurt with the compositions of volatile flavor compounds are needed to fully elucidate yogurt aroma and flavor.     

Sensory, chemical and gas chromatographic evaluation of five raspberry cultivars

Five raspberry cultivars, ‘Chilcotin’, ‘Chilliwack’, ‘Meeker’, ‘Skeena’ and ‘Tulameen’, were evaluated for sensory attributes, and chemical and flavor volatile compounds. ‘Chilliwack’ and ‘Tulameen’ received high ratings in sweetness and overall impression with high soluble solids, total sugars and sugar:acid ratio. ‘Chilcotin’ rated low in overall impression and sweetness, and high in sourness and astringency, with low soluble solids, sugar:acid ratio and total sugars, and high titratable acidity. Principal factor analysis (PFA) of the sensory results separated the cultivars based on desirable (appearance, color, texture, aroma and sweetness) and less desirable (sourness, bitterness, astringency and off-flavor) attributes. Twenty-eight volatile compounds were analyzed by dynamic headspace and 18 identified by gas chromatography-mass spectrometry (GC-MS), most of which were terpenes which included -pinene, sabinene, γ-terpinene, - and β-ionone and caryophyllene. Volatile compounds varied among cultivars, with benzaldehyde (11·1–31·8%), -pinene (4·0–11·5%), ethyl heptanoate (6·9–15·2%), β-myrcene (13·2–19·6%) and γ-terpinene (12·2–20·0%) as the predominant volatiles. Correlation analysis established no relationships between sensory and chemical data with volatile compounds.     

ANALYTICAL CHEMISTRY: UNLOCKING THE SECRETS OF WINE FLAVOR

Knowledge of wine flavor has paralleled developments in analytical chemistry. In the 19th century, analytical methods focused on the determination of major wine components such as ethanol, organic acids, and sugars. The development of chromatographic techniques in the early 1900s and particularly development of gas chromatography in the early 1950s ushered in a new era of discovery for analytical chemists. Currently, more than 1300 volatile compounds have been identified in alcoholic beverages and new compounds continue to be discovered. At the beginning of the 21st century, the focus is beginning to shift away from identification and quantification of new flavor compounds and toward developing dynamic analytical techniques that can model the complex relationships between volatile composition and sensory properties. In addition, rapid, readily automated techniques that can be used to optimize agricultural (viticultural) practices and processing or aging conditions are being evaluated and developed.

Primarily, this review provides a discussion of the major volatile compounds involved in wine flavor and an overview of the analytical techniques that have been instrumental in investigating the flavor of wines made from Vitis vinifera grapes. Secondarily, a brief discussion of the flavor contributions and analysis of nonvolatiles is also presented.     

Volatile Compounds and Sensory Properties in Various Melons,Which were Chosen from Different Species and Different Locations,Grown in Turkey

Gas chromatography coupled to mass spectrometry using a static head space technique was applied to analyze the volatile aromatic compounds of various melons collected from different locations in Turkey. Some physicochemical and sensory analyses were also made. A total of 33 volatile compounds were identified. Differences in the physicochemical and sensory properties of various Turkish melon samples were observed. The multivariate analyses by the volatile compounds separated the three varieties into groups successfully. The most abundant volatile compounds as mean value in all melon varieties were ethyl acetate (22.10%), acetaldehyde (13.65%), and ethanol (23.25%). The results showed that Cantaloupe melons were more preferred by panelists, which had relatively high levels of esters being responsible for strong fruit flavor, like melon, as well as high total soluble solid content and low titratable acidity compared with Inodorus and Simama.     

不同蛋白酶对香菇酶解液性质的影响

选用碱性蛋白酶、风味蛋白酶和中性蛋白酶水解香菇粉,研究不同蛋白酶对香菇酶解液的水解度、营养成分、感官评价和挥发性风味物质的影响。结果表明,随着酶解时间的延长,三种酶解液的水解度先升高后降低,风味蛋白酶酶解4 h的酶解液水解度最高,达到26.03%;酶解液的可溶性蛋白质含量、多糖含量及鲜味和香菇特征风味在酶解过程中的变化趋势与水解度类似,其中碱性蛋白酶酶解液多糖含量较高、苦味最明显,风味蛋白酶酶解液可溶性蛋白质含量较高、苦味整体最弱,4 h的酶解液的整体感官评分最高,为22.80分。气相色谱-质谱联用（GC-MS）分析三种蛋白酶解液共检出30种挥发性风味物质,其中含硫化合物相对含量占绝对优势,均高达90%以上,对风味的贡献最大;醛类物质种类最多,含量仅次于含硫化合物,其中风味蛋白酶解液中醛类物质相对含量最高。因此,风味蛋白酶酶解液水解度、营养成分更高,且整体风味更好。     

不同工艺芝麻油的挥发性成分分析和感官评价

利用SPME-GC-MS分析6种工艺芝麻油的挥发性物质,建立了芝麻油的感官风味轮,使用直线标度对感官属性强度评分,并利用主成分分析法比较芝麻油的感官差异,列出部分挥发性物质对应的特征气味,以研究加工工艺对芝麻油的挥发性成分和感官品质的影响。结果表明:冷榨芝麻油的挥发性成分以醛类和酸类为主,具有较强的生芝麻味、土腥味、木屑味和青草味;精炼芝麻油中挥发性成分最少;芝麻原油由于含有正己烷,表现出较强的机油味和刺激感;芝麻压榨毛油、压榨成品油和小磨芝麻香油富含吡嗪类、酚类、醛类和酮类等物质,具有较强的炒芝麻味、焦香味、留香较久且风味浓郁。小磨芝麻香油风味最纯正和醇厚,口感最绵柔。     

A Study on Soluble Solids Content Assessment Using Electronic Nose: Persimmon Fruit Picked on Different Dates

Soluble solids content is an important internal quality attribute in determining fruit maturity and harvesting time. In this study, an electronic nose was used to monitor the soluble solids content based on the change of volatile compounds of persimmon fruit during different picking-dates. Principal component analysis was applied to investigate whether the sensors’ response of the electronic nose was able to distinguish persimmons among different picking dates corresponding to different maturity levels. The loading analysis was used to identify those sensors that contribute most for flavor modeling. The results indicated that the electronic nose could distinguish the different picking dates using principal component analysis. The model testing showed that a support vector machine could achieve better prediction accuracy and generalization than multiple linear regression and back-propagation neural network and the average prediction accuracy, root mean square error, and mean relative error of the soluble solids content. By using support vector machine models were 91.36, 0.71, and 0.58%, respectively, which implied that the electronic nose was effective for soluble solids content prediction of persimmons on the basis of the support vector machine model.     

模拟冷链温度条件下不同采收方式对黑皮鸡枞菌品质的影响

黑皮鸡枞菌是一种高营养价值的珍稀食用菌,逐渐受到消费者的喜爱,但其子实体含水量高、没有表皮保护,故在常温贮藏过程中极易腐烂变质。低温冷链和采收方式可影响黑皮鸡枞菌的贮藏品质。本实验选择在冷链温度条件下（10 ℃）以切和拔两种方式采收的黑皮鸡枞菌为材料,探究其在贮藏过程中感官、营养、生理和风味指标的变化。结果表明：不同的采收方式对黑皮鸡枞菌品质的影响明显;采收方式为拔的黑皮鸡枞菌的质构、颜色、味觉值均是优于切处理组,切的采收方式在前期更能够抑制乙烯的释放,在后期样品有更高的可溶性糖质量分数,且多酚含量、黄酮含量、可溶性蛋白含量、呈味核苷酸含量、呈味氨基酸含量、等效鲜味浓度（equivalent umami concentration,EUC）和C8挥发性化合物含量均为切处理组相对优于拔处理组。综上,在冷链温度条件下,采收方式为拔的黑皮鸡枞菌有相对更好的感官品质;采收方式为切的黑皮鸡枞菌具有更优的营养风味,适合于即买即食。本实验可为解决黑皮鸡枞菌贮藏期间品质劣变问题提供理论参考。     

基于GC-MS和GC-O的调味品鸡精特征风味物质研究

本文采用顶空固相微萃取气相色谱质谱联用技术(SPME/GC-MS)分析其风味成分,采用气相色谱嗅闻分析(GC-O)中的时间-强度法(OSME)和香气活力值法(OAV)确定其特征风味物质并推断其对整体风味的贡献程度,利用偏最小二乘法(PLS)建立感官属性与GC-MS分析风味成分的关系。研究结果表明,鸡精中共检测出105种风味成分,其中硫化物13种、烷烃26种、芳香族化合物18种、酮类11种、醇类4种、烯类15种、醛类6种、杂环化合物10种和酯类2种,其中32种风味物质经PLS分析显示与感官属性相关性较好。气相色谱嗅闻(GC-O)分析结果显示有23种可被嗅闻的香气成分,由OSME法和OAV法共同鉴定出的鸡精样品中特征风味物质有烯丙硫醇、甲基烯丙基硫醚、二烯丙基硫醚、二烯丙基二硫醚、1-石竹烯、2,4-癸二烯醛。说明GC-MS、GC-O、OAV法结合PLS法可以有效综合评价调味品鸡精中的特征风味物质。     

荔枝汁结冰-解冻浓缩过程中品质的变化规律

以灭菌后的荔枝汁为原料,采用结冰-解冻浓缩工艺将其浓缩,研究了浓缩过程对荔枝汁的可溶性固形物含量、褐变度和可滴定酸度的影响,并运用气相色谱-质谱联用法对浓缩过程中的荔枝汁的挥发性风味物质进行测定,探讨其品质的变化规律。结果表明:荔枝汁中可溶性固形物的含量和褐变度随解冻所得的荔枝汁总体积的增加而逐渐降低;浓缩过程中,挥发性风味物质的相对含量的变化趋势因物质类型不同而不尽相同。综合考虑理化指标与风味物质的变化规律,可将解冻过程中荔枝汁总体积的40%(v/v)处选定为浓缩汁与剩余液的分界点,得到的浓缩汁中风味较高。