乳酸菌发酵核桃酸乳不良气味的形成与分析

目的：为探究核桃发酵酸乳不良气味物的形成机制及其组成,改善其风味品质。方法：采用对比实验和感官评价分析不同发酵剂、不同原料组分对发酵乳不良气味产生的影响,研究核桃乳发酵过程中原料组分、羰基价与挥发性化合物的变化规律与相关性;采用顶空-固相微萃取-气相色谱-质谱联用技术分析核桃酸乳挥发性化合物组成,采用相对气味活度值和主成分分析法对关键性风味物和不良气味物进行分析。结果：原料中脂肪组分与不良气味产生显著相关,发酵过程中酸乳羰基价与不良气味形成显著相关;核桃酸乳主要的挥发性风味物包括：己酸等3种酸类化合物,乙偶姻等3种酮类物,正己醇等7种醇类化合物,(E)-2-庚烯醛等4种醛类化合物以及丁酸丁酯和其他类化合物;相对气味活度值大于1的挥发物为(E)-2-庚烯醛、乙偶姻、己酸、正己醇、正辛醇、1-庚醇、苯甲醛、2-壬酮、2-庚酮、苯乙烯和苯乙醇;关键风味物为乙偶姻、己酸、(E)-2-庚烯醛、正己醇。结论：己酸、(E)-2-庚烯醛、正己醇、苯甲醛为核桃酸乳不良气味的主要风味物,其形成的主要路径为核桃乳发酵过程脂肪水解产生较多的亚油酸、亚麻酸,在脂肪氧合酶作用下氧化,裂解产生C6～C9的醇、醛、酸...     

比较2种蓝圆鰺腌干工艺中脂质氧化与挥发性风味物质形成的关系

为探明鱼类腌制过程脂质氧化与特征风味物质形成的关系,以蓝圆鰺(Decapterus maruadsi)为原料,采用2种不同的腌干方法,传统高盐(traditional high salt,HS)法和低盐乳酸菌(low-salt lactic acid fermentation,LAF)法对其进行加工。测定2种工艺的腌干鱼加工过程中不同加工阶段脂肪氧合酶(lipoxygenase,LOX)、过氧化值(peroxide value,POV)、硫代巴比妥酸(thiobarbituric acid reactive substances,TBARS)值、主要挥发性风味物质的变化规律,利用Person相关系数分析2种工艺加工过程中脂质氧化、挥发性风味物质形成规律及两者之间的关系。结果表明:LOX活性均呈现先增加后降低趋势,除烘干末期之外酶活性HS法大于LAF法(P0.05),成品中LOX活性较鲜鱼分别增加了25%(HS)、34.8%(LAF);POV、TBARS值变化趋势与LOX变化趋势基本相同,烘干后期POV急速下降;成品中主要挥发性风味物质为醛、酮、烃、醇类物质,挥发性风味物质主要形成于烘干期间;LAF法生产的产品在HS法产品风味基础上增加了花香味;LOX与脂肪的氧化、风味物质形成之间具有一定的正相关性且脂肪氧化对风味物质的形成具有重要作用;LAF法更利于LOX发挥酶活力,促进风味物质特别是醛类物质的形成。     

基于SPME-GC-MS结合化学计量学分析山核桃加速氧化过程挥发性成分的变化北大核心CSCD

为了解山核桃中的主要挥发性成分,同时探明不同氧化程度山核桃挥发性成分的动态变化规律,采用顶空固相微萃取-气相色谱-质谱法(SPME-GC-MS)结合主成分分析法对山核桃制品(熟制后的)加速氧化过程中的挥发性成分进行分析。结果表明:山核桃加速氧化过程中共鉴定出43种主要挥发性物质,有24种物质香气活力值(OAV)大于1,其中主要呈香物质为2-甲基丁酸乙酯和糠醛;在加速氧化过程中,山核桃酸值、过氧化值和饱和醛含量显著增加,不饱和醛和杂环类化合物含量显著减少;主成分分析显示,山核桃加速氧化可分为3个阶段,0~7 d为氧化初级阶段,此时醛类、酯类、酸类含量较高,变化较小,14~35 d为氧化加速阶段,此时醇类、醛类和酮类化合物种类显著增加,42 d后为酸败阶段,该阶段挥发性成分主要为小分子饱和醛。通过分析山核桃挥发性成分,可获悉山核桃氧化程度和氧化阶段,有助于更好地鉴别山核桃品质。     

脂质氧化产生香味物质

综述了脂质自动氧化、热降解产生的挥发性物质及含有不饱和脂肪酸的脂质氧化在肉风味中的重要作用.着重叙述了脂质氧化生成重要的香味物质醛、酮、醇,并概述了猪肉脂肪受热生成的香味物质.     

不同脂肪酶酶解奶油制备奶味香基的研究

选用Hansen calf lipase、Amano lipase A6、Lipozyme RM IM 3种脂肪酶对无水奶油进行适度酶解制备奶味香基。采用气相色谱分析了酶解奶油中游离脂肪酸组成,结合顶空固相微萃取-气相色谱质谱联用技术对酶解奶油中的挥发性风味成分进行研究,并通过感官评价对酶解奶油进行风味剖面分析并对烘焙产品偏好性评定。结果表明:3种脂肪酶选择性酶解产生中短链脂肪酸的能力均较强,其中动物来源的Hansen calf lipase对中短链脂肪酸的选择性酶解能力最高,酶解奶油中短链脂肪酸相对含量为42.9%,且该酶解奶油和烘焙产品具有令人愉悦的奶味和干酪味;3种酶解奶油中的挥发性风味成分主要为脂肪酸、醛类、酮类、内酯类物质。     

扒鸡加工过程中挥发性风味物质的变化规律

为探究扒鸡加工过程中风味物质的变化规律,以德州扒鸡为研究对象,采用固相微萃取结合气相色谱-质谱联用（solid phase microextraction-gas chromatography-mass spectrometry,SPME-GC-MS）技术测定其加工过程中的风味物质,并通过气味活度值（odor activity value,OAV）分析它们的贡献。结果表明：从扒鸡加工过程的7 个采样点共检测到56 种风味物质,其中醛类7 种、醇类11 种、烃类27 种、酮类4 种、杂环化合物2种、醚类2种、酚类1种、酯类1种、含硫化合物1种;扒鸡的主要挥发性风味物质为醛类、醇类、烃类和酮类;加工过程中,各类风味物质含量总体上呈先增加后降低的趋势,卤制阶段挥发性风味物质的数量和含量显著增加（P＜0.05）,恒温卤煮后风味物质含量达到最大;二甲基二硫、己醛、壬醛、庚醛、1-辛烯-3-醇、2-戊基呋喃、D-柠檬烯、桉叶油醇和丁香酚的OAV＞10,表明这些物质对扒鸡整体风味贡献较大,其主要来源于加工过程中不饱和脂肪酸的氧化及卤制时添加的香辛料。综上,卤制是扒鸡风味物质形成的关键加工阶段。     

速溶豆粉、牛奶粉及羊奶粉挥发性成分的比较

对速溶豆粉、牛奶粉和羊奶粉的挥发性成分进行鉴定并比较,分析三者挥发性成分的差异。结果表明,速溶豆粉中共鉴定出42种挥发性物质,牛奶粉中共鉴定出48种挥发性物质,羊奶粉中共鉴定出47种挥发性物质,主要包括醇类、醛酮类、烃类、酸类、酯类和其他类等物质。三者中烃类、醛酮类和酯类物质的种类和含量均较高。速溶豆粉检出的醇类和酸类物质含量最高;牛奶粉中检出的烃类和酯类物质含量最高;羊奶粉中检测到的醛酮类和其他类物质含量最高。聚类分析和主成分分析结果表明,癸醛、(E,E)-3,5-辛二烯-2-酮、1-十二烯、正癸酸、丙位辛内酯、2-正戊基呋喃、2,6-二叔丁基对甲酚是速溶豆粉的关键挥发性物质;壬醛、δ-癸内酯、十二烷、丁位十二内酯、2,2,4,6,6-五甲基庚烷、1-十三烯是牛奶粉的关键挥发性物质;1-戊醇、庚醛、2-庚酮、二甲基砜、3-辛烯-2-酮、壬醛、γ-十二内酯等挥发性物质是羊奶粉的关键挥发性物质。这些物质是导致速溶豆粉、牛奶粉和羊奶粉风味差异的主要物质。     

蛋黄粉中关键香气活性物质分析及其在储藏过程中的香气变化

为探究蛋黄粉在储藏过程中的风味变化,本文采用SPME/GC-O-MS法对不同储藏时间蛋黄粉的挥发性化合物进行测定,并确定关键气味活性物质,利用主成分分析法(PCA)分析不同储藏时间样品的关键气味活性物质主要差异。结果表明:在蛋黄粉样品中,最终鉴定出31种挥发性成分,其中醇类9种,醛类7种,酮类9种,酯类1种,杂环类5种等。在这31种香气成分中,能够通过嗅闻仪被检测到的气味成分为2-甲基丁醛(可可粉味)、异戊醛(麦芽味)、正己醛(青草味)、1-辛烯-3-酮(蘑菇味)、2-壬酮(热牛奶味)、3,5-辛二烯-2-酮(脂肪味)、乙酸丙酯(奶酪味)、2-戊基呋喃(青豆味)、2,5-二甲基吡嗪(烤坚果味)、5-甲基-2-乙基吡嗪(果香味),由于它们的重要贡献作用,因此被鉴定为蛋黄粉的关键气味活性物质。对储藏时间和关键气味活性物质进行主成分分析(PCA)并结合相对浓度变化得知,在储藏初期,即0~2个月,对蛋黄粉具有贡献作用的香气物质较为单一,主要为吡嗪和醛类物质,随着储藏时间的增加,蛋黄粉中气味物质的种类和浓度均有所增加,主要表现为醇类,酮类物质的增加,使蛋黄粉具有更为丰富的风味轮廓。以上结果表明,脂肪氧化与美拉德反应是蛋黄粉整体风味发生变化的重要原因,脂肪氧化易带来不利影响,美拉德反应产物大多起到协调风味的作用,因此,为提高蛋黄粉货架期稳定性,抑制脂肪氧化和促进美拉德反应生成是可以采取的措施。     

BIOCHEMISTRY OF TEA FERMENTATION: CONVERSION OF AMINO ACIDS TO BLACK TEA AROMA CONSTITUENTS

SUMMARY: ¹⁴C-amino acids were added to fresh tea-leaf homogenate undergoing conversion to black tea. After conversion (30 min, 25°C), the volatile compounds present in the headspace over the reaction mixture were collected and analyzed by gas chromatography. Results showed that leucine, isoleucine, valine and phenylalanine were partially converted to the aldehydes expected from a Strecker degradation. These aldehydes are constituents of black tea aroma. Further, drying of the fermented mixture caused an additional amount of the aldehydes to be formed. In contrast, no detectable volatile compounds were formed from aspartic acid, glutamic acid, glutamine, arginine, threonine. serine or theanine under the same conditions. Production of aldehydes from amino acids was shown to be dependent on the enzymic conversion process: Tea leaf which had been inactivated by steam treatment was not effective in causing formation of volatile aldehydes from the amino acids. Identical results were obtained in a model tea fermentation system composed of a crude soluble enzymes extract from tea leaves, purified epigallocatechin gallate and ¹⁴C-amino acids. Ascorbic acid was found to inhibit formation of aldehydes from amino acids in this model tea fermentation system; dehydroascorbic acid by itself was found to be effective in causing formation of volatile aldehydes from amino acids.     

基于全二维气相色谱质谱法对全脂乳粉在不同水合工艺下挥发性成分的分析

为了优化全脂乳粉水合工艺,探究低温水合对复原乳风味影响,本研究采用顶空固相微萃取（Headspace solid phase microextraction, HS-SPME）结合全二维气相色谱质谱法（Comprehensive two-dimensional gas chromatography-mass spectrometry,GC-GC-MS）考察全脂乳粉单段水合（55℃水合30 min）和两段水合（55℃水合30 min后4℃水合4、8、12 h）工艺条件下复原乳主要挥发性化合物相对含量,并利用ROAV法和主成分分析法分析挥发性物质对复原乳的风味贡献。结果表明：四组复原乳样品共鉴定出醇、醚、呋喃等9大类挥发性物质共68种,十二醇、正己醛、正辛醛、壬醛、反-2-辛烯醛、癸醛、反式-2-壬醛为四组复原乳共有的特征风味物质,醛类化合物对复原乳特征风味的贡献大于其他挥发性化合物;通过主成分分析,将单段水合复原乳与两段水合复原乳进行了良好区分,增加工序4℃水合工艺有利于降低1-辛烯-3-醇、十二醇、反式-2-癸烯醛造成的异味,其中4℃水合8 h最有利于提升复原乳有益风味,为最佳水合工艺...     

Volatile Compounds and Chemical Changes in Ultrapasteurized Milk Packaged in Polyethylene Terephthalate Containers

The volatile compounds profile and chemical stability of ultrapasteurized 2% milk bottled in amber polyethylene terephthalate (PET) were studied along with its shelf life of 60 d at 5 °C. Identification of volatile compounds using a solid‐phase microextraction (SPME) technique with gas chromatography‐mass spectrometry was performed in situ in the commercial product. Chemical stability was determined by measuring dissolved oxygen, free sulfhydryl groups, ascorbic acid, and headspace oxygen. The classes of volatile compounds identified were ketones, aldehydes, hydrocarbons, fatty acids, alcohol, and miscellaneous compounds. Volatile compounds found consistently during the storage period were 2‐heptanone, methoxy‐phenyl‐oxime, decane, 1‐ethyl‐2,4‐dimethyl‐benzene, D‐limonene, 2‐nonanone, octanoic acid, dodecane, and 4‐(1,1,3,3, ‐tetramethylbutyl) phenol. Possible products of lipid oxidation, such as hexanal, octanal, and nonanal, were also positively identified. Chemical stability of PET‐bottled milk was demonstrated by the insignificant changes in pH or TA, with the exception of ascorbic acid concentration, which degraded in the product at 60 d of refrigerated storage. Sensory evaluation of the milk samples revealed that there is no noticeable oxidized or rancid off‐flavor at 60 d of storage.     

Characterization of traditional Istrian dry-cured ham by means of physical and chemical analyses and volatile compounds

The aroma-active compounds of Istrian dry-cured ham were investigated by using headspace-solid phase microextraction and gas chromatography-mass spectrometry (GC-MS). Samples of biceps femoris were also evaluated by measuring physical and chemical characteristics: moisture, protein, fat, ash and NaCl content, a(w) value; colour: L*, a*, b* and oxidation of fat: TBARS test. About 50 volatile compounds were identified and quantified which belonged to several classes of chemical: 5 alcohols, 8 aldehydes, 7 alkanes, 1 ketone, 2 esters, 9 monoterpenes and 15 sesquiterpenes. Except volatile compounds derived from lipolysis and proteolysis the most abundant constituents were terpenes (62.97; 41.43%) that originate from spices added in the salting phase of the production process.     

基于ROAV和嗅闻技术分析乳脂的关键风味化合物

利用固相微萃取-气相色谱-质谱（solid phase microextraction-gas chromatography-mass,SPME-GC-MS）分析国内市场常见的8种乳脂产品（4种黄油、2种稀奶油及2种发酵黄油）的挥发性化合物,并采用相对气味活度值（relative odor activity value,ROAV）和气相色谱-嗅闻（gas chromatography-olfactometry,GC-O）鉴定关键风味化合物。结果发现：8种乳脂产品中共检出40种挥发性化合物,主要包括7种醛类、6种甲基酮类、7种脂肪酸类和7种内酯类。ROAV法确定的关键风味化合物共17种,GC-O可识别7种关键风味化合物。其中,乙酸、丁酸、己酸、δ-辛内酯、δ-癸内酯、γ-十二内酯的ROAV大于1,且可被GC-O识别,是最为重要的6种关键风味化合物。     

GCMS、GCOMS结合感官评价分析牦牛奶粉风味组分

本实验以乙醚为萃取溶剂,采用同时蒸馏萃取法（SDE）提取牦牛奶粉中挥发性组分,结合气相色谱-质谱联用技术（GC-MS）和气相色谱-嗅闻-质谱（GC-O-MS）,对牦牛奶粉中风味物质定性定量分析。通过8名感官评价人员对牦牛奶粉进行感官评价,奶粉样品色泽良好,其中奶香味、奶油味和甜味比较浓郁,有微弱咸味和煮熟味,无苦味、酸味及涩味。GC-MS和GC-O-MS共同检测出21种挥发性物质,包括酮类8种,醛类3种,烯烃类3种,醇类2种,杂环类2种,酚类2种,醚类1种。其中醇和酮类物质含量较高,分别为46.85μg/m L和38.63μg/m L。实验表明,GC-MS、GC-O-MS结合感官评价分析牦牛奶粉中的风味组分的方法是较为准确和高效的。      

Determination of volatile compounds in cows' milk using headspace GC-MS

The composition of the volatile fraction of milk from cows was investigated in a survey of milk samples using a headspace sampling technique and gas chromatography coupled to mass spectrometry analysis (GC-MS). Milk samples were collected from 12 farms, selected for similar management, breed and level of production. Farms were also grouped according to the type of forage in the ration: (1) hay; (2) hay and maize silage; (3) hay, maize silage and grass silages. Forty-one compounds in milk were isolated and identified from GC-MS headspace analysis. Quantitatively, the most representative chemical class was ketones (eight compounds, 170 microg/kg), followed by aldehydes (nine compounds, 63 microg/kg), alcohols (eight compounds, 36 microg/kg), and lower amounts of hydrocarbons (six compounds), sulphur compounds (three compounds), esters (four compounds) and terpenes (three compounds). The novel headspace sampling technique, and the consequent reduction of sample pre-treatment, allowed the identification of low-molecular weight volatile compounds, and reduced the risk of producing artefacts during analysis. Discriminant analysis was used to identify a classification criterion for milk samples, using type of forage in the ration as a grouping variable. Posterior probability error rate indicated that aldehydes provided one of the best discriminant criteria for grouping milks according to ration composition. When all 41 identified volatile compounds were included, discriminant analysis selected nine compounds (acetone, 2,3-butanedione, 2-butanone, ethanol, acetaldehyde, ethylacetate, ethvlisovalerate, dimethylsulphone) that did not fail the tolerance test and which correctly classified 100% of the original cases.     

超微粉碎对冬枣粉芳香成分的影响

采用固相微萃取与气相色谱质谱联用法（SPME-GC-MS）,测定了中短波红外干燥和变温压差膨化干燥的冬枣粉在超微粉碎后芳香成分的变化。结果表明,从中短波红外干燥普通粉碎枣粉中检测到38种芳香成分,超微粉碎枣粉中检测到44种芳香成分;从变温压差膨化干燥普通粉碎枣粉中检测到35种芳香成分,超微粉碎枣粉中检测到51种芳香成分。枣粉在超微粉碎后,酚类化合物、醇类化合物和烷烃类化合物的含量均有明显增加;酯类化合物,酸类化合物和醛类化合物的含量均有明显降低。      

燕麦酸面团发酵剂的冻干和储藏对面包风味的影响

应用固相微萃取技术(SPME)和气相色谱- 质谱联用技术(GC-MS)研究发酵剂冷冻干燥(冻干)前后面包中的挥发性风味物质,考察发酵剂的冻干和储藏对燕麦酸面包风味的影响。结果表明：旧金山乳杆菌发酵燕麦酸面包中的挥发性风味物质共87 种,主要包括酸类、醇类、醛类、酯类、酮类、脂肪烃类,以及一些芳香族和杂环类化合物。酸类物质的含量最高,其次是醇类、芳杂环类和醛类物质。在发酵剂冻干和储藏过程中,醛类和醇类物质先增加后减少,酸类、酯类、酮类和脂肪族化合物先减少后增加,芳杂环类物质含量则持续升高。燕麦酸面团发酵剂冻干后以及储存30d 制得的面包依然具有丰富的风味。乳酸菌和酵母菌的竞争作用导致乙酸和乙醇含量呈现相反的变化。糠醛含量持续升高,而己醛则在冻干后显著减少,并在存储30d 后消失。     

发酵乳风味及其分析技术研究进展

发酵乳制品具有悠久的历史, 富含蛋白质、脂肪、糖类和矿物质等营养物质, 具有调节机体功能、预防和治疗疾病、延长寿命等保健功能功效, 此外因其具有独特的发酵风味及组织状态, 深受消费者欢迎。发酵乳风味是评估其品质的主要指标之一, 乳酸菌在发酵过程中可以生成多种风味化合物, 其中主要包括酸类、酮类、酯类、醛类, 这些化合物的种类和含量均会影响发酵乳的品质?本文主要概述了发酵乳中挥发性风味物质的组成及形成机理, 同时对发酵乳关键风味化合物的分析技术进行了总结, 为发酵乳风味及其品质提高、新产品开发及关键技术工艺升级提供理论基础与依据。     

Influence of exopolysaccharide‐producing cultures on the volatile profile and sensory quality of low‐fat Tulum cheese during ripening

The objective of this investigation was to compare the composition and changes in the concentration of volatiles in low‐fat and full‐fat Tulum cheeses during ripening. Tulum cheese was manufactured from low‐ or full‐fat milk using exopolysaccharide (EPS)‐producing or non‐EPS‐producing starter cultures. A total of 82 volatile compounds were identified belonging to the following chemical groups: acids (seven), esters (21), ketones (14), aldehydes (six), alcohols (14) and miscellaneous compounds (20). The relative amounts of acids, alcohols and aldehydes increased in the cheeses made with EPS‐producing cultures during 90 days of ripening. Differences were found in the volatile profile of full‐fat Tulum cheese compared with the low‐fat variant, especially after 90 days of ripening. Exopolysaccharide‐producing cultures changed the volatile profile, and the EPS‐producing cultures including Streptococcus thermophilus + Lactobacillus delbrueckii subsp. bulgaricus + Lactobacillus helveticus (LF‐EPS2) produced cheese with higher levels of methyl ketones and aldehydes than the non‐EPS cultures. In the sensory analysis, full‐fat Tulum cheeses and the cheese produced with the EPS‐producing culture containing Lb. helveticus (LF‐EPS2) were preferred by the expert panel. It was concluded that the use of EPS‐producing starter cultures in the manufacture of low‐fat Tulum cheese had the potential to improve the flavour.