SPME Arrow-GC-MS鉴定3种不同杀菌乳中特征香气物质

利用新型箭型固相微萃取-气相色谱-质谱联用法（Solid-phase Microextraction Arrow-Gas chromatography-Mass spectrometry,SPME Arrow-GC-MS）对3类杀菌乳中挥发性风味组分进行研究,并结合香气活性值（odor activity values,OAV）与热图分析进一步探究3种杀菌方法对牛乳中特征香气物质的影响情况。3类杀菌乳中共检测到78种挥发性风味物质,其中脂肪酸类11种、酯类4种、内酯类7种、酮类12种、醛类18种、醇类14种、含硫化合物2种、芳香及杂环类化合物10种。对萃取到的风味组分进行热图分析,结果表明：不同杀菌乳中特征香气物质存在明显差异,其中巴氏杀菌乳中特征香气物质是辛醛和壬醛;UHT灭菌乳中特征香气物质是γ-十二内酯、顺式-4-羟基-6-十二烯酸内酯、2-壬酮、2-十一酮以及辛醛、壬醛;INF杀菌乳中则是1-辛烯-3-酮和壬醛。     

基于SPME-GC-MS技术结合电子鼻电子舌分析不同热处理牛乳风味的差异

目的 探究不同热处理牛乳即巴氏杀菌乳、超高温瞬时（UHT）灭菌乳和蒸汽浸入式（INF）杀菌乳的香气品质差异。方法 利用固相微萃取-气相色谱-质谱联用法（SPME-GC-MS）对三种热处理牛乳的挥发性风味组分进行鉴定,并结合电子鼻和电子舌对不同热处理牛乳的风味进行更直观的区分。结果 GC-MS技术共检测出热处理牛乳中53种挥发性风味化合物,主要是由13种醛类、10种脂肪酸类、9种醇类、7种酮类和3种内酯类组成。其中巴氏杀菌乳以辛酸、癸酸等脂肪酸类和壬醛、癸醛等醛类为主;INF杀菌乳中以辛酸、癸酸、乙酸等脂肪酸类为主,其次是辛醛、壬醛等醛类和糠醇、2-乙基-1-己醇等醇类;UHT灭菌乳则是以2-庚酮、2-壬酮和2-十一酮等酮类为主,其次是辛酸、己酸等脂肪酸类和丙醛、壬醛等醛类,然后是δ-癸内酯和δ-十二内酯等内酯类。电子鼻对不同热处理牛乳有明显不同响应,主成分分析（PCA）前两主成分可以很好地区分不同热处理牛乳的挥发性风味物质,传感器W5S、W1S、W1W和W2S对牛乳气味影响最大。电子舌结果表明不同热处理牛乳在鲜味和口感浓厚程度上差异显著,且PCA分析前两主成分可以完全区分不同热处理牛乳...     

高压脉冲电场对牛奶中风味物质的影响

本实验采用SPME-GC-MS 联用的方法,对鲜牛乳、UHT 灭菌牛奶和高压脉冲电场(PEF)处理(35kV/cm,400μS,200Hz)牛乳的风味成分进行分析。从鲜牛乳、UHT 灭菌乳和PEF 处理乳分别鉴定出19、17、18 种主要挥发性化合物。通过对不同处理方式牛乳挥发性风味成分的比较研究,PEF 处理较UHT 处理对牛乳中风味物质影响较小,且产生较少的与蒸煮味相关的含硫化合物。     

浸入式和喷射式超高温瞬时灭菌对牛乳中活性蛋白和风味化合物的影响

超高温瞬时灭菌(ultra-high temperature treatment, UHT)是常用的牛乳杀菌技术,可分为直接式与间接式处理,其中直接式UHT技术由于成本高在乳品行业使用较少。近年来,随着消费者对牛乳营养物质和风味需求的升级,直接式UHT技术由于升温速度快、风味及营养成分损失少的优点,再次受到广泛关注。对比了浸入式和喷射式2种直接式处理技术对牛乳理化性质、活性乳清蛋白含量和挥发性化合物含量的影响。结果表明,浸入式UHT乳较喷射式UHT乳的平均粒径、失稳系数和黏度值均更小,但乳清蛋白变性率高。通过2种萃取方法——箭型固相微萃取法和溶剂辅助萃取法,结合气相色谱-质谱联用仪的分析结果,共在UHT乳中检测出59种挥发性化合物,其中,浸入式UHT乳中检测出50种,喷射式UHT乳中检测出52种。浸入式UHT乳中的酮、醛和脂肪酸类化合物比喷射式UHT乳中占比低,而酯类和醇类化合物占比高。主成分分析结果表明,浸入式UHT乳和喷射式UHT乳可根据挥发性化合物进行区分,说明不同的直接式UHT工艺可能对UHT乳风味产生影响。研究结果表明：若生产奶味更重的UHT乳,可选择喷射式UHT;若生产蒸煮...     

杀菌方法对牛乳中特征香气物质的影响

超高温瞬时杀菌法(UHT)、巴氏杀菌法和浸入式杀菌技术(INF)等是应用较为广泛的牛乳杀菌方法,本研究利用溶剂辅助风味蒸发法(SAFE)对生牛乳和3类杀菌乳中挥发性风味组分差别进行研究,结果表明：从4种牛乳中共检出挥发性香气物质48种,包括脂肪酸类11种、酮类5种、醛类6种、含硫化合物2种、酯类6种、醇类5种、芳香及杂环类化合物13种。在此基础上结合阈值进一步确定了上述风味组分的香气活性值(OAV)。4种牛乳样品中共有23种OAV值大于1的关键风味化合物,其中十六酸甲酯、2-壬酮和己醛等对牛乳整体风味的贡献度较大。基于偏最小二乘回归(PLS)对4种牛乳中关键风味组分和牛乳感官特征之间的相关性进行分析,结果表明：INF乳和巴氏杀菌乳的感官特征更为相似,具有较强奶香味与甜味,其对应的化合物为2-壬酮、2(5H)-呋喃酮和乙酸丁酯。UHT乳的感官特征为具有蒸煮味、浓厚感较强。该感官特征与二甲基砜、二甲基硫、2-乙基-1-己醇和2-十三酮等组分相关性较大。此外,生牛乳风味组分相对较少。     

基于顶空气相色谱-离子迁移谱法分析脱脂处理对牛乳挥发性风味物质的影响

目的 探究脱脂工艺对牛乳中挥发性风味物质影响。方法 采用顶空气相色谱-离子迁移谱法(headspace-gas chromatography-ion mobility spectrometry, HS-GC-IMS)构建全脂牛乳和脱脂牛乳挥发性风味物质指纹图谱,结合主成分分析(principal component analysis, PCA)对其中挥发性风味物质差异进行分析。结果 全脂牛乳和脱脂牛乳中共检出50个信号峰,鉴定出26种挥发性风味物质,主要包括6种醛、10种酮、4种醇、5种酯和1种萜烯物质。牛乳在脱脂处理后1-戊醇、2-庚酮、丁酸乙酯和2-甲基乙酸乙酯的含量降低,而辛醛、正壬醛、乙酸戊酯、E-2-庚烯醛、己酸乙酯和2-辛酮的含量则增加。结论 本研究明确了脱脂后牛乳中挥发性风味物质变化,脱脂处理未改变牛乳中挥发性化合物种类,但对醛类、酮类、醇类、酯类和萜烯类化合物的相对含量均具有显著性影响。     

SPME/GC-MS分析比较热处理乳中的挥发性化合物

采用固相微萃取-气相色谱-质谱法(SPME-GC-MS)对UHT灭菌乳和巴氏杀菌乳中的主要挥发性成分进行定性分析.结果表明,采用固相微萃取技术能够有效达到富集样品中风味成分的目的,通过GC-MS分离与检测,UHT牛奶共检出74种风味物质,UHT灭菌乳和巴氏杀菌乳存在57种共同风味成分,但二者在某些风味物质的组成及质量分数方面也存在差异,UHT灭菌乳的特征性风味物质为酮类、酸类及烃类物质,巴氏杀菌乳的特征性风味物质为烃类、酸类和醇类物质.     

水牛乳稀奶油及其酶解产物挥发性风味物质分析

为了解水牛乳稀奶油酶解前后挥发性风味体系的变化,利用固相微萃取(SPME)结合GC-MS的方法检测其中的挥发性风味物质。结果表明:水牛乳稀奶油中主要的挥发性风味物质为甲基酮类化合物,占整个挥发性风味物质的41.104%,主要包括2-庚酮、2-戊酮、2-壬酮、2-丁酮等;对其进行酶解后,酶解产物中短链脂肪酸为主要的挥发性风味物质,其中丁酸、己酸、辛酸、癸酸这4类化合物占总挥发性风味物质的88.009%,此外,酯类化合物的种类相对酶解前更丰富。     

热处理对牛乳理化特性的影响

热加工是杀灭牛乳中致病微生物的有效途径,但对牛乳的成分和性质也会产生影响。以F1和F2两个工厂的巴氏乳和超高温瞬时杀菌乳(UHT)为研究对象,原料乳作为对照,研究了热处理之后牛乳理化性质的变化。结果表明巴氏乳和UHT乳中脂肪、蛋白质、乳糖以及固形物的总量与原料乳中的基本一致,但巴氏和UHT热处理造成了乳中维生素C的损失以及泛酸含量的升高。游离氨基酸总量在F1和F2之间差异显著(P0.05),但是它受热处理方式的影响不显著。巴氏杀菌和UHT热处理对于乳粒径的影响不显著。牛乳的黏度和感官特性受巴氏和UHT热处理的影响显著,两个工厂UHT乳的黏度均较大。F1工厂UHT乳的风味得分较高,而F2工厂的巴氏乳风味得分更高。     

基于GC-IMS技术分析荞麦益生菌发酵乳的风味物质

为探明益生菌发酵对荞麦乳产生风味物质的影响,采用GC-IMS技术对3种发酵乳制品进行了挥发性成分分析,根据挥发性成分的指纹图谱并结合主成分分析阐明使用不同原料以及不同发酵剂的发酵乳风味物质的差异。结果表明,从3种发酵乳中共鉴定出35种挥发性物质,包括醇类、酮类、酯类、醛类、有机酸类等。益生菌发酵荞麦乳制品中,特征性风味物质为3-甲基丁醛、2-甲基丁醛、2-戊基呋喃、6-甲基-5-庚烯-2-酮等;市售发酵乳中主要为2-戊酮、丁醛、乙酸乙酯、乙酸丙酯、乙酸丁酯等;实验室自制发酵乳中风味物质种类较少;指纹图谱和主成分分析清晰地显示了3种发酵乳风味物质的差异。GC-IMS联用技术实现了发酵乳中挥发性风味物质的快速检测,可以为谷物发酵制品开发、发酵工艺优化及产品风味改善提供技术支持。     

Formation of the aroma of a raw goat milk cheese during maturation analysed by SPME–GC–MS

The volatile profile of the Spanish goat raw milk cheese of the protected designation of origin (PDO) “Queso Ibores” was studied at four stages of maturation (day 1, 30, 60, and 90) by the method of solid-phase micro-extraction–gas chromatography–mass spectrometry (SPME–GC–MS) to determinate the characteristic volatile compounds of this cheese and to know the changes in the volatile profile of this cheese during maturation. According to the PDO, Ibores cheese aroma varies between sweet and mild and it has a strong taste, slightly tart. A total of 64 compounds were detected: 14 acids, 18 alcohols, 13 esters, 6 ketones and 13 compounds which could not be classified in these groups. Carboxylic acids were the most abundant volatile compounds in the headspace of Ibores cheese. Content of volatile compounds was significantly modified (P < 0.05) during ripening. The relative total amounts of acids, esters and ketones increased during the first 60 days of maturation. The most characteristic compounds of Ibores cheese aroma were butanoic, hexanoic and octanoic acids, some alcohols (2-butanol and 2-heptanol), ethyl esters of hexanoic and butanoic acids, some methyl ketones (2-butanone, 2-pentanone and 2-heptanone) and δ-decalactone.     

巴氏灭菌与超高温灭菌对全脂牛乳挥发性风味物质的影响

采用顶空固相微萃取分别对原料全脂牛乳、巴氏灭菌全脂牛乳和超高温灭菌全脂牛乳的挥发性成分进行萃取,经气相色谱-质谱联用仪分析。结果显示,原料全脂牛乳中共鉴定出12种挥发性物质,主要包括酸类和烷烃类;巴氏灭菌全脂牛乳中共鉴定出17种挥发性物质,主要包括酸类、酯类、酮类和烷烃类;超高温灭菌全脂牛乳中共鉴定出17种挥发性物质,主要包括酸类、酮类和烷烃类。经数据统计分析,3种牛乳样品的挥发性组分呈现明显差异。     

Characterisation by SPME–GC–MS of the volatile profile of a Spanish soft cheese P.D.O. Torta del Casar during ripening

The volatile profile of the Spanish soft cheese of the Protected Designation of Origin (PDO) Torta del Casar, made from raw ewes’ milk, was studied in four different stages of ripening (1, 30, 60 and 90 days) by the method of SPME–GC–MS. A total of 46 compounds were detected: 13 acids, 9 esters, 4 ketones, 7 alcohols, 3 aldehydes, 7 aromatic compounds and 3 compounds which could not be classified into those groups. Carboxylic acids were the most abundant group isolated; their levels significantly increased during ripening and comprised 61.5% of the total aroma extract at the end of ripening. At day 90, acids of microbial origin were the most abundant, followed by acids derived from amino acids while acids from lipolysis of triglycerides were the least abundant. Esters were the next most important group and their amount also increased significantly during maturation, as did ketones, while alcohols content slightly decreased at the end of the ripening. At day 90, the compounds at highest levels were acetic acid, 3-methylbutanoic acid, butanoic acid propyl ester and 2-butan-one; so these compounds, due to their high levels and their low threshold value could play an important role in the final aromatic profile of this cheese.     

Volatile fraction and sensory characteristics of Manchego cheese. 1. Comparison of raw and pasteurized milk cheese

Manchego cheese can be manufactured from raw or pasteurized ewes' milk. An automatic purge and trap apparatus, coupled to a GC-MS was used to isolate. identify and compare the relative amounts of the volatile components of raw and pasteurized Manchego cheese during ripening. The majority of volatile compounds were more abundant in raw milk (RM) cheeses than in pasteurized milk (PM) cheeses. Alcohols and esters predominated in the profile of RM Manchego cheese, while methyl-ketones and 2,3-butanedione were quantitatively important in PM cheeses. Branched chain alcohols were much more abundant in RM cheeses. The discriminant analysis separated 100% samples into RM or PM cheeses by using only 16 volatile compounds. Aroma intensity was correlated with esters, branched chain aldehydes and branched chain alcohols in RM cheeses, and with esters, branched chain aldehydes, 2-methyl ketones and 2-alkanols in PM cheeses. Diacetyl was positively correlated with the aroma attribute 'toasted' and negatively correlated with aroma quality in PM cheeses.     

Effects of high pressure treatment on volatile profile during ripening of ewe milk cheese

The effect of high-pressure treatment on the volatile profile of ewe milk cheeses was investigated. Cheeses were submitted to 200, 300, 400 and 500 MPa at 2 stages of ripening (after 1 and 15 d of manufacturing) and volatile compounds were assayed at 15 and 60 d of ripening. High-pressure treatment altered the balance of volatile profile of cheeses, limiting the formation of acids, alcohols, ketones, aldehydes, and sulfur compounds and enhancing the formation of 2,3-butanedione. In general, cheeses pressurized at 15 d of ripening were more similar to untreated cheeses than those treated at 1 d. Cheeses treated at 300 MPa after 1 d of manufacturing were characterized by higher levels of free amino acids, ethanol, ethyl esters, and branched-chain aldehydes, whereas cheeses treated at 500 MPa after 1 d of manufacturing had lower microbial populations, showed the highest abundance of 2,3-butanedione, pyruvaldehyde, and methyl ketones, and the lowest abundance of alcohols.     

Volatile composition and sensory properties of industrially produced Idiazabal cheese

The volatile composition and sensory properties of industrially produced Idiazabal cheeses made from ewes’ raw milk (RM) or pasteurised milk (PM) and with addition of different starter cultures were compared. Cheeses were analysed at 90 and 180 d of ripening. Acids were the major volatile compounds in RM cheeses. Methyl ketones were the major volatile compounds in PM cheeses at 90 ripening days. However, the content of acids strongly increased with ripening whereas the content of ketones decreased in PM cheeses. The concentration of esters was higher in RM cheeses than in PM cheeses. No differences were found in the content of alcohols. Most aldehydes, hydrocarbons, terpenes and furans identified were minor volatile compounds in both RM and PM cheeses. In RM cheeses, characteristic sensory attributes for the aroma of Idiazabal cheese were present at 3 months, whereas in PM cheeses those desirable sensory attributes did not appear until 6 months of ripening.     

Quantitative determination of thermally derived off-flavor compounds in milk using solid-phase microextraction and gas chromatography

Many volatile compounds generated during the thermal processing of milk have been associated with cooked, stale, and sulfurous notes in milk and are considered as off-flavor by most consumers. A headspace solid-phase microextraction (HS-SPME)/gas chromatographic technique for the quantitative analysis of thermally derived off-flavor compounds was developed in this study. The extraction temperature, time, and sample amount were optimized using a randomized 2³ central composite rotatable design with 2 central replicates and 2 replicates in each factorial point along with response surface methodology. Calibration curves were constructed in milk using the standard addition technique, and then used to quantify 20 off-flavor compounds in raw, pasteurized, and UHT milk samples with various fat contents. The concentrations of these volatiles in raw and pasteurized milk samples were not significantly different. However, dimethyl sulfide, 2-hexanone, 2-heptanone, 2-nonanone, 2-undecanone, 2-methylpropanal, 3-methylbutanal, heptanal, and decanal were found at higher concentrations in UHT milk as compared with raw and pasteurized milk samples. In addition, the concentration of methyl ketones was greater in UHT milk with higher fat content. The calculated odor activity values suggested that 2,3-butanedione, 2-heptanone, 2-nonanone, 2-methylpropanal, 3-methylbutanal, nonanal, decanal, and dimethyl sulfide could be important contributors to the off-flavor of UHT milk. The HS-SPME technique developed in this study is accurate and relatively simple, and can be used for the quantification of thermally derived off-flavor compounds in milk.     

西藏开菲尔发酵乳中挥发性风味物质分析

采用顶空固相微萃取结合气相色谱-质谱联用技术对两种不同地理来源西藏开菲尔粒的发酵乳中挥发性化合物进行检测,并结合化合物的阈值计算香气活力值(odor activity value,OAV)。结果表明,两种发酵乳中共鉴定出挥发性化合物30种,酸类和醇类在两种发酵乳中均占优势。两种西藏开菲尔粒的产挥发性风味物质能力存在差异,发酵乳B中挥发性化合物的种类和总含量均高于A。酯类是两种发酵乳中最重要的香气贡献化合物,辛酸乙酯在两种发酵乳中香气贡献最高。不同类别化合物对两种发酵乳的总香气贡献存在差异,醇类对发酵乳A的总香气贡献高于B,酯类、酸类和酮类对发酵乳B的总香气贡献高于A。     

Use of wild Lactobacillus strains in an adjunct culture for a Roncal-type cheese

The effect of an added adjunct culture consisting of facultatively heterofermentative lactobacilli (FHL) on the volatile compounds and sensory characteristics of a Spanish ewes'-milk cheese was examined. Three cheese batches were prepared using a commercial starter, one from raw milk, another from pasteurized milk, and a third from pasteurized milk with an added culture of wild Lactobacillus. paracasei+Lb. plantarum. Analysis of the volatile compounds was carried out by the purge and trap method and gas chromatography with a mass spectrometer and disclosed a total of 86 compounds belonging to the chemical families hydrocarbons, fatty acids, esters, ketones, aldehydes, and alcohols. After ageing for 120 and 240 days, the cheese samples underwent sensory analysis by a panel of expert assessors. The attributes evaluated were characteristic odour and odour intensity and characteristic aroma and aroma intensity. Pasteurization of the milk had an effect on the formation of certain volatile compounds, adversely affecting the characteristic flavour of the cheese. Use of the adjunct culture in addition to the commercial starter improved the flavour of the cheese made from the pasteurized milk, which earned sensory scores similar to those awarded to the cheese made from the raw milk. Use of adjunct cultures consisting of indigenous FHL strains could help to conserve the traditional characteristics of Roncal cheese made from pasteurized milk, although some technical adjustments to the Regulations would be needed.