Headspace Gas Sampling/GC Method for the Quantitative Analysis of Volatile Compounds in Cheese

Headspace gas sampling along with a fused silica capillary Carbowax 20 M column was examined for the quantitative analysis of some volatile compounds in cheese. Slurries prepared from natural cheeses were steam-distilled to isolate and concentrate volatile materials. The GC peak areas increased almost linearly as the solid concentrations in slurries were increased from 10 to 40%. However, a 30% solid slurry was used because the 40% slurry was too viscous to handle and distill. The maximum concentrations of volatile compounds were observed with 5.0 mL distillates collected. The relationships between chromatographic peak areas and added volatile compounds were linear between 0 and 80 ppb. Examination of a Cheddar cheese with different ages indicated that a few volatile compounds consistently increased or decreased in concentration with the age cheese.     

基于快速成熟模型的藏灵菇发酵切达干酪挥发性风味物质分析

通过建立快速成熟干酪模型,采用固相微萃取法提取传统藏灵菇发酵的切达干酪模型与商品发酵剂制作的切达干酪模型中挥发性成分,并结合气相色谱-质谱联用技术和气相色谱-嗅闻技术对萃取成分进行鉴定,结果表明醇类和酯类是藏灵菇发酵切达干酪成熟过程中的主要风味物质。藏灵菇发酵切达干酪模型中风味物质的种类和含量都明显高于商业发酵剂制作的切达干酪模型,其中酯类物质的变化最为显著。感官评价和风味分析结果表明,藏灵菇发酵切达干酪模型中酯类和醇类物质种类和含量更为丰富,风味更强,水果香味更浓郁,还具有酒香味。     

RETENTION OF FREE FATTY ACIDS DURING SPRAY DRYING OF CHEDDAR CHEESE

The effect of processing variables, such as total solids, atomization pressure and inlet drying air temperature, on the retention of free fatty acids (FFA) in Cheddar cheese during spray drying was investigated. A cheese homogenate was prepared with minimum heat treatment and spray dried at a feed temperature of approximately 43°C. The retention of FFA increased with molecular weight under all drying conditions. In the absence of emulsifying salts, a lower total solids content in the homogenate fed to the dryer increased the retention of FFA. For example, the maximum retention of butyric acid at 30% T.S. and at 4% T.S. was about 60% and 35%, respectively. In addition, higher atomization pressures and higher inlet drying air temperatures decreased the retention of FFA. Emulsifying salts were effective, especially at 40% T.S., in increasing the retention of FFA. These results could be predicted from the selective diffusion theory of the retention of volatile compounds.     

Dynamic Headspace Analyses of Volatile Compounds of Cheddar and Swiss Cheese during Ripening

The volatile compounds of Cheddar and Swiss cheeses during ripening for 9 wks at 11°and 21°C, respectively, were analyzed by a dynamic headspace analyzer/gas chromatograph every week. The compounds were identified by a combination of retention times and mass spectra. The volatile compounds of Cheddar increased 5.6 and Swiss cheese 15 times as ripening increased from 0 to 9 wks. The amount of volatile compounds of Swiss cheese was 2.6 times greater than that of Cheddar cheese during ripening. The volatile compounds were ketones, alcohols, aldehydes, esters, acids, sulfur compounds, benzenes, and hydrocarbons. Ketones and alcohols accounted for 92% of volatiles from Cheddar cheese and 88% of those from Swiss cheese.     

基于HS-SPME-GC-MS分析茶叶提取物对奶酪挥发性风味的影响

采用顶空固相微萃取法结合气相色谱质谱联用技术(headspace-solid phase microextraction-gas chromatography-mass spectrometry,HS-SPME-GC-MS)对原奶酪、绿茶奶酪和茯砖茶奶酪挥发性风味物质提取测定,分析茶叶提取物对奶酪挥发性风味的影响。结果显示,原奶酪、绿茶奶酪和茯砖茶奶酪分别检出37、36、39种挥发性风味物质。2-壬酮、苯甲醛、苯甲醇和3-辛酮为原奶酪的特征挥发性风味物质,己酸、4-苯基-1-环己烯和芳樟醇为绿茶奶酪的特征风味物质。癸酸乙酯、十二烷酸乙酯、辛酸乙酯和9-癸烯酸乙酯为茯砖茶奶酪的特征风味物质。三种奶酪感官评定分析显示,绿茶与茯砖茶奶酪具有较高的感官评分。综上,茶叶提取物可有效改善奶酪风味,对奶酪品质具有积极地促进作用。     

添加酿酒酵母的切达干酪风味研究

随着干酪市场的日益增长,开发新型风味干酪成为新的趋势.根据前期实验结果,研究选定了3种制作添加酿酒酵母的切达干酪(KY组、KH组、KC组)加工工艺,通过顶空固相微萃取和气相色谱-质谱联用技术、聚类分析及感官评价对干酪中挥发性风味化合物进行测定及分析,以此来评价酿酒酵母在切达干酪中的应用前景.干酪成熟过程中,3组干酪中挥...     

Influence of milk pretreatment on production of free fatty acids and volatile compounds in hard cheeses: Heat treatment and mechanical agitation

This work aimed to identify technological steps that can increase fat hydrolysis and volatile compounds production in hard cheeses; these biochemical events have been related with improved piquant taste and development of genuine flavor during cheese ripening. For that purpose, 2 different pretreatments of cheese milk were tested: heat treatment and mechanical agitation. Both factors were assayed at 2 levels: milk was either batch pasteurized or nonthermally treated, and mechanical agitation was either applied or not applied. For all combinations, hard cheeses (Reggianito type) were produced in a pilot plant and ripened for 90 d. In all cheeses the degree of lipolysis, assessed by gas chromatography, increased similarly during ripening. However, the proportion of short-chain fatty acids was higher in the cheeses made with unpasteurized milk, suggesting a higher activity of lipases with positional specificity toward the sn-3 position of the triglyceride, among which milk lipoprotein lipase is found. Similar results were found for most of the volatile compounds, determined by solid-phase microextraction-gas chromatography flame-ionization detector/mass spectrometry, which constitute the groups of ketones, alcohols, esters, and the group of acids. On the contrary, no effect of mechanical agitation was observed, although some interactions between factors were found. In the conditions of the study, results suggest that heat treatment had a higher effect on cheese lipolysis and volatile compounds production than partial destabilization of the fat emulsion produced by the agitation method applied.     

Study of organic acids, volatile fraction and caseins of a new Halloumi-type cheese during ripening in whey brine

Organic acids, fat hydrolysis, volatile compounds and sensory characteristics of a new brine cheese which combines characteristics of Halloumi and Feta cheeses during its ripening in whey brine (100g NaCl L⁻¹) were studied. Thermotolerant protease of Mucor miehei as a coagulant enzyme and a mixture of thermotolerant starter cultures Enterococcus faecium 0165 (0.5% w/w) and Lactobacillus casei 80 10D were used. Good quality new Halloumi-type cheese was produced with higher proteolysis than traditional Halloumi cheese kept in whey brine. The volatile compounds identified comprised alcohols, aldehydes, ketones, acids, esters, hydrocarbons and sulphur compounds. Ethanol was the dominant volatile compound determined. Lactic acid was the dominant acid produced; its concentration increased during ripening, reaching a maximum value of 9929 mg kg⁻¹ at day 30. Acetic acid was also found in high amounts, which increased during cheese ripening. Lipolysis of cheese was not intense. The most abundant acids of the mature cheese were palmitic, oleic and acetic acid. The Halloumi-type cheese scored higher in the sensory analysis when fresh than did the mature cheese.     

添加大豆分离蛋白对羊乳干酪风味物质的影响

以新鲜羊乳为原料,直投式乳酸菌混合菌种为主发酵剂,费氏丙酸杆菌为次级发酵剂,添加不同比例(0、4%、10%m/m)大豆分离蛋白(soy protein isolate,SPI)制作混合型干酪。完全成熟之后利用固相微萃取(SPME)萃取富集干酪挥发性物质、气相色谱-质谱联用(GC/MS)检测干酪风味物质。以研究添加大豆分离蛋白对干酪风味物质的影响,确定适宜添加比例。实验结果表明:干酪中主要风味物质是酸类,其次是酮,醇,醛,酯类化合物;添加大豆分离蛋白使干酪中酸类、酮类化合物种类及含量明显减少;醇类化合物增加。大豆分离蛋白添加比为4%时,干酪有浓郁的奶香及黄油香气,羊乳膻味减少,并检出苯酚、吡咯等化合物,提高了干酪风味物质种类的丰富性。     

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.     

Functional properties of native and cheese whey protein concentrate powders

The objective of this study was to compare microfiltered native whey protein concentrate and traditional cheese whey protein concentrate powders and their functional properties. Solubility, viscosity, gelation, foaming properties, emulsification and water-holding capacity were studied. The effect of spray and freeze drying methods on functional properties was evaluated. Gel strength varied from 0.11 to 0.65 N. Foaming stability and overrun varied from 0 to 29.3 min and from 230 to 2200%, respectively. Foaming and gelation properties were clearly better with native whey protein powders. Differences between drying methods were not observed but higher heat load decreased solubility.     

The influence of milk powder characteristics on the properties of halloumi cheese made from recombined milk*

The properties of halloumi made from recombined milks that had been prepared using milk powders processed by different methods were investigated. With skim milk powder, decreases in heat treatment of the liquid skim before drying were found to improve the stretch and melt properties of the cheese. In contrast, the level of solids in the skim concentrate before drying had no effect on the cheese characteristics. Ultrafiltration was also used to concentrate milk for spray drying. The resultant powder was recombined to give protein levels equivalent to that of normal milk and to that of milk concentrated fivefold. In both cases the recombined milks could be converted into high quality halloumi.     

Changes of organic acids,volatile aroma compounds and sensory characteristics of Halloumi cheese kept in brine

This study examines the changes in organic acids, volatile aroma compounds and sensory characteristics of ovine Halloumi cheese kept in brine (∼10% NaCl) at 4 °C for 45 days. The highest total score of the organoleptic assessment was observed at day 1, before storage in brine. During cheese storage, a large reduction of lactose was observed, especially in the first stages of storage while, concurrently, a significantly progressive increase in lactic and acetic acids was observed. Among the volatile aroma compounds determined were alcohols, aldehydes, ketones, acids, esters, hydrocarbons, sulphur compounds, as well as a variety of other compounds in very small quantities. Ethanol and acetic acid were the dominant volatile aromatic compounds and their concentrations increased during storage. The lipolysis of Halloumi cheese during storage was not excessive. The dominant free fatty acids were palmitic, oleic and acetic.     

Comparison of the volatile composition and sensory characteristics of Spanish PDO cheeses manufactured from ewes’ raw milk and animal rennet

Idiazabal, Manchego, Roncal and Zamorano varieties are the Spanish cheeses manufactured under Protected Denomination of Origin (PDO) from ewes’ raw milk and coagulated with animal rennet. Two batches of each cheese variety were ripened for six months and the cheeses were compared for sensory characteristics and composition of volatile compounds. Seventy-six volatile compounds were identified by GC-MS analysis of headspaces of the cheeses. The volatile profile of the four PDO cheeses differed significantly. Acids were the most abundant volatile compounds in Idiazabal, Roncal, and Zamorano cheeses, whereas alcohols were the main volatile compounds in Manchego cheese due to the large percentage of 2-butanol. Aldehydes, ketones and esters were minor compounds in all the cheese varieties, whereas terpenes and unsaturated hydrocarbons were only found in Manchego cheese. The sensory profiles, of the four PDO cheeses also differed significantly. The highest scores for sharp, brine and rennet odours, and rancid and rennet flavours were assessed in Idiazabal and Zamorano cheeses, whereas milky and buttery odour scores were higher in Manchego, Roncal and Zamorano cheeses than in Idiazabal cheese. Principal component analysis was applied to sensory attributes and volatile composition of the cheeses. Differences in flavour and odour attributes were correlated with differences in the volatile compounds. Two principal components correlating sensory attributes and volatile compounds were defined as “strength factor” and “sweetness factor”. The “strength factor” distinguished among the four cheese varieties, except between Roncal and Manchego cheeses, and the “sweetness factor” distinguished the Zamorano cheese from the Idiazabal, Manchego and Roncal cheeses.     

SPME-GC/MS测定再制干酪中的风味物质

利用固相微萃取法（SPME）富集，GC／MS分离与检测技术，研究了再制干酪加工过程对其挥发性风味化合物的影响。共鉴定出73种挥发性化合物，其中在1个月及5个月成熟期的切达干酪中分别鉴定出了41和43种挥发性化合物．在再制干酪产品中鉴定出44种化合物，其中原料干酪和再制干酪中同时拥有的化合物有35种。通过对加工前后挥发性风味化合物的变化推断，在再制干酪加工前后挥发性风味化合物的变化对产品风味强度的减弱没有显著影响。     

Characterization of aromatic properties of old-style cheese starters

Old-style cheese starters were evaluated to determine their ability to produce cheese aroma compounds. Detailed analyses of the aroma-producing potential of 13 old-style starter cultures were undertaken. The proteolytic profile of the starters was established by an accelerated ripening study using a model cheese slurry and compared with those of a commercial aromatic starter and commercial Cheddar cheeses. To evaluate the aromatic potential of the starter cultures, quantification of free amino acids liberated and volatile compounds after 15 d of ripening at 30°C as well as sensory analysis were carried out. Results showed that proteolysis patterns of all 13 starter cultures in the curd model were comparable to those of commercial Cheddar cheeses. All tested cultures demonstrated the ability to produce high amounts of amino acids recognized as precursors of aroma compounds. Several differences were observed between the starters and commercial Cheddar cheeses regarding some amino acids such as glutamate, leucine, phenylalanine, proline, and ornithine, reflecting the various enzymatic systems present in the starters. Starters Bt (control) and ULAAC-E exhibited various significant differences regarding their free amino acid profiles, as confirmed by sensory analysis. In addition, identification of volatile compounds confirmed the presence of several key molecules related to aroma, such as 3-methylbutanal and diacetyl. Besides the aroma-producing aspect, 2 starters (ULAAC-A and ULAAC-H) seem to possess an important ability to generate large amounts of γ-aminobutyric acid, which contributed up to 15% of the total amino acids present in the model curd after 15 d ripening. γ-Aminobutyric acid is an amine well-known for its antihypertensive and calming effects.     

Effects of using whey and maltodextrin in white cheese powder production on free fatty acid content,nonenzymatic browning and oxidation degree during storage

Use of maltodextrin and whey improves the physical properties of spray-dried cheese powder and, as cheese replacers, they decrease the raw material costs. However, it is necessary to evaluate their effects on the chemical quality and sensory properties of the product. Three powders, control (CON), whey-added cheese powder (WACP), and maltodextrin-added cheese powder (MACP) were produced to determine free fatty acid (FFA) content, degree of nonenzymatic browning, oxidation, and sensory (flavour) changes during 12 months' storage. In the emulsion preparation and drying process, total volatile FFAs decreased up to 9% and 53.5%, respectively, with higher decrease in CON than in WACP or MACP. Although whey increased oxidation degree of powder, oxidised flavour could not be perceived until the ninth month of storage. Maltodextrin slightly decreased cheese flavour and overall impression scores. There was no difference detected in the powders for scorched flavour.     

益生性植物乳杆菌对切达干酪挥发性风味形成的影响

将分离自西藏灵菇的益生性植物乳杆菌1-2通过在杀菌乳中添加活菌数8.0、9.0（lg（CFU/mL））和在排乳清后添加于凝乳块8.0（lg（CFU/g））的方式分别加入到切达干酪中,考察植物乳杆菌活菌数量、添加方式和成熟时间对干酪挥发性风味物质组成的影响。利用固相微萃取和气相色谱-质谱联用技术检测出对照组干酪的风味物质26种,益生菌干酪组风味物质30种,添加植物乳杆菌1-2可产生乙苯、十二烷、己醇和丙酮4种挥发性风味物质。成熟时间对干酪风味的影响最大,随成熟时间的延长,益生菌干酪组中苯含量显著增加,而对照组干酪在成熟12周时才检测到苯。益生菌添加量和添加方式对干酪挥发性风味的影响相似,丁酸受益生菌活菌数和添加方式的影响最大,益生菌干酪组成熟12周时,丁酸含量最高达对照组的3.96倍（P＜0.05）。在杀菌乳中添加益生菌活菌数8.0（lg（CFU/mL））组和9.0（lg（CFU/mL））组干酪中挥发性风味物质含量有显著差异,但在杀菌乳中添加高活菌数9.0（lg（CFU/mL））和在排乳清后添加低活菌数8.0（lg（CFU/g））于凝乳块中对干酪挥发性风味的形成具有相似的影响。本研究结果为改进益生菌干酪的加工工艺和风味品质提供了实验依据。     

Proteolysis and volatile profile in the Algerian traditional Bouhezza cheese made using raw goat’s milk

Bouhezza is an Algerian cheese, which is ripened in a goat-skin bag, called Chekoua. The aim of the study was to determine the protein profiles and aromatics, which contribute to sensory properties of Bouhezza cheese. The chemical composition, proteolysis, and volatile profile have been carried out in cheese made from raw goat milk. The results showed that, the dry matter ranged from 23.07 to 51.95%, the fat-in-dry matter ranged from 10.58 to 31.77%, and the protein ranged from 28.27 to 42.09%. Water-soluble and 12% trichloroacetic acid-soluble nitrogen fractions decreased at the beginning of the ripening process and then they increased until the end of ripening. The reverse phase-high-performance liquid chromatography peptide profiles of the cheese showed the modifications occurred during the ripening process. The volatile compounds showed a diversity of odorous components which contribute to give to the cheese its particular organoleptic. There were 109 compounds identified in Bouhezza cheese. Carboxylic acids, esters, and alcohols were the main classes of the volatile components in the cheese.