产脂肪酶乳酸菌对新疆传统奶酪脂肪酸及风味的影响

为了改善奶酪品质,奶酪生产过程中通常会添加脂肪酶或者产脂肪酶乳酸菌来提升产品品质。该研究以前期筛选的4株高产脂肪酶乳酸菌为发酵剂,分别随机选取3株乳酸菌复配制作酸凝奶酪。试验组：A组T1-5和T1-3属融合魏斯氏菌（Weissella confusa）、H1-6属瑞士乳杆菌（Lactobacillus helveticus）,B组H1-6、T1-5、B2-5属植物乳杆菌（Lactobacillus plantarum）,C组H1-6、T1-3、B2-5,D组T1-3、T1-5、B2-5,对照组（E组）（添加商业发酵剂）,分析发酵剂对传统奶酪pH值、滴定酸度和脂肪氧化情况的影响,并利用气相色谱法（Gas Chromatography,GC）检测奶酪中脂肪酸变化、利用气相色谱-离子迁移谱（Gas Chromatography-Ion Mobility Chromatography,GC-IMS）分析奶酪中风味物质的变化。结果表明：A,B,C,D组4组奶酪的pH值、过氧化值（Peroxide value,POV值）明显低于E组（对照组）（P < 0.05）,A,B组奶酪滴定酸度比对照E组高（P < 0.05）;A,B,C,D组奶酪中饱和脂肪酸（Saturated Fatty Acids,SFA）含量、单不饱和脂肪酸（Monounsaturated Fatty Acids,MUFA）含量和多不饱和脂肪酸（Polyunsaturated Fatty Acids,PUFA）含量均显著高于E组（P < 0.05）;4个试验组样品中亚油酸（C18∶2n6c）含量明显高于对照组（E组）（P < 0.05）。GC-IMS及主成分分析结果显示,A、B组奶酪挥发性风味物质种类多,且相似度较高,其中2-庚酮、丁醛、乙酸丁酯是主要呈味物质;C、E两组奶酪中风味物质比较相似,风味物质主要以乙酸乙酯、乙酸丙酯、己酸乙酯等酯类为主;D组与其他4组有所差异,主要挥发性风味物质为乙酸丁酯、3-辛酮、庚醛等。结合感官评定,A、B两组奶酪整体风味和口感较好,评分较高。筛选得到的产脂肪酶乳酸菌可以作为发酵剂用于提升新疆传统奶酪品质。     

Removal of cholesterol from Cheddar cheese by beta-cyclodextrin

This study was carried out to determine the cholesterol removal rate and resulting changes in flavor, fatty acid and bitter amino acid production in reduced-cholesterol Cheddar cheese, made by cream separation followed by 10% beta-cyclodextrin (beta-CD) treatment. The cholesterol removal from the cheese was 92.1%. The production of short-chain free fatty acids (FFAs) increased the ripening time in control and cream-treated cheeses. The quantity of short-chain FFAs released between treatments during ripening was different, while not much difference was found in the production of neutral volatile compounds in the samples. Reduced-cholesterol cheese produced much higher levels of bitter amino acids than the control. In sensory analysis, the texture score of control Cheddar cheese increased significantly with ripening time; however, that of the cream treatment group decreased dramatically with ripening time. On the basis of our results, we conclude that the cheese made from beta-CD-treated cream had a higher rate of cholesterol removal and ripened rapidly.     

Differential characteristics of fatty acids in cheese from milk of various animal species by capillary gas chromatography

The kind of milk used in the manufacture of cheese has been identified by analysis of the fatty acids. The milk fat is extracted from the cheese and saponified. The methyl esters of the fatty acids are prepared and determined by capillary column gas chromatography. Seven major fatty acids are separated and quantitated, namely, C8:0, C10:0, C12:0, C14:0, C16:0, C18:0, and C18:1. Many of the 21 simple ratios that can be formed from these 7 quantities are characteristic of the type of milk from which the fatty acids were obtained. The method allows the identification of cheese prepared with the milk of cows, buffalo, sheep, or goats. Substitution or adulteration of milk can also be detected.     

Rheological and proteolytic properties of Monterey Jack goat's milk cheese during aging

To enhance the understanding of the quality traits of goat's milk cheeses, rheological and proteolytic properties of Monterey Jack goat's milk cheese were evaluated during 26 weeks of 4 degrees C storage. As expected with aging, beta-casein levels decreased with concomitant increases in peptide levels and were correlated with changes in rheological properties of the cheese. Hydrolysis of the protein matrix resulted in more flexible (increased viscoelastic properties) and softer (decreased hardness, shear stress, and shear rigidity) cheeses. During the first 4-8 weeks of storage, cheese texture changed significantly (P < 0.05) and then stabilized. Characterization of rheological and proteolytic properties of the goat's milk semihard cheese during aging provided insight into the changes occurring in the protein matrix, the relationship to structure, and a shift in cheese quality.     

Fatty acids including trans content of commercial bakery products manufactured in Spain.

Fifteen samples of the most common industrial bakery products sold in Spain were analyzed for their fatty acid composition. Saturated fatty acids occurred in the largest proportions in all samples (mean = 52.8%), followed by monounsaturated (mean = 23.5%) and polyunsaturated fatty acids (mean = 17.2%). A small percentage of trans fatty acids, which were found in all samples, showed a mean value of 5.7%. According to their fatty acid composition, that is, their saturated, monounsaturated, and polyunsaturated fatty acid contents, the statistical analysis (discriminant analysis) showed three groups of samples, suggesting that the fat incorporated in these samples was obtained from different sources.     

trans-C18:1 isomers in cheeses enriched in unsaturated fatty acids and manufactured with different milk fat globule sizes

Increasing the knowledge on dietary fat composition, mainly the minor components, will improve the nutritional value of foods and their labeling. In this study, we examined the trans-octadecenoic acid (C18:1) composition of Emmental cheeses enriched in unsaturated fatty acids (FA) and manufactured with milks produced by cows selected to produce small and large fat globules. The FA composition of the milks was not significantly ( P > 0.05) different from the FA composition of the corresponding Emmental cheeses. Increasing the unsaturated FA content of the cheeses using dietary manipulations lead to an increase in the trans-C18:1 and changed their isomeric profiles. In milk fat produced with the linseed-enriched diet, the trans-10 C18:1 concentration was greater than trans-11 C18:1 (vaccenic acid), which is classically the major trans-C18:1 in milk fat. The content in trans-C18:1 and more particularly in trans-10 C18:1 was negatively correlated with the size of fat globules ( r (2) = 0. 82 and 0.87, respectively) and related to milk fat depression. The trans-C18:1 content was negatively correlated with the saturated FA (slope = -0.35; r (2) = 0.81) and positively correlated with the unsaturated (slope = 0.29; r (2) = 0.85) and monounsaturated (slope = 0.32; r (2) = 0.81) FA. Focusing on the health-related considerations of fat in food products, further nutritional studies are needed to elucidate the role of trans-C18:1 isomers.     

Hydrocarbon and fatty acid composition of cheese as affected by the pasture vegetation type

The determination of the geographical origin of dairy products is an ongoing issue. In this paper the effects of botanical diversity of two pastures on the hydrocarbon and fatty acid composition of cheese fat were studied, over 2 years of experimentation. Two areas in the Italian southwestern Alpine region, dominated by Trifolium alpinum (T) and Festuca nigrescens (F) vegetation, respectively, were chosen, and milk obtained from cows grazing on these pastures was used to produce a semihard traditional cheese. Cheese samples showed a significantly different composition of most linear hydrocarbons, odd-chain (C15, C17, and C17:1) and unsaturated (trans-11,cis-15-C18:2, C18:3, C20:4n-6, C20:4n-3, and 20:5n-3) fatty acids, according to pasture type. The ratio between C(29) and C(27) linear hydrocarbons, unlike the absolute content of the single molecules, showed a good discriminating ability between the two pastures and was little affected by the natural variability due to the climatic and environmental factors.     

Aroma compounds of fresh milk from New Zealand cows fed different diets

Volatile compounds were extracted from fresh milk produced by New Zealand cows using the newly developed solvent-assisted flavor evaporation (SAFE) technique. The two samples that were used came from cows that had been fed on different diets and represented the considerably different flavors of Northern hemisphere and New Zealand milk. Using gas chromatography-olfactometry (GC-O), 71 aroma compounds were found from the milk extracts, 66 of which were identified. Nearly all of the aroma compounds were common to both extracts, despite the two milk samples having quite different flavors. Only one compound, gamma-12:2 lactone, was significantly odor-active for the extract of milk from cows fed a supplement diet, but was not found for the extract of milk from cows fed a pasture diet. Thus, differences in milk flavor are primarily caused by concentration differences of a common set of flavor compounds, rather than by the occurrence of compounds uniquely associated with a particular feed.     

Starter bacteria are the prime agents of lipolysis in cheddar cheese

To assess the contribution of starter lactic acid bacteria (LAB) to lipolysis in Cheddar cheese, the evolution of free fatty acids (FFAs) was monitored in Cheddar cheeses manufactured from pasteurized milks with or without starter. Starter-free cheeses were acidified by a combination of lactic acid and glucono-delta-lactone. Starter cultures were found to actively produce FFAs in the cheese vat, and mean levels of FFAs were significantly higher in starter cheeses over ripening. The contribution of nonstarter LAB toward lipolysis appears minimal, especially in starter-acidified cheeses. It is postulated that the moderate increases in FFAs in Cheddar cheese are primarily due to lack of access of esterase of LAB to suitable lipid substrate. The results of this study indicate that starter esterases are the primary contributors to lipolysis in Cheddar cheese made from good quality pasteurized milk.     

Multiscale characterization of the organization of triglycerides and phospholipids in emmental cheese: from the microscopic to the molecular level

The chemical composition and properties of lipids, both triglycerides and phospholipids, play a major role in the functional and nutritional properties of food products. In this study, the suprastructure of fat, solid fat content, and crystallographic properties of triglycerides were investigated in hard-type cheeses from the microscopic scale to the molecular level using the combination of relevant techniques. Two industrial cheeses with different oiling off properties were compared with experimental cheeses manufactured in the laboratory. Microstructural analysis performed using confocal laser scanning microscopy showed that milk processing led to the disruption of fat globules with the formation of nonglobular fat. For a similar fatty acid composition, oiling off was mainly related to the fat in dry matter content and to the suprastructure of fat in cheese. An exogenous fluorescent phospholipid permitted the localization of milk phospholipids in the cheese matrix, which mainly remain around fat inclusions after disruption of the milk fat globule membrane, and to show heterogeneities. We also showed using differential scanning calorimetry that the suprastructure of fat did not affect the solid fat content in cheese at 4 degrees C: 71.6 +/- 4.9%. The organization of triglyceride molecules in fat crystals, elucidated at a molecular level using X-ray diffraction, corresponded to the coexistence of 2 lamellar structures (2L 40.5 angstroms and 3L 54.6 angstroms) with four polymorphic forms: alpha, two beta' and beta. A schematic representation of the multiscale organization of triglycerides and phospholipids in cheese is proposed.     

The addition of Propionibacterium freudenreichii to Raclette cheese induces biochemical changes and enhances flavor development

Two mixtures of Propionibacterium freudenreichii commercial strains were tested as adjunct cultures in pasteurized milk Raclette cheese to investigate the ability of propionibacteria (PAB) to enhance flavor development. Cheese flavor was assessed by a trained sensory panel, and levels of free amino acids, free fatty acids, and volatile compounds were determined. The PAB level showed a 1.4 log increase within the ripening period (12 weeks at 11 degrees C). Eye formation, which was not desired, was not observed in PAB cheeses. PAB fermented lactate to acetate and propionate and produced fatty acids by lipolysis, branched chain volatile compounds derived from isoleucine and leucine catabolism and some esters. One of the experimental cheeses received the highest scores for odor and flavor intensity and was characterized by higher frequencies of detection for some minor notes ("propionic"and "whey" odor, "sweet" taste). PAB can therefore be considered as potential adjunct cultures to enhance or modify cheese flavor development.     

Key odorants of Oscypek, a traditional Polish ewe's milk cheese

The unique flavor of Oscypek, a Polish ewe's milk smoked cheese, is described as slightly sour, piquant, salted, and smoked. In this paper with the application of gas chromatography-olfactometry (GC-O) and combination of aroma extract dilution analysis (AEDA) 20 potent odorants of this cheese have been identified within the flavor dilution factor (FD) range of 4-2048. Among them, 2-methoxyphenol, 2-methoxy-4-methylphenol, 4-methylphenol, and butanoic acid showed the highest FD factors. Quantification results based on labeled standard addition followed by calculation of odor activity values (OAV) of 13 compounds with the highest FD factors revealed that 11 compounds were present at concentrations above their odor threshold values and therefore mostly contribute to the overall aroma of smoked ewe's milk cheese. Six of those compounds were represented by phenolic derivatives, with the highest OAV for 2-methoxyphenol (1280). Analysis of key odorants of an unsmoked cheese sample showed that the smoking process had a fundamental influence on Oscypek aroma formation.     

Complex viscosity induced by protein composition variation influences the aroma release of flavored stirred yogurt

Dairy protein composition is known to influence the structure and the texture characteristics of yogurt. The objective of the present work was therefore to investigate the impact of protein composition, at a constant protein level, on the physicochemical properties of 4% fat flavored stirred yogurt and, more specifically, on the rheological properties, the microstructure, and the aroma release. The results showed that caseinate-enriched yogurt generally presented changes in their microstructure network and had a higher complex viscosity than whey protein-enriched yogurt. To a lesser extent, the release of the majority of aroma compounds was lower in caseinate-enriched yogurt. It was therefore possible to quantify physicochemical interactions between aroma compounds and proteins. The influence of gel structure on the flavor release was observed and was in agreement with sensory characteristics previously studied for these products.     

Phospholipid, sphingolipid, and fatty acid compositions of the milk fat globule membrane are modified by diet

The phospholipid and sphingolipid composition of milk is of considerable interest regarding their nutritional and functional properties. The objective of this article was to determine the lipid composition of the milk fat globule membrane (MFGM) of milk from cows fed a diet rich in polyunsaturated fatty acids. The experiments were performed with 2 groups of 6 cows feeding on (i) maize silage ad libitum (+ grassland hay, mixture of cereals, soyabean meal) or (ii) the maize silage-based diet supplemented with extruded linseed (bringing a lipid proportion of 5% of dry matter). The phospholipid and sphingolipid composition of the MFGM was determined using HPLC/ELSD. The fatty acid (FA) composition of total lipids and phospholipids was determined using GC. As expected, the linseed-supplemented diet decreased the saturated FA and increased the unsaturated FA content in milk fat. MFGM in milk from cows fed the diet rich in polyunsaturated FA resulted in (i) a higher amount of phospholipids (+ 18%), which was related to a smaller size of milk fat globules (ii) an increase of 30% (w/w) of the concentration in sphingomyelin, (iii) a higher content in stearic acid (1.7-fold), unsaturated FA (1.36-fold), and C18:1 trans FA: 7.2 +/- 0.5% (3.7-fold). The MFGM contained a higher concentration of unsaturated FA (C18:1, C18:2, and C18:3) and very long-chain FA (C22:0, C23:0, C24:0, EPA, DHA) compared with total lipids extracted from milk. The technological, sensorial, and nutritional consequences of these changes in the lipid composition of the MFGM induced by dietary manipulation remain to be elucidated.     

Fatty acid composition of traditional and novel forages

Managing the fatty acid composition of grazing ruminant diets could lead to meat and milk products that have higher conjugated linoleic acid (CLA) concentrations, but forage fatty acid dynamics must be more fully understood for a range of forages before grazing systems can be specified. The fatty acid profiles of 13 different forages, including grasses, legumes, and forbs, grown under greenhouse conditions, were determined. Three separate harvests, at 3-week intervals, were made of each plant material. alpha-Linolenic [C18:3, 7.0-38.4 mg g(-1) of dry matter (DM)], linoleic (C18:2, 2.0-10.3 mg g(-1) of DM), and palmitic (C16:0, 2.6-7.5 mg g(-1) of DM) acids were the most abundant fatty acids in all species at each harvest, together representing approximately 93% of the fatty acids present. Concentrations of fatty acids declined as plants developed, but the fractional contribution of each fatty acid to total fatty acids remained relatively stable over time. Grasses had a uniform composition across species with a mean of 66% of total fatty acids provided by C18:3, 13% by C18:2, and 14% by C16:0. The fractional contribution of C18:3 to total fatty acids was lower and more variable in forbs than in grasses. Intake of fatty acid by grazing ruminants would be affected by the forage species consumed.     

Vitamin D3 fortification, quantification, and long-term stability in Cheddar and low-fat cheeses

Considering the widespread insufficiency of vitamin D, the fortification of additional foods with vitamin D is warranted. The objective of this research was to assess the feasibility of vitamin D3 fortification in natural hard cheeses. We examined the recovery, distribution, long-term retention, and heat stability of the vitamin in industrially made fortified Cheddar and low-fat cheeses. The results indicated that the vitamin D3 did not degrade during processing, over 1 year of ripening (3-8 degrees C), or after thermal treatment at 232 degrees C for 5 min. Vitamin D3 recovery in the fortified Cheddar and low-fat cheeses were, respectively, 91 and 55% of the vitamin D3 added to the milk used to make each cheese. The remaining vitamin D3 was entrained in the whey. The vitamin D3 was uniformly distributed throughout the blocks of cheese. The fortification process did not alter the yield, chemical composition, or flavor of the Cheddar cheese. We conclude that industrially manufactured Cheddar and low-fat cheeses are suitable for vitamin D3 fortification.     

Relevance of isotopic and molecular biomarkers for the authentication of milk according to production zone and type of feeding of the cow

The first objective of the present paper was to assess the potential of both isotopic ( (18)O/ (16)O in milk water) and molecular biomarkers (terpenes, fatty acids, carotenoids, and vitamins) and milk color to discriminate the production zone (lowland or upland areas) from which 49 tanker bulk milks were collected over one year from a total of 204 farms. The milk water (18)O enrichment was higher in lowland (<500 m altitude) than in upland (>700 m altitude), but the delta (18)O values failed to discriminate systematically the production zone at the scale of the year because of its high variability related to the sampling period. In contrast with vitamins A and E, carotenoids, and milk color measurements, terpenes and fatty acids were confirmed to be relevant tracers of the production zone. The milk compounds with the strongest discriminative potential were fatty acids, which were determined by high-resolution gas chromatography. The calculation of fatty acid ratios, which permits the limitation of using fatty acid relative quantity expressed in percentage of total fatty acids to be overcome, was shown to be particularly relevant in discriminating upland from lowland milk ratios. The selection of two pairs of ratios, namely, iso-C17:0/C18:3 n-3 and iso-C15:0/iso-C14:0, enabled the authentication of 100% of the highland versus lowland milks whatever the season. The second objective was to evaluate the relevance of fatty acid composition to discriminate milks according to the proportion of corn silage in the diets of dairy cows. The selection of two fatty acids ratios, namely, trans11 cis15-C18:2/trans11-C18:1 and cis9-C16:1/iso-C16:0, enabled the correct classification of 100% of the milk samples according to the proportion of corn silage in the basic fodder rations (<25% vs >30%). The relationship between the milk production zone and the type of forage fed to the cows is discussed.     

Residues of spinosad in meat, milk, and eggs

Spinosad is an insect control agent that is derived from a naturally occurring soil bacterium and has a high level of activity against insects that infest a variety of crops. Dairy and poultry feeding studies were conducted to determine the magnitude of spinosad residues in animal products that would result from the consumption of typical feed commodities containing residues of spinosad. Dairy cows were dosed for 28 days with spinosad at rates equivalent to 0, 1, 3, and 10 microg/g in the diet. Chicken hens were dosed for 42 days with spinosad at rates equivalent to 0, 0.1, 0.3, 1, and 5 microg/g in the diet. Milk, eggs, and tissue samples were analyzed by high-performance liquid chromatography and/or immunoassay methods. Spinosad residues occurred in all of the sample types but were lowest in eggs, skim milk, and lean meat and were highest in the fat.     

Conjugated linoleic acid content and organoleptic attributes of fermented milk products produced with probiotic bacteria

The effect of probiotic bacteria on the formation of conjugated linoleic acid (CLA), microbial growth, and organoleptic attributes (acidity, texture, and flavor) of fermented milk products was determined. Four probiotic bacteria, Lactobacillus rhamnosus, Propionibacterium freudenreichii subsp. shermanii 56, P. freudenreichii subsp. shermanii 51, and P. freudenreichii subsp. freudenreichii 23, were evaluated individually or in coculture with traditional yogurt cultures (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus). The lipid source was hydrolyzed soy oil. L. rhamnosus, in coculture with yogurt culture, resulted in the highest content of CLA. Growth and CLA formation of propionibacteria were enhanced in the presence of yogurt cultures. Texture and flavor attributes of fermented milks produced with propionibacteria were significantly different than the fermented milks processed with yogurt cultures. The fermented milks processed with probiotic bacteria in coculture with yogurt cultures demonstrated similar acidity, texture, and flavor as the fermented milk produced with yogurt cultures.