Primary and Secondary Proteolysis in Eleven Turkish Cheese Varieties

Levels of proteolysis of 75 samples belonging to 11 Turkish cheese varieties, including Civil, Canak, Dil, Divle Tulum, Ezine, Hellim, Malatya, Mihalic, Orgu, Urfa, and Van Otlu, were comparatively studied. The cheeses were mainly produced using traditional methods; however, some varieties were industrially produced. Chemical composition and the levels of soluble nitrogen fractions of the cheeses varied depending on the cheese variety. Gel electrophoresis of the cheeses showed that the samples presented different gel patterns with α_s1-casein being extensively degraded in many cheeses; whereas the hydrolysis of α_s1-casein in Malatya and Hellim was observed to be limited. Peptide profiles by RP-HPLC of the water-soluble fractions were largely different for many of the samples, but some similarities were visualized. Multivariate analysis of the RP-HPLC data grouped the cheeses according to their peptide profiles. The results suggested that each variety of cheese had different levels of proteolysis. The manufacturing technique and ripening conditions employed have played a determinative role on the proteolytic patterns of the cheeses analyzed.     

Characterization and Comparison of Free Fatty Acid Profiles of Eleven Varieties of Turkish Cheeses

Free fatty acids profiles of 11 different cheese varieties sold in Turkey were determined to assess the development of lipolysis. Results obtained showed that the concentrations of short chain fatty acids (C₄ and C₆ free fatty acids) were close in all cheeses (P > 0.05), except for Canak cheese. However, significant differences were noted among the samples for other free fatty acids including C₈ to C_18:2 (P < 0.05). Palmitic (C₁₆) and oleic (C_18:1) acids were the most abundant free fatty acids in all cheese samples. Principal component analysis was applied to simplify interpretation of the data and distinguish the variety of the cheeses on the plot. Canak cheese gave a dramatically different free fatty acid profile from the other cheeses, probably because of the fact that ripening of this variety is achieved in the earthenware pots for about 1 year. Van Otlu (ripened with special herbs) and Civil (ripened by spontaneously molding on its surface) cheeses differed from the others by ANOVA and principal component analysis techniques. In conclusion, the degree of lipolysis in the cheeses could be classified into extreme (Canak), high (Civil, Divle Tulum, Mihalic, and Van Otlu), mild (Ezine, Orgu, and Urfa), and low (Dil, Hellim, and Malatya) based on their FFA profiles.     

Microbiology, biochemistry, and volatile composition of Tulum cheese ripened in goat's skin or plastic bags

Tulum cheeses were manufactured from raw ewe's milk and ripened in goat's skin bags (tulums) or plastic containers to understand the effect of ripening container on the chemical composition, biochemistry, microbiology, and volatile composition of Tulum cheeses during 150 d of ripening. Chemical compositions of the cheeses ripened in tulums were significantly different and the moisture contents decreased rapidly in those cheeses because of the porous structure of the tulum. Higher microbial counts were detected in the cheeses ripened in plastic than in cheeses ripened in tulums. Differences in nitrogenous compounds and total free AA of the cheeses were not significant. Total concentrations of free AA in cheeses increased with age and Glu, Ala, Val, Leu, and Phe were the most abundant AA in the cheeses. Urea-PAGE of pH 4.6-insoluble fractions of the cheeses during ripening showed similar degradation patterns in all cheeses. Peptide profiles by reversed-phase HPLC of pH 4.6- and ethanol-soluble or ethanol-insoluble fractions of the cheeses revealed only minor differences in the concentrations of some peptides among the cheeses; however, age-related changes in peptide concentrations were significantly different among the cheeses. Cheeses were analyzed at 90 d of ripening for volatile compounds by solid-phase microextraction gas chromatography-mass spectrometry. One hundred volatile components were identified, including 11 acids, 16 esters, 12 methyl ketones, 7 aldehydes, 22 alcohols, 7 sulfur compounds, 6 terpenes, and 19 miscellaneous compounds. The main components were short-chain fatty acids, 2-butanone, diacetyl, and primary alcohols. Quantitative differences in several volatile compounds were evident among the cheeses. Cheeses ripened in tulums or plastic had similar aroma patterns, but the concentrations of some components were different.     

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.     

Effects of Wild-Type Starter Culture (Artisanal Strains) on Volatile Profile of Urfa Cheese Made from Ewe Milk

In the present study, the development of volatile flavor compounds in sheep’s milk Urfa cheese made by using three different combinations of wild-type strains including Lactococcus lactis subsp. lactis 1B4, Lactococcus garvieae IMAU 50157, Enterococcus faecium ATCC 19434, Enterococcus durans IMAU 60200, and Enterococcus faecalis KLDSO.034 was investigated over 180 days. Three batches of cheese were made using above strains as follows: Cheese A (strains ATCC 19434+1B4+IMAU 50157); Cheese B (strains IMAU 60200+ATCC 19434+1B4); Cheese C (strains KLDSO.034+ IMAU 60200+ ATCC 19434+1B4+ IMAU 50157). The fourth batch was produced from raw sheep’s milk as control (Cheese D). The volatile compounds were identified using a gas chromatography/mass spectrometry system combined with solid-phase microextraction. In total, 70 volatile compounds were recovered from the cheeses including 10 alcohols (mainly ethanol, 2-methyl-1-propanol, 3-methyl-1-propanol), 20 aldehydes and ketones (mainly 2-pentanone, 2-heptanone), 11 esters (mainly ethyl acetate), 10 acids (mainly acetic acid, 2-hydroxy-4-methyl pentanoic acid), 6 terpenes (mainly α-pinene), and 13 miscellaneous compounds (mainly 3,7-dimethyl-1,6-octadiene). While total aldehydes concentration in the control cheese was higher than those made from combinations of wild-type strains (Cheeses A to C), the concentration of alcohols was lower in the former sample. Regarding other volatile compounds there was no clear differences between the cheeses. Results showed that strain combination A or C (Cheese A or C, respectively) could be employed in the manufacture of Urfa cheese made from pasteurized sheep’s milk. However, to reach a fair judgement on the proper strain combination for Urfa cheese, aroma profile (i.e., active compounds) released by the strains should be laid open in detail.     

Chemical and microbiological status and volatile profiles of mouldy Civil cheese,a Turkish mould‐ripened variety

The objective of this study is to characterise the gross chemical and microbiological status and identify the volatile compounds of mouldy Civil cheeses. A total of forty‐one samples were surveyed, and gross compositional status of the cheeses was (as mean values): 6.5 for pH, 6.2% for fat‐in‐dry matter, 51.8% for moisture and 15.3% for water‐soluble nitrogen (as% of total nitrogen). Chemical composition of the cheese samples varied widely. Mouldy Civil cheese has similar pH values and moisture contents when compared with blue‐type cheeses, but it has distinct feature for fat contents. The microbiological counts of the samples were found to be high and some samples contained coliform bacteria. A total of 95 volatiles, including esters (28), acids (6), ketones (12), aldehydes (3), alcohols (15), terpenes (10), sulphur compounds (3) and miscellaneous (18), were identified in the volatile fractions of the cheeses, and principal volatile groups were esters, alcohols and ketones.     

Effect of Penicillium roqueforti and incorporation of whey cheese on volatile profiles and sensory characteristics of mould‐ripened Civil cheese

In this study, four different types of mould‐ripened Civil cheese were manufactured. A defined (nontoxigenic) strain of a Penicillium roqueforti (SC 509) was used as secondary starter for the manufacture of mould‐ripened Civil cheese with and without addition of the whey cheese Lor; in parallel, secondary starter‐free counterparts were manufactured. A total of 83 compounds were identified. Ketones, alcohols and esters were the principal classes of volatile components. Principal component analysis of the headspace volatiles grouped cheeses by age and type. P. roqueforti inoculated cheese was clearly separated from the other cheeses at 180 days of ripening, and these cheeses were characterised with high levels of ketones (e.g., 2‐butanone, 2‐heptanone). Differences in the panel scores between the cheese samples were not significant during the first stage of ripening (up to 60 days); as ripening proceeded, these differences were become evident and P. roqueforti inoculated cheeses received higher scores than others. Addition of Lor in the manufacture of mould‐ripened Civil cheese caused lower points by the sensory panel, and the cheese inoculated with P. roqueforti and Lor‐free was the best type of mould‐ripened Civil cheese. The results showed that the use of P. roqueforti in the manufacture of mould‐ripened Civil cheese has significant impact on the volatile profiles and sensory attributes.     

Influence of ripening temperature on the volatiles profile and flavour of Cheddar cheese made from raw or pasteurised milk

Cheddar cheeses were made from raw (R1, R8) or pasteurised (P1, P8) milk and ripened at 1°C (P1, R1) or 8°C (P8, R8). Volatile compounds were extracted from 6 month-old cheeses and analysed, identified and quantified by gas chromatography-mass-spectrometry. A detailed sensory analysis of the cheeses was performed after 4 and 6 months of ripening. The R8 cheeses had the highest and P1 the lowest concentrations of most of the volatile compounds quantified (fatty acids, ketones, aldehydes, esters, alcohols, lactones and methional). The R8 and P8 cheeses contained higher levels of most of the volatiles than R1 and P1 cheeses. Ripening temperature and type of milk influenced most of the flavour and aroma attributes. Principal component analysis (PCA) of aroma and flavour attributes showed that P1 and R1 had similar aroma and flavour profiles, while R8 had the highest aroma and flavour intensities, highest acid aroma and sour flavour. The age of cheeses influenced the perception of creamy/milky and pungent aromas. PCA of the texture attributes separated cheeses on the basis of ripening temperature. The R8 and P8 cheeses received significantly higher scores for perceived maturity than P1 and R1 cheeses. The P1 and R1 cheeses had similar values for perceived maturity. In a related study, it was found that concentrations of amino acids and fatty acids were similar in R1 and P1 during most of the ripening period, and R1 and P1 cheeses had low numbers of non-starter lactic acid bacteria (NSLAB). The panel found that ripening temperature, type of milk and age of cheeses did not influence the acceptability of cheese. It is concluded that NSLAB contribute to the formation of volatile compounds and affect the aroma and flavour profiles and the perceived maturity of Cheddar 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.     

Headspace analysis of volatile flavour compounds of teleme cheese made from sheep and goat milk

The headspace compounds of teleme cheese made from sheep's milk, goats' milk or mixture of sheep's and goats' milk (50:50) were analysed during ripening by static headspace gas chromatography–mass spectrometry. A total of 21 major compounds were identified, including aldehydes (7), alcohols (5), ketones (4), and acids (2). All types of cheeses contained approximately the same volatiles at different concentrations. The total volatile compounds (TVC) increased during ripening. Cheeses made from sheep's milk showed the highest level of TVC, whereas cheeses made from goats' milk showed the lowest one.     

Characterization of the chemistry, biochemistry and volatile profile of Kuflu cheese, a mould-ripened variety

The chemistry, biochemistry and volatile compounds of Kuflu cheese, a Turkish mould-ripened variety were studied. A total of 29 samples were analysed and the titratable acidity, moisture, salt-in-moisture, fat-in-dry matter and total protein contents (as mean values) were 0.96%, 49.97%, 7.49%, 12.18% and 37.84%, respectively, and the pH of the cheeses was 6.29. Indices of proteolysis (i.e., the levels of pH 4.6- and trichloroacetic acid-soluble nitrogen) were high; however, these values were lower than those of other Blue cheeses probably due to proportionally higher levels of total nitrogen and salt-in-moisture in Kuflu cheese samples. Urea-polyacrylamide gel electrophoresis of the pH 4.6-insoluble fractions of the cheeses showed that both α_s1- and β-caseins were extensively degraded, but β-casein was less degraded than α_s1-casein. RP-HPLC peptide profiles of the pH 4.6-soluble fractions from Kuflu cheeses showed that some minor quantitative differences were found between the samples, while peptide profiles of the samples were qualitatively similar. One hundred and thirty-eight compounds were identified in the volatile fractions of Kuflu cheese by gas chromatography-mass spectrometry (GC-MS) using a solid-phase microextraction technique. Ketones and alcohols were the principal class of volatile components in Kuflu cheeses, and terpenes and sulphur compounds were found at substantial levels in the majority of the samples, but aldehydes and lactones were present at low levels. The RP-HPLC and GC-MS data were analysed by principal component analysis based on their peptide and volatile profiles, respectively. Kuflu cheeses obtained from different markets had some differences in terms of chemical composition, proteolysis and patterns of aroma compounds.     

5种黑茶香气成分的比较分析

本研究采用感官审评法和顶空固相微萃取法,结合气相色谱-质谱仪联用技术,对5种黑茶样品挥发性成分进行了分析鉴定。结果表明,5种黑茶共检出83种香气化合物,共有成分30种,主要包括醇类、醛类、酮类、芳香烃类、烯类和酯类等;不同产区黑茶香气特征及组成存在明显差异:青砖茶陈香纯正,以醛类和酮类化合物为主,包括(E,E)-2,4-庚二烯醛、β-紫罗酮、己醛;茯砖茶\     

Study of the chemical composition,proteolysis, volatile compounds,and textural properties of industrial and traditional Beaten (Bieno sirenje) ewe milk cheese

The objective of this study was to determine the gross composition, proteolysis, and volatile and texture profiles during ripening of industrial (IND) and traditional (TRD) Beaten (Bieno sirenje) cheeses made by using ewe milk. In the course of the analyses, statistical differences were determined in some physicochemical parameters, nitrogen fractions, and total free amino acid levels between TRD and IND types of cheese. Higher levels of proteolysis were observed in IND cheeses than in TRD cheeses during ripening. Levels of residual β- and α_s-caseins were 72.2 and 48.7%, respectively, in 180-d-old TRD cheeses. However, the residual levels were 52.8% for β-casein and 18% for α_s-casein in IND cheeses. Similar differences were noted for the reversed-phase HPLC peptide profiles of 2 types of cheeses. Also, higher concentrations of peptides were eluted in IND cheeses than in TRD cheeses during ripening. A total of 73 volatile compounds, including alcohols (16), esters (17), acids (14), terpenes (7), ketones (5), aldehydes (4), and miscellaneous (10) were identified. The IND cheeses contained higher levels of carboxylic acids, esters, alcohols, and terpenes than the TRD cheeses; however, the same levels of methyl ketones were determined in the 2 types of cheeses at the end of ripening. These may be due to some differences (e.g., pasteurization and scalding temperature, among other factors) in the manufacture of the 2 types of Beaten cheeses. The textural profile of Beaten cheeses showed that TRD production method resulted in firmer, less fracturable, and stiffer cheeses than the IND production method. In conclusion, the results suggest that the use of industrial production method (pasteurization of cheese milk and curd scalding at 70°C) in the manufacture of Beaten ewe milk cheese enriched the volatile profile of the cheese.     

Comparison of purge and trap and solid phase microextraction techniques for studying the volatile aroma compounds of three European PDO hard cheeses

Solid phase microextraction (SPME) and purge and trap (P&T) methods were compared to establish their effectiveness for the extraction of cheese aroma compounds from selected raw milk protected designation of origin (PDO) cheeses. The profiles of the volatile fraction from each cheese variety obtained by using the two extraction methods were significantly different. SPME fibres were more effective for extracting medium and high boiling compounds, P&T was better for extracting the highly volatile compounds. Gruyère Switzerland cheeses showed high concentrations of alkenes, aldehydes, methyl ketones, butane-2,3-dione, unsaturated alcohols, branched chain acids and 2,6-dimethyl pyrazine. Manchego cheeses contained high concentrations of alkanes, alkanols, prop-2-en-1-ol, propan-2-one and butan-2-one and their corresponding reduction products propan-2-ol and butan-2-ol, propyl esters and aromatic compounds. Ragusano cheeses contained high concentrations of fatty acids and ethyl and butyl esters. Discriminant analyses, performed separately for each extraction method, correctly classified all the samples by their PDO origin.     

Aroma compound production in cheese curd by coculturing with selected yeast and bacteria.

The microorganisms involved in cheese ripening produce various volatile compounds and induce typical flavors that contribute to cheese variety. To investigate aroma compound generation of cheese microflora, we used a dynamic headspace-gas chromatography-mass spectrometry analysis. To obtain good sensitivity and repeatability of quantification, dynamic headspace conditions and sample preparation were first optimized and led to an extraction set up in which samples were heated at 60 degrees C and diluted with water without pH adjustment. Then three different yeasts and three Geotrichum candidum commonly used in mold surface ripened cheeses were studied in pure culture in a cheese model medium. Thirty-nine cocultures of these three yeasts, the three G. candidum, and five bacteria were studied in the same medium to assess the interaction between microorganisms on aroma compound production. Twenty-four volatile compounds belonging to different chemical classes (alcohols, aldehydes, esters, sulfides, terpenes) were identified and quantified. Yeasts and especially Kluyveromyces lactis produced large amounts of alcohols, aldehydes, esters, and terpenes when cultured alone or in association. Geotrichum candidum and especially G. candidum strain G3 generated the largest amount of sulfides when cultured alone or in association. Finally, bacteria also produced aroma compounds but, except for Brevibacterium linens strain B5, which produced dimethyl trisulfide and ketones, no specific trend in the production of particular aroma compounds could be evidenced.     

4种主要柑橘类香气成分比较

为探明不同柑橘品种果实的香气成分,采用顶空固相微萃取结合气相色谱-质谱联用法分别对芦柑、脐橙、砂糖橘和狮头柑4个具有典型气味的柑橘品种果皮中的香气成分进行分析,分别从这4个品种果皮样品中检测出挥发性成分39、37、43种和41种,在芦柑和砂糖橘香气中缺少酯类物质,在脐橙香气中缺少酮类物质,狮头柑香气中包括了烃类、醛类、酮类、醇类、酯类、芳香族化合物和一些其他成分,初步从香气成分种类差异、共有香气成分相对含量差异以及各自特有成分上解释了4种果品的香气区别,从化学角度说明了4个柑橘品种果实香气类型的差异。     

VOLATILE FLAVOR COMPOUNDS IN 'KUNUN ZAKI'- A NIGERIAN MILLET-BASED BEVERAGE

Flavor volatile compounds of Kunun Zaki beverage were collected and concentrated on a Tenax GC and identified on a GC‐MS. Collected and separated compounds were evaluated for their aroma impression. Twenty‐eight volatile compounds were detected in the Kunun Zaki beverage. These were made up of pyrazines, ketones, alcohols, aldehydes, hydrocarbons and pyrroline. The aldehydes and pyrazines contributed a much higher percentage peak area to the beverage volatiles than ketones, hydrocarbons and alcohols. Kunun Zaki beverage exhibits a characteristic sweet, roasty potato‐like flavor.     

The role of triglycerides and phospholipids in the aroma of cooked beef

The intramuscular triglycerides and the structural phospholipids were selectively removed from beef muscle by solvent extraction and the aroma of the residual material assessed after cooking. Removing triglycerides had little effect on the aroma of the cooked meat, but when both triglycerides and phospholipids were removed a marked difference in aroma was observed. The headspace volatiles from the different cooked meats were entrained on Tenax GC and analysed by combined gas chromatography-mass spectrometry. The profile of headspace volatiles for the meat devoid of triglycerides was similar to that from an unextracted control and the major components were aliphatic alcohols and aldehydes. Removing phospholipids as well as triglycerides gave a markedly different volatile profile; the quantities of aliphatic aldehydes were considerably reduced and only traces of aliphatic alcohols were found, while the amounts of benzaldehyde and pyrazines were greatly increased. The latter explains some of the changes in roast aroma.     

Comparison of the compositional, microbiological, biochemical, and volatile profile characteristics of nine Italian ewes' milk cheeses

Nine Italian ewes’ milk cheeses were compared for compositional, microbiological, biochemical, and volatile profile characteristics. Mean values for the gross composition were rather similar among cheeses. The lowest pH values were found for cheeses that used primary starters. At the end of ripening, cheeses made from raw milk contained >6.0 log₁₀ cfu/g of nonstarter lactic acid bacteria. Several species of lactobacilli were identified, but Lactobacillus plantarum and Lactobacillus paracasei were dominant. Random amplified polymorphic DNA-PCR analysis showed the biodiversity among the strains, and in several cases a relationship with the cheese of provenance. Cheeses differed mainly for secondary proteolysis, as shown by the principal component analysis applied to reversed-phase fast protein liquid chromatography data of the pH 4.6-soluble fractions and by determination of the free AA. A total of 113 volatile components were identified in the Italian Pecorino cheeses by solid-phase microextraction coupled with gas chromatography-mass spectrometry analysis. The volatile profiles of the 9 cheeses differed significantly. Quantitatively, alcohols were the most abundant chemical class for some cheeses, whereas ketones were the most abundant for other cheeses. Esters and carboxylic acids were largely found. Specific volatile components seemed to distinguish specific cheeses.