Free amino acid content of goat's milk cheese made with animal rennet and plant coagulant

BACKGROUND: Enzymes present in the flowers of Cynara cardunculus (cyprosins) are used in the production of some traditional Spanish and Portuguese cheeses, replacing animal rennet. The aim of this work was to study the changes that take place in free amino acids during the ripening of a goat's milk cheese (Murcia al Vino) manufactured with plant coagulant (PC) or animal rennet (AR). RESULTS: The total free amino acid (TFAA) concentration increased during ripening, with Ile, Val, Ala, Phe, Gaba, Arg and Lys representing more than 50% of the TFAA content at 60 days in both types of cheese. The TFAA concentration was significantly higher in cheeses made with PC (854 mg 100 g^?1 total solids (TS)) than those made with AR (735 mg 100 g^?1 TS). The concentration of most free amino acids, especially His, Ser, Gln, Thr, Ala, Met and Ile, was higher in the PC cheese. CONCLUSION: Cheese made using PC as coagulant presented higher contents of free amino acid throughout the ripening period than cheese made using AR. Therefore we can conclude that the use of PC to produce Murcia al Vino goat's cheese would accelerate the ripening process as a result of increased cyprosin proteolytic activity. Copyright © 2011 Society of Chemical Industry     

Volatile compounds in pressed ewes' milk cheese with saffron spice (Crocus sativus L.)

Saffron spice has been successfully used as an ingredient in dairy products as a means of diversification. The objective of this work was to determine the influence of saffron on the volatiles' profile of a pressed ewes' milk cheese. This was performed by means of a modern extraction technique based on headspace sorptive extraction. Results showed that safranal was the only volatile that could be identified and quantified from saffron spice. Most volatile compounds were present in all cheeses but at different concentrations. Differences between control and saffron cheeses were observed, but as ripening time increased, these differences were less evident.     

Lipolysis and proteolysis profiles of fresh artisanal goat cheese made with raw milk with 3 different fat contents

The objective of this study was to describe the proteolysis and lipolysis profiles in goat cheese made in the Canary Islands (Spain) using raw milk with 3 different fat contents (0.5, 1.5, and 5%) and ripened for 1, 7, 14, and 28 d. β-Casein was the most abundant protein in all cheeses and at all ripening times. Quantitative analysis showed a general decrease in caseins as ripening progressed, and degradation rates were higher for α_S1-casein than for β-casein and α_S2-casein. Furthermore, the degradation rate during the experimental time decreased with lower fat contents. The α_S2-casein and α_S1-casein levels that remained in full-fat and reduced-fat cheeses were less than those in low-fat cheese. In contrast, β-casein also showed degradation along with ripening, but differences in degradation among the 3 cheese types were not significant at 28 d. The degradation products increased with the ripening time in all cheeses, but they were higher in full-fat cheese than in reduced-fat and low-fat cheeses. The free fatty acid concentration per 100 g of cheese was higher in full-fat cheese than in reduced- and low-fat cheese; however, when the results were expressed as milligrams of free fatty acids per gram of fat in cheese, then lipolysis occurred more rapidly in low-fat cheese than in reduced- and full-fat cheeses. These results may explain the atypical texture and off-flavors found in low-fat goat cheeses, likely the main causes of non-acceptance.     

Investigation on the microstructural and textural properties of Lighvan cheese produced from bovine milk fortified with protein and gum tragacanth during ripening

The effect of 0.02% gum tragacanth, sodium caseinate or milk protein concentrate (MPC70) on the physiochemical, microstructural and textural properties of Lighvan cheese produced from bovine milk was investigated. The microstructure of cheese samples was studied by scanning electron microscopy (SEM), and the SEM micrographs were analysed using 3D images, surface plots and binarised SEM images. The texture parameters of bovine Lighvan cheese containing sodium caseinate were similar to those of ovine Lighvan cheese, and the microstructure of the MPC‐containing bovine Lighvan cheese was closest to that of ovine Lighvan cheese.     

Low-fat akawi cheese made from bovine-camel milk blends: Rheological properties and microstructural characteristics

Camel milk (CM) can be used as an ingredient to produce various dairy products but it forms weak rennet-induced and acid-induced gels compared with bovine milk (BM). Therefore, in this study, we aimed to investigate the effect of blending bovine milk with camel milk on the physicochemical, rheological (amplitude sweep and frequency sweep), and microstructural properties of low-fat akawi (LFA) cheese. The cheeses were made of BM only or BM blended with 15% (CM15%) or 30% (CM30%) camel milk and stored at 4°C for 28 d. The viscoelastic properties as a function of temperature were assessed. The LFA cheeses made from blended milks had higher moisture, total Ca, and soluble Ca contents, and had higher pH 4.6–water-soluble nitrogen compared with those made from BM. Analysis by scanning electron microscopy demonstrated that the microstructures formed in BM cheese were rough with granular surfaces, whereas those in blended milk cheeses had smooth surfaces. Hardness was lower for LFA cheeses made from blended milk than for those made from BM only. The LFA cheeses demonstrated viscoelastic behavior in a linear viscoelastic range from 0.1 to 1.0% strain. The storage modulus (G′) was lower in LFA cheese made from BM over a range of frequencies. Adding CM reduced the resistance of LFA cheeses to flow as temperature increased. Blended cheeses exhibited lower complex viscosity values than BM cheeses during temperature increases. Thus, the addition of camel milk improved the rheological properties of LFA cheese.     

Ripening changes of Kashkaval cheese made from cow's milk

Kashkaval cheese was made from cow's milk and examined for the changes in its microstructure and chemical composition during ripening.The percentages of fat, protein, soluble nitrogen, non-protein nitrogen, amino acid nitrogen and the total free fatty and amino acids increased during ripening.The presence of glutamic acid, leucine, phenylalanine, valine and tyrosine at high concentration, and of butyric, caproic, caprylic and capric acids may contribute to the formation of Kashkaval cheese flavour. The small concentrations of acetic and propionic acids preclude any contribution to Kashkaval flavour.In young cheese, casein aggregates lose their spherical shape due to the scalding and kneading processes and they form a fibrous network including cavities.During ripening, dissociation and fusion processes occur in protein fibres to form a more homogeneous structure and interaction between layers of casein sheets increases to give a more compact structure.     

Survival of micro‐organisms and organic acid profile of probiotic Cheddar cheese from buffalo milk during accelerated ripening

The study aimed to assess the impact of ripening at elevated temperatures on the survival of probiotic micro‐organisms and production of organic acids in Cheddar cheese. Cheese was manufactured from buffalo milk using lactococci starters along with different probiotic bacteria (Lactobacillus acidophilus LA‐5, Bifidobacterium bifidum Bb‐11 and Bifidobacterium longum BB536) as adjunct cultures. The cheeses were ripened at 4–6 °C or 12–14 °C for 180 days and examined for composition, organic acids and microbial survival. The production of organic acids was accelerated at 12–14 °C when compared to normal ripening temperatures. The probiotic bacteria increased production of lactic and acetic acids, compared to cheese made with lactococci alone. The survival of the mesophilic starters was significantly (P < 0.05) reduced in all the cheese samples ripened at the higher temperature. However, the probiotic bacteria remained viable (>7.0 log₁₀ cfu/g) throughout the 180 days of ripening, irrespective of temperature. It was concluded that Cheddar containing additional probiotic cultures can effectively be ripened at elevated temperatures without any adverse effects.     

Fatty acid profiling of bovine milk and cheese from six European areas by GC‐FID and GC‐MS

The fatty acid (FA) composition of milk from six European areas, as well as the alteration in the FA profile during cheese production, was studied using both a targeted GC‐FID and an untargeted GC‐MS approach. By applying principal component, partial least square discriminant and chemical similarity enrichment analysis, a discrimination of the geographical areas could be achieved highlighting important FA classes such as odd‐ and branched‐chain FAs for the differentiation. The FA profile remained constant during cheese production, and aroma compounds have been identified as biomarkers for the ripening methods used, namely foil and smear ripening.     

凝乳酶对牦牛乳硬质干酪成熟期间蛋白降解的影响

以新鲜牦牛乳为原料,采用小牛皱胃酶、木瓜蛋白酶和微生物凝乳酶制作硬质干酪,探讨凝乳酶种类对牦牛乳硬质干酪成熟期间蛋白质降解的影响。结果表明:三种凝乳酶牦牛乳硬质干酪成熟过程中,不同凝乳酶牦牛乳硬质干酪在成熟期间蛋白质降解能力存在较大差异,总氮（TN）、p H4.6水溶性氮（p H4.6-SN/TN）、12%的三氯乙酸氮（12%TCA-N/TN）、5%磷钨酸氮（5%PTA-N/TN）含量、游离氨基酸均随成熟时间延长不同程度的增加,蛋白氮和酪蛋白氮逐渐降低,多肽氮呈先升高后下降趋势,且微生物凝乳酶降解牦牛乳硬质干酪蛋白能力显著（p<0.05）高于木瓜蛋白酶和小牛皱胃酶。      

Ripening of Camembert-type cheese made from caprine milk using calf rennet or kid rennet as coagulant

Camembert-type cheese was made from caprine milk using either calf rennet or kid 'Grandine' rennet as coagulant. The pH of all cheeses increased throughout ripening and levels of pH 4.6-soluble nitrogen increased from 8.1 to 18.2% of total nitrogen (TN) and from 6.9 to 20% TN for the cheeses made using calf rennet and kid rennet, respectively. Degradation of β-casein, measured by urea–polyacrylamide gel electrophoresis, and total and free amino acids were greater in the cheese made using kid rennet. Production of peptides, analysed by high performance liquid chromatography (HPLC), was slightly more extensive in the Camembert-type cheese made using calf rennet as coagulant. In general, a higher degree of proteolysis was found in Camembert-type cheese made from caprine milk using kid rennet than in cheese made using calf rennet as coagulant.     

Fresh cheese from camel milk coagulated with Camifloc

Camel milk was processed into cheese using Camifloc and calcium chloride. Two types of cheeses were produced from camel milk, using Camifloc (CF cheese) and CaC_l2 in addition to Camifloc (CFCC cheese). The study revealed the usefulness of Camifloc in coagulation of camel milk. The time of coagulation was found to be about 2–3 h, and the yield of CFCC cheese was found to be higher than the CF cheese, while a shelf life of 4 days was obtained for both cheeses. Both cheeses showed nonsignificant variations in compositional content except for the percentages of protein and ash, which showed significant differences at P < 0.001 and P < 0.05. Sensory evaluation by taste panellists was conducted to determine the acceptability of cheeses during the storage periods. Differences were found between the CF cheese and the CFCC cheese in saltiness and overall acceptability, and higher mean scores were recorded for the CF cheese than the CFCC cheese. The study recommends the use of Camifloc in making cheese from camel milk; and if CaCl₂ is added, it can improve the cheese yield. However, we suggest that the rate of salting should be reduced, and further drying and storage of the cheese should be done.     

Ripening of Cheddar cheese made from blends of raw and pasteurised milk

Cheddar cheeses were made from pasteurised milk (P), raw milk (R) or pasteurised milk to which 10 (PR10), 5 (PR5) or 1 (PR1) % of raw milk had been added. Non-starter lactic acid bacteria (NSLAB) were not detectable in P cheese in the first month of ripening, at which stage PR1, PR5, PR10 and R cheeses had 10⁴, 10⁵, 10⁶ and 10⁷ cfu NSLAB g⁻¹, respectively. After ripening for 4 months, the number of NSLAB was 1–2 log cycles lower in P cheese than in all other cheeses. Urea–polyacrylamide gel electrophoretograms of water-soluble and insoluble fractions of cheeses and reverse-phase HPLC chromatograms of 70% (v/v) ethanol-soluble as well as -insoluble fractions of WSF were essentially similar in all cheeses. The concentration of amino acids were pro rata the number of NSLAB and were the highest in R cheese and the lowest in P cheese throughout ripening. Free fatty acids and most of the fatty acid esters in 4-month old cheeses were higher in PR1, PR5, PR10 and R cheeses than in P cheese. Commercial graders awarded the highest flavour scores to 4-month-old PR1 cheeses and the lowest to P or R cheese. An expert panel of sensory assessors awarded increasingly higher scores for fruity/sweet and pungent aroma as the level of raw milk increased. The trend for aroma intensity and perceived maturity was R>PR10>PP5>PR1>P. The NSLAB from raw milk appeared to influence the ripening and quality of Cheddar cheese.     

Effects of high pressure on proteolytic enzymes in cheese: relationship with the proteolysis of ewe milk cheese

Ewe milk cheeses were submitted to 200, 300, 400, and 500 MPa (2P to 5P) at 2 stages of ripening (after 1 and 15 d of manufacturing; P1 and P15). The high-pressure-treated cheeses showed a more important hydrolysis of β-casein than control and 2P1 cheeses. Degradation of α_s1-casein was more important in 3P1, 4P1, and P15 cheeses than control and 2P1 cheeses. The 5P1 cheeses exhibited the lowest degradation of α_s-caseins, probably as a consequence of the inactivation of residual chymosin. Treatment at 300 MPa applied on the first day of ripening increased the peptidolytic activity, accelerating the secondary proteolysis of cheeses. The 3P1 cheeses had extensive peptide degradation and the highest content of free amino acids. Treatments at 500 MPa, however, decelerated the proteolysis of cheeses due to a reduction of microbial population and inactivation of enzymes.     

Proteolytic and lipolytic changes during the ripening of León raw cow's milk cheese, a Spanish traditional variety

Proteolytic and lipolytic changes were studied throughout ripening of five batches of León cow's milk cheese, a traditional variety made in the north of Spain. Total soluble nitrogen, non-protein nitrogen, oligopeptides nitrogen, amino nitrogen and ammonia nitrogen fractions increased slightly during the ripening process. The final values of these nitrogen fractions indicate that this cheese undergoes a very slight proteolysis as much in extent as in depth. This weak protein degradation is corroborated when the caseins and their degradation products were quantified by electrophoresis. β-Casein stayed practically intact throughout the ripening process and only 10% of α_s-casein became degraded. The content of total free amino acids increased progressively but in a slightly increased way during ripening, reaching final average values of 592 mg (100 g)⁻¹ of total solids. The most abundant free amino acid at the end of ripening was lysine, followed by leucine, glutamic acid, tryptophan, valine and phenylalanine. The acidity index of the fat values increased during ripening by a factor of 4.39. The final values of this parameter are in the range of those observed in other cow's milk cheeses ripened by bacteria. The content in total free fatty acids underwent an increase throughout ripening reaching final average values of 6669 ppm. The most abundant free fatty acid at the end of ripening was oleic acid followed by butyric and palmitic acids. The high content of short-chain fatty acids is outstanding, specially that of butyric acid.     

Physicochemical,microbiological, textural and sensory changes during the ripening of pasteurised goat milk cheese made with plant coagulant (Cynara scolymus)

This study describes the changes that occur during the ripening of cheeses made with a plant coagulant derived from artichoke flowers (Cynara scolymus). The results indicate that the physicochemical composition during ripening evolves similarly to other cheeses. The texture and sensory features of the cheeses during ripening evolved differently from that observed for other goat cheeses. Although it is common for a bitter taste to develop during the ripening of cheeses elaborated with plant coagulants, bitterness was scored very low in the cheeses made with artichoke, so that these cheeses could be suitable for marketing.     

黑豆豆乳添加量对Mozzarella奶酪成熟过程中品质的影响

在牛乳中添加不同的黑豆豆乳,研究不同的黑豆豆乳添加量对Mozzarella奶酪在成熟0 d、30 d、60 d、90 d时的水分活度、pH、质构、色泽、蛋白质降解等品质指标变化的影响。结果显示,随着黑豆豆乳添加量在2%～6%范围内的增大,奶酪的水分活度不断增大,pH不断降低,奶酪的硬度、弹性、粘附性、咀嚼性增加,奶酪的明亮度（L*值）下降,红度（a*值）和黄度（b*值）增加,而加入黑豆豆乳的奶酪在成熟过程中蛋白质降解与对照奶酪相似。综合各个指标,在牛乳中加入4%黑豆豆乳条件下制作的黑豆豆乳牛乳奶酪,既有独特的风味,同时奶酪具有较好的色度、质构、蛋白降解等指标特性。     

Vatless manufacturing of low-moisture part-skim mozzarella cheese from highly concentrated skim milk microfiltration retentates

Low-moisture, part-skim (LMPS) Mozzarella cheeses were made from concentration factor (CF) 6, 7, 8, and 9, pH 6.0 skim milk microfiltration (MF) retentates using a vatless cheese-making process. The compositional and proteolytic effects of cheese made from 4 CF retentates were evaluated as well as their functional properties (meltability and stretchability). Pasteurized skim milk was microfiltered using a 0.1-microm ceramic membrane at 50 degrees C to a retentate CF of 6, 7, 8, and 9. An appropriate amount of cream was added to achieve a constant casein:fat ratio in the 4 cheesemilks. The ratio of rennet to casein was also kept constant in the 4 cheesemilks. The compositional characteristics of the cheeses made from MF retentates did not vary with retentate CF and were within the legal range for LMPS Mozzarella cheese. The observed reduction in whey drained was greater than 90% in the cheese making from the 4 CF retentates studied. The development of proteolytic and functional characteristics was slower in the MF cheeses than in the commercial samples that were used for comparison due to the absence of starter culture, the lower level of rennet used, and the inhibition of cheese proteolysis due to the inhibitory effect of residual whey proteins retained in the MF retentates, particularly high molecular weight fractions.     

Texture and flavour development in Ras cheese made from raw and pasteurised milk

Texture, proteolysis and flavour development in Ras cheeses made from raw or pasteurised milk with two different thermophilic lactic cultures were monitored during ripening. Results showed that at day 1 of manufacture, the moisture content and pH were lower in raw milk cheese than in pasteurised milk cheeses. Levels of water-soluble nitrogen, casein breakdown, free amino groups and free fatty acids were higher in cheese made from raw milk than in that made from pasteurised milk. Textural characteristics, such as hardness, cohesiveness and chewines, increased in all treatments during the first 60 days of ripening due to the reduction in the moisture level during the second stage of salting (dry salting during the first 60 days of ripening). Cheese made from raw milk received the highest texture and flavour scores by panellists.     

Effects of freezing and frozen storage on the microstructure and texture of ewe's milk cheese

Semi-hard ewe's milk cheeses, frozen immediately after manufacture either slowly at –35 °C or rapidly at –80 °C and stored at –20 °C for 4 months were studied for microstructural and textural characteristics during subsequent ripening. Two control groups were used to establish the effect of freezing: the fresh unfrozen cheese and cheese thawed immediately after freezing. Freezing proper did not result in any marked changes in the textural parameters of the cheeses, but considerable changes were found in slowly frozen cheeses after 4 months of frozen storage. Shear strength values were lower in all frozen and stored cheeses, particularly in cheese samples frozen slowly compared to those in the unfrozen control batch. This parameter and firmness values were significantly lower in both slowly and rapidly frozen cheeses at the completion of ripening. Ripening tended to offset differences in elasticity, noticeable in the cheeses during the first 30 days of ripening. Light microscopy and electron microscopy revealed small cracks and ruptures in the cheeses which could not be observed by the naked eye. More extensive damage to the cheese microstructure was found in slowly frozen cheese samples stored frozen for 4 months.