Proteolysis and texture changes of a Spanish soft cheese (‘Torta del Casar’) manufactured with raw ewe milk and vegetable rennet during ripening

Proteolysis and textural changes of the Spanish ewe raw milk soft cheese of the Protected Designation of Origin Torta del Casar were studied in four different stages of ripening, with 1, 30, 60 and 90 days. In general, proteolysis in Torta del Casar cheese was weak at 1 and 30 days and it was more intense between the 30–60 days of ripening. Soluble nitrogen non‐protein nitrogen, polypeptide N and free amino acids values significantly increased during cheese ripening. Protein and casein nitrogen decreased significantly after 60 days of ripening resulting in the increase of the other nitrogen fractions measured. Caseins changes determined by capillary zone electrophoresis showed that proteolysis of β‐casein occurred faster than αs1‐casein but the latter suffered higher proteolytic degradation at the end of ripening (day 90). This pattern of degradation of caseins is reversed in other cheeses made with animal rennet. Texture analysis showed that firmness and consistency decreased along ripening while adhesiveness increased. Highly significant correlations were found between textural parameters, residual caseins levels and nitrogen fractions during maturation, which shows the importance of proteolytic changes for an optimal texture formation.     

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.     

Changes during ripening in chemical composition,proteolysis, volatile composition and texture in Kashar cheese made using raw bovine,ovine or caprine milk

Kashar cheeses were manufactured from pure ovine (OV), bovine (BV) and caprine (CP) milk, and the chemical composition, cheese yield, proteolysis, hardness, meltability and volatile composition were studied during 90 days. Gross chemical composition, cheese yield and level of proteolysis were higher in OV cheeses than those of BV or CP cheeses. Glu, Val, Leu, Phe and Lys were the most abundant free amino acids (FAA) in the samples, and the concentrations of individual FAA were at the highest levels in OV cheeses with following BV and CP cheeses. Urea‐PAGE patterns and RP‐HPLC peptide profiles of the BV cheeses were completely different from the small ruminants’ milk cheeses (OV or CP). Higher and lower hardness and meltability values were observed in CP cheeses, respectively. OV cheeses resulted in higher levels of the major volatile compounds. In conclusion, the Kashar cheese made using OV milk can be recommended due to high meltability, proteolysis and volatiles.     

Effect of frozen storage on the proteolytic and rheological properties of soft caprine milk cheese

Freezing and long-term frozen storage had minimal impact on the rheology and proteolysis of soft cheese made from caprine milk. Plain soft cheeses were obtained from a grade A goat dairy in Georgia and received 4 storage treatments: fresh refrigerated control (C), aged at 4°C for 28 d; frozen control (FC), stored at −20°C for 2 d before being thawed and aged in the same way as C cheese; and 3-mo frozen (3MF), or 6-mo frozen (6MF), stored at −20°C for 3 or 6 mo before being thawed and aged. Soft cheeses had fragile textures that showed minimal change after freezing or over 28 d of aging at 4°C. The only exceptions were the FC cheeses, which, after frozen storage and aging for 1 d at 4°C, were significantly softer than the other cheeses, and less chewy than the other frozen cheeses. Moreover, after 28 d of aging at 4°C, the FC cheeses tended to have the lowest viscoelastic values. Slight variation was noted in protein distribution among the storage treatment, although no significant proteolysis occurred during refrigerated aging. The creation and removal of ice crystals in the cheese matrix and the limited proteolysis of the caseins showed only slight impact on cheese texture, suggesting that frozen storage of soft cheeses may be possible for year-round supply with minimal loss of textural quality.     

Changes in volatile, sensory and microbial profiles during preparation of smoked ewe cheese

BACKGROUND: Oscypek is a special type of Polish smoked ewe cheese with a unique flavour described as slightly sour, piquant, salted and smoked. In this study the volatile, sensory and microbial profiles of Oscypek cheese were analysed during its various preparation stages of curding, scalding, brining and smoking. RESULTS: The smoked ewe cheese was characterised by 54 volatile compounds belonging to nine different chemical groups (free fatty acids, esters, ketones, alcohols, aldehydes, furans/furanones, phenols, sulfur compounds, terpenes). The sensory aroma profile analysis of unsmoked and smoked cheese showed an important correlation with the analysis of volatile compounds. The microbial profile data indicated that in smoked cheese such as Oscypek the levels of selected bacteria diminished after the curding stage as a result of the subsequent scalding, brining and smoking stages. CONCLUSION: From the results it can be concluded that, although the analysed smoked cheese consisted of three groups of compounds, the first derived from biochemical reactions (free fatty acids, esters, ketones, alcohols, aldehydes, sulfur compounds), the second from smoking (furans and furanones, phenols) and the third from milk flavour (terpenes), it is the smoking process that mainly influences its typical flavour. Copyright © 2011 Society of Chemical Industry     

High-pressure processing decelerates lipolysis and formation of volatile compounds in ovine milk blue-veined cheese

Enzyme-rich cheeses are prone to over-ripening during refrigerated storage. Blue-veined cheeses fall within this category because of the profuse growth of Penicillium roqueforti in their interior, which results in the production of highly active proteinases, lipases, and other enzymes responsible for the formation of a great number of flavor compounds. To control the excessive formation of free fatty acids (FFA) and volatile compounds, blue-veined cheeses were submitted to high-pressure processing (HPP) at 400 or 600 MPa on d 21, 42, or 63 after manufacture. Cheeses were ripened for 30 d at 10°C and 93% relative humidity, followed by 60 d at 5°C, and then held at 3°C until d 360. High-pressure processing influenced the concentrations of acetic acid and short-chain, medium-chain, and long-chain FFA. The effect was dependent on treatment conditions (pressure level and cheese age at the time of treatment). The lowest concentrations of acetic acid and FFA were recorded for cheeses treated at 600 MPa on d 21; these cheeses showed the lowest esterase activity values. Acetic acid and all FFA groups increased during ripening and refrigerated storage. The 102 volatile compounds detected in cheese belonged to 10 chemical groups (5 aldehydes, 12 ketones, 17 alcohols, 12 acids, 35 esters, 9 hydrocarbons, 5 aromatic compounds, 3 nitrogen compounds, 3 terpenes, and 1 sulfur compound). High-pressure processing influenced the levels of 97 individual compounds, whereas 68 individual compounds varied during refrigerated storage. Total concentrations of all groups of volatile compounds were influenced by HPP, but only ketones, acids, esters, and sulfur compounds varied during refrigerated storage. The lowest total concentrations for most groups of volatile compounds were recorded for the cheese pressurized at 600 MPa on d 21. A principal component analysis combining total concentrations of groups of FFA and volatile compounds discriminated cheeses by age and by the pressure level applied to HPP cheeses.     

Changes in texture,composition and sensory characteristics of Camembert cheese made from a mixture of goat milk and cow milk during ripening

The study was conducted to evaluate the nutritional, textural and sensory characteristics of Camembert cheese made from goat milk, cow milk and their blends. The type of milk used affected yield, physicochemical properties and fatty acid profile of the cheeses. The percentages of C6:0, C8:0 and C10:0 acids were higher in the cheeses containing ≥ 75% goat milk. The sensory evaluation results showed differences in texture, colour, aroma and flavour among the cheeses. Cheeses made with the mixture of cow and goat milk particularly 50% goat milk mixed with 50% cow milk (50G:50C) maintained particular positive nutritional characteristics especially with respect to the mineral contents, fatty acids and consumer acceptability.     

Effect of starter cultures on the physico‐chemical and biochemical features in ewe cheese made with extracts from flowers of Cynara cardunculus L

The effect of starter cultures on the physico‐chemical and biochemical features of Los Pedroches cheese made by using Cynara Cardunculus L extracts as vegetable coagulant was assessed. Specimens of cheese containing no starter (vats A and C) and others to which a lactic acid starter was added (vats B and D) were stored either under typical farmhouse ripening conditions (vats A and B) or in a controlled chamber at 14°C and 80% relative humidity (vats C and D) for 90 days. The addition of starter cultures and the ripening conditions where found to have no appreciable effect on the moisture, fat, protein, ash, NaCl, Ca and P contents of the cheese, nor on its water activity; however, it resulted in increased lactic acid contents and lower pH values relative to control specimens throughout ripening. The protein breakdown of the cheeses was assessed in terms of soluble nitrogen, non‐protein nitrogen, aminoacid nitrogen, ammonia nitrogen, soluble tyrosine and tryptophan, and urea‐PAGE. Proteolysis was generally more marked and rapid in cheese containing the lactic starter, the NPN, NH₃ ‐N and soluble Tyr and Trp contents of which were significantly higher than those of the cheese obtained with no starter. The PAGE technique revealed no appreciable differences between the four cheese batches studied; however, it showed the cheese to be more resistant to β‐CN hydrolysis than to α_s‐CN hydrolysis. In general, the flavour and aroma scores were higher in batches obtained with starter cultures and ripened under controlled conditions. © 1999 Society of Chemical Industry     

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.     

Effects of curd heating with or without previous milk pasteurisation on the microbiological quality and safety of craft‐made ‘Pasta Filata’ Kashkaval cheese curds

An empirical ‘Pasta Filata’ process used for traditional Kashkaval cheese manufacture from raw ewes’ milk improved the hygiene of fresh curd. Coagulase‐positive (RPF+) staphylococci and coliforms declined by 2.4 and 4.5 log units, respectively, and Listeria contamination was minimised. Before Pasta Filata, RPF+ staphylococci exceeded the 5‐log threshold level specified in EC Regulation 1441/2007 in raw milk curds despite the prevalence of indigenous mesophilic lactic acid bacteria. Pasta Filata favoured enterococci in raw milk curds. Pasteurisation enhanced prevalence of Streptococcus thermophilus and Lactococcus lactis starters and microbial quality and safety of pasteurised milk curds before and particularly after Pasta Filata.     

Compositional characteristics and volatile organic compounds of traditional PDO Feta cheese made in two different mountainous areas of Greece

The compositional characteristics of Feta cheese manufactured in two mountainous areas from raw milk, from sheep fed by grass, and the forages’ volatile organic compounds (VOC) were studied, to differentiate the Feta cheese. Although the main compositional features did not vary greatly, the proteolysis mode was altered. The VOC profiles of the cheeses varied. While some VOCs were common to both groups of cheeses, others were discriminatory for each production area. There were common terpenes in both the bulk forage and the mature cheeses. Overall, the VOC composition of Feta could provide a basis for identification with regard to its region of origin.     

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.     

Microbiological and chemical characterization of Fiore Sardo, a traditional Sardinian cheese made from ewe's milk

The purpose of this study was to assess the chemical and microbial characteristics of 12 batches of artisanal Fiore Sardo, a protected designation of origin (PDO) hard cheese made from raw ewe's milk without addition of starters, during maturation. High standard deviations were observed for moisture percentage, total solids percentage and NaCl percentage content, possibly owing to differences in manufacturing processes and/or milk composition. Total mesophilic bacteria varied between 10 log₁₀ cfu/g in 48-h-old cheese samples and 3 log₁₀ cfu/g in 9-month-old samples. Total coliforms and staphylococci showed the highest counts at 48 h of ripening then decreased significantly, dropping to levels below 2 log₁₀ cfu/g at 3 months of maturation. Lactic acid bacteria and enterococci were the dominant micro-organisms throughout maturation. They were mainly represented by the species Lactococcus lactis ssp. lactis, Enterococcus faecium, Lactobacillus plantarum and Lactobacillus casei group. Low levels of yeasts were detected throughout the maturation period of the cheese. Debaryomyces hansenii and Kluyveromyces lactis var. lactis were the prevalent yeast species isolated.     

Effect of milk protein standardization using different methods on the composition and yields of Cheddar cheese

Two sets of Cheddar cheese were made in which the milk protein level (%, wt/wt) was increased from 3.3 (Control A, CA) to 3.6 (set A) or from 3.3 (control B, CB) to 4.0 (set B) by the addition of phosphocasein (PC), milk protein concentrate (MPC), or freshly prepared ultrafiltered milk retentate (UFR). The cheeses were denoted CA, PCA, MPCA, and UFRA from set A, and CB, PCB, MPCB, and UFRB, from set B, respectively. The level of cheese moisture decreased significantly on increasing milk protein level from 3.3 to 3.6 or 4.0% (wt/wt), but was not affected significantly by the method of protein standardization. The percentage milk fat recovered to cheese increased significantly on increasing the level of milk protein from 3.3 to 3.6% (wt/wt) with PC, and from 3.3 to 4.0% (wt/wt) with PC, MPC, and UFR. Increasing milk protein level from 3.3 to 4.0% (wt/wt) with PC significantly increased the percentage of milk protein recovered to cheese. Actual cheese yield increased significantly with milk protein level. The yield of cheese per 100 kg of milk normalized to reference levels of fat (3.4%, wt/wt) and casein (2.53%, wt/wt) indicated no significant effects of protein content or standardization treatment on yield. However, the moisture-adjusted yield per 100 kg of milk with reference levels of fat and casein increased significantly on increasing the protein content from 3.3 to 3.6% (wt/wt) with MPC and from 3.3 to 4.0% (wt/wt) with PC, MPC, and UFR.     

Comparison of the characteristics of teleme cheese made from ewe's, goat's and cow's milk or a mixture of ewe's and goat's milk

Teleme cheeses were manufactured from ewe's, goat's and cow's milk and mixture of ewe's and goat's milk. Physicochemical and biochemical analyses of the cheeses at various stages of ripening and storage were performed. Cheeses made from goat's milk had lower moisture content than those made from other milks. No significant differences in the mean values of protein, salt and water activity (a _w ) of the different cheeses at all ages studied were found. Cheeses from goat's and cow's milk had higher contents of fat and fat in dry matter (FDM) compared to that of cheeses from ewe's milk and mixed milk. Significant differences were observed in the yield and yield on 56% moisture: cheeses from ewe's milk gave the highest yield and cheese from cow's milk the lowest. Significant differences were found in the ashes content of the different cheeses at all ages. No differences in cholesterol and cholesterol/fat contents of the four types of cheeses were found. Main and trace elements showed variability among the four cheeses.     

Biological activities of the bioaccessible compounds after in vitro digestion of low-fat Akawi cheese made from blends of bovine and camel milk

The objective of this study was to assess protein degradation and biological activities of the water-soluble extract (WSE) and the 10 kDa permeable and nonpermeable fractions of in vitro digesta of low-fat Akawi cheese made from blends (100:0, 85:15, or 70:30) of bovine milk and camel milk and ripened for 28 d. Biological activities, such as antioxidant activities, amylase and glucosidase inhibition, angiotensin-converting enzyme inhibition, and antiproliferative of the WSE, and the 10 kDa permeable and nonpermeable fraction of the digesta were assessed. To identify the nature of the bioaccessible compounds, untargeted metabolomic analysis was carried out by ultra-high performance liquid chromatography–quadrupole time-of-flight mass spectrometry. Higher o-phthaldialdehyde absorbances were observed in cheeses made of bovine-camel milk blends compared with cheese from bovine milk only. The WSE from these blends also exhibited higher angiotensin-converting enzyme inhibitory effects and higher antiproliferative effects than from bovine milk. The results from this study suggest that the use of blends of camel milk and bovine milk can modulate biological activities of low-fat Akawi cheese.     

Yield and sensory properties of cheese made with milk from Holstein or Montbéliarde cows milked twice or once daily

The aim of this study was to evaluate the milk properties and the yield and sensory properties of Cantal cheese made with milk from Holstein or Montbéliarde cows milked once or twice daily. Sixty-four grazing cows [32 Holstein (H) and 32 Montbéliarde (M) cows] in the declining phase of lactation (157 d in milk) were allocated to 1 of 2 equivalent groups milked once daily (ODM) or twice daily (TDM) for 7 wk. The full-fat raw milk collected during 24 h from the 4 groups of cows (M-TDM, M-ODM, H-TDM, and H-ODM) was pooled and processed into Cantal cheese 4 times during the last 4 wk of the experimental period. In all, 16 cheeses were made (2 milking frequencies × 2 breeds × 4 replicates) and analyzed after a ripening period of 15 and 28 wk. The results showed that for both breeds, the pooled milk content of fat, whey protein, casein, total protein, and phosphorus as well as rennet clotting time and curd firming time were significantly higher with ODM cows, whereas the casein-to-total protein ratio was lower, and lactose, urea, calcium, and free fatty acids contents of milk remained unchanged. The acidification and draining kinetics of the cheese as well as cheese yields and the chemical and rheological properties of the ripened cheese were not significantly modified by milking frequency. For both breeds, the cheeses derived from ODM cows had a slightly yellower coloration but the other sensory attributes, except for pepper odor, were not significantly affected by milking frequency, thereby demonstrating that ODM does not have an adverse effect on the sensory properties of Cantal cheese. Compared with that of Holstein cows, milk from Montbéliarde cows resulted in a higher cheese yield (+1.250 kg/100 kg of milk) and ripened cheeses with lower pH, dry matter, calcium, sodium chloride, and water-soluble nitrogen concentrations. These cheeses had also a less firm and more elastic texture, a more acidic taste, and a yogurt/whey aroma.     

Technical note: Development and validation of a new method for the quantification of soluble and micellar calcium,magnesium, and potassium in milk

Milk mineral content is a key trait for its role in dairy processes such as cheese-making, its use as source of minerals for newborns, and for all traits involving salt-protein interactions. This study investigated a new method for measuring mineral partition between soluble and micellar fractions in bovine milk after rennet coagulation. A new whey dilution step was added to correct the quantification bias due to whey trapped in curd and excluded volume. Moreover, the proposed method allowed the quantification of the diffusible volume after milk coagulation. Milk mineral content and concentration in whey, and diluted whey were quantified by acid digestion and inductively coupled plasma optical emission spectrometry. The repeatability of the method for micellar Ca, Mg, and K was between 2.07 and 8.96%, whereas reproducibility ranged from 4.01 to 9.44%. Recovery of total milk minerals over 3 spiking levels ranged from 92 to 97%. The proposed method provided an accurate estimation of micellar and soluble minerals in milk, and curd diffusible volume.