A study on the ripening of white pickled Brinza cheese made from ewe's milk

The chemical composition, the microbiological feature and the microstructure of young and mature Brinza cheese were investigated. During ripening fat, total nitrogen, soluble nitrogen, non protein nitrogen; peptide nitrogen, amino acid nitrogen and acidity increased while the microbial feature decreased. The amount of free amino acids and free fatty acids increased with storage and the patterns of their distribution changed with the highest levels for lysine, glutamic, oleic, palmatic and myristic acids. The microstructure of fresh Brinza cheese consists of casein micelles joined together to form an open network with clustering of micelles. During ripening, these micelles continued to aggregate and coalesce with increasing fusion process to give more homogeneous and loose structure similar to that in white pickled Domiati 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.     

Microstructure,free amino acids and free fatty acids in Domiati cheese treated with β-galactosidase

Domiati cheese was made from partially lactose hydrolyzed fresh milk and examined for the microstructure, the free amino acids, and the free fatty acids when young and after two months. The addition of β-galactosidase to cheese milk before renneting enhanced the fusion of protein and the formation of more homogenious structure of submicelles compared to control, as well as produced a good quality cheese of 1.5–2.5 fold free amino acids and free fatty acids as much as those of control. The differences were particularly great in respect of serine, phenylalanine, aspartic acid, glutamic acid, myristic acid, palmatic acid and oleic acid.     

Manufactore of Ras cheese from ultrafiltered milk supplemented with caseinates

Whole cow's milk was ultrafiltered (conc. Factor 5), sodium and calcium caseinate were added to the milk retentate at the rate of 0.5 and 0.75% (w/w) of the milk. Ras cheese was made from milk retentate supplemented with different levels of caseinate salts, as well as unsupplemented retentates, and compared with Ras cheese made by the traditional method. Retentate supplemented with 0.5% Na and Ca caseinate was suitable for Ras cheese-making with limited whey drainage, supplementation of retentate with 0.75% Ca caseinate gave defective cheese at the end of ripening, while Na caseinate increased soluble N and free fatty acids in the cheese. Organoleptic scoring showed that supplementation with Na caseinate enhanced cheese ripening.     

1984 Award to professor Y. Pomeranz for advancement of application of agricultural and food chemistry

Differences in chemical and free amino acid compositions, microstructure and sensory quality during pickling were found between Kariesh cheese made from lactose-hydrolyzed milk and a control.Sodium caseinate and essential free amino acids are considered to be the proteinaceous and free amino acids components of this type of cheese. Differences in flavour between the two cheese types are assumed to be due to differences in free amino acid contents during pickling. The microstructure of the ripened experimental cheese was more homogeneous than that of the control cheese.Protein degradation, free amino acid concentration and fusion of casein micelles in the cheese protein matrix were increased, and the organoleptic quality of Kariesh cheese was improved, when β-galactosidase was added to the cheese milk before processing.     

Evaluation of isolated starter lactic acid bacteria in Ras cheese ripening and flavour development

Eighteen cultures of starter lactic acid bacteria with or without added adjunct cultures, isolated from Egyptian dairy products, were evaluated in experimental Ras cheese for flavour development. Chemical composition of experimental cheeses was within the legal limit for Ras cheese in Egypt. All cultures used in this study had no effect on chemical composition of Ras cheese. Very significant variations in free amino acids, free fatty acids and sensory evaluation have been found among the cultures used in Ras cheesemaking. The levels of free amino acids and free fatty acids were correlated well with flavour development in Ras cheese. Seven of the tested cultures produced acceptable flavour and texture of Ras cheese. The highest overall score of flavour intensity, flavour and texture acceptability were in cheese made using YY47 lactic culture in addition to adjunct culture of Lactobacillus helveticus, Lactobacillus paracasei subsp. paracasei, Lactobacillus delbrueckii subsp. lactis and Enterococcus faecium. This culture can be recommended for Ras cheese manufacture using pasteurized milk.     

Accelerated ripening of Ras cheese using cell free extract,freeze- and heat-shocked Leuconostoc spp. cultures

Ras cheese was manufactured with cell free extract, freeze- and heat-shocked cultures of Leuconostoc spp. to enhance flavour development and accelerated ripening. Cheese analysis (pH, acidity, dry matter, fat, protein, soluble nitrogen, volatile acidity, free fatty acids) were carried out for 3 months. No significant differents were observed between the experiment cheeses and control, however, the cheese flavour was enhanced in cheeses with addition of heat treated Leuconostoc cells. Bitter taste was decreased in all experimental cheeses.     

Free fatty acids and oxidative changes of a raw goat milk cheese through maturation

Free fatty acids (FFA) and lipid and protein oxidation changes were studied throughout maturation process of a raw goat milk cheese with protected designation of origin. Cheeses were analyzed at 4 different times of maturation, at 1, 30, 60, and 90 d. All FFA significantly increased during maturation and the relative increase was higher for long-chain than medium- or short-chain FFA. At the end of maturation, oleic (C18:1 n9), butyric (C4:0), and palmitic (C16:0) acids were the most abundant. The higher levels of short-chain fatty acids (SCFA) regarding total FFA obtained at the end of Ibores cheese ripening compared with other raw goat milk cheeses, highlight the notable role of SCFA on the flavor of this cheese owing to their low-odor thresholds. Lipid oxidation values significantly increased during maturation process but low levels of malondialdehyde were reported; however, protein oxidation did not significantly change during ripening.     

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.     

Free fatty acids and oxidative changes of a Spanish soft cheese (PDO 'Torta del Casar') during ripening

Free fatty acids (FFA) and lipid and protein oxidation changes during ripening were studied in Torta del Casar cheese. This cheese with protected designation of origin (PDO) is made from raw ewe milk and uses vegetable rennet. Cheeses were analysed at four different stages of ripening at 1, 30, 60 and 90 days. Most FFA significantly increased throughout maturation, except valeric and margaric acids. Acetic acid content increased during ripening and was the most abundant FFA in Torta del Casar cheese at the end of ripening. Short chain fatty acids (SCFA) showed an important increase throughout maturation, especially butyric, isovaleric and isobutyric acids. Lipid oxidation values significantly increased during the first month and decreased in the last 2 months of maturation; however, protein oxidation did not significantly change during ripening. Changes in FFA, especially SCFA, could have great importance in Torta del Casar cheese final characteristics; however, oxidative reactions did not play an important role.     

Influence of adjunct cultures on volatile free fatty acids in reduced-fat Edam cheeses

The effects of the adjunct cultures Lactococcus lactis ssp. diacetylactis, Brevibacterium linens BL2, Lactobacillus helveticus LH212, and Lactobacillus reuteri ATCC 23272 on volatile free fatty acid production in reduced-fat Edam cheese were studied. Lipase activity evaluation using p-nitrophenyl fatty acid ester substrates indicated that L. lactis ssp. diacetylactis showed the highest activity among the 4 adjunct cultures. Full-fat and 33% reduced-fat control cheeses (no adjunct) were made along with 5 treatments of reduced-fat cheeses, which included individual, and a mixture of the adjunct cultures. Volatile free fatty acids of cheeses were analyzed using static headspace analysis with 4-bromofluorobenzene as an internal standard. Changes in volatile free fatty acid concentrations were found in headspace gas of cheeses after 3-and 6-mo ripening. Acetic acid was the most abundant acid detected throughout ripening. Full-fat cheese had the highest relative amount of propionic acid among the cheeses. Certain adjunct cultures had a definite role in lipolysis at particular times. Reduced-fat cheese with L. lactis ssp. diacetylactis at 3-mo showed the highest levels of butyric, isovaleric, n-valeric, iso-caproic, and n-caproic acid. Reduced-fat cheese with Lactobacillus reuteri at 6 mo produced the highest relative concentration of isocaproic, n-caproic, and heptanoic, and the highest relative concentration of total acids.     

β-Galactosidase in the acceleration of Ras cheese ripening

An attempt has been carried out to accelerate Ras cheese ripening by pre-treatment of cheese milk with β-galactosidase. Milk was treated with a β-galactosidase enzyme preparation, namely lactozym (1 ml/kg milk), at 33°C for 1 h or at 4°C for 18 h and used for Ras cheese making. Flavour intensity, formation of soluble nitrogen compounds, free amino acids and liberation of free fatty acids were enhanced in cheese made from β-galactosidase treated milk. In addition, the ripening period was reduced to 2 months compared with 4 months required for control cheese. Treatment of cheese milk with β-galactosidase at 4°C or 33°C showed a similar effect on the properties of cheese.     

About presence of free phosphoserine in ripened cheese and in enzymatic hydrolysate of casein

Occurrence of free phosphoserine (SerP) in ripened cheeses was investigated to clarify whether this amino acid can be directly released from casein by enzymatic attack. Free amino acids extracted from cheese were separated by IEC or RP-HPLC and the peak of SerP always eluted close to unretained material and acidic components. Presence of these interferences suggests that the content of free SerP (from 0.8 to 16.4 mmoles/kg cheese) could be highly overestimated. These figures were dramatically lowered (up to 100 times) after a purification step of the cheese extract on cationic column, but the chromatographic separation of SerP was not yet interference-free. However, these values of free SerP are not significant on the basis of the total amount of free amino acids (<0.06%). The interfering compounds were characterized in Grana Padano cheese by FAB-MS and several low-MW peptides were found, the most abundant of which was the casein phosphopeptide (CPP) β(16-22)3P. In vitro enzymatic hydrolysis of casein confirmed that accumulation of short-chain CPPs having the common structure X-SerP-SerP-SerP-Glu-Glu-X occurs, explaining incomplete recovery of the amino acids. The recovery increased from 89% up to 96% and the content of Ser and Glu approached the theoretical value when the enzymatic hydrolysis was performed in presence of alkaline phosphatase. These data are consistent with splitting of Ser and not of SerP from casein by enzymatic attack and with accumulation of only free Ser in cheese ripening. Because of the accumulation of “enzyme-resistant” CPPs, in vitro enzymatic hydrolysis of casein can be completed when alkaline phosphatase is included in the pool of enzymes.     

Influence of selected lab cultures on the evolution of free amino acids, free fatty acids and Fiore Sardo cheese microflora during the ripening

Fiore Sardo Protected Denomination of Origin is a traditional Sardinian (Italy) hard cheese produced exclusively from whole raw ovine milk and coagulated with lamb rennet paste. Currently, Fiore Sardo is still produced by shepherds at the farmhouse level without the addition of any starter culture and the cheese-making process is characterized by significant waste. The first objective of the present work was to investigate the autochthonous microflora present in milk and Fiore Sardo cheese in order to select lactic acid bacterial (LAB) cultures with suitable cheese-making attributes and, possibly reduce the production waste. Secondly, the ability of selected cultures to guarantee cheese healthiness and quality was tested in experimental cheese-making trials. In this study, we show that the typical lactic microflora of raw ewe's milk and Fiore Sardo cheese is mostly composed of mesophilic LAB such as Lactococcus lactis subsp. lactis, Lactobacillus plantarum and Lactobacillus casei subsp. casei. Moreover, strains belonging to the species were selected for cheese-making attributes and used in experimental cheese-making trials carried out in different farms producing Fiore Sardo. The evolution of the cheese microflora, free amino acids and free fatty acids during the ripening showed that the experimental cheeses were characterized by a balanced ratio of the chemical constituents, by a reduced number of spoilage microorganisms and, remarkably, by the absence of production waste that were significant for the control cheeses.     

Identification of free fatty acids and some other volatile flavour compounds from Swiss cheese using on-line supercritical fluid extraction-gas chromatography

On-line supercritical CO₂ extraction - gas chromatography was applied to the isolation and identification of free fatty acids and other volatile compounds of young and ripe Swiss cheese (Emmental) produced in Finland. Extractions were carried out using a micro-cartridge at 40 °C temperature and 10 MPa pressure and the volatile fractions were analysed by DB-WAX column (polyethylene glycol phase) with flame ionization detection and mass spectrometry. The total time of analysis was less than 2.5 h. Acetic acid and propionic acid predominated over the C12–C18 acids, the longer chain fatty acids increasing in concentration during the ripening of the cheese. Due to the high proportions of fatty acids, further fractionation is required for analysis of the less abundant aroma compounds such as alcohols, carbonyls and lactones.     

Microstructure and chemical changes in Twarog cheese made from ultrafiltrated milk and from lactose-hydrolysed milk

Twarog cheese was manufactured from fresh milk, lactose-hydrolysed milk and retentate. Microstructure, chemical composition, protein breakdown, amino acid distribution and organoleptic properties were studied during ripening.Inoculation of the milk with β-galactosidase, before cheese processing, reduced the clotting time, enhanced the protein breakdown and enhanced amino acid accumulation during ripening. Concentrating the milk, by ultrafiltration, prolonged the coagulation time and resulted in a cheese with greater amounts of moisture, fat, total nitrogen and higher pH than other cheeses.Essential free amino acids are considered to constitute more than half of the total free amino acids of Twarog cheese and glutamic acid, leucine and phenylalanine are the major free amino acids in the ripened cheese.Quality of the cheese was improved either by ultrafiltration or by lactose hydrolysis and the acceptable flavour was more pronounced in β-galactosidase-treated cheese.Microstructure of the protein in young cheeses does not differ in all treatments. The disintegration and fusion of casein advanced during ripening in the outer protein matrix more than internally. The appearance of the cheese matrix was similar in both control and ultrafiltrated cheeses while the casein in β-galactosidase-treated cheese fused faster than in other treatments.     

Kinetic description of heat‐induced cross‐linking reactions of whey protein‐free casein solutions

Heat treatment of milk products induces several physico‐chemical changes that can compromise rennetability and milk protein functionality. The aim of this study was to investigate the kinetic parameters of heat‐induced polymerisation of whey protein‐free casein micelles in the native environment of skim milk, which were produced by microfiltration and ultrafiltration in a diafiltration mode. The intra‐ or intermolecular polymerisation of casein monomers by covalent cross‐linking of amino acids was analysed by gel‐permeation chromatography. The degree of polymerisation and the amounts of polymerisation products such as lysinoalanine and histidinoalanine leading to cross‐linking of proteins could be described as zero‐order reaction.     

Dynamics of the uptake of free amino acids in the blood serum of the portal vein during the digestion of isolated krill protein

The rate of absorption of amino acids obtained from isolated krill protein administered to rat stomach was studied. Absorption of casein amino acids was determined for reference purposes. Rats subjected to 48-hour fasting were administered krill isolate and casein in the form of homogenates at a rate 540 mg protein per 100 g bw in 6 ml of distilled water. The concentration of free amino acids in the portal vein was measured after 30 minutes, 1, 3 and 6 hours. The content of amino acids was measured by ion-exchange chromatography with the use of an automatic analyzer of amino acids. The digestion of krill protein proceeds at a high rate. This ensures the maximal augmentation of the concentration of most amino acids in the blood of the portal vein 30 min after isolate administration to the stomach.