The mathematical modelling of cheese ripening

A mathematical model is developed for the ripening of cheese. Such models may assist predicting final cheese quality using measured initial composition. The main constituent chemical reactions are described with ordinary differential equations. Numerical solutions to the model equations are found using Matlab. Unknown parameter values have been fitted using experimental data available in the literature. The results from the numerical fitting are in good agreement with the data. Statistical analysis is performed on near infrared data provided to the MISG. However, due to the inhomogeneity and limited nature of the data, not many conclusions can be drawn from the analysis. A simple model of the potential changes in acidity of cheese is also considered. The results from this model are consistent with cheese manufacturing knowledge, in that the pH of cheddar cheese does not significantly change during ripening.

Evaluation of microbial adjuncts and their effect on the ripening of cheddar cheese

A bacteriocin-producing strain of Lactobacillus paracasei DPC 4715 was used as an adjunct culture in Cheddar cheese in order to control the growth of “wild” nonstarter lactic acid bacteria. No suppression of growth of the indicator strain was observed in the experimental cheese. The bacteriocin produced by Lactobacillus paracasei DPC 4715 was sensitive to chymosin and cathepsin D and it may have been cleaved by the rennet used for the cheese manufactured or by indigenous milk proteases. A series of studies were performed using various microbial adjuncts to influence cheese ripening. Microbacterium casei DPC 5281, Corynebacterium casei DPC 5293 and Corynebacterium variabile DPC 5305 were added to the cheesemilk at level of 109 cfu/ml resulting in a final concentration of 108 cfu/g in Cheddar cheese. The strains significantly increased the level of pH 4.6-soluble nitrogen, total free amino acids after 60 and 180 d of ripening and some individual free amino acids after 180 d. Yarrowia lipolytica DPC 6266, Yarrowia lipolytica DPC 6268 and Candida intermedia DPC 6271 were used to accelerate the ripening of Cheddar cheese. Strains were grown in YG broth to a final concentration of 107 cfu/ml, microfluidized, freeze-dried and added to the curd during salting at level of 2% w/w. The yeasts positively affected the primary, secondary proteolysis and lipolysis of cheeses and had aminopeptidase, dipeptidase, esterase and 5’ phosphodiestere activities that contributed to accelerate the ripening and improve the flavor of cheese. Hafia alvei was added to Cheddar cheesemilk at levels of 107 cfu/ml and 108 cfu/ml and its contribution during ripening was evaluated. The strain significantly increased the level of pH 4.6-soluble nitrogen, total free amino-acids, and some individual free amino-acids of Cheddar cheese, whereas no differences in the urea-polyacrylamide gel electrophoresis (urea-PAGE) electrophoretograms of the cheeses were detected. Hafia alvei also significantly increased the level of some biogenic amines. A low-fat Cheddar cheese was made with Bifidobacterium animalis subsp. lactis, strain BB-12® at level of 108 cfu/ml, as a probiotic adjunct culture and Hi-Maize® 260 (resistant high amylose maize starch) at level of 2% and 4% w/v, as a prebiotic fiber which also played the role of fat replacer. Bifidobacterium BB-12 decreased by 1 log cycle after 60 d of ripening and remained steady at level of ~107 cfu/g during ripening. The Young’s modulus also increased proportionally with increasing levels of Hi-maize. Hencky strain at fracture decreased over ripening and increased with increasing in fat replacer. A cheese based medium (CBM) was developed with the purpose of mimicking the cheese environment at an early ripening stage. The strains grown in CBM showed aminopeptidase activity against Gly-, Arg-, Pro- and Phe-p-nitroanalide, whereas, when grown in MRS they were active against all the substrates tested. Both Lb. danicus strains grown in MRS and in CBM had aminotransferase activity towards aromatic amino acids (Phe and Trp) and also branched-chain amino acids (Leu and Val). Esterase activity was expressed against p-nitrophenyl-acetate (C2), pnitrophenyl- butyrate (C4) and p-nitrophenyl-palmitate (C16) and was significantly higher in CBM than in MRS.

Use of a new milk-clotting protease from Thermomucor indicae-seudaticae N31 as coagulant and changes during ripening of Prato cheese

Prato cheeses were manufactured using coagulant from Thermomucor indicae-seudaticae N31 or a commercial coagulant. Cheeses were characterised using the following analysis: yield; fat; acidity; moisture; ash; salt; pH; total nitrogen; total protein; NS-pH 4.6/NT100; NS-TCA 12%/NT100; casein electrophoresis; and RP-HPLC. The results were statistically analysed and revealed that the proteolytic indices were not significantly different throughout the 60 days of ripening of cheeses made with either coagulant. Even though there were some quantitative differences in the peptide profile of cheeses, the enzyme from T. indicae-seudaticae N31 was used in the production of good quality Prato cheese without having to change the established technological parameters of the process. © 2011 Elsevier Ltd. All rights reserved.

Microfiltration in cheese and whey processing

Milk microfiltration (0.05-0.2 um) is a membrane separation technique which divides milk components into casein-enriched and native whey fractions. Hitherto the effect of intensive microfiltration including a diafiltration step for both cheese and whey processing has not been studied. The microfiltration performance of skimmed milk was studied with polymeric and ceramic MF membranes. The changes caused by decreased concentration of milk lactose, whey protein and ash content for cheese milk quality and ripening were studied. The effects of cheese milk modification on the milk coagulation properties, cheese recovery yield, cheese composition, ripening and sensory quality as well as on the whey recovery yield and composition by microfiltration were studied. The functional properties of whey protein concentrate from native whey were studied and the detailed composition of whey protein concentrate powders made from cheese wheys after cheese milk pretreatments such as high temperature heat treatment (HH), microfiltration (MF) and ultrafiltration (UF) were compared. The studied polymeric spiral wound microfiltration membranes had 38.5% lower energy consumption, 30.1% higher retention of whey proteins to milk retentate and 81.9% lower permeate flux values compared to ceramic membranes. All studied microfiltration membranes were able to separate main whey proteins from skimmed milk. The optimal lactose content of Emmental cheese milk exceeded 3.2% and reduction of whey proteins and ash content of cheese milk with high concentration factor (CF) values increased the rate of cheese ripening. Reduction of whey protein content in cheese milk increased the concentration of caseinomacropeptide (CMP) of total proteins in cheese whey. Reduction of milk whey protein, lactose and ash content reduces milk rennet clotting time and increased the firmness of the coagulum. Cheese yield calculated from raw milk to cheese was lower with microfiltrated milks due to native whey production. Amounts of a-lactalbumin (a-LA) and b-lactoglobulin (b-LG) were significantly higher in the reference whey, indicating that HH, MF and UF milk pretreatments decrease the amounts of these valuable whey proteins in whey. Even low CF values in milk microfiltration (CF 1.4) reduced nutritional value of cheese whey. From the point of view of utilization of milk components it would be beneficial if the amount of native whey and the CMP content of cheese whey could be maximized. Whey protein concentrate powders made of native whey had excellent functional properties and their detailed amino acid composition differed from those of cheese whey protein concentrate powders.

Primary proteolysis of caseins in cheddar cheese

Studies were undertaken to investigate proteolysis of the caseins during the initial stages of maturation of Cheddar cheese. Isolated caseins were hydrolyzed by enzymes thought to be of importance during cheese ripening and the resulting peptides isolated and identified. Large peptides were also isolated from Cheddar cheese and identified, thus enabling the extent to which casein degradation studies could be extrapolated to cheese to be established. The proteolytic specificity of chymosin on bovine αs1- and αs2-caseins and of plasmin on bovine αs1-casein were determined. The action of cathepsin D, the principal indigenous acid milk proteinase, on caseins was studied and its pH optimum and sensitivity to NaCI determined. The action of cathepsin D on αs1-, αs2-, β- and κ-caseins was compared with that of chymosin and was found to be generally similar for the hydrolysis of αs1- and κ-caseins but to differ for αs2-and β- caseins. β-Casein in solution was hydrolyzed by cell wall-associated proteinases from three strains of Lactococcus lactis; comparison of electrophoretograms of the hydrolyzates with those of Cheddar cheese indicated that no peptides produced by cell wall-associated proteinases were detectable in the cheeses. All the major peptides in the water-insoluble fraction of Cheddar cheese were isolated and identified. It was found that β-casein was degraded primarily by plasmin and αs1 -casein by chymosin. Initial chymosin and plasmin cleavage sites in αs1-, and β-casein, respectively, identified in these and other studies corresponded to the peptides isolated from cheese. The importance of non-starter lactic acid bacteria (NSLAB) to the maturation of Cheddar was studied in cheeses manufactured from raw, pasteurized or microfiltered milks. NSLAB were found to strongly influence the quality and patterns of proteolysis. Results presented in this thesis are consistent with the hypothesis that primary proteolysis in Cheddar is catalysed primarily by the action of chymosin and plasmin on intact αs1- and β-caseins, respectively. The resulting large peptides so produced are subsequently degraded by these enzymes and by proteinases and peptidases from the starter and NSLAB.

Studies on factors relating to the development of defects in commercial cheese

Defects in commercial cheese result in a downgrading of the final cheese and a consequential economic loss to the cheese producer. Developments of defects in cheese are often not fully understood and therefore not controllable by the producer. This research investigated the underlying factors in the development of split and secondary fermentation defect and of pinking defects in commercial Irish cheeses. Split defect in Swiss-type cheese is a common defect associated with eye formation and manifests as slits and cracks visible in the cut cheese loaf (Reinbold, 1972; Daly et al., 2010). No consensus exists as to the definitive causes of the defect and possible factors which may contribute to the defect were reviewed. Models were derived to describe the relationship between moisture, pH, and salt levels and the distance from sample location to the closest external block surface during cheese ripening. Significant gradients within the cheese blocks were observed for all measured parameters in cheeses at 7 day post/after manufacture. No significant pH gradient was found within the blocks on exit from hot-room ripening and at three months post exit from the hot-room. Moisture content reached equilibrium within the blocks between exit from hot-room and 3 months after exit from hot-room while salt and salt-to-moisture levels had not reached equilibrium within the cheese blocks even at three months after exit from hot-room ripening. A characterisation of Swiss-type cheeses produced from a seasonal milk supply was undertaken. Cheeses were sampled on two days per month of the production year, at three different times during the manufacturing day, at internal and external regions of the cheese block and at four ripening time points (7 days post manufacture, post hot-room, 14 days post hot-room and 3 months in a cold room after exit from hot-room). Compositional, biochemical and microbial indices were determined, and the results were analysed as a splitplot with a factorial arrangement of treatments (season, time of day, area) on the main plot and ripening time on the sub-plot. Season (and interactions) had a significant effect on pH and salt-in-moisture levels (SM), mean viable counts of L. helveticus, propionic acid and non-starter lactic acid bacteria, levels of primary and secondary proteolysis and cheese firmness. Levels of proteolysis increased significantly during hot-room ripening but also during cold room storage, signifying continued development of cheese ripening during cold storage (> 8°C). Rheological parameters (e.g. springiness and cohesiveness) were significantly affected by interactions between ripening and location within cheese blocks. Time of day of manufacture significantly affected mean cheese calcium levels at 7 days post manufacture and mean levels of arginine and mean viable counts of NSLAB. Cheeses produced during the middle of the production day had the best grading scores and were more consistent compared to cheeses produced early or late during day of manufacture. Cheeses with low levels of S/M and low values of resilience were associated with poor grades at 7 days post manufacture. Chesses which had high elastic index values and low values of springiness in the external areas after exit from hot-room ripening also obtained good commercial grades. Development of a pink colour defect is an intermittent defect in ripened cheese which may or may not contain an added colourant, e.g., annatto. Factors associated with the defect were reviewed. Attempts at extraction and identification of the pink discolouration were unsuccessful. The pink colour partitioned with the water insoluble protein fraction. No significant difference was observed between ripened control and defect cheese for oxygen levels and redox potential or for the results of elemental analysis. A possible relationship between starter activity and defect development was established in cheeses with added coulourant, as lower levels of residual galactose and lactose were observed in defective cheese compared to control cheese free of the defect. Swiss-type cheese without added colourant had significantly higher levels of arginine and significantly lower lactate levels. Flow cell cytometry indicated that levels of bacterial cell viability and metabolic state differed between control and defect cheeses (without added colourant). Pyrosequencing analysis of cheese samples with and without the defect detected the previously unreported bacteria in cheese, Deinococcus thermus (a potential carotenoid producer). Defective Swiss-type cheeses had elevated levels of Deinococcus thermus compared to control cheeses, however the direct cause of pink was not linked to this bacterium alone. Overall, research was undertaken on underlying factors associated with the development of specific defects in commercial cheese, but also characterised the dynamic changes in key microbial and physicochemical parameters during cheese ripening and storage. This will enable the development of processing technologies to enable seasonal manipulation of manufacture protocols to minimise compositional and biochemical variability and to reduce and inhibit the occurrence of specific quality defects.

Oxidation-reduction potential and its influence on Cheddar cheese quality

Oxidation-reduction (redox) potential is a fundamental physicochemical parameter that affects the growth of microorganisms in dairy products and contributes to a balanced flavour development in cheese. Even though redox potential has an important impact on the quality of dairy products, it is not usually monitored in dairy industry. The aims of this thesis were to develop practical methods for measuring redox potential in cheese, to provide detailed information on changes in redox potential during the cheesemaking and cheese ripening and how this parameter is influenced by starter systems and to understand the relationship between redox potential and cheese quality. Methods were developed for monitoring redox potential during cheesemaking and early in ripening. Changes in redox potential during laboratory scale manufacture of Cheddar, Gouda, Emmental, and Camembert cheeses were determined. Distinctive kinetics of reduction in redox potential during cheesemakings were observed, and depended on the cheese technology and starter culture utilised. Redox potential was also measured early in ripening by embedding electrodes into Cheddar cheese at moulding together with the salted curd pieces. Using this approach it was possible to monitor redox potential during the pressing stage. The redox potential of Emmental cheese was also monitored during ripening. Moreover, since bacterial growth drives the reduction in redox potential during cheese manufacture and ripening, the ability of Lactococcus lactis strains to affect redox potential was studied. Redox potential of a Cheddar cheese extract was altered by bacterial growth and there were strain-specific differences in the nature of the redox potential/time curves obtained. Besides, strategies to control redox potential during cheesemaking and ripening were developed. Oxidizing or reducing agents were added to the salted curd before pressing and results confirmed that a negative redox potential is essential for the development of sulfur compounds in Cheddar cheese. Overall, the studies described in this thesis gave an evidence of the importance of the redox potential on the quality of dairy products. Redox potential could become an additional parameter used to select microorganisms candidate as starters in fermented dairy products. Moreover, it has been demonstrated that the redox potential influences the development of flavour component. Thus, measuring continuously changes in redox potential of a product and controlling, and adjusting if necessary, the redox potential values during manufacture and ripening could be important in the future of the dairy industry.

Chromatographic determination of fatty acids profiles in regionally-produced Portuguese goat cheese along curing

The biochemistry of cheese ripening involves mechanisms such as glycolysis, proteolysis and lipolysis. Fatty acids are released by the action of lipases from different sources, milk, rennet, bacteria, moulds included as secondary starters, and other exogenous lipases, during lipolysis [1]. The composition of the lipid fraction contributes positively to the flavour of cheese, for being precursors of more complex aroma compounds responsible for the characteristic “goaty flavour” of goat cheeses [2]. Goat milk is recognized by its easier digestibility, alkalinity, buffering capacity and certain therapeutic values in medicine and human nutrition [3]. A high total content of fatty acids is strongly linked to a rancid and tart off flavour in goat milk and may be considered undesirable in most cheese varieties [4]. In this sense, the purpose of the present study was to examine the composition and changes in fatty acids and saponification value of goat cheese during curing period (2, 7 and 12 months). Goat cheese was made in industrial unit of Cachão - Mirandela (Trás-os- Montes) with raw milk Serrana goats’ race, salt and rennet from animal origin. During the first two months, the samples were stored in a ripening chamber (9.5-11 °C and RH 75-85%). From the second month to one year, the samples were stored in a preservation chamber (10.5-12 °C and RH 75-85%). The fatty acids profile of the inner part of the cheese was analyzed by gas-chromatography coupled to flame ionization detection (GC-FID). The degree of saponification was determined both in the crust and inside the cheese by HCl titration of ethanol KOH solution of the samples. Twenty-six fatty acids (FA) were identified and quantified in the inner part of the cheese (total fat was 45-46 g/100 g during the curing period). Saturated fatty acids (SFA) did not change up to 7 months of curing, increasing only after 12 months, being palmitic (C16:0), stearic (C18:0), myristic (C14:0) and capric (C10:0) acids the most abundant FA in this class. Monounsaturated fatty acids (MUFA) decreased only after 12 months, and oleic acid (C18:1) was the predominant FA. In polyunsaturated fatty acids (PUFA) class, the most abundant were linoleic (C18:2) and linolenic (C18:3) acids, and followed the same tendency of MUFA. This is corroborated by an increase in the degree of saponification, either in the crust as in the inner part of the cheese, after 12 months of curing, probably related with the saturation of the fatty acids [3]. Extra-long curing can be done in cheeses produced with goat milk up to seven months of storage without changing the total fat and individual FA content.

Elaboração de um queijo análogo ao pecorino romano produzido com leite de cabra e coalhada congelados

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Queijo Parmesão: caracterização físico-química, microbiológica e microestrutura

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effet de réduction en sodium sur la texture et la bioaccessibilité des protéines d’un fromage à pâte molle à croûte fleurie

Le sel (NaCl) joue plusieurs rôles importants dans les fromages aux niveaux technologique, microbiologique et organoleptique. Cependant, le sodium, un facteur de risque des maladies cardiovasculaires, est consommé en trop grande quantité par les Canadiens. Comme la réduction du sodium pourrait affecter la texture des fromages à pâte molle à croûte fleurie et la libération des nutriments pendant la digestion, l’impact de la réduction du sodium sur la bioaccessibilité des protéines dans le fromage Brie a été étudié. Ainsi, la composition et les caractéristiques texturales de fromages Brie ayant différentes teneurs en sodium (standard, réduite, substituée au KCl) ont été analysées. Une réduction du sodium de 23 % a été obtenue pour les fromages réduits en sodium. Le temps d’affinage affecte la protéolyse et la texture des fromages. La cinétique de dégradation de la matrice fromagère et la libération des protéines ont été déterminées par une approche de digestion in vitro. La désintégration de la matrice fromagère et la libération des protéines pendant la digestion in vitro ne sont pas différentes entre les fromages expérimentaux. Ces travaux démontrent qu’il est possible de réduire le sodium sans affecter le profil de protéolyse et la texture pendant l’affinage du fromage Brie ainsi que son comportement à la digestion.