Cheese Manufacturing Process Research Articles

Microbiological quality of white local sheep cheese in Mosul city markets

The soft white cheese is considered one of the most popular locally manufactured cheese in Iraq, a kind of traditional cheese that is mainly produced from sheep milk. It usually becomes available in the markets of Mosul between the months of February and July. To investigate the microbiological quality, 25 samples of white, soft, un-salted fresh locally produced sheep cheese were collected from the market in Mosul. These cheese samples were examined by the quantity method to determine the total viable bacterial counts (TVC) and the total counts of coliform and Escherichia coli bacteria. The minimum, maximum and average results of the aforementioned bacterial counts were 1.0x106, 1.4x103, 1.4x102 CFU g-; 2.9x108, 6.0x107, 12.6x105 CFU g- and 18.0x107, 5.8x106, 3.1x105 CFU g-1, respectively. Corresponding to the ‘International Microbiological Reference Criteria’ for cheese, it could be clear from these results that the samples were highly contaminated. Hence, it can be concluded that the sanitary conditions were inadequate either during the milk production and cheese manufacturing process or throughout their distribution in the local market. Therefore, it is recommended to comply with the public health and sanitary measures during the process of local cheese production. In consequence, it is essential to follow the annual screening of local cheese in terms of bacterial counts to determine the degree of contamination and in order to develop a national standard microbiological criteria and quality control for local cheese.

Incorporating flaxseed (linum usitatissimum) oil into queso blanco at different stages of the cheese manufacturing process

The objective of this study was to evaluate the physicochemical and microbial properties of queso blanco (QB) with flaxseed oil (FO) incorporated at different stages of the cheese manufacturing process. Whole milk was homogenized, coagulated with citric acid, salted with NaCl, and the resulting curds were pressed. Then QBFO was produced by incorporating FO during homogenization (QBFO-H), coagulation (QBFO-C), or salting (QBFO-S). The cheeses were stored at 8 °C for 30 days. Significantly lower lipid oxidation in QB was observed when FO was added during coagulation or salting compared to homogenization. However, lipid oxidation values of QBFO-H did not exceed the allowable limit for good quality food, it experienced the lowest yeast and mold counts, and only QBFO-H had a significantly higher lipid content than QB. This study demonstrated that QB containing FO can be effectively produced by incorporating FO during the homogenization step of the cheese manufacturing process. Practical applications Flaxseed oil (FO) is a potent source of α-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid. Incorporation of FO into queso blanco (QB) cheese may provide a functional food that aids in greater omega-3 polyunsaturated fatty acid consumption. Addition of FO into QB during homogenization yielded a good quality cheese with higher fat content.

Staphylococcus aureus Entrance into the Dairy Chain: Tracking S. aureus from Dairy Cow to Cheese.

Staphylococcus aureus is one of the most important contagious mastitis pathogens in dairy cattle. Due to its zoonotic potential, control of S. aureus is not only of great economic importance in the dairy industry but also a significant public health concern. The aim of this study was to decipher the potential of bovine udder associated S. aureus as reservoir for S. aureus contamination in dairy production and processing. From 18 farms, delivering their milk to an alpine dairy plant for the production of smeared semi-hard and hard cheese. one thousand hundred seventy six one thousand hundred seventy six quarter milk (QM) samples of all cows in lactation (n = 294) and representative samples form bulk tank milk (BTM) of all farms were surveyed for coagulase positive (CPS) and coagulase negative Staphylococci (CNS). Furthermore, samples from different steps of the cheese manufacturing process were tested for CPS and CNS. As revealed by chemometric-assisted FTIR spectroscopy and molecular subtyping (spa typing and multi locus sequence typing), dairy cattle represent indeed an important, yet underreported, entrance point of S. aureus into the dairy chain. Our data clearly show that certain S. aureus subtypes are present in primary production as well as in the cheese processing at the dairy plant. However, although a considerable diversity of S. aureus subtypes was observed in QM and BTM at the farms, only certain S. aureus subtypes were able to enter and persist in the cheese manufacturing at the dairy plant and could be isolated from cheese until day 14 of ripening. Farm strains belonging to the FTIR cluster B1 and B3, which show genetic characteristics (t2953, ST8, enterotoxin profile: sea/sed/sej) of the recently described S. aureus genotype B, most successfully contaminated the cheese production at the dairy plant. Thus, our study fosters the hypothesis that genotype B S. aureus represent a specific challenge in control of S. aureus in the dairy chain that requires effective clearance strategies and hygienic measures already in primary production to avoid a potential transfer of enterotoxic strains or enterotoxins into the dairy processing and the final retail product.

Peynir Üretiminde Pıhtı Kesim Zamanının Belirlenmesinde Kullanılan Enstrümental Yöntemler

In cheese-manufacturing process, cutting time greatly affects moisture, yield, and quality of cheese as well as whey fat losses. The objective cutting time determination is extremely important to both the quality and the quantity of cheese being produced. Taking into account the importance of accurate cutting time determination for economic and practical aspects, numerous instrumental techniques have been developed to assess cutting time based on a wide range of mechanical, vibrational, ultrasonic, thermal or optical instrument methods. In this article, information about advanced instrumental methods applied to the analysis of cutting time will be given.

Draft Genome Sequence of Corynebacterium variabile Mu292, Isolated from Munster, a French Smear-Ripened Cheese.

Here, we report the draft genome sequence of Corynebacterium variabile Mu292, which was originally isolated from the surface of Munster, a French smear-ripened cheese. This genome investigation will improve our knowledge on the molecular determinants potentially involved in the adaptation of this strain during the Munster-type cheese manufacturing process.

Insights into milk-clotting activity of latex peptidases from Calotropis procera and Cryptostegia grandiflora

Latex fractions from Calotropis procera, Cryptostegia grandiflora, Plumeria rubra, and Himatanthus drasticus were assayed in order to prospect for new plant peptidases with milk-clotting activities, for use as rennet alternatives. Only C. procera and C. grandiflora latex fractions exhibited proteolytic and milk-clotting activities, which were not affected by high concentrations of NaCl and CaCl2. However, pre-incubation of both samples at 75°C for 10min eliminated completely their activities. Both proteolytic fractions were able to hydrolyze k-casein and to produce peptides of 16kDa, a similar SDS-PAGE profile to commercial chymosin. RP-HPLC and mass spectrometry analyses of the k-casein peptides showed that the peptidases from C. procera or C. grandiflora hydrolyzed k-casein similar to commercial chymosin. The cheeses made with both latex peptidases exhibited yields, dry masses, and soluble proteins similar to cheeses prepared with commercial chymosin. In conclusion, C. procera and C. grandiflora latex peptidases with the ability to coagulate milk can be used as alternatives to commercial animal chymosin in the cheese manufacturing process.

Effect of Nutrient Supplementation on Biobutanol Production from Cheese Whey by Abe (acetone–butanol–ethanol) Fermentation

Cheese whey is a liquid effluent obtained from the cheese manufacturing process, presenting a high volumetric production and high organic loads related to its lactose content. The aim of this research was to increase the productivity of ABE fermentation with the bacterial strain Clostridium beijerinckii CECT 508, when using nanofiltered sheep cheese whey as a substrate. Thermal sterilization of the whey was essential to avoid the proliferation of lactic acid bacteria. An experimental design including Plackett-Burman and Response Surface Methodology (RSM) was applied to figure out which additional nutrients were necessary for the fermentation process and their optimum concentrations. For this specific whey, it was established that 1 g/L yeast extract, 5 g/L CaCO3, 0.019 g/L FeSO4·7H2O, 0.2 g/L MgSO4·7H2O and 2.1 g/L NH4Cl needed to be added. Under optimal nutrient conditions, the highest butanol production (9.11 g/L) was obtained with an initial lactose concentration of 57 g/L; achieving 49% lactose consumption and 0.311 g/g YB/L yield. However, the best lactose consumption rate (87%) was recorded for lactose initial concentrations of 30 g/L, which also allowed satisfactory fermentation values (8.51 g/L butanol and 0.328 g/g YB/L yield). On the other hand, the best YB/L yields (0.428 g/g; which is close to the theoretical value) were obtained for initial lactose concentrations of 40 g/L, attaining a value of 52% lactose consumption and 8.91 g/L butanol. Therefore, the ABE fermentation could be a feasible solution to treat cheese whey and remove lactose, obtaining acceptable amounts of butanol.

Effect of the low-fat Cheddar cheese manufacturing process on the viability of Bifidobacterium animalis subsp. lactis, Lactobacillus rhamnosus, Lactobacillus paracasei/casei, and Lactobacillus plantarum isolates

The impact of the Cheddar cheese manufacturing process on the viability of five new probiotic candidates was evaluated in this study. Decreases in pH, changes in proteolysis, and sugar and acid contents during ripening were also determined. The Bifidobacterium animalis subsp. lactis populations decreased after the cooking step, whereas the Lactobacillus plantarum, Lactobacillus paracasei/casei, and Lactobacillus rhamnosus populations gradually increased. Salting had no impact on bifidobacteria counts, whereas the growth of lactobacilli slowed but then started again during the curd-pressing step. The bifidobacteria counts in cheese decreased greatly after 14 days of ripening, whereas the lactobacilli counts stayed stable or increased. Bifidobacteria produced acetic acid during cheese production and, in smaller quantities, during ripening, whereas L. plantarum produced acetic acid only during cheese ripening. Some strains had higher viability and were therefore better candidates for use as probiotics in low-fat Cheddar cheese.

“Memorized” modifications on Listeria monocytogenes’ membrane lipids and fatty acid profile after its survival on soft white feta-type cheese

The ability of Listeria monocytogenes to adapt to low temperature, low pH, and osmotic stress, to withstand cleaning and disinfection agents, to induce stress-related cross-protection responses, and to form biofilms, enables it to prevail and survive most of the common safety measures employed in industrial-scale food processing to ensure food safety. The objective of this study was to determine the changes that occur in the lipid composition of the membrane of L. monocytogenes under the conditions of the manufacture and storage of a laboratory-prepared soft cheese (feta type). The results show that L. monocytogenes cells present in the raw milk may survive the cheese manufacturing process as well as the storage period and that the history of the inoculated cells has an effect on their behavior during storage of the cheese. The bacterium seems to follow different pathways and adopt different strategies to preserve the optimal fluidity and functions of the membrane depending on the length of storage time and the history of the inoculated cells. In this context, cells derived from pre-inoculated cells grown in optimal or acidic conditions showed an increase in the number of straight chain fatty acids (SCFA) relative to branched ones (BCFA), without altering the ratio of BCFA C15:0 to BCFA C17:0 and the ratio of iso to anteiso FA. Alternatively, those cells derived from pre-inoculated cells grown in presence of benzalkonium chloride followed a different pathway. These cells achieved a balance between optimal fluidity and solid phase membrane not only by changes in SCFA content, but also by changes in the ratios of BCFA C15:0 to C17:0 and of iso to anteiso fatty acids. This latter approach to maintain membrane fluidity seems to be paired with the different survival trends of the bacterium under the conditions of this study.

Optimization of the production and characterization of milk-clotting enzyme from Bacillus subtilis isolated from marine sponge

Background and objectives Milk-clotting enzyme (MCE) has important applications in the dairy industry and in the cheese-manufacturing process. Because of the increase in cheese consumption and the low supply of calf rennets, there is a need for a suitable rennet substitute from an appropriate source. The present investigation aims at microbial production of MCE and medium optimization for maximal enzyme production by the most potent strain. Partial purification and the properties of the partially purified enzyme are also studied. Materials and methods In the present study several microorganisms were tested for production of the MCE. MCE/caseinase ratio was investigated and was used as the key parameter for selection of the most potent strain and for medium optimization. Medium optimization experiments were carried out in an attempt to increase the enzyme productivity by the most potent strain. The produced enzyme was partially purified using ammonium sulfate at 50% concentration and the properties of the partially purified enzyme were investigated. Results and conclusion Among all the tested bacteria the marine sponge Pseudoceratina arabica isolated bacterium (isolate I) showed the highest milk-clotting activity. This isolate was used for MCE production throughout this study and it was identified as Bacillus subtilis KU710517. Maximum enzyme productivity (581.8 U/ml) and maximum MCE/caseinase ratio were obtained using a medium containing 50 g/l wheat bran with xylose and yeast extract as carbon and nitrogen sources. For the partially purified enzyme, the optimal temperature and pH were 85°C and 5.0, respectively. The enzyme was thermally stable at 45°C and retained 100% activity after 90 min. At 50°C for the same period of time it retained about 82% activity. However, at 60°C, the enzyme lost about 70% of its original activity after 30 min. The activation energy (Ea) of the enzyme was calculated as 6.95 kcal/mol. Km and Vmax values were 4.6 mg/ml and 2933 U/mg protein, respectively.

The 9-MilCA method as a rapid, partly automated protocol for simultaneously recording milk coagulation, curd firming, syneresis, cheese yield, and curd nutrients recovery or whey loss

The aim of this study was to propose and test a new laboratory cheesemaking procedure [9-mL milk cheesemaking assessment (9-MilCA)], which records 15 traits related to milk coagulation, curd firming, syneresis, cheese yield, and curd nutrients recovery or whey loss. This procedure involves instruments found in many laboratories (i.e., heaters and lacto-dynamographs), with an easy modification of the sample rack for the insertion of 10-mL glass tubes. Four trials were carried out to test the 9-MilCA procedure. The first trial compared 8 coagulation and curd firming traits obtained using regular or modified sample racks to process milk samples from 60 cows belonging to 5 breeds and 3 farms (480 tests). The obtained patterns exhibited significant but irrelevant between-procedure differences, with better repeatability seen for 9-MilCA. The second trial tested the reproducibility and repeatability of the 7 cheesemaking traits obtained using the 9-MilCA procedure on individual samples from 60 cows tested in duplicate in 2 instruments (232 tests). The method yielded very repeatable outcomes for all 7 tested cheese yield and nutrient recovery traits (repeatability >98%), with the exception of the fresh cheese yield (84%), which was affected by the lower repeatability (67%) of the water retained in the curd. In the third trial (96 tests), we found that using centrifugation in place of curd cooking and draining (as adopted in several published studies) reduced the efficiency of whey separation, overestimated all traits, and worsened the repeatability. The fourth trial compared 9-MilCA with a more complex model cheese-manufacturing process that mimics industry practices, using 1,500-mL milk samples (72 cows, 216 tests). The average results obtained from 9-MilCA were similar to those obtained from the model cheeses, with between-method correlations ranging from 78 to 99%, except for the water retained in the curd (r=54%). Our results indicate that new 9-MilCA method is a powerful research tool that allows the rapid, inexpensive, and partly automated analysis processing 40 samples per day with 2 replicates each, using 1 lacto-dynamograph, 2 heaters, and 3 modified sample racks, and yields a complete picture of the cheesemaking process (e.g., milk gelation, curd firming, syneresis, and whey expulsion) as well as the cheese yield and the efficiency of energy or nutrients retention in the cheese or loss in the whey.

Incorporación de la proteína del suero lácteo en un queso fresco.

El objetivo del presente trabajo fue evaluar el efecto de la incorporación de proteína de suero (PS) en un queso fresco. Se obtuvo el rendimiento, composición química proximal, contenido de triptófano, propiedades de textura y agrado sensorial de consumidores. El estudio se realizó en una quesería del cantón de San Carlos, Costa Rica, durante el año 2011. La proteína recuperada del suero se incorporó en el proceso de elaboración del queso previo de agregar el cuajo microbiano, y se evaluaron cuatro niveles de adición, incluido un control. Los quesos suplementados presentaron un agrado entre 6,8 y 7,1. Los productos con adición de 75 y 120 g de PS/kg leche no mostraron diferencias significativas respecto al queso sin suplementar; en tanto que, el agrado del queso con 150 g PS/kg leche fue menor al presentado por control (p<0,05). Un análisis de conglomerados indicó la existencia de dos grupos de consumidores: uno, formado por el 65% de los panelistas, donde el agrado no fue afectado por la proteína suplementada, y otro donde la adición de proteína de suero afectó negativamente esta valoración. La incorporación de proteína de suero en el queso produjo un aumento significativo en el rendimiento y en la relación proteína/agua y una reducción en su contenido de grasa (p<0,05). Sin embargo, hubo cambios en la estructura del queso que provocaron la disminución de algunas propiedades de textura y generaron cambios en sus propiedades sensoriales que redujeron el agrado del producto en un grupo representativo de consumidores.

Potential use of scotta, the by-product of the ricotta cheese manufacturing process, for the production of fermented drinks.

In the present work, the use of scotta as substrate for bacterial fermentation was studied with the objective of obtaining a drink from transformation of this by-product. Scotta retains most of the lactose of the milk and it is normally colonized by a natural microbiota. A treatment was devised to reduce the autochthonous microbial populations in order to reduce competition towards the inoculated bacterial strains. Nine lactic acid bacteria (LAB) were assessed for their capability to develop in scotta. They evidenced different behaviors regarding growth rate, acidification capability and nitrogen consumption. A co-inoculum of three LAB, namely a Streptococcus thermophilus, a Lactobacillus delbrueckii subsp. bulgaricus and a Lb. acidophilus strains, chosen among those giving the best performances in single-strain fermentation trials, gave abundant (close to 10(9) cfu/ml) and balanced growth and lowered pH to 4.2, a value similar to that of yogurt. These results show that scotta may have potential as a substrate for bacterial growth for the production of a fermented drink. Further studies are needed to optimize the organoleptic aspects of the final product.

Investigation of the protective effect of whey proteins on lactococcal phages during heat treatment at various pH

The incorporation of whey protein concentrates (WPC) into cheese is a risky process due to the potential contamination with thermo-resistant phages of lactic acid bacteria (LAB). Furthermore, whey proteins can protect phages during heat treatment, thereby increasing the above risk. The main objective of this work was to understand this protective effect in order to better control LAB phages and maximize whey recycling in the cheese industry. First, the inactivation of a previously characterized thermo-resistant lactococcal virulent phage (P1532) was investigated at 95°C in WPC, in individual whey components β-lactoglobulin, α-lactalbumin, and bovine serum albumin as well as under different heat and pH conditions. The structural changes of the tested proteins were also monitored by transmission FTIR spectroscopy. Phage inactivation results indicated that the protective effect of whey proteins was pH and time dependent at 95°C and was not restricted to one component. FTIR spectra suggest that the protection is related to protein molecular structures and to the level of protein aggregates, which was more pronounced in acidic conditions. Moreover, the molecular structure of the three proteins tested was differently influenced by pH and the duration of the heat treatment. This work confirms the protective effect of WPC on phages during heat treatment and offers the first hint to explain such phenomenon. Finding the appropriate treatment of WPC to reduce the phage risk is one of the keys to improving the cheese manufacturing process.

Phenotypic analysis of cheese yields and nutrient recoveries in the curd of buffalo milk, as measured with an individual model cheese-manufacturing process

Traits associated with cheese yield and milk nutrient recovery in curd are used to describe the efficiency of the cheese-making process. This is fundamental for all dairy species, including the Italian Mediterranean buffalo, which is largely used for milk production aimed at the dairy industry. To assess cheese-making traits among buffalo, a model cheese-manufacturing process was tested; it was capable of processing 24 samples per run, using 0.5-L samples of milk from individual buffalo. In total, 180 buffalo reared in 7 herds located in Northeast Italy were sampled once. Briefly, each sample was weighed and heated (35°C for 30min), inoculated with starter culture (90min), and mixed with rennet (51.2 international milk-clotting units/L of milk). After 10min of gelation, the curd was cut; 5min after the cut, the curd was separated from the whey, and the curd was subjected to draining (for 30min) and pressing (18h). The curd and whey were weighed, analyzed for pH and the total solid, fat, lactose, and protein contents, and subjected to estimation of the energy content. Three measures of cheese yield (%CY), %CYCURD, %CYSOLIDS, and %CYWATER, were computed as the ratios between the weight of the curd, the curd dry matter, and the water retained in the curd, respectively, and the weight of the milk processed. These traits were multiplied by the daily milk yield to define the 3 corresponding measures of daily cheese yield (dCY, kg/d). The milk component recoveries (REC) in the curd, RECFAT, RECPROTEIN, and RECSOLIDS, represented the ratios between the weights of the fat, protein, and total solids in the curd, respectively, and the corresponding components in the milk. Finally, energy recovery (RECENERGY) was estimated. The values for %CYCURD, %CYSOLIDS, %CYWATER, RECPROTEIN, RECFAT, RECSOLIDS, and RECENERGY averaged 25.6, 12.7, 12.9, 80.4, 95.1, 66.7, and 79.3%, respectively, indicating that buffalo milk has a higher aptitude to cheese-making than bovine milk. The effect of days in milk was the most important source of variation for %CY, RECPROTEIN, and the overall recoveries (which showed higher values toward the end of lactation), whereas parity did not appear to influence any of the investigated traits. The cheese-making procedure tested allowed us to assess the variability of and relationships among different cheese yield traits, recovery traits, daily milk production traits, and milk components at the individual level.

Proteolytic and milk-clotting activities of calf rennet processed by high pressure homogenization and the influence on the rheological behavior of the milk coagulation process

This work studied the effects of high pressure homogenization (HPH) on the performance of a commercial calf rennet. The enzyme solution was processed at 50, 100, 150 and 190 MPa and then stored for up to five days at 4 °C. The effects were evaluated on the proteolytic and milk-clotting activities of the enzyme and on the rheological behavior of the milk gels obtained using the processed enzyme. HPH caused a reduction in proteolytic activity with increase in pressure (up to 52% loss of activity at 190 MPa). At the first 48 h of storage, the processed enzyme maintained its activity while the non-processed sample showed a continuous reduction in activity. The results showed that HPH processing did not alter the milk-clotting activity and the rheological tests showed high G' values for the milk coagulated with the enzyme processed at 190 MPa (7% higher after 84 min of coagulation). Thus, HPH improves the milk coagulation by calf rennet and reduces the proteolytic activity of enzyme, which may improve the quality of fresh cheeses, especially after their storage. The changes caused by HPH in the calf rennet improved the cheese manufacturing process and the quality of the product (higher consistency of the milk gel and lower proteolysis during storage). Therefore, the HPH processing of calf rennet can improve its application in the dairy industry to obtain high quality fresh cheese and an extended shelf-life.

Factors affecting variation of different measures of cheese yield and milk nutrient recovery from an individual model cheese-manufacturing process

Cheese yield (CY) is the most important technological trait of milk, because cheese-making uses a very high proportion of the milk produced worldwide. Few studies have been carried out at the level of individual milk-producing animals due to a scarcity of appropriate procedures for model-cheese production, the complexity of cheese-making, and the frequent use of the fat and protein (or casein) contents of milk as a proxy for cheese yield. Here, we report a high-throughput cheese manufacturing process that mimics all phases of cheese-making, uses 1.5-L samples of milk from individual animals, and allows the simultaneous processing of 15 samples per run. Milk samples were heated (35°C for 40 min), inoculated with starter culture (90 min), mixed with rennet (51.2 international milk-clotting units/L of milk), and recorded for gelation time. Curds were cut twice (10 and 15 min after gelation), separated from the whey, drained (for 30min), pressed (3 times, 20 min each, with the wheel turned each time), salted in brine (for 60min), weighed, and sampled. Whey was collected, weighed, and sampled. Milk, curd, and whey samples were analyzed for pH, total solids, fat content, and protein content, and energy content was estimated. Three measures of percentage cheese yield (%CY) were calculated: %CYCURD, %CYSOLIDS, and %CYWATER, representing the ratios between the weight of fresh curd, the total solids of the curd, and the water content of the curd, respectively, and the weight of the milk processed. In addition, 3 measures of daily cheese yield (dCY, kg/d) were defined, considering the daily milk yield. Three measures of nutrient recovery (REC) were computed: RECFAT, RECPROTEIN, and RECSOLIDS, which represented the ratio between the weights of the fat, protein, and total solids in the curd, respectively, and the corresponding components in the milk. Energy recovery, RECENERGY, represented the energy content of the cheese compared with that in the milk. This procedure was used to process individual milk samples obtained from 1,167 Brown Swiss cows reared in 85 herds of the province of Trento (Italy). The assessed traits exhibited almost normal distributions, with the exception of RECFAT. The average values (± SD) were as follows: %CYCURD=14.97±1.86, %CYSOLIDS=7.18±0.92, %CYWATER=7.77±1.27, dCYCURD=3.63±1.17, dCYSOLIDS=1.74±0.57, dCYWATER=1.88±0.63, RECFAT=89.79±3.55, RECPROTEIN=78.08±2.43, RECSOLIDS=51.88±3.52, and RECENERGY=67.19±3.29. All traits were highly influenced by herd-test-date and days in milk of the cow, moderately influenced by parity, and weakly influenced by the utilized vat. Both %CYCURD and dCYCURD depended not only on the fat and protein (casein) contents of the milk, but also on their proportions retained in the curd; the water trapped in curd presented an higher variability than that of %CYSOLIDS. All REC traits were variable and affected by days in milk and parity of the cows. The described model cheese-making procedure and the results obtained provided new insight into the phenotypic variation of cheese yield and recovery traits at the individual level.

Genetic parameters of different measures of cheese yield and milk nutrient recovery from an individual model cheese-manufacturing process

Cheese yield (CY) is an important technological trait in the dairy industry, and the objective of this study was to estimate the genetic parameters of cheese yield in a dairy cattle population using an individual model-cheese production procedure. A total of 1,167 Brown Swiss cows belonging to 85 herds were sampled once (a maximum of 15 cows were sampled per herd on a single test day, 1 or 2 herds per week). From each cow, 1,500 mL of milk was processed according to the following steps: milk sampling and heating, culture addition, rennet addition, gelation-time recording, curd cutting, whey draining and sampling, wheel formation, pressing, salting in brine, weighing, and cheese sampling. The compositions of individual milk, whey, and curd samples were determined. Three measures of percentage cheese yield (%CY) were calculated: %CYCURD, %CYSOLIDS, and %CYWATER, which represented the ratios between the weight of fresh curd, the total solids of the curd, and the water content of the curd, respectively, and the weight of the milk processed. In addition, 3 measures of daily cheese yield (dCY, kg/d) were defined, considering the daily milk yield. Three measures of nutrient recovery (REC) were computed: RECFAT, RECPROTEIN, and RECSOLIDS, which represented the ratio between the weights of the fat, protein, and total solids in the curd, respectively, and the corresponding nutrient in the milk. Energy recovery, RECENERGY, represented the energy content of the cheese versus that in the milk. For statistical analysis, a Bayesian animal model was implemented via Gibbs sampling. The effects of parity (1 to ≥4), days in milk (6 classes), and laboratory vat (15 vats) were assigned flat priors; those of herd-test-date, animal, and residual were given Gaussian prior distributions. Intra-herd heritability estimates of %CYCURD, %CYSOLIDS, and %CYWATER ranged from 0.224 to 0.267; these were larger than the estimates obtained for milk yield (0.182) and milk fat content (0.122), and similar to that for protein content (0.275). Daily cheese yields showed heritability estimates similar to those of daily milk yield. The trait %CYWATER showed a highly positive genetic correlation with %CYSOLIDS (0.87), whereas their phenotypic correlation was moderate (0.37), and the fat and protein contents of milk showed high genetic correlations with %CY traits. The heritability estimates of RECPROTEIN and RECFAT were larger (0.490 and 0.208, respectively) than those obtained for the protein and fat contents of milk, and the genetic relationships between RECPROTEIN and RECFAT with milk protein and fat content were low or moderate; RECPROTEIN and RECFAT were moderately correlated with the %CY traits and highly correlated with RECSOLIDS and RECENERGY. Both RECSOLIDS and RECENERGY were heritable (0.274 and 0.232), and showed high correlations with each other (0.96) and with the %CY traits (0.83 to 0.97). Together, these findings demonstrate the existence of economically important, genetically determined variability in cheese yield that does not depend solely upon the fat and protein contents of milk, but also relies on the ability of the coagulum to retain the highest possible proportions of the available protein, fat, and water. Exploitation of this interesting genetic variation does not seem to be feasible through direct measurement of the phenotype in cows at the population level. Instead, further research is warranted to examine possible means for indirect prediction, such as through assessing the mid-infrared spectra of milk samples.

A kiwi juice aqueous solution as coagulant of bovine milk and its potential in Mozzarella cheese manufacture

In this work a kiwi juice aqueous solution was prepared and used as coagulant enzyme in the manufacturing process of mozzarella cheese. The aqueous solution does exhibit high levels of milk-clotting activity probably due to the presence of the clotting enzyme actinidin in mixture with other kiwi fruit proteolityc enzymes. The mozzarella cheese was manufactured from bovine milk with a yield of 10.6% being in the range of that routinely obtained during cheese manufacture. A preliminary evaluation of the cheeses flavor showed positive results and lack of bitterness. Finally, in view of a future marketing of the kiwi juice aqueous solution as plant coagulant, it is shown that the aqueous solution stored for 20 days at −20°C maintains both the clotting and proteolytic activities unaffected. Due to its properties as well as to the accessibility of the primary source for the preparation of the aqueous solution, it might represent a good candidate for calf rennet substitution, provided that further research on cheese properties will be carried out.

F123 近赤外レーザー誘起表面波を用いたチーズ製造プロセス粘性率センシング技術の開発(OS-8:熱物性・計測(1))

F123 近赤外レーザー誘起表面波を用いたチーズ製造プロセス粘性率センシング技術の開発(OS-8:熱物性・計測(1))