This study was conducted to develop and evaluate several formulas which predict Mozzarella cheese yield from fat and protein content of milk and moisture content of cheese. During a one month period, 107 samples of milk and cheese were collected at Olympia Cheese Company, Olympia, Washington. Milk samples were analyzed for fat and protein content. Cheese samples were analyzed for fat, protein and moisture content. Three models were derived to predict the yield of Mozzarella cheese. The three models were statistically fitted to the data by applying the Gauss-Newton non-linear least squares method of iteration. The differences among the three models in predicting cheese yield were insignificant. Any of the three formulas can predict yield of Mozzarella cheese reasonably well.

Low fat Mozzarella cheese was made using exopolysaccharide-producing starter cultures consisting of single strains of Streptococcus thermophilus MR-1C and Lactobacillus delbrueckii ssp. bulgaricus MR-1R with or without the addition of mesophilic exopolysaccharide-producing adjunct mixed culture consisting of Lactococcus lactis ssp. lactis and Lactococcus lactis ssp. cremoris. A control cheese was made using a non-exopolysaccharide-producing starter culture consisting of S. thermophilus TA061 and Lactobacillus helveticusLH100. Cheeses were analyzed for moisture, melt, fat, and protein. Cheeses made with the addition of the mesophilic exopolysaccharide-producing adjunct culture showed significant differences in moisture, but not in melting properties when compared to cheeses made without adjunct culture. Cheeses made with both the exopolysaccharide-producing starter and exopolysaccharide-producing adjunct cultures showed a 4% increase in moisture, but the use of the exopolysaccharide-producing starter cultures alone produced a 3% increase in moisture over the control cheese. Melt also increased in these cheeses as moisture increased. The same cultures were used to determine the effects on moisture when the cheesemaking procedure was scaled up from 10-kg vats to using 454-kg horizontal blade double-O vats, and hand stretching was replaced by an Alfa Laval cooker stretcher machine. Cheese made using the exopolysaccharide-producing cultures showed a 2% increase in moisture over cheese made using non-exopolysaccharide-producing cultures. All of the cheeses made in the double-0 vats showed a decrease in moisture compared to cheeses made in the 10-kg stainless steel vats . Cheeses with elevated moisture levels showed increased melt.

Bacteriophage infection of Streptococcus thermophilus is a growing concern in the mozzarella cheese industry. One method to control this problem may be to replace S. thermophilus with a starter coccus from a different genus of lactic acid bacteria. This work evaluated the possibility of using genetically modified Pediococcus spp. for this approach. Electroporation was used to introduce genes for lactose utilization from Lactococcus lactis into strains of P. acidilactici and P. pentosaceus. The resulting lactose-positive transformants, P. acidilactici SAL and P. pentosaceus SPL-2, rapidly reduced the pH of lactose broth, accumulated [14C]lactose at a rate higher than a lactococcal control, and showed relatively high phospho-β-galactosidase activity. When paired with Lactobacillus helveticus LH100 in 9% reconstituted skim milk, P. acidilactici SAL and P. pentosaceus SPL-2 demonstrated synergistic growth with LH100. Milk fermented with Pediococcus-LH100 starter pairs also contained significantly less free galactose than milk fermented with a control starter blend of LH100 and S. thermophilus TA061. Mozzarella cheese made with lactose-positive Pediococcus-LH100 blends was compositionally similar to cheese made with the control starter blend, but production required 60-90 additional minutes. In an attempt to decrease the time required to produce mozzarella, Pediococcus spp. were transformed with lactococcal genes from an extracellular serine proteinase ora n oligopetpide transport system. Constructs which expressed each system were obtained, but these strains did not display improvement in the ability to clot 9% reconstituted skim milk.Studies to screen P. acidilactici and P. pentosaceus for lysogeny detected temperate bacteriophage in three strains of P. acidilactici. Morphological characterization of these new phages demonstrated that they had small isometric heads with non-contractile tails and thus belonged to the B I group of the family Siphovirdae. Further characterization based on DNA-DNA homology and protein profiles suggested that the P. acidilactici phages can be separated into at least two different species. As a whole, the results reported here suggest that due to their slower growth in milk, P. acidilactici SAL and P. pentosaceus SPL-2 cannot be used as direct replacements for S. thermophilus but may be suited for use as adjuncts to the traditional S. thermophilus/Lactobacillus sp. starter blend.

Listeria monocytogenes continues to challenge the dairy industry in causing post-process contamination of cheeses. To reduce risk of contamination, it is crucial to understand the growth and survival of pathogenic bacteria in cheese products and to develop post-process mitigation strategies. This study evaluated the fate of pathogens in reduced and regular sodium Mozzarella cheese, and the potential of Supercritical Fluid Extraction with CO2 (SFE) to reduce Listeria innocua on Mozzarella and Queso Fresco. The survival of L. monocytogenes, Salmonella, and E.coli O157:H7 (2-3 log CFU/g) in reduced sodium Mozzarella (1.62%), compared to regular sodium Mozzarella cheese (2.15%) at 4ºC and 12ºC for 90 and 30 days, respectively, was evaluated. Salmonella and E. coli O157:H7 populations decreased over incubation time at both temperatures and no difference (pListeria monocytogenes population also decreased during incubation time at 4°C regardless of the sodium concentration in Mozzarella cheese. However, there was a difference in the population of L. monocytogenes for regular and reduced sodium incubated 12°C, and its populations increased 1 log CFU/g in reduced sodium Mozzarella cheese. Additionally, this study determined the bactericidal effect of SFE on the population of L. innocua, a surrogate for L. monocytogenes, in Mozzarella and Queso Fresco cheese (6 log CFU/g) treated with SFE at two pressures and temperatures (120 bar at 40°C and 150 bar at 50°C) for 30 min. SFE treatment at 120 bar, 40°C for 30 min decreased L. innocua by approximately 3.0 and 3.5 log CFU/g in Mozzarella and Queso Fresco cheeses, respectively. SFE at 150 bar and 50°C reduced L. innocua by approximately 3.78 and 5.2 log CFU/g in Mozzarella and Queso Fresco cheeses, respectively. Since SFE had a minimal effect on the physico-chemical characteristics of the cheeses assayed, the results suggest SFE might be used to reduce L. monocytogenes in cheeses without negatively impacting product quality.

No description available.

Muçarela de búfala é um queijo fresco, de massa filada, que apresenta características como coloração branca, sabor adocicado e alto valor nutricional e que tem grande aceitação pelos consumidores, dispostos a pagar preços diferenciados pela peculiaridade do produto. No entanto, o queijo está sujeito à violação de autenticidade, tanto pela sazonalidade da produção do leite da búfala quanto pelo alto preço do leite e do queijo, quando comparado aos similares oriundos da vaca, bem como à contaminação microbiana. Assim, este trabalho teve por objetivos avaliar a ocorrência de fraude na muçarela de búfala por adição de leite de vaca, e a influência da sazonalidade da produção do leite de búfala na frequência desta adulteração, bem como avaliar a presença de alguns patógenos no queijo comercializado no município de São Paulo. Amostras de muçarela de bolinha cujo rótulo identificava o uso exclusivo de leite de búfala foram submetidas à pesquisa de DNA bubalino e bovino, usando primers para detecção do gene citocromo b (cytb), e à análise microbiológica. A fraude foi detectada em 73% das amostras (77/106), não havendo influencia da sazonalidade; em duas amostras (2/106) apenas o DNA bovino foi detectado. Do ponto de vista microbiológico, todas as amostras apresentaram ausência de Listeria monocytogenes e de Salmonella spp. em 25 gramas, mas 7% (10/138) foram consideradas impróprias para o consumo humano por apresentar Coliformes termotolerantes e/ou Staphylococcus coagulase positiva acima dos limites estabelecidos pela legislação vigente. Conclui- se que a fraude por adição de leite de vaca é muito frequente e não é motivada apenas pela redução sazonal da oferta do leite bubalino. Além disso os problemas microbiológicos detectados estão associados às inadequadas condições de higiene da matéria prima e/ou do processo de fabricação e/ou abuso de temperatura de armazenamento do queijo. / Buffalo mozzarella is a fresh cheese, filada mass, with characteristics such as white color, sweet taste and high nutritional value and has great acceptance by consumers willing to pay different prices for the uniqueness of the product. However, the cheese is subject to violation of authenticity, both the seasonality of production of milk the buffalo as by the high price of milk and cheese when compared to similar coming from the cow as well as to microbial contamination. This work aimed to evaluate the occurrence of fraud in buffalo mozzarella by adding cow\'s milk, and the influence of the seasonality of production of buffalo milk in the frequency of this tampering and evaluate the presence of some pathogens in cheese marketed in São Paulo. Mozzarella samples of marble whose label identified the exclusive use of buffalo milk were subjected to DNA research buffalo and cattle, using primer for detection of cytochrome b gene (cytb), and microbiological analysis. The fraud was detected in 73% of samples (77/106), with no influence of seasonality; in two samples (2/106) only the bovine DNA was detected. From a microbiological point of view, all samples showed no Listeria monocytogenes and Salmonella spp. 25 grams but 7% (10/138) were considered unfit for human consumption by presenting thermotolerant coliforms and / or coagulase positive Staphylococcus above the limits established by law. It is concluded that fraud by adding cow\'s milk is very common and is not motivated only by the seasonal reduction in supply of buffalo milk; microbiological problems encountered are related to inadequate hygiene conditions of raw materials and / or fabrication process and / or storage temperature abuse cheese.

As fat is removed from Mozzarella cheese, the resulting increase in protein content causes the cheese to become tough, thus decreasing the desired physical characteristics of meltability and stretch. Low-fat (6% fat) Mozzarella cheese was manufactured with the addition of several levels of a Lactococcus lactis adjunct culture that was proteinase positive and lactose deficient in an attempt to improve these physical properties. During cheese manufacture , milk was acidified to pH 6.0, then inoculated with Lactobacillus helveticus and Streptococcus thermophilus. Experimental vats were also inoculated with either 0.25, 0.50, or 1.0% of the adjunct culture. Cheeses made with the adjunct culture had increased melt properties at d 1. During the first 14 d of storage, cheeses manufactured with 0.50% and 1.0% adjunct culture melted more readily than the control; by 28 d, the meltability of all cheeses was similar. Breakdown of cheese body was more rapid in the experimental cheeses and was particularly apparent during shredding. The increase in softness was presumed to be the result of increased proteolysis in the cheeses. There were no significant differences in melt viscosity between control and experimental cheeses. Storage time, however, was significant, and between d 14 and d 28, melt viscosity decreased for all cheeses. Protein hydrolysis was measured using SDS-PAGE, but no differences were observed in the disappearance of intact caseins. In the second part of this study, part-skim (18% fat) Mozzarella cheese was manufactured from milk standardized to a casein-to-fat ratio of 1.2 and inoculated with L. helveticus strain and S. thermophilus strain. Low-fat (6% fat) Mozzarella cheese was manufactured from milk with a casein-to-fat ratio of 4.2 and inoculated with the same starter culture with (or without) addition of the proteinase positive, lactose deficient adjunct culture. The cheese was molded into 1.5-lb blocks and stored at 4°C. Meltability and melt viscosity of the cheese were measured during 28 d storage. Disappearance of αs1-casein and ß-casein was measured using free solution capillary electrophoresis, which separated intact proteins and large peptides. Micellar electrokinetic capillary chromatography was used to study the appearance of small peptides (<30 >kDa) during storage. After 28 d storage, there were significant decreases in the amount of intact αs1-casein remaining after 28 d, but no measurable change in ß-casein in either the part-skim or low-fat cheeses. In part-skim cheese, 71% αs1-casein remained, but in the low-fat cheeses only 20% intact αs1-casein remained after 28 d. If adjunct culture was used in low-fat cheese, then only 14% a 5 1-casein was found after 28 d. A similar increase in proteolysis in the low-fat cheeses was observed based on the amount of small peptides produced. Part of these differences may be a function of increased moisture content of the low-fat cheese, 61% vs 51% in part-skim cheese. During storage, part-skim Mozzarella showed a typical increase in melt with a corresponding decrease in melt viscosity. Melt increased from 10.6 cm at d 1 to 16.9 cm at d 28; melt viscosity at 80°C decreased from 1.0 x 106 cP at d 1 to 2.1 x 105 cP at d 28. There was less change in melt in the low-fat cheese during storage, 8.9 cm at d 1 and 10.9 cm at d 28. Melt viscosity decreased from 4.8 x 105 cP at d 1 to 1.9 x 105cP at d 28. It appears that adding the adjunct culture increased initial meltability of the low-fat cheese by accelerating proteolysis during the first 14 d but caused an increase in viscosity and decrease in melt after 14 d of refrigerated storage.

This study sought to investigate the role of the C55 undecaprenol lipid carrier in the production of exopolysaccharide (EPS), the effect of exopolysaccharide producing (EPS+) starter cultures on the viscosity of Mozzarella cheese whey, and the possible protective characteristics of capsular EPS against freezing and freeze drying. Efforts to investigate the role of the lipid carrier in EPS production employed pAMbacA, a plasmid that encodes an enterococcallipid kinase that confers bacitracin resistance by increasing intracellular levels of undecaprenol phosphate lipid carrier. Unfortunately, this avenue of study was thwarted by the inability to demonstrate bacA expression in a model dairy lactic acid bacterium, Lactococcus lactis. To study the effect of EPS+ cultures on cheese whey, Mozzarella cheese was made with starters consisting of Lactobacillus helveticus (LH100) paired with one of four Streptococcus thermophilus strains. These strains included a capsular EPS producer (Cps+) MR-1C; a non-exopolysaccharide producing negative mutant (EPS-) of MR-1C, DM10; a ropy EPS producer, MTC360; and a non-EPS producing industrial strain, TA061. Results showed that Mozzarella cheese made with a Cps+ or ropy EPS+ S. thermophilus strain had significantly higher moisture levels than cheese made with non-exopolysaccharide producing (EPS-) streptococci. Melt properties were also better in cheeses with higher moisture. Viscosity measurements of unconcentrated and ultrafiltered (5-fold concentrated) whey showed that ultrafiltered whey from cheeses made with S. thernzophilus MTC360 was significantly higher in viscosity than whey from cheeses made with MR-1C, TA061, or DM10. There was no significant difference in the viscosity of unconcentrated or concentrated whey from cheese made with S. thermophilus MR-1C and cheese made with the commercial starter culture TA061. The results indicated that non-ropy, encapsulated exopolysaccharideproducing S. thermophilus strains can be used to achieve higher cheese moisture levels and to improve the melt properties of Mozzarella cheese without significantly increasing cheese whey viscosity. Finally, S. thermophilus MR-1C and DM10 were subjected to freezing and freeze drying to test for possible protective effects of the capsular exopolysaccharide. Analysis of variance of cell counts taken before and after freezing or freeze drying cycles revealed there was no significant difference between the viability of these strains.

Experiment A explored the influence of sodium on direct acid, nonfat Mozzarella cheese. Cheeses with differing salt levels were obtained by varying dry salt applications (none, 0.5%, and 1.0% NaCl w/w) and hot brine stretching (0%, 5%, and 10% NaCl wt/v). Salt application and salt content influenced cheese moisture, meltability, expressible serum, micro- and ultra-structure, and color. Moisture was highest when cheese was salted before stretching (P = 0.03) . Melt was lowest in cheeses that were unsalted (P = 0.05). Cheeses stretched in salt brine had < 1% of the amount of expressible serum found in unsalted cheese (P < 0.0001). Unsalted cheeses had a more open structure with pockets of serum distributed throughout the protein matrix giving it an opaque, white appearance. Salted cheeses had a more homogeneous protein matrix lacking light scattering surfaces, resulting in a translucent cheese. Neither salt concentration nor method of salting affected the calcium content of the cheeses (P > 0.05). Experiment B explored the influence of calcium, moisture, and pH on cheese structure and functionality. Cheeses were manufactured using combinations of citric and acetic acids. Addition of EDTA to the whey during cooking, CaCl2 fortification, and extended drain times were used to produce eight cheeses in a 23 factorial design with target pH levels of 5.8 and 5.3, 70% and 66% moisture, and 0.6% and 0.3% calcium levels. EDTA was unsuccessful in removing calcium from pH 5.8 cheese. Adding CaCh successfully increased the calcium level of pH 5.3 cheese. Cheese with 0.3% calcium had greatest melt, decreased hardness and increased adhesiveness. Cheese with 0.6% calcium had decreased melt and adhesiveness, and increased hardness. When calcium content was held at 0.6% there was no significant difference in melting even when pH was varied from pH 5.8 to pH 5.3 . The microstructure of the 0.6% calcium cheeses had an increase in protein folds and serum pockets. Low calcium cheeses had a very homogeneous structure. Directly acidified nonfat Mozzarella cheese manufactured with 1.0% dry salt and hot water stretching produced the best cheese. This cheese contained 0.4% salt, 0.4% calcium, no expressible serum, and good meltability.

This study investigated the role of exopolysaccharide (EPS) in cheese moisture retention. Analysis of low-fat Mozzarella cheese made with different combinations of EPS-producing (Streptococcus thermophilus MR-1C and Lactobacillus delbrueckii ssp. bulgaricus MR-lR) and non-EPS-producing (S. thermophilus TA061 and L. helveticus LH100) starters showed significantly higher moisture levels in cheese made with S. thermophilus MR-1C. To determine if the S. thermophilus MR-1C EPS was responsible for increased moisture retention, gene replacement was used to inactivate the epsE gene in this bacterium. Low-fat Mozzarella cheese made with L. helveticus LH100 plus the EPS-negative mutant, S. thermophilus DM1O, had significantly lower moisture content than cheese made with LH100 and MR-1C, which confirmed that the MR-1C capsular EPS was responsible for the water-binding properties of this bacterium in cheese. Chemical analysis of the S. thermophilus MR-lC EPS indicated that it had a repeating unit composed of D-galactose, L-rhamnose, and L-fucose in a ratio of 5:2:1. Interestingly, carbohydrate utilization tests showed that DMlO had acquired the ability to ferment galactose.