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PubMed2004

Evaluation of salt whey as an ingredient in processed cheese.

The objective of this research was to determine whether salt whey, obtained from a traditional Cheddar cheese manufacturing process, could be used as an ingredient in processed cheese. Due to its high salinity level, salt whey is underutilized and leads to disposal costs. Consequently, alternative uses need to be pursued. The major components of salt whey (salt and water) are used as ingredients in processed cheese. Three replicates of pasteurized processed cheese (PC), pasteurized processed cheese food (PCF), and pasteurized processed cheese spread (PCS) were manufactured. Additionally, within each type of processed cheese, a control formula (CF) and a salt whey formula (SW) were produced. For SW, the salt and water in the CF were replaced with salt whey. The composition, functionality, and sensory properties of the CF and SW treatments were compared within each type of processed cheese. Mean melt diameter obtained for the CF and SW processed cheeses were 48.5 and 49.4 mm, respectively, for PC, and they were 61.6 and 63 mm, respectively, for PCF. Tube-melt results for PCS was 75.1 and 79.8 mm for CF and SW treatments, respectively. The mean texture profile analysis (TPA) hardness values obtained, respectively, for the CF and SW treatments were 126 N and 115 N for PC, 62 N and 60 N for PCF, and 12 N and 12 N for PCS. There were no significant differences in composition or functionality between the CF and SW within each variety of processed cheese. Consequently, salt whey can be used as an ingredient in PC without adversely affecting processed cheese quality.

Cheese↗
PubMed2005

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

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

Animals↗
PubMed2005

Impact of modifications in acid development on the insoluble calcium content and rheological properties of Cheddar cheese.

Cheddar cheese was made from milk concentrated by reverse osmosis (RO) to increase the lactose content or from whole milk. Manufacturing parameters (pH at coagulant addition, whey drainage, and milling) were altered to produce cheeses with different total Ca contents and low pH values (i.e., <5.0) during ripening. The concentration of insoluble (INSOL) Ca in cheese was measured by cheese juice method, buffering by acid-base titration, rheological properties by small amplitude oscillatory rheometry, and melting properties by UW-Melt Profiler. The INSOL Ca content as a percentage of total Ca in all cheeses rapidly decreased during the first week of aging but surprisingly did not decrease below approximately 41% even in cheeses with a very low pH (e.g., approximately 4.7). Insoluble Ca content in cheese was positively correlated (r = 0.79) with cheese pH in both RO and nonRO treatments, reflecting the key role of pH and acid development in altering the extent of solubilization of INSOL Ca. The INSOL Ca content in cheese was positively correlated with the maximum loss tangent value from the rheology test and the degree of flow from the UW-Melt Profiler. When cheeses with pH <5.0 where heated in the rheometer the loss tangent values remained low (<0.5), which coincided with limited meltability of Cheddar cheeses. We believe that this lack of meltability was due to the dominant effects of reduced electrostatic repulsion between casein particles at low pH values (<5.0).

Animals↗
PubMed2006

Interaction of brine concentration, brine temperature, and presalting on salt penetration in Ragusano cheese.

Thirty-one 3.6-kg blocks of Ragusano cheese were made on each of 6 different days (in different weeks) starting with a different batch of milk on each day. On d 1, 3, and 5, the cheeses were not presalted and on d 2, 4, and 6, all cheeses were presalted (PS). One of the 31 blocks of cheese was selected at random for analysis before brine salting (i.e., on d 0). The remaining 30 blocks were randomly divided into 2 groups of 15 blocks each; one group was placed in 18% brine (18%B) and the other group was placed in saturated brine (SB). For the 15 blocks within each of the 2 brine concentrations (BC), 5 blocks were placed in a brine tank at 12 degrees C, 5 at 15 degrees C, and 5 at 18 degrees C, and submerged for 24 d. The research objective was to determine the combined impacts (i.e., interactions) of PS the curd before stretching, BC (SB vs. 18%B), and brine temperature (BT; 12, 15, and 18 degrees C) on salt uptake, moisture content, and yield of Ragusano cheese. Although BC, BT, and PS each had their own separate impacts on salt uptake, there was little interaction of these effects on salt uptake when they were used in combination. The PS most quickly delivered salt to the interior of the cheese and was the most effective approach to salting for controlling early gas formation. There were strong separate impacts of BC, BT, and PS on cheese moisture content, moisture loss, and net weight loss, with BC having the largest separate impact on these parameters. Reducing BT reduced salt content and increased moisture, but the effects were small. The more important effect of reduced BT was to reduce growth of gas forming bacteria. The 18%B produced higher moisture, and less moisture and weight loss than SB. The effect of interactions of BC, BT, and PS on moisture loss and net weight loss were small. To achieve the maximum benefit from the various approaches to salting for controlling early gas formation in Ragusano cheese, PS combined with slightly lower BT (i.e., 15 degrees C instead of 18 degrees C) should be used. Although using 18%B instead of SB did increase salt uptake, the point at which improved salt uptake occurred due to use of 18%B did not provide benefit in prevention of early gas formation, as reported separately. However, use of 18%B instead of SB provided a 9.98% increase in cheese yield due to reduced moisture loss during brining; this would be very attractive to cheese makers. The increase in yield needs to be balanced against the risk of growth of undesirable bacteria in the 18%B and the creation of another cheese quality defect.

Animals↗
PubMed2006

Effect of formulation and manufacturing parameters on process cheese food functionality--I. Trisodium citrate.

The objective of this research was to use a Rapid Visco Analyzer to study the effect of natural cheese age, trisodium citrate (TSC) concentration, and mixing speed on process cheese food (PCF) functionality. In this study 3 replicates of natural cheese were manufactured, and a portion of each cheese was subjected to 6 different PCF manufacturing treatments at 2, 4, 6, 12, and 18 wk of ripening. These treatments were factorial combinations of 3 levels of TSC (i.e., 2.0, 2.5, and 3.0%) and 2 mixing speeds during manufacture (450 and 1,050 rpm). Functional properties of the PCF evaluated included manufacturing properties [apparent viscosity after manufacture (VAM)], unmelted textural properties (firmness), melted cheese flow properties [hot apparent viscosity (HAV)], and cheese thickening during cooling [time at 5000 cP (T5)]. All 4 parameters (VAM, firmness, HAV, and T5) were significantly affected by natural cheese age and mixing speed, whereas VAM, HAV, and T5 were also significantly influenced by the amount of TSC. The VAM and firmness decreased as cheese age increased, whereas T5 values increased as cheese age increased. Similarly, VAM, HAV, and firmness values increased because of the increased mixing speed, whereas T5 values decreased. The age x mixing speed interaction was significant for VAM and firmness. The age x concentration of the TSC interaction term was significant for VAM, whereas the age x age x TSC concentration term was significant for HAV. The results demonstrate that natural cheese age, mixing speed during manufacture, and concentration of TSC have a significant impact on process cheese functionality.

Caseins↗
PubMed2006

Monitoring the chemical and textural changes during ripening of Iranian White cheese made with different concentrations of starter.

The effect of the concentration of starter inoculated to milk on the composition, free tyrosine-tryptophan content, microstructure, opacity, and fracture stress of Iranian White cheese (IWC) was studied during 50 d of ripening in brine. Three treatments of cheese were made using 1-fold (IWC1S), 2-fold (IWC2S), and 4-fold (IWC4S) concentrations of a direct-to-vat mesophilic mixed culture containing Lactococcus lactis ssp. cremoris and Lactococcus lactis ssp. lactis as starter. As ripening progressed, moisture and protein contents of the treatments continuously decreased, whereas their total ash, salt, and salt in moisture contents increased. Fat content and pH of cheeses remained stable during ripening. The pH of cheese milk at the time of renneting, which decreased by increasing the concentration of starter (6.57, 6.49, and 6.29 for IWC1S, IWC2S, and IWC4S, respectively), significantly affected most of the chemical characteristics and opacity of cheese. Lower pH values at renneting decreased moisture and ash contents, whereas cheese protein content increased. The concentration of free tyrosine-tryptophan in curd increased at first 29 d but decreased between d 29 and 49 of aging. The changes observed in cheese whiteness followed the changes in moisture content of the treatments. As the concentration of starter inoculated to milk increased, the value of fracture stress at a given ripening time significantly decreased, leading to a less resistant body against applied stress. A similar trend was also observed for fracture strain during cheese ripening. The micrographs taken by scanning electron microscopy provided a meaningful explanation for decrease in the value of fracture stress. As the cheese ripening progressed or the concentration of starter increased, the surface area occupied by the protein fraction in cheese microstructure decreased, leading the way to lower the force-bearing component in cheese texture.

Animals↗
PubMed2006

Comparison of the compositional, microbiological, biochemical, and volatile profile characteristics of nine Italian ewes' milk cheeses.

Nine Italian ewes' milk cheeses were compared for compositional, microbiological, biochemical, and volatile profile characteristics. Mean values for the gross composition were rather similar among cheeses. The lowest pH values were found for cheeses that used primary starters. At the end of ripening, cheeses made from raw milk contained >6.0 log10 cfu/g of nonstarter lactic acid bacteria. Several species of lactobacilli were identified, but Lactobacillus plantarum and Lactobacillus paracasei were dominant. Random amplified polymorphic DNA-PCR analysis showed the biodiversity among the strains, and in several cases a relationship with the cheese of provenance. Cheeses differed mainly for secondary proteolysis, as shown by the principal component analysis applied to reversed-phase fast protein liquid chromatography data of the pH 4.6-soluble fractions and by determination of the free AA. A total of 113 volatile components were identified in the Italian Pecorino cheeses by solid-phase microextraction coupled with gas chromatography-mass spectrometry analysis. The volatile profiles of the 9 cheeses differed significantly. Quantitatively, alcohols were the most abundant chemical class for some cheeses, whereas ketones were the most abundant for other cheeses. Esters and carboxylic acids were largely found. Specific volatile components seemed to distinguish specific cheeses.

Amino Acids↗
PubMed2006

Detection and characterization of Listeria monocytogenes in Sao Jorge (Portugal) cheese production.

Listeria monocytogenes is a foodborne pathogen that can cause serious invasive disease in humans. Because human listeriosis cases have previously been linked to consumption of contaminated cheese, control of this pathogen throughout the cheese production chain is of particular concern. To understand the potential for L. monocytogenes transmission via São Jorge cheese, a Portuguese artisanal cheese variety that bears a Protected Denomination of Origin classification, 357 raw milk, curd, natural whey starter, and cheese samples representative of the production chain of this cheese were collected over one year and tested for the presence of L. monocytogenes and selected physicochemical parameters. Although neither L. monocytogenes nor other Listeria spp. were detected in whey, curd, or cheese samples, 2 of the 105 raw milk samples analyzed were positive for L. monocytogenes. These 2 raw milk isolates represented a ribotype that has previously been linked to multiple human listeriosis outbreaks and cases elsewhere, indicating the potential of these isolates to cause human listeriosis. On average, physicochemical parameters of São Jorge cheese ripened for 4 mo presented values that likely minimize the risk of L. monocytogenes outgrowth during ripening and storage (mean pH = 5.48; mean moisture = 37.79%; mean NaCl concentration = 4.73%). However, some cheese samples evaluated in this study were characterized by physicochemical parameters that may allow growth and survival of L. monocytogenes. Even though our results indicate that raw milk used for São Jorge cheese manufacture as well as finished products is rarely contaminated with L. monocytogenes, continued efforts to control the presence of this pathogen in the São Jorge cheese production chain are urged and are critical to ensure the safety of this product.

Animals↗
PubMed1992

Growth of Staphylococcus aureus and synthesis of enterotoxin during ripening of experimental Manchego-type cheese.

To study the possible presence of staphylococcal enterotoxins in Manchego-type cheese, milk was inoculated with the enterotoxigenic Staphylococcus aureus collection strains FRI-100, S6, FRI-137, and FRI-472 to a final concentration of 10,000 to 25,000 cfu/ml. Cheese was prepared following the industrial specifications and ripened for 60 d. Batches were prepared with 1 and .1% lactic acid culture and labeled with the abbreviated name of the strain and the concentration of lactic acid culture. Mean staphylococcal counts in .1% lactic bacteria cheeses were usually more than 1 log higher than the corresponding 1% ones. Staphylococcal counts declined markedly after d 35 to 42, and, by the end of ripening, they had disappeared from some cheeses. Enterotoxins were present in five of the cheeses, three prepared with .1% and two with 1% lactic bacteria. Enterotoxins detected were A and D, the enterotoxins most commonly associated with human intoxication. The maximum level of enterotoxin A detected in cheese with strain FRI-100 and with the .1% culture was 222 ng/100 g of cheese; in cheese FRI-100 with 1%, 111 ng/100 g; in cheese S6 with .1%, 769 ng/100 g; and in cheese S6 with 1%, 33 ng/100 g. Maximum level of enterotoxin D detected in cheese FRI-472 with .1% was 38 ng/100 g.

Animals↗
PubMed1997

Cheddar cheese: influence of milking frequency and stage of lactation on composition and yield.

Cheddar cheese was made from milk collected from two groups of cows milked either two or three times daily during early, mid, and late lactation. Milk from cows in late lactation had lower casein as a percentage of true protein and a higher acid degree value than did milk from cows in early lactation. Milk from cows milked three times daily had lower concentrations of milk fat and casein and higher acid degree values than did milk from cows milked twice daily, and thus this milk would be expected to result in decreased cheese yield. Cheese composition was not affected by milking frequency. Stage of lactation effects on cheese composition were confined to differences in salt content and a trend for higher moisture in cheese made from milk of cows in late lactation. Stage of lactation influenced the pH and degradation of alpha s-casein in cheese during aging. Fat and protein losses in whey at draining were higher for milk from cows in late lactation than from milk from cows in early lactation. The typical differences in fatty acid composition of milk from cows in early lactation that cause lower melting point may have caused higher fat loss in press whey. Fat loss in whey at draining was higher in cheese made from milk from cows milked three times daily than in cheese made from milk from cows milked twice daily, but the protein loss was not influenced. The ADV of milk was positively correlated to the fat loss in whey. Lower recoveries of fat and protein in cheese from milk of cows in late lactation were observed and may cause small but economically important decreases in cheese yield. Low SCC of milk from cows in late lactation may have minimized the changes in cheese composition and yield from stage of lactation.

Animals↗
PubMed2001

Effect of phage on survival of Salmonella enteritidis during manufacture and storage of cheddar cheese made from raw and pasteurized milk.

The ability of Salmonella Enteritidis to survive in the presence of phage, SJ2, during manufacture, ripening, and storage of Cheddar cheese produced from raw and pasteurized milk was investigated. Raw milk and pasteurized milk were inoculated to contain 10(4) CFU/ml of a luminescent strain of Salmonella Enteritidis (lux) and 10(8) PFU/ml SJ2 phage. The milks were processed into Cheddar cheese following standard procedures. Cheese samples were examined for Salmonella Enteritidis (lux), lactic acid bacteria, molds and yeasts, coliforms, and total counts, while moisture, fat, salt, and pH values were also measured. Salmonella Enteritidis (lux) was enumerated in duplicate samples by surface plating on MacConkey novobiocin agar. Bioluminescent colonies of Salmonella Enteritidis were identified in the NightOwl molecular imager. Samples were taken over a period of 99 days. Counts of Salmonella Enteritidis (lux) decreased by 1 to 2 log cycles in raw and pasteurized milk cheeses made from milk containing phage. In cheeses made from milks to which phage was not added, there was an increase in Salmonella counts of about 1 log cycle. Lower counts of Salmonella Enteritidis (lux) were observed after 24 h in pasteurized milk cheese containing phage compared to Salmonella counts in raw milk cheese with phage. Salmonella Enteritidis (lux) survived in raw milk and pasteurized milk cheese without phage, reaching a final concentration of 10(3) CFU/g after 99 days of storage at 8 degrees C. Salmonella did not survive in pasteurized milk cheese after 89 days in the presence of phage. However, Salmonella counts of approximately 50 CFU/g were observed in raw milk cheese containing phage even after 99 days of storage. In conclusion, this study demonstrates that the addition of phage may be a useful adjunct to reduce the ability of Salmonella to survive in Cheddar cheese made from both raw and pasteurized milk.

Animals↗
PubMed2003

[Elaboration of "cotija" type cheese made of whole milk and chickpea (Cicer arietinum L.) mixture].

The objective [corrected] of this work was to elaborate "cotija" type cheese prepared with whole milk and chickpea (Cicer arietinum L.), inoculated with S. Thermophilus and to compare its physicochemical, microbiological and sensorial characteristics with a commercial cheese. Two mixture were selected 70:30 and 80:20 (whole milk:chickpea paste). Both mixture were ground, pasteurized and inoculated with. S. Thermophilus, to develop taste and aroma. Two rennet concentrations (1:10,000 and 2:10,000), lactic acid and 50% CaCl2 solution were used in both products. Results showed that cheese made with 70:30 mixture and 1:10,000 rennet concentration gave a weak curde and 12% of total solids were lost; in the same way as 70:30 mixture and 2:10,000 rennet concentration. Nevertheless, cheese made with 80:20 mixture and 10,000 or 2:10,000 rennet concentration showed hard consistency of its curd. Addition of 10% sodium chloride solution to he 80:20 mixture cheese, made better whey drain, and a "cotija" type cheese with similar sensory characteristics as a whole milk cheese, was obtained. Chemical and physical analysis of the extended "cotija" type cheese showed 14.3 +/- 0.42 and 15.5 +/- 0.21 g/100 g of protein and lipid content respectively. Microbiologically, the extended "cotija" type cheese is pathogenic microorganisms free for human consumption. Sensory evaluation of the chickpea "extended" cheese showed a 80% acceptance while the acceptance of the whole milk commercial cheese was 90%.

Animals↗
PubMed2003

[Quantification of the probability of milk contamination by Listeria monocytogenes during manufacture of hard cheese].

BACKGROUND: The present work is concerned with the probability of contamination by Listeria monocytogenes in the artisanal manufacture of Swiss Emmental hard cheese made from raw milk. The simulation model follows the evolution of the contaminant flora from raw milk at the farm to milk mixing, storage at the cheese factory and to the cheese manufacturing process. METHODS: The simulations are based on models of predictive microbiology, namely the exponential growth model of bacteria including the lag-time, a cardinal growth model and a Log-linear model of thermal deactivation of bacteria. RESULTS: The results of the actual simulation indicate that the contamination of milk at the farm is a rare event (P=0.0036), but the mixing of milk at the cheese factory leads to a higher probability of contamination of cheese milk (P=0.07). Elevated bacterial concentrations are mainly due to cases of mastitis involving Listeria monocytogenes. The decline in bacterial counts during cheese manufacture depends on the curing temperature (52-54 degrees C) and varies between 1.5 and 3.2 Log cfu/ml. Freshly manufactured Emmental-cheese made from contaminated raw milk is expected to have only 4.6 cfu of heat injured Listeria monocytogenes /kg cheese mass in the press. CONCLUSION: Depending on listeria evolution, from the press to the product consumption, consumer exposure has been evaluated and might result in 1 to 10 Listeria monocytogenes per portion of cheese. The bacterial presence could be due to recontamination during packaging, distribution and cheese preparation by the consumer. Based on the presented data and estimations, it is concluded that the consumption of traditionally/artisanal manufactured Swiss Emmental hard cheese presents an extremely low, but existent risk, especially for people with a deficient or diminished immune system.

Animals↗
PubMed2004

Characterization of particles in cream cheese.

Cream cheese is used as a spread and as an ingredient in many food applications. A gritty or grainy mouthfeel is an undesirable textural defect that occurs in cream cheese. However, the factors that cause the textural defect are not well understood. The objectives of this study were to isolate and characterize particles from cream cheese and to study the effect of particles on cheese texture. Particles were isolated by washing cream cheese with water first at 25 degrees C and then at 50 degrees C repeatedly 4 to 5 times. The size of these particles was determined using a particle size analyzer. The particles as well as the original cheeses were analyzed for moisture, fat, protein, ash, and lactose. The particle size ranged of 0.04 to 850 microm. It was found that isolated particles were significantly higher in protein content as compared with the whole cheese. To study the effect on the cheese texture, particles were added at 5, 15, and 25% (wt/wt) levels to smooth cream cheese, and a sensory ranking test was done on the samples. Isolated particles were further separated into 2 size classes of 2.5 to 150 microm and > or =150 microm. These particles were then mixed with smooth cream cheese at 16 and 29% (wt/wt), and a sensory test was conducted on these samples. Smooth cream cheese with only 5% (wt/wt) added particles was perceived as significantly grittier than the control sample. This experiment also revealed that the perceived grittiness increased with increase in amount and size of particles.

Caseins↗
PubMed2004

Adjunct starter properties affect characteristic features of Swiss-type cheeses.

A large number of microorganisms, both starter microorganisms and non-starter lactic acid bacteria originating from the base milk, or from various contamination sources during cheese manufacture, is associated with cheese ripening and the formation of flavour, texture and aroma. Under controlled conditions, Emmental and Bergkäse, a Gruyère-type cheese variety, were produced from pasteurised milk with standard starters and defined strains of facultatively heterofermentative lactobacilli (FHL), and partly with addition of a defined mixture of enterococci. Lactobacillus casei subsp. casei and L. rhamnosus (two strains each) were selected with respect to their potential for the utilisation of citric acid and ribose as sole energy source. The FHL developed up to 10(8) cfu/g within the first weeks of ripening, and viable counts in mature cheeses were 10(7) cfu/g, independent of the cheese variety. Bergkäse made with addition of L. rhamnosus strains showed a more pronounced proteolysis, resulting in reduced firmness and elasticity values of the cheese body, and FHL strains able to utilise citric acid improved the appearance of the cheeses by increasing the number of small eyes to the desired level. In Emmental cheese, the citric acid (+) strains reduced the intensity of propionic acid formation as the FHL apparently competed with the propionibacteria, and enterococci disappeared completely during maturation. Although further work is needed the study shows that, depending on the cheese variety, particular properties of FHL adjunct starters significantly affect important quality attributes of the resulting cheeses.

Cheese↗
PubMed2006

Artisanal and experimental Pecorino Siciliano cheese: microbial dynamics during manufacture assessed by culturing and PCR-DGGE analyses.

Traditional artisanal Pecorino Siciliano (PS) cheeses, and two experimental PS cheeses were manufactured using either raw or pasteurised ewes' milk with the addition of starter cultures. The bacterial diversity and dynamics of the different cheese types were evaluated both by culturing and characterisation of isolates, and a culture-independent approach based on the 16S ribosomal RNA (rRNA) gene. Following cultivation, artisanal and experimental cheese types showed similar microbial counts, and isolates belonging to Lactococcus lactis, Streptococcus thermophilus, Enterococcus faecalis and Leuconostoc mesenteroides were identified by phenotypic characterisation and comparison of the restriction fragment length polymorphism (RFLP) of the 16S rRNA gene to that of reference species. The culture-independent fingerprinting technique PCR and denaturing gradient gel electrophoresis (DGGE) of V6 to V8 regions of the 16S rRNA gene of samples taken during artisanal PS cheese manufacture, from raw milk to the ripened cheese, indicated relevant shifts in the microbial community structure. The dominance of Streptococcus bovis and Lactococcus lactis species in the traditional artisanal PS was revealed by 16S rRNA gene sequencing. Comparison of DGGE profiles of samples from milk to ripened cheese, derived from artisanal procedure and the two experimental PS cheeses during production showed similar trends with the presence of intense bands in common. Nevertheless, the profiles of several artisanal cheeses from different farms appeared more diverse, and these additional species are probably responsible for the generally superior flavour and aroma development of traditional PS cheese.

Animals↗
PubMed2000

Effects of mixed starter composition on nisin Z production by lactococcus lactis subsp. lactis biovar. diacetylactis UL 719 during production and ripening of Gouda cheese.

A starter culture system that produced both acid and nisin at acceptable rates in milk for manufacture of Gouda cheese was developed using nisin Z-producing L. lactis subsp. lactis biovar. diacetylactis UL 719 (UL 719) and a commercial Flora Danica (FD) starter culture. Different compositions of mixed cultures (0, 0.2, 0.4, 0.6 or 0.8% UL 719 with 1.4% FD) were tested for acidification and nisin Z production in milk after 12 h incubation at 30 degrees C. The 0.6/1.4% combination, selected as the optimal mixture of starter cultures, acidified milk to a suitable pH and produced nisin Z at a high concentration of 512 IU/ml. With this optimal combination, FD numbers of citrate-fermenting and non-fermenting bacteria did not change compared with the control (1.4% FD). However, with 0.8% of L. lactis strain UL 719 and 1.4% of the FD starter culture, the numbers of citrate-fermenting and non-fermenting bacteria in fermented milk decreased compared with those obtained when milk was inoculated with 0.2, 0.4 or 0.6% of UL 719 added to 1.4% FD or control cultures (1.4% FD). Mixed starter culture ratios 0.6/1.4%, 0.4/1.4% and 0.5/1.4% (UL 719/FD) were used to manufacture nisin Z containing Gouda cheese which was ripened up to 45 weeks. The composition of control cheeses made with 1.4% FD, and nisin Z-containing Gouda cheeses were similar with respect to percent moisture, fat, salt and protein. During the ripening period, the cell counts observed were approximately two logs higher in cheese made with the 0.6/1.4% mixed starter culture than in control cheese. In experimental cheese produced with 0.6/1.4% (UL 719/FD) mixed starter culture, nisin activity increased from 256 IU/g at the end of manufacture to a maximum of 512 IU/g after 6 weeks of ripening; the levels then decreased to 128 and 32 IU/g after 27 and 45 weeks of ripening, respectively. In contrast, nisin Z was not detected in experimental cheeses made with 0.4/1.4% or 0.5/1.4% (UL 719/FD) mixed starters. Using an affinity purified anti-nisin polyclonal antibody, anti-rabbit gold-conjugate and transmission electron microscopy, nisin Z was found to be localized in the cheese matrix, in fat globules, in the casein phase and concentrated at the fat-casein interface. After 27 weeks of ripening, nisin Z was detected preferentially in the fat globules of the experimental cheese.

Cheese↗
PubMed2003

Yeasts as adjunct starters in matured Cheddar cheese.

Debaryomyces hansenii and Yarrowia lipolytica are typical foodborne yeast species frequently associated with dairy products and capable of predominating the yeast composition in such systems. The two species fulfil a number of criteria to be regarded as co-starters for cheesemaking. They are known for their proteolytic and lipolytic activity as well as their compatibility and stimulating action with the lactic acid starter cultures when co-inoculated. Recent studies indicated that yeasts could be included as part of starter cultures for the manufacturing of cheese, enhancing flavour development during the maturation. The potential of D. hansenii and Y. lipolytica as agents for accelerated ripening of matured Cheddar cheese has been evaluated during four cheese treatments. The interaction between the two yeast species and the lactic acid bacteria was surveyed incorporating (i) D. hansenii, (ii) Y. lipolytica, (iii) both species as adjuncts to the starter culture and (iv) a control cheese without any additions for the production of matured Cheddar cheese. The physical and chemical properties of the cheeses were monitored in order to evaluate the contribution of the yeasts to cheese maturation. The yeasts grew in association with the lactic acid bacteria without any inhibition. The yeasts species when individually added contributed to the development of bitter flavours despite accelerated development of strong Cheddar flavours. When both species were incorporated as part of the starter culture, the cheese, however, had a good strong flavour after a reduced ripening period. The cheese retained this good flavour and aroma after 9 months of production. The simultaneous application of D. hansenii and Y. lipolytica as part of the starter culture for the production of matured Cheddar cheese is proposed.

Cheese↗