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At least 19 recordsLinked to original sources

PubMed1990

[Effect of a differentiated additive KNO3 on the quality of Zuławski cheese. I. Nitrate changes in maturing Zuławski cheese].

18 gyle of cheese in three experimental variants were produced: O variant--control product without additive KNO3; 1 variant--with 0.01% of additive KNO3; 2 variant--with 0.02% of additive KNO3. It was found that raw and pasteurized milk was not an essential source of nitrates. During the summer and autumn cycles of production it was noted respectively: 0.0-0.8 mg NO3-/kg and 0.0-7.4 mg NO3-/kg. Content of NO3- ions in cheese starter approximated their content in raw milk. However, content of nitrates in milk after preparing depended mostly on the quantity of added saltpeter. The cheese made without saltpeter was characterized by low level of nitrates, not exceeding 4.2 mg NO3-/kg, and by vestigial presence nitrites. Whereas the cheese made with additive KNO3 included to 40 mg NO3-/kg for 0.01% of additive KNO3 and to 80 mg NO3-/kg for 0.02% of additive KNO3. It was found that the most intense reduction of nitrates in cheese (to 75%) occurred between the phase of pressing and up to the first two weeks of its ripening. After four weeks' ripening process the level of nitrates in cheese became stabilized independently of the quantity of additive KNO3. After six weeks' ripening process, that is when the cheese is sent into consumption, the level of nitrates and nitrites was quite low and did not exceed 3.0 mg NO3-/kg and 1.2 mg NO2-/kg. Manufactured cheese met the requirements of FIL/IDF while taken into consideration the content of nitrates and nitrites.

Cheese↗

PubMedDate not supplied

Spectrometric and liquid chromatographic determination of natamycin in cheese and cheese rind.

Methods for determining natamycin content of cheese rind and cheese are presented. Cheese and rind samples are extracted with methanol and the fat precipitated by cooling the sample solution in methanol-water at -15 to -20 degrees C for ca 1 h. Natamycin levels are measured by UV spectrometric detection at absorbance minimum 311 nm, maximum 317 nm, and at exactly 329 nm, or by LC separation over Lichrosorb RP-8 column with detection at 303 nm. For measuring low levels, a concentration step is provided. The method is applicable to natamycin in cheese rind and in the interior of the cheese. Detection limit is 0.5 mg/kg. The method is suitable for controlling a maximum tolerance of natamycin on the cheese rind, at a level of 1 mg/dm2, and for detecting migration of natamycin into the cheese.

Cheese↗

PubMed1988

Effects of cheese, breadcrumbs, and a breadcrumb and cheese mixture on microhardness of bovine dental enamel in intraoral experiments.

In previous telemetric and animal experiments, cheese has been shown to be a food of low acidogenic and cariogenic potential. In vivo intraoral tests were carried out to confirm the low cariogenic potential of this substrate in humans and to explore the enamel-softening effects of toasted breadcrumbs and those of a mixture of breadcrumbs and cheese. The results confirmed the cariostatic nature of cheese and established a considerable enamel-softening effect of toasted breadcrumbs. A mixture of breadcrumbs and cheese failed to show a statistically significant difference to breadcrumbs despite a substantially lower mean value for the breadcrumbs and cheese mixture.

Adult↗

PubMedDate not supplied

Determination of natamycin in cheese and cheese rind: interlaboratory collaborative study.

A collaborative test on the determination of natamycin in cheese and cheese rind was conducted. Participants were from 37 laboratories in 13 countries. Eight samples, consisting of 4 duplicates, were investigated by a spectrometric method and a liquid chromatographic (LC) method. The spectrometric method gave good results (coefficient of variation [CV] = 12%) and the LC method with ultraviolet detection gave reasonable results (CV = 25%) for levels down to 15 mg/kg (0.9 mg/dm2). For very low levels, a preconcentration step is necessary, but even then quantitation is poor (CV = 35-37%) for both methods at 1.7 mg/kg, although the presence of natamycin can be detected qualitatively. For a level of 0.3 mg/kg, quantitation is poor (CV = 39%) for the LC method and impossible (CV = 60%) for the spectrometric method.

Cheese↗

PubMedDate not supplied

[Antigenic analysis of cheese mites with view to a study of cheese-makers' illness (author's transl)].

"Somatic" and "metabolic" antigens prepared from A. farinae and T. casei mites in Auvergne cheese were used for experimental immunisation: the hyper-immune serums obtained permitted 11 to 21 precipitant systems to be distinguished. An enzymatic activity could be identified on certain arcs. Research into antigenic communities showed the existence of 1 to 3 arcs common to the mite antigens, but none with the antigens obtained from the Penicillium cyclopium and Mucor fuscus moulds accompanying the mites. The results obtained thus facilitate an epidemiological investigation among the cheesemakers.

Antigens↗

PubMed1989

Behavior of Listeria monocytogenes during manufacture and ripening of brick cheese.

Brick cheese was made by the washed-curd procedure from pasteurized whole milk inoculated to contain ca. 1 x 10(2) to 1 x 10(3) Listeria monocytogenes [strain Scott A, Ohio, V7, or California]/ml. Cheeses were ripened (15 degrees C/95% relative humidity) with a surface smear for 2, 3, or 4 wk to simulate production of mild, aged, or "Limburger-like" brick cheese, respectively, and then stored an additional 20 to 22 wk at 10 degrees C. Populations of strains Scott A, Ohio, V7, and California increased 1.89, 1.72, .83, and .86 orders of magnitude, respectively, following completion of brining ca. 32 h after the start of cheese making. All four L. monocytogenes strains leached from cheese into brine during 24 h and survived in brine at 10 degrees C at least 5 d after removal of cheese. Strains Scott A and Ohio grew rapidly during the initial 2 wk of smear development and attained maximum populations of ca. 6.6 and 6.2, 7.0 and 6.9, and 5.6 and 5.1 log10/g in 4-wk-old slice (pH 6.0 to 6.5), surface (pH 6.5 to 6.9), and interior (pH 5.6 to 6.2) samples of cheese, respectively. Numbers of strains Scott A and Ohio generally decreased 1- to 7-fold during 20 to 22 wk at 10 degrees C. Strains V7 and California failed to grow appreciably in any cheese during or after smear development, despite pH of 6.8 to 7.4 in fully ripened cheese; the strains were never isolated from 2- and 3-wk-old cheese and with direct plating were detected sporadically at levels generally less than or equal to 4.0 log10/g in cheese aged greater than or equal to 4 wk. Cold enrichment of slice, surface, and interior samples of cheeses aged greater than or equal to 4 wk generally yielded positive results for L. monocytogenes; strains V7 and California were detected in all cheeses after 20 to 22 wk at 10 degrees C. At 10 ppm, methyl sulfide, dimethyl disulfide, or methyl trisulfide (compounds commonly produced during ripening of brick and Limburger cheese) failed to inhibit appreciably growth of L. monocytogenes.

Cheese↗

PubMed1990

Glycolysis and related reactions during cheese manufacture and ripening.

Fermentation of lactose to lactic acid by lactic acid bacteria is an essential primary reaction in the manufacture of all cheese varieties. The reduced pH of cheese curd, which reaches 4.5 to 5.2, depending on the variety, affects at least the following characteristics of curd and cheese: syneresis (and hence cheese composition), retention of calcium (which affects cheese texture), retention and activity of coagulant (which influences the extent and type of proteolysis during ripening), the growth of contaminating bacteria. Most (98%) of the lactose in milk is removed in the whey during cheesemaking, either as lactose or lactic acid. The residual lactose in cheese curd is metabolized during the early stages of ripening. During ripening lactic acid is also altered, mainly through the action of nonstarter bacteria. The principal changes are (1) conversion of L-lactate to D-lactate such that a racemic mixture exists in most cheeses at the end of ripening; (2) in Swiss-type cheeses, L-lactate is metabolized to propionate, acetate, and CO2, which are responsible for eye formation and contribute to typical flavor; (3) in surface mold, and probably in surface bacterially ripened cheese, lactate is metabolized to CO2 and H2O, which contributes to the increase in pH characteristic of such cheeses and that is responsible for textural changes, (4) in Cheddar and Dutch-type cheeses, some lactate may be oxidized to acetate by Pediococci. Cheese contains a low level of citrate, metabolism of which by Streptococcus diacetylactis leads to the production of diacetyl, which contributes to the flavor and is responsible for the limited eye formation characteristic of such cheeses.

Animals↗

PubMed1988

Experimental aflatoxin production in Manchego-type cheese.

Manchego-type cheese, a typical Spanish cheese, was inoculated in various ways with an aflatoxigenic organism, Aspergillus parasiticus NRRL 2999, to study the production of aflatoxin. When the original milk was contaminated with a spore suspension, aflatoxin was not detected in paraffin-covered cheeses although it was present in the top layer of non-paraffin-covered cheeses after ripening at 15 degrees C for 60 d. When the cheese surface was inoculated, no aflatoxins were detected in paraffin-covered cheeses after ripening for 60 d although they were found when the cheeses were ripened for 30 d. In non-paraffin-covered cheeses aflatoxins were detected only in the top layer and in the second 10 mm layer when cheeses were incubated after the normal ripening at 28 degrees C for 30 d. When the centre of the cheese was inoculated, no aflatoxins were detected although Aspergillus grew slightly along the inoculation area. When cheese portions were inoculated, fungal growth was evident after incubation at 28 degrees and 15 degrees C for 6 d but there was no growth at 10 degrees C after 50 d. At 28 degrees C aflatoxins were detected at a concentration of 132 micrograms/g after 13 d, the highest level obtained. In cheese paste at 28 degrees and 15 degrees C, growth was intense, but the level of aflatoxins detected was lower than in cheese portions. At 10 degrees C the growth was heavy, but aflatoxins were not detected.

Aflatoxins↗

PubMed2026

Genomic diversity and thermal niches of Aspergillus molds disrupting rind formation of surface-ripened cheeses.

Filamentous fungi play important roles in the development of surface-ripened cheese microbial communities and contribute to the aesthetics and flavors of these products. Much is known about the diversity and ecology of desirable cheese fungi, but our understanding of the natural history of cheese spoilage molds is limited. The goal of this work was to characterize the genomic diversity of Aspergillus species contaminating artisan cheeses and to identify how the abiotic environment of cheese (the substrate itself and temperature) may constrain the growth of Aspergillus. Comparative genomics identified two main species of Aspergillus, A. westerdijkiae and A. ostianus, as the spoilage molds across three different facilities in the Northeastern United States that experienced contamination events. Multiple genomic types of A. westerdijkiae were found across the different cheese production facilities, indicating that these contamination events are not caused by a single clonal strain. All A. westerdijkiae isolates produced ochratoxin A, but concentrations varied greatly across strains. RNA-sequencing of A. westerdijkiae on nutrient-rich lab media (malt extract agar) versus cheese curd agar identified a suite of pathways enriched in expression on cheese, including degradation of amino and fatty acids. Experiments measuring growth over a range of temperatures identified that spoilage Aspergillus species have a higher optimal growth temperature compared to desirable fungal species in cheese rinds and are outcompeted by Penicillium species at temperatures lower than 15°C. Global fungal metabarcoding databases suggest that A. westerdijkiae is not normally found in natural habitats of the Northeastern United States, and it may be introduced to this region.IMPORTANCEOver the past decade, disruptive contamination events of Aspergillus spoilage molds have occurred at cheese production facilities in Massachusetts, Connecticut, and Vermont in the United States, causing aesthetic, flavor, and potential safety issues. Our work highlights independent introductions of different strains of A. westerdijkiae into multiple cheese facilities and suggests that temperature could be used to control the abundance of Aspergillus spoilage molds. Based on our analysis of the global distribution of A. westerdijkiae, it is not invading cheese facilities from local fungal populations and may be a contaminant in materials used for cheese production.

Aspergillus↗

PubMed1992

New type of Domiati cheese of potential benefit to people with high blood cholesterol.

Part of the milk used for manufacturing Domiati cheese was replaced by buttermilk at rates of 0, 20, 30, 40, 50 and 60%. The fat and SNF contents were standardized at 5 and 10% respectively. The hypocholesterolaemic effect of buttermilk when incorporated into cheese was tested with rats by including cheese manufactured with and without buttermilk mixed in their diet at a rate of 30% for a period of 60 d. When the diet containing Domiati cheese free from buttermilk (control cheese) was given to rats, there were highly significant increases in serum and liver cholesterol. However, when part of the milk used in manufacturing Domiati cheese was replaced by buttermilk the increases in serum and liver cholesterol concentrations were reduced. These reductions were proportional to the proportion of buttermilk incorporated in the milk used to manufacture the cheese. When 50% of the milk used for Domiati cheese was replaced by buttermilk the hypercholesterolaemic effect of Domiati cheese was nullified and the serum and liver cholesterol concentrations were restored to their normal values. The effect of replacing 50% of the milk used in the manufacture of Domiati cheese by buttermilk on the quality of the cheese was tested periodically during the ripening period. The buttermilk improved the flavour of the cheese whilst only slightly affecting its ripening.

Animals↗

PubMedDate not supplied

Evaluation of APHA and AOAC methods for phosphatase in cheese.

Varieties of market cheese were analyzed for alkaline phosphatase by the modified rapid colorimetric method of the American Public Health Association (APHA) and the official AOAC method, 16.304-16.306. In the APHA method, 5 g cheese (pH less than 7.0) is macerated with 2 mL 1:1 carbonate buffer, or 2 mL water (for cheese with pH greater than 7.0). Addition of 0.1 mL magnesium acetate (1 mg magnesium) to test portions of cheese extracts yielded reproducible and quantitative recovery of added phosphatase. In the AOAC method, macerating 0.5 g cheese with 1 mL borate buffer before adding milk phosphatase improved recovery among cheeses. Addition of magnesium ion increased phosphatase activity in some cheeses. Phosphatases in blue mold-ripened and Swiss cheeses were inactivated by heat faster than was milk phosphatase, yet milk phosphatase added to various soft cheeses was completely inactivated at 60 degrees C for 10 min. The lability of phosphatase was due to the heat-denaturing effect of NaCl present in finished cheeses. Some Mexican style soft cheeses contained both heat-labile and heat-stable phosphatases. These data suggest that the phosphatase test to differentiate milk and microbial phosphatases on the basis of repasteurization and analysis of cheese is no longer valid.

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↗

PubMed1990

Effects of processed cheese on human plaque pH and demineralization and remineralization.

This two-part study was undertaken to examine the effects of processed cheese on human plaque pH and de- and remineralization of enamel and root lesions in a human in situ caries model system. In the first part of the study the selected processed cheese (Kraft American Singles Processed Cheese Food) was eaten alone and followed by a 10% sucrose rinse after the acidogenicity of the plaque was demonstrated. A 10% sucrose rinse alone resulted in a mean minimum pH of 4.26. The cheese alone showed a mean minimum pF of 6.32 and cheese followed by sucrose resulted in a mean minimum pH of 6.48. The plaque pH of cheese eaten alone stayed at pH above 5.7 (the "safe for teeth" level). Cheese consumption also prevented the acid challenge when followed by sucrose. The second part of the study utilized the thin-sections of artificially created caries-like lesions on enamel and root, and sound root sections. One-month periods were used in a cross-over design to examine the effect of eating the cheese q.i.d. Polarized light microscopy was used to determine changes in the size of lesion areas. The addition of the processed cheese to the diet resulted in statistically significant reductions in enamel lesion size as well as a reduction in progression of root lesions. Lesions created on the sound root surfaces were approximately one-third the size of those created during the control period. This study indicates that processed cheese is hypoacidogenic, anti-acidogenic, and prevents demineralization as well as enhances remineralization.

Adult↗

PubMed1990

Factors controlling histamine production in Swiss cheese inoculated with Lactobacillus buchneri.

Swiss cheese was made from raw milk inoculated with various concentrations of a histamine-producing strain of Lactobacillus buchneri. Histamine production in these cheeses was proportional to the initial number of L. buchneri present in the raw milk. The highest inoculum level tested was 10(5) L. buchneri/ml. This cheese contained 80 mg of histamine/100 g of cheese after 90 d of storage. Only 15 mg of histamine/100 g of cheese were detected after 90 d at the lowest inoculum level, 10(2) L. buchneri/ml. No histamine was detected in any of the Swiss cheese samples until after the brining stage. Perceptible growth of L. buchneri also did not occur until after the warm room treatment. Therefore, control of histamine formation in Swiss cheese requires control of the number of histamine-producing bacteria in the raw milk. A 5.5% NaCl concentration in DeMan, Rogosa, Sharpe (MRS) broth inhibited the production of histamine by L. buchneri, but the concentrations of NaCl typically found in Swiss cheese were not inhibitory. The histamine-producing isolate of L. buchneri survived heating at 49 to 80 degrees C for 10 min, suggesting that this organism would easily survive the normal heating process applied to raw milk used prior to making Swiss cheese.

Animals↗

PubMed1991

[The use of appropriate technologies to improve the sanitary quality and the yield of goat cheeses in little farms].

The purpose of this study was to increase the microbiological quality and yields of goat cheese prepared at farm level. For this purpose, appropriate technologies for the cheese-making process were designed, using a curd tank heated by gas, and cheese knives adjusted to the tank dimensions. Moreover, a low-cost table for whey draining and PVC moulds, were designed. Variables assayed were milk pasteurization, utilization of lactic acid starter by direct application, substitution of the kid rennet by commercial calf rennet, and cheese maturation for a one-month period. The control sample was goat cheese traditionally made by the small farmers. Processing and variables were evaluated by proximate chemical analysis, microbiological counts of aerobic mesophilic bacteria, total and fecal coliforms, and S. aureus; as well as by sensory evaluation of quality and acceptability. It was found that the cutting of curd with cheese knives significantly decreased solid losses in the whey. The addition of the starter and then the cheese maturation, as well as the use of the equipment previously described, increased the microbiological quality of cheese to standard sanitary regulation. Although pasteurization was the most effective treatment in decreasing bacteria contamination, this thermal treatment was difficult to be done under arid zones conditions. Commercial calf rennet did not differ significantly from kid rennet in the characteristics analyzed in this assay. Variables studied did not affect the normal sensory quality of goat cheese.

Animals↗

PubMed1990

The occurrence of Listeria monocytogenes in cheese from a manufacturer associated with a case of listeriosis.

A case of listeriosis was associated with the consumption of a soft cheese produced in England. Goats cheese and other products from the same food manufacturer were examined for the presence of Listeria over the following 11 months. Listeria monocytogenes was isolated from 16 of 25 cheese samples on retail sale, 12 of 24 cheese samples obtained directly from the factory, and from shelving within the plant. Phage-typing of 68 isolates of L. monocytogenes from cheese samples and the factory showed that 66 (97%) were indistinguishable from the strain isolated from the patient's cerebrospinal fluid and stool. L. monocytogenes was not isolated from seven goats milk or two yoghurt samples. Listeria innocua was isolated from 10 cheese samples, two of which contained no other species of Listeria. Levels of L. monocytogenes shortly after production were low (less than 10/g), but were higher (10(5)-10(7) cfu/g) in six of the 16 cheese samples obtained from retail outlets. Multiplication of L. monocytogenes was demonstrated in cheeses contaminated at the factory and held at 4 degrees C in the laboratory.

Adult↗

PubMed1988

Methods for improved recovery of Listeria monocytogenes from cheese.

Method of homogenization (Waring blender versus stomacher), type of diluent (tryptose broth [TB] versus aqueous 2% trisodium citrate), and temperature of diluent (20 versus 40 degrees C) were compared for recovery of Listeria monocytogenes from freshly made and ripened Colby cheese. By using direct plating on McBride listeria agar, significantly higher numbers of L. monocytogenes were recovered when cheese samples were (i) homogenized for 2 min with the blender rather than the stomacher (P less than 0.01), (ii) diluted in trisodium citrate rather than TB (P less than 0.01), and (iii) diluted in diluents at 40 rather than 20 degrees C (P less than 0.05). Based on these results, a new diluent/enrichment medium was developed by adding 2% trisodium citrate to TB (TBC). Despite superior results with the blender, biosafety concerns led to use of the stomacher for homogenization of cheese samples; hence, the stomaching time was increased to 3 min. Results obtained by direct plating indicated that recovery of L. monocytogenes from Colby cheese and from curd samples taken during manufacture of brick cheese increased when samples were diluted 1:10 in TBC at 45 degrees C and stomached for 3 min, as compared with similarly treated samples diluted in TB at 25 degrees C. A similar comparison of both diluents for recovery of L. monocytogenes from cold-pack cheese food yielded bacterial counts which were not significantly different. Recovery of L. monocytogenes from cold-enriched (at 4 degrees C for up to 8 weeks) samples of Colby cheese and cold-pack cheese food was generally similar for samples homogenized in TBC or TB.

Animals↗

PubMed1989

Effect of eating cheese on Ca and P concentrations of whole mouth saliva and plaque.

A study was undertaken to examine the release of calcium and phosphate from cheese during mastication. Unstimulated saliva was collected for baseline analysis in the initial study followed by saliva collection after chewing different cheeses with and without biscuits. In the second study, volunteers who had abstained from tooth cleaning for 24 h had plaque samples taken from two quadrants, they then chewed cheese in their own personal eating manner, and a second sample of plaque was taken within 5 min. The results showed that the calcium ion concentration of the oral fluids rose from a mean of 30 micrograms/ml to between 200 and 540 micrograms/ml, depending on the type of cheese, but the phosphate concentration fell below baseline. The release of both ions tended to be less when the cheese was eaten with a biscuit. In the second study a highly significant rise in plaque calcium concentration was shown after eating cheese, but no consistent change in phosphate level was found. Acidic soft drinks, following eating, tended to reduce the plaque calcium levels, but no consistent change was found if tea or coffee was taken following the cheese consumption. It is suggested, from these findings, that cheese eaten alone at the very end of a meal raises plaque calcium and might be effective in reducing dental caries.

Beverages↗