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At least 145 records · Page 8Linked to original sources
PubMed2006

Nonstarter lactic acid bacteria biofilms and calcium lactate crystals in Cheddar cheese.

A sanitized cheese plant was swabbed for the presence of nonstarter lactic acid bacteria (NSLAB) biofilms. Swabs were analyzed to determine the sources and microorganisms responsible for contamination. In pilot plant experiments, cheese vats filled with standard cheese milk (lactose:protein = 1.47) and ultrafiltered cheese milk (lactose:protein = 1.23) were inoculated with Lactococcus lactis ssp. cremoris starter culture (8 log cfu/mL) with or without Lactobacillus curvatus or Pediococci acidilactici as adjunct cultures (2 log cfu/mL). Cheddar cheeses were aged at 7.2 or 10 degrees C for 168 d. The raw milk silo, ultrafiltration unit, cheddaring belt, and cheese tower had NSLAB biofilms ranging from 2 to 4 log cfu/100 cm2. The population of Lb. curvatus reached 8 log cfu/g, whereas P. acidilactici reached 7 log cfu/g of experimental Cheddar cheese in 14 d. Higher NSLAB counts were observed in the first 14 d of aging in cheese stored at 10 degrees C compared with that stored at 7.2 degrees C. However, microbial counts decreased more quickly in Cheddar cheeses aged at 10 degrees C compared with 7.2 degrees C after 28 d. In cheeses without specific adjunct cultures (Lb. curvatus or P. acidilactici), calcium lactate crystals were not observed within 168 d. However, crystals were observed after only 56 d in cheeses containing Lb. curvatus, which also had increased concentration of D(-)-lactic acid compared with control cheeses. Our research shows that low levels of contamination with certain NSLAB can result in calcium lactate crystals, regardless of lactose:protein ratio.

Animals↗
PubMed2006

Enhanced nutty flavor formation in cheddar cheese made with a malty Lactococcus lactis adjunct culture.

Nutty flavor in Cheddar cheese is desirable, and recent research demonstrated that 2- and 3-methyl butanal and 2-methyl propanal were primary sources of nutty flavors in Cheddar. Because malty strains of Lac-tococcus lactis (formerly Streptococcus lactis var. malti-genes) are characterized by the efficient production of these and other Strecker aldehydes during growth, this study investigated the influence of a malty L. lactis adjunct culture on nutty flavor development in Cheddar cheese. Cheeses made with different adjunct levels (0, 10(4) cfu/mL, and 10(5) cfu/mL) were ripened at 5 or 13 degrees C and analyzed after 1 wk, 4 mo, and 8 mo by a combination of instrumental and sensory methods to characterize nutty flavor development. Cheeses ripened at 13 degrees C developed aged flavors (brothy, sulfur, and nutty flavors) more rapidly than cheeses held at 5 degrees C. Additionally, cheeses made with the adjunct culture showed more rapid and more intense nutty flavor development than control cheeses. Cheeses that had higher intensities of nutty flavors also had a higher concentration of 2/3-methyl butanal and 2-methyl propanal compared with control cheeses, which again confirmed that these compounds are a source of nutty flavor in Cheddar cheese. Results from this study provide a simple methodology for cheese manufacturers to obtain consistent nutty flavor in Cheddar cheese.

Aldehydes↗
PubMed2007

Effect of protein-to-fat ratio of milk on the composition, manufacturing efficiency, and yield of cheddar cheese.

Twenty-three Cheddar cheeses were prepared from milks with a protein content of 3.66% (wt/wt) and with different protein-to-fat ratio (PFR) in the range 0.70 to 1.15; the PFR of each milk differed by 0.02. For statistical analysis, the 23 cheeses were divided into 3 PFR groups: low (LPFR; 0.70 to 0.85), medium (MPFR; 0.88 to 1.00) and high (HPFR; 1.01 to 1.15), which were compared using ANOVA. The numbers of PFR values in the LPFR, MPFR, and HPFR groups were 9, 7, and 7, respectively. Data were also analyzed by linear regression analysis to establish potentially significant relationships among the PFR and response variables. Increasing PFR significantly increased the levels of cheese moisture, protein, Ca, and P, but significantly reduced the levels of moisture in nonfat substances, fat-in-DM, and salt-in-moisture. The percentage of milk fat recovered in the LPFR cheese was significantly lower than that in the MPFR or HPFR cheeses. In contrast, the recovery of water from milk to the LPFR cheese was significantly higher than that in the MPFR or HPFR cheeses. Increasing the PFR led to a significant decrease in the actual yield of cheese per 100 kg of milk but a significant increase occurred in the normalized yield of cheese per 100 kg of milk with reference values of fat plus protein (3.4 and 3.3%, wt/wt, respectively). The results demonstrate that alteration of the PFR of cheese milk in the range 0.70 to 1.15 has marked effects on cheese composition, component recoveries, and cheese yield.

Animals↗
PubMed2000

Potential use of presumptive enterococci and staphylococci as indicators of sanitary condition in plants making hard Italian-type cheese.

Raw milk, pasteurized milk, unripened cheese (1 day old), and partially ripened cheese (3 months) from 42 milk lots at a plant making hard Italian-type cheese were analyzed for presumptive enterococci using kanamycin esculin azide agar pour plates. Fully ripened (> or =10 months) cheeses, derived from other milk lots, were also tested. Numbers of presumptive staphylococci (Baird-Parker agar [B-P]) were determined in the partially and fully ripened cheeses. Presumptive enterococci were ubiquitous in raw milk, usually at levels of 2.1 to 3.0 log CFU/ml. Enterococci were detected in 11 (26%) of 42 pasteurized milk samples. Enterococci and staphylococci were detected in 39 (93%) and 6 (14%) of unripened cheeses and in 33 (80%) and 4 (10%) of partially ripened cheeses, respectively. Only eight and five samples of enterococci-positive unripened and partially ripened cheese, respectively, were made from pasteurized milk in which presumptive enterococci were detected. Of 42 samples of fully ripened cheese, 35 (83%) and 8 (19%), respectively, contained presumptive enterococci and staphylococci. Results suggest either that low numbers of presumptive enterococci survive pasteurization and cheese ripening or that contamination of cheese by enterococci occurs after pasteurization. Biochemical testing confirmed 63% of presumptive enterococci isolates. None of the 20 presumptive staphylococci isolates produced colonies typical of Staphylococcus aureus on B-P agar; the isolates were identified as 1 Staphylococcus epidermidis, 1 Staphylococcus xylosus, 2 Staphylococcus saprophyticus, 1 Staphylococcus warneri, 5 Kocuria spp., and 10 unidentified gram-positive, catalase-positive cocci. Three staphylococci isolates decreased in numbers by more than 3.0 log CFU/ml in 9.9 ml of skim milk heated 30 min in a 62.8 degrees C water bath. This finding suggests that most presumptive staphylococci detected may have been prepasteurization contaminants. Unless specificity of the kanamycin esculin azide and B-P media is improved, use of presumptive enterococci and staphylococci as indicators of postpasteurization sanitation in plants making hard Italian-type cheese cannot be recommended.

Animals↗
PubMed2004

High-pressure processing of Gorgonzola cheese: influence on Listeria monocytogenes inactivation and on sensory characteristics.

The presence of Listeria monocytogenes on the rind of Gorgonzola cheese is difficult to avoid. This contamination can easily occur as a consequence of handling during ripening. The aims of this study were to determine the efficiency of high-pressure processing (HPP) for inactivation of L. monocytogenes on cheese rind and to evaluate the influence of HPP treatments on sensory characteristics. Gorgonzola cheese rinds, after removal, were inoculated (about 7.0 log CFU/g) with L. monocytogenes strains previously isolated from other Gorgonzola cheeses. The inoculated cheese rinds were processed with an HPP apparatus under conditions of pressure and time ranging from 400 to 700 MPa for 1 to 15 min. Pressures higher than 600 MPa for 10 min or 700 MPa for 5 min reduced L. monocytogenes more than 99%. A reduction higher than 99.999% was achieved pressurizing cheese rinds at 700 MPa for 15 min. Lower pressure or time treatments were less effective and varied in effectiveness with the cheese sample. Changes in sensory properties possibly induced by the HPP were evaluated on four different Gorgonzola cheeses. A panel of 18 members judged the treated and untreated cheeses in a triangle test. Only one of the four pressurized cheeses was evaluated as different from the untreated sample. HPP was effective in the reduction of L. monocytogenes on Gorgonzola cheese rinds without significantly changing its sensory properties. High-pressure technology is a useful tool to improve the safety of this type of cheese.

Cheese↗
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↗
PubMed2001

Effect of enterocin CCM 4231 on Listeria monocytogenes in Saint-Paulin cheese.

The bacteriocin production by Enterococcus faecium strain in cheese milk and cheese was demonstrated. Purified enterocin CCM 4231 exhibited an anti-listerial effect during Saint-Paulin cheese manufacture. During cheese production the strain grew to a final concentration of 10.1 +/- 0.01 log CFU per mL per g in cheese. Then only a slight decrease of the cell concentration was noticed during ripening and was almost stable for 8 weeks. No significant differences in pH were observed between the experimental and reference cheeses. Bacteriocin production during cheese manufacture was detected only in milk samples and curd, reaching a level of 100 AU/mL. After addition of purified enterocin CCM 4231 (concentration 3200 AU/mL) into the experimental cheese, the initial concentration of 6.7 +/- 0.06 log CFU per mL of Listeria monocytogenes Ohio was reduced up to 1.9 +/- 0.01 log CFU per mL per g. After 6 weeks and at the end of the experiment the difference of surviving cells of L. monocytogenes Ohio in ECH was only one or 0.7 log cycle compared to the control cheese. Although enterocin CCM 4231 partially inhibited L. monocytogenes in Saint-Paulin cheese manufacture, an inhibitory effect of enterocin added was shown in 1-week cheese; however, it was not possible to detect bacteriocin activity by the agar spot test. The traditional fermentation and ripening process was not disturbed, resulting in acceptable end-products, including sensory aspects.

Bacteriocins↗
PubMed2004

Indigenous raw milk microbiota influences the bacterial development in traditional cheese from an alpine natural park.

Nostrano di Primiero is a 6-month ripened cheese produced from raw milk collected in the Paneveggio-Pale di San Martino Natural Park area in the Italian Dolomites. In summer, this cheese is made using milk collected from two different areas, Passo Rolle and Vanoi, in the Paneveggio Natural Park. During the experiment, the milk from the two areas was separately processed, and cheeses were made in the same cheese factory using the same technological process. The microbiota of raw milk and cheeses of the two areas was isolated and the dominant population was monitored by RAPD analysis and identified by 16S rRNA sequence. The milk of the Passo Rolle area was mainly composed of mesophilic strains, thermophilic Streptococcus thermophilus, and low amounts of enterococci were also found; the milk of the Vanoi area was dominated by mesophilic microbiota mostly Lactococcus lactis ssp. cremoris and ssp. lactis and Lactobacillus paracasei ssp. paracasei. The plating of the natural starter culture revealed the presence of a relevant community of thermophilic cocci and lower amounts of enterococci. The dynamic population analysis showed the importance of the natural starter culture in the first 2 days of cheese ripening in both cheeses. Moreover, the large biodiversity observed in the raw milks was also detected in the cheeses during ripening. The Vanoi cheese was dominated by Enterococcus faecium and Streptococcus macedonicus in the first two days and mesophilic 21 Lb. paracasei ssp. paracasei became the most represented population after 15 days of ripening. In the first few days, the Rolle cheese was characterized by being mainly composed of thermophilic S. macedonicus and S. thermophilus and secondarily by mesophilic cocci. During ripening, the microbiota composition changed, and at 15 days, mesophilic lactobacilli were the dominant population, but later, this was mainly composed of mesophilic cocci and lactobacilli. The taxonomical identification by 16S rRNA sequence confirmed a large biodiversity related to raw milk microbiota and only five strains of S. macedonicus, Lactobacillus plantarum, 21 Lb. paracasei ssp. paracasei, Lactobacillus fermentum and E. faecium were detected in both cheeses.

Animals↗
PubMed2005

The manufacture of miniature Cheddar-type cheeses from milks with different fat globule size distributions.

A novel 2-stage gravity separation scheme was developed for fractionation of raw, whole bovine milk into fractions enriched in small (SFG) or large (LFG) fat globules. The volume mean diameter of fat globules in SFG, LFG or control (CTRL) milk was 3.45, 4.68 and 3.58 microm, respectively. The maximum in storage modulus (index of firmness) decreased with increasing fat globule size for rennet-induced gels formed from SFG, LFG or CTRL milks. Miniature (20 g) Cheddar cheeses were manufactured using each of the 3 milks. There were no significant (P > 0.05) differences in the pH, moisture and fat in dry matter levels between cheeses made using any of the 3 milks, however, the fat content of the cheese made using SFG milk was approximately 1% lower than that of cheese made using LFG or CTRL milk in each of the 2 trials. Image analysis of confocal scanning laser micrographs of the cheeses illustrated that the star volume of fat globules in the cheeses decreased significantly (P < or = 0.05) as the size of fat globules in the milks used for cheesemaking was reduced. This indicates that it is possible to manipulate the size distribution of fat globules in Cheddar cheese by adjusting the fat globule size distribution of the milk used for cheese-making. The concentration of free fatty acids (FFA) increased in all cheeses during ripening. At 120 d of ripening, the concentration of FFA varied significantly (P < or = 0.05 and P < or = 0.001 for trials 1 and 2, respectively) with fat globule size, with cheeses made in trial 2 from LFG, SFG or CTRL milks having total FFA levels of 3391, 2820 and 2612 mg/kg cheese, respectively.

Animals↗
PubMed1995

Identification of Clostridium tyrobutyricum as the causative agent of late blowing in cheese by species-specific PCR amplification.

Butyric acid fermentation, the late-blowing defect in cheese, caused by the outgrowth of clostridial spores present in raw milk, can create considerable loss of product, especially in the production of semihard cheeses like Gouda cheese, but also in grana and Gruyère cheeses. To demonstrate the causative relationship between Clostridium tyrobutyricum and late blowing in cheese, many cheesemaking experiments were performed to provoke this defect by using spores from several strains of the major dairy-related clostridia. A method of PCR amplification of a part of the 16S rRNA gene in combination with hybridization with species-specific DNA probes was developed to allow the specific detection of clostridial sequences in DNAs extracted from cheeses. The sensitivity was increased by using nested PCR. Late blowing was provoked in experimental cheeses with 28 of the 32 C. tyrobutyricum strains tested, whereas experimental cheeses made with spores from C. beijerinckii, C. butyricum, and C. sporogenes showed no signs of butyric acid fermentation. In all experimental and commercial cheeses with obvious signs of late blowing, DNA from C. tyrobutyricum was detected; in some cheeses, signals for C. beijerinckii were also found. It was concluded that only C. tyrobutyricum strains are able to cause butyric acid fermentation in cheese.

Base Sequence↗
PubMed2001

Fate of Mycobacterium avium subsp. paratuberculosis in Swiss hard and semihard cheese manufactured from raw milk.

Raw milk was artificially contaminated with declumped cells of Mycobacterium avium subsp. paratuberculosis at a concentration of 10(4) to 10(5) CFU/ml and was used to manufacture model hard (Swiss Emmentaler) and semihard (Swiss Tisliter) cheese. Two different strains of M. avium subsp. paratuberculosis were tested, and for each strain, two model hard and semihard cheeses were produced. The survival of M. avium subsp. paratuberculosis cells was monitored over a ripening period of 120 days by plating out homogenized cheese samples onto 7H10-PANTA agar. In both the hard and the semihard cheeses, counts decreased steadily but slowly during cheese ripening. Nevertheless, viable cells could still be detected in 120-day cheese. D values were calculated at 27.8 days for hard and 45.5 days for semihard cheese. The most important factors responsible for the death of M. avium subsp. paratuberculosis in cheese were the temperatures applied during cheese manufacture and the low pH at the early stages of cheese ripening. Since the ripening period for these raw milk cheeses lasts at least 90 to 120 days, the D values found indicate that 10(3) to 10(4) cells of M. avium subsp. paratuberculosis per g will be inactivated.

Animals↗
PubMed2000

Ripening of cheddar cheese with added attenuated adjunct cultures of lactobacilli.

We made Milled curd Cheddar cheese with Lactococcus starter and an adjunct culture of Lactobacillus helveticus I or Lactobacillus casei T subjected to different attenuation treatments: freeze shocking (FS), heat shocking (HS), or spray drying (SD). Proteolysis during cheese ripening (0 to 6 mo), measured by urea-PAGE and water-soluble nitrogen, indicated only minor differences between control and most adjunct-treated cheeses. However, there were significant differences in the effect of Lactobacillus adjuncts on the level of free amino nitrogen in cheese. Cheeses made with FS or HS Lb. helveticus adjunct exhibited significantly greatest rates of free amino group formation. Lipolysis as measured by total free fatty acids was consistently highest in adjunct-treated cheeses, and FS Lb. casei-treated cheeses showed the highest rate of free fatty acid formation followed by FS Lb. helveticus treated cheeses. Mean flavor and aroma scores were significantly higher for cheeses made with Lb. helveticus strain. Freeze-shocked Lb. helveticus-treated cheeses obtained the highest flavor and aroma scores. Sensory evaluation indicated that most of the adjunct-treated cheeses promoted better texture and body quality.

Cheese↗
PubMed2001

A survey of lipolytic and glycolytic end-products in commercial Cheddar enzyme-modified cheese.

The concentrations of L- and D-lactic acid and free fatty acids, C4:0 to C18:3, were quantified in a range of commercial enzyme-modified Cheddar cheeses. Lactic acid in Cheddar enzyme-modified cheeses varied markedly depending on the manufacturer. Differences in the ratio of L- to D-lactic acid indicate that cheeses of different age were used in their manufacture or contained varying levels of nonstarter lactic acid bacteria. The level of lipolysis in enzyme-modified cheese was higher than in natural Cheddar cheese; butyrate was the predominant free fatty acid. The addition of exogenous acetate, lactate, and butyrate was also indicated in some enzyme-modified cheeses and may be used to confer a specific flavor characteristic or reduce the pH of the product. Propionate was also found in some enzyme-modified cheese products and most likely originated from Swiss-type cheese used in their manufacture. Propionate is not normally associated with natural Cheddar cheese flavor; however, it may be important in the flavor and aroma of Cheddar enzyme-modified cheese. Levels of lipolysis and glycolysis appear to highly controlled as interbatch variability was generally low. Overall, the production of enzyme-modified Cheddar cheese involves manipulation of the end-products of glycolysis (lactate, propionate, and acetate) and lipolysis to generate products for specific applications.

Acetates↗
PubMed2002

Influence of ovine milk in mixture with bovine milk on the quality of reduced fat Muenster-type cheese.

Reduced fat Muenster-type cheeses were manufactured from a mixture of bovine skim milk and ovine whole milk and from bovine milk only (control). Cheeses were evaluated at 15, 30, 60, 90, 120, and 180 d of age for numbers and type of microflora, casein hydrolysis, and amounts of free fatty acids. alpha(s1)-Casein degradation was similar for both cheeses during the aging period, but beta-casein degradation proceeded at a faster rate in the control cheese. The total amounts of free fatty acids remained constant throughout the ripening time; however, the cheeses produced with bovine/ovine milk yielded a significantly larger amount of caprylic (C8:0) and capric (C10:0) acids compared with the bovine milk cheeses. Lactobacilli increased during the aging period, while the populations of lactic acid bacteria, yeast and molds, and lipolytic organisms did not increase. Both cheeses had comparable cheese flavor intensity, but the bovine/ovine milk cheese had a greater occurrence of off flavors. The bovine/ovine milk cheeses were firmer than the bovine cheeses throughout the aging period.

Animals↗
PubMed2003

Influence of coagulant level on proteolysis and functionality of mozzarella cheeses made using direct acidification.

Nonfat (0% fat), reduced-fat (11% fat), and control (19% fat) mozzarella cheeses were made using direct acidification to test the influence of three levels (0.25X, 1X, and 4X) of coagulant concentration on proteolysis, meltability and rheological properties of cheeses during 60 d of storage at 5 degrees C. Changes in meltability, level of intact alpha(s1)-casein and beta-casein (by capillary electrophoresis), 12.5% TCA-soluble nitrogen, and complex modulus were measured. There were differences in rate of proteolysis and functional properties as a function of fat content of the cheese, but some of these differences could be attributed to differences in moisture contents of the cheeses. As fat level decreased, the percent moisture-in-nonfat-substance of the cheeses also decreased. Cheeses with the lower fat contents (and consequently the lowest moisture-in-nonfat-substance content) had slower rates of proteolysis. Fat content influenced the complex modulus of the cheese, with the biggest effect occurring when fat content was reduced from 11 to 0%. Coagulant level had only a small effect on initial modulus. Cheeses became softer during storage, and the decrease in modulus was influenced by the level of coagulant. At 0.25X, there was very little decrease in modulus after 60 d, while at 1X and 4X coagulant levels the softening of the cheese was more evident. The influence of coagulant level and fat content on cheese melting was similar to their effects on complex modulus. In general, higher fat contents promoted more melting and so did higher coagulant levels. Melting increased during storage although very little change was observed in the nonfat cheese.

Animals↗
PubMed2003

Effect of Lactobacillus helveticus and Propionibacterium freudenrichii ssp. shermanii combinations on propensity for split defect in Swiss cheese.

One of the least controlled defects in Swiss cheese is development of splits that appear during refrigerated storage after cheese is removed from the warm room. Such fissures, or cracks, in the body of the cheese can be as short as 1 cm, or long enough to span a 90-kg block. A 2 x 2 x 2 factorial experiment was used to determine the effect of different Lactobacillus helveticus/Propionibacterium freudenreichii ssp. shermanii starter culture combinations on the occurrence of split defect in Swiss cheese. Eights vats of cheese were made in summer and eight in winter. Each 90-kg block of cheese was cut into twenty-four 4-kg blocks and graded based on the presence of splits. Only small variations were found in the composition of cheeses made during the same season. There were no correlations between moisture, pH, fat, protein, calcium, lactose contents, D/L lactate ratio, or protein degradation that could be used to predict splits after 90 d of storage. However, cheese made in the summer had 2% higher moisture content and a greater prevalence of splits. There was a sixfold increase in amount of downgraded cheese between the best and worst culture combinations used during cheese manufacture. After 90-d storage, 14 to 90% of cheese had splits in the summer, and 1 to 6% in the winter. Split formation increased with time from 60 to 120 d of storage and extent of split formation was influenced by both the lactobacilli and propionibacteria cultures used.

Calcium↗
PubMed2003

The effect of application of cold natural smoke on the ripening of Cheddar cheese.

The present study was undertaken to study the effects of application of natural wood smoke on ripening of Cheddar cheese, and to determine the effects of smoking before or after ripening on cheese quality. A 20-kg block of Cheddar cheese obtained immediately after pressing was divided into six approximately 3-kg blocks and ripened at 8 degrees C for up to 270 d. One 3-kg block was taken after 1 d, 1, 3, 6, or 9 mo and smoked for 20 min, then returned to the ripening room for further ripening. Cheeses were sampled at intervals for lactobacilli counts, moisture, pH, and proteolysis. Sensory analysis was conducted on 6 and 9-mo-old cheeses by a trained sensory panel (n = 7). Results show that application of natural wood smoke did not significantly affect cheese pH or primary proteolysis during ripening. However, secondary proteolysis as assessed by the concentrations of free amino acids was generally higher in smoked cheeses than in control cheeses after 6 mo of ripening. Cheese smoked after 6 mo of ripening had better smoked flavor than that smoked after 9 mo of ripening. Cheese smoked after 3 mo of age and further ripened for 6 mo had the highest smoked flavor intensity. It is concluded that it is best to smoke cheese after ripening for at least 3 mo.

Cheese↗
PubMed2004

Influence of residual milk-clotting enzyme on alpha(s1) casein hydrolysis during ripening of Reggianito Argentino cheese.

Milk-clotting enzyme is considered largely denatured after the cooking step in hard cheeses. Nevertheless, typical hydrolysis products derived from rennet action on alpha(s1)-casein have been detected during the ripening of hard cheeses. The aim of the present work was to investigate the influence of residual milk-clotting enzyme on alpha(s1)-casein hydrolysis in Reggianito cheeses. For that purpose, we studied the influence of cooking temperature (45, 52, and 60 degrees C) on milk-clotting enzyme residual activity and alpha(s1)-casein hydrolysis during ripening. Milk-clotting enzyme residual activity in cheeses was assessed using a chromatographic method, and the hydrolysis of alpha(s1)-casein was determined by electrophoresis and high performance liquid chromatography. Milk-clotting enzyme activity was very low or undetectable in 60 degrees C- and 52 degrees C-cooked cheeses at the beginning of the ripening, but it increased afterwards, particularly in 52 degrees C-cooked cheeses. Cheese curds that were cooked at 45 degrees C had higher initial milk clotting activity, but also in this case, there was a later increase. Hydrolysis of alpha(s1)-casein was detected early in cheeses made at 45 degrees C, and later in those made at higher temperatures. The peptide alpha(s1)-I was not detected in 60 degrees C-cooked cheeses. The results suggest that residual milk-clotting enzyme can contribute to proteolysis during ripening of hard cheeses, because it probably renatures partially after the cooking step. Consequently, the production of peptides derived from alpha(s1)-casein in hard cheeses may be at least, partially due to this proteolytic agent.

Aspartic Acid Endopeptidases↗