Cheese Starter Research Articles

Contribution of starter and adjunct lactobacilli to proteolysis in Cheddar cheese during ripening

Proteolysis in Cheddar cheese made with or without adjunct lactobacilli and acidified with starter or glucono-δ-lactone (GDL) was monitored during ripening. The pH of the GDL cheeses was higher than that of the starter cheeses, resulting in lower chymosin activity in the former which was apparent in electrophoretograms of the cheeses throughout ripening. Although the coagulant appeared to be responsible for most of the water-soluble N (WSN), the starter also contributed, as shown by differences between electrophoretograms of the WSN extracts of the starter and GDL cheeses. The starter enzymes were the major contributors to the production of small peptides and free amino acids. Addition of adjunct lactobacilli to the starterfree cheeses caused a significant increase in proteolysis. This increase in proteolysis was not as apparent when the adjunct lactobacilli were added to the starter cheese, possibly due to the lack of available substrate for the wide range of enzymes supplied by both the starter lactococci and adjunct lactobacilli.

Effect of lactic starter cultures on the organic acid composition of milk and cheese during ripening—analysis by HPLC

The major function of lactic starter cultures in cheese making is to produce lactic and other organic acids from the carbohydrates present in milk. The activity of six starter cultures consisting of two Lactococcus lactis ssp. lactis, two Lactococcus lactis ssp. lactis biovar. diacetylactis and two Leuconostoc strains, was tested by monitoring the evolution of the organic acid composition of milk by a modified HPLC method. In addition, their performance as cheese starters was also tested. The HPLC method developed proved to be a precise tool to monitor the organic acid content. Thus, it can be used to follow the fermentation ability of starter cultures, providing information about the type of fermentation. The use of any of the six starters assayed is suggested for manufacturing Afuega'l Pitu cheese.

Development and characterization of lactose-positive pediococcus species for milk fermentation

Bacteriophages against Streptococcus thermophilus are a growing problem in the Italian cheese industry. One possible control method involves replacing S. thermophilus in mozzarella starter blends with lactic acid bacteria from a different genus or species. In this study, we evaluated lactose-positive pediococci for this application. Because we could not identify any commercially available pediococci with fast acid-producing ability in milk, we transformed Pediococcus pentosaceus ATCC 25744, P. pentosaceus ATCC 25745, and Pediococcus acidilactici ATCC 12697 by electroporation with pPN-1, a 35-kb Lactococcus lactis lactose plasmid. Transformants of P. pentosaceus ATCC 25745 and P. acidilactici ATCC 12697 were then used to examine lactose-positive pediococci for properties related to milk fermentation. Both transformants rapidly produced acid and efficiently retained pPN-1 in lactose broth, and neither bacterium was attacked by bacteriophages in whey collected from commercial cheese facilities. Paired starter combinations of Pediococcus spp. and Lactobacillus helveticus LH100 exhibited synergistic pH reduction in milk, and small-scale cheese trials showed that these cultures could be used to manufacture part-skim mozzarella cheese. Results demonstrate that lactose-positive pediococci have potential as replacement cocci for S. thermophilus in Italian cheese starter blends and may facilitate development of new strain rotation schemes to combat S. thermophilus bacteriophage problems in mozzarella cheese plants.

Reclassification of the Penicillium roqueforti group into three species on the basis of molecular genetic and biochemical profiles.

Penicillium roqueforti is currently divided into two varieties, one used for cheese starter cultures, P. roqueforti var. roqueforti, and one ubiquitous patulin-producing variety, P. roqueforti var. carneum. The ribosomal regions comprising the 5.8S gene and the internal transcribed spacers, ITS I and ITS II, have been analysed from 10 isolates belonging to each variety. The 10 P. roqueforti var. carneum isolates were separated into two groups of five on the basis of 12 base-pair differences in the ITS regions. One of the groups of P. roqueforti var. carneum, in the following designated P. carneum, differed from P. roqueforti var. roqueforti, here designated P. roqueforti, in just two positions, while the other group, here called P. paneum, differed from P. roqueforti in 12 positions. Random Amplified Polymorphic DNA (RAPD) analysis substantiated these findings, and a comparison of secondary metabolites produced by the three groups showed that the P. roqueforti isolates all produce Penicillium Roqueforti (PR) toxin, marcfortines and fumigaclavine A, while the P. carneum isolates produce patulin, penitrem A and mycophenolic acid, as well as unidentified metabolites. P. paneum produces secondary metabolites in five chromophore families including the known mycotoxins patulin and botryodiploidin. On the basis of these findings it is proposed that P. roqueforti is reclassified into three species named P. roqueforti, P. carneum and P. paneum.

An application in cheddar cheese manufacture for a strain of Lactococcus lactis producing a novel broad-spectrum bacteriocin, lacticin 3147.

Lactococcus lactis DPC3147, a strain isolated from an Irish kefir grain, produces a bacteriocin with a broad spectrum of inhibition. The bacteriocin produced is heat stable, particularly at a low pH, and inhibits nisin-producing (Nip+) lactococci. On the basis of the observation that the nisin structural gene (nisA) does not hybridize to DPC3147 genomic DNA, the bacteriocin produced was considered novel and designated lacticin 3147. The genetic determinants which encode lacticin 3147 are contained on a 63-kb plasmid, which was conjugally mobilized to a commercial cheese starter, L. lactis subsp. cremoris DPC4268. The resultant transconjugant, DPC4275, both produces and is immune to lacticin 3147. The ability of lacticin 3147-producing lactococci to perform as cheddar cheese starters was subsequently investigated in cheesemaking trials. Bacteriocin-producing starters (which included the transconjugant strain DPC4275) produced acid at rates similar to those of commercial strains. The level of lacticin 3147 produced in cheese remained constant over 6 months of ripening and correlated with a significant reduction in the levels of nonstarter lactic acid bacteria. Such results suggest that these starters provide a means of controlling developing microflora in ripened fermented products.

DNA Fingerprinting of Dairy Propionibacteria Strainsby Pulsed-Field Gel Electrophoresis

Restriction endonuclease patterns generated by Pulsed-Field Gel Electrophoresis (PFGE) were used to compare 96 strains of dairy propionibacteria originating from dairy products, international and industrial collections; endonucleases XbaI and SspI gave satisfactory restriction patterns. However, whereas XbaI can be used for Propionibacterium freudenreichii, SspI seems more suitable for the three other species: P. acidipropionici, P. thoenii, and P. jensenii. It is a convenient method to differentiate the dairy propionibacteria from closely related bacteria and from others usually present in dairy products. We observed a considerable restriction fragment length polymorphism among the Propionibacterium chromosomes and especially for P. freudenreichii: among 48 strains we detected 40 different patterns. This species is the most commonly encountered in the Swiss-type cheeses and is the only Propionibacterium species used as a cheese starter. Conversely, the species P. acidipropionici is not very diverse: among nine strains we observed only four different patterns, two of which were closely related. This is probably because this species is not used as a starter in cheese manufacture and consequently is poorly represented in collections. When strains come from geographical different isolates, their patterns are always different with very few common bands. The presence of numerous identical strains was due to the fact that they were present at the same time in the national collections, research laboratory collections, and in the industrial ones.

Use of high milk protein powder in the manufacture of Gouda cheese

Abstract A high milk protein powder (HMPP), used in a blend with non-fat dry milk in bulk starter for Gouda cheese making, caused no differences in composition, adjusted yield, sensory evaluation, and pH during ripening of the cheese. Supplementation of cheese milk with HMPP had noticeable effects in Gouda cheese from manufacturing to ripening. The pH decreased faster from milk renneting to pressing of curds, coagulation time was shorter, curd was firmer, and more effort was needed to cut the gel. Addition of 2% HMPP increased cheese yield by almost 2.4 kg per 100 kg of milk compared to controls, but the cheese retained more moisture, and was higher in protein and had less fat. This modified composition adversely affected the sensory attributes of the ripened product. Nevertheless, addition of 1% HMPP to cheese milk and fat standardization would ensure a Gouda cheese with good sensory characteristics as well as increased cheese yield.

Production of propionic acid from whey permeate by sequential fermentation, ultrafiltration, and cell recycling

This article deals with the production by fermentation of a mycostatic and aromatic food additive based on propionic acid. Membrane bioreactors have been used from laboratory scale up to pilot and industrial production plants. Due to the high cell densities achieved by the sequential recycling mode of operation, a mixed acids solution was rapidly produced from whey permeate. The sterile fermented broth obtained was subsequently concentrated at different levels by evaporation and spray drying according to the projected use. Concentrated Propionibacterium cells (200 g x L(-1) DW) were obtained from the process by periodic bleeds and could be used to good effect as cheese starters, silage preservatives, or probiotics. Propionic acid concentrations from 30 to 40 g x L(-1) were easily achieved with no residual lactose. The highest volumetric productivity was 1.6 g x L(-1) x h(-1) for total acid and 1.2 g x L(-1) x h(-1) for propionic acid with a specific productivity of 0.035 h(-1).

Relationship between Lactococcus lactis subsp. lactis 952, an industrial lactococcal starter culture and strains 712, ML3 and C2

Lactococcus lactis subsp. lactis 952, used as a component of a cheese starter culture, was found to be closely related to the 712/ML3/C2 group of strains. Plasmid profiles of the four isolates were very similar and factory phages isolated against strain 952 could produce plaques on all the other strains at the same titres. Treatment with mitomycin C failed to induce phage from strain 952 although homology was observed between φT712 and the chromosome of strain 952. Pulse field gel electrophoresis of the four strains revealed only minor differences in their genomic DNA. The clumping phenomenon observed during lactose transfer in strains 712 and ML3 was also evident in strain 952. The ability of strain 952 to mobilize non‐conjugative vectors such as pGB301 was also examined and analysis of pGB301 transconjugants revealed that some contained novel enlarged plasmids not present in either the donor or the recipient. Preliminary characterization of these enlarged plasmids suggested the involvement of a sex factor type element in strain 952.

Characterization of growth and enzymes produced by prt+lac+ and prt-lac-Lactococcus lactis cells

Lactococcus lactis subsp.cremoris strains KH (prt+lac+) and KHA (prt−lac−) are used as starter cultures in manufacture of ripened cheeses. The growth characteristics and the dipeptidases produced by these cells have been investigated in this study. A new semisynthetic medium was developed for growth of the cells. Growth on this medium was as good as or better than that on milk, the natural medium for cheese starters. Production of proteinases and dipeptidases by these cells was monitored. The effect of temperature on the activity and on the half-lives of dipeptidases was determined.

Conjugally Transferable Phage Resistance Activities from Lactococcus lactis DRC1

Lactococcus lactis ssp. lactis strain HID600 is a phage-resistant transconjugant produced by mating HID113 (an antibiotic-resistant variant of plasmid-free strain LM0230) with L. lactis ssp. lactis strain DRC1. Analysis of HID600 revealed that it had conjugally acquired phage resistance, bacteriocin production, proteolytic activity, and a 131-kb plasmid. The interaction of phages c2 and sk1 with HID113 and HID600 was studied. Plaque assays indicated that only about 12.5% of c2 infections of HID600 produced infective centers and that c2 infections of HID600 had a longer latent period and smaller average burst size than did infections of HID113. Less than .2% of sk1 infections of HID600 were apparently productive; no burst was detected. The resistance to phage infection involved restriction-modification and abortive infection effects. Such resistance might be useful in the construction of cheese starter strains with reduced susceptibility to phage infection, although phage variants able to infect HID600 with increased efficiency were observed.

Proteinase genes of cheese starter cultures

The proteolytic enzymes of lactococci are of eminent importance for milk fermentations. By the combined action of proteinases and peptidases milk protein is degraded to peptides and amino acids which are required for cell growth and contribute to the organoleptic properties of the foods. The importance of the proteolytic system for dairy product quality has resulted in an increased fundamental research of the enzymes and genes involved. Proteinase plasmids have been identified and plasmid stability problems offered an explanation for the apparent instability of proteolysis in certain strains of lactococci. Chromosomal integration has recently been used to stably anchor the proteinase genes in the chromosome of Lactococcus lactis. The structural proteinase genes of a number of strains have been cloned and sequenced, and some of the properties of the enzymes they specify will be discussed. The product of a second gene is necessary for the activation of the proteinase, a proteinase maturation process that is unique in the bacterial world.

Genetic characterization of partial lactose-fermenting revertants from lactose-negative mutants of lactococci

Partial lactose-positive (Lac+) revertants, designated RS0121 and RS033, were isolated from lactose-negative (Lac−) mutants of Lactococcus lactis subsp. lactis C2 and ML3, respectively. These revertants were found to coagulate 10% reconstituted skim milk, but the rate of lactose fermentation was much slower than that of their parental Lac+ strains. Such partial Lac+ revertants were also isolated from Lac− mutants of L. lactis subsp. Lactis SL712, SH4109, and SL763 and of L. lactis subsp. cremoris ML1 and SC607, showing a generalized phenomenon. The Lac+ characteristic of the revertant strains was conjugally transferred to Lac− variants. When the plasmid profiles of the Lac− variants and their partial Lac+ revertants and transconjugants were analyzed, there were no detectable differences in the plasmid bands. A strain with no plasmids, MG1363, also yielded partial Lac+ revertants, which were devoid of all plasmids. In addition, the Lac+ phenotype of one such revertant, designated RS101, was transferable to other Lac− strains by conjugation. The results indicate that the genetic information for slow lactose metabolism in such partial Lac+ revertants is mediated through chromosomal gene(s) and is under the influence of some suppressor. These observations also suggest the possibility of utilizing this method for isolating slow acid producing variants, which could be used as adjuncts with regular cheese starter cultures for accelerated cheese ripening. Key words: lactococci, lactose-negative mutants, plasmid DNA, lactose-fermenting revertants.

Characterization of Bacteriophages and Bacteria Indigenous to a Mixed-Strain Cheese Starter

To understand the types of phages and bacteria that coexist in a phage-carrying starter, we characterized isolates from milk fermented by a commercial mixed-strain culture. The bacterial population was 62% Lactococcus lactis ssp. cremoris, 19% Lactococcus lactis ssp. lactis biovar. diacetylactis, 2% Lactococcus lactis ssp. lactis, 16% Leuconostoc cremoris, and 1% unknown species. Plasmid analyses indicated 24 groups of L. lactis ssp. cremoris strains, 4 groups of L. lactis ssp. lactis biovar. diacetylactis, 1 group of L. lactis ssp. lactis, and 1 group of Leuc. cremoris. Fermentation times and sensitivity to outside phages varied between strains. Seven phages were isolated from the starter. Six attacked L. lactis ssp. cremoris strains, and one attacked L. lactis ssp. lactis biovar. diacetylactis. Three L. lactis ssp. cremoris phages crossreacted on starter hosts, and their DNA patterns were similar after restriction endonuclease digestion and agarose gel electrophoresis. Electron microscopy and DNA/DNA hybridization revealed two distinct small isometric phage types. One type attacked L. lactis ssp. cremoris and had a collar, whiskers, hexagonal tail-base structure, and 151-nm long tail. The other type attacked L. lactis ssp. lactis biovar. diacetylactis, had a tail fiber and a 215-nm long tail. Bacteria within and between plasmid groups demonstrated various degrees of resistance to these phages. Although lytic phages and sensitive hosts were both present, the mixed-strain culture functioned as a fast acid-producing starter.

Influence of Lysozyme on Selected Bacteria Associated with Gouda Cheese

The germination of Clostridium tyrobutyricum spores; the growth of vegetative cells of C. tyrobutyricum; and the growth of four cultures each of lactobacilli, coliform bacteria, and cheese starter cultures were studied in culture media containing various levels of lysozyme. Lysozyme was found to inhibit vegetative growth of both isolates (BZ15 and C611) of C. tyrobutyricum at concentrations equal to and greater than 250 units/ml. Spore germination was stimulated by lysozyme with maximum stimulation at 250 units/ml. This effect was more evident with the slower germinating strain, C611. One Lactobacillus isolate was not affected by lysozyme while the other three isolates were inhibited by 500 to 1000 units/ml of lysozyme, but were not affected by lower concentrations. The activity of the four starter cultures was not affected by lysozyme concentrations of up to 2500 units/ml. Growth of three coliform isolates was inhibited by 1000 units/ml of lysozyme, but was not significantly affected by lower concentrations of the enzyme. Growth of the fourth coliform isolate was stimulated by lysozyme at all the concentrations used in the experiments.

BOOK REVIEWS

Journal of Food BiochemistryVolume 13, Issue 6 p. 485-487 BOOK REVIEWS First published: December 1989 https://doi.org/10.1111/j.1745-4514.1989.tb00415.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Book reviewed in this article: Colloidal Systems and Interfaces. Sydney Ross and Ian D. Morrison Durum Wheat: Chemistry and Technology.G. Fabriani and C. Lintas, eds. Cheese Starters: Developments and Applications of the Lewis System.J. E. Lewis Volume13, Issue6December 1989Pages 485-487 RelatedInformation

Impedance Measurement of Changes in Activity of Lactic Cheese Starter Culture After Storage at 4°C

Impedance, titratable acidity, and change in pH were used to measure activity of lactic cheese starter culture held up to 7 d at 4°C. The impedance microbiology, as quantified by the impedance detection time method, provided an activity estimate within 37 to 53min, and the results were similar to the activity measurements using titratable acidity (3.5h) and change in pH (2.5h). The impedance detection time, titratable acidity, and pH activity tests showed that the culture activity decreased most rapidly between 2 and 5 d. The slope of the impedance curve, 15min after the impedance detection time, decreased as storage time increased with the sharpest decrease occurring during the first 3 d of storage.

Development and use of a defined strain starter system for Cheddar cheese

Out of 210 strains of Streptococcus cremoris and Streptococcus lactis screened, 35 were suitable for inclusion in multiple strain starters for Cheddar cheese. The use of various combinations of these 35 strains and bacteriophage‐insensitive mutants isolated from some of them as cheese starters over six seasons is described. All cheese graded well for body, texture and flavour, with <1% being downgraded due to starter failure. The system is now being used in all Cheddar cheese plants in Ireland producing ˜60,000 tonnes a year. The problems encountered in phage monitoring are also discussed.

Sensitivity of Commercial Cheddar Cheese Starter Isolates to Bacteriophage Associated with Wheys

Seventy-six Cheddar cheese starter cultures were collected from five cheese plants located in New York, Wisconsin, and Illinois. Several single colony isolates from each starter culture were purified and identified to species on the basis of six biochemical reactions. Thirteen of the 76 starter cultures were identified as mixture of Strepcococcus lactis and S. cremoris and 63 of the starter cultures were single species. Plasmid profiles and resistance to five phages (ML3, C2, TRM, 18-16, and C5W6) were determined for all 450 isolates. One hundred and thirty-six isolates that constituted a representative cross-section of commercial strains were selected upon their plasmid and phage-resistance profiles. These strains were used as indicators to test phage activities of 57 wheys collected from four of the five cheese plants. Wheys from different cheese plants showed varying levels of phage activity. Wheys from the plant that had the most acute phage problem completely lysed at least 25% of the 136 strains. Most of the sensitive bacterial strains of the 136 isolates were lysed by wheys from two individual plants. The percentage of strains from each plant resistant to all 57 wheys ranged from 9 to 43.

4621058 Method of preparing cheese starter media: Malireddy S Reddy assigned to Mid-America Dairymen Inc

4621058 Method of preparing cheese starter media: Malireddy S Reddy assigned to Mid-America Dairymen Inc