Use of high pressure treatment to attenuate starter bacteria for use as adjuncts for Cheddar cheese manufacture

Attenuated starter bacteria cannot produce acid during cheese manufacture, but contain enzymes that contribute to cheese ripening. The aim of this study was to investigate attenuation of starter bacteria using high pressure treatment, for use in combination with a primary starter for Cheddar cheese manufacture, and to determine the effect of such adjunct cultures on secondary proteolysis during ripening. Lactococcus lactis ssp. cremoris HP and L. lactis ssp. cremoris 303 were attenuated by pressure treatment at 200 MPa for 20 min at 20 °C. Cheddar cheese was manufactured using untreated cultures of both these starter strains, either alone or in combination with their high pressure-treated equivalents. High pressure-treated starters did not produce acid during cheese manufacture and starter counts in cheeses manufactured using high pressure-treated starter did not differ from those of the controls. Higher levels of cell lysis were apparent in cheese manufactured using high pressure-treated strains than in the controls after 26 d of ripening. Small differences were observed in the peptide profiles of cheeses, analysed by reversed-phase HPLC; cheeses manufactured using high pressure-treated starters also had slightly higher levels of amino acids than the relevant controls. Overall, addition of high pressure-treated starter bacteria as a secondary starter culture accelerated secondary proteolysis in Cheddar cheese.

Industrial relevance

Attenuated starters provide extra pool of enzymes, which can influence cheese ripening, without affecting the cheese making schedule. This paper presents an alternative method for attenuation of starter bacteria using high pressure treatment and their subsequent use to accelerate secondary proteolysis in Cheddar cheese during ripening.     

Biogenic amine content and proteolysis in Manchego cheese manufactured with Lactobacillus paracasei subsp. paracasei as adjunct and other autochthonous strains as starters

Two different autochthonous strain starter cultures, in which the acidifying starter was composed of strains of Lactococcus lactis, were used for the manufacture of pasteurised milk Manchego cheese. Proteolysis parameters, biogenic amines and sensory characteristics were evaluated and compared with those of commercial starter Manchego cheese and raw milk Manchego cheese manufactured without starter. Autochthonous starter cheeses, and especially those including Lactobacillus paracasei subsp. paracasei as adjunct, presented higher levels of proteolysis than in commercial starter cheese. The concentrations of total biogenic amines in autochthonous starter cheeses were much lower than in raw milk cheese and even lower than in commercial starter cheese. Cheese manufactured with the adjunct strain gave the best results for both flavour intensity and flavour quality, and was the most preferred by panellists. The results suggest that the culture containing Lb. paracasei subsp. paracasei as adjunct could be used for the manufacture of industrial Manchego cheese.     

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, 10⁴ cfu/mL, and 10⁵ cfu/mL) were ripened at 5 or 13°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°C developed aged flavors (brothy, sulfur, and nutty fla-vors) more rapidly than cheeses held at 5°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.     

Autolysis of selected Lactobacillus helveticus adjunct strains during Cheddar cheese ripening

Cheddar cheeses were manufactured on a pilot scale (500 L vats) with three different Lactobacillus helveticus strains, which showed varying degrees of autolysis, added as adjuncts to the starter. Autolysis of adjunct strains was monitored by reduction in cell numbers, level of intracellular enzymes released into the cheese, and by the consequent changes in the degree of proteolysis and concentration of free amino acids in the cheese. The flavour profiles of the cheeses at 6 months were also determined. Significant variation in viability of the Lb. helveticus strains, which showed a positive correlation with the indicators of autolysis, was observed. However, cheese manufactured with the most autolytic strain did not receive the highest flavour scores. The results indicate that whereas autolysis of adjunct strains is an important factor in Cheddar cheese flavour development, other factors also contribute to the overall flavour improvement observed.     

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°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°C compared with that stored at 7.2°C. However, microbial counts decreased more quickly in Cheddar cheeses aged at 10°C compared with 7.2°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.     

Application of exopolysaccharide-producing cultures in reduced-fat Cheddar cheese: composition and proteolysis

Proteolysis during ripening of reduced fat Cheddar cheeses made with different exopolysaccharide (EPS)-producing and nonproducing cultures was studied. A ropy strain of Lactococcus lactis ssp. cremoris (JFR1) and capsule-forming nonropy and moderately ropy strains of Streptococcus thermophilus were used in making reduced-fat Cheddar cheese. Commercial Cheddar starter was used in making full-fat cheese. Results showed that the actual yield of cheese made with JFR1 was higher than that of all other reduced-fat cheeses. Cheese made with JFR1 contained higher moisture, moisture in the nonfat substance, and residual coagulant activity than all other reduced-fat cheeses. Proteolysis, as determined by PAGE and the level of water-soluble nitrogen, was also higher in cheese made with JFR1 than in all other cheeses. The HPLC analysis showed a significant increase in hydrophobic peptides (causing bitterness) during storage of cheese made with JFR1. Cheese made with the capsule-forming nonropy adjunct of S. thermophilus, which contained lower moisture and moisture in the nonfat substance levels and lower chymosin activity than did cheese made with JFR1, accumulated less hydrophobic peptides. In conclusion, some EPS-producing cultures produced reduced-fat Cheddar cheese with moisture in the nonfat substance similar to that in its full-fat counterpart without the need for modifying the standard cheese-making protocol. Such cultures might accumulate hydrophobic (bitter) peptides if they do not contain the system able to hydrolyze them. For making high quality reduced-fat Cheddar cheese, EPS-producing cultures should be used in conjunction with debittering strains.     

Preliminary observations on proteolysis in Manchego cheese made with a defined-strain starter culture and adjunct starter (Lactobacillus plantarum) or a commercial starter

Different authors have demonstrated the potential of adding lactobacilli as adjunct cultures to pasteurized milk used in cheese manufacture. The aim of this work was to observe the effect of the use of a defined-strain starter culture and the addition of an adjunct culture (Lactobacillus plantarum) to cheesemilk in order to determine their effect on the ripening of Manchego cheese. Manchego cheeses were manufactured using one of the following starter culture systems: a defined starter consisting of Lactococcus lactis ssp. lactis and Leuconostoc mesenteroides ssp. dextranicum; a defined starter, as described above, and Lb. plantarum, which were isolated from a good quality Manchego cheese made from raw milk, or a commercial starter comprised of two strains of Lc. lactis. The cheeses were sampled at 15, 45, 90 and 150 d of ripening. Principal component analysis of peak heights of reversed-phase HPLC chromatograms of 70% (v/v) ethanol-insoluble and -soluble fractions distributed the samples according to the starter used in their manufacture. Quantitative differences in several peptides were evident between the three cheeses. Cheeses made with the defined-strain starters received higher scores for the flavour quality and intensity and for overall impression than the cheeses made with the commercial starter.     

Manufacture of low-fat Cheddar cheese by exopolysaccharide-producing Lactobacillus plantarum JLK0142 and its functional properties

This study aimed to evaluate the effect of exopolysaccharide (EPS)-producing Lactobacillus plantarum JLK0142 on the ripening characteristics and in vitro health-promoting benefits of low-fat Cheddar cheese. Three batches of cheese were made by employing a non-EPS–producing cheese starter (control), in combination with Lb. plantarum JLK0142 as an adjunct and the purified EPS as an ingredient. Lactobacillus plantarum JLK0142 survived well in cheese, with counts of 7.99 log cfu/g after 90 d of ripening. All experimental cheeses (with adjunct culture or EPS ingredient) had higher moisture, proteolysis, and sensory scores, and lower hardness and cohesiveness compared with the control cheese. Water-soluble extracts from the experimental cheeses outperformed that of the control in scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), and hydroxyl radicals, and inhibiting α-amylase, angiotensin-converting enzyme, and HT-29 tumor cell growth. Therefore, incorporation of the EPS-producing culture of Lb. plantarum JLK0142 is promising for improvement of low-fat cheese quality and bioactivities.     

Use of Galactose-Fermenting Streptococcus thermophilus in the Manufacture of Swiss,Mozzarella, and Short-Method Cheddar Cheese

Galactose-fermenting (galactose-positive) strains of Streptococcus thermophilus, alone and combined with galactose-positive and galactose-negative strains of Lactobacillus bulgaricus, were used as starter cultures in the manufacture of Swiss and Mozzarella cheese and were paired with Streptococcus lactis (also galactose-positive) in short-method Cheddar cheese manufacture. Experimental Swiss cheese made with the galactose-positive Streptococcus thermophilus starter alone contained a large amount of galactose (ca. 26 to 28 µmol/g of curd) 28 h after hooping compared with control Swiss (< 2 µmol/g) made with a nongalactose fermenting strain of Streptococcus thermophilus and a galactose-positive strain of Lactobacillus bulgaricus. Mozzarella and short-method Cheddar made with only galactose-positive Streptococcus thermophilus also contained large amounts of galactose. Swiss cheese made with a galactose-positive strain of Streptococcus thermophilus and a galactose-negative strain of Lactobacillus bulgaricus had little galactose remaining after 28 h, indicating that the Lactobacillus had a stimulatory effect on galactose metabolism in Streptococcus thermophilus. These results indicate that galactose-fermenting Streptococcus thermophilus may have limited potential when used as single strain starter cultures in Swiss cheese, but may be useful when combined with galactose-positive Lactobacillus in the manufacture of Mozzarella cheese.     

Volatile composition and improvement of the aroma of industrial Manchego cheese by using Lactobacillus paracasei subsp. paracasei as adjunct and other autochthonous strains as starters

The use of several autochthonous strains of lactic acid bacteria, including Lactobacillus paracasei subsp. paracasei as adjunct of the starter in the manufacture of Manchego cheese, was evaluated in an attempt to improve the aroma of the industrial Manchego cheese. Volatile composition and odour characteristics were evaluated and compared to those in Manchego cheese manufactured with a commercial starter (CS) culture and with raw milk cheese manufactured without starter. Manchego cheeses manufactured with two autochthonous strains of Lactococcus lactis subsp. lactis displayed a similar volatile profile and odour characteristics to the cheese made with the CS. The use of the strain Lactobacillus paracasei subsp. paracasei CECT 7882 as adjunct of the Lactococcus strains produced cheeses with higher amounts of some free fatty acids and alcohols, acetoin, lactones, phenylacetaldehyde, 2-phenylethanol and linalool, and higher scores of the odour intensity, odour quality, and ewe’s milk odour than the CS cheeses. It resulted in an intensification and improvement of industrial Manchego cheese aroma.     

Proteolytic pattern and organic acid profiles of probiotic Cheddar cheese as influenced by probiotic strains of Lactobacillus acidophilus,Lb. paracasei,Lb. casei or Bifidobacterium sp.

Cheddar cheeses were produced with starter lactococci and Bifidobacterium longum 1941, B. lactis LAFTI^® B94, Lactobacillus casei 279, Lb. paracasei LAFTI^® L26, Lb. acidophilus 4962 or Lb. acidophilus LAFTI^® L10 to study the survival of the probiotic bacteria and the influence of these organisms on proteolytic patterns and production of organic acid during ripening period of 6 months at 4 °C. All probiotic adjuncts survived the manufacturing process of Cheddar cheese at high levels without alteration to the cheese-making process. After 6 months of ripening, cheeses maintained the level of probiotic organisms at >8.0 log₁₀ cfu g⁻¹ with minimal effect on moisture, fat, protein and salt content. Acetic acid concentration was higher in cheeses with B. longum 1941, B. lactis LAFTI^® B94, Lb. casei 279 and Lb. paracasei LAFTI^® L26. Each probiotic organism influenced the proteolytic pattern of Cheddar cheese in different ways. Lb. casei 279 and Lb. paracasei LAFTI^® L26 showed higher hydrolysis of casein. Higher concentrations of free amino acids (FAAs) were found in all probiotic cheeses. Although Bifidobacterium sp. was found to be weakly proteolytic, cheeses with the addition of those strains had highest concentration of FAAs. These data thus suggested that Lb. acidophilus 4962, Lb. casei 279, B. longum 1941, Lb. acidophilus LAFTI^® L10, Lb. paracasei LAFTI^® L26 and B. lactis LAFTI^® B94 can be applied successfully in Cheddar cheese.     

Comparison of growth and survival of single strains of Lactococcus lactis and Lactococcus cremoris during Cheddar cheese manufacture

Traditionally, starter cultures for Cheddar cheese are combinations of Lactococcus lactis and Lactococcus cremoris. Our goal was to compare growth and survival of individual strains during cheesemaking, and after salting and pressing. Cultures used were 2 strains of L. lactis (SSM 7605, SSM 7436) and 2 strains of L. cremoris (SSM 7136, SSM 7661). A standardized Cheddar cheese make procedure was used that included a 38°C cook temperature and salting levels of 2.0, 2.4, 2.8, 3.2, and 3.6% from which were selected cheeses with salt-in-moisture levels of 3.5, 4.5, and 5.5%. Vats of cheese were made using each strain on its own as biological duplicates on different days. Starter culture numbers were enumerated by plate counting during cheesemaking and after 6 d storage at 6°C. Flow cytometry with fluorescent staining by SYBR Green and propidium iodide was used to determine the number of live and dead cells in cheese at the different salt levels. Differences in cheese make times were strain dependent rather than species dependent. Even with correction for average culture chain length, cheeses made using L. lactis strains contained ～4 times (～0.6 log) more bacterial cells than those made using L. cremoris strains. Growth of the strains used in this study was not influenced by the amount of salt added to the curd. The higher pH of cheeses with higher salting levels was attributed to those cheeses having a lower moisture content. Based on flow cytometry, ～5% of the total starter culture cells in the cheese were dead after 6 d of storage. Another 3 to 19% of the cells were designated as being live, but semipermeable, with L. cremoris strains having the higher number of semipermeable cells.     

Applicability of heat-stable deoxyribonuclease assay for assessment of staphylococcal growth and the likely presence of enterotoxin in cheese

The relationships between growth of Staphylococcus aureus and production of deoxyribonuclease and enterotoxin A in cheese were evaluated. Conditions of cheese manufacture, such as the nature of milk used (heated or raw), type of lactic starter, and degree of starter activity, influenced deoxyribonuclease production. There was a close correlation between the S. aureus population and deoxyribonuclease content (correlation .88 in Cheddar and Colby cheeses for normal or inhibited starter, and .85 in Brick cheese for normal starter). Conditions which affected deoxyribonuclease production also had a similar influence on production of enterotoxin A. Detection of the former is especially useful in cheeses which may have had a partial starter failure not detected by the usual criteria of starter activity such as the titratable acidity of whey or the final pH of cheese. While the viable S. aureus population declined during aging, both deoxyribonuclease and enterotoxin A persisted for an extended time (3 yr at 4.4 C) in cheese of normal or inhibited starter.     

Influence of bacteria used as adjunct culture and sunflower oil addition on conjugated linoleic acid content in buffalo cheese

The influence of bacteria and sunflower oil addition on conjugated linoleic acid content (CLA) in buffalo cheese was determined. Fresh and short-ripened cheeses were manufactured using the same starter culture and four different adjunct strains previously selected by their CLA production rate. Lactobacillus casei, Lactobacillus rhamnosus, Bifidobacterium bifidum and Streptococcus thermophilus were individually used as adjunct culture. Sunflower oil (SO) was added to obtain a final concentration of 200 μg/ml of linoleic acid. CLA levels in cheese were higher than raw milk, especially after ripening time. SO supplementation increase CLA concentrations in fresh cheeses, except in those manufactured with S. thermophilus as adjunct culture. Both, ripening and SO supplementation showed a positive influence on CLA concentration. Similar texture, acidity and colour were determined in cheeses with or without SO supplementation. Buffalo cheeses manufactured with appropriate adjunct cultures may be a natural source of CLA for human consumption.     

Nonstarter Lactobacillus strains as adjunct cultures for cheese making: in vitro characterization and performance in two model cheeses

Nonstarter lactic acid bacteria are the main uncontrolled factor in today's industrial cheese making and may be the cause of quality inconsistencies and defects in cheeses. In this context, adjunct cultures of selected lactobacilli from nonstarter lactic acid bacteria origin appear as the best alternative to indirectly control cheese biota. The objective of the present work was to study the technological properties of Lactobacillus strains isolated from cheese by in vitro and in situ assays. Milk acidification kinetics and proteolytic and acidifying activities were assessed, and peptide mapping of trichloroacetic acid 8% soluble fraction of milk cultures was performed by liquid chromatography. In addition, the tolerance to salts (NaCl and KCl) and the phage-resistance were investigated. Four strains were selected for testing as adjunct cultures in cheese making experiments at pilot plant scale. In in vitro assays, most strains acidified milk slowly and showed weak to moderate proteolytic activity. Fast strains decreased milk pH to 4.5 in 8 h, and continued acidification to 3.5 in 12 h or more. This group consisted mostly of Lactobacillus plantarum and Lactobacillus rhamnosus strains. Approximately one-third of the slow strains, which comprised mainly Lactobacillus casei, Lactobacillus fermentum, and Lactobacillus curvatus, were capable to grow when milk was supplemented with glucose and casein hydrolysate. Peptide maps were similar to those of lactic acid bacteria considered to have a moderate proteolytic activity. Most strains showed salt tolerance and resistance to specific phages. The Lactobacillus strains selected as adjunct cultures for cheese making experiments reached 10⁸ cfu/g in soft cheeses at 7 d of ripening, whereas they reached 10⁹ cfu/g in semihard cheeses after 15 d of ripening. In both cheese varieties, the adjunct culture population remained at high counts during all ripening, in some cases overcoming or equaling primary starter. Overall, proximate composition of cheeses with and without added lactobacilli did not differ; however, some of the tested strains continued acidifying during ripening, which was mainly noticed in soft cheeses and affected overall quality of the products. The lactobacilli strains with low acidifying activity showed appropriate technological characteristics for their use as adjunct cultures in soft and semihard cheeses.     

Improvement of texture and structure of reduced-fat Cheddar cheese by exopolysaccharide-producing lactococci

The objective of this study was to evaluate the effect of capsular and ropy exopolysaccharide (EPS)-producing strains of Lactococcus lactis ssp. cremoris on textural and microstructural attributes during ripening of 50%-reduced-fat Cheddar cheese. Cheeses were manufactured with added capsule- or ropy-forming strains individually or in combination. For comparison, reduced-fat cheese with or without lecithin added at 0.2% (wt/vol) to cheese milk and full-fat cheeses were made using EPS-nonproducing starter, and all cheeses were ripened at 7°C for 6 mo. Exopolysaccharide-producing strains increased cheese moisture retention by 3.6 to 4.8% and cheese yield by 0.28 to 1.19 kg/100 kg compared with control cheese, whereas lecithin-containing cheese retained 1.4% higher moisture and had 0.37 kg/100 kg higher yield over the control cheese. Texture profile analyses for 0-d-old cheeses revealed that cheeses with EPS-producing strains had less firm, springy, and cohesive texture but were more brittle than control cheeses. However, these effects became less pronounced after 6 mo of ripening. Using transmission electron microscopy, fresh and aged cheeses with added EPS-producing strains showed a less compact protein matrix through which larger whey pockets were dispersed compared with control cheese. The numerical analysis of transmission electron microscopy images showed that the area in the cheese matrix occupied by protein was smaller in cheeses with added EPS-producing strains than in control cheese. On the other hand, lecithin had little impact on both cheese texture and microstructure; after 6 mo, cheese containing lecithin showed a texture profile very close to that of control reduced-fat cheese. The protein-occupied area in the cheese matrix did not appear to be significantly affected by lecithin addition. Exopolysaccharide-producing strains could contribute to the modification of cheese texture and microstructure and thus modify the functional properties of reduced-fat Cheddar cheese.     

Ripening of Cheddar cheese made from blends of raw and pasteurised milk

Cheddar cheeses were made from pasteurised milk (P), raw milk (R) or pasteurised milk to which 10 (PR10), 5 (PR5) or 1 (PR1) % of raw milk had been added. Non-starter lactic acid bacteria (NSLAB) were not detectable in P cheese in the first month of ripening, at which stage PR1, PR5, PR10 and R cheeses had 10⁴, 10⁵, 10⁶ and 10⁷ cfu NSLAB g⁻¹, respectively. After ripening for 4 months, the number of NSLAB was 1–2 log cycles lower in P cheese than in all other cheeses. Urea–polyacrylamide gel electrophoretograms of water-soluble and insoluble fractions of cheeses and reverse-phase HPLC chromatograms of 70% (v/v) ethanol-soluble as well as -insoluble fractions of WSF were essentially similar in all cheeses. The concentration of amino acids were pro rata the number of NSLAB and were the highest in R cheese and the lowest in P cheese throughout ripening. Free fatty acids and most of the fatty acid esters in 4-month old cheeses were higher in PR1, PR5, PR10 and R cheeses than in P cheese. Commercial graders awarded the highest flavour scores to 4-month-old PR1 cheeses and the lowest to P or R cheese. An expert panel of sensory assessors awarded increasingly higher scores for fruity/sweet and pungent aroma as the level of raw milk increased. The trend for aroma intensity and perceived maturity was R>PR10>PP5>PR1>P. The NSLAB from raw milk appeared to influence the ripening and quality of Cheddar cheese.     

Effect of exopolysaccharide produced by isogenic strains of Lactococcus lactis on half-fat Cheddar cheese

Fat-reduced cheeses often suffer from undesirable texture, flavor, and cooking properties. Exopolysaccharides (EPS) produced by starter strains have been proposed as a mechanism to increase yield and to improve the texture and cooking properties of reduced-fat cheeses. The objective of this work was to assess the influence of an exopolysaccharide on the yield, texture, cooking properties, and quality of half-fat Cheddar cheese. Two pilot-scale half-fat Cheddar cheeses were manufactured using single starters of an isogenic strain of Lactococcus lactis ssp. cremoris (DPC6532 and DPC6533) that differed in their ability to produce exopolysaccharide. Consequently, any differences detected between the cheeses were attributed to the presence of the exopolysaccharide. The results indicated that cheeses made with the exopolysaccharide-producing starter had an 8.17% increase in actual cheese yield (per 100 kg of milk), a 9.49% increase in moisture content, increase in water activity and water desorption rate at relative humidities ≤90%, significant differences in the cheeses microstructure, and a significant improvement in both textural and cooking properties, without negatively affecting the flavor profiles of the cheeses.     

Application of Lactobacillus amylovorus as an antifungal adjunct to extend the shelf-life of Cheddar cheese

Lactobacillus amylovorus DSM 19280 is an antifungal strain that is inhibitory to a range of fungi including Penicillium expansum, Penicillium roqueforti, Aspergillus niger, Aspergillus fumigatus and Fusarium culmorum. In this study, the strain was used as an adjunct culture in a Cheddar cheese model system. During the ripening period, P. expansum spores were applied to the cheese surface to mimic fungal contamination. The presence of the antifungal L. amylovorus adjunct resulted in a four-day delay in appearance of Penicillium growth on the cheese in comparison to the adjunct-free control. When cheeses were exposed to natural airborne fungi, the presence of the adjunct resulted in a six-day delay in the appearance of mycelia on the cheese surface. Significantly, its presence had no detectable negative impact on cheese quality. The results indicate that the strain could have an application for extending the shelf-life of cheeses which are prone to fungal spoilage.