Cheese Flavor Development Research Articles

Genomic Characterization of Wild Lactobacillus delbrueckii Strains Reveals Low Diversity but Strong Typicity.

Investigating the diversity of a given species could give clues for the development of autochthonous starter cultures. However, few studies have focused on the intraspecies diversity of Lactobacillus delbrueckii strains, a technologically important lactic acid bacterium for the dairy industry. For this reason, Lactobacillus delbrueckii strains from the Saint-Nectaire Protected Designation of Origin (PDO) area were isolated and characterized. Genetic diversity was determined based on core genome phylogenetic reconstruction and pangenome analysis, while phenotypic assessments encompassed proteolysis and volatile compound production potential. A total of 15 L. delbrueckii ssp. lactis unique new strains were obtained. The genetic analysis and further proteolytic activities measurement revealed low variability among these Saint-Nectaire strains, while substantial genetic variability was observed within the L. delbrueckii ssp. lactis subspecies as a whole. The volatile compound profiles slightly differed among strains, and some strains produced volatile compounds that could be of particular interest for cheese flavor development. While the genetic diversity among Saint-Nectaire strains was relatively modest compared to overall subspecies diversity, their distinct characteristics and pronounced differentiation from publicly available genomes position them as promising candidates for developing autochthonous starter cultures for cheese production.

Taxonomy, Sequence Variance and Functional Profiling of the Microbial Community of Long-Ripened Cheddar Cheese Using Shotgun Metagenomics.

Shotgun metagenomic sequencing was used to investigate the diversity of the microbial community of Cheddar cheese ripened over 32 months. The changes in taxa abundance were compared from assembly-based, non-assembly-based, and mOTUs2 sequencing pipelines to delineate the community profile for each age group. Metagenomic assembled genomes (MAGs) passing the quality threshold were obtained for 11 species from 58 samples. Although Lactococcus cremoris and Lacticaseibacillus paracasei were dominant across the shotgun samples, other species were identified using MG-RAST. NMDS analysis of the beta diversity of the microbial community revealed the similarity of the cheeses in older age groups (7 months to 32 months). As expected, the abundance of Lactococcus cremoris consistently decreased over ripening, while the proportion of permeable cells increased. Over the ripening period, the relative abundance of viable Lacticaseibacillus paracasei progressively increased, but at a variable rate among trials. Reads attributed to Siphoviridae and Ascomycota remained below 1% relative abundance. The functional profiles of PMA-treated cheeses differed from those of non-PMA-treated cheeses. Starter rotation was reflected in the single nucleotide variant profiles of Lactococcus cremoris (SNVs of this species using mOTUs2), while the incoming milk was the leading factor in discriminating Lacticaseibacillus paracasei/casei SNV profiles. The relative abundance estimates from Kraken2, non-assembly-based (MG-RAST) and marker gene clusters (mOTUs2) were consistent across age groups for the two dominant taxa. Metagenomics enabled sequence variant analysis below the bacterial species level and functional profiling that may affect the metabolic interactions between subpopulations in cheese during ripening, which could help explain the overall flavour development of cheese. Future work will integrate microbial variants with volatile profiles to associate the development of compounds related to cheese flavour at each ripening stage.

The impact of different bacterial blends on texture and flavour development in plant-based cheese

Texture and flavour development in plant-based cheese generally relies on the use of texturizing and flavouring agents. However, fermentation can be a powerful tool to improve those sensorial attributes. Twenty-four different bacterial blends with four different starter cultures and six different adjunct combinations were designed to ferment a pea protein emulsion. Their acidification performance, contribution to gel hardness, and their ability to mask off-flavours and develop dairy-like flavours were evaluated through pH measurement, compression tests, and volatile compounds analysis, respectively. Blends including Vega™ Harmony and Vega™ Classic acidified significantly faster and were more efficient at removing the compounds identified as responsible for the green and/or beany off-flavours attributes in pea matrices. The presence of L. plantarum and L. casei in the blends reduced gel firmness. Dairy-like compounds were detected in all fermented samples and some were produced at different levels depending on the bacterial blend.

Acceleration of proteolysis, flavour development and enhanced bioactivity in a model cheese using Kuflu cheese slurry: An optimisation study

This study aimed to use Kuflu (a mould-ripened cheese) cheese slurry to accelerate ripening, improve biological activity and flavour development in a model cheese in terms of proteolysis and volatile compounds. Response surface methodology (RSM) was employed for the model cheese to determine higher proteolysis and volatile development level during ripening as a function of Kuflu cheese slurry addition level (0–5 %), salt concentration (1–3 %) and ripening temperature (5–15 °C). The highest aminopeptidase activities (0.140 and 0.187 OD/g per hour) were determined in 15-day-old samples containing 3 % and 5 % Kuflu cheese slurry, respectively. Also, the use of Kuflu cheese slurry, regardless of ripening, caused an increase in ABTS*+ antioxidants, angiotensin-converting enzyme (ACE)-inhibition activity and volatile compounds in model cheeses. The sensory evaluation indicated that the use of 3 % (w/w) Kuflu cheese slurry, storage temperature 10 °C for 15 days provided better flavour, odour, texture, colour, appearance and overall acceptability. In conclusion, using Kuflu cheese slurry for model cheese production enhanced the level of proteolysis and volatile flavour composition with shortened ripening time.

Causality Verification for the Correlation between the Presence of Nonstarter Bacteria and Flavor Characteristics in Soft-Type Ripened Cheeses.

Flavor characteristics of ripened cheese are established by various bacteria, such as lactic acid bacteria, Actinobacteria, and Proteobacteria, which spontaneously develop during the cheese-manufacturing process. We previously revealed the relationship between bacterial microbiota and flavor components in soft-type ripened cheeses by using a multiomics approach that combined metagenomics and metabolomics; however, we could not establish a causal relationship. This study aimed to substantiate the causal nature of the correlations revealed by the multiomics approach by using cheese-ripening tests with single isolate inoculation. The bacterial diversity and composition in surface mold-ripened cheeses from Japan and France varied, depending on the differences between the milks (pasteurized or raw), cheese positions (core or rind), and manufacturers. Although the volatile compounds did not clearly reflect the distinctive characteristics of the cheese samples, nonstarter lactic acid bacteria, Actinobacteria, and Proteobacteria positively correlated with ketones and sulfur compounds, as evidenced by a Spearman's correlation analysis. Cheese-ripening tests conducted after inoculation with single bacterial strains belonging to the above-mentioned taxa confirmed that these bacteria formed volatile compounds, in agreement with the correlations observed. In particular, various flavor compounds, such as acids, esters, ketones, and sulfur compounds, were detected in cheese inoculated with Pseudoalteromonas sp. TS-4-4 strain. These findings provide important insights into the role of nonstarter bacteria in the development of cheese flavor and into the effectiveness of the multiomics approach in screening for bacteria that can improve the quality of cheese products. IMPORTANCE Our previous study revealed that the existence of various bacteria, such as lactic acid bacteria, Actinobacteria, and Proteobacteria, clearly correlated with the abundance of flavor components, such as volatile compounds, in soft-type ripened cheeses via a multiomics approach that used 16S rRNA gene amplicon sequencing and headspace gas chromatography-mass spectrometry. However, this approach only showed correlations derived from statistical analyses rather than causal relationships. Therefore, in the present study, we performed cheese-ripening tests using nonstarter bacteria to substantiate the correlations revealed by the multiomics approach in soft-type ripened cheese. Our results suggest the capability of nonstarter bacteria, such as Proteobacteria, to impart flavor to cheese and the effectiveness of the multiomics approach in screening for microbial isolates that can improve the quality of cheese. Overall, our research provides new insights into the importance of bacteria in cheese production.

Modelling the non-linear development of Shenley Station blue cheese volatiles during ripening using untargeted volatile fingerprinting and self-organizing maps

Blue cheese flavour development derives from complex biochemical reactions that depend on numerous factors including milk source, culture/strain selection, processing, and ripening conditions. Understanding volatile compound development during blue cheese ripening will help reduce production costs and facilitate quality improvements. Volatile compounds contribute to the characteristic flavours of the cheeses but ripening time predictions based on chemical data have proven difficult. The present study employed untargeted fingerprinting combined with linear and non-linear chemometric approaches to identify key volatiles for the modelling of Shenley Station blue cheese ripening times. Self-organizing maps and entropy-based feature selection along with partial least squares regression and variable identification coefficients were used to parse the linear and non-linear development behaviours of volatiles. The blue cheese ripening times were accurately modelled by twenty-three discriminant volatiles. The present study demonstrated that volatile fingerprints can be used to effectively model blue cheese ripening times using a non-linear chemometric approach.

Omics Approaches to Assess Flavor Development in Cheese.

Cheese is characterized by a rich and complex microbiota that plays a vital role during both production and ripening, contributing significantly to the safety, quality, and sensory characteristics of the final product. In this context, it is vital to explore the microbiota composition and understand its dynamics and evolution during cheese manufacturing and ripening. Application of high-throughput DNA sequencing technologies have facilitated the more accurate identification of the cheese microbiome, detailed study of its potential functionality, and its contribution to the development of specific organoleptic properties. These technologies include amplicon sequencing, whole-metagenome shotgun sequencing, metatranscriptomics, and, most recently, metabolomics. In recent years, however, the application of multiple meta-omics approaches along with data integration analysis, which was enabled by advanced computational and bioinformatics tools, paved the way to better comprehension of the cheese ripening process, revealing significant associations between the cheese microbiota and metabolites, as well as their impact on cheese flavor and quality.

Enzymolysis Combined with Lactic Acid Bacteria (Lab) Fermentation as Promising Strategies for Cheddar Cheese Flavor Development in Reconstituted Milk System

Enzymolysis Combined with Lactic Acid Bacteria (Lab) Fermentation as Promising Strategies for Cheddar Cheese Flavor Development in Reconstituted Milk System

Genomic and Metabolic Features of an Unexpectedly Predominant, Thermophilic, Assistant Starter Microorganism, Thermus thermophilus, in Chinese Inner Mongolian Cheese.

Inner Mongolian cheese is a traditional dairy product in China. It is produced without rennet, using naturally acidified milk that is simmered to achieve whey separation. In order to analyse the impact of simmering on the microbial community structure, high-throughput sequencing was performed to obtain bacterial 16S rRNA sequences from cheeses from the Ordos (ES), Ulanqab (WS), Horqin (KS) and Xilingol (XS) grasslands of Inner Mongolia. The relative abundance of an unexpected microorganism, Thermus thermophilus, ranged from 2% to 9%, which meant that its dominance was second only to that of lactic acid bacteria (LABs). Genome sequencing and fermentation validation were performed in T. thermophilus N-1 isolated from the Ordos, and it was determined that T. thermophilus N-1 could ingest and metabolise lactose in milk to produce lactate during the simmering process. T. thermophilus N-1 could also produce acetate, propionate, citrate and other organic acids through a unique acetate production pathway and a complete propionate production pathway and TCA cycle, which may affect texture and flavour development in Inner Mongolian cheese. Simultaneously, the large amount of citrate produced by T. thermophilus N-1 provides a necessary carbon source for continuous fermentation by LABs after the simmering step. Therefore, T. thermophilus N-1 contributes to cheese fermentation as a predominant, thermophilic, assistant starter microorganism unique to Chinese Inner Mongolian cheese.

Microbiological characteristics and identification of yeast microbiota of traditional mouldy civil cheese

Investigation of the traditional cheeses and bringing them to the industry contributes to the development of dairy technology in terms of quality and diversity. For this purpose, traditional Turkish mouldy Civil cheese, which has a rich microbial diversity and is lovingly consumed, was studied and its yeast flora revealed. Samples were evaluated in terms of aerobic plate count, psychrotrophic bacteria, proteolytic bacteria, yeast, mould, coliform, enterococci, presumptive lactobacilli, presumptive lactococci, Staphylococcus aureus and Enterobacteriaceae counts. Seventy isolates were characterised by RAPD-PCR with M13 primer. Six diverse species were detected: Yarrowia lipolytica, Kluyveromyces marxianus, Pichia membranifaciens, Debaryomyces hansenii, Pichia fermentans and Candida zeylanoides. As a result, yeast diversity in mouldy Civil cheese may have an important role on development of characteristic blue cheese flavour and selected yeast strains could be used as adjunct culture to improve the quality of the final product.

Adjunct Culture of Non-Starter Lactic Acid Bacteria for the Production of Provola Dei Nebrodi PDO Cheese: In Vitro Screening and Pilot-Scale Cheese-Making.

The present study aimed at selecting non-starter lactic acid bacteria strains, with desirable technological and enzymatic activities, suitable as adjunct culture for the Provola dei Nebrodi cheese production. One hundred and twenty-one lactic acid bacteria, isolated from traditional Provola dei Nebrodi cheese samples, were genetically identified by Rep-PCR genomic fingerprinting, using the (GTG)5-primer, and by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). Twenty-seven strains, included in the qualified presumption of safety (QPS) list, were tested for technological and proteinase/peptidase activities. Results showed that technological features and flavour formation abilities were strain-dependent. Among the selected strains, Lacticaseibacillus paracasei PN 76 and Limosilactobacillus fermentum PN 101 were used as adjunct culture in pilot-scale cheese-making trials. Data revealed that adjunct cultures positively affected the flavour development of cheese, starting from 30 days of ripening, contributing to the formation of key flavour compounds. The volatile organic compound profiles of experimental cheeses was significantly different from those generated in the controls, suggesting that the selected adjunct strains were able to accelerate the flavour development, contributing to a unique profile of Provola dei Nebrodi cheese.

Effect of Pseudomonas fluorescens proteases on the quality of Cheddar cheese

The objective of this study was to investigate the effect of adding different levels of a thermoresistant protease produced by a Pseudomonas fluorescens strain to milk on the manufacture and quality of Cheddar cheese. Fresh raw milk was collected, standardized, and pasteurized at 72°C for 15 s, and the enzyme was added to give a protease activity of 0.15 or 0.60 U/L (treatments P1 and P4, respectively), while one sample had no enzyme added (control). Milk was stored at 4°C for 48 h and Cheddar cheese was manufactured after 0 and 48 h of storage. Results indicated that the protease was active in milk during 48 h of storage; however, its effect on milk composition was minimal. The protein that was preferentially hydrolyzed by the protease over storage was β-casein, followed by κ-casein. The mean cheese yield and recovery of fat and protein obtained for all cheeses were not affected by protease activity. The protease showed low activity during cheese manufacture, possibly because of unfavorable conditions, including low pH. One of the factors that might have influenced protease activity was the pH of the curd (approximately 6.55 after acidification and 5.35 at milling), which was lower than that at which the enzyme would have optimum activity (pH 7 to 9). Consequently, the composition, pH, patterns of proteolysis, and hardness of all cheeses produced were similar and in accordance with values expected for that type of cheese, independently of the protease activity level. However, slight increases in proteolysis were observed in P4 cheeses and produced using milk stored for 48 h. Both the P1 and P4 cheeses had higher concentrations of free amino acids (FAA) compared with the control, whereas urea-PAGE electrophoretograms indicated a greater breakdown of caseins in the P4 cheese samples, which may be related to possible increases in numbers of proteolytic bacteria in milk during storage. Therefore, the thermoresistant psychrotrophic bacterial protease(s) tested in this study may affect the manufacture or quality of Cheddar cheese during ripening to a relatively limited extent. However, controlling initial levels of proteolytic bacteria in raw milk remains essential, because proteolysis affects the development of flavor and texture in cheese.

Phenotypic Diversity of Lactobacillus casei Group Isolates as a Selection Criterion for Use as Secondary Adjunct Starters.

Autochthonous lactic acid bacteria (LAB) play a key role in the development of cheese flavor. As the pasteurization treatment on raw milk causes the elimination of LAB, secondary starter cultures are used in cheese manufacture to obtain cheeses with improved and standardized flavors. In this work, strains of the L. casei group isolated from traditional Italian cheeses were screened for their phenotypic features of technological interest for use as secondary starters. Their milk acidifying performance and the production of volatile compounds when grown in milk were evaluated. Simultaneously, the acetoin metabolic pathway presence was screened in the strains and assessed for its transcriptional activation. The results showed that the analyzed strains, despite belonging to taxonomically-related species, vary greatly according to the measured phenotypes. Four strains among the fourteen screened could be potentially used as adjunct cultures for cheese-making processes. The strain that showed the highest production of acetoin upregulated the aspartate pathway. An increased knowledge of volatile compounds’ production and acidifying properties of LAB strains isolated from traditional dairy products might guide the selection of strains for industrial applications.

Identification and partial characterization of proteolytic activity of Enterococcus faecalis relevant to their application in dairy industry.

Bacteria of the genus Enterococcus are lactic acid bacteria (LAB), which occur ubiquitous in many traditional fermented foods, especially artisanal cheeses, playing positive role in the development of cheese flavor. Moreover, several enterococci are successfully used as a pharmaceutical probiotic and some of them are able to produce bacteriocin and bioactive peptides, thanks to which the possibilities of application of enterococci in dairy technology and biotechnology are increased. The aims of the study were to investigate the proteolytic potential and identify the key enzymes of proteolytic system of Enterococcus faecalis isolated from artisan Polish cheeses. An extracellular - secreted (E) and a cell envelope proteinase (CEP) were isolated and enzyme activity depending on bacterial growth phase was evaluated. CEP showed a higher protease activity than E and this fraction has been purified 70-fold by a method including precipitation, diafiltration and gel filtration chromatography. The molecular mass of the enzyme has been estimated to be ~25 kDa by SDS-PAGE. Maximum enzyme activity of the proteinase has been observed at pH 6,9 and 37 ºC. The enzyme was able to hydrolyze: casein, bovine serum albumin, α-lactalbumin, β-lactoglobulin, but not Leu-pNa. The results of zymography, SDS- PAGE and LC-MS-MS/MS data allowed us to identify the key enzymes of proteolytic system of E. faecalis as coccolysin and glutamylendopeptidase. To asses microbiological safety of the tested strain, the evaluation of the presence of virulence factors and antibiotic susceptibility was also conducted.

Flavour profiles of functional reduced-fat cream cheese: Effects of β-glucan, phytosterols, and probiotic L. rhamnosus

The purpose of this study was to evaluate the individual and combined effect of functional ingredients - β-glucan, phytosterols and probiotic L. rhamnosus on the flavour of functional reduced-fat cream cheese. Eleven samples were investigated for their volatile profiles – five of the cream cheese contained β-glucan, esterified phytosterols, and emulsified phytosterols independently or in combination (β-glucan-esterified phytosterols and β-glucan-emulsified phytosterols) and the remaining six were probiotic-non-encapsulated or encapsulated cream cheese with or without β-glucan/phytosterols. The results were compared with high-fat (11.6% fat) and reduced-fat (5.5% fat) cream cheese containing no functional ingredients and probiotic. A dynamic headspace GC-MS was used for quantifying the volatile compounds found in the samples. Twenty-nine flavour compounds at varying levels were identified: 9 fatty acids, 9 ketones, 9 aldehydes, 2 alcohols. Additionally, high levels of acetic acid (vinegar), hexanoic acid (pungent/sour), octanoic acid, and decanoic acid (rancid, fatty) were also identified in the samples. Addition of L. rhamnosus increased the diacetyl compounds (buttery flavour), but the effect was more pronounced in non-encapsulated rather than encapsulated form. Fatty acid compounds were dominant in cream cheese with phytosterols ester while aldehydes and ketones were responsible for the development of flavour in cream cheese containing phytosterols emulsion.

Cheese yeasts.

Numerous traditionally aged cheeses are surface ripened and develop a biofilm, known as the cheese rind, on their surfaces. The rind of such cheeses comprises a complex community of bacterial and fungal species that are jointly responsible for the typical characteristics of the various cheese varieties. Surface ripening starts directly after brining with the rapid colonization of the cheese surface by yeasts. The initially dominant yeasts are acid and salt-tolerant and are capable of metabolizing the lactate produced by the starter lactic acid bacteria and of producing NH3 from amino acids. Both processes cause the pH of the cheese surface to rise dramatically. This so-called deacidification process enables the establishment of a salt-tolerant, Gram-positive bacterial community that is less acid-tolerant. Over the past decade, knowledge of yeast diversity in cheeses has increased considerably. The yeast species with the highest prevalence on surface-ripened cheeses are Debaryomyces hansenii and Geotrichum candidum, but up to 30 species can be found. In the cheese core, only lactose-fermenting yeasts, such as Kluyveromyces marxianus, are expected to grow. Yeasts are recognized as having an indispensable impact on the development of cheese flavour and texture because of their deacidifying, proteolytic, and/or lipolytic activity. Yeasts are used not only in the production of surface-ripened cheeses but also as adjunct cultures in the vat milk in order to modify ripening behaviour and flavour of the cheese. However, yeasts may also be responsible for spoilage of cheese, causing early blowing, off-flavour, brown discolouration, and other visible alterations of cheese.

Invited review: Bioactive compounds produced during cheese ripening and health effects associated with aged cheese consumption

Traditionally, cheese is manufactured by converting fluid milk to a semisolid mass through the use of a coagulating agent, such as rennet, acid, heat plus acid, or a combination thereof. Cheese can vary widely in its characteristics, including color, aroma, texture, flavor, and firmness, which can generally be attributed to the production technology, source of the milk, moisture content, and length of aging, in addition to the presence of specific molds, yeast, and bacteria. Among the most important bacteria, lactic acid bacteria (LAB) play a critical role during the cheese-making process. In general, LAB contain cell-envelope proteinases that contribute to the proteolysis of cheese proteins, breaking them down into oligopeptides that can be subsequently taken up by cells via specific peptide transport systems or further degraded into shorter peptides and amino acids through the collaborative action of various intracellular peptidases. Such peptides, amino acids, and their derivatives contribute to the development of texture and flavor in the final cheese. In vitro and in vivo assays have demonstrated that specific sequences of released peptides exhibit biological properties including antioxidant, antimicrobial, anti-inflammatory, immunomodulatory, and analgesic/opioid activity, in addition to angiotensin-converting enzyme inhibition and antiproliferative activity. Some LAB also produce functional lipids (e.g., conjugated linoleic acid) with anti-inflammatory and anticarcinogenic activity, synthesize vitamins and antimicrobial peptides (bacteriocins), or release γ-aminobutyric acid, a nonprotein amino acid that participates in physiological functions, such as neurotransmission and hypotension induction, with diuretic effects. This review provides an overview of the main bioactive components present or released during the ripening process of different types of cheese.

Symposium review: Interaction of starter cultures and nonstarter lactic acid bacteria in the cheese environment

The microbiota of ripening cheese is dominated by lactic acid bacteria, which are either added as starters and adjunct cultures or originate from the production and processing environments (nonstarter or NSLAB). After curd formation and pressing, starters reach high numbers, but their viability then decreases due to lactose depletion, salt addition, and low pH and temperature. Starter autolysis releases cellular contents, including nutrients and enzymes, into the cheese matrix. During ripening, NSLAB may attain cell densities up to 8 log cfu per g after 3 to 9 mo. Depending on the species and strain, their metabolic activity may contribute to defects or inconsistency in cheese quality and to the development of typical cheese flavor. The availability of gene and genome sequences has enabled targeted detection of specific cheese microbes and their gene expression over the ripening period. Integrated systems biology is needed to combine the multiple perspectives of post-genomics technologies to elucidate the metabolic interactions among microorganisms. Future research should delve into the variation in cell physiology within the microbial populations, because spatial distribution within the cheese matrix will lead to microenvironments that could affect localized interactions of starters and NSLAB. Microbial community modeling can contribute to improving the efficiency and reduce the cost of food processes such as cheese ripening.

Identification and Functional Validation of Autolysis-Associated Genes in Lactobacillus bulgaricus ATCC BAA-365.

Lactic acid bacteria (LAB) are important organisms in food production. Indeed, LAB autolysis is very critical in dairy processing. For example, it influences the development of cheese flavor by releasing intracellular enzymes, and controls cell growth in yogurts and probiotic products. Two component systems (TCS) constitute essential environmental sensors and effectors of signal transduction in most bacteria. In the present work, mutants of one TCS (LBUL_RS00115/LBUL_RS00110) were generated to assess the relationship between TCS and cell autolysis. The mutants displayed decreased autolysis in comparison with wild type; meanwhile, complementation reversed this effect. The interaction between LBUL_RS00115 and LBUL_RS00110 was confirmed by yeast two-hybrid analysis. These observations suggested that the TCS (LBUL_RS00115/LBUL_RS00110) was involved in autolysis in Lactobacillus delbrueckii subsp. bulgaricus.

Strains of the Lactobacillus casei group show diverse abilities for the production of flavor compounds in 2 model systems

Cheese flavor development is directly connected to the metabolic activity of microorganisms used during its manufacture, and the selection of metabolically diverse strains represents a potential tool for the production of cheese with novel and distinct flavor characteristics. Strains of Lactobacillus have been proven to promote the development of important cheese flavor compounds. As cheese production and ripening are long-lasting and expensive, model systems have been developed with the purpose of rapidly screening lactic acid bacteria for their flavor potential. The biodiversity of 10 strains of the Lactobacillus casei group was evaluated in 2 model systems and their volatile profiles were determined by gas chromatography-mass spectrometry. In model system 1, which represented a mixture of free AA, inoculated cells did not grow. In total, 66 compounds considered as flavor contributors were successfully identified, most of which were aldehydes, acids, and alcohols produced via AA metabolism by selected strains. Three strains (DPC2071, DPC3990, and DPC4206) had the most diverse metabolic capacities in model system 1. In model system 2, which was based on processed cheese curd, inoculated cells increased in numbers over incubation time. A total of 47 compounds were identified, and they originated not only from proteolysis, but also from glycolytic and lipolytic processes. Tested strains produced ketones, acids, and esters. Although strains produced different abundances of volatiles, diversity was less evident in model system 2, and only one strain (DPC4206) was distinguished from the others. Strains identified as the most dissimilar in both of the model systems could be more useful for cheese flavor diversification.