Thermophilic Starter Cultures Research Articles

INVESTIGATION OF THERMOPHILIC MICROFLORA FOR THE SELECTION OF STARTER CULTURE COMPOSITION FOR A FUNCTIONAL PRODUCT

Fermented dairy products have valuable nutrients and contain a large number of living cells of lactic acid bacteria strains of lactic acid bacteria. The selection of microorganisms according to their technological and microbiological properties and their ability to develop in a dairy base, as well as organoleptic and rheological parameters of the finished fermented milk product, is an important stage in the development of new types of products. Therefore, special attention was paid to the selection of starter cultures for the production of a functional product. The authors conducted research on the selection of starter culture microflora for the production of functional products. The microbiological and organoleptic properties of selected microorganisms have been studied. When selecting microorganisms, the intensity and direction of the microbiological and biochemical processes occurring during fermentation were taken into account, which is determined by the development of the starter microflora. Thermophilic starter culture by species Lactobacillus acidophilus, Streptococcus thermophiles, Lactobacillus bulgaricus was used in the work.

Development of camel milk cheese technology and research of qualitative characteristics

Recently, interest in the production of camel milk and products from it has increased due to its nutritional and medicinal properties, including camel milk cheeses.In this study, the technology of cheese from non-pasteurized camel milk using mesophilic and thermophilic starter cultures was developed. The composition of camel milk and its microbiological safety indicators were studied. Next, three experimental types of camel milk cheese were prepared, where the physico-chemical composition, cheese yield, mineral composition and organoleptic parameters were determined. Thus, the content of the mass fraction of fat in the studied samples ranged from 25.45 to 22.13%. The mass fraction of solids for all samples was in the range of 50.50-62.30%; ash content was 3.05-3.65%; and the mass fraction of proteins was 17.49, 22.19%, respectively, in the control sample, cheese using mesophilic and thermophilic starter cultures. The cheese yield ranged from 115.20g/l to 137.98 g/l. The mineral composition of camel milk cheese showed that macronutrients such as Na, Mg, Ca, K, P. predominate in all samples. Also, all experimental samples of camel milk cheese had high organoleptic characteristics.

COMPARATIVE STUDY OF FERMENTATION PROCESSES OF YAK AND COW MILK

Yak milk is a valuable raw material for the production of functional food. Investigation of the fermentation process with commercial starter cultures is conducted to find suitable starters for producing fermented yak milk products on an industrial scale using modern rheological, microbiological, and sensorial methods. According to the acidification curve and rheological measurement, the gel-forming time of yak milk with mesophilic, thermophilic and mixed (meso-thermophilic) starter cultures was not significantly different from cow milk; but, yak milk had a significantly higher gel strength in all cases. The viable bacteria count of fermented samples with thermophilic starters was 8.23 log CFU∙mL-1 for cow milk and 9.12 log CFU∙mL-1 for yak milk. During cold storage (72 h), the CFU in yak milk remained higher (98.48% – 101.22%) during the storage period than that of cow milk (90.33% – 95.06%). The sensorial property scores of yak milk fermented with mixed starters were the highest, followed by those of milk fermented with mesophilic and thermophilic starter cultures. The obtained parameters show that mesophilic and mixed cultures are advantageous in terms of sensorial and probiotic properties, and thermophilic culture - in terms of gel strength. All this information is useful for the development of new dairy products.

Storage related changes in short-set cream cheese manufactured using thermophilicstarter culture and direct acidification technique

Cream cheese is a fresh acid curd variety with semi-soft body, manufactured by the gradual, quiescent acid gelation of milk. The typical flavour profile of cream cheese is cultured diacetyl with little bit lactic acid flavour as well as aroma. It is envisaged that demand of cream cheese will increase in upcoming years due to its application as spread and it having higher nutritional value compared to similar products available in the market. The purpose of the study was to observe changes in sensory, physicochemical and microbial quality during storage in short-set cream cheese samples manufactured by using thermophilic starter culture and direct acidification technique and was compared with control cream cheese manufactured using mesophilic starter culture. All the three samples i.e., control cream cheese made using mesophilic culture (MC), cream cheese made using thermophilic culture (TC) and cream cheese made using laboratory grade lactic acid (SLA) were stored in re-closable polypropylene tubs at 7 ± 2°C. During storage study, flavour score, FFA, tyrosine value were significantly affected by storage period (P), treatment (T) and the interaction of T × P. Moisture, pH, titratable acidity, sensory parameters (except flavour) were significantly affected only by storage period (P) and treatment(T). All the three samples had storage stability up to 15 days at 7± 2°C.

Recreating pink defect in cheese with different strains of Thermus bacteria

Pink discoloration defects in cheese manifests as the appearance of pink patches within cheese blocks and has recently been associated with Thermus thermophilus. Swiss‐type cheeses were prepared at pilot scale using thermophilic starter cultures, Propionibacterium freudenreichii, and one of Thermus thermophilus HB27, Thermus scotoductus SE1 or Thermus thermophilus DPC6866 or a control without Thermus. Significantly, a higher level of redness was observed in cheeses with Thermus thermophilus HB27 relative to the other cheeses and suggests that the development of the pink defect is dependent on the strain of Thermus present and on other, as yet unknown, factors that require further study.

Influence of starter culture on nitrogen fraction and volatile compounds in Beaten cow's milk cheese

The aim of this investigation was to characterize the influence of selected starters (Streptococcus thermophilus, Lb. casei, Lactobacillus delbrueckii subsp. bulgaricus, Lactococcus lactis subsp. lactis and Lc. lactis subsp. cremoris) on gross composition, the breakdown of proteins or peptides, and volatile compounds of the beaten cheese made from cow's milk. Results showed a low level of primary proteolysis, expressed by a low content of non-casein nitrogen (NCN), in raw cow's cheeses. Greater differences were observed in RP-HPLC peptide profiles between the cheeses manufactured with or without starter cultures during ripening. Volatile profiles including alcohols (17), ketones (33), esters (10), acids (7), and miscellaneous (4) were differed based on used starter culture. Variations on the chemical composition, peptides, and flavor profiles of beaten cheeses are due to the effect of important peptidase activity of each cell species of starter culture used in cheese production. Practical applications Lactic acid bacteria provide to beaten cheese flavor quality with their peptidase activity. Traditional cheese-making technology is made without the addition of lactic acid bacteria depending on the indigenous flora of the milk for ripening. Recently, mesophilic and/or thermophilic starter cultures were used in the manufacture of Beaten cheese. No previous investigation on using starter culture in Beaten cheese has been published and may ensure details to upgrade the technology and ripening by extending the flavor of the current product as its standard variety. Starter cultures can increase flavor evolution or contribute additional flavors to cheese as it matures and control off-flavors in matured cheeses that can considerably economize the cheese production.

Effect of commercial yogurt starter cultures on fermentation process, texture and sensoric parameters of white yogurt

In this work, we have compared and described the fermentation process of two commercial yogurt starter cultures during the white yogurt production. We used freeze-dried thermophilic starter culture YoFlex® YF - L812 and deep-frozen starter culture Delvo® Fresh YS – 241 for the production of white yogurts. We analysed titration acidity, active acidity, total viable counts, texture, and sensory parameters of white yogurts produced in laboratory conditions. This research was performed for dairy company Mliekareň Kopanice Selce, s.r.o., Slovakia. We did not found statistically significant differences (p >0.05) in titration acidity of both yogurts after 7 hours of fermentation. We did not found statistically significant differences (p >0.05) in the pH of both yogurts after 7 hours of fermentation. We found statistically significant differences (p <0.05) in all textural parameters (hardness, consistency, cohesion, and viscosity). The total viable count of microorganisms in yogurts after 24 hours of fermentation was 6.28 x 107 and 7.14 x 107 respectively.

Potential growth of Listeria monocytogenes in Italian mozzarella cheese as affected by microbiological and chemical-physical environment

In the present study, 33 brands of mozzarella cheese (pasteurized cow milk mozzarella obtained by direct acidification through the addition of food-grade citric acid or obtained by natural acidification through the addition of thermophilic starter cultures, mozzarella for pizza mainly obtained by addition of citric acid, and pasteurized buffalo milk mozzarella obtained by adding microbial rennet) were characterized for the factors potentially influencing the growth of Listeria monocytogenes (microbial populations, moisture, pH, and organic acids). Then, the growth potential of L. monocytogenes in mozzarella was investigated by challenge tests performed at different temperatures. The presence of heterogeneous microflora (lactobacilli, streptococci, Pseudomonas spp., and, for buffalo mozzarella, yeasts) was evidenced. Almost all the product typologies were classified as high-moisture mozzarella cheese because moisture was >52%. Moreover, pH varied from 5.32 to 6.43 depending on the manufacturing methodology applied. Organic acid concentrations too showed great variability depending on the mozzarella production method, with values ranging from less than limit of detection (LOD; 16 mg/kg) to 14,709 mg/kg, less than LOD (216 mg/kg) to 29,195 mg/kg, and less than LOD (47 mg/kg) to 1,725 mg/kg in the water phase of lactic, citric, and acetic acids, respectively. Despite this presence, the concentration of undissociated acids was lower compared with the minimum inhibitory concentrations estimated for L. monocytogenes by other authors. This was confirmed by the results of the challenge tests conducted inoculating the pathogen in mozzarella produced with the addition of citric acid, as the microorganism grew fast at each temperature considered (4, 9, 15, and 20°C). Good hygiene practices should be strictly applied, especially with the aim of avoiding postproduction contamination of mozzarella, as the presence of organic acids and microflora is insufficient to prevent L. monocytogenes growth.

Novel isolates of Streptococcus thermophilus bacteriophages from group 5093 identified with an improved multiplex PCR typing method

Bacteriophages are a persistent problem in dairy plants. Streptococcus thermophilus is a component of thermophilic starter cultures used for cheese and yoghurt production. In this study, a multiplex PCR method was adapted to identify, in a single reaction, all known S. thermophilus phage groups. The method was compared with the previously published multiplex PCR typing method and showed higher specificity for classifying purified phage isolates. Three new representatives of phage group 5093, which were discovered with the developed PCR method, were genome sequenced and the genomes were compared with those available in GenBank. A validation of the two typing methods performed with whey revealed limitations of multiplex PCR assays when applied for the detection of phages in dairy samples. This study established an improved multiplex PCR method for classifying purified S. thermophilus phages, and expanded the genetic information of group 5093, both important steps to control phage infections in dairies.

Effect of levels of starter culture and varients of packaging materials on the quality characteristics of enriched misti dahi

The research was undertaken to access the effect of starter culture on the qualitative characteristics of whey protein enriched misti dahi through incorporation of whey protein concentrate @ 2.0 % whey protein concentrate and fruit juice (apple and orange - 1:1) @ 15.0 % by weight. The thermophilic starter cultures were added @ 1.0, 2.0 and 3.0 % level. Incorporation of starter culture @ 2.0 % rate yielded product having acceptable sensory attributes. Misti dahi packaged in polyethylene teraphthalate (PET) cups could be stored for longer period (i.e. 15 days) as compared to use of polystyrene, polypropylene cups or even earthen pots, when stored under refrigerated (4±2 oC) condition.

The effect of starters with a functional arginine deiminase pathway on cheese ripening and quality

The arginine deiminase (ADI) pathway catalyses the degradation of l-arginine via the intermediate l-citrulline into l-ornithine, ammonia, and CO2. This constitutes an important metabolic feature of some lactic acid bacteria (LAB) in their response to acid stress. We investigated the capacity of four thermophilic starters to degrade arginine via the ADI pathway and studied their influence on the ripening and quality of experimental Gruyere cheeses. One of the starters could not degrade arginine, while another had an impaired ADI pathway and formed mainly citrulline. In cheeses produced with the two starters exhibiting a fully functional ADI pathway, ornithine content, pH-value, and CO2 and eye formation were significantly increased, indicating that the quality and ripening of the cheeses were affected by ADI metabolism. This is the first study investigating thermophilic starter cultures that contain Lactobacillus delbrueckii subsp. lactis with a functional ADI pathway converting arginine into ornithine and CO2 in cheese.

Novel Variants of Streptococcus thermophilus Bacteriophages Are Indicative of Genetic Recombination among Phages from Different Bacterial Species

ABSTRACTBacteriophages are the main cause of fermentation failures in dairy plants. The majority of Streptococcus thermophilus phages can be divided into either cos- or pac-type phages and are additionally characterized by examining the V2 region of their antireceptors. We screened a large number of S. thermophilus phages from the Chr. Hansen A/S collection, using PCR specific for the cos- or pac-type phages, as well as for the V2 antireceptor region. Three phages did not produce positive results with the assays. Analysis of phage morphologies indicated that two of these phages, CHPC577 and CHPC926, had shorter tails than the traditional S. thermophilus phages. The third phage, CHPC1151, had a tail size similar to those of the cos- or pac-type phages, but it displayed a different baseplate structure. Sequencing analysis revealed the genetic similarity of CHPC577 and CHPC926 with a subgroup of Lactococcus lactis P335 phages. Phage CHPC1151 was closely related to the atypical S. thermophilus phage 5093, homologous with a nondairy streptococcal prophage. By testing adsorption of the related streptococcal and lactococcal phages to the surface of S. thermophilus and L. lactis strains, we revealed the possibility of cross-interactions. Our data indicated that the use of S. thermophilus together with L. lactis, extensively applied for dairy fermentations, triggered the recombination between phages infecting different bacterial species. A notable diversity among S. thermophilus phage populations requires that a new classification of the group be proposed.IMPORTANCE Streptococcus thermophilus is a component of thermophilic starter cultures commonly used for cheese and yogurt production. Characterizing streptococcal phages, understanding their genetic relationships, and studying their interactions with various hosts are the necessary steps for preventing and controlling phage attacks that occur during dairy fermentations.

Process Standardization for the Manufacture of Mango flavoured steamed Sweetened Concentrated Yoghurt (Bhapadahi)

The present investigation was carried out with the objective of developing a ‘value-added’ mango flavoured sweetened concentrated yogurt (SCY referred to in India as Bhapa dahi) based on chakka(an intermediate dairy product obtained by partial draining of whey from yogurt) and sweetened (partly skimmed) condensed milk (SCM). Bhapa dahi was prepared adopting the process standardized by Bhattacharya et al. [1]; the modifications being substituting plain condensed milk with SCM and increasing the steaming period. The process standardization involved (i) Selecting the thermophilic starter culture from amongst Y-170F, Yo-Flex and Y-480F, (ii) Choosing the best admixture of chakka and SCM from amongst three proportions (viz., 40:60, 45:55 and 50:50 w/w), and (iii) Selecting the optimum steaming treatment required to for a gelled fermented product. The rate of addition of mango pulp was kept constant at 18.0 % by weight of base mix (i.e. chakka plus SCM). The SCY samples were subjected to analysis for their proximate composition, texture profile and sensory quality. (iv) The standardized process for the manufacture of mango flavoured SCY involved use of Y-170F thermophilic yoghurt culture at the rate of 0.15 g/l of milk to obtain the curd; utilizing chakka plus SCM in the proportion of 1:1 (w/w) as the base mix and steaming (cooking) the blend of base mix plus mango pulp for a period of 15 min.

Effect of buffalo milk on the yield and composition of buffalo feta cheese at various processing parameters

Abstract The aim of this study was to analyze the composition of Iranian buffalo milk and study the effect of different parameters such as fat content, acidity of milk, starter culture and temperature on the composition of buffalo feta cheese. The feta cheese yields obtained from buffalo milk were higher in comparison with the yields reported for cow milk. Higher yields were obtained when the fat content of the milk was increased. Rise in the raw milk acidity increased the yield and reduced the fat, protein and lactose loses. Thermophilic and mesophilic starter cultures exhibited better activities at 38 °C and 34 °C, respectively. Pasteurization resulted in significantly (p 0.05). The results of this study revealed that buffalo milk could be regarded as a good source for the production of feta cheese due to elevated amounts of fat, protein and Ca. The results showed that optimum conditions were needed to achieve the higher yields.

Microbial community dynamics in thermophilic undefined milk starter cultures

Model undefined thermophilic starter cultures were produced from raw milk of nine pasta-filata cheesemaking plants using a selective procedure based on pasteurization and incubation at high temperature with the objective of studying the microbial community dynamics and the variability in performances under repeated (7–13) reproduction cycles with backslopping. The traditional culture-dependent approach, based on random isolation and molecular characterization of isolates was coupled to the determination of pH and the evaluation of the ability to produce acid and fermentation metabolites. Moreover, a culture-independent approach based on amplicon-targeted next-generation sequencing was employed. The microbial diversity was evaluated by 16S rRNA gene sequencing (V1–V3 regions), while the microdiversity of Streptococcus thermophilus populations was explored by using novel approach based on sequencing of partial amplicons of the phosphoserine phosphatase gene (serB). In addition, the occurrence of bacteriophages was evaluated by qPCR and by multiplex PCR. Although it was relatively easy to select for a community dominated by thermophilic lactic acid bacteria (LAB) within a single reproduction cycle, final pH, LAB populations and acid production activity fluctuated over reproduction cycles. Both culture-dependent and -independent methods showed that the cultures were dominated by either S. thermophilus or Lactobacillus delbrueckii subsp. lactis or by both species. Nevertheless, subdominant mesophilic species, including lactococci and spoilage organisms, persisted at low levels. A limited number of serB sequence types (ST) were present in S. thermophilus populations. L. delbrueckii and Lactococcus lactis bacteriophages were below the detection limit of the method used and high titres of cos type S. thermophilus bacteriophages were detected in only two cases. In one case a high titre of bacteriophages was concurrent with a S. thermophilus biotype shift in the culture.This study largely confirms previous data on the composition of undefined thermophilic starters used for the production of traditional cheeses in Italy but it is the first one to systematically address the dynamics of the cultures under a repeated reproduction regime with backslopping.

Fermented milk products: effects of lactose hydrolysis and fermentation conditions on the rheological properties

Lactose-free dairy products become increasingly important for lactose-intolerant consumers, but there are only few studies concerning the rheological properties of fermented dairy products from lactose-hydrolysed milk. Hydrolysation was performed with commercial β-galactosidase either before or during fermentation (co-hydrolysis). In each trial, fermentation of the base milk was carried out simultaneously using the same starter cultures for (a) untreated milk (reference) (b) hydrolysed milk as substrate and (c) by performing lactose hydrolysis and fermentation simultaneously (co-hydrolysis). In total, five thermophilic starter cultures and two products (yoghurt and Greek-style yoghurt) were investigated. Results show that the influence of hydrolysis of lactose on the properties of the fermented dairy products strongly depends on starter culture and substrate. For starters C and D, apparent viscosity (extracted from flow curves at a shear rate of 75 s−1) of fermented milks was only marginally affected by lactose hydrolysis, ranging between approx. 0.34–0.31 and 0.37–0.31 Pa.s, respectively. Hydrolysed products from starters A and E exhibited significant lower apparent viscosity (0.16 and 0.24 Pa.s) compared with their respective references (0.29 and 0.35 Pa.s). Fermentation of both substrates (regular yoghurt, Greek-style yoghurt) with starter B resulted in a decrease of yield stress and apparent viscosity because of lactose hydrolysis only for Greek-style yoghurt. Furthermore, a trend towards higher EPS synthesis was found when using hydrolysed milk. The results clearly show that products made from lactose-hydrolysed milk with similar rheological properties as the reference product can be obtained but that there is a lack of information concerning the complex interactions between starter culture and milk substrate.

Effect of starters and ripening time on the physicochemical, nitrogen fraction and texture profile of goat's cheese coagulated with a vegetable coagulant (Cynara cardunculus )

The increase in the demand for goat's cheese throughout the world has encouraged research into the development of new related products with different textural characteristics. The aim of this work was to study the effect of three commercial starter cultures through the assessment of physicochemical and textural characteristics of goat's milk cheeses made with vegetable coagulant (Cynara cardunculus) during ripening. Use of the different starter cultures produced a significant effect (P < 0.05) on moisture, proteins, pH, nitrogen fractions and hardness of the cheeses. Results show that the addition of mesophilic starters ensures the correct acidification rate and produced cheeses with lower pH values and greater hardness. Use of thermophilic starter cultures produces cheeses with less instrumental hardness and the use of mixed cultures produced less proteolysis. These results are found useful for selecting the most suitable starter for the development of new goat's cheeses.

Development of a multiplex real time PCR to detect thermophilic lactic acid bacteria in natural whey starters

A multiplex real time PCR (mRealT-PCR) useful to rapidly screen microbial composition of thermophilic starter cultures for hard cooked cheeses and to compare samples with potentially different technological properties was developed. Novel primers directed toward pheS gene were designed and optimized for multiple detection of Lactobacillus helveticus, Lactobacillus delbrueckii, Streptococcus thermophilus and Lactobacillus fermentum. The assay was based on SYBR Green chemistry followed by melting curves analysis. The method was then evaluated for applications in the specific detection of the 4 lactic acid bacteria (LAB) in 29 different natural whey starters for Parmigiano Reggiano cheese production. The results obtained by mRealT-PCR were also compared with those obtained on the same samples by Fluorescence in Situ Hybridization (FISH) and Length-Heterogeneity PCR (LH-PCR).The mRealT-PCR developed in this study, was found to be effective for analyzing species present in the samples with an average sensitivity down to less than 600 copies of DNA and therefore sensitive enough to detect even minor LAB community members of thermophilic starter cultures. The assay was able to describe the microbial population of all the different natural whey starter samples analyzed, despite their natural variability. A higher number of whey starter samples with S. thermophilus and L. fermentum present in their microbial community were revealed, suggesting that these species could be more frequent in Parmigiano Reggiano natural whey starter samples than previously shown. The method was more effective than LH-PCR and FISH and, considering that these two techniques have to be used in combination to detect the less abundant species, the mRealT-PCR was also faster. Providing a single step sensitive detection of L. helveticus, L. delbrueckii, S. thermophilus and L. fermentum, the developed mRealT-PCR could be used for screening thermophilic starter cultures and to follow the presence of those species during ripening of derived dairy products. A major increase in understanding the starter culture contribution to cheese ecosystem could be harnessed to control cheese ripening and flavor formation.

Effects of high pressure treatment on glycolytic enzymes of Lactococcus lactis subsp. lactis, Streptococcus thermophilus and Lactobacillus acidophilus

High pressure processing (HPP) reduces the glycolytic activity of lactic acid bacteria (LAB) and provides a means to control further production of acidic metabolites in fermented dairy products during storage. However, there is limited information on the effects of HPP on specific enzymes of dairy starter bacteria responsible for the metabolism of lactose. The aim of this study was to determine pressure-induced inactivation of glycolytic enzymes in Lactococcus lactis subsp. lactis C10, Streptococcus thermophilus TS1 and Lactobacillus acidophilus 2400. Cultures were grown for 16 h in M17 or MRS broth containing 5% (w/v) lactose at pH 6.5 (maintained by addition of 10 M NaOH). The cells were harvested by centrifugation, washed and resuspended in 100 mM phosphate buffer (pH 6.5) and pressure-treated at 300 and 600 MPa (≤ 22 °C, 5 min). The ability of pressure-treated resting cells of Lactococcus, incubated with 5% (w/v) lactose at 30 °C, to ferment lactose was evaluated by determining titratable acidity (TA) during incubation. The activities of phospho-β-galactosidase (P-β-gal), β-galactosidase (β-gal) and lactate dehydrogenase (LDH) were determined in cell-free extracts of untreated and pressure-treated cells. Resting cells of Lactococcus treated at 600 MPa had a substantially lower rate of acidification than the controls and those treated at 300 MPa. Both P-β-gal and β-gal were significantly inactivated (p < 0.01) in the starter cultures treated at 300 or 600 MPa. The LDH in Lactococcus and Lactobacillus was highly resistant to pressure treatment at 300 MPa. In contrast, the LDH in Streptococcus was almost completely inactivated at ≥ 300 MPa. Industrial relevance Continuing production of acidic metabolites in fermented dairy products during storage can be a technological challenge that adversely affects product quality. The current study demonstrates that high pressure processing (HPP) offers the potential of controlling this problem by inactivation of glycolytic enzymes in various mesophilic and thermophilic starter cultures. The findings of this research will assist in establishing optimised operating parameters for HPP treatment of cultured products to extend shelf-life, by reducing acid production during storage.

Exploitation of the diverse insertion sequence element content of dairy Lactobacillus helveticus starters as a rapid method to identify different strains

The species Lactobacillus helveticus is a commonly used thermophilic starter and/or adjunct culture for Swiss and Cheddar cheese manufacture. Its use is normally associated with flavour improvement which is known to be associated with culture traits such as rapid autolysis and high proteolytic activity. The genome of the commercial strain, DPC4571, was recently sequenced and found to have an abundance of IS sequences in terms of both abundance (213 intact) and diversity (21 types). Given this unique diversity for a lactic acid bacterium, we investigated whether PCR-based IS fingerprinting could be used as a discriminatory tool to distinguish between different strains of Lb. helveticus. A set of ten primers targeting five of the most numerous groups (ISL 1201, ISLhe 65, ISLhe 2, ISLhe 15 and ISL 2) of IS elements was designed. Multiplex-PCR with all primers resulted in 1 – 12 discreet amplicons for each strain tested. The resultant fingerprints (in the 0.5 kb – 3 kb range) were found to be strain specific and reproducible. This approach thus provides a valuable method to distinguish between Lb. helveticus strains while giving some indication of the relative abundance of IS sequences in each strain.