Commercial Meat Starter Cultures Research Articles

Effect of Blanching Plus Fermentation on Selected Functional Properties of Mealworm (Tenebrio molitor) Powders.

The aim of this study was to determine the effect of blanching followed by fermentation of mealworms (Tenebrio molitor) with commercial meat starter cultures on the functional properties of powders produced from the larvae. Full fat and defatted powder samples were prepared from non-fermented and fermented mealworm pastes. Then the crude protein, crude fat, and dry matter contents, pH, bulk density, colour, water and oil binding capacity, foaming capacity and stability, emulsion capacity and stability, protein solubility, quantity of free amino groups, and protein composition of the powders were evaluated. Regardless of the starter culture used, the blanching plus fermentation process reduced the crude and soluble protein contents of the full fat powders and in general impaired their water and oil binding, foaming, and emulsifying properties. Defatting of the powders improved most functional properties studied. The o-phthaldialdehyde assay revealed that the amount of free amino groups was higher in the fermented powders while sodium dodecyl sulfate polyacrylamide gel electrophoresis demonstrated that the soluble proteins of the fermented powders were composed of molecules of lower molecular mass compared to non-fermented powders. As molecular sizes of the soluble proteins decreased, it was clear that the protein structure was also modified by the fermentation process, which in turn led to changes in functional properties. In general, it was concluded that fermentation of mealworms with blanching as a pre-treatment does not contribute to the functional properties studied in this work. Nevertheless, the results confirmed that the properties of non-fermented powders are comparable to other food protein sources.

Degradation of PCBs in dry fermented sausages during drying/ripening

The effects of several commercial meat starter cultures on degradation of polychlorinated biphenyls (PCBs) in dry fermented sausages over 28days of drying/ripening were investigated. The sausage batter was prepared according to a classic recipe and spiked with a standard solution of a PCB congener mixture. With addition of different commercial meat starter cultures, five experimental groups were prepared: no further addition; and separate addition of each of four starter cultures: Texel DCM-1, Texel LM-30, Biostar Sprint, and SM-181. Samples were taken at the beginning of fermentation (zero time), and after 4, 7, 14, 21 and 28days. PCB residues were extracted with hexane. The PCB contents were determined using gas chromatography–mass spectrometry. The PCB levels were reduced in all of the experimental groups tested, where addition of starter culture Biostar Sprint (Lactobacillus sakei, Staphylococcus carnosus, Staphylococcus xylosus) showed the highest PCB degradation rates.

EVALUATION OF FUNCTIONAL ASPECTS IN LACTOBACILLUS STRAINS ISOLATED FROM DRY FERMENTED SAUSAGES

ABSTRACT The aim of this study was to characterize lactobacilli isolated from a traditional Italian dry‐fermented sausages inoculated with Lactobacillus casei/paracasei for use as probiotics. Strains isolated were L. casei (38%), L. paracasei paracasei (32%), Lactobacillus rhamnosus (21%) and Lactobacillus sakei sakei (9%). L. paracasei paracasei and L. rhamnosus showed no significant decrease in viability compared with L. casei and L. sakei sakei in artificial gastric juice; L. casei and L. sakei sakei were not affected by artificial intestinal fluid. In human embryonic intestine cell line (INT407) in vitro model, L. rhamnosus and L. sakei sakei were more adhesive than the other strains. The production of acetic acid (40.92 ± 1.94 mmol/L) and propionic acid (0.14 ± 0.07 mmol/L) was similar in all strains tested. Considerably higher (100–250 mmol/L) levels of lactic acid were produced by L. casei, L. paracasei paracasei and L. rhamnosus, and were varied depending on microaerobic or anaerobic conditions. L. casei and L. rhamnosus had the best antibacterial activity against Escherichia coli and Salmonella enterica ssp. enterica (serovar Typhimurium). These findings suggest that L. casei and L. rhamnosus merit further investigation as novel starter cultures in meat products.PRACTICAL APPLICATIONSProbiotics are well established in dairy products but they are not widely used in meat products and it is expected their use in this area will expand considerably in the near future. Starter cultures of active or resting forms of microorganisms are widely employed in fermented meat products to improve sensory qualities. More recently they are being used in fermented meat products to improve the nutritional value of these products as functional foods. Probiotics in meat may exert their benefits by several methods, and more research is required to identify the strains and combinations of strains that produce the most health benefits. Our study demonstrates that the in vitro characterization of Lactobacillus strains directly isolated from dry fermented sausages can be useful to select novel starter cultures with potential probiotic characteristics among lactic acid bacteria used as commercial meat starter culture.

Identification of Lactobacillus sakei genes induced during meat fermentation and their role in survival and growth.

Lactobacillus sakei is a lactic acid bacterium that is ubiquitous in the food environment and is one of the most important constituents of commercial meat starter cultures. In this study, in vivo expression technology (IVET) was applied to investigate gene expression of L. sakei 23K during meat fermentation. The IVET vector used (pEH100) contained promoterless and transcriptionally fused reporter genes mediating beta-glucuronidase activity and erythromycin resistance. A genomic library of L. sakei 23K was established, and the clones were subjected to fermentation in a raw-sausage model. Fifteen in carne-induced fusions were identified. Several genes encoded proteins which are likely to contribute to stress-related functions. One of these genes was involved in acquisition of ammonia from amino acids, and the remaining either were part of functionally unrelated pathways or encoded hypothetical proteins. The construction and use of isogenic mutants in the sausage model suggested that four genes have an impact on the performance of L. sakei during raw-sausage fermentation. Inactivation of the heat shock regulator gene ctsR resulted in increased growth, whereas knockout of the genes asnA2, LSA1065, and LSA1194 resulted in attenuated performance compared to the wild-type strain. The results of our study are the first to provide an insight into the transcriptional response of L. sakei when growing in the meat environment. In addition, this study establishes a molecular basis which allows investigation of bacterial properties that are likely to contribute to the ecological performance of the organism and to influence the final outcome of sausage fermentation.

Identification of potential probiotic starter cultures for Scandinavian-type fermented sausages

Potential probiotic cultures suitable as starter cultures for the Scandinavian-type fermented sausages were identified among strains well-adapted to fermented meats as well as strains originating from a culture collection. From 15 different fermented meat products, 22 strains were isolated as dominant non-starter lactic acid bacteria (NSLAB). The isolates were identified by RAPD, API and sequence analysis of 16S rRNA and showed to be five strains of Lactobacillus sakei, five strains of Lactobacillus farciminis, five strains belonging to the group of Lactobacillus plantarum/ pentosus, four strains of Lactobacillus alimentarius, two strains of Lactobacillus brevis and one strain of Lactobacillus versmoldensis. Heterofermentative strains as well as strains not growing at 37 °C and not lowering pH below 5.1 in a meat model were excluded leaving 9 strains for further studies. These strains together with 19 strains from a culture collection were evaluated by in vitro methods including survival upon exposure to pH 2.5 or 0.3% oxgall and adhesion to the human colon adenocarcinoma cell line Caco-2 as well as antimicrobial activity against potential pathogens. Strains that fulfilled all the probiotic criteria and showed to be fast acid producers in a meat model included three strains belonging to the group of Lb. plantarum/ pentosus (MF1291, MF1298, MF1300) which originated from the dominant NSLAB of fermented meat products. MF1291 and MF 1298 were further identified as Lb. plantarum and MF1300 as Lb. pentosus. The three strains were all successfully applied as starter cultures for the production of fermented sausage. The viable count at the end of the processing period reached high cell numbers (4.7 × 10 7–2.9 × 10 8 cfu/g) and pH of the sausages decreased to pH 4.8–4.9 without any flavour deviation compared to sausage fermented by a commercial meat starter culture.

MODELLING INTERACTIONS BETWEEN BACTERIOCIN-PRODUCING SAUSAGE STARTER CULTURES OR COCULTURES AND LISTERIA REVEALS HOW TO IMPROVE THE EFFICIENCY OF LISTERIA KILLING

The kinetics of Listeria innocua LMG 13568 were studied in vitro during laboratory batch fermentation experiments in the presence of the bacteriocin-producing strains Lactobacillus sakei CTC 494, Lactobacillus curvatus LTH 1174, and Enterococcus faecium RZS C5. A comparison was made with a non-bactcriocin-producing commercial meat starter culture of Lb. sakei. The L. innocua LMG 13568 population consisted predominantly of bacteriocin-sciisitive cells but also contained a small subpopulation of bacteriocin-resistant cells (resistance frequency of 4x10 -4 ). Bacteriocin production by Lb. sakei CTC 494 and Lb. curvatus LTH 1174 in a meat simulation medium resulted in the rapid inactivation of sensitive L. innocua LMG 13568 cells, even in the very early stages of bacteriocin production at low bacteriocin activity levels. The inhibition obtained by E. faecium RZS C5 was less pronounced but was better than with a non-bacteriocin-producing starter culture. The harsh conditions typical for a sausage environment (low temperature and pH and high amounts of salt and nitrite) were enough to control the bacteriocin-resistant subpopulation. Hence, bticteriocin-producing starter cultures used under appropriate sausage manufacturing conditions may guarantee a Listeria-free end-product.

Flavour profiles of dry sausages fermented by selected novel meat starter cultures

Probiotic or bioprotective Lactobacillus rhamnosus strains GG, LC-705 and E-97800 as well as Pediococcus pentosaceus E-90390 and Lactobacillus plantarum E-98098 were studied for their ability to act as main fermenting organisms in the manufacturing process of dry sausages. In the preliminary tests, their abilities to produce lactic acid and biogenic amines, histamine or tyramine, were studied in MRS broth and analysed by high-performance liquid chromatography. The strains produced higher or equal amounts of lactic acid compared to control and were amine negative. During the actual fermentation process of dry sausages the numbers of inoculated bacteria increased from the level 6.5–7.0 log cfu/g to 8.0–9.0 log cfu/g. The most fast growing strains were P. pentosaceus E-90390 and the control while the growth of L. plantarum E-98098 and L. rhamnosus LC-705 were the slowest. The pH value of the sausages decreased from 5.6 to 4.9–5.0. The presence of these experimental strains as major organisms in the sausages after fermentation and ripening was confirmed on the bases of their genetic fingerprints. The flavour profiles of the experimental sausages produced by these probiotic or protective strains were similar with that produced by the commercial meat starter culture and commercial North European dry sausage recipe.

Screening of commercial meat starter cultures at low pH and in the presence of bile salts for potential probiotic use

The survival of lactic acid bacterial strains from eight meat starter cultures under conditions similar to those in the gastrointestinal tract was determined. The conditions in stomach were simulated by using pH 1–5 phosphate-buffered saline. The conditions in small intestine were simulated by using MRS broth over a pH range 4–7 and two bile salt concentrations (0.15% and 0.30%). The survival capacity at pH 3 was strain dependent. 0.30% bile salts were critical for screening bile salt tolerant strains at pH 6. Strains of Lactobacillus sake (RM10) and Pediococcus acidilactici (P2) had the best survival capacities under acidic conditions and at the higher concentration of bile salts.

Formation of amino acid ( l-leucine, l-phenylalanine) derived volatile flavour compounds by Moraxella phenylpyruvica and Staphylococcus xylosus in cured meat model systems

A bacterial strain isolated from Danish immersion curing brine, Moraxella phenylpyruvica 0100, and a commercial meat starter culture, Staphylococcus xylosus DD34, were tested for their ability to form characteristic volatile compounds in minimal medium with the added amino acid l-leucine or l-phenylalanine under different environmental conditions (pH 5.5 and 6.0; 0 and 210 ppm nitrate; pre-incubation with and without agitation) and compared with respect to their ability to form volatile compounds in cured meat extracts and vacuum-packed cured meat cuts. The characteristic cured meat aroma precursors/compounds 3-methylbutanal and 3-methylbutanol were found to be formed in cured meat extracts and vacuum-packed cured meat cuts inoculated with M. phenylpyruvica. These volatiles are most probably formed by metabolic conversion of the amino acid l-leucine by M. phenylpyruvica, as they were also produced in minimal media with added l-leucine inoculated with this organism. The characteristic l-phenylalanine derived compound, benzaldehyde, formed by M. phenylpyruvica in minimal medium in the presence of nitrate (210 ppm), was not produced in any noticeable amount in cured meat extracts or vacuum-packed cured meat inoculated with M. phenylpyruvica. In contrast, benzacetaldehyde, which has been described as a possible metabolic product of the microbial conversion of l-phenylalanine, was found to be a characteristic volatile compound formed in cured meat extracts and vacuum-packed cured meat inoculated with M. phenylpyruvica, indicating an alternative metabolic pathway for l-phenylalanine by this organism in a cured meat environment. Even though S. xylosus was able to form volatile compounds characteristic of cured meats (3-methylbutanal, 3-methylbutanol) in minimal media with added l-leucine, this bacterial strain seemed not to be able to produce these characteristic volatiles in the studied cured meat systems. The present data imply that M. phenylpyruvica, in particular, is a potential meat starter for ensuring superior flavour development in cured meat.

Antibiotic challenge of meat starter cultures and effects upon fermentations

The principal bacterial strains present in 10 different commercial meat starter cultures were isolated and identified. These 22 strains (pediococci, lactobacilli and staphylococci) were examined for their sensitivity to a group of 21 antibiotics in solid and liquid media. Minimum inhibitory concentrations (MIC) of antibiotics were calculated and a select group was used at 1 2 , 1,2 and 5 times their MIC in broth media amended by glucose, salt and nitrite addition to study effects upon fermentation rate by the reconstituted starter culture mixtures. Four antibiotics often used in clinical therapy of large domestic animals were used in meat fermentations at 28 °C to evaluate their ability to inhibit the fermentation process. Patterns of antibiotic susceptibility of the lactic acid bacteria were consistent with those seen for similar organisms isolated from different environments. Pediococcus pentosaceus and the lactobacilli were more resistant to antibiotic challenge than P.acidilactici. Staphylococci were most sensitive to the antibiotics tested. The lactic acid bacteria were resistant to sulfa drugs, vancomycin, dihydrostreptomycin and synergistin, were fairly resistant to carbadox, but showed substantial sensitivity to erythromycin, β-lactams, the tetracyclines, clindamycin, excenel, lincomycin, bacitracin, tylosin tartrate, and virginiamycin. Erythromycin, penicillin G, tylosin tartrate and excenel were evaluated for their ability to affect fermentation performance and growth of the mixed starter cultures in a dry sausage meat formulation. These antibiotics at concentrations ≥0.125μgg −1, ≥2 IUg −1, ≥0.5μgg −1 and ≥4μgg −1, respectively, negatively influenced fermentations. It is suggested that these concentrations may be used as targets for development of rapid tests for detection of residue levels that could inhibit starter culture performance in meat.

Staphylococcus carnosus bacteriophages isolated from salami factories in Germany and Italy

Two phages lysing strains of Staphylococcus carnosus, an organism used as a starter culture for salami production, were isolated from factories in Germany and Italy. Morphologically they show the C1 morphotype and are unrelated to the only other known Staph. carnosus phage. The phages were physiologically and morphologically similar but showed differences in their structural proteins and DNA restriction patterns. Their genomes consisted of linear double stranded DNA with a genome size of 19 kb. The phages lysed a wide range of Staph. carnosus strains from commercial meat starter cultures as well as the DSM type strain. Despite the presence of these phages, the products were normal from the point of view of colour, texture and flavour.

Use of MRSD medium and the hydrophobic grid membrane filter technique to differentiate between pediococci and lactobacilli in fermented meat and starter cultures

Modifications of MRS medium were made by incorporation of 0.1 M L-arginine-HCl, 0.0025% phenol red, 100 IU polymyxin B sulfate, by deletion of meat extract, use of only 1.2% (w/v) glucose and increase of Mn 2+ to 1000 ppm. In addition, adoption of the hydrophobic grid membrane filter (HGMF) system with 0.025% Fast Green FCF dye and adjustment of the agar medium to pH 5.5 gave MRSD (differential) medium. Incubation at 25°C anaerobically under N 2 or CO 2 followed by a post-growth staining procedure involving use of 0.4% (w/v) bromocresol purple yielded conditions under which pediococci colonies were blue whereas homo- and heterofermentative lactobacilli were green in color. Under these conditions, 7 pediococci, 16 lactobacilli, and 18 commercial meat starter cultures were successfully analyzed by plate count to yield a differential assessment of the lactobacilli and pediococci present without interference from the 9 other genera tested. Streptococcus lactis and Leuconostoc spp. produced blue and green colonies, respectively, at 25°C which might interference but these organisms are not present in significant numbers in fermented meats. Pediococcus parvulus and Streptococcus faecalis produced green and blue colonies, respectively, but their very poor growth at 25°C prevented their interference. Use of the developed MRSD medium was described for enumeration of both pediococci and lactobacilli in starter cultures and in fermenting dry sausages to enable documentation of starter culture performance.

Changes in the plasmid profile of Lactobacillus plantarum obtained from commercial meat starter cultures

The stability of plasmids in Lactobacillus plantarum used commercially as a starter culture in the production of dry sausage was studied. Individual isolates of one strain taken from the starter culture produced over a period of 10 years were examined, and certain changes in the plasmid profiles identified. From molecular sizing and restriction enzyme analysis it appeared that two of the six plasmids became fused over this period of time to give one new, larger plasmid. The other plasmids remained unchanged.

Effect of Bacteriophage on the Activity of Lactic Acid Starter Cultures Used in the Production of Fermented Sausage

ABSTRACTThe effects of phage fri, which was isolated from a commercial meat starter culture, on the growth of Lactobacillus plantarum and on pH development in broth culture were determined. The influence of this phage on pH development in laboratory sausages produced with the aid of four commercial starter cultures was also assessed. In the presence of a phage‐sensitive starter culture, phage fri inhibited the growth of the organism and prevented the development of low pH levels when grown in broth culture. In laboratory sausage, the phage‐sensitive, lactic‐acid starter cultures produced sufficient acid for an acceptable product in the presence of phage fri. Results suggested that product failure in the fermented meat industry due to phage infection would not be common.

Incidence of Nitrite-Depleting Lactic Acid Bacteria in Cured Meats and in Meat Starter Cultures

Lactic acid bacteria were isolated from commercial packages of chicken loaf, bologna, Thuringer sausage and summer sausage. The bacteria were identified. The ability of these isolates to deplete nitrite was assessed during growth studies in broth cultures. The Lactobacillus plantarum components of four commercial meat starter cultures were also studied. All of the starter cultures and 68% of the isolates caused 59 to 93% depletion of 200 μg of nitrite per ml of APT broth over 24 h at 30°C. Two mechanisms of nitrite depletion were observed: chemical depletion due to acid production during growth, and enzymatic depletion. To assess enzymatic depletion of nitrite, the pH was maintained at 6.2. Six isolates were found to deplete nitrite up to 100% within 24 h at 22°C due to enzymatic activity. The starter cultures possessed weak enzyme activity, depleting nitrite by 10 to 28% over 24 h.

Isolation and characterization of a Lactobacillus plantarum bacteriophage isolated from a meat starter culture*

Morphological characterization of a bacteriophage isolated from the Lactobacillus plantarum portion of a commercial meat starter culture showed that the isolate, phage fri, belonged to the Bradley group A bacteriophages. It had a regular six‐sided head (90 nm diameter), and a contractile tail (190 nm in length). Short tail fibres were observed at the distal end of the sheath. Fluorescent staining with acridine orange indicated that phage fri contained double‐stranded DNA. The resistance to high concentrations of either chloroform or ether showed that its lipid content was negligible. Heat lability was demonstrated by inactivation of a phage fri population within 10 min at 60°C and within 5 min at 70°C. It tolerated pH levels of 3.0–8.0 and exhibited greater stability in the acid region than did its host strain. The latent and rise periods were both 75 min, and the average burst size 200 pfu/cell. Sensitivity was limited to the Lact. plantarum strain of only one manufacturer of the commercial meat starters investigated.