Thermal inactivation of the frozen thawed traditional meat starter culture, Pediococcus pentosaceus, in a meat model system

The equation, y_(t) = y₍₀₎e^kt, was fitted (R = 0.9281, 0.9220 and 0.9117, respectively) to thermal inactivation data (55, 60 and 65 °C) of the traditional meat starter culture Pediococcus pentosaceus (10⁷ cfu/ml) in a meat model system. The population reduction constant (‘k’) increased (about 2.5- and 3-fold) with an increase in the treatment temperature (from 55 to 60 °C and from 60 to 65 °C, respectively). The Q₁₀ (55–65 °C) for ‘k’ was 7.63. Thermal treatments of 19.1, 9.0 and 3.1 min (55, 60 and 65 °C, respectively) reduced the population of P. pentosaceus by 2.0 logs. The value of ‘k’ and the duration of the thermal treatment played an important role in the extent of the inactivation of the culture. The “zero inactivation” temperature (T₀) for P. pentosaceus was 49.9 °C. About 5 logs of the culture would be destroyed at 63 and 68 °C within about 15.5 and 6.5 min, respectively.     

Prospects for new technology of meat processing in Japan

This review starts by introducing the history and underlying culture of meat production and consumption in Japan since early times, and the effects of social change on these parameters. Meat processing in Japan is described, and certain other related papers are also introduced. Automatic machines for meat cutting have been developed by the Japanese food industry and are currently being used throughout the world, particularly in Europe. Soft meat products specially produced for the elderly, along with diet meat products low in salt and calorie content for middle aged persons have recently gone into production. The intensification of color formation of meat using naturally occurring materials, and tenderization of sausage casing are discussed.     

生物技术在干酪加工中的应用

综述了生物技术在原料乳品质改进、凝乳酶、干酪发酵剂、干酪促熟、干酪包装及乳清处理等不同干酪加工环节中的应用.     

Study of the lactic acid bacteria throughout the manufacture of dry-cured lacón (a Spanish traditional meat product). Effect of some additives

Total aerobic mesophilic microflora (on SPC agar), lactic acid bacteria (on MRS agar) and lactobacilli (on Rogosa agar) were enumerated in samples from the surface and the interior of the pieces throughout the manufacture of six batches of lacón. Three of the batches were made without additives and three with additives (glucose (2 g/kg), sodium nitrite (E₂₅₀) (125 mg/kg), sodium nitrate (E₂₅₁) (175 mg/kg), sodium ascorbate (E₃₀₁) (500 mg/kg), and sodium citrate (E₃₃₁) (100 mg/kg)). The counts decreased throughout the manufacturing process, particularly after the salting stage. The use of additives did not affect the counts or the evolution of the microbial groups, except for the lactobacilli, which were present in higher numbers in the batches with additives.     

Identification of lactic acid bacteria isolated during traditional fura processing in Ghana

Fura is a millet-based spontaneously fermented dumpling produced and consumed in parts of West Africa, particularly Nigeria, Burkina Faso and Ghana. From eight traditional fura production sites in northern Ghana, 862 lactic acid bacteria were isolated and identified to species level using a combination of genotypic and phenotypic methods including (GTG)₅-based PCR fingerprinting and 16S rRNA gene sequencing, multiplex PCR by means of recA gene sequence comparison, conventional morphological characteristics and carbohydrate fermentation profiling. During millet dough fermentation, pH decreased from 5.6–6.4 to 4.1–3.7 and total lactic acid bacteria (LAB) counts increased from 4.4–5.3 to 7.9–9.2 log₁₀ (cfu/g). The initial stages of the fermentation were characterized by co-dominance of homo- and heterofermentative species of Pediococcus acidilactici, Weisella confusa, Lactobacillus fermentum, Lactobacillus reuteri, Lactobacillus salivarius, and Lactobacillus paraplantarum whereas L. fermentum was dominating at the end of the fermentation. L. fermentum was predominant in all fermentations (p < 0.05) and a high uniformity was observed among production sites regarding the dominance of L. fermentum. L. fermentum and W. confusa were isolated in all production sites and almost at all fermentation stages indicating that they are indigenous to traditional fura processing. The other LAB bacteria species which comprised a minor proportion of the total LAB occurred occasionally and in an irregular pattern among the production sites.     

Observations on the succession dynamics of lactic acid bacteria populations in chill-stored vacuum-packaged beef

Drip samples were collected at 4-week intervals from 10 vacuum-packaged beef striploins stored for 16 weeks at −1.5 °C and assayed for populations of lactic-acid bacteria (LAB), pH and spoilage-causing fermentation products. A total of 15 LAB species were identified using pulsed-field gel electrophoresis and biochemical analysis. A pattern of succession was observed during storage between strains of Carnobacterium, Lactobacillus, Leuconostoc and Pediococcus. Acetic acid production was associated with increasing LAB populations generally and butyric acid production was associated with the development of a particular strain of Leuconostoc. Changes in pH is postulated as a driver of succession.     

Evaluation of microbial dynamics during the ripening of a traditional Taiwanese naturally fermented ham

Isolation and identification of the autochthonous starter from a naturally fermented meat allows control of the fermentation process and promises microbiological safety for this specialty. Thus the purpose of this study was to identify the lactic acid bacteria and coagulase-negative cocci present in a traditional Taiwanese naturally fermented ham (TNFH) and to study the microbial dynamics at different ripening stages; the approach was a combination of conventional microbiological cultivation, polymerase chain reaction-denaturing gradient gel electrophoresis and DNA sequencing. In total, twelve different strains of lactic acid bacteria and three Staphylococcus strains were identified in the TNFH samples, whereas only 5 dominant strains were observed in the TNFH samples when the DGGE as a culture-independent method was applied. The bacterial ecology on the surface of the samples was mainly characterized by the stable presence of Lactobacillus sakei and Staphylococcus saprophyticus; nonetheless Leuconostoc mesenteroides and Carnobacterium divergens were the most abundant bacteria found in the final product. These results are also agreed with the findings of the culture-independent method. In addition, Microbacterium spp., Carnobacterium spp., Enterobacter spp., Brochothrix spp., Enterococcus spp., and Bacillus spp. were also present at the beginning of the ripening, but few bacteria were found at the center of the TNFH samples during the early ripening stages. However, after 30 days of ripening, the microbial ecology at the center of the TNFH samples paralleled that of the surface. Finally, as far as we have been able to determine, our report is the first to investigate the microbiological dynamics in fermented meat products using combination of cultivation, the Harrison disc method, DGGE and DNA sequencing as the culture-dependent method. Our report is also the first to show the presence of Staphylococcus arlettae in a fermented sausage and ham product.     

Evaluation of stored lamb bio-preserved using a three-strain cocktail of Lactobacillus sakei

Commercially prepared lamb was stored at −1.5 °C after inoculation with a combination of three Lactobacillus sakei strains previously shown to inhibit spoilage and pathogenic bacteria of importance to the meat industry. Between 6 and 14 weeks storage samples were evaluated for growth of inoculated strains, production of fermentation end-products and sensory acceptance of the cooked product. All three L. sakei strains flourished during storage, formed consistently dominant populations and were associated with lower surface pH and increased levels of lactic and acetic acids. Inoculated samples were determined to be as equally acceptable for smell, acidity, rancidity and overall liking as un-inoculated controls.     

Evaluation of three 2-thiobarbituric acid methods for the measurement of lipid oxidation in various meats and meat products

The aim of this work was to study the influence of different conditions on the 2-thiobarbituric acid (TBA) number, determined by the extraction and distillation method, as a measure of lipid oxidation in various meats and meat products. Different extracting agents (trichloroacetic acid and perchloric acid), different reaction times (20, 30, 40, 50 and 60 min) and the effect of sulfanilamide additions were evaluated. Significant differences with respect to reaction times were found. The best results were generally obtained with 40 min at 80 ± 2 °C. Different values were found between samples with and without the addition of sulfanilamide.     

Effect of a reactive oxygen species-generating system for control of airborne microorganisms in a meat-processing environment

The effectiveness of reactive oxygen species (ROS)-generating AirOcare equipment on the reduction of airborne bacteria in a meat-processing environment was determined. Serratia marcescens and lactic acid bacteria (Lactococcus lactis subsp. lactis and Lactobacillus plantarum) were used to artificially contaminate the air via a six-jet Collison nebulizer. Air in the meat-processing room was sampled immediately after aerosol generation and at various predetermined times at multiple locations by using a Staplex 6 stage air sampler. Approximately a 4-log reduction of the aerial S. marcescens population was observed within 2 h of treatment (P < 0.05) compared to a 1-log reduction in control samples. The S. marcescens populations reduced further by approximately 4.5 log after 24 h of exposure to ROS treatment. Approximately 3-log CFU/m3 reductions in lactic acid bacteria were observed following 2-h ROS exposure. Further ROS exposure reduced lactic acid bacteria in the air; however, the difference in their survival after 24 h of exposure was not significantly different from that observed with the control treatment. S. marcescens bacteria were more sensitive to ROS treatment than the lactic acid bacteria. These findings reveal that ROS treatment using the AirOcare unit significantly reduces airborne S. marcescens and lactic acid bacteria in meat-processing environments within 2 h.     

Evaluation of QTL for carcass merit and meat quality traits in a US commercial Duroc population

Putative quantitative trait loci (QTL) regions on 5 chromosomes (SSC3, 6, 12, 15, and 18) were selected from our previous genome scans of a Duroc×Pietrain F(2) resource population for further evaluation in a US commercial Duroc population (n=331). A total of 81 gene-specific single nucleotide polymorphism (SNP) markers were genotyped and 33 markers were segregating. The MDH1 SNP on SSC3 was associated with 45-min and ultimate pH (pHu), and pH decline. PRKAG3 on SSC15 was associated with pHu. The HSPG2 SNP on SSC6 was associated with marbling score and days to 113kg. Markers for NUP88 and FKBP10 on SSC12 were associated with 45-min pH and L*, respectively. The SSC15 marker SF3B1 was associated with L* and LMA, and the SSC18 marker ARF5 was associated with pHu and color score. These results in a commercial Duroc population showed a general consistency with our previous genome scan.     

Optimisation of a chromatographic procedure for determining biogenic amine concentrations in meat and meat products employing a cation-exchange column with a post-column system

The aim of this study was to optimise and validate a chromatographic method for determining biogenic amine (BA) in meat and meat products separated by a cation-exchange column with a post-column system, using o-phthalaldehyde as a derivatising reagent. A perfect separation of nine BA (tyramine, histamine, β-phenylethylamine, putrescine, cadaverine, tryptamine, agmatine, spermidine and spermine) was obtained in 22 min. The conditions were: column Tª 40 °C and coil Tª 45 °C, pump flow rate 0.8 mL/min, pH phase A 6.33, B 5.63 and C 13.00. The method was adjusted linearly in a range of 0.10–12 mg/L with a correlation coefficient superior to 0.998. Detection and quantification limits were between 0.03–0.10 mg/L and 0.10–0.20 mg/L, respectively. Precision studies were satisfactory, with RSD less than 2% and meat extracts recovering over 98%. This method showed an appropriate, precise, fast and versatile procedure for determining nine BA simultaneously in different meat product matrices.     

Development of a pentaplex PCR assay for the simultaneous detection of Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, L. delbrueckii subsp. lactis, L. helveticus, L. fermentum in whey starter for Grana Padano cheese

A pentaplex PCR assay for the rapid, selective and simultaneous detection of Lactobacillus helveticus, L. delbrueckii subsp. lactis, L. delbrueckii subsp. bulgaricus, Streptococcus thermophilus, and L. fermentum, was developed. The target sequences were a group of genes coding for beta-galactosidase production (S. thermophilus and L. delbrueckii subsp. bulgaricus), for cell-enveloped associated proteinase synthesis (L. helveticus), for dipeptide transport system production (L. delbrueckii subsp. lactis) and for arginine-ornithine antiporter protein production (L. fermentum). The analytical specificity of the assay was evaluated with 5 reference strains and 140 lactic acid bacterial strains derived from raw milk cheeses and belonging to the Lactobacillus, Streptococcus, Lactococcus and Enterococcus genera. The identification limit for each target strain was 10³ CFU/ml. This new molecular assay was used to investigate the LAB population by direct extraction of DNA from the 12 whey cultures for Grana Padano. The pentaplex PCR assay revealed a good correspondence with microbiological analyses and allowed to identify even minor LAB community members which, can be out-competed in vitro by numerically more abundant microbial species.     

Suitability of the TBA method for assessing lipid oxidation in a meat system with added phenolic-rich materials

Numerous protocols and modifications of the thiobarbituric acid (TBA) test are available in the literature. The present paper compares the effectiveness of different TBA tests in minimizing the interferences caused by the addition of phenolic-rich materials (wild fruits) as antioxidants in cooked burger patties. The aqueous acid extraction procedure (EM) and a modified distilation TBA method (DM) were tested with different conditions of incubation – boiling (B) vs. room temperature (RT) – for monitoring lipid oxidation in cooked burger patties during refrigerated storage. DM-B and DM-RT were more suitable than EM procedures for assessing TBA-reactive substances (TBA-RS) in meat samples containing compounds such as anthocyanins, with similar spectral properties than that of the TBA–malondialdehyde (MDA) adduct. Additionally, interferences caused by browning development during incubation were avoided by DM procedures or by performing RT incubations. Correlations between TBA-RS numbers and hexanal contents in cooked pork burger patties were calculated in order to corroborate the suitability of the tested TBA procedures. The DM-RT procedure showed the highest correlation with hexanal content (R² = 0.90; p < 0.001).     

Evaluation of culture media for enumeration of Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium animalis in the presence of Lactobacillus delbrueckii subsp bulgaricus and Streptococcus thermophilus

The study compared the growth capability of probiotic (Lactobacillus acidophilus La05, Lactobacillus casei Lc01 and Bifidobacterium animalis Bb12) and non-probiotic (Lactobacillus delbrueckii subsp bulgaricus and Streptococcus thermophilus) cultures on twenty-one culture media grouped according to selectivity: non-selective agars, selective agars without antibiotics and MRS agars containing different combinations of lithium chloride, cystein, bile salts and antibiotics. Four of these media were selected for quantitative enumeration of L. acidophilus La05, L. casei Lc01, and B. animalis Bb12. The best culture media and incubation conditions for enumeration of the probiotic cultures were: B. animalis: MRS agar with dicloxacillin, 37 °C or 42 °C, anaerobiosis; L. acidophilus: MRS agar with bile salts, 37 °C or 42 °C, aerobiosis; L. casei: MRS agar with lithium chloride and sodium propionate, 37 °C or 42 °C, aerobiosis or anaerobiosis. Plating on MRS with glucose replaced by maltose, 37 °C or 42 °C, anaerobiosis, will distinguish probiotic from non-probiotic cultures. For enumeration of each probiotic in a mixed culture, the following media and incubation conditions were recommended: B. animalis: 4ABC-MRS, 42 °C, anaerobiosis, L. acidophilus: LC medium, 42 °C, aerobiosis or anaerobiosis and L. casei: LP-MRS, 42 °C, aerobiosis or anaerobiosis. In all experiments, differences in counts using pour plating or surface plating were not significant (P ≤ 0.05).     

Hanseniaspora opuntiae, Saccharomyces cerevisiae, Lactobacillus fermentum, and Acetobacter pasteurianus predominate during well-performed Malaysian cocoa bean box fermentations,underlining the importance of these microbial species for a successful cocoa bean fermentation process

Two spontaneous Malaysian cocoa bean box fermentations (one farm, two plantation plots) were investigated. Physical parameters, microbial community dynamics, yeast and bacterial species diversity [mainly lactic acid bacteria (LAB) and acetic acid bacteria (AAB)], and metabolite kinetics were monitored, and chocolates were produced from the respective fermented dry cocoa beans. Similar microbial growth and metabolite profiles were obtained for the two fermentations. Low concentrations of citric acid were found in the fresh pulp, revealing low acidity of the raw material. The main end-products of the catabolism of the pulp substrates glucose, fructose, and citric acid by yeasts, LAB, and AAB were ethanol, lactic acid, acetic acid, and/or mannitol. Hanseniaspora opuntiae, Lactobacillus fermentum, and Acetobacter pasteurianus were the prevalent species of the two fermentations. Saccharomyces cerevisiae, Lactobacillus plantarum, Lactobacillus pentosus, and Acetobacter ghanensis were also found during the mid-phase of the fermentation processes. Leuconostoc pseudomesenteroides and Acetobacter senegalensis were among the prevailing species during the initial phase of the fermentations. Tatumella saanichensis and Enterobacter sp. were present in the beginning of the fermentations and they could be responsible for the degradation of citric acid and/or the production of gluconic acid and lactic acid, respectively. The presence of facultative heterofermentative LAB during the fermentations caused a high production of lactic acid. Finally, as these fermentations were carried out with high-quality raw material and were characterised by a restricted microbial species diversity, resulting in successfully fermented dry cocoa beans and good chocolates produced thereof, it is likely that the prevailing species H. opuntiae, S. cerevisiae, Lb. fermentum, and A. pasteurianus were responsible for it.     

Development and validation of an extensive growth and growth boundary model for psychrotolerant Lactobacillus spp. in seafood and meat products

A new and extensive growth and growth boundary model for psychrotolerant Lactobacillus spp. was developed and validated for processed and unprocessed products of seafood and meat. The new model was developed by refitting and expanding an existing cardinal parameter model for growth and the growth boundary of lactic acid bacteria (LAB) in processed seafood (O. Mejlholm and P. Dalgaard, J. Food Prot. 70. 2485–2497, 2007). Initially, to estimate values for the maximum specific growth rate at the reference temperature of 25 °C (μ_ref) and the theoretical minimum temperature that prevents growth of psychrotolerant LAB (T_min), the existing LAB model was refitted to data from experiments with seafood and meat products reported not to include nitrite or any of the four organic acids evaluated in the present study. Next, dimensionless terms modelling the antimicrobial effect of nitrite, and acetic, benzoic, citric and sorbic acids on growth of Lactobacillus sakei were added to the refitted model, together with minimum inhibitory concentrations determined for the five environmental parameters. The new model including the effect of 12 environmental parameters, as well as their interactive effects, was successfully validated using 229 growth rates (μ_max values) for psychrotolerant Lactobacillus spp. in seafood and meat products. Average bias and accuracy factor values of 1.08 and 1.27, respectively, were obtained when observed and predicted μ_max values of psychrotolerant Lactobacillus spp. were compared. Thus, on average μ_max values were only overestimated by 8%. The performance of the new model was equally good for seafood and meat products, and the importance of including the effect of acetic, benzoic, citric and sorbic acids and to a lesser extent nitrite in order to accurately predict growth of psychrotolerant Lactobacillus spp. was clearly demonstrated. The new model can be used to predict growth of psychrotolerant Lactobacillus spp. in seafood and meat products e.g. prediction of the time to a critical cell concentration of bacteria is considered useful for establishing the shelf life. In addition, the high number of environmental parameters included in the new model makes it flexible and suitable for product development as the effect of substituting one combination of preservatives with another can be predicted. In general, the performance of the new model was unacceptable for other types of LAB including Carnobacterium spp., Leuconostoc spp. and Weissella spp.     

Evaluation of a facile method of template DNA preparation for PCR-based detection and typing of lactic acid bacteria

The objective of our investigation was to develop a convenient and reliable method of generating template DNA for routine PCR-based detection and typing of lactic acid bacteria (LAB). Template DNA extracted from Lactobacillus, Lactococcus, Pediococcus and Leuconostoc using a combination of urea, SDS and NaOH yielded amplicons of expected size in PCR with genus-specific primers. Apart from LAB, the proposed method could also be adopted to generate PCR-compatible template DNA from a number of Gram-positive and Gram-negative bacterial strains. DNA template prepared by the proposed method from various standard strains of Lactobacillus sp. also generated discriminating fingerprints with BOXA1R primer in rep-PCR. A significant finding of the investigation was that a comparable banding profile of LAB strains was obtained in rep-PCR using template DNA prepared by urea–SDS–NaOH method and a commercially available DNA isolation kit. This was further evidenced by high dice coefficient values obtained in the range of 81.8–96.7 when cluster analysis was performed by UPGAMA method. The application potential of this DNA extraction method for PCR-based direct detection of LAB in fermented food samples such as dahi, idli batter and salt-fermented cucumber was validated by detecting specific amplicons of LAB genera in the fermented samples. The applicability of the proposed template DNA extraction method was further substantiated when 29 bacteriocinogenic LAB strains (Bac⁺) previously detected in salt-fermented cucumber by PCR [Singh, A.K., Ramesh, A., 2008. Succession of dominant and antagonistic lactic acid bacteria in fermented cucumber: Insights from a PCR-based approach. Food. Microbiol. 25, 278–287] generated differentiating fingerprints in BOX element based rep-PCR and formed clusters with reference LAB strains.