Microbiological quality of fresh lettuce from organic and conventional production

Previously there was no available information on the levels of indicator bacteria and the prevalence of pathogens in fresh lettuce grown in organic and conventional farms in Spain. A total of 72 lettuce samples (18 farms for 4 repetitions each) for each type of the agriculture were examined in order to assess the bacteriological quality of the lettuces, in particular the prevalence of selected pathogens. The lettuce samples were analyzed for the presence of aerobic mesophilic, psychrotrophic microorganisms, yeasts and moulds, Enterobacteriaceae, mesophilic lactic acid bacteria, Pseudomonas spp. and presumptive Escherichia coli, Salmonella spp. and Listeria monocytogenes. The mean aerobic mesophilic counts (AM) were 6.35 ± 0.69 log₁₀ cfu g⁻¹ and 5.67 ± 0.80 log₁₀ cfu g⁻¹ from organic and conventional lettuce, respectively. The mean counts of psychrotrophic microorganisms were 5.82 ± 1.01 log₁₀ cfu g⁻¹ and 5.41 ± 0.92 log₁₀ cfu g⁻¹ from organic and conventional lettuce, respectively. Yeasts and moulds (YM) mean counts were 4.74 ± 0.83 log₁₀ cfu g⁻¹ and 4.21 ± 0.96 log₁₀ cfu g⁻¹ from organic and conventional lettuce, respectively. Lactic acid bacteria (LAB) were present in low numbers and the mean counts were 2.41 ± 1.10 log₁₀ cfu g⁻¹ and 1.99 ± 0.91 log₁₀ cfu g⁻¹ from organic and conventional lettuce, respectively. Pseudomonas spp. mean counts were 5.49 ± 1.37 log₁₀ cfu g⁻¹ and 4.98 ± 1.26 log₁₀ cfu g⁻¹ in organic and conventional lettuce, respectively. The mean counts for Enterobacteriaceae were 5.16 ± 1.01 log₁₀ cfu g⁻¹ and 3.80 ± 1.53 log₁₀ cfu g⁻¹ in organic and conventional lettuce, respectively. E. coli was detected in 22.2% (16 samples) of organic lettuce and in 12.5% (9 samples) of conventional lettuce. None of the lettuce samples was positive for E. coli O157:H7, L. monocytogenes and Salmonella spp. From the samples analyzed by principal component analysis (PCA) a pattern with two different groups (conventional and organic) can be observed, being the highest difference between both kinds of samples the Enterobacteriaceae count.     

Rapid Non-destructive Detection of Spoilage of Intact Chicken Breast Muscle Using Near-infrared and Fourier Transform Mid-infrared Spectroscopy and Multivariate Statistics

Near-infrared (NIR) transflectance and Fourier transform-infrared (FT-IR) attenuated total reflectance spectra of intact chicken breast muscle packed under aerobic conditions and stored at 4° for 14 days were collected and investigated for their potential use in rapid non-destructive detection of spoilage. Multiplicative scatter correction-transformed NIR and standard normal variate-transformed FT-IR spectra were analysed using principal component analysis (PCA), partial least-squares discriminant analysis (PLS2-DA) and outer product analysis (OPA). PCA and PLS2-DA regression failed to completely discriminate between days 0 and 4 samples (total viable count (TVC) days 0 and 4 = 5.23 and 6.75 log₁₀ cfu g⁻¹) which had bacterial loads smaller than the accepted levels (8 log₁₀ cfu g⁻¹) of sensory spoilage detection but classified correctly days 8 and 14 samples (TVC days 8 and 14 = 9.61 and 10.37 log₁₀ cfu g⁻¹). OPA performed on both NIR and FT-IR datasets revealed several correlations that highlight the effect of proteolysis in influencing the spectra. These correlations indicate that increase in free amino acids and peptides could be the main factor in the discrimination of intact chicken breast muscle. This investigation suggests that NIR and FT-IR spectroscopy can become useful, rapid, non-destructive tools for spoilage detection.     

Fingerprint of lactic acid bacteria population in beef carpaccio is influenced by storage process and seasonal changes

We have investigated the population structure of lactic acid bacteria (LAB) for several beef carpaccio available on the market with the purpose of comparing the effect of storage process (modified-atmosphere packaging and vacuum-packaging) and of seasonal changes on this microbial population. Out of 60 samples we have characterised 214 isolates accounting for 10 LAB species and 35 isolates accounting for 11 non-LAB species. Lactobacillus sakei, Leuconostoc carnosum and Leuconostoc mesenteroides were the most prevailing LAB species with a frequency of identification within 66%, 62% and 52% of the samples respectively. These 3 species were also characterised by a phenotypic intra-species diversity of isolates based on colony morphology. We showed that the prevalence was increased 1.5 fold for L. sakei and L. mesenteroides during the summer sampling in comparison to the spring or the fall sampling suggesting an environmental origin of these two species. Seasonal variations were also observed for the prevalence of Lactobacillus fuchuensis and L. carnosum in spring (2- and 1.5-fold increase, respectively) and of Brochothrix thermosphacta in fall (6-fold increase). Finally, we demonstrated that the growth potential after the sell-by-date was favourable of 1.25 log₁₀ cfu g⁻¹ to Leuconostoc spp. in modified-atmosphere packaging and of 1.38 log₁₀ cfu g⁻¹ to Lactobacillus spp. in vacuum-packaging. In conclusion, we show that important and unsuspected traits in bacterial population dynamics can be unravelled by large sampling strategies. We discuss about the need to take this assessment into account for further studies on bacterial ecosystems of meat.     

Technology-induced selection towards the spoilage microbiota of artisan-type cooked ham packed under modified atmosphere

The microbiota associated with a highly-perishable Belgian artisan-type cooked ham was analyzed through plating and (GTG)₅-fingerprinting of isolates throughout its processing chain. The raw tumbled meat was characterized by the presence of a versatile microbiota around 4.8 log(cfu g⁻¹), consisting of lactic acid bacteria, staphylococci, Brochothrix thermosphacta, Gram-negative bacteria, and yeasts. Pasteurisation of the ham logs reduced bacterial counts below 2 log(cfu g⁻¹) and subsequent manipulations selected for leuconostocs and carnobacteria. Also, B. thermosphacta and several Enterobacteriaceae were found at this stage. During storage in an intermediate high-care area for 2 days, a selection towards certain Enterobacteriaceae (Hafnia alvei, Enterobacter spp., and Pantoea agglomerans) and lactic acid bacteria (mainly vagococci and Streptococcus parauberis) was observed. B. thermosphacta, Leuconostoc carnosum and carnobacteria were also detected, but only after allowing bacterial outgrowth by incubating the meat logs at 7 °C for four weeks. After a mild post-pasteurisation process and subsequent handling, incubation of the meat logs at 7 °C for four weeks led to outgrowth of Enterobacteriaceae (mainly Enterobacter spp. and Serratia spp.). B. thermosphacta, and lactic acid bacteria (Enterococcus faecalis, Leuc. carnosum, and Carnobacterium maltaromaticum) were also found. After slicing and packaging under modified atmosphere, the microbiota of the refrigerated end-product consisted of leuconostocs, carnobacteria, and B. thermosphacta.     

Protective action of Lactobacillus curvatus CRL705 on vacuum-packaged raw beef. Effect on sensory and structural characteristics

Lactobacillus curvatus CRL705 was examined for its effectiveness as protective culture in the biopreservation of vacuum-packaged fresh beef stored during 60 days at 2 °C. For this purpose, L. curvatus CRL705, producer of lactocin 705 and lactocin AL705, was inoculated on the meat surface (10⁶ cfu g⁻¹). This microorganism became the dominating population throughout the storage period controlling the growth of Brochothrix thermosphacta and spoilage lactic acid bacteria naturally present on the meat. When the microstructural characteristics of the meat were evaluated using light microscopy, beef samples inoculated with the bioprotective culture showed a 10 days delay for the appearance of tissue degradation signs. Sensory analysis demonstrated that beef samples treated with L. curvatus CRL705 only developed an “acid” off-flavor after 60 days of refrigerated storage, and no undesirable off-odors were found. Therefore, inoculation with this bacteriocinogenic strain would provide an additional hurdle to improve storage life of refrigerated vacuum-packaged beef without affecting its sensory and structural characteristics.     

Lactic acid bacteria isolated from ethnic preserved meat products of the Western Himalayas

We used culture- and molecular-biology-based methods to investigate the diversity of lactic acid bacteria (LAB) in the ethnic chevon (goat) meat products chartayshya, jamma and arjia of the Western Himalayas. In six chartayshya, six jamma and four arjia samples, LAB were the predominant microbial component involved in the fermentation of these samples, and the total LAB population in arjia (7.8 ± 0.1 log cfu g⁻¹; mean ± SD) was significantly higher (P < 0.05) than in chartayshya (6.9 ± 0.1 log cfu g⁻¹) and jamma (7.5 ± 0.1 log cfu g⁻¹). We identified 53 LAB samples by 16S rRNA and phenylalanyl-tRNA synthase (pheS) genes sequencing. The LAB isolates were identified as Enterococcus durans, Enterococcus faecalis, Enterococcus faecium, Enterococcus hirae, Leuconostoc citreum, Leuconostoc mesenteroides, Pediococcus pentosaceus, and Weissella cibaria. These results revealed that there is a high level of diversity of LAB in the Himalayan ethnic preserved meat products.     

Viability of Lactobacillus acidophilus La-5 added solely or in co-culture with a yoghurt starter culture and implications on physico-chemical and related properties of Minas fresh cheese during storage

The effect of a probiotic culture of Lactobacillus acidophilus (La-5), added solely or in co-culture with a starter culture of Streptococcus thermophilus, on texture, proteolysis and related properties of Minas fresh cheese during storage at 5 °C was investigated. Three cheese-making trials were prepared and produced with no addition of cultures (T1 - control), supplemented with La-5 (T2), and with La-5 + S. thermophilus (T3). Viable counts of La-5 remained above 6.00 log cfu g⁻¹ during the whole storage for T2, reaching 7.00 log cfu g⁻¹ on the 14th day. For T3, the counts of La-5 remained above 6.00 log cfu g⁻¹ after 7 days of storage. Due to the presence of S. thermophilus, T3 presented the highest proteolytic index increase and titratable acidity values. Nevertheless, these results and S. thermophilus addition had no influence on viability of La-5 which presented satisfactory populations for a probiotic food. Moreover, the use of a yoghurt culture for the production of Minas fresh cheese T3 supplemented with La-5 resulted in a good quality product, with a small rate of post-acidification, indicating that traditional yoghurt culture could be employed in co-culture with La-5 to improve the quality of this cheese.     

The growth and survival of Escherichia coli O157:H7 on minced bison and pieces of bison meat stored at 5 and 10 °C

This study investigated the growth and survival of Escherichia coli O157:H7 on minced and whole pieces of bison meat. Growth curves of native microflora, including Pseudomonas spp. and Enterobacteriaceae were also generated. A marked E. coli O157:H7 strain was inoculated onto minced and whole pieces of bison meat at an initial level of 1.5 log₁₀ cfu g⁻¹. The inoculated meat was stored at either 5 °C for 28 days or 10 °C for 21 days. Survival, but no growth, of E. coli O157:H7 was observed on both forms of bison meat stored at 5 °C, while significant growth of the organism was observed at 10 °C. E. coli O157:H7 counts on whole pieces were generally higher than counts observed on minced bison meat, and reached their highest population by 14 days, with a total increase of 3.36 log₁₀ cfu g⁻¹ on whole pieces and 2.12 log₁₀ cfu g⁻¹on minced bison meat stored at 10 °C. Under the same storage temperature, Pseudomonas spp. and total counts displayed similar growth patterns on both pieces and minced bison meat, while the Enterobacteriaceae showed a slower growth rate. This study showed that the growth of E. coli O157:H7 on bison meat is similar to that observed in studies of beef.     

Possible role of volatile amines as quality-indicating metabolites in modified atmosphere-packaged chicken fillets: Correlation with microbiological and sensory attributes

The present work evaluated the possible role of volatile amines as indicator(s) of poultry meat spoilage. Fresh chicken meat (breast fillet) was packaged in four different atmospheres: air (A), vacuum (VP) and two modified atmospheres (MAs), namely M1, 30%/65%/5% (CO₂/N₂/O₂) and M2, 65%/30%/5% (CO₂/N₂/O₂). All chicken samples were kept under refrigeration (4 ± 0.5 °C) for a period of 15 days. Of the four treatments, the VP and M1 and M2 gas mixtures were the most effective for delaying the development of aerobic spoilage microbial flora. Pseudomonas spp. in chicken samples stored under M2 gas mixture and VP were significantly lower than all the other samples after 15 days of storage. Of the remaining bacterial species examined, lactic acid bacteria (LAB), Brochothrix thermosphacta, were dominant in the microbial association of both aerobically- and MA-packaged chicken, while yeasts contributed to a much lesser extent in the final microbial flora of chicken meat. On the basis of microbiological data (TVC), shelf-life extensions of 2, 4 and 9–10 days were achieved by VP and M1 and M2 gas mixtures. Results of the present work showed that the limit of sensory acceptability (a score of 6) was reached for the aerobically, vacuum-packaged and M1 gas mixture chicken samples approximately on days 6–7 and 9–10, respectively. Based on sensory (taste) analysis and with regard to chicken spoilage and freshness, TMA-N and TVB-N limit values of acceptability, namely 10.0 mg N/100 g and 40 mg N/100 g for chicken samples stored in air, may be proposed as the upper limit values for spoilage initiation of fresh chicken meat stored aerobically. Interestingly, the M2 gas mixture sample did not reach these limit values throughout the 15 day storage period. The formation of volatile amines during chill storage of chicken meat, under the packaging conditions examined in the present study, seemed to be in good agreement with the increase in microbiological count (TVC) and sensory taste score except for the M2 gas mixture.     

Microbiological and physicochemical properties of dry‐cured neck inoculated with probiotic of Bifidobacterium animalis ssp. lactis BB‐12

The effect of inoculum level of Bifidobacterium animalis ssp. lactis BB‐12 probiotic strain and ripening period on the quality of dry‐cured neck was studied. The microbiological parameters (Enterobacteriaceae, LAB and TVC) and physicochemical attributes (pH value, a_w, TBARS index, colour) were determined directly after fermentation at 15 °C for 3 weeks, after 6 and 12 months of ripening at 4 °C. The highest LAB count and a lower pH value were found in the meat inoculated with probiotic strain at 6.6 log cfu g^?1 (B2) followed by inoculation with probiotic strain at 6.3 log cfu g^?1 (B1). Level of inoculation had not had an influence on water activity, TBARS index and total colour parameters. Changes of fat oxidation during half‐year of ripening were limited in probiotic meat samples compared to naturally fermented control meat (C). Based on the results, it can be concluded that the most favourable physicochemical and microbiological parameters of the dry‐cured neck were obtained after 6 months of ripening. At that time, the Bifidobacterium BB‐12 at both levels is a good potential starter for meat fermentation.     

Behaviour of Listeria monocytogenes and Staphylococcus aureus in sliced,vacuum-packaged raw milk cheese stored at two different temperatures and time periods

The behaviour of Listeria monocytogenes and Staphylococcus aureus in raw milk cheese slices packaged under vacuum was evaluated. Artificially contaminated 80-day ripened cheese was portioned, vacuum packaged, and then stored for 28 days at 4 °C and for 56 days at 10 °C. Bacterial counts were obtained before vacuum packaging and then weekly during storage. At the end of ripening, the initial L. monocytogenes count was 4.46 ± 0.89 log cfu g⁻¹; weekly bacterial counts remained substantially unchanged in the samples stored at 4 °C but decreased to 3.54 ± 1.54 log cfu g⁻¹ in those stored at 10 °C. The initial S. aureus count before vacuum packaging was 3.60 ± 0.78 log cfu g⁻¹; it then gradually decreased to 2.60 ± 1.32 log cfu g⁻¹ in the samples stored at 4 °C and to about 1.9 log cfu g⁻¹ in those stored at 10 °C.     

Effect of nutrient supplements on growth and viability of Lactobacillus johnsonii NRRL B-2178 in whey

The main objectives of the paper were to study the effects of nutrient supplementation of cows' whey on the growth and viability of the probiotic microorganism Lactobacillus johnsonii NRRL B-2178. Because of the short lifespan of probiotics, this study was aimed at the evaluation of the contribution of nutrients in the improvement of growth and viability of the microorganism for the purpose of its further application in the formulation of whey-based beverages. A maximal cell growth of 8.70 log₁₀ cfu mL⁻¹ and viability of less than 5 days were achieved during the fermentation of whey supplemented with yeast extract (3.0%) and inulin (1.0%), including the synergistic effect of temperature 39 °C. Elimination of inulin from the fermentation process reduced the viable cell count by 0.2 log₁₀ cfu mL⁻¹, but the addition of 1.0% inulin after fermentation extended the viability of Lb. johnsonii NRRL B-2178 by 10 days.     

Inulin and oligofructose improve sensory quality and increase the probiotic viable count in potentially synbiotic petit-suisse cheese

The influence of inulin, oligofructose and oligosaccharides from honey, combined in different proportions, on the consumers’ sensory acceptance, probiotic viable count and fructan content of novel potentially synbiotic petit-suisse cheeses was investigated. Probiotic populations varied from 7.20 up to 7.69 log cfu g⁻¹ (Bifidobacterium animalis subsp. lactis) and from 6.08 up to 6.99 log cfu g⁻¹ (Lactobacillus acidophilus). The highest fructan contents were achieved by the cheese trials containing oligofructose and/or inulin (above 8.90 g 100 g⁻¹). The control trial showed the lowest mean acceptance (6.63) after 28 days of refrigerated storage, whereas the highest acceptance (7.43) was observed for the trial containing 10 g 100 g⁻¹ oligofructose. Acceptance increased significantly during storage (P<0.05) only for cheeses supplemented with oligofructose and/or inulin. Cheeses containing honey did not perform well enough compared to the cheeses with addition of inulin and/or oligofructose, and the best synbiotic petit-suisse cheese considering sensory and technological functional features was that containing oligofructose and inulin combined, therefore encouraging the commercial product use.     

Survival of Campylobacter jejuni on beef and pork under vacuum packaged and retail storage conditions: examination of the role of natural meat microflora on C. jejuni survival

The ability of Campylobacter jejuni ATCC 11168 to survive on beef and pork stored under chilled, vacuum packaged and retail display conditions were examined. In addition, the effect of natural microflora on commercial beef and pork on the survival of C. jejuni under these storage conditions was examined. When sterile cores of beef and pork were inoculated with ∼10⁵ to 10⁶ cfu cm⁻²C. jejuni, and were stored under aerobic or vacuum packaged conditions at −1.5 or 4 °C, its numbers dropped significantly and C. jejuni could not be enumerated by direct plating after 21 d of the 6 wks study. In contrast, survival of C. jejuni on commercial vacuum packaged beef and pork was significantly enhanced, resulting in only 1 log cfu cm⁻² reduction at the end of 6 wks. During 7 d of display in a retail case, numbers of C. jejuni dropped quickly, but could be enumerated by direct plating even after the 7 d. The presence of high numbers of inoculated C. jejuni on beef and pork had no significant effect on the natural microflora numbers compared to uninoculated controls when the meat was stored either in vacuum or in a retail display case. These results show that natural microflora on vacuum packaged meat afford enhanced survival of C. jejuni present on the surfaces of both beef and pork when stored at refrigeration temperatures. Hence, strict hygienic practices or the implementation of decontamination technologies are recommended to ensure safety of meat with respect to this pathogen.     

Assessment of the microbiological safety of dried spices and herbs from production and retail premises in the United Kingdom

A study of dried spices and herbs from retail and production premises to determine the microbiological status of such products was undertaken in the UK during 2004. According to EC Recommendation 2004/24/EC and European Spice Association specifications, 96% of 2833 retail samples and 92% of 132 production batches were of satisfactory/acceptable quality. Salmonella spp. were detected in 1.5% and 1.1% of dried spices and herbs sampled at production and retail, respectively. Overall, 3.0% of herbs and spices contained high counts of Bacillus cereus (1%, ≥10⁵ cfu g⁻¹), Clostridium perfringens (0.4%, ≥10³ cfu g⁻¹) and/or Escherichia coli (2.1%, ≥10² cfu g⁻¹). Ninety percent of samples examined were recorded as being ‘ready-to-use’, 96% of which were of satisfactory/acceptable quality. The potential public health risk of using spices and herbs as an addition to ready-to-eat foods that potentially undergo no further processing is therefore highlighted in this study. Prevention of microbial contamination in dried herbs and spices lies in the application of good hygiene practices during growing, harvesting and processing from farm to fork, and effective decontamination. In addition, the importance of correct food handling practices and usage of herbs and spices by end users cannot be overemphasised.     

Spoilage characteristics of Brochothrix thermosphacta and campestris in chilled vacuum packaged lamb,and their detection and identification by real time PCR

The spoilage potential of Brochothrix campestris and Brochothrix thermosphacta was investigated in vacuum-packed lamb. Striploins (n = 338) were inoculated and stored for twelve weeks at temperatures − 1.5, 0, 2 and 7 °C. Growth around 5–6 log₁₀ CFU/cm² was recorded after six weeks at 0, 2 and 7 °C, and ~ 3 log₁₀ CFU/cm² after nine weeks at − 1.5 °C. B. campestris was shown to cause spoilage by nine weeks at temperatures above 0 °C by the presence of green drip and unacceptable odours. Molecular based assays for the detection and differentiation of B. thermosphacta and B. campestris were developed and validated. A TaqMan assay was designed to target a unique single-nucleotide polymorphism in the Brochothrix 16 s rRNA gene with a sensitivity of < 7 CFU per reaction. Secondly a specific PCR was designed for B. campestris targeting the structural genes, brcA and brcB. These testing regimes offer a rapid and cost effective method for the detection and screening of Brochothrix species in meat products and processing environments.     

Efficacy of plant extracts in inhibitingAeromonas hydrophilaandListeria monocytogenesin refrigerated,cooked poultry

Alcohol extracts of angelica root, banana purée, bay, caraway seed, carrot root, clove (eugenol), marjoram, pimento leaf and thyme were applied to cooked chicken to determine their antimicrobial activities against Aeromonas hydrophilaand Listeria monocytogenes.Skinless chicken breast meat was cooked to an internal temperature of 85°C, allowed to cool to c. 5°C, then treated by surface application with plant extracts. Low (10 cfu g⁻¹)or high (10⁵ cfu g⁻¹)populations of A. hydrophilaand L. monocytogeneswere applied and samples were stored at either 5 or 15°C for up to 14 or 7 days, respectively. Eugenol and pimento extracts were most effective in inhibiting growth of both bacteria. A. hydrophilawas the more sensitive to the two treatments, with 4 log₁₀ cfu g⁻¹less growth occurring at 14 days at 5°C on eugenol-treated breast meat than on control samples. These results suggested that plant extracts might be useful as antimicrobials in cooked, ready-to-eat chicken meat.     

Identification and Quantification of Volatile Chemical Spoilage Indexes Associated with Bacterial Growth Dynamics in Aerobically Stored Chicken

Volatile organic compounds (VOCs) as chemical spoilage indexes (CSIs) of raw chicken breast stored aerobically at 4, 10, and 21 °C were identified and quantified using solid phase microextraction (SPME) combined with gas chromatography‐mass spectrometry (GC‐MS). The growth dynamics of total viable count (TVC), psychrotrophs, Pseudomonas spp., lactic acid bacteria (LAB), Brochothrix thermosphacta and H₂S producing bacteria were characterized based on maximum growth rates (μ_max), maximal microbial concentration (N_max) and at the moment of microbial shelf life (S_values), calculated from Gompertz‐fitted growth curves. Pseudomonas spp. was predominant species, while B. thermosphacta was characterized by the highest μ_max. The microbiological and sensory shelf lives were estimated based on TVC, Pseudomonas spp., and B. thermosphacta counts and sensory evaluation, respectively. Among 27 VOCs identified by GC‐MS in spoiled chicken samples, ethanol (EtOH), 1‐butanol‐3‐methyl (1But‐3M), and acetic acid (C₂) achieved the highest Pearson's correlation coefficients of 0.66, 0.61, and 0.59, respectively, with TVC, regardless of storage temperature. Partial least squares (PLS) regression revealed that the synthesis of 1But‐3M and C₂ was most likely induced by the metabolic activity of B. thermosphacta and LAB, while EtOH was attributed to Pseudomonas spp. The increase in concentration of selected volatile spoilage markers (EtOH, 1But‐3M, and C₂) in the headspace over spoiled chicken breast was found to be statistically significant (P < 0.05) with TVC growth. These findings highlight the possibility of analyzing the combination of 3 selected spoilage markers: EtOH, 1But‐3M, and C₂ as rapid evaluation for poultry quality testing using SPME‐GC‐MS.     

Microbial growth,communities and sensory characteristics of vacuum and modified atmosphere packaged lamb shoulders

Packaging fresh lamb in a vacuum (VAC) versus a 100% CO₂ modified atmosphere (MAP) may influence product shelf-life and the bacterial communities. While VAC is a common packing method and 100% CO₂ MAP is used in some countries, there is little information about how these different techniques affect the growth of spoilage bacteria and sensory attributes of lamb. The aim of this study was to assess changes in microbiological and organoleptic properties, and determine differences in microbial communities by terminal restriction fragment length polymorphism (TRFLP) and 454 pyrosequencing, in bone-in (BI) and bone-out (BO) MAP- and VAC-packed lamb shoulders stored at −0.3 °C over 12 wk. VAC and MAP lamb shoulders were acceptable in sensory test scores over 12 wk of storage at −0.3 °C, despite total viable count (TVC) and lactic acid bacteria (LAB) levels increasing to 8 log₁₀ CFU/cm² for VAC lamb and 4–6 log₁₀ CFU/cm² for MAP lamb. Similar to the sensory results, there were no significant differences in microbial communities between BI and BO product. However, types of bacteria were different between VAC and MAP packaging. Specifically, while VAC shoulder became dominated by Carnobacterium spp. in the middle of the storage period, the MAP shoulder microbial population remained similar from the start until later storage times.     

Microbiological and physicochemical quality of fresh-cut apple enriched with the probiotic strain Lactobacillus rhamnosus GG

The effectiveness as protective culture of the probiotic Lactobacillus rhamonosus GG (L. rham. GG) against Salmonella and Listeria monocytogenes on minimally-processed apples throughout storage as well as its effect on apple quality and natural microflora was evaluated. Survival to subsequent exposure to gastric stress was also reported. Apples were cut into wedges and dipped in a solution containing Salmonella and L. monocytogenes (10⁵ cfu mL⁻¹) and/or L. rham. GG (10⁸ cfu mL⁻¹). Apple wedges were packed and stored at 5 and 10 °C. Periodically, microbial population, bacterial survival to gastric stress and quality of apple wedges were evaluated. Although Salmonella was not affected by co-inoculation with L. rham. GG, L. monocytogenes population was 1-log units lower in the presence of L. rham. GG. L. rham. GG population maintained over recommended levels for probiotic action (10⁶ cfu g⁻¹) along storage, however, viable cells after gastric stress were only above this level during the first 14 days. Pathogen survival after gastric stress was <1% after 7 days at 5 °C. Moreover, apple wedges quality was not affected by L. rham. GG addition. Thus, L. rham. GG could be a suitable probiotic for minimally-processed apples capable to reduce L. monocytogenes growth; nevertheless shelf life should not be higher to 14 days to guarantee the probiotic effect.