Control of the bacteriological condition of calf brain. II. The effects of lactic acid decontamination and frozen storage

In two experiments the effects of lactic acid decontamination (LAD) and frozen storage on the bacteriological condition of calf brain were investigated. The first experiment incuded 80 calves, whose brains were extracted manually after splitting of the occipital bone with an axe. Upon removal, 40 brains were sprayed with 1.25% (v/v) L-lactic acid, whereas 40 brains remained untreated. At day 1 cone-shaped samples of 10 g were excised from 20 brains of each group at undamaged sites of the hemispheres and at the sites of impact of the captive bolt. After 7 days of storage at 3 ± 1°C in polystyrene trays the 20 remaining brains were sampled. The bacteriological examination included aerobic colony count at 30°C (ACC-30) and 4°C (ACC-4), mesophilic Enterobacteriaceae colony count (EC-37) and Lancefield group D streptococci colony count. For both locations and with regard to all parameters examined LAD resulted in significantly lower bacterial counts at day 1 as compared with controls. However, the differences were slight particularly at the damaged locations where a reduction in ACC-30 and ACC-4 of only 0.3 log g^?1 was effected. At day 8, bacterial counts were no longer significantly different, with the exception of ACC-4 at the site of impact of the captive bolt, which was 7.0 log g^?1 and 7.5 log g^?1 for treated and control brain respectively. Moreover, treated brain exhibited an unacceptable discolouration. From these findings it was concluded that lactic acid decontamination does not give an appreciable extension of the storage life of calf brain. The second experiment involved aseptically removed brains of 20 mechanically stunned calves. Ten brains were sampled at day 1, whereas brains of 10 other calves were stored at ?40°C for 7 days. Subsequent they were allowed to thaw for 1 day at 3 ± 1°C. At day 9 these brains had bacterial counts similar to those obtained at day 1. Thawing loss was somewhat higher (5.1%) than the weight loss of cooler-stored controls stored at 3 ± 1°C (1.2%). It is concluded that in view of the susceptibility of calf brain to bacterial spoilage, freezing should be taken into consideration as an effective means to prevent growth of bacteria that will lead to deterioration.     

Microbiological quality of retail fresh fish fillets in The Netherlands

A total of 242 samples of ready-for-sale fish fillets of validated good sensory quality was examined for colony counts at 20, 30 and 37°C, Enterobacteriaceae at 37°C, Escherichia coli, Salmonella and Vibrio parahaemolyticus in 10 g aliquots. Staphylococcus aureus and yeast and mould propagules. Gram negative pathogens were not detected in any sample. The following reference values were found attainable: colony counts at 30°C, 10⁶ g^?1; E. coli 10 g^?1; S. aereus 10² g^?1; yeast and mould propagules 10⁴ g^?1. These reference values include, as customary, a tolerance of about 20% of samples exceeding the stated levels without, however, reaching the next log₁₀ level.     

Characterization of Enterobacteriaceae strains isolated from spoiled dry-cured hams

Microbiological and physicochemical aspects of spoiled specimens of dry-cured hams affected by deep putrefaction were studied. Total aerobe (10³–10⁴cfu g⁻¹), Micrococcaceae(10⁴cfu g⁻¹) and lactic acid bacteria (<10²cfu g⁻¹) were present at the same levels as in unspoiled control hams. The overall hygienic quality of the hams was good, even when spoiled. Only Enterobacteriaceae counts (10²–10³cfu g⁻¹) were higher in spoiled dry-cured hams. pH (5·85–6·09) and A_w(0·888–0·909) were similar in spoiled and unspoiled hams. Thirty strains of the family Enterobacteriaceae were isolated and characterized. The strains were identified as Serratia liquefaciens and Proteus vulgaris. The strains of S. liquefaciens were slightly lipolytic, proteolytic, and psychrotrophic. Only two strains of this species were able to grow at an A_wlevel of 0·949. The strains of P. vulgaris were not lipolytic, were strongly proteolytic and only slightly psychrotrophic, and were able to grow at an A_wlevel of 0·949. None of them were able to grow at an A_wlevel of 0·929. The results indicate that the isolated strains could have caused deep putrefaction of dry-cured hams, growing during the first non-refrigerated steps of the curing process before the decrease of A_w. Enterobacteriaceae ought therefore to be considered a microbial quality-related hazard in the development of HACCP systems for dry-cured ham.     

A survey of microbial levels for incoming raw beef,environmental sources,and ground beef in a red meat processing plant

A microbial survey was performed for a midwestern red meat processing plant that produces retail cuts and ground beef. Samples were obtained from incoming ingredients, beef during processing, finished product, food contact and environmental surfaces, and the air. Aerobic plate count (APC), coliform count (CC), andEscherichia colicount (ECC) were determined for each sample. Product samples (25 g) were taken from beef carcasses, boxed beef, and ground beef. Swab samples (10 cm²) were obtained from food surfaces, food contact surfaces, floors, and walls. All samples were plated on aerobic plate count Petrifilm (for APC) andE. coliPetrifilm (for CC and ECC). Average log₁₀APC for product samples ranged from 3 cfu g⁻¹for retail cuts to nearly 7 cfu g⁻¹for boxed beef and the brisket and flank areas of beef carcasses. Average log₈APC for ground beef samples was 4.6 cfu g⁻¹. Average log₁₀CC for product samples ranged from 1.4–2.3 cfu g⁻¹. Highest CC was usually obtained from the brisket area of the beef carcass. Average log₁₀ECC ranged from <1–2 cfu g⁻¹and ECC was usually highest in finished ground beef. Average surface counts for log₁₀APC ranged from <1 cfu cm⁻²on sanitized processing equipment to 5 cfu cm⁻²on processing floors. Coliforms andE. coliwere rarely recovered from food contact surfaces or from food surfaces. Airborne log₁₀APC was generally low (0.6 cfu m⁻³), except for the carcass receiving area where counts were 2.4 cfu m⁻³. The most important factor contributing to source and level of microbial contamination for ground beef and retail cuts was from incoming raw materials obtained from different suppliers of beef. Microbial testing for beef products and the environment is an important tool for identifying and monitoring potential hazards as part of HACCP and GMP program development.     

Bacteriological quality of sheep meat in Mhow town of India

The purpose of this study was to investigate bacterial load in ready‐to‐sale sheep meat with special reference to Salmonella. Samples were collected from 100 sheep carcasses from retail meat shops in domestic markets. On carcasses, where bacterial counts were obtained, the mean of the log₁₀ aerobic plate count was 7.26 cfu g^?1, and that of total coliform count and total Escherichia coli count was 4.11 log₁₀ cfu g^?1 and 3.03 log₁₀ cfu g^?1, respectively. All the samples (100) were found positive for coliforms, 49.0% were positive for E. coli and 3.0% were positive for Salmonella. The isolates were serotyped as Salmonella infantis having antigenic structure 6, 7: r: 1, 5. Antibiogram revealed highest (100.0%) sensitivity towards amikacin, ceftriaxone, ciprofloxacin, chloramphenicol, colistin sulphate, gentamicin and nalidixic acid followed by cefuroxime and tetracycline (66.67% each) and cotrimoxazole (33.33%). All the strains were resistant to ampicillin.     

The fate of Escherichia coli O157 : H7 in Myzithra,Anthotyros, and Manouri whey cheeses during storage at 2 and 12°C

Myzithra, Anthotyros and Manouri whey cheeses were inoculated the day after production withEscherichia coli O157 : H7 at concentrations of approx. 1·8×10⁶cfu g⁻¹, and stored at 2 and 12°C for 30 and 20 days, respectively. The pH of the whey cheeses decreased from an initial value of approx. 6·20 to 5·83 or 5·60 (Myzithra) 5·75 or 5·20 (Anthotyros) and 5·80 or 5·30 (Manouri) by the end of the corresponding storage periods at 2 and 12°C, respectively. Escherichia coli O157 : H7 populations in the whey cheeses at the end of the 12°C storage period, had grown with an increase of approx. 1·3 log₁₀cfu g⁻¹. E. coli O157 : H7 populations in whey cheeses at the end of the 2°C storage period did not grow and decreased, with an approx. 2·5 log₁₀cfu g⁻¹reduction. Results showed that E. coli O157 : H7 can grow at 12°C and survive at 2°C storage in Myzithra, Anthotyros and Manouri whey cheeses, and therefore post-manufacturing contamination with this pathogen must be avoided by employing hygienic control programmes such as HACCP.     

Enterobacteriaceae in beef products from retail outlets in the Republic of Ireland and comparison of the presence and counts of E. coli O157:H7 in these products

This study investigated the prevalence and numbers of Enterobacteriaceae in minced beef and beef burgers purchased from supermarkets and butcher shops in the Republic of Ireland (RoI). Samples (n=1303) collected between June 2001 and April 2002 from every county in the RoI (∼60 per county) were examined for the presence of Enterobacteriaceae using method BS 5763. Overall, in the 43 beef products in which E. coli O157:H7 was present the Enterobacteriaceae counts ranged from 0.52 to 6.98 log₁₀ cfu g⁻¹. There was no correlation between the number of Enterobacteriaceae and the presence of E. coli O157:H7. There were no significant differences between Enterobacteriaceae numbers in fresh, unpackaged, minced beef samples from butcher shops and supermarkets, or in fresh, unpackaged, beef burgers from butcher shops and supermarkets. However, there were significant differences among the numbers of Enterobacteriaceae detected in different minced beef products. The numbers of Enterobacteriaceae in fresh, unpackaged, minced beef (6.54–6.98 log₁₀ cfu g⁻¹) were considerably higher than in preprepared or prepackaged minced beef (2.95–3.62 log₁₀ cfu g⁻¹).     

Microbiological Attributes of Turkish Butters Sold Under Market Conditions

In this study, microbiological quality of 45 butter samples sold under market conditions at Manisa (Turkey) was investigated. Total coliform, total fecal coliform, Escherichia coli and yeast and mould counts were found between < 1.0 – > 3.15 log₁₀ cfu.g^-1, < 1.0 – > 3.15 log₁₀ cfu.g^-1, < 1.0 – > 3.15 log₁₀ cfu.g^-1 and < 1.0 – > 6.62 log₁₀ cfu.g^-1 respectively. Only in one sample Salmonella was detected. Staphylococcus aureus was not detected in any of the samples. To that extent butters sold under market conditions in Manisa have high coliform, yeast and mould contamination.     

The hygienic condition of manufacturing beef destined for the manufacture of hamburger patties

The hygienic condition of the manufacturing beef collected at six carcass breaking plants for dispatch to hamburger patty manufacturing plants was examined. At each plant, 24×1kg samples of meat were selected at random from the product being collected into bulk containers. Total aerobic, coliform andEscherichia colicounts per gram were enumerated for each sample. The log mean (X) and standard deviation (s.d.) were calculated for the log₁₀values of each set of 24 counts, on the assumption that the distribution of counts approximated the log normal. A value for the log₁₀of the arithmetic mean (log A) was calculated for each set from the values for X and s.d. Log A values for total, coliform andE. colicounts ranged from 3.5 to 4.9, 0.7 to 3.0 and 0.2 to 2.6 log₁₀cfu g⁻¹, respectively. For each set of samples, there was a weak or no correlation between log₁₀values for total counts and those for coliforms orE. coli, but correlations between log₁₀values for coliform andE. colicounts ranged from non (R²=0.19) to close (R²=0.97). The results show that there are large differences between plants in the numbers ofE. coliin the manufacturing beef which they produce. The differences inE. colinumbers are not reliably reflected by differences between total or coliform counts in product from different plants. In addition, the findings indicate that manufacturing beef obtained from culled cow carcasses may generally be less heavily contaminated withE. colithan the trimmings obtained from the carcasses of feedlotted steers. Clearly, some current processes for the production of manufacturing beef destined for hamburger patty manufacture are poorly controlled with respect to minimizing the contamination of product withE. coliand, presumably, other faecal bacteria. The methods used in this study offer a means of objectively identifying such hygienically inadequate processes.     

Microflora of two varieties of sweet cherries: Burlat and Sweetheart

The epiphytic microflora of two widely cultivated sweet cherries ‘Burlat’ and ‘Sweetheart’ from Aragón (Spain), were characterized immediately after harvesting. Microbial analyses of total mesophilic aerobic, Enterobacteriaceae family and mould and yeast counts were carried out. Total mesophilic aerobic counts averaged 4·00 and 2·00 log cfu g⁻¹ for Burlat and Sweetheart cherries, respectively. The Enterobacteriaceae family was the microbial group with the lowest counts averaging 1·56 and 0·07 log cfu g⁻¹. Yeasts were the most prevalent micro-organisms in both varieties, with a mean of 4·10 and 2·30 log cfu g⁻¹ for Burlat and Sweetheart cherries. However, average mould counts slightly exceeded 2·00 log cfu g⁻¹. Statistical differences in microbial counts between the two varieties were detected. These results confirmed the lower susceptibility of Sweetheart cherries to microbial colonization and spoilage. Six hundred and seventy-nine strains, 103 belonging to the Enterobacteriaceae family, 100 mold strains and 442 yeast strains were isolated for the identification. Identification of Enterobacteriaceae species revealed that Pantoea agglomerans was the prevalent species in both varieties. Enterobacter cloacae and Serratia liquefaciens were also present on the Burlat cherry. Investigation of the external mycota led to three genera: Cladosporium, Alternaria and Penicillium. Yeasts were identified using the Deák and Beuchat simplified scheme (SIM) as belonging to five species included in three genera. Trichosporon pullulans was the dominant species, while Rhodotorula glutinis, Rhodotorula rubra, Cryptococcus albidus andCryptococcus neoformans were present at low numbers. Results of the yeast identification were compared with two commercially available kits, Api 20C AUX and PROLEAL. The PROLEAL values agreed with the SIM results; whereas the Api 20C AUX kit led to misidentifications in all strains tested.     

Microbiological Attributes of Turkish Butters Sold Under Market Conditions

In this study, microbiological quality of 45 butter samples sold under market conditions at Manisa (Turkey) was investigated. Total coliform, total fecal coliform, Escherichia coli and yeast and mould counts were found between < 1.0 – > 3.15 log₁₀ cfu.g^-1, < 1.0 – > 3.15 log₁₀ cfu.g^-1, < 1.0 – > 3.15 log₁₀ cfu.g^-1 and < 1.0 – > 6.62 log₁₀ cfu.g^-1 respectively. Only in one sample Salmonella was detected. Staphylococcus aureus was not detected in any of the samples. To that extent butters sold under market conditions in Manisa have high coliform, yeast and mould contamination. Received: April 29, 2008; received in revised form: May 28, 2008; accepted: June 3, 2008     

Microbiological quality of fresh fruit and vegetable products in Catalonia (Spain) using normalised plate‐counting methods and real time polymerase chain reaction (QPCR)

BACKGROUND: Commercially available fruits and raw and ready‐to‐eat vegetables (n = 445) were examined for aerobic, coliform, and yeast and mould counts using normalised methods. Listeria spp., Listeria monocytogenes and Salmonella spp. were detected by real time polymerase chain reaction (QPCR) after enrichment. RESULTS: Aerobic plate counts ranged from < 10 to > 10⁹ colony‐forming units (CFU) g^?1, with the lowest and highest counts recorded for fruits and sprouts respectively. The highest incidence level of coliforms was found in ready‐to‐eat vegetables, with up to 65.7% of samples containing from 5 to 9 log₁₀CFU g^?1. Yeasts and moulds showed their highest incidence level between 5 and 6 log₁₀ CFU g^?1, with an overall range from < 2 to 9 log₁₀ CFU g^?1. Salmonella spp., Listeria spp. and L. monocytogenes were detected in 0.67, 2.7 and 0.9% respectively of the total samples examined. CONCLUSION: The samples analysed can be gathered into two main groups, one showing low microbial counts (fruits) and a second group (raw whole leaves and roots and packed ready‐to‐eat vegetables) with higher microbial contamination. Although incidence levels of pathogenic bacteria reported here are in the lower range of those reported elsewhere, positive detections highlight the importance of good hygienic measures throughout the whole food chain. Copyright © 2007 Society of Chemical Industry     

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.     

Effectiveness of organic acid,ozonated water and chlorine dippings on microbial reduction and storage quality of fresh‐cut iceberg lettuce

BACKGROUND: The comparative effects of organic (citric and lactic) acids, ozone and chlorine on the microbiological population and quality parameters of fresh-cut lettuce during storage were evaluated. RESULTS: Dipping of lettuce in 100 mg L⁻¹ chlorine solution reduced the numbers of mesophilic and psychrotrophic bacteria and Enterobacteriaceae by 1.7, 2.0 and 1.6 log₁₀ colony-forming units (CFU) g⁻¹ respectively. Treatment of lettuce with citric (5 g L⁻¹) and lactic (5 mL L⁻¹) acid solutions and ozonated water (4 mg L⁻¹) reduced the populations of mesophilic and psychrotrophic bacteria by 1.7 and 1.5 log₁₀ CFU g⁻¹ respectively. Organic acid dippings resulted in lower mesophilic and psychrotrophic counts than ozonated water and chlorine dippings during 12 days of storage. Lactic acid dipping effectively reduced (by 2.2 log₁₀ CFU g⁻¹) and maintained low populations of Enterobacteriaceae on lettuce for the first 6 days of storage. No significant (P > 0.05) changes were observed in the texture and moisture content of lettuce samples dipped in chlorine, organic acids and ozonated water during storage. Colour, β-carotene and vitamin C values of fresh-cut iceberg lettuce did not change significantly (P > 0.05) until day 8. CONCLUSION: Lactic and citric acid and ozonated water dippings could be alternative treatments to chlorine dipping to prolong the shelf life of fresh-cut iceberg lettuce. Copyright © 2007 Society of Chemical Industry     

Bacillus cereus emetic toxin production in cooked rice

Three mesophilic strains of Bacillus cereus known to produce emetic toxin were used to model germination, growth and emetic toxin production in boiled rice cultures at incubation temperatures ranging from 8°C to 30°C. Minimum temperatures for germination and growth in boiled rice were found to be 15°C for all strains. Toxin production at 15°C was found to be significantly greater (P<0·01; reciprocal toxin titre of 373±124) than at 20°C and 30°C (reciprocal toxin titres 112±37 and 123±41, respectively). Toxin production became detectable after 48 h incubation at 15°C, with a maximum titre reached by 96 h. At 20°C and 30°C, toxin production was detected at 24 h incubation, with a maximum titre reached by 72 h. Toxin production at 15°C was detectable at lower bacterial counts (6·2 log₁₀ cfu g⁻¹), than with incubation at 20°C and 30°C (>7·0 log₁₀ cfu g⁻¹). In this study, the lower temperature limit for germination and growth on solid laboratory medium was found to be 12°C for all strains, i.e. 3°C lower than that observed in boiled rice.     

Changes in appearance and natural microflora on iceberg lettuce treated in warm,chlorinated water and then stored at refrigeration temperature

The objective of this study was to determine the effect of warm, chlorinated water on the survival and subsequent growth of naturally occurring microorganisms and visual quality of fresh-cut iceberg lettuce. After dipping cut lettuce leaves in water containing 20 mg l⁻¹free chlorine for 90 s at 50°C, samples were stored at 5 or 15°C for up to 18 or 7 days, respectively. Populations of aerobic mesophiles, psychrotrophs, Enterobacteriaceae, lactic acid bacteria, and yeasts and molds were determined. The visual appearance and development of brown discoloration were monitored. Treatment of lettuce in warm (50°C) chlorinated water delayed browning of lettuce. Shelf life of lettuce stored at 5°C, as determined by subjective evaluation of color and general appearance, was about 5 days longer than that of lettuce stored at 15°C. Treatment in warm (50°) water, with or without 20 mg l⁻¹chlorine, and in chlorinated water at 20°C significantly (α= 0·05) reduced the initial population of mesophilic aerobic microflora by 1·73–1·96 log₁₀cfu g⁻¹. Populations increased, regardless of treatment, as storage time at 5°C and 15°C increased. The same trends were observed in populations of psychrotrophs and Enterobacteriaceae. Yeast populations increased slightly in lettuce stored at 5°C but were consistently about 3 logs lower than mesophilic aerobes. Populations of molds and lactic acid bacteria were less than 2 log₁₀cfu g⁻¹throughout storage at 5 or 15°C. Results suggest that heat (50°C) treatment may have delayed browning and reduced initial populations of some groups of micro-organisms naturally occurring on iceberg lettuce, but enhanced microbial growth during subsequent storage.     

Aerobic bacterial, coliform, Escherichia coli and Staphylococcus aureus counts of raw and processed milk from selected smallholder dairy farms of Zimbabwe

A cross sectional study was conducted to enumerate total viable bacteria (TBC), coliforms, Escherichia coli and Staphylococcus aureus in raw (n = 120) and processed (n = 20) milk from individual farms from three smallholder dairy schemes of Zimbabwe between October, 2009 and February, 2010. Data on management factors were collected using a structured questionnaire. A standard pour plate technique was used to enumerate total viable bacteria, while for coliforms, E. coli and S. aureus, counts were assessed by the spread plate technique. The association of total viable bacterial counts and management factors was assessed using univariable and a linear regression model. The log₁₀ TBC for raw milk differed significantly (P < 0.05) amongst the schemes with the lowest (5.6 ± 4.7 log₁₀ cfu/ml) and highest (6.7 ± 5.8 log₁₀ cfu/ml) recorded from Marirangwe and Nharira respectively. The mean log₁₀ of TBC of processed milk (6.6 ± 6.0 log₁₀ cfu/ml) were marginally higher than those of raw milk (6.4 ± 5.6 log₁₀ cfu/ml) but not significant (P > 0.05). The coliform, E. coli and S. aureus counts for raw milk significantly differed (P < 0.05) amongst the study areas. The variation in TBC, coliforms, E. coli and S. aureus counts amongst the schemes could be attributed to differences in milking hygiene where farms with more access to training and monitoring of microbiological quality of milk had lower counts. Linear regression analysis revealed dairy scheme, delivery time and season of milking as independently associated with increased TBC of raw milk. The high TBC of raw and processed milk generally indicated low levels of milking hygienic practices, and high level of post-processing contamination, respectively. The high TBC, coliform, E. coli and S. aureus counts of both raw and processed milk may present a public health hazard. Thus, educating the farmers on general hygienic practices, quickening the delivery of milk to collection centres, or availing cooling facilities on-farm will improve the microbiological quality and safety of milk.     

Vacuum skin packaging and its effect on selected properties of beef and pork meat

Physicochemical, instrumental and microbiological examinations of steaks of beef and pork (m. longissimus lumborum) in vacuum skin packaging (VSP), conventional vacuum packing (CVP) and modified atmosphere packaging (MAP) were performed. Samples were stored at 2 ± 0.5 °C for 3 (pork) or 5 (beef) weeks. No statistically significant changes in pH values were recorded. Statistically significant (p < 0.001) changes in the thiobarbituric reactive substances content in modified atmosphere packed beef samples, and differences between samples in MAP and VSP or CVP were found from week 2 of the experiment onwards. The biggest changes in colour parameters were found in beef samples in MAP. The lowest and highest purge loss was recorded in samples in VSP and CVP, respectively. Vacuum packing enhanced the growth of lactic acid bacteria (LAB). At the end of the experiment, their numbers ranged from 4.31 log₁₀ cfu g^?1 (pork in CVP) to 5.14 log₁₀ cfu g^?1 (beef in VSP). LAB populations reached 2 log₁₀ cfu g^?1 in MAP beef and pork samples. On the other hand, MAP enabled the development of bacteria of the genus Pseudomonas and Brochothrix thermosphacta. The highest increase in coliform bacteria counts was recorded in vacuum-packed pork.     

Effects of plasma-activated water on microbial growth and storage quality of fresh-cut apple

Fresh-cut ‘Fuji’ apples were immersed for 5 min in plasma-activated water (PAW) generated, by plasma generated with sinusoidal voltages at 7.0 kHz with amplitudes of 6 kV, 8 kV, and 10 kV, designated PAW-6, PAW-8, and PAW-10, respectively. The control group was soaked in distilled water for 5 min instead of PAW. The results indicated that the growth of bacteria, molds, and yeasts was inhibited by PAW treatments during storage at 4 ± 1 °C, especially the microbial inactivation with PAW-8, which was the most efficient. PAW-8 reduced the microbial counts by 1.05 log₁₀CFU g⁻¹, 0.64 log₁₀CFU g⁻¹, 1.04 log₁₀CFU g⁻¹ and 0.86 log₁₀CFU g⁻¹ for aerobic bacteria (aerobic plate counts), molds, yeasts and coliforms on day 12, respectively. In addition, the bacterial counts of fresh-cut apples treated with PAW were <5 log₁₀CFU g⁻¹, which did not exceed to the existing China Shanghai local standard (DB 31/2012–2013) during 12 days of storage. PAW treatments reduced superficial browning of fresh-cut apples without affecting their firmness and titratable acidity. In addition, no significant change was observed in antioxidant content and radical scavenging activity between the PAW-treated and control groups. It is suggested that PAW is a promising method for preservation of fresh-cut fruits and vegetables, which is usually beneficial to the quality maintenance of fresh-cut fruits and vegetables during storage.     

Changes in the Microflora of Valdeteja Raw Goat's Milk Cheese throughout Manufacturing and Ripening

Changes in the microbiological flora of Valdeteja, a ripened home-made raw goat's milk cheese produced in northwest Spain, were studied during the manufacture and ripening processes using the spiral plating method. High counts of all microbial groups were observed in milk (7.66, 7.57, 6.13, 6.91, 2.47, 5.18, 3.27 and 3.85 log₁₀ cfu/g for aerobic mesophilic bacteria, lactococci, lactobacilli, leuconostocs, enterococci, Enterobacteriaceae,Micrococcaceae and moulds and yeasts, respectively). Counts increased between 0.76 and 1.96 log units from milk to curd. Lactic acid bacteria (lactococci, lactobacilli and leuconostocs) were the dominant microorganisms throughout ripening. Lactococci dominated over the lactobacilli up to day 27 of ripening. Leuconostocs were stable from day 2 of ripening. The final levels of typical enterococci were 3.62 log₁₀ cfu/g. Aerobic mesophilic bacteria, Enterobacteriaceae andMicrococcaceae reached their maximum in curd and decreased significantly throughout ripening. The decrease ofEnterobacteriaceae was very marked, although they did not completely disappear at the end of the ripening process (2.74 log₁₀ cfu/g). Moulds and yeasts counts increased significantly during ripening, giving final levels of 6.09 log₁₀ cfu/g. A strong correlation (P<0.001) was found between pH and lactobacilli (R=−0.87), leuconostocs (R=−0.82) and moulds and yeasts (R=−0.74) and between a_w and various microbial groups (e.g. EnterobacteriaceaeR=0.83).