Control of the bacteriological condition of calf brain. I. Impact of improving hygiene

Sixty calves of the Dutch Friesian (FH) breed were stunned mechanically. Without previously having been stunned, another 30 calves were stuck according to the Jewish rite. Upon opening of the skulls (1–2 h post mortem) brains of mechanically stunned calves were collected either conventionally (n = 30) or ‘hygienically’ (n = 30), i.e. using a fresh pair of surgical gloves during each removal to avoid cross contamination. For ritually slaughtered animals only the hygienic procedure was followed. Samples of 10 g were excised from undamaged hemispheres and in the mechanically stunned treatment group also from the site of impact of the captive bolt. After storage in polystyrene trays at 3 ± 1°C for 7 days sampling was repeated. Bacteriological examination included the assessment of aerobic colony counts at 30°C for 3 days (ACC-30) and 4°C for 14 days (ACC-4) and Enterobacteriaceae colony counts at 37°C for 20 h (ECC). In conventionally collected samples the ACC-30 and ACC-4 were 3.8 and 3.0 log₁₀ cfu g^?1 at day 1 and 6.2 and 6.4 log₁₀ cfu g^?1 at day 8. With hygienic collection these counts were reduced by approximately 1 log unit. Whilst by conventional practice the ECCs, at day 1 and 8 were 2.6 and 4.8 log₁₀ cfu g^?1 these counts were 1.8 and 2.6 log₁₀ cfu g^?1 for hygienic practice. In samples excised from the site of impact of the captive bolt the hygienic procedure had similar, though less marked effects. On day 1 brains from ritually slaughtered animals had a bacteriological contamination similar to that found in the hemispheres of mechanically stunned calves. However, whilst at day 8 their mean ECCs were 3.4 and 3.5 log₁₀ cfu g^?1 the percentages of plates ‘positive’ for Enterobacteriaceae were only 10% in the ritually vs. 53% in the mechanically stunned group. The Enterobacteriaceae in this case were composed of psychrotrophic non-pathogenic genera of environmental origin. Salmonella was not isolated from any sample.     

Effects of Gellan-Based Edible Coating on the Quality of Fresh-Cut Pineapple During Cold Storage

The effects of gellan-based [gellan gum 0.56 % (w/v), glycerol 0.89 % (w/v) and sunflower oil 0.025 % (w/v)] edible coating on the respiration rate, physico-chemical properties and microbiological and sensory quality of fresh-cut pineapple during 16 days of storage (5?±?1 °C, 85?±?10 % RH) were evaluated. Uncoated fresh-cut pineapple was stored under the same condition and served as the control. For cross-linking reaction which was necessary for gel formation of gellan gum, a 2 % (w/v) calcium chloride solution that contained 1 % (w/v) ascorbic acid and 1 % (w/v) citric acid (as antibrowning agents) was used. The results obtained show that the respiration rate and weight loss of gellan-based coated samples were significantly (p?<?0.05) lower than those of the uncoated samples during 16 days of storage at 5 °C. In addition, coated samples significantly (p?<?0.05) maintained the firmness and colour of fresh-cut pineapple during low-temperature storage as compared to uncoated samples. The results obtained in this study also indicate that pH, titratable acidity and total soluble solids of coated and uncoated samples showed little changes during 16 days of storage at 5 °C. Gellan-based formulation did not show any antimicrobial effect, and no significant (p?>?0.05) differences were found among total plate counts and yeast and mould counts for coated and uncoated samples. Total plate counts and yeast and mould counts for coated and uncoated samples reached 10⁶ CFU/g (limit of shelf life acceptance for fruit-based products recommended by the Institute of Food Science and Technology in the UK) after 12 days of storage at 5 °C. In addition, the scores for all sensory characteristics at day 12 were significantly (p?<?0.05) higher in coated samples as compared to control. Therefore, the results obtained in this study indicate that gellan-based edible coating formulation has the potential to maintain the quality of fresh-cut pineapple during low-temperature storage for about 12 days.     

Changes in Chemical and Microbial Qualities of Dried Apricots Containing Sulphur Dioxide at Different Levels During Storage

Effects of different sulphur dioxide (SO₂) concentrations (188, 452, 791, 1,034, 1,236, 2,899 and 3,864 mg SO₂ kg^?1) and storage temperatures (5, 10, 20 and 30 °C) on the physical, chemical and microbial qualities of sulphited-dried apricots (SDAs) were evaluated. Analysis of kinetic data suggested first-order models for losses of moisture and SO₂ and formation of brown colour. Strong correlations were found between SO₂ concentrations and moisture loss constants (r?=??0.943), and brown colour values (r?=?0.949). β-carotene contents in SDA samples ranged from 26.6 to 36.2 mg 100 g^?1 dry weight, depending on SO₂ content of dried apricots. The SO₂ concentration over 791 mg per kg of dried apricots effectively protected carotenoids in dried apricots during drying. While storage times had significant effect on β-carotene contents, storage temperatures did not have such effects. The number of total mesophilic aerobic bacteria in all SDA samples ranged from 8.20?×?10¹ to 1.84?×?10² CFU g^?1. The number of total psychrophilic aerobic bacteria, lactic acid bacteria, yeast and mould, xerophilic mould, Staphylococcus spp. and total Enterobacteriaceae were below the detection limits (<4 CFU g^?1) in samples containing SO₂ even at the lowest level (188 mg SO₂ kg^–1) throughout the storage. Regardless of SO₂ concentration in dried apricots, low storage temperatures (below 20 °C) should be preferred to prevent the characteristic golden yellow colours of dried apricots.     

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.     

Microbial growth in vacuum packaged frankfurters produced in Spain

The effects of storage temperature and time on the microflora of vacuum packed frankfurters were analysed. Total aerobic counts, lactic acid bacteria, Brochothrix thermosphacta and yeast and moulds, were determined as functions of time. Statistically significant differences were observed (P ≤0·001) amongst the counts obtained at 2 and 7°C. At the end of the controlled storage period (42 days) the sausages kept at 7°C showed signs of spoilage. The appearance of superficial slime occurred after 28 days in samples with lactic acid bacteria at counts higher than 10⁸ cfu g⁻¹. The swelling of the pack showed after 42 days in those samples which had a level higher than 5 × 10⁸ cfu g⁻¹. On the contrary, the samples kept at 2°C did not show the aforesaid spoilage signs during the period of controlled storage. Basing our conclusions on the results obtained, a period of shelf life of 28 days was established at 7°C, whilst at 2°C a minimum shelf life of 42 days was obtained.     

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.     

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 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     

Behavior and incidence of Vibro parahaemolyticus in Sydney rock oysters (Crassostrea commercialis)

Vibrio parahaemolyticus grew poorly or not at all during storage of unopened Sydney rock oysters (Crassostrea commercialis) at 15 and 30°C for 2 and 7 days. Although V. parahaemolyticus counts often increased at 30°C, counts above 10⁴/g were not observed. Escherichia coli counts did not usually change substantially under these conditions. V. parahaemolyticus grew more readily during storage of unopened oysters under more severe conditions, with counts approaching or exceeding 10⁶/g after continuous or intermittent storage at 37°C. Opened oysters provided a much more favourable environment than unopened oysters for growth of V. parahaemolyticus. Growth occurred at 15, 30 and 37°C, with counts > 10⁶/g after overnight storage at 30 or 37°C. A survey of 30 market samples of oysters was conducted. Sixteen samples of unopened oysters were collected at the wholesale level and 14 samples of refrigerated opened oysters were purchased from retailers. V. parahaemolyticus was present in all samples of unopened oysters (range 0.4/g?2.3 × 10⁴/g) and in 13 samples of opened oysters (range 4.3/g? > 1.1 × 10³/g).     

Incidence of Penicillium roqueforti and roquefortine C in silages

Wilted grass and whole-crop maize silages taken from farm silos in northern Germany were analysed for fermentation pattern, mould counts and composition of mycoflora as well as for roquefortine C. In general, increasing DM contents of visibly unmoulded silages resulted in decreasing amounts of volatile fatty acids and a greater portion of samples with a high number of mould propagules. The average mould count of these silages was found to be 1·4×10⁴ cfu g⁻¹, whereas visibly moulded samples contained about 1×10⁸ cfu g⁻¹. Penicillium roqueforti was the predominating fungal species in silages occasionally accompanied by species of the genera Aspergillus, Mucor, Monascus and/or Geotrichum. Penicillium roqueforti was detected in 89% of the visibly moulded and in 85% of the visibly unmoulded samples. Of 24 visibly moulded silages tested, 21 samples contained roquefortine C, a mycotoxin known to be produced by P roqueforti. The highest level of roquefortine C found was 36 mg kg⁻¹ DM. Even 6 of 24 visibly unmoulded samples analysed for this mycotoxin were contaminated with roquefortine C but only in trace amounts. Roquefortine C is considered as a model compound for the biosynthesis of toxic fungal metabolites produced by P roqueforti in silages. The P roqueforti-count can be employed as a criterion to predict the contamination of silages with mycotoxins produced by this fungal species. © 1998 SCI.     

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.     

Quality of fresh‐cut purple‐fleshed sweet potatoes after X‐ray irradiation treatment and refrigerated storage

The effect of X‐ray irradiation on the quality of fresh‐cut, refrigerated purple‐fleshed sweet potato (PFSP) cubes was investigated. Packaged sweet potato cubes were treated with 0, 250, 500, 750 or 1000 Gy X‐ray irradiation and stored at 4 ± 1 °C for 14 days. After 14 days, total aerobic bacteria counts were 4.1 and 3.2 log₁₀ CFU g^?1, and mould–yeast counts were 3.3 and 3.0 log₁₀ CFU g^?1 in 750 and 1000 Gy treated samples, respectively. Doses up to 1000 Gy did not affect the firmness, moisture content and anthocyanin content of PFSP cubes throughout storage. PFSP cubes' flesh colour did not change during the first week of storage, but lightness (L*) increased after 14 days. Also, irradiation doses at 750 and 1000 Gy decreased saturation (C*) significantly, producing duller flesh colour than controls. Results indicate that X‐ray irradiation treatment at doses up to 1000 Gy can reduce microbial populations while maintaining the physical quality and anthocyanin content of PFSP cubes up to 14 days of storage.     

Direct Determination of Trace Elements in Meat Samples via High-Resolution Graphite Furnace Atomic Absorption Spectrometry

This work presents a direct and straightforward approach for the determination of trace elements in fish muscle, oyster, and bovine liver via direct solid sample analysis (SS) using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). The preliminary studies revealed the presence of spectral interferences at the analytical line of Ni at 231.096 nm, which could be corrected subtracting the spectrum of SiO and PO from the sample spectra using least-squares background correction. Moreover, all meat samples were proven homogeneous according to the homogeneity factor (H _e) (all values were <10 mg^½). Pyrolysis (Tp) and atomization (Ta) temperatures were studied and optimized as 800 °C (Tp) and 2500 °C (Ta) for Mn, 700 °C (Tp) and 2600 °C (Ta) for Ni, and 600 °C (Tp) and 2500 °C (Ta) for Rb. Calibration against aqueous standards was proven feasible for Mn determination, whereas Ni and Rb required calibration against solid standards for their quantification. The detection limits achieved were demonstrated adequate for application to food analysis (0.005 μg g^?1 for Mn, 0.002 μg g^?1 for Ni, and 0.1 μg g^?1 for Rb). The developed method was successfully applied for the elemental analysis of fish muscle, oyster, and bovine liver and three certified reference materials, demonstrating good agreement with the certified values and with the reference technique at a 95 % statistical confidence level.     

Influence of storage temperature on the quality of beef liver; pH as a reliable indicator of beef liver spoilage

The development of the microbial flora specifically involved in the spoilage of sliced beef livers packaged and stored under aerobic conditions at 0 and 3 °C for 14 days was studied. Changes in the pH value of the product were also determined. The possibility that pH value could be considered as a quick and reliable indicator of incipient spoilage was particularly considered. All microbial groups (except micrococci) showed differences in their rates of growth between 0 and 3 °C. Pseudomonads and lactic acid bacteria were the main components of the spoilage flora. When the 37 °C aerobic plate counts (APCs) reached 10⁵–10⁶ CFU g⁻¹ and the 20 °C APCs and pseudomonad counts reached 10⁶–10⁷ CFU g⁻¹, visible surface colonies (VSCs) were observed. The presence of VSCs is the most important criterion to determine organoleptic beef liver spoilage and has hence enabled us to establish a shelf-life of up to 8–10 and 5.5–6.5 days for samples stored at 0 and 3 °C respectively. Our study shows that the determination of pH, which is simple, economical and rapid, is capable of giving a reliable estimate of the spoilage status of beef livers. pH values lower than 6.15 may be considered as indicative of beef liver spoilage. © 1999 Society of Chemical Industry     

An evaluation of the effect of catalase and 3,3-thiodipropionic acid on the recovery of freeze-injured coliform bacteria

Coliform bacteria isolated from ground beef were frozen in 0.1 M phosphate buffer at ?18°C for 72 h. Before and after freezing, colony counts were made in tryptic soy agar (TSA) (Difco) and in TSA supplemented with 680 units of catalase ml^? and 1% 3,3-thiodipropionic acid (TDPA), respectively. The two H₂O₂ scavengers exerted no enhancing effect on cell recovery in the non-selective medium.Catalase and TDPA were also added to the TSA bottom layer in the selective dual-plating repair detection procedure described by Ray and Speck [(1978) Appl. Environ. Microbiol. 35, 883–885] using violet red bile agar (VRBA) as the selective medium. After freezing, approximately 70% of surviving cells could be recovered using TSA and TSA supplemented with catalase or TDPA (TSAC, TSAT).A total of 19 samples of various frozen food products (ice cream, pastries, ground meat and vegetables) were examined for coliform bacteria by the repair detection procedure with unsupplemented TSA and TSA with catalase or TDPA. Coliforms were detected in 15 samples. The logarithmic mean colony count with the TSA/VRBA procedure was 1350 g^?1. With TSAC/VRBA and TSAT/VRBA the counts were 1590 and 1400 g^?, respectively. These counts did not differ significantly from those obtained with unsupplemented TSA/VRBA (P>0.05).     

Microbiology of Indian and Mestizo pozol fermentations

Pozol is a beverage prepared from fermented nixtamal consumed in Southeastern Mexico. The Mestizos have modified the traditional Indian procedure by adding an extra cooking step to reduce the amount of solid sediment present in the beverage when the dough is suspended in water. To elucidate whether this additional step influences the microbiology of the fermentation, the microbiota before fermentation of Indian and Mestizo nixtamal doughs, and the microbial growth during both processes were assessed. The initial microbiotas of freshly made nixtamal doughs purchased on nine successive days from one Indian producer and one Mestizo producer were examined. The numbers of micro-organisms in the initial doughs were quite constant day by day and were similar in the Indian and Mestizo products. Initial microbial concentrations (cfu g⁻¹) were: lactic acid bacteria, 10⁵–10⁶; non-lactic aerobic mesophilic bacteria, 10⁴–10⁶, enterobacteria, 10³–10⁴; mould propagules, 10²–10³and yeasts, 10⁴. In the products fermented at 28°C for 48 h the concentrations of lactic acid bacteria and non-lactic aerobic mesophilic bacteria were 10⁹and 10⁵cfu g⁻¹respectively. No differences were found in the initial microbiotas nor in the fermentation patterns of both kinds of doughs. The concentrations of bacteria were similar on the surface and in the interior of the balls, but those of moulds and yeasts were higher on the surface than in the interior. In spite of the low pH values attained (4·5 or below), viable enterobacteria were still present at the end of the fermentation.     

Gamma irradiation as a means to eliminate Listeria monocytogenes from frozen chicken meat

Cells of Listeria monocytogenes ATCC 35152 were sensitive to gamma irradiation in phosphate buffer, pH 7.00 (D₁₀, dose required for 10% survival—0.15 kGy) at 0–5°C. The cells showed higher radiation survival when irradiated under frozen condition, with a D₁₀ of 0.3 kGy. The protection offered by shrimp/chicken/kheema homogenates (100 g litre^?1) was evidenced by even higher D₁₀ values (0.5 kGy) at both 0–5°C and cryogenic temperature. Boneless chicken meat samples were artificially inoculated with L monocytogenes ATCC 35152 cells at low (5 × 10³) colony-forming unit (cfu) g^?1 and high (5 × 10⁶ cfu g^?1) concentrations and irradiated at 1, 3, 4, 6 kGy doses under cryogenic conditions. The efficacy of the radiation process was evaluated by detecting L monocytogenes during storage at 2–4°C in the irradiated samples. These studies, when repeated with three other serotypes of L monocytogenes, clearly suggested the need for a dose of 3 kGy for elimination of 10³ cfu cells of L monocytogenes g^?1 from air-packed frozen chicken meat.     

Characterisation of proteolysis profile of Argentinean sheep cheeses made by two different production methods

BACKGROUND: In this work the proteolysis profiles of Argentinean sheep cheeses made by two different production methods were studied in order to develop products with typical and defined features. Cheeses with a starter of Streptococcus thermophilus, curd cut to corn grain size, washed and heated to 43 °C (S cheeses) and cheeses with a mixed starter of Streptococcus thermophilus, Lactobacillus helveticus and Lactobacillus bulgaricus, curd cut to rice grain size, unwashed and heated to 47 °C (L cheeses) were manufactured. The cheeses were ripened at 12 °C and 80% relative humidity for 180 days and samples were taken throughout this period. RESULTS: Gross composition and primary proteolysis were similar for both types of cheeses. Streptococci counts diminished from 10⁹ to 10⁷ colony‐forming units g^?1 during ripening in both S and L cheeses. Lactobacilli counts in L cheeses decreased during ripening and disappeared at 180 days. L cheeses had significantly lower pH values and showed higher peptidolysis than S cheeses. Triangle sensory evaluation indicated important differences between the two types of cheeses. CONCLUSION: S cheeses had a low proteolysis level and a soft flavour, making them appropriate for consumption after a short ripening time. L cheeses had a higher proteolysis level and more intense sensory characteristics, making them appropriate for consumption after a longer ripening time. Copyright © 2009 Society of Chemical Industry     

The effect of temperature on microbial growth in apple cubes packed in film and preserved by use of orange juice

Red delicious apple cubes were packed in fresh orange juice containing chemical preservatives (citric and ascorbic acid, potassium sorbate) and covered with plastic films of different gas permeabilities (polyethylene and EVA‐SARAN‐EVA) before storage at 4, 10 and 20 °C. The concentration of potassium sorbate in the product was optimized with respect to colour and microbial growth. Yeast and mould growth was modelled by Gompertz and linear equations to derive parameters such as lag phase, maximum microbial population and specific microbial growth or rates of decline. Activation energies for the specific growth rates were estimated from Arrhenius‐type equations and the time required to reach microbial counts of 10^6±0.2 CFU g^?1 was determined in all cases. At 4 °C, these values were longer than 25 days in all systems tested. The use of a low gas permeability film and an adequate potassium sorbate concentration extended storage life at higher temperatures.     

The effect of temperature abuse on Staphylococcus aureus and Salmonellae in raw beef and chicken substrates during frozen storage

Raw beef and chicken substrates inoculated with Staphylococcus aureus and two serotypes of Salmonella were subjected to severe temperature abuse at intervals during six months frozen storage at ?18°C. A method was developed for enumeration of freeze-damaged Salmonellae in a mixed population. After 24 h S. hadar in chicken at c 20 or 27°C, increased by 2·87 and 5·40 log cycles respectively. In beef, S. typhimurium increased by 1·80 and 2·93 log cycles. Refreezing thawed samples reduced the Salmonellae by up to 99%. Growth of St. aureus during thawing was generally slight in comparison but there was little change in viable counts on refreezing. Substantial growth of St. aureus occurred in chicken at 27°C. Some samples were assayed for staphylococcal enterotoxin A but this was not detected in samples containing St. aureus at c 10⁷ cfu.g^?1. Growth of natural saprophytes had caused obvious spoilage by 24 h of thawing.