A gram-positive, nonfermentative, rod-shaped bacterium designated ST-5, identified as Rhodococcus, was isolated from Kuwait soil. Grown on hydrocarbon, such as kerosene and n-paraffin, the bacterium produced surface-active compounds (biosurfactants). Neasurements of surface tension, critical micelle dilution and emulsifying activity indicated that the biosurfactant is produced as a primary metabolite. The ST-5 culture surface-active component is mainly giycolipid in nature. Whole-culture broth dropped surface tension to values below 27 mN/m and was stable during exposure to high salinity (10% NaCI), elevated temperatures (120°C for 15 min) and a wide range of pH values. The culture broth was effective in recovering up to 86% of the residual oil from oil-saturated sand packs, indicating potential value in enhanced oil-recovery processes.
The effect of processing procedures and overall environmental and hygienic conditions on the microbiological quality and safety of chicken carcasses was studied in a modern processing plant on two separate days. The level of microorganisms on chicken carcasses was assessed by a neck-skin “maceration” method. Carcasses were heavily contaminated by different types of organisms, including indicator organisms (total aerobics, Enterobacteriaceae, coliforms and Escherichia coli) and pathogens (e.g., Salmonella, Campylobacter and Staphylococcus aureus). Microbial levels varied during processing, but the highest levels were detected after scalding and defeathering. Microbial levels did not change during vent opening or evisceration. Spray washing after evisceration did not reduce levels of bacteria. No substantial change occurred in bacteria levels during air-chilling, packaging and cold-storage; however, the finished product was heavily contaminated. In the freshly processed carcasses, mean counts (log colony forming units [CFU]/g neck-skin) of aerobic bacteria Enterobacteriaceae, coliforms, E. coli, Campylobacter and S. aureus were 6.6, 4.5, 4.1, 3.6, 5.2 and 2.7 on the first sampling day, and 6.5, 4.6, 4.9, 3.6,4.7 and 4.1 on the second day. Salmonella was present in all birds examined, including those coming directly from the farm. Major serotypes detected on dressed carcasses were Salmonella ohio, Salmonella enteritidis, Salmonella paratyphi and Salmonella krefeld.
The effect of modified atmosphere packaging (MAP) (70% CO2/30% N2; 30% CO2/70% N2) on the shelf‐life of fresh chicken carcasses stored at 2, 4, 7 and 9C was investigated. The shelf‐lives of MAP carcasses (70% CO2/30%N2) stored at 2, 4, 7 and 9C were 25, 21, 12 and 8 days, respectively compared with 7 days for air‐packaged ones stored at 4C; the shelf‐life of MAP carcasses (30% CO2/70%N2) stored at the same temperatures were 20, 15, 8 and 8 days, respectively. The inhibitory effect of MAP on the growth of Enterobacteriaceae and on the production of spoilage metabolites, such as free fatty acids and extract release volume, was negligible at higher temperatures (7 and 9C) and more pronounced at lower temperatures (2 and 4C), especially at higher concentrations of CO2 (70% CO2/30% N2). The occurrence and growth of organisms such as Escherichia coli, coliforms, Staphylococcus aureus, Salmonella and Campylobacter in carcasses stored at different temperatures were also documented.
The nutritional requirements and growth characteristics of a biosurfactant-producingRhodococcus bacterium isolated from Kuwaiti soil were determined. Maximum cell yields (6.6 g/l) and biosurfactant production were achieved with a medium containing 2% (v/v)n-paraffin as a carbon and energy source, 0.2% lactose broth, optimal concentrations of nitrogen (nitrate), phosphorus, iron, magnesium and sodium sources, and minimal concentrations of potassium and trace element sources. The optimal pH was 6.8 for surfactant production and optimal temperature was 37°C. The biosurfactant produced after 16 to 33 h growth in a 7 I fermenter decreased both surface tension and interfacial tension of culture broth to below 27 and 1.8 mN/m, respectively, and was effective at critical micelle dilutions of 10(-3). Data on biosurfactant biosynthesis suggest that the product is produced as a primary metabolite and, therefore, could be produced effectively under continuous fermentation conditions.
l%e effects of vacuum-packaging on the shelf-life of eviscerated broiler carcasses, under conditions simulating market storage (4, 7and 9C) in the State of Kuwait were studied. Vacuum-packaging increased the shelf-life of the carcasses by 7-8, 6 and 4 days beyond that of the conventionally-packaged carcasses, when stored at 4, 7 and 9C, respectively. l%e growth of the Enterobacteriaceae was lowest in carcasses stored at 4C, irrespective of the packaging type. Of the Enterobacteriaceae, the coliforms were the predominant microorganisms (-SO%), whereas Salmonella accounted for up to 15%. Lactobacillus were the predominant spoilage microorganisms in the vacuum-packaged carcasses, whereas Pseudomonas predominated in the conventionally-packaged ones. Vacuum-packaging can be recommended for improvement of the keeping quality of eviscerated broiler carcasses, but it should also be associated with strict procedures for controlling the handling andstorage temperatures throughout the overall distribution system, 'To whom correspondence should be addressed Tel: 4836100/4816007 Ext. 4331 Fax: 4846891 *Present address: Kamnarsv., 5D/316, 22646. Lund, Sweden Journal of Food Safety 13 (1993) 305-32 1. AZZ Rights Resewed. Topyright I993 by Food & Nutritian Press, Inc., Trumbull, Connecticur. 305 306 W. SAWAYA et al.
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