EFFECTS OF TRISODIUM PHOSPHATE ON POPULATIONS OF SALMONELLA TYPHIMURIUM AND SALMONELLA ENTERITIDIS IN VITRO

This study determined the bactericidal activity of different concentrations of trisodium phosphate (TSP) against Salmonella typhimurium and Salmonella enteritidis in vitro. One milliliter of each TSP solution (0.5, 1, 1.5 and 2% w/v) was mixed with 1 mL of each bacterial culture and left to stand at room temperature (18  ±  1C) for 0, 15, 30, 45, 60 or 90 min before enumeration of the surviving pathogens.
The effects of 1.5 and 2% TSP were apparent on both bacterial species from 0 min and bacterial counts reached undetectable ( < 1.0  ×  10¹ cfu/mL) levels immediately. The 1% TSP solution effected close to 4.20–5.72 log reduction after 15 min. However, the reduction effect of 0.5% TSP was a function of treatment time, and some culturable bacteria remained even after 90 min of treatment. These results suggest that the bactericidal effect of TSP solution on these pathogens depends on its concentration and on the duration of treatment.

PRACTICAL APPLICATIONS

Poultry has been identified as one of the most important reservoirs of Salmonella typhimurium and Salmonella enteritidis in food chain. Efforts to eliminate or reduce Salmonella spp. and other pathogens attached to poultry carcasses during processing have been made for many years. In 1992, the U.S. Department of Agriculture approved the use of trisodium phosphate (TSP) as a processing aid to reduce Salmonella spp. on raw poultry carcasses. The aim of the present study was to determine the bactericidal effects of different concentrations of TSP on pure cultures of these pathogens in vitro .     

CHANGES IN QUALITY DURING STORAGE OF VACUUM-PACKED SEA BASS (DICENTRARCHUS LABRAX, Linnaeus, 1758) COOKED BY DIFFERENT METHODS

This work evaluates the chemical, microbiological and sensorial characteristics of vacuum-packed sea bass processed by different cooking methods under different time/temperature conditions and storage at 2C. The heat treatments applied in core were: 5 min, at 180C for frying, 30 mi, at 230C for baking, and 16 min at 2450 MHz for microwave cooking. Chemical, microbiological and sensory quality changes were investigated periodically. In all groups; the total viable and psycrophilic bacteria counts increased throughout the storage period of vacuum-packed sea bass. Total viable counts of fried, baked and microwave-cooked sea bass reached 6.06, 7.00, 7.24 log cfu/g, respectively, after 15 days. On day 15, the total volatile base nitrogen (TVB-N) value of microwave-cooked sea bass exceeded the allowable limit of 38.72 mg/100 g, whereas the TVB-N value of fried and baked sea bass reached 22.46 and 29.85 mg/100 g, respectively. Therefore, it can be concluded that frying at 180C for 5 min in core is the most effective cooking method to ensure the safety and extend the shelf life of fried sea bass, preserving its microbiological guality.

PRACTICAL APPLICATION

This study establishes the chemical, microbiological and sensory quality of vacuum-packed sea bass and emphasizes the relevance of the quality changes of the different cooked sea bass. Heat treatments and storage temperatures are very important to ensure the safety of the fish product.     

The manufacture and some quality characteristics of kurut, a dried dairy product

This study was designed to investigate the microbiological and chemical characteristics of kurut, a dairy product obtained by drying yogurt under the sun in rural areas of Turkey. For this purpose, 50 randomly collected kurut samples from the Kars Region were analysed for determination of their microbiological and chemical characteristics. Analysis of kurut samples showed that kurut contained on average 4.52 log₁₀ cfu/g of aerobic mesophilic bacteria, 2.78 log₁₀ cfu/g of aerobic mesophyl spores, 3.60 log₁₀ cfu/g of lactic acid bacteria, 3.60 log₁₀ cfu/g of Lactococcus , 3.94 log₁₀ cfu/g of mould and yeast, 2.13 log₁₀ cfu/g of Enterobacteriaceae, l.51 log₁₀ cfu/g of sulphite-reducing clostridia, and 1.81 log₁₀ cfu/g of coagulase-positive s taphylococci . Coliform bacteria and enterococci bacteria were not detected in any of the kurut samples. Furthermore, chemical characteristics of the kurut were as follows: pH 4.2, acidity (lactic acid) 2.9, moisture 12.1%, fat 45.9% protein 25.5%, salt 6.7% and ash 10.0%. The quality characteristics of kurut presented here may help create a different perspective for new products to be produced in the dairy sector.     

SIDEROPHORE PRODUCTION, SERUM RESISTANCE, HEMOLYTIC ACTIVITY AND EXTENDED-SPECTRUM β-LACTAMASE-PRODUCING KLEBSIELLA SPECIES ISOLATED FROM MILK AND MILK PRODUCTS

This study aimed at the isolation and identification of Klebsiella spp. from dairy product to establish their public health significance by determining their virulence factors, antibiotic resistance and extended‐spectrum β‐lactamase (ESBL). Klebsiella pneumoniae, Klebsiella oxytoca and Klebsiella rhinoscleromatis were identified in 25 (58%), 11 (26%) and 7 (16%) isolates, respectively. A high prevalence of Klebsiella isolates had virulence factors such as siderophore production (63%), serum resistance (32.5%) and hemolytic activity (58%). ESBL‐producing Klebsiella spp. was detected in 35% of the isolates. Resistance to the antimicrobial agents tested was found to be much higher in the ESBL‐producing Klebsiella spp. than in non‐ESBL‐producing isolates. All ESBL‐producing Klebsiella spp. showed high‐level resistance to cephalosporins and monobactams. The majority of the serum resistant, siderophore, hemolysin and ESBL producers were K. pneumoniae.