Effect of cover brine type on the quality of meat from herring marinades.

Effects of vinegar, oil, and sour cream brines on meat quality of 4 popular cold marinades from herring were investigated in the study. Cover brine type affected the composition and nutritive value of meat as well as the sensory and microbiological quality of marinated herring. Qualitative differences resulted from cover brine penetration into meat, and from diffusion of components from meat to vinegar brine. Compared to oil and sour cream, vinegar brine contributed to increased concentrations of salt and acetic acid, hardness, color brightness of marinades meat and to increased microbial contamination of meat. Furthermore, vinegar caused nitrogen losses to 15%, including valuable products of protein hydrolysis, enzymes, and total volatile bases. The rolling up of fillets reduced diffusion even by 50%. In turn, oil and sour cream were causing mainly a higher fat content and overall sensory evaluation of the marinades.

The possible effect of a sanitization program on intraspecies differentiation of Listeria monocytogenes strains isolated from a fish processing plant.

Forty-seven Listeria monocytogenes strains isolated during a year in a selected Polish fish-processing plant as well as 7 L. monocytogenes strains of different origins (including a reference strain) were analyzed in our studies. Strains were isolated from raw fish fillets (flounder), frozen coated flounder fillets, coating ingredients, and the processing environment. Isolation of strains covered the period of a sanitization program introduced in the plant. L. monocytogenes was identified using conventional microbiological methods and the PCR technique. RAPD (random amplified polymorphic DNA) technique for fingerprinting was applied to analyze the intraspecies diversity. Six RAPD types (A-F) and seven unique strains were revealed as a result of fingerprinting with one persistent type isolated from July 1999 to February 2000. It was detected for the first time after one month of sanitization. Its occurrence could have been promoted by clone selection either due to ineffective disinfection or to resistance against the disinfectant. As L. monocytogenes mostly occurred on frozen products, this indicates that contamination could start during product freezing, cold storage, or handling. The results revealed that there is a crucial need for preparing sanitization schemes precisely targeted at L. monocytogenes to avoid its recurrence as persistent 'in-house' strains. The possibility of incorrect interpretations of classical microbiological test results as well as the necessity to introduce assays based on nucleic acid analysis into epidemiological investigations were emphasized.