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The protein composition and the milk yield (morning milking) were studied in 10 Chilean Holstein–Friesian first lactation dairy cows during the spring season. In addition, the genetic variants A and B of κ‐casein (κ‐CN) and β‐lactoglobulin (β‐Lg) were also identified. The results showed that the casein content is significantly affected by the presence of B variant of κ‐CN. Moreover, positive interactions between the B variant of κ‐CN with AB of β‐Lg and the combination of A κ‐CN with AA of β‐Lg for the total protein content, were found.

Three culture media were studied for the bacteriocin like substance (BLS) production from Carnobacterium piscicola L 103 in a batch and continuous culture system. The efficacy of the antagonistic substance against Listeria monocytogenes was tested on vacuum packaged salmon. BLS was produced in a 1.0 L bioreactor by batch and continuous culture using D-MRS, mod. D-MRS and APT as nutrient broths. Salmon fillets were inoculated with BLS (200 AU mL -1 and 800 AU mL in D-MRS and mod. D-MRS broth, and of 400 AU mL -1 in APT broth. During continuous culture BLS activity increased to 6400 AU mL -1 in both types of MRS broths, while in APT the activity decreased to 50 AU mL -1 , indicating a clear advantage of the first two culture media and also of the continuous culture system. BLS had a bacteriostatic effect on L. monocytogenes when inoculated on salmon, with counts of 6.0 x 10 3 cfu cm -2 after 15 days. No significant differences were found between the two BLS activities used. In the control without BLS, L. monocytogenes counts increased to 1.0 x 10 6 cfu cm -2 after 15 days of storage.

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The purpose of this study was to relate the genetic variants A and B of κ‐casein (κ‐CN) and β‐lactoglobulin (β‐Lg) of the milk of 10 Chilean Holstein–Friesian cows and its coagulation properties (coagulation ability of milk, curd firmness and syneresis of the curd). The results showed that β‐Lg AB phenotypes have a significant effect on the studied properties in comparison with the samples containing the AA phenotype. A and B variants of κ‐CN did not have a significant effect on the coagulation properties, although there was a favourable interaction between β‐Lg AB and κ‐CN B.