Changes in the microbial flora of Zamorano cheese (P.D.O.) by accelerated ripening process

Abstract

Five batches of Zamorano cheese (P.D.O.), manufactured from pasteurized ewe’s milk with the addition of a lactic starter culture, were ripened at various controlled temperatures (180 days at 10 °C; 60 days at 10 °C and 120 days at 15 °C; 60 days at 10 °C, 60 days at 15 °C and 60 days at 10 °C; 60 days at 15 °C and 120 days at 10 °C and 180 days at 15 °C). The effect of these ripening conditions on the changes undergone by the microbial flora was studied during manufacture and ripening of the cheeses with the aim of learning whether any of these conditions could accelerate ripening of Zamorano cheese. Lactococci (flora from the starter added) maintained high counts (log count 8–9 cfu g −1) for the first two months of ripening in the cheeses in each batch. Thereafter, counts dropped faster in cheeses from batch E, which was kept at 15 °C for the whole ripening process. The effects of temperature were clearest in the changes in lactobacilli (non-starter lactic acid bacteria). Lactobacilli counts were 3 log units higher in batches D and E with respect to the remainder of the batches until the end of the first month of ripening. In 60-day-old cheeses the difference fell to 2 log units and by the end of ripening the counts were similar in all batches.