Impact of salting and ripening temperatures on late blowing defect in Valtellina Casera PDO cheese

Abstract

Clostridial contamination of raw milk can cause the late blowing defect (LBD) in semi-hard and hard cheeses. In this study we have evaluated the influence of salting and ripening temperatures on LBD appearance in Valtellina Casera PDO cheese. Four cheese lots were brined at two different temperatures (8 and 13 °C) and successively ripened at 8 or 13 °C for 90 days. To evaluate the spore content a modified most probable number (MPN) method was used. The brining temperature of 8 °C seemed to prevent clostridial germination. During the ripening we detected LBD symptoms in all the cheeses aged at 13 °C, while no defects were observed in those placed at 8 °C. Clostridium tyrobutyricum resulted to be the main cause of LBD and its development was temperature-dependent. Volatilome analysis highlighted rancid volatile compounds in cheeses ripened at 13 °C. A combination of salting and ripening temperatures resulted to be an effective strategy to prevent and control the LBD in cheeses. A brine temperature of 13 °C followed by an aging at 8 °C inhibited the germination of C. tyrobutyricum spores during brining and subsequent germination during ripening.