Inhibition of Clostridium tyrobutyricum in Vidiago cheese by Lactococcus lactis ssp. lactis IPLA 729, a nisin Z producer

Abstract

Lactococcus lactis ssp. lactis IPLA 729 is a nisin Z producer isolated from raw milk cheese able to grow and produce nisin Z in milk. The ability of this strain to inhibit the growth of Clostridium tyrobutyricum CECT 4011, a late blowing agent, in Vidiago cheese, a semi-hard farmhouse variety, manufactured in Asturias, Northern Spain, was investigated. For control purposes, cheeses were manufactured with the mesophilic mixed starter IPLA-001. In experimental cheeses, the nisin-producing strain L. lactis IPLA 729 was combined with this starter. Nisin Z activity reached a concentration of 1600 AU/ml in 1-day cheeses and this level was maintained until 15 days of ripening. Furthermore, to compare the inhibitory activity of the nisin-producing strain to nitrate, cheeses were also manufactured with a commercial starter culture and potassium nitrate as anti-blowing agent was added in accordance with Vidiago's cheesemakers. The control, experimental and commercial cheeses were contaminated with C. tyrobutyricum CECT 4011. The composition of the three different cheeses showed only slight differences with respect to total solids, protein and fat, although control and experimental cheeses showed a richer flavour-compound profile than commercial cheeses. The level of the spoilage strain C. tyrobutyricum CECT 4011 decreased from 1.2×10 6 to 1.3×10 3 cfu/g during ripening in presence of the nisin Z producer, while it increased to 1.99×10 9 cfu/g in control cheeses and to 3.5×10 7 cfu/g in commercial cheeses.