Efficacy of nisin and/or natamycin to improve the shelf-life of Galotyri cheese

The present study evaluated the use of nisin, natamycin and/or their combination as antimicrobial treatments to improve the shelf-life of Galotyri cheese. Samples were treated with nisin [N1 (100 IU/g), N2 (200 IU/g)], natamycin [NA1 (0.01% w/w), NA2 (0.02% w/w)] and their combinations N1-NA1, N1-NA2, N2-NA1 and N2-NA2. A Galotyri control (N0) cheese sample was also tested (absence of nisin or natamycin). Single N1, N2 treatments reduced lactobacilli and lactococci populations, but their effect was less pronounced, as compared to the combined nisin-natamycin treatments between days 14 and 28 of storage. Yeast populations in natamycin-treated Galotyri cheese samples or those additionally treated with nisin were significantly suppressed throughout the entire period of storage. Control N0 or N1, N2 treated samples received significantly lower acceptability scores, as compared to either natamycin or natamycin-nisin treated samples. Natamycin, added either singly or in combination with nisin, efficiently suppressed fungal growth in the Galotyri cheese. The observed shelf life of Galotyri, based on overall acceptability data, was the longest for N1-NA1, N1-NA2, N2-NA1 and N2-NA2 cheese samples (>28 days) followed by the N1, N2 treated samples (18-19 days) whereas for the control N0 a shelf-life of 14-15 days was attained.