Although ripening causes gradual decrease in starter cul- tures due to harsh cheese-ripening environment such as little or no residual lactose and high ripening temperatures, usually non- starter LAB in cheese begin to grow during ripening and eventually plateau at cell densities of 107–108 cfu/g after 3–9 months of aging (Peterson & Marshall, 1990), because A fraction of the dying starter cells undergo autolysis, which releases intracellular enzymes and cellular components such as sugars and nucleic acids into the cheese matrix facilitating non-starter LAB growth in cheese (Pe- terson & Marshall, 1990; Broadbent et al., 2013).
The growth and activities of cheese starter cultures and non- starter LAB can be affected by nisin (Benech et al., 2003). However in the present study, nisin did not demonstrate any major negative effect on the total lactic acid bacteria during storage and the counts were within the range of 8.1370.02–8.5970.01 log cfu/g for both nisin incorporated and control samples (Fig. 2). Generally, microbial cultures show variable sensitivity to nisin. The higher viability levels of LAB in nisin incorporated cheese samples in the present study may have been due to their ability in tolerating ni- sin. Since these microorganisms play a significant role in cheese ripening and flavor development, careful selection of appropriate starter cultures and non-starters with low nisin sensitivity is vital in harnessing the beneficial effects of nisin, because the main objectives of using nisin as a biopreservative in food systems is to control the pathogenic microbes, but not the beneficial, flavor enhancing and health promoting microbes.
Although ripening causes gradual decrease in starter cul- tures due to harsh cheese-ripening environment such as little or no residual lactose and high ripening temperatures, usually non- starter LAB in cheese begin to grow during ripening and eventually plateau at cell densities of 107–108 cfu/g after 3–9 months of aging (Peterson & Marshall, 1990), because A fraction of the dying starter cells undergo autolysis, which releases intracellular enzymes and cellular components such as sugars and nucleic acids into the cheese matrix facilitating non-starter LAB growth in cheese (Pe- terson & Marshall, 1990; Broadbent et al., 2013).The growth and activities of cheese starter cultures and non- starter LAB can be affected by nisin (Benech et al., 2003). However in the present study, nisin did not demonstrate any major negative effect on the total lactic acid bacteria during storage and the counts were within the range of 8.1370.02–8.5970.01 log cfu/g for both nisin incorporated and control samples (Fig. 2). Generally, microbial cultures show variable sensitivity to nisin. The higher viability levels of LAB in nisin incorporated cheese samples in the present study may have been due to their ability in tolerating ni- sin. Since these microorganisms play a significant role in cheese ripening and flavor development, careful selection of appropriate starter cultures and non-starters with low nisin sensitivity is vital in harnessing the beneficial effects of nisin, because the main objectives of using nisin as a biopreservative in food systems is to control the pathogenic microbes, but not the beneficial, flavor enhancing and health promoting microbes.
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