How Can Bacteriocins or Substances Bacteriocins-Like Impact on Cheese Ripening?

For in situ bacteriocin production in cheese, strains must be able to grow to high concentrations and be active in the cheese environment. Bacteriocins like nisin and pedi- ocin with a broader activity spectrum are active on bacteria closely related to producer strain or confined to same ecological niche. Thus, the presence of bacteriocin, produced in situ or added, can alter the natural balance and dynamics of the cheese microflora, including starter cultures.

The texture, physical, chemical, and sensory characteristic of cheddar cheese made with a mixed culture consisting of Lactococcus lactis subsp. lactis biovar diacetylactis UL 719 and two nisin-tolerant lactococci with high acidifying capacity in milk, have been investigated (Benech et al., 2003). After six months of ripening, the rheological characteristics were not so different, while proteolysis, lipolysis, and the concentration of hydrophilic and hydrophobic peptides increased in cheese containing the nisin Z strain producer compared with control cheese. The cheeses produced using the abovedescribed strains, in combination or not with Lactococcus diacetylactis UL 719, presented a bitter off-flavor and acidic taste due to a low amino-peptidasic activity of these strains compared with commercial starter cultures.

However, the bitterness could be reduced and flavor improved adding some proteolytic strains such as Lactobacillus casei/paracasei in the mixed cultures containing the nisin Z producer.

Bacteriocins can induce lysis of sensitive starter cultures leading to a fast release of intracellular enzymes that may play an important role on flavor development. Bacteriocins may also promote diffusion of molecules such as amino acids in the cells, through membrane permeabilization.

The pool of amino acids released may lead to an increased rate of transamination and formation of an alpha-Ketoacid, which can be further degraded enzymatically into flavor compounds.

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