Fundamental Food Microbiology, Third Edition - Fuad Fathir

284 FUNDAMENTAL FOOD MICROBIOLOGY
(such as Gouda, Emmentaler, and provolone) can also occur from the growth of
some Clostridium (e.g., Clo. tyrobutyricum). Their spores survive pasteurization of
milk, germinate, and grow in the anaerobic environment to produce CO 2, H 2, and
butyrate from the metabolism of lactate. Hard-ripened cheese, such as cheddar, can
have a bitter taste due to rapid production of bitter peptides during ripening. Fast
acid-producing strains of Lactococcus lactis used as starters are generally associated
with this defect. Sharp-ripened cheeses can also have large amounts of biologically
active amines (e.g., histamine and tyramine), produced from the decarboxylation of
the respective amino acids by decarboxylase. Decarboxylase enzymes can be present
in some starter strains or in secondary microflora of the cheeses (Enterococcus, some
coliforms). Lysis of the cells releases the enzymes during the ripening process,
causing decarboxylation of amino acids and accumulation of these amines. Hard
and semihard cheeses are generally susceptible to spoilage from mold growth on
the surface and produce undesirable color and flavor defects in the products. Anaerobic
packaging greatly reduces this problem.
C. Fermented Vegetable and Fruit Products
Many types of vegetables are fermented, among which cucumber and sauerkraut are
produced in large volumes. In salt stock pickles containing ca. 15% salt, yeasts and
halophilic bacteria can grow, especially if the acidity is not sufficient. Dill pickles
with low salt (