End of Project ReportCheddar cheese is a complex microbial ecosystem. The internal
cheese environment, in particular of hard and semi-hard cheeses, is
not conducive to the growth of many microorganisms.
At the beginning of ripening the dominant microorganisms are the
starter bacteria which are present at high levels (~109/g). However,
during ripening, non-starter lactic acid bacteria (NSLAB) grow from
relatively low levels (<103/g) at the beginning of ripening, to 108/g
within 6 - 8 weeks. Other bacteria, e.g. enterococci and staphylococci,
may also be present but in much lower numbers.
In a previous study of mature and extra mature Cheddar cheeses from
different manufacturers (see End of Project Report No. 1), it was
found that the NSLAB population was dominated by strains of Lb.
paracasei. However, their contribution to cheese flavour and their
source(s) are still unclear, nor is it known if the NSLAB flora is unique
to each plant. Hence, understanding the growth of this group of
organisms in cheese is a key to defining their role in flavour
development.
The biochemistry of flavour development in cheese is poorly
understood. For most cheese varieties, including Cheddar,
proteolysis, which results in the accumulation of free amino acids, is
of vital importance for flavour development. Increasing evidence
suggests that the main contribution of amino acids is as substrates for
the development of more complex flavour and aroma compounds.
The manner by which such compounds are generated in cheese is
currently the focus of much research.
Starter bacteria have been shown to contain a range of enzymes
capable of facilitating the conversion of amino acids to potential
flavour compounds. However, the potential of lactobacilli (NSLAB) to
produce similar enzymes has only recently been investigated. Hence, although, it is generally accepted that the cheese starter flora
is the primary defining influence on flavour development, the
contribution of NSLAB is also considered significant.
The objectives of these studies were:
- to develop a greater understanding of the behaviour of NSLAB in
cheese, and
- to identify suitable strains, and other cheese bacteria, to be used as
starter adjuncts for flavour improvement.Department of Agriculture, Food and the Marin
