substituted in the formulae, the result is higher than a specified value
then this indicates that the product would be microbiologically stable or
safe depending on the formula used.
The formula for safety is:
15 : 75 ð 1 aÞð% total acetic acidÞþ 3 : 08 ð% saltÞþð% hexoseÞ
þ 0 : 5 ð% disaccharideÞþ 40 ð 4 : 0 pHÞ¼
X
sð 9 : 5 ÞWhere (1a) is the proportion of undissociated acetic acid,ais the
proportion dissociated, given by the expression:
pH¼pKþlog½a=ð 1 aÞð 9 : 6 Þwhere pK¼4.76.
Any sauce based on acetic acid with
P
s^4 63 is regarded as intrinsi-
cally safe, since viable numbers ofE. coliin it will decline by more than 3
log cycles in less than 72 h at 20 1 C. The formula for stability is:
15 : 75 ð 1 aÞð% total acetic acidÞþ 3 : 08 ð% saltÞþð% hexoseÞ
þ 0 : 5 ð% disaccharideÞ¼X ð 9 : 7 ÞIfP
4 63, any sauce with this formulation should be microbiologi-
cally stable without refrigeration, even after opening.
The mouldMoniliella acetoabutans, the micro-organism most resistant
to acetic acid, would still grow in such products but can be controlled by
good hygienic practices and pasteurization of ingredients containing
vinegar. Experience in the pickle and sauce industry indicates that
spoilage byMoniliellais rare.
Products meeting the CIMSCEE requirement for stability would have
a relatively strong taste of acid or salt. If levels of these ingredients are
reduced to produce a milder taste then some supplementary preservative
measure would be necessary such as sorbate, a final pasteurization step
or refrigerated storage.
9.12 Mould Fermentations
Mould fermentations are an aspect of fermented foods that, up until
now, we have mentioned only briefly. Failure to remedy this neglect
would give a seriously unbalanced view for, in the East particularly,
moulds play a key role in a number of food fermentations.
9.12.1 Tempeh
Tempeh is a traditional mould-fermented food in Indonesia, though it
has also attracted interest in the Netherlands and United States. The most
362 Fermented and Microbial Foods