yeast in suspension and active at such high alcohol concentrations.
At the end of fermentation which typically lasts for three weeks, the
product is settled, filtered and blended before being pasteurized and
bottled.
A number of other rice-based mould starters are used in the countries
of East and Southeast Asia to fulfil a similar role tokoji(Table 9.11).
They are used to produce sweetened rice products which can be con-
sumed fresh or added to other products (see Section 9.9) or can be
used as a base for the production of rice wine and rice vinegar. The
microbiological composition of these generally differs from that ofkoji
and comprises primarilyRhizopusandMucorspecies and amylolytic
yeasts.
9.12.3 Mycoprotein
Products such astempehandkojicontain a significant amount of mould
biomass and a reasonable extension of this type of approach would be to
grow up mycelium itself as a source of food. Of the many investigations
into the growth of moulds on readily available substrates one has
successfully emerged as a commercial product. Mycoprotein, marketed
as Quorn, is essentially the mycelium ofFusarium venenatum(formerly
F. graminearum) grown in continuous culture in a medium containing
glucose, ammonium salts and a few growth factors. Advantages associ-
ated with the use of a filamentous organism are that it can be harvested
by filtration and washing and can be readily textured to give the product
an acceptable mouth-feel.
To be acceptable as a food for human consumption it is necessary to
reduce the level of RNA, which is nearly 10% based on mycelial dry
weight, to below the levels likely to lead to kidney-stone formation or
gout. This is achieved by a mild heat treatment prior to filtration which
activates the mould’s RNAases and leads to a dramatic reduction of
RNA to about 1% which is acceptable. The product has a useful protein
content of 44% and is high in ‘fibre’ because of the cell walls of the
filamentous fungal structure.
Table 9.11 Amylolytic mould preparations
koji Japan
look pang Thailand
ang-kak Philippines
ragi-tapai Malaysia/Indonesia
nuruk Korea
peh-yueh China
bakhar N. India368 Fermented and Microbial Foods