51
Salting
Since the freshly prepared pehtze has no taste, salting and ripening are carried out
to develop flavour and aroma in the pehtze. Pehtze is capable of absorbing salt and
thus loses water until the salt content reaches up to a saturation level. This salt
imparts certain taste to pehtze and thereby inhibits further fungal growth and also
prevents the product from microbial contamination (Nout and Aidoo 2010). There
are several ways in which salting is carried out. One such way involves transferring
of pehtze to vessels containing saturated salt solution kept at room temperature.
After 4–5 days, the salt content of pehtze reaches up to 12% and thereby reduces the
moisture content up to 10–15%. In another method, pehtze is submerged in an alcoholic saline solution comprising 12% NaCl and 10% ethanol. This method is a combination of both salting and ripening in one step.
Ripening
In this stage, the enzymes produced by the mould act upon its respective substrates
and thereby hydrolyze the protein and lipid, thus resulting in the production of principal compounds responsible for generating flavour and aroma in sufu. According to
Hwan and Chou in 1999, the complicated flavour and aroma of sufu were reported
to be the result of 22 esters, 18 alcohols, 7 ketones, 3 aldehydes, pyrazines, 3 phenols and other volatile compounds (Hwan and Chou 1999).
4.4.3 Red Kojic Rice
Red kojic rice, popularly termed as angkak, Chinese red rice, red qu or red yeast
fermented rice, is conventionally obtained by fermentation of cooked rice using
Monascus spp. such as M. anka, M. purpureus or M. ruber. Red fermented rice is
referred to as koji in Japan, which has a specific aroma and purplish red tinge making it a potent colourant in red furu, red spirit and red rice (Chiao 1986). Several
other researchers have also studied secondary metabolites being produced by
Monascus species (Blanc et al. 1994; Lin et al. 2008).
4.4.3.1 Fungi Involved
In a liquid culture of Monascus anka MF107, the growth and pigment production
were distinguished into three different phases (Fu et al. 1996). The first phase of
liquid culture is dominated by mycelial growth and the pH of the media decreases
from 5.5 to 4.6, and the second phase involves steady pigment production, thereby
decreasing the pH from 4.6 to 8.4. And finally, the third phase is of gradual
4 Fungi in Food Bioprocessing
Salting
Since the freshly prepared pehtze has no taste, salting and ripening are carried out
to develop flavour and aroma in the pehtze. Pehtze is capable of absorbing salt and
thus loses water until the salt content reaches up to a saturation level. This salt
imparts certain taste to pehtze and thereby inhibits further fungal growth and also
prevents the product from microbial contamination (Nout and Aidoo 2010). There
are several ways in which salting is carried out. One such way involves transferring
of pehtze to vessels containing saturated salt solution kept at room temperature.
After 4–5 days, the salt content of pehtze reaches up to 12% and thereby reduces the
moisture content up to 10–15%. In another method, pehtze is submerged in an alcoholic saline solution comprising 12% NaCl and 10% ethanol. This method is a combination of both salting and ripening in one step.
Ripening
In this stage, the enzymes produced by the mould act upon its respective substrates
and thereby hydrolyze the protein and lipid, thus resulting in the production of principal compounds responsible for generating flavour and aroma in sufu. According to
Hwan and Chou in 1999, the complicated flavour and aroma of sufu were reported
to be the result of 22 esters, 18 alcohols, 7 ketones, 3 aldehydes, pyrazines, 3 phenols and other volatile compounds (Hwan and Chou 1999).
4.4.3 Red Kojic Rice
Red kojic rice, popularly termed as angkak, Chinese red rice, red qu or red yeast
fermented rice, is conventionally obtained by fermentation of cooked rice using
Monascus spp. such as M. anka, M. purpureus or M. ruber. Red fermented rice is
referred to as koji in Japan, which has a specific aroma and purplish red tinge making it a potent colourant in red furu, red spirit and red rice (Chiao 1986). Several
other researchers have also studied secondary metabolites being produced by
Monascus species (Blanc et al. 1994; Lin et al. 2008).
4.4.3.1 Fungi Involved
In a liquid culture of Monascus anka MF107, the growth and pigment production
were distinguished into three different phases (Fu et al. 1996). The first phase of
liquid culture is dominated by mycelial growth and the pH of the media decreases
from 5.5 to 4.6, and the second phase involves steady pigment production, thereby
decreasing the pH from 4.6 to 8.4. And finally, the third phase is of gradual
4 Fungi in Food Bioprocessing