This is the first in depth study investigating the effects of
different chemical leavening agents and extrusion cooking conditions
on lysine loss as determined by furosine content in cornbased
extrudates.
There is no previous report on the effects of CO2 on the furosine
formation mechanism in extrusion cooking. Therefore, in the present
study, it was decided to investigate CO2 injection with relation
to furosine formation and properties of extrudates. The results
indicated that there were no significant differences in furosine
contents of extrudates produced with the CO2 injection method as
compared to those produced by the conventional extrusion
method. On the other hand, the CO2 injection method had a positive
effect on the physical properties of the extrudates. Furthermore,
furosine levels of extrudates significantly decreased when
the feed moisture content increased from 22% to 26% in both
extrusion methods. In other words, increased feed moisture had a
protective effect against lysine loss during extrusion cooking. This
could be due to the fact that water is a product of the Maillard
reaction. It is well known that Amadori compounds which are
formed in the early stages of the Maillard reaction are not stable,
and they are lost depending on the severity of the heat treatment.
Therefore, furosine contents of the extrudates significantly
decreased as the exit die temperature was increased from 110 to
150 C, as expected. In conclusion, the level of furosine, as an indicator
of Amadori compounds, formed during the early stages of
the Maillard reaction, was highly influenced by leavening agent,
temperature, and feed moisture content in extrusion cooking.