Abstract:
Yield, proximate composition, and proteolytic activity were
determined in each unit operation during production of surimi from
Pacific whiting. Preliminary studies involved the addition of protein
adjuncts such as egg white (EW), whey protein concentrate (WPC), and soy
protein isolate (SPI), at different levels, to kamaboko gels in order to
select the main protein for further study. SDS-gel electrophoresis was
performed to evaluate the effectiveness of egg white as a protease
inhibitor in kamaboko gels.
Yields obtained from planked fish (42.4%) and minced flesh (35.7%)
agree with those values reported from other studies in whiting. A
reduced washed flesh yield was expected since washing is done to remove
those constituents not desirable in surimi. Lower yields resulted in
the refined flesh (17.4%), and surimi (19.9%). Proximate composition
values through the unit operations were similar with other studies done
with whiting, and were compared with other fish species indicating
acceptable nutritional quality. Deboned and washed flesh (first wash)
were significantly different in protease activity from the flesh (second wash) and refined product (P<0.05). This demonstrates the importance of
the washing process in surimi unit operations.
Protein adjuncts (EW, WPC, and SPI) in kamaboko gels at levels of 1
to 5% were evaluated based on hardness, cohesiveness and elasticity.
Addition of egg white at levels ranging from 3 to 5% resulted in greater
hardness (P<0.05), and elasticity (P<0.005) in comparison with WPC and
SPI. Therefore EW at 3% level was selected for additional study.
Two stage heat treatments at 40°C at varying times followed by a
90°C for 20 min were tested with kamaboko gels containing 3% EW. No
significant differences were found in hardness and elasticity compared
to a one stage heat treatment at 90°C for 40 min (P<0.01). Based on
this study, a one stage heat treatment was selected for the cooking of
kamaboko gels.
Potato starch at a level of 5% was also included in the following
formulations due to its property to increase binding and elasticity. An
increased hardness of 154% and elasticity 464% in kamaboko gels
containing 3% EW was found compared to the control. An increase of 9%
in hardness, and 23% in elasticity was found in gels containing 3% EW
and 5% potato starch compared to gels containing only 3% EW. A
significant difference was found in expressible moisture within the
three formulations (P<0.03) due to the addition of the ingredients and
their binding properties.
Egg white proved to have an inhibiting effect on proteolytic
activity in kamaboko gels. This was demonstrated by SDS
gel-electrophoresis in which the myosin band was present in formulations
containing 3% egg white and indicated that no enzymatic breakdown was
taking place.
