Freezing Studies on a Model System and Quality Changes in Frozen Malaysian Fish
Variations in the definition of freezing time do not provide a universally accepted definition which adequately describe the freezing rate. A "volume average freezing time" was derived as an alternative definition of freezing time which gave a linear relationship with frozen depth . Th...
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| 格式: | Thesis |
| 語言: | English English |
| 出版: |
1985
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| 主題: | |
| 在線閱讀: | http://psasir.upm.edu.my/id/eprint/9681/1/FSMB_1985_2_A.pdf |
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| 總結: | Variations in the definition of freezing time do not provide
a universally accepted definition which adequately describe the
freezing rate. A "volume average freezing time" was derived as an
alternative definition of freezing time which gave a linear
relationship with frozen depth . The majority of the experimental
values was found to fall within 20% of the predicted figures using
the derived formula .
Proximate analysis , objective and organoleptic tests were done
on Chub Mackerel, Yellow-banded Trevally and Notched Threadf in Bream.
Samples of gutted and ungutted fish were frozen fast and slow, and
stored in the glazed and unglazed conditions at - 20˚C for 16 to 24
weeks. At intervals various chemical indices of deterioration were
determined and taste-panel assessment performed. The data on lipid
oxidation, protein denaturation and pH changes were related to
textural, flavour, odour and general acceptability performances.
The quality of canned frozen Chub Mackerel were also determined.
Malonaldehyde production in Threadfin Bream (0.8% fat content)
was low and similar to that in Yellow-banded Trevally (9.7% fat
content), whereas values for Chub Mackerel (2.1% fat content) was
higher than both the former two species and were produced over a
shorter storage period. These differences were also shown to conform
to odour and flavour scores for all the three species . The protein
solubility in Threadfin Bream (pH = 6.8) and Yellow-banded Trevally
(pH = 6.15) remained low during the storage period which results in a softer texture. In comparison, Chub Mackerel (pH = 6.15) had a
firmer texture as protein solubility remained higher during the
storage period. Threadfin Bream and Yellow-banded Trevally also
gave higher general acceptability scores over that of Chub Mackerel
at the same storage period, and the storage life of the two former
species were longer than the latter.
TBA values of canned Chub Mackerel prepared from frozen fish
increased during subsequents to rage, and proportional to the length
of frozen storage period before canning. The general acceptability
scores decreased with increase in period of frozen storage before
canning. The limit of frozen storage period for Chub Mackerel before
canning is one month or less for an acceptable canned product to
last for not more than three months. Generally fresh fish gave a
better canned product than frozen fish. |
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