The optimum conditions for the proteolytic solubilization of
trash fish and processing carcass waste in a simple shell-in-tube
heat exchange system was investigated. The nutritional and chemical
effects of processing variables were evaluated.
An exogenous source of proteolytic enzymes (albacore tuna
viscera, Thunnus alalunga) yielded a linear increase in the rate of
the proteolytic hydrolysis of ground whole Pacific hake (Merluccius
productus) up to 40% in the reaction mixture at 55°C. At 60°C optimum
temperature for proteolytic hydrolysis was established with a
20% viscera 80% hake reaction mixture. Acidification of hake with
85% H₃PO₄ greatly accelerated proteolytic hydrolysis yielding an
optimum between pH 3.6 and 3.7. The optimum pH for liquification
based upon the viscometric properties of reaction mixtures varied
from that for hydrolysis and was between 4.3 and 5.1.
The chemical characteristics of the proteolytic solubilization
of hake at 55°C was determined. The total nitrogen and free amino
and tyrosine equivalent content of trichloroacetic acid (TCA), water
and sodium dodecylsulfate (SDS) fractions of reactions containing 0,
2 and 4% 85% H₃PO₄ were determined at various times over a two hr
period. With accelerated reactions (2 and 4% 85% H₃PO₄) the rate of
hydrolysis was greatly reduced after 30 min. Under less than optimum
pH conditions (0% 85% H₃PO₄) proteolytic hydrolysis proceeded
in a linear fashion throughout the two hr period. The relationship between
the quantities of chemical indices in the TCA and water fractions
suggested that the majority of the proteolytic action yielded
amino acids and short peptides. The total nitrogen content of the SDS
soluble fraction inferred that very little of the protein that was not
SDS soluble was being solubilized.
The protein efficiency ratio of samples of hake reacted at 55°C
in the presence of 0, 2 and 4% (wt/wt) 85% H₃PO₄ at 30, 60, and
120 min was determined to assess the nutritional effects of proteolytic
solubilization. Proteolytic action reduced protein quality to a
degree related directly to the level of acid accelerated proteolytic
action. Full reduction in quality was accomplished at the end of 30
min for reaction mixtures containing 0 and 2% acid in comparison to
a raw hake control; no reduction was observed between 30 and 120
min. In addition to the initial reduction in quality within the first 30 min of reaction, mixtures containing 4% acid were significantly reduced
between 30 and 120 min. Conversion of native protein to
nutritionally less utilizable amino acids and peptides probably played
the major role in reducing protein quality in reaction mixtures containing
0 and 2% acid. The time dependent reduction in protein
quality for the reactions containing 4% supports the destruction of
amino acids, probably tryptophan, at this higher level of acidity. / Graduation date: 1977
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27192 |
| Date | 24 January 1977 |
| Creators | Timmerman, Conrad Dietrich |
| Contributors | Crawford, David L. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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