摘要：

The optimum conditions for the proteolytic solubilization oftrash fish and processing carcass waste in a simple shell-in-tubeheat exchange system was investigated. The nutritional and chemicaleffects of processing variables were evaluated.An exogenous source of proteolytic enzymes (albacore tunaviscera, Thunnus alalunga) yielded a linear increase in the rate ofthe proteolytic hydrolysis of ground whole Pacific hake (Merlucciusproductus) up to 40% in the reaction mixture at 55°C. At 60°C optimumtemperature for proteolytic hydrolysis was established with a20% viscera 80% hake reaction mixture. Acidification of hake with85% H₃PO₄ greatly accelerated proteolytic hydrolysis yielding anoptimum between pH 3.6 and 3.7. The optimum pH for liquificationbased upon the viscometric properties of reaction mixtures variedfrom that for hydrolysis and was between 4.3 and 5.1.The chemical characteristics of the proteolytic solubilizationof hake at 55°C was determined. The total nitrogen and free aminoand tyrosine equivalent content of trichloroacetic acid (TCA), waterand sodium dodecylsulfate (SDS) fractions of reactions containing 0,2 and 4% 85% H₃PO₄ were determined at various times over a two hrperiod. With accelerated reactions (2 and 4% 85% H₃PO₄) the rate ofhydrolysis was greatly reduced after 30 min. Under less than optimumpH conditions (0% 85% H₃PO₄) proteolytic hydrolysis proceededin a linear fashion throughout the two hr period. The relationship betweenthe quantities of chemical indices in the TCA and water fractionssuggested that the majority of the proteolytic action yieldedamino acids and short peptides. The total nitrogen content of the SDSsoluble fraction inferred that very little of the protein that was notSDS soluble was being solubilized.The protein efficiency ratio of samples of hake reacted at 55°Cin the presence of 0, 2 and 4% (wt/wt) 85% H₃PO₄ at 30, 60, and120 min was determined to assess the nutritional effects of proteolyticsolubilization. Proteolytic action reduced protein quality to adegree related directly to the level of acid accelerated proteolyticaction. Full reduction in quality was accomplished at the end of 30min for reaction mixtures containing 0 and 2% acid in comparison toa raw hake control; no reduction was observed between 30 and 120min. In addition to the initial reduction in quality within the first 30 min of reaction, mixtures containing 4% acid were significantly reducedbetween 30 and 120 min. Conversion of native protein tonutritionally less utilizable amino acids and peptides probably playedthe major role in reducing protein quality in reaction mixtures containing0 and 2% acid. The time dependent reduction in proteinquality for the reactions containing 4% supports the destruction ofamino acids, probably tryptophan, at this higher level of acidity.

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