Fish protein hydrolysate (FPH) prepared from defatted sardine meal by treatment with alkaline protease was tested for inhibitory activity against angiotensin I converting enzyme (ACE) and for hypotensive effects on spontaneously hypertensive rats (SHR). FPH at 0.18 mg protein/ml concentration provided 50% inhibition against ACE, and FPH was more effective compared with
In order to develop a protein material that is soluble and highly nutritious, fish protein hydrolysates (FPH) were prepared from defatted sardine meal by enzymic treatment using various proteases including three alkaline, two neutral and three acid ones.Ability to solubilize protein was compared among these proteases, and tryptophan content, bitterness and molecular weight distribution of each FPH were evaluated as indicies to quality.The results showed that all the alkaline proteases had higher ability to solubilize protein compared with neutral and acid ones. FPH prepared with alkaline proteases had higher tryptophan content and lower molecular weight than those prepared with neutral and acid ones. Especially, FPH prepared with alcalase or actinase, which were alkaline proteases, had weaker bitteness than other FPH.Furthermore, it was found that FPH prepared with alcalase followed by treatment with synthetic adsorbents or peptidases had much weaker bitteness.
The nutritive values of enzymatic fish protein hydrolysate (FPH) from defatted sardine meal were examined. The amino acid score of the FPH relative to the FAO/WHO pattern (1973) was calculated to be 100, showing that FPH is excellent protein nearly equal to the original meal.The nutritive values of FPH obtained in an experiment using growing rats were as follows: protein efficiency ratio (PER) 3.2, net protein ratio (NPR) 5.2, biological value (BV) 86, true digestibility (TD) 99%, net protein utilization (NPU) 85. These results show that FPH has high nutritive values, almost equivalent to defatted sardine meal and somewhat superior to casein, but slightly lower than an amino acid mixture corresponding to FPH. Furthermore, blood components (12items), liver and liver fat weights were measured in an animal experiment, and these values for animals fed the FPH appeared normal.
Enzymatic fish protein hydrolysates were prepared from defatted sardine meal (FPH-S) and cod meal (FPH-C).Their volatile components were analyzed by GC and GC-MS. GC-MS analy sis of the head space gas identified 13 components in the defatted sardine meal, 8 in FPH-S, 12 in the cod meal and 5 in FPH-C.The volatile components were decreased in kind and content through the FPH preparation process.GC and GC-MS analyses of the ether extract identified 51 components in FPH-S and 64 in FPH-C.Major components in FPH-S were 4-methylpentanoic acid, 2-methylbutyric acid, butyric acid, caproic acid, isobutyric acid, valeric acid and 2-nonenal, and those in FPH-C were hexadecanal, palmitic acid, 2-methylbutyric acid, butyric acid, caproic acid, valeric acid and hexanal.Acids and aldehydes were present in fairly large quanti ties in the volatile components.They had a generally unpleasant odor and many had low sen sory threshold values, and they seemed to be the principal odor component of FPH.
Fishy odor was lessened when fish protein hydrolysate (FPH) aldehydes were treated with resting yeast strains of Saccharomyces or acetic acid bacteria (Acetobacter and Gluconobacter) cells at acidic pH. A very small but detectable amount of aldehydes still remained after treatment with these yeasts or acetic acid bacteria, and alcohol dehydrogenase (ADH) or aldehyde dehydrogenate (ALDH), suggesting that the remaining aldehydes interacted with protein. It seemed that the contribution of the bound aldehydes to fishy odor was small. These results showed that it is possible to develop fish protein hydrolysates with low odor levels.
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