摘要:

ABSTRACTThe Merchoquant test strip and a rapid, enzymatic method were evaluated for the quantitation of formaldehyde (HCHO) in neutralized perchloric acid (HC104) extracts of fish muscle. Compared with the standard colorimetric Cochin and Axelrod (1959) modification of the Nash reagent method (1953), the nonglutathione dependent formaldehyde dehydrogenase (EC 1.2.1.46) method based on that of Yasuhara et al. (1982) for creatine was faster and less affected by interferences. The enzyme method resulted in lower HCHO values than did the modified Nash method for the gadoid pollock, haddock and cod samples while the semi‐quantitative Merchoquant test strip resulted in positive readings for only one cod sample. Seventy‐nine HC104fish extracts analyzed by the enzyme and modified Nash procedures showed a species dependent correlation between the two methods, with slopes of 0.847, 0.321, 0.436, 0.519 for sole, pollock, haddock and cod, respectively. The HCHO content of the samples ranged between 0.4 and 75 μmoles%. Standard addition evaluation of the accuracy of the formaldehyde dehydrogenase method compared with the modified Nash procedure on three samples also resulted in species dependent slopes. Nongadoid sole samples showed the greatest deviation while cod was the only species where the modified Nash method resulted in HCHO values lower than those attained with the enzyme method. The detection limit of the formaídehyde dehydrogenase method was 0.3 μ

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1988.tb00361.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTThe inhibition of a purified β‐galactosidase from “Spartan” apples by flavonoids and related compounds has been studied with a fluorimetric assay using the substrate 4‐methylumbelliferyl β‐D‐galactoside. Certain flavonoids, flavonoid glycosides, phenolic acids, and polyphenols (quercetin, fustin, rutin, p‐coumaric acid, and catechol) gave classical noncompetitive inhibition at moderate substrate concentrations. Others (kaempferol, chlorogenic acid) gave nonlinear Dixon plots. The best inhibitors were flavones. In general, the degree of inhibition increased with the degree of hydroxylation and glycosylation of the phenol. Correlation of the structure of these substances with the observed inhibition suggests that the trans‐3‐(4‐hydroxyphenyl)‐propenoyl group, common to 4′‐hydroxyflavones and p‐hydroxyphenolic acids, is impor

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1988.tb00362.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTThe actinidin activity in kiwifruit increased 3‐fold after 3 weeks postharvest ripening at 5°C with a 15% decrease in specific activity. Actinidin activity is highest in the pulp of ripe fruit at 27,600 U/kg fruit. The thiol protease actinidin from kiwifruit was extracted and purified 26‐fold to a specific activity of 57 U/mg with Km= 91 μM and kcat= 101 s−1towards N‐α‐CBZ‐lysine p‐nitrophenyl ester at

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1988.tb00363.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTAmaranth lectin from Amaranthus cruentus seeds was isolated, purified and partially characterized. The purification method used was based on its ability to interact with fetuin. Effects of temperature, pH and buffers and concentration were determined by measurement of lectin hemagglutination activity. Amaranth lectin biological activity was best maintained at temperatures between 4 and 30°C and pH's above or below 5. It was possible to store amaranth lectin at 4°C in acetate buffers, pH 4.8, for prolonged periods and to concentrate it 10‐fold by ultrafiltration with only 18% loss of activity. A subunit molecular weight of 32,500 daltons was determined by SDS‐PAGE for amaranth l

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1988.tb00364.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTChanges in the thiol groups were determined in the mantle meat of the squid (Illex argentinus) after heating at 98°C for 45 min. The contents of ‐SH groups in the raw mince was about 90 μmoles/g protein and after heating decreased by about 30%. The total contents of ‐SH groups after reduction of disulfide bridges by NaBH4was 120 μmoles/g protein in the raw sample and did not change significantly in the cooked meat. After 45 min of cooking the mince contained about 18 times more dimethylamine and only twice as much free formaldehyde as the raw samples. The correlation coefficients between free ‐SH groups contents and the solubility, degree of thermal coagulation of proteins as well as the water holding capacity of the meat were +0.936, ‐0.947, and +0.880, re

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1988.tb00365.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Book reviewed in this article:Recent Advances in the Chemistry and Technology of Fats and Oils Edited by R.J. Hamilton and A. Bhati.Naturally Occurring Carcinogens of Plant Origin: Toxicology, Pathology and Biochemistry. Edited by I. Hirono.Warmed‐Over Flavor of Meat. Edited by Allen J. St. Angelo and Milton E. Bailey.Statistical Procedures in Food Research. Edited by J.R. Piggott.Developments in Food Preservation. Edited by Stuart Thorne.Water Activity: Theory and Applications to Food. Edited by L.B. Rockland and L.R. Beuchat.Food Biotechnology ‐ 1. Edited by R.D. King and P.S.J. Chettam.Corn: Chemistry and Technology. Edited by S.A. Watson and P.E. Ramstad.PIGMENTS IN FRUITS by Jeanna Gr

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1988.tb00366.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY