摘要:

ABSTRACTBarhee and Zahdi dates(Phoenix dactylifera)contain polyphenol oxidase (PPO) at all maturity stages. The highest PPO activity is present in the medium green and late yellow stages of Barhee and Zahdi dates, respectively. The extracts of medium green stage of Barhee dates contained proteolytic activity. Four PPO forms were purified to homogeneity by acetone precipitation and DEAE‐cellulose chromatography. The total fold purification was 8.0, 10.0, 12.5, and 15.0 with 6.7, 0.7, 2.2, and 2.7% recovery of PPO activity. A single PPO form was observed when 1.0mM of phenylmethylsulfonyl chloride (PMSC) was used in extraction solutions. However, only a single PPO form was observed in Zahdi dates and purified 13.1 fold with 7.7% recovery of activit

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1988.tb00375.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTPurified polyphenol oxidase (PPO) from Barhee and Zahdi date cultivars had a molecular weight of 17,500 and 17,000, respectively, as determined by exclusion gel chromatography. The enzyme possessed activity on o‐diphenols but not on monophenols or m‐diphenols. The highest activity was on catechol with Kmof 3.5 and 8.75 mM for PPO from Barhee and Zahdi dates, respectively. PPO from the two cultivars showed optimal pH for activity and stability around 6.0 and 7.0, respectively. The enzyme was completely inactivated when incubated at 70°C for 10 min. Activation energy for conversion of substrate to product was 3400 and 3600 cal/mole for PPO from Barhee and Zahdi dates, respectively. However, the activation energy for denaturation was 28000 and 27000 cal/mole for the enzyme from Barhee and Zahdi cultivars, respectively. Ascorbic acid, oxalic acid and sodium metabisulfite caused non‐competitive inhibition for PPO activity, while sodium chloride was an uncompetitive inhibitor. Sodium metabisulfite was the most potent inhibitor with Ki values of 0.025 and 0.030 mM for PPO from Barhee and Zahdi dates, respec

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1988.tb00376.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTSilage prepared solely from ground hake frames and ground entrails plus frames (1:4, w/w) acidified to a pH of 4.0 with phosphoric acid and with the addition of 0.1% potassium sorbate underwent enzymatic liquefaction after several weeks storage at 20°C without microbial development. With silage prepared with frames and phosphoric acid but without potassium sorbate, oxidative surface yeasts were the only spoilage microorganisms. With silage prepared from entrails and frames with just phosphoric acid a heavy surface growth of both molds and oxidative yeasts developed

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1988.tb00377.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTThe amino acid and fatty acid compositions of the seeds of the wild Nigerian legumeCentrosema pubescencehave been determined, along with proximate composition and levels of selected inorganic ions. Total unsaturation of the lipid extract amounted to about 59% with oleic acid being not only the dominant unsaturated fatty acid, but also the overall single dominant fatty acid. The first limiting amino acid was methionine. Lysine was present at a level higher than in the reference egg protein. The proximate composition was characterized by high protein and crude fiber contents (21 and 9.7%, respectively) and by low crude fat (about 2.3%) and ash contents (about 3.5%). Varying levels of selected inorganic ions were also detected.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1988.tb00378.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTProteases in acetone powder prepared from milkfish (Chanos chanos) viscera were extracted with deionized water and purified by ammonium sulfate fractionation, Sephadex G‐75 gel filtration, repeated DEAE‐Sephadex A‐50 and CM‐Sepharose CL‐6B chromatography. Four fractions with caseinolytic activity, named A, B, C and D, were obtained from CM‐Sepharose CL‐6B and DEAE‐Sephadex A‐50 chromatography. The four proteases were purified to electrophoretic homogeneity. Substrate specificity studies indicated that proteases A and B were carboxypeptidase A‐like and chymotrypsin‐like enzymes, respectively; C and D were trypsin‐like enzymes.ABSTRACTThe optimal temperatures of proteases A, B, C and D for hydrolysis of casein were found to be 60, 60, 55 and 60°C, respectively. The optimal pH of protease A for hydrolysis of hippuryl‐L‐phenylalanine was 9.0, B for hydrolysis of acetyl‐L‐tyrosine ethyl ester was 8.0, C and D for hydrolysis of tosyl‐L‐arginine methyl ester was 8.0. The temperatures which inactivated 50% of enzymes in 5 min were 20°C for protease B; 51°C for protease C; 56°C for protease A; and 61°C for protease D. The molecular weights of proteases A, B, C, and D were 14,800, 16,800,

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1988.tb00379.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTActivity of enzymes involved in the biogenesis of lipid‐derived volatiles was assayed in five mango cultivars during ripening. Lipase activity was maximum either at harvest maturity and/or at 1/2 ripe stage depending on the cultivar and declined in later ripening stages. Cvs. Banganapalli, Langra and Totapuri had high relative lipase activity. Lipoxygenase activity increased from harvest maturity until 1/2 ripe stage and then declined. The relative activity was maximum in cvs. Langra and Dasheri. Alcohol dehydrogenase activity increased from harvest maturity to either 1/2 ripe stage and/or 3/4 ripe stage depending on the cultivar and then declined. The aldehyde‐forming activity was high at harvest maturity, decreased a little in 1/2 ripe stage and thereafter declined rapidly. The cv. Alphonso had higher relative aldehyde forming activity during ripen

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1988.tb00380.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY