摘要:

The aroma complex of cranberry contains benzaldehyde, benzyl alcohol and benzyl benzoate as major components, and [7‐14C] benzoic acid was converted into benzaldehyde, benzyl alcohol, benzyl benzoate, and minor amounts of other benzyl and benzoate esters in tissue slices of ripe cranberry. Hydrolysis of the benzyl benzoate indicated that label was about equally distributed between benzoic acid and benzyl alcohol. [7‐14C] benzaldehyde was converted in tissue slices into benzyl alcohol and benzyl benzoate, and hydrolysis of the ester indicated that only the alcohol moiety was labeled. Incubation of cranberry tissue slices with [7‐14C] benzyl alcohol yielded primarily benzyl benzoate, and only the alcohol portion of the ester was labeled. All biosynthetic products were identified by radio chromatographic analysis and by preparation of derivatives, and the direct incorporation of precursors into biosynthetic products was demonstrated by chemical degradation studies. These results strongly suggest that, in the biosynthesis of benzyl benzoate, benzoic acid is first reduced to benzaldehyde, followed by reduction of the aldehyde to benzyl alcohol which is subsequently esterified. None of the aforementioned transformations of [14C] benzoic acid and its derivatives could be demonstrated in tissue slices from unripe (green) cranberry, suggesting that development of the ability to synthesize volatile benzenoid compounds is associated with rip

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00190.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Kluyveromyces fragilis β‐galactosidase purified to electrophoretic, chromatographic and immunochemical homogeneity was used. The enzyme specifically required potassium ions for stability; MnCl2increased the stability. The enzyme was maximally stable at pH 6.5 to 7.5; stability was markedly less at pH's below 6.5 and above pH 8.5 at 37°C. Temperature denaturation followed first order kinetics with an activation energy for denaturation of 56 kcal/mol. Maximum activity was achieved in the presence of 5mM KCl. In potassium phosphate buffer, the enzyme was further activated by Mn2+, Mg2+, Co2+and Zn2+; Mn2+, at 0.1 mM, gave the highest activation. None of these ions activated the enzyme in Tris buffer and>0.1 mM Zn2+caused complete loss of activity. Activity was completely inhibited by ethylenediaminetetraacetate and partially restored by addition of MnCl2. p‐Chloromercuribenzoate caused rapid loss of activity which could be restored by dithiothreitol. Iodoacetamide, N‐ethylmaleimide and sodium tetrathionate did not inactivate the enzyme. The enzyme was specific for β‐galactosides. Km's for o‐nitrophenyl β‐D‐galactopyranoside and lactose were 2.72 and 13.9 mM, respectively, at pH 6.6 D‐Galactono‐1, 4‐lactone was a good competitive inhibitor (Ki=0.17 mM). pH optimum for hydrolysis of o‐nitrophenyl β‐D‐galactopyranoside was 6.2–6.4. Vmaxfor this substrate was dependent on two ionizable groups of pKaof 6.13 and 6.51 while Vmax/Kmwas dependent on two ionizable groups of pKaof 6.39 and 7.23. Activation energy for hydrolysis of o‐nitrophenyl β‐D‐galactopyranoside at pH 7.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00191.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

A study was made on the distribution in potato tubers of two lipiddegrading enzymes, lipolytic acyl hydrolase (LAH) and lipoxygenase (LOX), and of peroxidase (POD). The LAH showed higher activity at the stem end than at the bud end of tubers whereas LOX (and to a lesser extent POD) were more concentrated in the cortical tissues outside the vascular ring. A preliminary study of heat inactivation of the enzymes in situ indicated a decreasing resistance to inactivation in the order POD>LOX>LAH. The possible relevance of these results to potato processing is discussed.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00192.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Reproducible determinations of cell wall uronic acid content are obtained by first dissolving wall samples in sulfuric acid and then performing assays on aliquots of the cell wall solution. The colorimetric assay utilizing m‐hydroxydiphenyl is recommended because of its low background readings in the presence of large quantities of neutral sugar

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00193.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

A study was conducted to evaluate the mode of calcium‐binding to four food protein sources. Following calcium‐binding at pH levels of 7, 8, 9, 10 and 11, samples were evaluated for changes in the approximate molecular and subunit weight and in the isoelectric point of the soluble proteins. Data presented show that there were subunit interactions during the various pH incubations. This was especially true for the soy and wheat gluten proteins. Isoelectric points were found to decrease for soy, wheat, and leaf proteins after calcium bind

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00194.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Three α‐amylase inhibitors were purified to homogeneity from Anza wheat (Triticum aestivum var. Anza) by extraction with 70% ethanol, ammonium sulfate fractionation and column chromatography on DEAE‐cellulose, CM‐ceillulose and Sephadex G‐50. Homogeneity was determined by disc gel and isoelectric focusing electrophoresis and by sedimentation equilibrium centrifugation. The inhibitors are designated 0.19, 0.28 and 0.55 on basis of their relative electrophoretic mobilities on polyacrylamide gels. The 0.19, 0.28 and 0.55 inhibitors had molecular weights of 24,000, 18,500 and 30,000 by polyacrylamide gel electrophoresis with different gel concentrations while the former two were 29,000 and 14,500 by sedimentation equilibrium centrifugation, respectively. The molecular weight of the 0.55 inhibitor was not determined by centrifugation. The isoelectric points were 5.9, 5.2 and 4.2 for the 0.19, 0.28 and 0.55 inhibitors, respectively. The three inhibitors had similar amino acid compositions but differed significantly in amounts of lysine, arginine, histidine, alanine, valine and phenylalanine. The 0.19 inhibitor was active against human salivary and hog pancreatic α‐amylases but inactive against Bacillus subtilis and Aspergillus oryzae α‐amylases. The 0.28 inhibitor had very weak activity against only human salivary α‐amylase. The 0.55 inhibitor had activity against only human salivary α‐amylase. The 0.55 inhibitor appears to differ from all previously reported wheat α‐amylase inhibitors while the 0.28 inhibitor (protein) is unique in having essentially

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00195.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Book Reviews in this article.Industrial Microbiology, Brinton M. Miller and Warren Litsky, Editors.Practical Electron Microscopy for Biologists, 2nd Edition, Geoffrey A. Meek.Plant Biochemistry, 3rd Edition, James Bonner and Joseph E. Varner, Editors.Phenolic, Sulfur and Nitrogen Compounds in Food FlavorsGeorge Charalambous and Ira Katz, Editors.Microbial and Plant Protoplasts, J. F. Peberdy, A. H. Rose, H. J. Rogers and E. C. Cocking, Editors.The Enzyme Molecule, W. Ferdinand, Editor.Enzymes in Food and Beverage processing, Robert L. Ory and Allen J. St. Angelo.Biochemistry of Foods and the Biocatalysts, I. I. Shahied.Enzyme Kinetics–The Steady State Approach, Paul C. Enge

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1978.tb00196.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY