摘要:

ABSTRACTAlcohol insoluble solids (AIS) from jicama and Chinese water chestnut were isolated and analyzed to elucidate the similarity in texture between these two crispy vegetables. Pectins were the largest AIS component of both vegetables, comprising approximately 50% of AIS. Further analysis showed a similar composition of water soluble, chelator soluble, and alkaline soluble pectins in both jicama and water chestnut. Water chestnut contained a much larger hemicellulose component and a correspondingly smaller cellulose and lignin component than jicama. Fractionation of the hemicellulose and examination of molecular weight distribution and neutral sugar composition of various fractions revealed major differences between the two vegetables. These differences in structure and composition of hemicellulose may explain the observed differences in textural properties of these two crispy vegetables.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00418.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTThe effect of lipophilization on the structure‐function and stability ofMucor mieheiaspartyl proteinase (MMP) was examined. Modification of approximately 3 and 2 e‐amino groups in MMP with caproyl and myristoyl chloride, respectively, decreased the proteolytic activity (PA) and milk‐clotting activity (MC) of the enzyme; differential reduction in these activities was manifest as increased MC/PA. Lipophilized MMP also showed significantly higher thermal, kinetic and conformational stability. Interaction between fatty acids and proteinase appeared to be ionic in nature, as evidenced by increased relative electrophoretic (cathodic) mobility. Attachment of the fatty acid ligands was shown to increase both aliphatic and aromatic hydrophobicity of MMP as indicated by the hydrophobic fluorescent probes cis‐parinaric acid and l‐anilino‐8‐naphthalenesulfonate. Lipo‐philization‐induced changes in functional properties were accompanied by altered secondary and tertiary structure as reflected by far‐UV and near‐ UV circular dichroism spectra, respectively. Results of this study suggesed that high MC/PA may be related to high hydrophobicity in

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00419.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTDialysis, preparative isoelectric focusing (IEF) and gel filtration were employed to obtain final enrichments of 2.2‐fold and 1.4‐fold forMucor miehei (CBS 360.75) proteinase (MMP) andM. pusillus(var. Lindt) proteinase (MPP), respectively, from partially purified sources. Recovery of total activity (percent yield) of MMP was 38% following preparative IEF and 6.7% after gel filtration. Percent yield of MPP was 61% following preparative IEF and 15% after gel filtration. Preparative IEF fractionation with a lowpH (3–5) ampholyte produced most of the increase, and partitioned brown pigments into fractions of pH 2.0 to 3.5. The protocol produced proteinases of high purity as indicated by SDS‐PAGE. The isoelectric point, molecular weight, extinction coefficient and amino acid composition of MMP and MPP proteinases were in agreement with previously determined values. Secondary structure analysis confirmed previous findings that these enzymes contain a high proportion of β‐sheet structure. Purifications starting with 4 to 5 g of crude partially purified MMP preparation (at least 50% NaCl) yielded between 18 and 28 mg of purifi

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00420.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTThe possible role of phytic acid as a chelating agent in the softening of fresh beans during cooking was examined. Its diffusion out of the grain of two bean varieties was determined during the cooking process. The softening rate was five times higher in the Michigan variety than in the Ojo de Cabra variety. During cooking the phytic acid did not diffuse out of the grain, and no evidence of a change in its solubility was found in either bean variety. These data indicate that phytic acid probably is not a chelating agent during bean thermal softening.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00421.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTWhen 2, 3‐dihydroxybenzoic acid (2, 3‐DBA) is acted upon by mushroom tyrosinase, a yellow intermediate, 2, 3‐DBA‐o‐quinone, characterized by a peak at 415 nm, is the first product detected. 2, 3‐DBA‐o‐quinone gives rise to a “final blue product” (λmax = 230, 410, 620 nm), and to “soluble oxidation product(s)” (λmax = 275–280, 350–360 nm).Kinetic data (assayed spectrophotometrically and polarographically) obtained when different concentrations of 2, 3‐DBA were oxidized by a fixed amount of mushroom tyrosinase, deviated from classic Michaelis‐Menten kinetics.Reduction of the “final blue product” with ascorbate resulted in the loss of the blue chromophore at 620 nm and the concomitant appearance of a “yellowish reduced final product.” The “yellowish reduced final product” could be reoxidized with either mushroom tyrosinase or with NaIO4 to the “final blue product,” indicating that the latter has carbonylic

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00422.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Book reviewed in this article:Biotechnology and Food Safety.D.D. Bills and S. Kung.Lipid Biochemistry: An Introduction.M.I. Gurr and J.L. Harwood.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00423.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1991.tb00417.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY