摘要:

ABSTRACTLegumes provide an important part of the world's protein requirements, as well as other nutrients, but they are underutilized as food. A major factor limiting expanded consumption is storage induced textural defects that prolong cooking time and demand correspondingly higher energy requirements for preparation. These defects, including the hard‐to‐cook phenomenon and hardshell, are initiated by structural and compositional factors but can be at least partially controlled by storage and processing conditions. Structural components implicated include seed coat, cell walls, middle lamella, starch granules and membranes while, compositionally, proteins, carbohydrates, phytate, polyphenols and lignin may also be important. Methods of texture measurement of legumes, including mechanical, physical and sensory properties are reviewed. The most commonly held hypothesis for the mechanism of the hard‐to‐cook defect states that beans fail to soften after exposure to high temperature and humidity storage because the increased water activity potentiates phytase which hydrolyzes phytate, rendering it no longer capable of chelating the Ca++and Mg++ions of the middle lamella and, hence, undissoluble. More recent evidence, however, provides potential roles for lignification, starch gelatinization and perhaps other mechanisms depending upon conditions. The possibility of a nonenzymatic as well as an enzymatic route is raised and thoughts presented on a course of action for future r

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1985.tb00355.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTThe yeast Candida macedoniensis produces constitutively an extracellular pectinolytic enzyme with a high maceration activity; the culture filtrate is free from foreign enzyme activity. The enzyme formation is optimal under strictly anaerobic conditions with N2gassing.The culture medium for optimal enzyme recovery is a nutrient solution containing 1% yeast extract, 2% peptone and 10% sucrose, at pH 3, 28°C. Characterization of the enzyme showed it to be an endopolygalacturonase. The pH and temperature optima of the enzyme differ for pectic acid cleavage and maceration activity, these being 4.5 and 50—53°C and 2.5 and 40°C, respectively. The enzyme activities could not be separated from one another by protein chemical methods (analytical and preparative isoelectric focussing). Dialysis of the enzyme‐containing culture filtrate did not decrease the enzyme activity. The endopolygalacturonase fromCandida macedoniensis leads to the release of plant cells from the tissue, without destroying the cells by lysing the cell walls. After two hours incubation of the substrate (carrot slices), the tissue mass consisted of cell clumps of up to 15

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1985.tb00356.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTKlebsiella pneumoniaeUH‐2, previously isolated from spoiled skipjack tuna grew rapidly at 37C, 25C and 10C (generation times of 0.64, 0.79 and 4.57 h, respectively) and produced large amounts of histamine at these temperatures. Histamine was found during storage of resting cells at 2C, but growth did not occur. TheK. pneumoniaeUH‐2 histidine decarboxylase system has in situ properties that may contribute to rapid histamine formation in fish tissue. The conversion of histidine to histamine in situ had an apparent Km = 0.98 mM at the optimum pH, 4.0, with ca. 70% of this activity at pH 6. These properties and recent reports of its prominence in fish spoilage suggest thatK. pneumoniaecould play a major role in the formation of histamine in susceptible spec

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1985.tb00357.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTPatatin, the major glycoprotein of potato tubers, had very similar chemical and physical properties whether isolated from cultivar Desiree or from Kennebec. The patatin of each cultivar exhibited copurification with p‐nitrophenyl laurate esterase. However, the esterases from the two sources differed in substrate preference ranging from near equality toward α‐naphthyl laurate to a hundredfold difference toward p‐nitrophenyl l

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1985.tb00358.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Book reviewed in this article:Food Analysis—Principles and Techniques Vol. 3: Biological Techniques, edited by Dieter W. Gruenwedel and John R. WhitakerDEVELOPMENTS IN DAIRY CHEMISTRY—2, Edited by P. F.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1985.tb00359.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1985.tb00360.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY