摘要:

ABSTRACTHeat treatment of soymilk was studied in the conventional batch boiling process and under High Temperature‐Short Time (HTST) conditions. Reduction in total trypsin inhibitor was assayed enzymatically, and individual inhibitors, the Kunitz and the Bowman‐Birk inhibitor, were assayed by ELISA technique. Standard first‐order reaction kinetics and thermodynamics were applicable for inactivation, and results indicated that the mechanism was not protein unfolding, because entropy changes were zero or negative. The two inhibitors were inactivated at the same rate around 137°C. Therefore, a simple first‐order kinetic model which gave a good, slightly conservative estimate of residual anti‐trypsin activity under HTST conditions could be e

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14173.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTHeat‐denatured whey protein isolate was hydrolyzed with trypsin, α‐chymotrypsin, Alcalase or Neutrase to 2.8, 4.3, 6.0 or 8.0% degree of hydrolysis. Hydrolysates were fractionated by ultrafiltration and freeze‐dried. Protein content of retentates showed little variation but permeates differed with enzyme. Surface hydrophobicity increased with hydrolysis but was not linear except for α‐chymotrypsin. Ultrafiltration increased solubility and the permeates and retentates had better solubility than hydrolysates. Retentates had higher emulsifying activity index than hydrolysates while permeates did not form stable emulsions. Permeates formed stable foams but hydrolysates and retentates showed poor foaming characteristics. Specificity of the enzyme, and degree of hydrolysis influenced the functional properties of the peptides. Fractions generated by trypsin, at all levels of hydrolysis generally had higher solubility, emulsifying properties and foaming properties. Permeates from Alcalase hydrolysis had the best foam capacity but low foam

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14174.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTFreeze‐dried WPC, containing 35 and 75% protein were manufactured by pretreating whey with calcium chloride and heat. These and commercial WPC were subjected to proximate analysis and lipid classes, phospholipid classes, free fatty acids (FFA), and monoacylglycerols (MAG) composition were determined. Solubility, thermal, foaming, and emulsifying properties of the WPC were studied. Pretreatment increased calcium and phosphorus contents and decreased the contents of all other minerals. The pretreatment had no effect on solubility, denaturation enthalpy, and onset temperature of denaturation of WPC. These values were comparable to those of commercial WPC. Foaming capacity and emulsion stability were unaffected, but foam stability increased and emulsifying capacity decreased due to pretreatment. Overall, total lipids and lipid class contents of experimental WPC were too low to affect surface properties of WP

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14175.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe gel strength of ovalbumin mixed with α‐lactalbumin (α‐La) was determined after heating at 80°C for 15 min at pH 7.0 Gel strength of the mixture of 4%α‐La and 4% ovalbumin was two times that of 8% ovalbumin. Modified α‐La at Cys6‐Cys120 (3 SSα‐La) had low enhancement effects on ovalbumin gelation. Competitive ELISA using monoclonal antibody to α‐La showed decreased binding reactivities after heating α‐La with ovalbumin at specific concentrations. The decrease of total SH groups in the gel mixed with 3SS α‐La was much less than when mixed with α‐La. A disulfide bond of Cys6‐Cys120 in α‐La contributed to interactions between ovalb

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14176.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThere have been increasing needs for biosensing in the food industry because it is accurate, rapid and efficient. A needle‐type L‐lactate sensor with a three‐layer membrane system which uses lactate oxidase as the biological component was prepared. The sensor had an optimum pH around 9–10 and an optimum temperature at 45 C. The current response was stable over 40 days and specifically responded to L‐lactic acid. The sensor gave accurate L‐lactate measurements in kimchi and yogurt of 187.4 ± 4.1 and 734.1 ± 34.5 mg/dL, similar to those of a spectrophotometric

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14177.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTA cheese extract and a standard solution with a mixture of peptides and amino acids were used to evaluate the separations of reverse‐phase HPLC with alternative mobile phases to be used in conjunction with sensory evaluation. Acceptable resolution of components was observed when acetonitrile was replaced with absolute ethanol and trifluoroacetic acid was replaced with food‐grade hydrochloric acid. The average hydrophobicity and molecular weight of the peptides and amino acids were used to construct a linear regression equation with corrected retention times. Suspected bitter compounds were not confined to any one section of the chromatogram based on the established regression mo

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14178.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTProteolysis during ripening of full‐fat and low‐fat Cheddar cheese was investigated by applying reverse‐phase HPLC to the pH 4.6 water‐soluble N fraction of cheese. The separated N compounds were divided into four MW ranges. The number of separated peaks and the amount of N compounds separated in each of the MW ranges increased with ripening time. Significant within‐cheese, within‐variety, and between‐varieties differences in the amounts and proportions of N compounds with different MW were observed as related to ripening time. Reverse‐phase HPLC of the pH 4.6 water‐soluble N fraction of cheese can provide detailed quantitative information on proteolytic activitie

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14179.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTAntistaling additives—distilled monoglycerides (MGL), diacetyl tartaric ester of monodiglycerides (DATEM), sodium stearoyl lactylate (SSL), carboxymethylcellulose (CMC), hydroxypropylmethylcellulose (HPMC) and fungal α‐amylase—were studied for effects on rheological and fer‐ mentative properties of white/whole wheat bread doughs, made following straight/sour dough processes. A fractionated factorial design (L32) was used to evaluate single additive effects and interactions. Single addition of DATEM, followed by SSL, α‐amylase and hydrocolloids improved oven rise and final volume. In presence of DATEM, synergistic (MGL) and antagonistic (SSL) effects of additional emulsifiers were found on gassing power. SSL was the only effective conditioner for enhancement of mixing properties. Dough plasticity was negatively affected by MGL addition and by CMC/HPMC in white/whole flours respectively. Some combinations resulted in detrimental dough handling

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14180.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTAcid urease derived from Lactobacillus fermentum was applied to reduce ethyl cthe target level (90 μg/L). However, complete prearbamate (EC) formation in California sherry production. Commercial sherry and sherry base were treated with urease under different conditions. Amounts of urea were determined and EC amounts were monitored by gas chromatography. Urea removal by acid urease reduced EC formation during the baking process and effectively maintained EC concentrations below vention of EC was not achieved because of precursors other than urea

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14181.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTPectinesterase, lipase, polyphenol oxidase, lipoxygenase, peroxidase, lactoperoxidase, phosphatase and catalase have been examined at distinct conditions within a pressure range of 0.1 to 900 MPa, temperatures from 25°C to 60°C, pH 3 to 7, and time of treatment of 2 min to 45 min. Results in model buffers made it possible to rank the enzymes according to their pressure induced inactivation in the following order: lipoxygenase, lactoperoxidase, pectinesterase, lipase, phosphatase, catalase, polyphenol oxidase, peroxidase. A combination of pressure with moderate temperature increased the degree of enzyme inactivation. Pressure treatment of real food systems showed a protective effect of food ingredients on the pressure inactivation of most enzymes evaluated. For example sucrose protected pectinesterase from inactivation by pressure while lactoperoxidase and lipoxigenase were as stable in milk as in buffe

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14182.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY