摘要:

ABSTRACTIt is widely accepted that viscometric assays are the most sensitive methods for evaluation of endoglucanase activities, because of the preferential attack of these enzymes on internal bonds of the substrate. However, due to the high sensitivity of the disodium 2,2′‐bicinchoninate assay, we could measure, in a onestep method, the initial stages of the degradation of cellulose derivatives by endo‐1,4‐β‐D‐glucanases, by determining the reducing end‐groups released. We report the applicability of the method for the determination of activity, and the Kmfor the endoglucanase‐I from Trichoderma reesei. This assay can be extended to the evaluation of reducing groups released by the action of many other carbohydrases, either with endo‐ or

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1993.tb00463.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTGrass shrimp(Penaeus monodon)at prerigor stage were frozen at rates ranging from 3.41 to 16.1 cm/h by using an air blast freezer at –35C or a liquid nitrogen freezer at – 80, – 100 and – 120C. Immediately after freezing, the spacing between muscle fiber bundles was larger (21.3 ± 5.7 μm) in shrimp frozen at 3.4 cm/h than in shrimp frozen at 8.6 ∼ 16.1 cm/h (6.0 ± 0.6 to 8.8 ± 1.1 μm, respectively). The spacing between fibers increased during frozen storage at – 20C and remained different for slow and fast frozen samples within 4 weeks. The lysosomal fraction from fresh shrimp had more cathepsin D‐like activity (187 units/mg protein) than that from shrimp frozen at 10.2 cm/h (179 units/mg protein) and at 3.4 cm/h (86 units/mg protein). During frozen storage at – 20C the cathepsin D‐like activity of intact lysosomes decreased and was negligible after 4 weeks. The solubility of muscle protein in 0.6 M KCl was not consistently different in samples frozen by different methods and stored at – 20C for 4 weeks. Liquid nitrogen freezing produced frozen shrimp of higher muscle integrity than air blast. But the differences disappeared after on

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1993.tb00464.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTFermented and nonfermented cassava(Manihot utilissimaPohl) starches from Colombia and Brazil were studied. The DSC thermograms obtained at high water contents (water:starch 3.1 to 4.2) showed that starch fermentation decreased both the temperature of gelatinization (Tmax) and that of final gelatinization. No significant differences were found between the enthalpies of gelatinization of fermented and non‐fermented starches. Differences in ΔH corresponding to the first endothermic transition of fermented and nonfermented samples were detected at low water contents (water:starch 1.0 to 0.4). Pastes obtained with nonfermented starches were more viscous than those corresponding to fermented samples. This behavior could be related to the greater solubility of the fermented samples, leading to a smaller size of hydrated granul

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1993.tb00465.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTA substantial number of enzymes have potential applications in dairy technology but most are not commercially viable, at least at present. In this review, the principal applications of proteinases (rennets for cheese manufacture, acceleration of cheese ripening, modification of the functional properties of milk proteins, preparation of nutritionally and physiologically active peptides), lipases (mainly in cheese ripening) and lysozyme are discussed.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1993.tb00466.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTThe fermentative production of propionic acid in cod gurry hydrolysate containing from 2.5 to 4.0% glucose by strains ofPropionibacteriumwas studied. Yields of 1.3 to 1.7% propionic acid plus 0.52 to 0.71% acetic acid with resulting pH values of 4.2 to 4.0 were achieved with steam sterilized hydrolysates after 192 h of incubation. Concentrations of 1.0% propionic acid or more at a pH value at or near 4.0 are considered sufficient to achieve permanent preservation. The rates of the fermentations and resulting rates of reduction of pH were notably slow due to generation times of 6 h or longer. This slow rate of fermentation can be expected to allow the growth of contaminating spoilage organisms during the first 24 to 48 h before inhibitory levels of propionic and acetic acids are produced. The preservation of hydrolyzed gurry by direct propionic acid fermentation is therefore not feasible at this time unless the rate of fermentation is significantly increased.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1993.tb00467.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Book reviewed in this article:FOOD TAINTS AND OFF‐FLAVORS. Edited by M.J. Saxb

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1993.tb00468.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY