摘要:

ABSTRACTCompressive creep curves of potato flesh and cheddar cheese were fitted by a modified, four parameter model of the kind J(t) = Ko+ K1t + t/(K2+K3t) where J(t) is the compliance and the K's characteristic constants. The curves were fitted both with and without correction for cross‐sectional area expansion and the nonlinearity of the strain. The fit of the model was comparable to that of the discrete Kelvin‐Voigt model with 4 or 6 constants. The magnitude of the modified model constants was indicative of the general rheological character of the material and the stress dependency of the nonlinear viscoelastic behav

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1985.tb13274.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTAdsorption‐desorption isotherm of pedha, a popular Indian milk sweet, was a smooth sigmoid curve. The equilibrium relative humidity (ERH) of the product was 76% and BET monolayer moisture content 8.73% on dry basis. A negative linear relationship was observed between the logarithm of mold‐free shelf‐life and ERH at 27 ± 1°C in the studied ERH range of 75–92%. Packaging in 100 and 300 gauge low density polyethylene (LDPE‐100 and −300) pouches reduced weight loss, browning and free fatty acid (FFA) development, and retarded deterioration of flavor, odor and acceptability of pedha during storage. Peroxide value was not influenced by LDPE‐packaging. LDPE‐300 was more effective in controlling weight loss, browning and FFA formation than LDPE‐100. Film thickness, however, did not influence the organoleptic attri

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1985.tb13275.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTA method was developed to measure the emulsifying activity and emulsion stability of proteins using a simple apparatus consisting of a glass column with a conductivity cell. A significant correlation was observed between the emulsifying activity and emulsion stability of 10 proteins determined by the conductivity method examined in this paper and the turbidity method of Pearce and Kinsella (1978). These results suggest that the emulsifying properties can be estimated by measuring changes in the conductivity of emulsion. The advantages of the conductivity method are to measure accurately and simply the emulsifying properties of proteins, because this method directly and automatically measures changes in the physical constant (that is, conductivity) of emulsion.

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1985.tb13276.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTPulsed nuclear magnetic resonance was used to monitor the thermophysical transition of aqueous egg albumin dispersion. Gelling, which was manifested by an increase in force required to penetrate the surface of the dispersion, was accompanied by a decrease in T1, the spin‐lattice relaxation time of water protons in the dispersion. There was a high, negative correlation coefficient between gel strength and T1. Apparent rate kinetics of the transition was fist order for changes in T1and zero order for changes in gel strength, with activation energies for the rate constants of 42.62 and 43.68 kcal/mole, respectivel

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1985.tb13277.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTOvalbumin (OV), bovine serum albumin (BSA) and lysozyme (Lys) were added to egg yolk low density lipoprotein (LDL) and the heat‐induced gel formation of LDL‐protein mixture was studied. The gel formation of LDL‐protein mixture was different between the acidic and alkaline pH region; fine stable gels were formed in the alkaline pH region, but weak paste‐like gels were formed in the acidic pH region. The effect of added BSA or OV on the gel strength of LDL was much larger than that of Lys. Scanning electron micrographic observation showed that the microstructures of both LDL‐BSA and LDL‐OV gels were more uniform than that of

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1985.tb13278.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTThe influence of tannin on protein digestibility and quality of black beans was evaluated using an enzyme‐Tetrahymena thermophilabioassay. In vitro digestibility and t‐PER (Tetrahymena‐based PER) were inversely related to tannin content. Bioavailability, expressed byTetrahymenagrowth, of black bean globulin G1in the presence of black bean condensed tannins correlated well (r=0.95) with the in vitro digestibility of the protein. Black bean condensed tannins complexed readily with black bean globulin G1to form insoluble precipitates from pH 2.0 to pH 8.0. Bean tannin‐G1precipitates, at tannin‐to G1ratios of 0.55 or greater, were resistant to pepsin digestion at pH 2.0. Digestion of bean tannin‐G1precipitates was 69–74% at pH 8.0, using a multienzyme system of trypsin, chymotrypsin

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1985.tb13279.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTTwo inhibitors of α‐amylase, I‐1 and I‐2, were purified from the black bean (Phaseolus vulgaris). The rate of complexation with porcine pancreatic α‐amylase was very slow. I‐l required 12 hr and I‐2 6 hr for maximum inhibition at 30°C. The stoichiometry of complexation of α‐amylase with I‐1 was 2:1 and 1:1 with I‐2. Optimum pH for complexation with I‐1 ranged from 4.5 to 5.0 and 5.0 to 5.5 for I‐2 and both were most stable at pH 3.0 to 4.0. An increase in ionic strength of the preincubation buffer from 0.106 to 0.906 enhanced the rate of inhibition 3 fold for both inhibitors. Maltose, a competitive inhibitor of α‐amylase, added to the preincubation solution prevented complex formation for both inhibitors; however, it did not reverse the inhibition of the preformed complex. The dissociation constant for I‐1 was 2.2 × 10−9M and 3.8 × 10−9M for I‐2 at 30°C and pH 6.9. Both inhibitors functioned via a noncompetitive mechanism. I‐2 was also stable at pH 2.0. I‐2 was more stable to proteolytic digestion by trypsin than

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1985.tb13280.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTMethodology was developed that allowed sensitive measurement of phytohemagglutinin (PHA), the lectin of kidney beans. Trypsinated porcine red blood cells were treated with saline extracts of kidney beans, incubated, and the nonagglutinated cells were quantitated using a Coulter Counter. This hemagglutination activity (HA) assay was then used to monitor the PHA in cooked kidney beans. The thermal treatment (minutes @°C) required to reduce HA by 1 log cvcle was: 12 @ 100°C: 62 @ 93°C: 136 @ 88°C: 160 @ 82°C. Beans were prepared in commercially available low‐temperature cookers and evaluated for tenderness and residual hemagglutinating ac

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1985.tb13281.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTLupin protein isolates were prepared by alkaline extraction and precipitation at pH 5.1, 4.2 and 4.9 and their functional properties investigated. Solubility, emulsification capacity, swelling and gelation properties were determined under different conditions of pH, ionic strength and heat treatment. Lupin protein isolates showed better solubility than soybean isolate and a similar emulsification capacity. Swelling and gelation were found to be inferior, but when modifications in the methods of isolate preparation were introduced these properties were significantly improved. Consequently, it is possible to consider lupin proteins as a potential substitute for soybean proteins in food applications.

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1985.tb13282.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTAn outline for isolating sunflower lipoxygenase (SLO) from germinating seeds is described. With linoleic acid as substrate, SLO optimum pH was 6.2, the temperature of maximum activity was 35°C and the activation energy was 3.4 Kcal/mole. Nordihydroguaiaretic acid was the most effective inhibitor of SLO, while α‐tocopherol and diethyldithiocarbamic acid were less effective. Km values for linoleic acid, linolenic acid and methyl linoleate were 6.7, 5.0, and 40.0 μM, respectively. The activity of SLO was lost rapidly at temperatures higher than 50°C. The enzyme was stable when stored at −20°C or freeze‐dried, but not at 4°C in dilute solution. Experiments in micellar solution showed that SLO catalytic power was also maintained in hydrocarbon media with a Km for linoleic acid of 9 mMand a maximum velocity o

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1985.tb13283.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY