摘要:

ABSTRACTRelatively simple mathematical models for microwave energy penetration in food products were applied, based on Lambert's law and taking into account internal reflections. With these models direct insight in microwave heating distributions in products with basic geometries and homogenous composition can be gained. Effects of changes in product composition with relation to dielectric properties and changes in product size can be predicted. The model was not designed to give an exact and detailed prediction of temperature distributions during microwave heating. However, it can simulate microwave heating of various food products and be useful for designing heat treatments.

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb10941.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTSolubilization of oil molecules in surfactant micelles can have pronounced effects on the physicochemical properties of oil‐in‐water emulsions, e.g., reaction rates, distribution of nonpolar ingredients, emulsion stability and controlled flavor release. Static light‐scattering was used to compare the solubilization kinetics of corn oil droplets with those ofn‐hexadecane droplets (ø= 0.02 wt%, d32= 0.3 μm) in a micellar surfactant solution (2 wt% Tween 20). Then‐hexadecane droplets were completely solubilized by the micelles within 5 days, but no change was observed in the corn oil emulsíon Possible reasons for the observed differences in solubilization kinetics were related to the molecular geometry and size of the o

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb10942.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTCheese headspace volatile compounds were extracted with solid‐phase microextraction (SPME) fibers, coated with either polydimethylsiloxane or polyacrylate, and thermally desorbed in the injector port for gas chromatographic (GC) analysis. Results with polyacrylate‐coated fibers were better than those with a polydimethylsiloxane fiber. Major cheese volatile components such as volatile fatty acids and 5‐lactones were readily extracted by both SPME fibers, but minor components such as volatile sulfur compounds were not observed. SPME‐GC patterns were distinctly different among cheese varieties, and characteristic volatile compounds could be identified using multivariate tec

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb10943.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTPressure (300–900 MPa) so modified β‐lactoglobulin that it displayed reduced emulsifying capacity and foamability compared to native β‐lactoglobulin. However, the pressure‐treated samples showed a greater capacity for protein‐protein interactions in the adsorbed layers of interfaces as evidenced by increased surface‐dilational modulus and resistance to displacement by a surfactant in foams. The observed behavior was explained by a pressure‐induced structural change in β‐lactoglobulin. This increased its hydrophobicity and its potential for aggregate formation which probably accounts for the reduced emulsifying capaci

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb10944.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTBiopolymers were prepared by cross‐linking whey protein isolate (WPI) and soybean 11S using transglutaminase. Electrophoretic pattern, solubility, emulsification, hydrophobicity and foaming properties of the biopolymers were determined. SDS‐PAGE showed bands corresponding to high‐molecular‐weight components (MW>200 kDa). Biopolymer solubility was>90% at pH 3 and below, and at pH 7 and above. Emulsifying properties of biopolymers were lower than those of WPI. The foaming capacity of the biopolymers (23.6 mL) and WPI/11S mixture (22.7 mL) were similar to that of egg albumin (20.3 mL). The foaming stability of the biopolymers (122 min) was higher than that of WPI/11S mixture (33.7 min), and was similar to that of egg albumin (1

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb10945.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTCyst(e)ine and methionine were converted into cysteic acid and methionine sulfone by oxidizing with performic acid. The oxidized samples were then subjected to acid hydrolysis (6N HCl, 105–110°C/24 hr). After derivatization with phenylisothiocyanate, reverse phase HPLC separation was carried out at 48°C and with UV detection. Different gradients and pH values in the eluent were assayed to determine the best resolution. Analytical parameters, detection and quantification limits, linearity, precision and accuracy, were determined. The method was reliable and accurate for measuring cyst(e)ine and methionine in infant formu

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb10946.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTConcentrations of seven milk‐clotting enzyme preparations were standardized to equal clot times. Portions of bovine αs‐, β‐ and κ‐casein were treated with enzymes. Proteolytic activity of the coagulants on each casein fraction was determined using the TNBS (2,4,6‐trinitrobenzene‐sulfonic acid) procedure. Recombinant chymosin showed the lowest degree of proteolysis on αs‐ and β‐caseins. Excessive proteolysis of calf rennet appeared to be due to the pepsin fraction.M. mieheiandM. pusillusvarLindtproteases showed similar degradation of caseins, butM. pusillusvarLindtwas more proteolytic when β‐casein was the substrate.C. parasiticaprotease showed the highest degree of proteolysis on αs‐ and β‐caseins but was the

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb10947.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTHeat‐induced gelation of myofibrillar proteins and myosin (0.6M; pH 6.0) from rabbit fast‐ and slow‐twitch muscles was analyzed by thermal scanning rheometry. Proteins from slow‐twitch muscle exhibited higher thermostability and lower gel strength than those from fast‐twitch muscle. Purifying myosin from myofibrillar proteins changed heat‐gelation profiles and generally increased gel rigidity at 80°C. However, the effect of some proteins on the gelation of myosin was muscle dependent. Complete elimination of actin decreased the heat‐gelling ability of slow myosin and increased that of fast myosin. Also, elimination of C‐protein led to a greater increase in rigidity of gels from slow myosin than from fast myosin. The heat‐behavior of the different protein fractions was related to the degree and type of aggr

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb10948.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe effects of ionic strength on myofibrils and myosin from rabbit fast‐twitchPsoas major(PM) and slow‐twitchSemimembranosus proprius(SMp) muscles before and after heating were studied by electron microscopy and thermal scanning rheometry. The direct suspension of proteins in low ionic strength (0.2M KCl; pH 6.0) led to very weak gels, whereas a gradual lowering of the ionic strength (by dialysis against 0.2M KCl; pH 6.0) of 0.6M KCl protein solutions induced strand‐type networks at low temperature and strong heat‐induced gels. As shown by transmission and scanning electron micrographs, in low ionic strength, SMp myosins formed shorter filaments before heating and thinner and shorter structures in heat‐induced gels, as well as a lower gel porosity than P

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb10949.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTGround turkey breast and thigh muscle were extracted with various NaCl solutions with or without added CaCl2, MgCl2, or ZnCl2(0.05%). Protein solubility was increased by CaCl2and decreased by ZnCl2in each muscle type. At 4% NaCl, MgCl2increased thigh myosin solubility by 30%, compared to the control, whereas CaCl2had no effect. At 2% and 4% NaCl, breast myosin was not affected by MgCl2or CaCl2. Myosin was not detected for either muscle type when ZnCl2was used. All three salts increased breast actin solubility but only MgCl2increased thigh actin solubility. The CaCl2resulted in the highest overall protein solubility and MgCl2resulted in the highest thigh myosin and actin solubility at 4% NaCl.

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb10950.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY