摘要:

ABSTRACTA solid butterfat fraction was prepared by controlled crystallization of the melt. Products of glycerolysis and rate of reaction were analyzed by size exclusion chromatography and gas‐liquid chromatography and compared to those of a tricaprilin model system. Physical and functional properties of the resulting mixture of mono‐ and diglycerides were compared to commercial monoglyceride‐based emulsifiers. The emulsifier from the butterfat fraction consisted of ∼60% mono‐ and 40% diglycerides and presented a very different FA profile from the commercial emulsifiers. The butterfat‐derived emulsifiers had a lower melting range and imparted a significantly lower surface tension at oil/water and oil/ skim milk

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14722.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTA reduced‐cholesterol butteroil was emulsified with different milk‐derived components into three 20% milk fat cream formulations. Electron microscopy showed an oil‐in‐water emulsion typical of milk lipid globules in natural cream. Heat treatment and homogenization had no effect on cream composition (p>0.05). Homogenization pressure had no effect on amount of protein associated with lipid globules but more phospholipid was associated with the lipid globules at 13.6/3.4 MPa (p ≦ 0.05). Formulation had significant effects on cream composition and amount of protein and phospholipid associated with lipid globules. Cholesterol was reduced 65 to 76% lower than that of natu

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14723.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTEmulsifying properties of six experimental and three commercial control, lipid‐reduced, and calcium‐reduced whey protein concentrates (WPC) were evaluated on the basis of mean droplet size and creaming intensity in model emulsions. Mean droplet sizes ranged from 225 to 395 nm. Model emulsions made with a commercial control (WPC F), experimental lipid‐reduced (WPC MF. 1, MF. 45), commercial lipid‐reduced (WPC E), and experimental calcium and lipid‐reduced (WPC B) samples had low stabilities. Emulsion stabilities of the WPC most strongly correlated with protein solubility and fatty acid compositions, but did not correlate with mean dro

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14724.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTpH‐induced changes in casein micelles during direct acidification and bacterial fermentation of reconstituted skim milk at 20°C were monitored by scanning electron microscopy (SEM) in combination with biochemical and rheological methods. For SEM casein micelle observations, an original method of milk sample preparation with porous inorganic membranes was developed. Micrographs suggested that different stages of micellar association were related to pH and that between pH 5.5 and 5.0 casein micelles coalesced. Correlations between microstructural and biochemical changes in casein micelles, and rheological behavior of milk or gel, help to explain the different steps leading to the final protein network of the acid milk g

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14725.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe flow behavior of whey protein isolates (WPI) was studied in systems processed under different conditions. Experiments were undertaken to study effects of heating conditions (temperature/time), pH, solid content, calcium chloride, and guanidinium hydrochloride addition on the gelation of whey protein isolate solutions. The rheological data demonstrated a power‐law frequency dependence of the viscoelastic functions G″ (ω) and G″ (ω) and a frequency‐independent tan δ determined from a multi‐frequency scan of tan δ vs gelling time at the gel point. The power‐law exponents (n) obtained from these dynamic measurements for determining the sol‐gel transition point were between 0.62 and 0.69. Those values suggest a percolation mechanism for the

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14726.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTAggregation of β‐Lactoglobulin β‐Lg) solutions, with and without sodium polypectate (SPP), was investigated at pH 6.5 and 3.5 by turbidity measurements and gel permeation chromatography during heating at 1°C/min. The ratio of β‐Lg:SPP was maintained at 10:1. At pH 6.5, the transition temperature of β‐Lg aggregation decreased linearly with the logarithm of β‐Lg concentration. Irrespective of β‐Lg concentration, SPP did not affect the rate of β‐Lg aggregation during heating at pH 6.5. However, SPP influenced the formation of high‐molecular‐weight (HMW) β‐Lg aggregates during heating at pH 6.5 was related to bulk macromolecular concentration. No thermal aggregation transitions were detected for β‐Lg solutions at pH 3.5. SPP interacted with β‐Lg at pH 3.5 to form a co

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14727.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTNear‐infrared transmittance spectroscopy was used to determine the average fat content in farmed Atlantic salmon fillets with skin and scales. The fat content was 5.7–17.6% and weight range 1.0–5.4 kg. A partial least square regression including 43 salmon resulted in a multivariate prediction correlation of 0.97 and a root mean square error of cross validation of 0.75%. Regression models using 6 to 9 wavelengths in the 850–1048 nm range gave somewhat lower prediction errors than a model using 100 wavelengths. Results showed that NIR transmittance was suited to determine fat content nondestructively in whole salmon fillets with skin and

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14728.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTFour anionic trypsins, tentatively labeled trypsin A, B, C, and D, isolated from crayfish hepatopancreas, had high casein activity between pH 5.5 and 10.0. Temperature optima for hydrolysis of casein were 45°C for A and B, and 50°C for C and D. Trypsin D had the highest substrate turnover number (Vmax) for casein reaction compared with the other trypsins at pH 6.8. Trypsins A and D had higher activities against myofibrilla and sarcoplasmic proteins from crayfish tail meat than did B and C. Results suggested that trypsins A and D are important in development of mushiness in crayfish tail meat compared with other trypsins presen

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14729.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTAn enzyme‐linked immunosorbent assay (ELISA) for specific determination of microbial transglutaminase (MTGase) has been developed using its polyclonal and monoclonal antibodies. In the assay we calibrated sodium dodecylsulfate (SDS)‐denatured MTGase for standard, and the detection limit of the SDS‐denatured MTGase was 0.1 μg/mL. When products were extracted with SDS and 2‐mercaptoethanol, which assured optimum protein recovery, the assay covered the expected levels for determination of MTGase in surimi‐based products. In model kamaboko products, recoveries were 50–71%. When the procedures were applied to commercial products, 0.01–0.18% (w/w) of MTGase were found i

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14730.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTJuice from transgenic tomato (Lycopersicon esculentumcv Rutgers) fruits with reduced levels of pectin methylesterase (PME) activity due to the expression of a PME antisense gene exhibited improvement in quality. The percentage increase in juice from transgenic fruits over that of juice from wild type Rutgers ranged between 5.1–5.3 for total solids, 3.8–6.1 for soluble solids, 70–80 for efflux viscosity, 180–220 for serum viscosity and about 50 for precipitate weight ratio. Time of harvest had no effect on quality of juice. Ketchup prepared from transgenic fruit juice had a lower Bostwick value, reduced serum separation and high serum viscosity compared to ketchup from parental

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1996.tb14731.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY