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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food biochemistry 16 (1992), S. 0 
    ISSN: 1745-4514
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Three isozymes of polyphenol oxidase (PPO I, PPO II and PPO III) were purified from lobster (Homarus americanus) by ion-exchange chromatography and preparative isoelectric focusing using a Rotofor cell. The purified isozymes migrated as single protein bands in polyacrylamide gels with Rf values corresponding to molecular weights of 32,180, 35,480 and 39,300, respectively. The pI values of the PPO isozymes were 3.89, 4.26 and 4.54, respectively. PPO I was most active at pH 6.5 and most stable from pH 6.0 to 7.0; PPO II was most active within the pH range 6.0 to 7.0, and most stable within the pH range 4.0 to 9.0; while PPO III was most active at pH 7.0 and most stable in the pH range 6.0 to 8.0. The temperature optimum for the PPO-dihydroxyphenylalanine oxidation reaction was 35C with PPO I and 45C with PPO II or III. Lobster PPO I lost about 30% of its initial activity after 30 min incubation at 45C, while PPO II and II retained virtually all their activity after the same heat treatment. The catalytic specificities of the PPO isozymes were relatively higher with dihydroxyphenylalanine as substrate than with chlorogenic acid.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1745-4514
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Optimization models are useful in ascertaining optimum parameters as they relate to a particular response. Ethanol production with different cellulase-systems and substrate concentrations were subjected to this model and the results revealed that crude unextracted cellulase-systems are more efficient than crude extracted cellulase-systems in producing hydrolysates for ethanol production with Pichia stipitis (Y-7124), Saccharomyces cerevisiae (AT 60868) and their mixture. Response surface plots showed that for 80–90% of high concentrations of delignified wheat straw up to 11% could be converted into ethanol by simultaneous hydrolysis with enzyme loading of 16 IU/mL and fermentation with P. stipitis. P. stipitis was found to be the most suitable yeast for the fermentation of mixed hexose and pentose sugars in the wheat straw hydrolysate.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food biochemistry 20 (1996), S. 0 
    ISSN: 1745-4514
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bovine serum extract containing α2-macroglobulin was added to bluefish meat pastes to various final concentrations of 0% (control), 0.05%, 0.10%, or 0.20%, and gels were prepared from the treated fish pastes by heat at 60C for 60 min, or by hydrostatic pressure at 3,742 atm for 30 min. α2-Macroglobulin caused significant color changes in the gels even though increasing inhibitor concentration showed no further changes. L* values were increased by inhibitor addition while a* and b* values were decreased. Storage studies at 0C indicated that hardness and elasticity of the heat-induced gels were higher for the α2-macroglobulin containing samples than the control samples within 7 days of storage, whereas a similar effect was not observed with pressure-induced gels. SDS-PAGE studies indicated that pressure treatment retained more myosin in the fish gels than the heat treatment. The heat-induced gels with α2-macroglobulin also retained more myosin than those without the protease inhibitor.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food biochemistry 25 (2001), S. 0 
    ISSN: 1745-4514
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The contribution of several high pressure (HP) processing related factors (pressure level, 300-400 MPa; pressure cycle, 1-3, and pressure-hold time, 30–120 min) on the inactivation of pectin methyl esterase (PME) in single strength (pH 3.7 and 11.4 °Brix) and concentrated (pH 3.5 and 42 °Brix) orange juice was evaluated. A response surface methodology was employed to model the combined effects of factors on the enzyme inactivation. The main effects were described by linear or quadratic functions. For both single strength and concentrated orange juices, the effects of all three main factors and some interactions (pressure level, cycle and holding time) were statistically significant (p〈0.05). The dual nature of pressure inactivation of PME (with an instantaneous inactivation due to a pressure pulse, instantaneous pressure fall, and first order rate of inactivation during the pressure hold, yielding D and z values) reported in earlier studies was confirmed. Combination models were developed to predict the residual enzyme activity as influenced by the pressure level, number of pressure cycles and pressure hold time.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food biochemistry 18 (1994), S. 0 
    ISSN: 1745-4514
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The enzymes, chymotrypsin, trypsin, collagenase and cathepsin C, as well as the protease inhibitor, α2-macroglobulin, have been shown to be susceptible to hydrostatic pressure inactivation. a2-Macroglobulin lost about 15% activity at a pressure of 2,000 atm and as much as 80% at 3,000 atm pressure applied for 1 h in both cases. Thermal stability studies also indicated the protein to be completely denatured at about 75C. The enzymes were also inactivated to various extents depending on the amount of pressure and the duration of application, The degree of susceptibility to pressures ranging between 2,000–4,000 atm applied for time periods ranging from 5–60 min was found to be as follows: chymotrypsin 〈 cathepsin 〈 trypsin 〈 collagenase. The hydrostatic pressure effects were irreversible when pressure-treated enzymes were stored at room temperature (20–25C), but showed various levels of reactivation when stored at refrigerated temperatures (4–7C).
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK and Malden, USA : Blackwell Science Inc
    Journal of food biochemistry 29 (2005), S. 0 
    ISSN: 1745-4514
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Intact carp (Cyprinus carpio) fillets were packaged under vacuum and pressurized at 100, 140, 180 and 200 MPa at 4C for 15 or 20 min. Changes in the lipid fraction and color of the fillets as well as the electrophoretic profiles of the fish proteins were studied to establish the best conditions (time and pressure) for pressure-shift freezing the carp fillets. Thiobarbituric acid (TBA) values, free fatty acid (FFA) content and color parameters (L*, a*, b*) increased as the pressure level and pressurization time were increased. After 15 min of treatment at any pressure level, the intensity of the protein band with MW 〈 36 kDa decreased. With these results, the carp fillets were frozen using either pressure-shift freezing (PSF) (140 MPa, −14C for 12 min) or air-blast freezing (ABF) (−20C for 4 m/s) and then stored at −20C for 75 days. Changes in TBA values, FFA content, texture, total drip losses and size of ice crystal were evaluated. The TBA values and FFA content were relatively lower in the PSF samples than in the ABF samples. The freezing procedure did not seem to have a significant effect (P 〉 0.05) on the texture of carp fillets. PSF was more effective in reducing total drip losses in cooked samples compared to ABF treatment. Ice crystals found in the PSF fish samples were mainly intracellular, smaller and more regular in shape than those found in the ABF samples.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food processing and preservation 15 (1991), S. 0 
    ISSN: 1745-4549
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Drying characteristics of carotenoproteins were evaluated in an air-drier using air temperature (45, 55 and 65°C) and relative humidity (5 and 15%) as main factors. the study indicated that the carotenoprotein slurry exhibited a short constant rate period drying followed by classical diffusion drying. Higher temperatures achieved faster drying rates, but adversely affected its nutritional composition and/or quality. the proximate composition of carotenoprotein air dried at 45°C and relative humidity of 5% or 15% were comparable to that obtained by freeze drying.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food biochemistry 21 (1997), S. 0 
    ISSN: 1745-4514
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 61 (1996), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Effects of combination treatments involving hydrostatic pressure, pH, and crude α;2-macroglobulin on muscle protease activity and viscosity were investigated using response surface methodology. Statistical analysis showed the model was very significant, predicting responses with high accuracy. Proteolytic activities were reduced with increasing pressure and inhibitor concentrations while pH elicited a quadratic response. Reducing pH and increasing pressure also reduced viscosity of tissue homogenate, but inhibitor concentration did not affect (p 〉 0.05) this response. The proteases did not show any tendency to regain activity during 3 weeks storage possibly due to a crude inhibitor in the homogenate and did not seem to have any direct influence on viscosity as shown by a low correlation (r =–0.30). Viscosity progressively increased during this period.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 61 (1996), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Kinetic parameters for α;2-macroglobulin inhibition of selected proteases (collagenase, cathepsin D, trypsin and chymotrypsin) were determined along with the extent of inhibition of the corresponding fish muscle proteases. Protease inhibition by α;2-macroglobulin occurred in the presence of large macromolecular substrates but not in the presence of synthetic substrates. The inhibitor remained active at refrigerated temperatures (4–7°C). The α;2-macroglobulin did not have any inhibitory effects on proteases in intact fish muscle tissue possibly due to lack of penetration of the tissues, but showed various levels of inhibition of proteases in tissue homogenates. Inhibitor concentration of 0.1% per weight of tissue homogenate resulted in about 17% loss of proteolytic activity while 0.4% inhibitor concentration caused complete loss of protease activity.
    Type of Medium: Electronic Resource
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