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  • Blackwell Publishing Ltd  (10)
  • 1
    Electronic Resource
    Electronic Resource
    Kinetics of Racemization of Amino Acid Residues in Casein (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 47 (1982), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Exposing casein to alkali (0.1N NaOH at 65°C) partly racemized the amino acid residues. A plot of D/L ratios for seven amino acids versus time of treatment shows fast initial racemization rates that decrease after about 1 hr. A linear free energy relationship exists between racemization rates and inductive effects of amino acid side chains or R-substituents (σ*). Kinetic studies over the temperature range 25–75°C yields activation energies (in Kcal/mole) for aspartic acid (20.8), phenylalanine (28.7), glutamic acid (32.5), and alanine (32.4). Racemization rates increase with hydroxide ion concentration but not with protein concentration. Acetylation of amino groups prevents lysinoalanine formation but not racemization, permitting studies which distinguish between effects of these two alkali-induced reactions. Understanding principles that govern racemization should help in designing food processes that minimize undesirable, deteriorative changes in food proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1982.tb12709.x
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  • 2
    Electronic Resource
    Electronic Resource
    Factors Governing Lysinoalanine Formation in Soy Proteins (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 49 (1984), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Exposing soy protein to alkaline conditions (pH 8-14) for various time periods (10-480 min), and temperatures (25-95°C at 10°C intervals) destroyed all of the cystine and part of arginine, lysine, serine, and threonine residues. These losses were accompanied by the appearance of lysinoalanine (LAL) and unidentified ninhydrin-positive compounds. Acylation of the proteins minimized LAL formation. Addition of cysteine, copper salts, dimethyl sulfoxide and glucose also suppressed LAL production. Oxygen, with one possible exception, did not affect LAL formation. Free and protein-bound lysinoalanine is stable to acid but not basic conditions used for protein hydrolysis. Mechanisms are described to explain the observed influence of these variables on LAL generation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1984.tb14970.x
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  • 3
    Electronic Resource
    Electronic Resource
    Relationship between In Vitro Digestibility of Casein and its Content of Lysinoalanine and D-Amino Acids (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 46 (1981), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alkali and heat induce changes in proteins. These include racemization of L- to D-amino acids and crosslinking via lysinoalanine. Since high-quality proteins are presumably well-digested, possible effects of D-amino acid and lysinoalanine contents on food casein digestibility was examined. The following variables, which were expected to influence all three parameters, were evaluated: (a) pH (8-14); (b) temperature (25-75°C); and (c) time of treatment (10 min to 24 hr). An approximately inverse relationship was observed between D-ammo acid and lysinoalanine content and the extent of proteolysis. Such changes may lower the quality and safety of foods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1981.tb14545.x
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  • 4
    Electronic Resource
    Electronic Resource
    Nutritional Improvement of Soy Flour Through Inactivation of Trypsin Inhibitors by Sodium Sulfite (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 51 (1986), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Treatment of raw soy flour at 75°C with 0.03M sodium sulfite for 1 hr completely inactivated trypsin inhibitors leaving no sulfite residues in the soy proteins. Rat feeding studies showed that the protein efficiency ratio (PER) increased from 1.55 for raw flour to 2.11 for heated flour and 2.49 for flour heated in the presence of sulfite. This nutritional improvement was accompanied by enhancement in in vivo nitrogen digestibilities. Pancreas weights were elevated in rats fed raw soy flour, but not in those consuming heated soy flour, with or without sodium sulfite. Knowledge of the factors that decrease the stability of potentially toxic trypsin inhibitors may be useful for improving the quality of certain foods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1986.tb13094.x
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of Carbohydrates and Heat on the Amino Acid Composition and Chemically Available Lysine Content of Casein (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 49 (1984), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Casein, casein-starch, casein-sucrose, and casein-glucose mixtures were heated under conditions modeling storage, autoclaving, baking/broiling and charring (37–300°C). Losses in total and chemically available lysine content were measured by fluorodinitrobenzene (FDNB) and dye-binding methods. The lysine and arginine content decreased up to 99%. Changes in amino acid profiles were accompanied by the appearance of at least five new ninhydrin-positive compounds. The relative potencies of the three carbohydrates effecting these changes were different at the four temperatures studied. The available lysine contents of the samples measured by the two independent methods were identical within experimental error. The results show different susceptibilities of casein to heat- induced damage in the presence of different carbohydrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1984.tb13219.x
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  • 6
    Electronic Resource
    Electronic Resource
    Inter- and Intra-Laboratory Variation in Amino Acid Analysis of Food Proteins (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 48 (1983), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Amino acid compositions of casein, egg white, beef, soy isolate, rapeseed concentrate, pea flour and wheat flour were studied by seven collaborating laboratories. Samples were hydrolyzed with 6N HCl, performic acid + 6N HCl, and (with one exception) 4.2N NaOH. Amino acids were then determined by ion-exchange chromatography using automatic analyzers. One laboratory, however, determined tryptophan by treatment with p-dimethylaminobenz-aldehyde. The colorimetric determination of tryptophan was comparable to the tryptophan values determined by ion-exchange chromatography. Interlaboratory variation of tryptophan (coefficients of variation, CV, up to 24%), cystine and methionine (CV up to 17%), was greater than that of most other amino acids (CV up to 10%). Intralaboratory variation for all amino acids was less than 5%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1983.tb10781.x
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  • 7
    Electronic Resource
    Electronic Resource
    Feeding Tomatoes to Hamsters Reduces their Plasma Low-density Lipoprotein Cholesterol and Triglycerides (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 65 (2000), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hamsters were fed semipurified diets containing green or red freeze-dried tomato powders. Compared to the control diet devoid of tomatoes, a 59% and 44% reduction low-density lipoprotein (LDL) cholesterol was induced by both the green and red tomatoes, respectively. The corresponding reductions in very low-density lipoproteins (VLDL) were 45% and 35% and in plasma triglyceride concentrations 47% and 31%, respectively. Plasma levels of high-density lipoproteins (HDL) were unaffected. Fecal deoxycholic and lithocholic acid concentrations of hamsters on tomato diets were higher than those on control diets. Possible contributions of major components of green and red tomatoes to these beneficial effects are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2000.tb13608.x
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  • 8
    Electronic Resource
    Electronic Resource
    Distribution of Catechins, Theaflavins, Caffeine, and Theobromine in 77 Teas Consumed in the United States (2005)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 70 (2005), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: : To help define the composition of commercial teas consumed in the United States, we have developed and validated an high-performance liquid chromatography (HPLC) method to analyze levels of catechins, theaflavins, and alkaloids in 77 commercial black, green, specialty (brown rice, white, oolong), and herbal teas extracted with hot water to simulate home use. The following 13 compounds were separated in a single analysis on an Inertsil ODS-3v column with acetonitrile/potassium dihydrogen phosphate as the mobile phase: (−)-epigallocatechin, (+)-catechin, (−)-epicatechin, (−)-epigallocatechin-3-gallate, (−)-gallocatechin-3-gallate, (−)-epicatechin-3-gallate, (−)-catechin-3-gallate, theaflavin, theaflavin-3-gallate, theaflavin-3′-gallate, theaflavin-3, 3′-digallate, caffeine, and theobromine. The data show that (1) extraction time from 3 min to 20 min did not significantly affect measured levels of tea compounds and (2) there was a wide variation in the composition of the tea compounds both within each tea category and among categories: black teas contained both theaflavins and catechins, green and white teas contained catechins and trace amounts of theaflavins, herbal teas contained very low amounts of all tea compounds. A statistical profile of the distribution of catechins, theaflavins, caffeine, and theobromine in the evaluated teas offers consumers a choice of teas containing high levels of health-promoting compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2005.tb08304.x
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  • 9
    Electronic Resource
    Electronic Resource
    Immunoassays for Bowman-Birk and Kunitz Soybean Trypsin Inhibitors in Infant Formula (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 69 (2004), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: : Because the consumption of soybean inhibitors of digestive enzymes in processed foods may have both beneficial and adverse health-related effects, reliable and rapid analytical methods for these inhibitors are needed. Monoclonal antibody-based sandwich enzyme-linked immunosorbent assays (ELISAs) were developed for the 2 major soybean protease inhibitors, the Kunitz trypsin inhibitor (KTI) and Bowman-Birk inhibitor (BBI) of trypsin and chymotrypsin. The ELISAs had limits of quantification of approximately 1 and 3 ng/mL for BBI and KTI, respectively, and were used to measure active inhibitors in soy infant formulas. Results were compared with enzymatic analyses and demonstrated that most of the trypsin- and chymotrypsin-inhibitory activities of infant formula were due to constituents other than KTI and BBI. The sandwich ELISA for BBI was also effective in detecting soybean germplasm with atypically low levels of BBI.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2004.tb17849.x
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  • 10
    Electronic Resource
    Electronic Resource
    Ninhydrin-Reactive Lysine in Food Proteins (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 49 (1984), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A lithium acetate-dimethyl sulfoxide ninhydrin reagent was shown to be useful for reaction of amino groups in a series of structurally diverse food proteins and flours of variable lysine content. The proteins were bovine serum albumin, casein, hemoglobin, lactalbumin, lysozyme, soybean protein, soybean trypsin inhibitor, trypsin, and wheat gluten. The flours were barley, high lysine corn, high protein rice, lima bean, nonfat dry milk, rice, soy, and wheat. The ninhydrin-reactive lysine content of these proteins varied from 63-109% of the theoretical values. This variation needs to be taken into account in possible applications of the ninhydrin reaction to food proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1984.tb13656.x
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