17E-7 |
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M. VENKATACHALAM1, K. H. Roux2, S. S. Teuber3, and S. K. Sathe1. (1) Dept. of Nutrition, Food & Exercise Sciences, Florida State Univ., 402 Sandels Bldg., Mail Code 1493, Tallahassee, FL 32306-1493, (2) Dept. of Biological Science, Florida State Univ., 335 Biology Unit 1, Mail Code 4370, Tallahassee, FL 32306-4370, (3) School of Medicine, Univ. of California, Davis, Div. of Rheumatology, Allergy & Clinical Immunology, 2221 Stockton Blvd., Sacramento, CA 95817 Pecan is an economically important tree nut and the U.S. accounts for ~80% of the world’s pecan production. Although various agronomic and certain proximate compositional aspects of pecans have been investigated, pecan proteins remain largely unexplored. With increasing awareness of tree nut proteins being major food allergens, and particular lack of understanding as to which pecan proteins are allergens, pecan protein characterization is imperative. Pecans, Desirable cultivar, were defatted using petroleum ether and soluble proteins were extracted under optimized conditions [1 h, 25°C, flour to solvent ratio of 1:10 (w/v)]. Effects of pH (1-12), ionic strength (0.0 – 4.0 M NaCl) and common protein solvents on pecan protein solubilization were evaluated. Albumin, globulin, prolamin, and glutelin fractions were prepared from defatted flour. Protein concentration was determined by micro-Kjeldahl (N X 5.3) and Lowry procedure. Protein polypeptide composition was determined using polyacrylamide gel electrophoresis under native and reducing conditions. Periodic acid-Shiff staining was used to detect presence of glycoproteins. Protein amino acid composition was determined by HPLC. Defatted pecan flour contained 34.8% protein on a dry weight basis. Protein solubility was minimal in pH 3 – 7 range and increased significantly on either side of this pH range. Increasing ionic strength from 0.0 to 4.0 M NaCl significantly improved (~ 9 fold) protein solubility. Among the solvents tested, 0.1 M NaOH was the most effective protein solubilizer. The glutelin fraction (60.1%) accounted for major portion of pecan proteins followed by globulin (31.5%), prolamin (3.4%) and albumin (1.5%) fractions, respectively. Pecan protein polypeptides had molecular weights in the range 12,000-66,000 Da. The globulin fraction contained most glycoprotein polypeptides in pecan proteins. Lysine was the first limiting essential amino acid in total pecan protein, globulin, prolamin and glutelin fractions. Phenyalanine was the first limiting amino acid in the albumin fraction.
Session 17E, Food Chemistry: Proteins
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