30C-30 |
Quantification and distribuation of proteins in barley grain |
A. K. LEKHI1, F. Temelli, and T. Vasanthan. (1) Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada Proteins make up 8-15% of barley, which is mainly used as animal feed. Characterization of barley proteins is essential before their potential incorporation into food products. However, information is lacking on the distribution of the different types of proteins in barley. The objective was to quantify the four major classes of proteins in the whole grain and determine their distribution in the bran and endosperm fractions in two barley varieties. Candle (waxy) and Condor (regular) barley were pearled stepwise up to 42%. Scanning electron microscopy (SEM) was done on the whole and pearled grains. Compositional analysis was carried out on all samples, whereas a modified Osborne procedure was performed on the 19% pearlings fraction to quantify protein classes. For both varieties, SEM images showed that 17-22% of pearling removed outer aleurone layer with minimum abrasion of the endosperm. In whole Candle, albumins, globulins, hordeins and glutelins account for 12, 8, 36 and 22% (w/w) of total proteins, respectively. Of the individual grain proteins, 35% of total albumins, 33% glutelins, 50% globulins and 23% hordeins were found in the bran fraction (19%) with the remainder being in the endosperm. In whole Condor, the protein composition was similar to that of candle, except the hordein content was higher reaching 42%. Of the total globulin content, 65% was in the bran (19% pearled) and 61% of total albumins were concentrated in the endosperm. Pearling at about 19-20% level resulted in the complete separation of true bran in the barley grain. For both varieties, even though the endosperm proteins are mainly made up of hordeins and glutelins, substantial amounts of albumin are also present. Globulin concentration is highest in the bran with glutelin content being similar to that of albumin. Better understanding of the composition and distribution of proteins in the barley grain will lead to development of value-added food products utilizing bran and endosperm fractions.
Session 30C, Food Chemistry: Proteins
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