TY - JOUR T1 - Changes in Nitrogen Compounds in Berries of Six Grape Cultivars during Ripening over Two Years JF - American Journal of Enology and Viticulture JO - Am J Enol Vitic. SP - 69 LP - 77 DO - 10.5344/ajev.2002.53.1.69 VL - 53 IS - 1 AU - Koki Yokotsuka AU - Masakazu Fukui Y1 - 2002/01/01 UR - http://www.ajevonline.org/content/53/1/69.abstract N2 - Nitrogen compounds (free amino acids, peptides, and proteins) in the berries (juice, skins, and seeds) of six grape cultivars were studied to determine the amount of protein and changes in protein during ripening. Proteins were extracted totally and effectively from the skin and seeds at pH 12 with water. The amount of protein in juice and skins increased over time during ripening, whereas the amount of protein in seeds changed only slightly. Approximately 63% of total soluble and/or extractable nitrogen compounds in berries were proteins. Free amino acids and peptides comprised approximately 20 and 17% of all nitrogen compounds, respectively. Seeds contained on average approximately 50% of all the nitrogen compounds found in berries, primarily in the form of proteins. Juice and skins both contained approximately 25% of nitrogen compounds, and in juices these were primarily in the form of free amino acids. Proteins from these three tissues were rich in aspartic acid and glutamic acid, and similar amino acid compositions of proteins were observed in two different growing seasons for the same tissue of the same cultivar. Moreover, these compositions did not change appreciably during ripening. Amino acid compositions of proteins from the same tissue of different cultivars were similar. In comparisons of compositions of proteins from the three different tissues, a greater degree of similarity was observed between proteins from the juice and skin than between proteins from the juice and seeds or between proteins from the skin and seeds.Acknowledgments: The authors express their gratitude to Mr. Tohru Hosaka, of the Institute of Enology and Viticulture, Yamanashi University, for his technical assistance. ER -