Changes in the Concentration of Free Amino Acids in Grape Berries During Maturation

Abstract

The concentrations of 8 amino acids and of total free amino acids in the juices of 6 table varieties and 12 wine varieties of grapes were determined at various times during the ripening and ripe periods of fruit development. Total free amino acids increased two-to-fivefold during ripening and ripe periods of fruit development and ranged in concentration from 200 to 800 mg per ml juice (leucine equivalents). The 8 amino acids studied accounted for 59 to 94% of the total free amino acids in the different varieties at all stages investigated. The concentration of arginine usually increased rapidly during the ripening period and then often decreased as the fruits became ripe to overripe. Proline, on the other hand, generally increased very rapidly during the latter stages of ripening and during fruit senescence. Arginine was the predominant amino acid at fruit maturity in `Black Corinth,' `Cardinal,' `Flora,' `Gewurztraminer,' and `Muscat Hamberg'; proline was predominant in `Cabernet Sauvignon,' `Carignane,' `Chardonnay,' `Chenin blanc,' `Malbec,' `Perlette,' and `White Riesling;' and glutamic acid was the main amino acid in `Tokay.' `Alicante Bouschet,' `Palomino,' `Pinot blanc,' `Pinot noir,' and `Thompson Seedless' contained about equal concentrations of arginine and proline in the mature fruits. Mature fruits of `Cardinal,' `Chardonnay,' and `Gewurztraminer' were relatively high in total free amino acids (> 600 mg/100 ml juice); `Tokay' and `White Riesling' were low (< 300 mg/l00 ml juice); and the other varieties were intermediate.