Varying Levels of Sugars, Acids, Amino Acids, and Monoterpenes contained in Muscat of Alexandria Grapes Produced in Okayama

Sugars,acids, amino acids, and monoterpenes in Muscat of Alexandria grapes were analyzed to elucidate the distribution of the fruit taste and aroma. Fruit bunches were collected from 25 commercial vineyards in Okayama Prefecture, comprising six early heated, nine normally heated, and 10 unheated greenhouses, at mid-harvesting time in each vineyard. Juice was squeezed out by head and used for analyses. Total soluble solids (TSS) content in juice from 3 vineyards were lower than 16°Brix, the lowest limit for shipping. Average content of glucose was lower in early heated vines and that of fructose was lower in unheated vines than normally heated ones, although there were wide variations among vines. Average malic acid content was highest in early heated vines and by further lowest in unheated vines. However, no significant difference was found in tartaric acid content among the vines. Concentrations of alanine and proline, major amino acids enhancing sweetness, were lower in early heated vines than in normally heated ones. In unheated vines, average concentration of proline was highest, although that of glutamine, a main factor enhancing deliciousness of the juice, was lowest. Threonine, an amino acid which at higher levels decreases sweetness, was detected at various levels depending on the vine. Geraniol, the second major substance of Muscut aroma, was found at significantly higher levels in early heated vines than in the other ones. The relationships between these compositions and the berry flavor were discussed.

岡山県で生産されるマスカット・オブ・アレキサンドリア果実の味のばらつきを検討するために，ガラス室またはビニールハウス25園（早期加温6園，普通加温9園，無加温10園）で収穫された果房について，果汁に含まれる糖，酸，アミノ酸，モノテルペン含量を分析した．各樹の収穫盛期に果実をサンプリングしたが，各作型の１園ずつでは可溶性固形物含量（TSS）が最低基準の16°付近に達していなかった．これらを除くと，早期加温樹ではグルコース含量が特に低いものがあり，無加温樹ではフラクトース濃度が低い傾向であった．リンゴ酸濃度は早期加温樹で高く，無加温樹で低かったが，酒石酸濃度には作型や樹による差が少なかった．アミノ酸濃度には樹による差が大きかったが，早期加温樹では全アミノ酸，アラニン，γ-アミノ酪酸，プロリンが他の作型よりも低い傾向であった．また，無加温樹ではプロリンは他の作型の樹よりも高い樹が多かったが，グルタミンは著しく低かった．モノテルペンの内，マスカット香の主成分であるリナロール含量は，樹による差が非常に大きかったが，第２主要成分であるゲラニオールは早期加温樹で高かった．これらの果汁成分の相違が果実の味に及ぼす影響について考察した．