Effect of Fruit Size on Skin Color and Juice Constituents in White Peaches Produced in Okayama

Skin color and juice constituents in large(L), medium(M), nad small(S) fruits of four peach cultivars, Hashiba-hakuho(early maturing), were analyzed to elucidate the effect of fruit size on the quality. The fruits containing higher soluble solids than 12°Brix were samled at a commercial packing-house located in southen Okayama. They were stored at 25℃ until fully ripened. The skin color on the cheeks (yellowish) was dark in S fruits of Hashiba-hakuto and Hakurei, respectively, compared to the fruits of other sizes. The sucrose + fructose content in juice, the major source of the sweetness, was higher in S and M fruits in Hakuho, Shimisu-hakuto, and Hakurei, while the malic+citric acid content, the major sour constituent, was lower in L fruits in those cultivars, although no significant difference was found in Hashiba-hakuho. Asparagine, the biggest amino acid fraction and thought to deteriorate the fruit taste at high levels, was higher in L fruits tahn in S fruits in Hashiba-hakuho and Hakuho. The content in Shimizu-hakuto and Hakurei fruits was generally low and not affected by fruit size. The content of γ-decalactone, the major peachy aromatic substance, was higher in L fruits in Hashiba-hakuto, in M fruits in Hakuho and Shimizu-hakuto, and in S fruits in Hakurei, than in those of other sizes. Sensory tests revealed that the L fruits of Hakuho and S fruits of Hakurei were poor in flavor. These results suggest that the larger fruits of Hakuho, Shimizu-kakuto, and Hakurei, the representative white peach fruits in Okayama, have rather falatter tastes than medium size fruits because of their lower sweetness and sourness and weaker aroma, as well as poorer texture.

岡山市一宮のモモの選果場に出荷された有袋栽培の‘橋場白鳳’（早生），‘白鳳’（早中生），‘清水白桃’（中生）および‘白麗’（晩生）から，３段階のサイズ（Ｌ，Ｍ，Ｓ）の果実を入手し，完熟状態（手で皮が剥ける）に達するまで25℃の室温においた．それらの果実について，果皮色と果汁成分の分析と果肉の食味テストを行い，果実のサイズによる品質の相違を検討した．‘橋場白鳳’では，Ｓ果実は地色が暗く，‘清水白桃’のＬ果実は着色が濃いが色調が暗く，‘白麗’のＬ果実は着色が薄くて黄色が強く，いずれも外観が劣った．果汁中の主要な甘味成分であるスクロース＋フルクトース含量は，‘白鳳’，‘清水白桃’および‘白麗’ではＳまたはＬ果実で高く，酸味成分のリンゴ酸＋クエン酸含量は，それら３品種のＬ果実で最も低かった．‘橋場白鳳’では果実サイズによる糖・酸含量の有意な差がなかった．果実に苦みを与えるアスパラギン含量は，‘橋場白鳳’と‘白鳳’ではＬ果実で高かったが，‘清水白桃’と‘白麗’ではどのサイズでも含量が低かった．モモ香の主成分であるγ-decalactoneは，‘橋場白鳳’ではＬ果実で高かったが，‘白鳳’と‘清水白桃’ではＭ果実で，‘白麗’ではＳ果実で高かった．官能テストの結果，‘白鳳’のＬ果実と‘白麗’のＳ果実は食味が劣った．これらの結果から，岡山の「白桃」を代表する‘白鳳’，‘清水白桃’，‘白麗’の大果は，中程度の大きさの果実より甘味と酸味が低く，アロマが弱いなど，食味が薄く，肉質も劣ると考えられる．