Vol. 77 No: 1

Title:
Changes in moisture, dry matter and soluble sugars of dry-on-the-vine raisins with special reference to sorbitol

Authors:
H. AUNG, D.W. RAMMING and R. TARAILO

pp: 100-105

Abstract:
The moisture, dry matter and soluble sugar composition of Vitis vinifera L. advanced selections of dry-on-the-vine raisins were determined over several seasons. Moisture loss from post-veraison berries occurred in a graduated stepwise manner, with a rapid decline from an initial 86±2% to 60±5% 108 d from first bloom, a slower loss and a final accelerated loss to 25±4% after 151 days from first flowering. The pattern of dry-matter accumulation was similar in large, medium, or small berries but dry matter was higher in large (0.65±0.04 g dry wt. per berry) than medium (0.52±0.03 g dry wt. per berry) or small (0.36±0.03 g dry wt. per berry raisin). Incipient browning was seen with raisin formation at the distal berry region with a higher sugar concentration than in the proximal (pedicel) region. Sucrose in the raisins exhibited two maxima, one (1.4±0.2 mg g^-1 fresh wt.) 96 d from first bloom, and a second (2.4±0.4 mg g1^-1 fresh wt) 123 d after first bloom, with each maximum occurring before the rise in glucose, fructose, and sorbitol, and decreasing as these sugars increased. Sorbitol was not detected initially in mature berries, but increased in raisins. It was proposed that sorbitol or its biosynthetic enzyme might be useful for determining raisin harvest. Raffinose and sucrose contents of the peduncle were higher than raisins and may indicate a role of these sugars in the physiology of the peduncle

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