A New Fruit Wine from Kiwifruit: A Wine of Unusual Composition and Riesling Sylvaner Character

Abstract

Initial attempts to make wine from kiwifruit (Chinese gooseberry, Actinidia chinensis Planch) using conventional wine practices were unsuccessful, the product being described as "grassy, green, stalky" in aroma and taste, and as being of unacceptable bitterness and astringency. A process was subsequently developed which produced a white table wine of outstanding character.

Juice was extracted from crushed fruit with a rack and cloth (pack) press. Yields of 55-60% were increased up to 84% by pectolytic enzyme or press-aid treatment of pulp before pressing. The juice composition is unusual in its high concentration of quinic (9 g/L) and ascorbic (1 g/L) acids. High acidity (20 g/L) and low sugar (100 g/L) necessitate juice amelioration for the production of balanced wines. Wines made by fermenting juice which had been clarified to "brilliance" with commercial pectolytic enzymes developed an intense "fruity, Riesling Sylvaner (Müller-Thurgau)-type" aroma during fermentation and retained no undesirable astringency or bitterness. The removal of astringency and bitterness correlated with a reduction in total phenols and removal of flavonoids.

The relationship between SO₂, ascorbic acid and dehydroascorbic acid in the juice and the wine was investigated. Juice and wine have considerable SO₂ binding power: at bottling, after the addition of 275 ppm of SO₂ during processing, 47% was present as SO₂ (11% free, 36% bound), 34% was oxidized to sulfate and 19% was unaccounted for. Addition of SO₂ is necessary to produce wines with maximum fruity Riesling Sylvaner-type character and good shelf life in the bottle. Wines made without SO₂ develop excessive brown color and an "oxidized" flavor during storage despite the presence of high concentrations of ascorbic acid (0.4 g/L). Such changes correlate with the loss of ascorbic acid and are markedly retarded by the presence of free SO₂.