Carbohydrate dynamics in kiwifruit

Rates of fruit growth, on-vine changes in the soluble and insoluble carbohydrate pools, and subsequent changes during storage were examined on kiwifruit from vines having moderate to very high crop loads (20-50 fruit m^-2). In accord with previous studies, vines carrying the highest loads exhibited a 18% decrease in mean fruit weight and a two-fold increase in total yield compared with those having the lowest crop loads. Rates of dry-matter accumulation in the fruit varied in proportion to total yield and remained constant over the entire season - a result that deserves further investigation. Effects of crop loading on the carbohydrate composition of fruit were small and after reviewing the available literature we conclude that the primary determinants of fruit composition are genetic and climatic. Relationships between the various fruit quality variables were used to develop a predictive model of soluble solids concentration of fruit at eating ripeness from harvest measurements of fruit density (weight per unit volume) or dry matter. The accuracy of these predictions are of the order of 1% (w/v). The rate of change in soluble solids during storage at 0°C is shown to follow a simple exponential function of time with a time constant of 20 d.