What was it all about?

In response to an identified 3000 to 5000 tonne market niche for light-coloured Sultana-type dried vine fruit, this project investigated how to consistently produce light-coloured dried fruit.

Researchers undertook trials on grape maturity, and on the use of covers to protect drying grapes, to look at the effects of both on dried fruit colour.

The maturity component examined the relationship between berry maturity at the time that drying is initiated and final dried fruit colour. Crop loads were manipulated and multiple harvests were used to produce a range of maturities. Grapes were dried either in an oven to remove the effect of weather on final fruit colour, or on an open rack.

The use of plastic covers, as used in the table grape industry to prevent rain-related grape splitting, was investigated on summer-pruned Sultana and Sunmuscat to assess the impact of covers on the microclimate in the drying canopies.

Key findings included…

• Weather during drying was the single biggest influence on final colour, with rain during drying resulting in darker dried fruit
  
  
• There was no colour darkening associated with high crop loads
  
  
• Getting crops to mature sooner and dried quickly following summer pruning assists in obtaining the desirable colour
  
  
• Final dried fruit colour was unaffected by covers, but the colour intensity was marginally greater.

The findings suggested that adoption of earlier maturing rain-tolerant varieties will best meet the demand for light-coloured dried vine fruit.