Harvesting by Peel Color to Reduce Bruising of 'Golden Delicious' Apples

'Golden Delicious' apples were harvested at three peel color stages and equilibrated at 22 degrees C for 2 days before inducing bruising to a constant depth using an artificial silicon finger attached to an Instron universal material testing instrument. After 48 hr, bruised tissue was sliced sequentially from the fruit surface in a plane perpendicular to the direction of the applied force until discoloration was no longer evident. Thickness and discolored area of each tissue slice was measured using a digital caliper and total volume of bruised tissue was estimated. Analysis showed that there was a significant difference in bruise volume between green and yellow peel stages. Susceptibility to bruising of fruit at the white (intermediary) stage appeared to vary with environmental conditions (year to year). Compared with the previous year, the 2008 growing season was cooler and shorter and bruise volume at all stages was greater. Analysis of fruit maturity suggested bruise volume was influenced by ripening-induced changes in cell structure, size, and integrity. Where fruit peel color changed but flesh firmness did not, bruise volume increased. We conclude that peel color is a better indicator of bruise susceptibility than fruit flesh firmness.