BRUISING ON BLUSH AND NON-BLUSH SIDES IN APPLE-TO-APPLE IMPACTS

Abstract

A study of how bruising during apple-to-apple impact varied between the blush (red) and non-blush (green)sides of an apple has been conducted using McIntosh apples. The relationships between bruise position, contact area,bruise surface area before and after skin removal, bruise visibility, bruise volume, and bruise depth were also consideredfor early- and mid-maturity fruit. Tissue firmness was measured by two destructive methods and related to bruising duringthe experiments. Bruising was created by controlled impact tests conducted about one week after picking. To reducevariability between apples, a procedure was used in which apples were cut into red and green halves, which were thenimpacted against one another.<br><br>The study showed there were differences in the extent of bruising between the two sides, even though the total bruisevolume caused by an impact was similar, regardless of which sides of apples were involved. In impacts involving red andgreen sides, the green (non-blush) sides were bruised more frequently, and were generally larger. The overall bruisevolume (i.e., the total volume produced in 10 separate apple to apple impacts) on the green side was two to three timeslarger in one experiment and 1.1 to 1.6 times greater in the other. Bruises on the green side were also more readily visiblethan those on the red side. Bruise surface area estimates prior to skin removal consistently overestimated the area ofbruising, by up to 25%. This was greatest for small bruises on red sides. Bruise surface area measurements alone (with orwithout skin removal) did not give a reliable indication of bruise volume in apple-to-apple impacts, due to the largevariation in bruise depths. Impacting red and green sides of the same apple against each other appeared to increase thedifferences between the two sides slightly (compared to impacting sides selected at random). A statistical analysissuggested that the technique of studying impacts between halves of the same apple may reduce between fruit variability inapple-to-apple impact studies.