Vol. 69 No: 3

Title:
Control of Superficial Scald in ‘Granny Smith’ Apples by Ultra-Low and Stress Levels of Oxygen as an Alternative to Diphenylamine

Authors:
A.B. TRUTER, J.C. COMBRINK and S.A. BURGER

pp: 581-1129

Abstract:
‘Granny Smith’ apples were harvested at weekly intervals, commencing approximately 155 d after full bloom (DFFB), over two successive seasons. Subsamples of the fruit were stored for periods of five and six months, without the application of diphenylamine, under regular atmosphere (RA) (1990/91 season only), and ultra-low oxygen (ULO) controlled atmosphere (CA) conditions. Further samples were subjected to initial low oxygen stress (ILOS) conditions before ULO CA storage. During the 1989/90 season, scald development after five months' storage was low for fruit which had been picked in the pre- and post-maturity phases, but high on fruit picked at optimum maturity (170 DFFB). Although storage regime had little effect on scald development after five months' storage, the ILOS + ULO CA treatment resulted in lower levels of scald on the post-mature fruit after six months of storage than was the case under ULO CA storage alone. There was more scald in the 1990/91 season than in the previous season. Under RA storage conditions, scald levels were high after both five and six months of storage, and decreased only slightly the later the apples were picked. Relative to RA, storage under ULC CA conditions led to markedly lower scald levels on the post-mature fruit, but did not greatly reduce scald on the pre-mature and mature fruit. Storage under the ILOS + ULO CA regime, however, conferred low levels of superficial scald on pre-mature, mature and post-mature fruit after both five and six months of storage. These results suggest that although superficial scald on ‘Granny Smith’ apples can be inhibited by a combination of ILOS and ULO CA storage, the development of scald is also affected by factors other than maturity and storage period.

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