Vol. 81 No: 3

Title:
The influence of crop-load, delayed cooling and storage atmosphere on post-storage quality of 'Honeycrisp'™ apples

Authors:
JOHN M. DELONG, ROBERT K. PRANGE, PETER A. HARRISON, CHARLES G. EMBREE, DOUGLAS S. NICHOLS and A. HARRISON WRIGHT

pp: 391-396

Abstract:
The influence of crop-load, delayed cooling and storage environment on fruit quality and disorder, and on the incidence of rot was investigated on 7 year-old ´Honeycrisp` apple (Malus domestica Borkh.) trees on ´Malling 26` rootstocks at three different sites during 2003 and 2004. Fruit from non-thinned (control) trees, or trees thinned to three, six or nine fruit cm^-² trunk cross-sectional area (TCSA) were harvested and: (1) immediately cooled over 24 h to 3°C [commercial (Comm)] then stored at 3°C in refrigerated air (RA) or in a controlled atmosphere (CA; 2.5 kPa O₂, 1.0 - 1.5 kPa CO₂); or (2) held at 20°C for 6 d, followed by 1 d at 3°C [= 7 d pre-storage warming treatment = delayed cooling (DC)] then stored at 3°C under RA or in CA storage. After 3 and 6 months of storage, fruit mass (g), firmness (N), colour (% red), soluble solids content (SSC; %), titratable acidity (TA; mg malic acid equivalents 100 ml^-¹ juice), “greasiness” (0-3 scale), the extent of disorders such as soft scald (%) and low temperature breakdown (LTB; %), as well as the incidence of rot (%) were assessed. In general, as crop-load increased fruit mass, firmness, colour, SSC and TA decreased regardless of the effects of DC and storage treatment. Crop-load did not influence fruit “greasiness” and had an inconsistent and less-pronounced effect on soft scald, LTB and rot. The 7 d pre-storage warming treatment reduced the incidence of soft scald and LTB, irrespective of crop-load, but had little influence on other fruit quality measurements. Although the storage environment did not consistently alter quality, CA-stored ´Honeycrisp` apples tended to be more acidic, less “greasy” and develop less soft scald. Overall, the data indicate that the highest fruit quality was attained by thinning ´Honeycrisp` trees as close to three fruit cm^-² TCSA as possible, by subjecting newly-harvested fruit to a 7 d pre-storage warming period of 20°C, followed by CA storage at 2.5 kPa O₂, 1 - 1.5 kPa CO₂ at 3°C.

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