INITIAL LOW OXYGEN STRESS (ILOS) CONTROLS SCALD OF APPLES WITHOUT USING POSTHARVEST CHEMICAL TREATMENTS
Numerous countries have banned the use of diphenylamine (DPA), so other means must be developed to control scald of apples. Our objectives were: 1) to develop alternative strategies to control scald of apples, to avoid applying postharvest treatment with the scald inhibitor DPA and/or fungicides to ensure fruit quality and food safety. 2) to determine the physiological and biochemical bases of apple scald. Preclimacteric Law Rome and Granny Smith apples were subjected to ILOS at 0.5 and 0.25% O2 for two weeks at 1°C, and stored in dynamic (slowly ventilated) controlled atmosphere (CA) at 3 or 1.5% O2 at 1°C as well as in air and in CA prior to low oxygen stress. Examination of fruit for scald and other physiological and pathological disorders was made after storage plus one week in air at 20°C. -Farnesene, 6-methyl-5-hepten-2-one (MHO) and other volatiles were measured with GC/MS through headspace sampling by solid phase micro extraction (SPME). The effects of continuous low oxygen storage on production of volatiles and scald control were also studied. ILOS/CA controlled scald of all cvs. tested without using DPA. Moreover, flesh firmness was retained at near harvest values and other quality attributes were superior to those achieved by conventional CA storage at 1.5% O2 with 3% CO2 at 0°C throughout the storage period. The underlying basis for scald control by the ILOS/CA regimen appears to be related to a transient increase in fruit ethanol levels and ethanol-related metabolism during and after ILOS. This prevents the induction of scald potential that otherwise develops during the first month of storage at low temperature. The biochemical basis for scald is related to MHO derived from -farnesene. ILOS/CA significantly reduced the production of -farnesene and MHO, both during and following storage, in comparison to conventional CA. Commercial CA storage trials of ILOS confirmed its efficacy to control scald of apples. The ILOS/CA regimen is: ILOS at 0.5% O2 for 2 to 3 weeks at 0°C followed by raising the temperature to 3°C for 3 days and then holding a CA at 1.5% O2 with 3% CO2 for the duration of the storage period at 0 to 1°C.
Wang, Z. and Dilley, D.R. (2001). INITIAL LOW OXYGEN STRESS (ILOS) CONTROLS SCALD OF APPLES WITHOUT USING POSTHARVEST CHEMICAL TREATMENTS. Acta Hortic. 553, 261-266
Volatiles; α-farnesene; 6-methyl-5-hepten-2-one; ethanol; CA regimen; hypobaric storage