Using the Streif Index as a final harvest window for controlled-atmospherestorage of apples

A final harvest window (FHW), expressed as Streif Index coefficients [firmn ess/(percentage soluble solids concentration x starch index)], was develope d for identifying maximum fruit quality for strains of 'McIntosh', 'Cortlan d', and 'Jonagold' apples (Malus x domestica Borkh.) following 8 months of controlled-atmosphere (CA) storage. The Streif Index was calculated during nine preharvest (twice per meek) intervals and four weekly harvests over th ree seasons. The relationship between Streif Index (dependent variable) and day of year (independent variable) of the preharvest and harvest samples w as then derived by negative first-order linear regression equations that ha d parameter estimate (b(1)) probability values less than or equal to 0.0001 for all of the strains. Apples from the four harvest periods were stored i n standard CA storage for 8 months and then subjected to a 7-day shelf-life test at 0 degrees C followed by 5 days at 20 degrees C. Poststorage qualit y data were categorized and combined to produce an overall fruit quality ra ting scale. For each strain, the final harvest (i.e., day of year) was iden tified as that which directly preceded at least a 10% drop in the poststora ge fruit quality rating compared with the first harvest rating. The FHW, ex pressed as Streif Index coefficients via the regression of Streif Index (Y) on day of year (X), was then calculated as the 3-year final harvest mean w ith the upper and lower window limits being determined by the standard devi ation of the mean. The lower to upper FHW boundaries ranged from 4.18 to 5. 34, 4.12 to 5.46, 4.51 to 5.68, 5.23 to 599, and 1.38 to 2.34 for Redmax, M arshall and Summerland 'McIntosh', Redcort 'Cortland' and Wilmuta 'Jonagold ', respectively. The practical utility of the Streif Index method lies in t he ease with which apple fruit maturity at harvest can be evaluated for its suitability for long-term CA storage.