D. Scott Mattinson

Relationship of harvest maturity to flavor regeneration after CA storage of ‘Delicious’ apples

Red Delicious producers in the USA face increased pressure to produce fruit with optimum ‘on-shelf’ dessert quality following storage. In addition to firmness and soluble solids measurement other ripening-related events affect flavor perception. Ester production is always closely linked to the onset of climacteric ripening, while prolonged low-oxygen storage is usually detrimental to volatile production. Experiments focused on timing of the optimum harvest for maintaining sweetness, sourness and aroma generating capacity during CA storage. In multiple-harvest experiments with ‘Redchief Delicious’ apples, we investigated the relationship between the internal ethylene maturity indicator and flavor retention and regeneration after storage for different lengths of time. Using a cohort of untrained panelists, it was found that overall flavor perception and perceived fruit ripeness begins to increase at the onset of the climacteric. CA conditions reduce post-storage volatile production when compared with those stored in refrigerated air although not to a level below those displayed in ‘over-mature’ fruit at harvest after 3 months in storage. As harvest maturity advanced, the time required to regenerate aroma volatiles to an ‘optimum’ level after removal from CA storage decreased markedly. A linear relationship between attainment of optimal eating quality and time out of storage was established. Firmness, soluble solids, and titratable acidity of fruit from all harvest dates remained at acceptable levels throughout the post-storage ripening period.

Alteration of foliar flavonoid chemistry induced by enhanced UV-B radiation in field-grown pinus ponderosa, Quercus rubra and Pseudotsuga menziesii

Chromatographic analyses of foliage from several tree species illustrate the species-specific effects of UV-B radiation on both quantity and composition of foliar flavonoids. Pinus ponderosa, Quercus rubra and Pseudotsuga menziesii were field-grown under modulated ambient (1x) and enhanced (2x) biologically effective UV-B radiation. Foliage was harvested seasonally over a 3-year period, extracted, purified and the flavonoid fraction applied to a mu Bondapak/C(18) column HPLC system sampling at 254 nm. Total flavonoid concentrations in Quercus rubra foliage were more than twice (leaf area basis) that of the other species; Pseudotsuga menziesii foliage had intermediate levels and P. ponderosa had the lowest concentrations of total flavonoids. No statistically significant UV-B radiation-induced effects were found in total foliar flavonoid concentrations for any species; however, concentrations of specific compounds within each species exhibited significant treatment effects. Higher (but statistically insignificant) levels of flavonoids were induced by UV-B irradiation in 1- and 2-year-old P. ponderosa foliage. Total flavonoid concentrations in 2-year-old needles increased by 50% (1x ambient UV-B radiation) or 70% (2x ambient UV-B radiation) from that of 1-year-old tissue. Foliar flavonoids of Q. rubra under enhanced UV-B radiation tended to shift from early-eluting compounds to less polar flavonoids eluting later. There were no clear patterns of UV-B radiation effects on 1-year-old P. menziesii foliage. However, 2-year-old tissue had slightly higher foliar flavonoids under the 2x UV-B radiation treatment compared to ambient levels. Results suggest that enhanced UV-B radiation will alter foliar flavonoid composition and concentrations in forest tree species, which could impact tissue protection, and ultimately, competition, herbivory or litter decomposition.