Max E Patterson

Ester biosynthesis in “Rome” apples subjected to low-oxygen atmospheres

Abstract The relationship between acetate ester-forming activity of acetyl CoA alcohol transferase (ACAT), non-ethylene volatile emission, and flesh volatile content of “Rome” apples ( Malus domestica Borkh.) after removal from 9 months storage in low-oxygen environments was investigated. Apple samples held at 0–1°C were removed from refrigerated air (RA) or controlled-atmosphere (CA) storage at 1.0 or 0.5% v/v O 2 /1% CO 2 and placed in ambient laboratory conditions. Every three days fruit flesh and headspace were analyzed for volatile compounds using capillary gas chromatography. Acetate ester forming activity was assayed spectrophotometrically on partially-purified extracts of cortical tissue. Patterns of acetate ester formation depended upon storage environment and alcohol moiety precursor. Ethyl acetate content was always higher in the headspace and flesh of RA fruit, regardless of time after storage. Propyl acetate concentrations in CA stored apple flesh were higher until post-storage day 12 when they decreased. Headspace propyl acetate levels were higher in RA controls until days 9–15 when more emanated from CA fruit. Butyl acetate concentrations were lower in flesh and headspace of CA fruit until day 15, when RA fruit headspace levels decreased. Headspace and flesh concentrations of 2-methyl-1-butyl acetate were higher in CA apples. Acetate ester-forming activity was detectable at day 0 in 1.0% oxygen-stored fruits, but not in 0.5% oxygen-stored fruits. By post-storage day 9, ACAT activity in CA apples reached maximal levels, only to decrease by day 15. RA-stored apples had more ACAT activity at day 0, but did not substantially increase in activity like the 0.5% oxygen-stored apples removed from CA storage. It is unknown whether the ACAT protein is reactivated by exposure to ambient oxygen or synthesized de novo.

Effects of ethephon on the respiration and ethylene evolution of sweet cherry (Prunus avium L.) fruit at different development stages.

Abstract The role of ethylene on sweet cherry ( Prunus avium L.) fruit respiration was studied at three stages of development. An ethylene-releasing compound, ethephon [(2-chloroethyl)phosphonic acid], was applied at concentrations from 10 to 1000 ppm to straw-, pink- and mahogany-colored fruits. Depending upon the ethephon concentration applied, rates of ethylene evolution as high 6 μl C 2 H 4 kg fruit −1 h −1 were detected. Ethylene evolution was undetectable from untreated, mature fruits. Fruit respiration rates declined at all stages, regardless of the rate of ethylene evolved. Ethephon did not affect the firmness of mature, mahogany-colored sweet cherry fruit. These results confirm that sweet cherry fruit are nonclimacteric because untreated fruit produced neither respiratory nor ethylene peaks near maturity. Respiration was not stimulated in the presence of exogenous ethylene during these later stages of sweet cherry fruit development, as it is in other nonclimacteric fruits.