Project Number: 5350-43000-005-10
Project Type: Trust

Start Date: Jul 01, 2007
End Date: Jun 30, 2012

Objective:
1. Characterize pear peel metabolic profiles during air and CA storage under conditions known to enhance or suppress development of superficial scald and speckling. 2. Identify lot specific metabolic profiles that are indicative of susceptibility to development of superfical scald and speckling.

Approach:
Multiple lots of `d¿Anjou¿ pears will be held in a range of storage environments (temperature, gas composition) known to promote or avoid development of peel disorders. The low oxygen setpoint will be based in part on an assessment of the oxygen concentration at which a change in peel chlorophyll fluorescence occurs. Incidence and severity of peel disorders as well as fruit quality (firmness, weight, color, soluble solids content, titratable acidity, volatile production) will be assessed bimonthly during an 8 month storage period. At harvest and after removal from storage, peel tissue samples will be collected, flash frozen in liquid nitrogen, then stored at -112 degrees fahrenheit until used for metabolic profile analyses. Fruit analyses. Firmness will be assessed using a penetrometer). Color will be evaluated visually using a chart where 1=green, 5=yellow, and also using a chromameter. Soluble solids content and titratable acidity will be analyzed in fresh juice using a refractometer and autotitrator. Respiration rate and ethylene production will be assessed using gas chromatography. Emissions of other volatile compounds will be characterized by collecting samples at the outlet of glass jars containing whole pear fruit onto adsorbent traps. Adsorbent traps will be desorbed using a thermodesorber into a gas chromatograph equipped with a mass selective detector. Metabolic profiles of non-volatile compounds will be characterized using GC/MS and LC/MS. For GC/MS, ground peel will be extracted with methanol containing internal standards. The extract will be clarified by centrifugation, and aloquots of the supernatant will be dried under a stream of N 2(subscript)(g), derivatized using methoxamination at 86 degrees fahrenheit for 90 min followed by silation (BSTFA) at 99 degrees fahrenheit for 30 min. Sample components analyzed using GC/MS will be identified and quantified using a combination of techniques including comparison with standards, and deconvolution of spectra for co-eluting compounds. Deconvoluted results will be evaluated with mathematical procedures designed to discover changes within a large group of components and how these components may be interacting. Using this technique, 100-200 or more compounds can be routinely evaluated and tracked in pear peel. LC/MS analyses will be utilized for pigments, isoprenes, large flavor precursors, phenolics, waxes, and other compounds. Ground peel will be extracted in an emulsion containing saturated CaCl 2(subscript), hexanes, and internal standards. The partitioned aqueous and hexanes phases will be concentrated using solid phase extraction (SPE). Concentrated SPE fractions will be analyzed using a LC/MS. Data will be deconvoluted, identified, and evaluated as for GC/MS. Documents Trust with Marketing Order #927, Pear Grown in Oregon and Washington. Log 32987.