Comparative analysis of aroma compounds in ‘Bartlett’ pear in relation to harvest date, storage conditions, and shelf-life

Abstract

In this study ‘Bartlett’ pear fruit from two harvest dates were stored under normal atmosphere and ultra-low oxygen (ULO: 0.8kPa O2, <0.5kPa CO2) at +1°C and −1°C. Storage under ULO at −1°C greatly delayed ripening, as demonstrated by maintained firmness and suppressed synthesis of aroma volatiles after storage. ULO storage also suppressed synthesis of esters, including two character-impacting compounds: methyl and ethyl (2E,4Z)-deca-2,4-dienoate. Synthesis of hexyl acetate was suppressed under ULO storage regardless of temperature, while ethyl acetate synthesis was suppressed only by ULO at −1°C. The levels of most aroma volatiles were recovered after the following 10 d of shelf-life, although with significantly lower recovery for methyl and ethyl (2E,4Z)-deca-2,4-dienoate in fruit under ULO storage. Although synthesis of aroma volatiles was most suppressed under ULO at −1°C, butyl and hexyl acetate levels recovered better in fruit under ULO storage at −1°C than at +1°C. Acetaldehyde and nonanal were the principal aldehydes present, with levels that were higher in early harvested fruit and in fruit stored at +1°C. Using multivariate analysis, we found two clusters one for after storage and the other for after shelf life samples, with the exception of pears after storage and after shelf life at +1°C and normal atmosphere positioned on the lower side of graph Overall, this analysis discriminated between mentioned storage conditions that are specifically defined by hexylacetate and decanal on the one side and ethyl butanoate, pentyl acetate and α-farnesene on the other side.