|Obenland, David - Dave|
|Arpaia, Mary Lu|
Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2012
Publication Date: 9/1/2012
Citation: Obenland, D.M., Collin, S., Sievert, J., Arpaia, M. 2012. Influence of maturity and ripening on aroma volatiles and flavor in avocado. Postharvest Biology and Technology. 71:41-50. Interpretive Summary: The percentage of dry matter present in the flesh of avocados is used to determine harvest maturity although it is recognized that this is an inexact and incomplete measure of eating quality. Changes in flavors and other sensory aspects of the fruit were measured during maturation and ripening and related to the concentrations of aroma compounds present to help more fully understand the influences of maturation on avocado flavor. As maturation progressed sensory panelists found the likeability of the fruit to increase, coinciding with the fruit becoming creamier and less watery in texture, and flavor richer and less grassy. Changes in a number of aroma compounds were found to potentially responsible for the some of the observed flavor changes. Aroma compounds were also found to change in amount during ripening that also could impact overall flavor. Understanding how flavor develops in avocado and what factors impact this development aids in helping to provide consumers with avocados of optimum flavor quality.
Technical Abstract: Changes in aroma volatiles were determined using solid phase microextraction (SPME) and gas chromatography in ripe avocados (Persea americana Mill.) throughout an eight-month maturation period and related to the sensory properties of the fruit. As maturation progressed sensory panelists found the likeability of the fruit to increase, coinciding with the fruit becoming creamier and less watery in texture, and flavor richer and less grassy. During this maturation time the concentration of hexanal, (E)-2-hexenal and 2,4-hexadienal, three of the most abundant volatiles, greatly declined in amount. These volatiles all have a grass-like aroma and it is likely that the loss in amount was responsible for the decline in grassy flavor during maturation. Acetaldehyde, methyl acetate, pentanal, and ß-myrcene were at higher concentrations in mature than non-mature fruit and may also have contributed to the overall flavor. Avocados of an intermediate maturity were ripened at 20°C and fruit of different ripeness levels (firmnesses) measured for ethylene production, rate of respiration and aroma volatile content. A sharp increase in the rates of respiration and ethylene production marked a rapid increase in softening and the beginning of the climacteric. Seventeen volatiles were identified in the ripening avocados of which three (pentanol, hexanol, and 2-nonenal) were not detectable in fully-ripe fruit. Of particular interest was a 85% decline in the amount of hexanal in a comparison of firm to fully ripe (4 N firmness) fruit. It is possible that declining lipoxygenase and/or hydroperoxide lyase activities may be responsible for the reduction. Aroma volatiles have in the past been little-studied in avocados but appear to have a role in determining the flavor of the fruit.