Effect of harvest date on off-flavor development in mandarins following postharvest wax application

Authors: Obenland, David - Dave; ARPAIA, MARY LU - University Of California

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2018
Publication Date: 11/26/2018
Citation: Obenland, D.M., Arpaia, M. 2018. Effect of harvest date on off-flavor development in mandarins following postharvest wax application. Postharvest Biology and Technology. 149:1-8. https://doi.org/10.1016/j.postharvbio.2018.11.010.
DOI: https://doi.org/10.1016/j.postharvbio.2018.11.010

Interpretive Summary: Mandarins are prone to off-flavor formation following the postharvest application of wax, and it had been observed that fruit harvested later in the season sometimes have more off-flavor than fruit picked earlier. To more fully evaluate the seasonality effect on off-flavor and to determine potential causes for it ‘Owari’ and ‘China S-9’, two Satsuma varieties, were harvested at three to four dates within the harvest season, waxed, and placed into storage. The testing was conducted over three seasons with ‘W. Murcott’, a non-Satsuma variety, being included in the third season. At the end of the storage period in the first two seasons the fruit were evaluated for flavor using a semi-expert sensory panel. In all three seasons analyses were conducted for various parameters related to fruit internal gas composition. Consistently, in seasons 1 and 2 where flavor was evaluated, both Satsuma varieties did not develop off-flavor or a loss in overall flavor quality in the initial harvest. In subsequent harvests, however, off-flavor became increasingly noticeable and was correlated with the decline in overall flavor quality that occurred. Advancing harvest date in all three seasons was associated with a decrease in oxygen inside of the fruit and an increase in internal carbon dioxide, except in the case of ‘W. Murcott’ where there was little or no change in internal oxygen and an increase in carbon dioxide. Enhanced production of compounds related to off-flavor within the fruit occurred in fruit from the later harvests in the form of higher ethanol in the Satsuma varieties. Measurements of the ability for gases to pass through the peel performed in season 3 showed no meaningful relationship with the internal gas concentrations measured during the season. Respiration rate, however, strongly increased during the season in the Satsuma varieties and decreased in ‘W. Murcott’, both changes being associated with the measured internal gas composition inside the fruit. It is concluded that seasonality exists for the propensity for off-flavor to develop in mandarins, but that it may not occur in every instance. The potential mechanism modulating the change in the three varieties examined in this study appeared to be changes in the rate of respiration, which when respiration is sufficiently high, cause oxygen levels to decline to a level where fermentation occurs, and off-flavor is observed. Knowledge that seasonality in off-flavor development exists offers a potential tool to utilize in the prevention of its occurrence in that attempts can be made to harvest those varieties that are susceptible to off-flavor early rather than late in the season.

Technical Abstract: Mandarins (Citrus reticulata Blanco) are very prone to off-flavor formation following the postharvest application of wax and it had been previously observed that fruit harvested later in the season sometimes had more off-flavor. To more fully evaluate the seasonality effect on off-flavor and to determine potential causal mechanisms for it, ‘Owari’ and ‘China S-9’, two Satsuma varieties, were harvested at three to four dates within the harvest season, waxed, and placed into storage for either 2 weeks at 5 °C or 1 week at 5 °C + 1 week 20 °C, the later treatment being expected to develop off-flavor. The testing was conducted over three seasons with ‘W. Murcott’, a non-Satsuma variety, being included in the third season. At the end of the storage period, in the first two seasons, the fruit were evaluated for flavor using a semi-expert sensory panel. In all three seasons analyses were conducted for various parameters related to fruit internal atmosphere composition. Consistently, in seasons 1 and 2 where flavor was evaluated, both Satsuma varieties did not develop off-flavor or a loss in acceptability in the initial harvest. In subsequent harvests, however, off-flavor became increasingly noticeable and was correlated with the decline in flavor acceptability that occurred. There were occasional impacts on other flavor attributes, but the results were inconsistent. Advancing harvest date in all three seasons was associated with a decrease in internal oxygen and an increase in internal carbon dioxide, except in the case of ‘W. Murcott’ where there was little or no change in internal oxygen and an increase in carbon dioxide. Enhanced fermentative metabolism was indicated in the later harvests in the form of higher ethanol in the Satsuma varieties. Peel gas permeance measurements performed in season 3 showed no meaningful relationship with the internal gas concentrations measured during the season. Respiration rate, however, strongly increased during the season in the Satsuma varieties and decreased in ‘W. Murcott, both changes being associated with the internal gas composition. It is concluded that seasonality exists for the propensity for off-flavor to develop in mandarins, but it does not occur in every instance. The potential mechanism modulating the change in the three varieties examined in this study appeared to be changes in the rate of respiration, which when respiration is sufficiently high, cause oxygen levels to decline to a level where fermentation occurs, and off-flavor becomes apparent.