Influence of cold storage prior to and after ripening on quality factors and sensory attributes of ‘Hass’ avocados

Abstract

Partially-ripened avocados are often held in cold storage in an attempt to enable the consistent delivery of ripe fruit to food service or retail outlets. It is also common to hold fruit without any prior ripening for a few days to several weeks prior to ethylene treatment and final ripening. The purpose of this study was to determine the impact of these practices on ripening time and subsequent fruit quality. ‘Hass’ avocados were harvested from three different orchards on six harvest dates and placed at either 5°C or 12°C immediately after harvest or after ripening to average firmness values of either 80N (partially ripe) or 19N (near ripe). After storage the fruit were then ripened to eating firmness (4.4–6.7N) and evaluated for quality parameters. A portion of the fruit at harvest firmness were stored for 0d, 7d, 14d or 28d and then treated with ethylene to ripen the fruit. Continual softening during storage resulted in fruit that had been ripened prior to storage being nearly at eating firmness at the end of 14d, especially those stored at 12°C. Stem end rot, body rot and pink staining of the vascular tissue occurred more frequently in the previously-ripened fruit after 14d, the severity being greatest at 12°C where the incidence exceeded 50% for both stem end rot and pink staining. Both harvest date and orchard influenced the amount of pink staining observed. Storage of firm fruit prior to ethylene treatment resulted in higher levels of both stem end rot and pink staining only when the storage time exceeded 14d. In an additional study to assess the impact of the storage of partially-ripened fruit on both quality and sensory characteristics, ‘Hass’ avocados were harvested six times at monthly intervals, ripened to approximately 16N firmness at 20°C and then placed at either 1°C or 5°C for 7d or 14d. Following storage the fruit were ripened to eating firmness and evaluated. The occurrence of fruit quality defects was not affected by the timing of ripening. Sensory panelists liked fruit ripened prior to or after cold storage equally well and there were no differences among the ripening treatments, within a storage time, in the level of rich, nutty or grassy attributes that composed the fruit flavor. There were statistically-significant differences in the degree of textural creaminess among the ripening treatments, although these differences were inconsistent and slight. Storing partially ripe ‘Hass’ avocados for up to 4d at either 1°C, 5°C or 12°C does not greatly alter avocado quality, while storage for longer periods, such as 14d, may be problematic due to enhanced development of decay and pink staining, especially at higher temperatures. Holding unripe avocados for longer than 14d prior to ethylene treatment may predispose the fruit to the development of pink staining.