RELATIONSHIP BETWEEN DRY MATTER AND RIPENING TIME IN 'HASS' AVOCADO

‘Hass’ avocado fruit harvested early in the season take a longer time to ripen than fruit harvested later in the season. As the harvest season progresses, the dry matter content of fruit increases. Dry matter can be quantified by near-infrared spectroscopy (NIR). The objective of this study was to determine the relationship between fruit dry matter content and the time taken to ripen, and whether NIR can be used to grade fruit for time to ripen. ‘Hass’ avocado fruit were taken from field bins on the day of harvest from three orchards on three occasions: early, mid and late season. At each harvest, 150 fruit, approximately count 23, were taken per orchard, of which 100 fruit were used to determine time to ripen/dry matter relationship and estimate dry matter by NIR, and 50 fruit were used for NIR calibration. Fruit were allowed to ripen at 20°C without prior cold storage. Throughout the harvest season there was a relationship between higher dry matter and shorter time to ripen, although there was considerable variability in ripening time at any given dry matter (R²=0.25). Within a single harvest, with a limited range of dry matter and time to ripen, there was a less clear relationship between dry matter and the rate of ripening. Fruit from different orchards with similar dry matter may have different ripening times. Given the relationships established, it remains to be demonstrated whether NIR could be routinely used to segregate fruit into commercially useful ripening categories.