Prediction model of avocado ripening process based on sensory quality at room temperature

Abstract: 'Hass' avocado is enjoyed by consumers worldwide due to its rich flavor, high overall quality and health related attributes. The nutritional and dense phytochemical composition of avocado is attracting more consumers. Avocados do not ripen on the tree and must be ripened after harvest, which means that most or all of the ripening process needs to be carefully controlled in the commercial postharvest environment. In view of the problems that the storage time and quality changes of avocado during the storage and transportation in the Chinese avocado market are difficult to be controlled, as well as that avocado is easy to be damaged, the color of the avocado peel, the hardness of the avocado pulp, and the sensory quality indicators at room temperature (25±1 ℃, 75% RH) were measured to monitor their intrinsic variation during ripening in this study. The Pearson correlation analysis between the affection degree of avocado flesh and the color difference, hardness, respiration rate, weight loss rate, respectively, was also performed. At last, the prediction model for the ripening of avocado was developed based on first-order functional equation, logistic equation of dry weight loss rate-and the color difference a* value-storage time. The results showed that the weight of avocado fruit decreased from 195.2(0.9 to 181.2(0.8 with the prolongation of storage time (0-9 d), and the daily weight loss rate and respiration rate increased first at the storage time of 0~3 d and then decreased sharply. Conversely, the peel color, characterized by L* (34.66(1.27), a* ((10.69(1.29) and b* values (18.31±1.56), changed significantly when the storage time was less than 3 d, and then tended to constant (~25.63, ~4.19, and~3.45, respectively). However, the avocado flesh hardness decreased from 144.2N to 8.04N during storing for 3 d and reached equilibrium when the storage time exceeded 3 h. Additionally, apart from the respiratory rate (r=(0.221), the dry weight loss rate, peel color (L*, a* and b* values), and avocado flesh hardness during storing at room temperature were significantly correlated with sensory preference scores (P<0.01), in which the dry weight loss rate (r=0.840)and a* value (r=0.915) were positively related to sensory preference scores, and flesh hardness (r=(0.954), L* (r=(0.947), and b* values (r=(0.952) were negatively related to sensory preference scores. Based on determination of the color of avocado peel were nondestructive, fast, convenient, herein a* value was selected as key indicators to establish the prediction model of avocado quality change during storing. At the storage time of 0-9 d, the a* value was fitted well based on logistic equation. R2 values was 0.993. In the validation experiments, when a* value less than 4, the predicted and the measured values have a good linear correlation, the decision coefficient is 0.996, indicating that the developed model can be used to predict the ripening period of avocado at room temperature when a* value less than 4. The research results in this work can provide favorable guidance and basis for quality control of avocado.