Modeling the relationship between postharvest storage conditions and grapefruit quality

The postharvest loss in quality of grapefruit during storage can be quantified by determining the change of the quality traits of grapefruit, including total soluble solids (TSS), titratable acidity (TA), TSS/TA, weight loss (WL), and the development of decay (DC) and chilling injury (CI). The objective of this study was, therefore, to develop models that encompass the relationship between both storage conditions and duration and the quality traits of grapefruit to predict the loss of grapefruit quality during storage. The models of TSS, TA and TSS/TA were developed with experimental data collected during the 2007–08 and 2008-09 growing seasons that were obtained from the literature. The models for WL, DC, and CI were developed with experimental data collected in Florida during the 2004–05 and 2005-06 growing seasons. The WL, DC and CI models were applied to determine storage life. The results indicated that there was a second-order polynomial relationship between storage duration and TSS and linear relationships between storage duration and TA and TSS/TA. A longer storage duration resulted in a higher TSS, a lower TA and a higher TSS/TA. There were linear relationships between storage duration and WL, thermal time above a threshold temperature of 0 °C and DC and thermal time below 10 °C and CI, with higher WL, DC and CI resulting from longer storage duration and larger number of thermal times. Model performance for simulating TSS, TA, TSS/TA for storage temperature between 2 °C and 11 °C was good. There is good performance for simulating WL for storage temperature between 4 °C and 12 °C, DC for storage temperature of 21.1 °C, and CI for storage temperature of 4.4 °C. Following model development, it was applied to determine the optimum storage life. Optimum storage condition was a storage temperature of 7.6 °C for approximately 20 d, resulting in less than 5 % of the stored fruits lost due to unacceptable quality based on predictions for WL, DC and CI.