Studies on the physical properties and preservation of the North American pawpaw (Asimina triloba) fruit

The North American pawpaw (Asimina triloba) fruit is an annonaceous fruit that belongs in the same family as tropical fruits like soursop, cherimoya, atemoya, and others. Pawpaw is the only fruit in the Annonaceae family that grows in temperate regions of the world. The fruit is native to the United States and grows in over 30 states in the United States including Missouri, Indiana, Ohio, Illinois, and parts of Texas. The fruit has remained underutilized and uncommercialized for several centuries. The main factors that have contributed to it being underutilized and uncommercialized are the rapid changes in quality that occur in the fruit after it is harvested. The fruit loses firmness, and the color of the skin rapidly changes from yellowish green to brown or black within 3-5 days. This study aims to evaluate the physical characteristics of different cultivars of the pawpaw fruit to gain insights into its processing potential, test correlations between noninvasive parameters like skin color and invasive parameters like textural properties to establish noninvasive ripening indicators and compare the effect of edible coatings on the quality of pawpaw fruits during storage. The findings from the study show that among the cultivars studied, the Susquehanna cultivar has the highest fruit weight and pulp yield, while the Overleese cultivar has the highest juice content, making the Susquehanna cultivar potentially suitable for fruit processing operations that require high pulp yield and the Overleese cultivar potentially suitable for fruit juice processing. Also, all the cultivars studied had peel thickness between 0.21 and 0.72mm, making them highly susceptible to bruising and eventual postharvest losses if they are not handled carefully. Further, analyses of the textural properties show that the ripe pawpaw fruits have a hardness of 2.2 [plus or minus] 0.5 kg-force, similar to the hardness of green ripe mangoes but harder than green ripe bananas, and the unripe fruits have a hardness of 68.2 [plus or minus] 10.9 kg-force. Although skin color had previously been thought to be a poor indicator of pawpaw fruit ripeness, the results from the correlations show that there are statistically significant strong negative correlations between the fruit skin color a* values (greenness) and hardness (r = -0.87), chewiness (r = -0.86), and cohesiveness ratio (r = -0.73), and a strong positive correlation with total soluble solids (r = 0.90). The skin hue angles also have strong positive correlations with hardness (r = 0.86), cohesiveness ratio (r = 0.74), and chewiness (r = 0.86), and a strongly negative correlation with total soluble solids (r = -0.91). Hence, instead of determining the ripeness of the fruit using hardness which is an invasive method, noninvasive parameters like the skin color greenness and hue angles can be used to determine pawpaw fruit ripeness. In addition, the results from the preservation studies show that chitosan coatings are more effective in slowing moisture loss in Sunflower fruits than in Susquehanna and 10-35 fruits over time. The TOPSIS-Shannon entropy analyses showed that the 10-35 fruits with 1 percent chitosan had the most stable quality over time, followed by the Susquehanna and Sunflower fruits with 2 percent chitosan coatings. The experimental data from different cultivars, treatments, and storage conditions proved the shelf-life of pawpaw fruit could be extended from 5 days to 15-20 days depending on the cultivar. These findings will enable the creation of markets for pawpaw fruits and allow countries that grow them to generate revenue from this underutilized specialty crop