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  • Author or Editor: Changzheng Wang x
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Pawpaw (Asimina triloba L.), a species of the eastern United States, bears the largest edible fruit of all native trees. Relatively little is known about ripening of pawpaw, and several problems, such as short shelf life and duration of harvesting, hamper pawpaw production. While previous investigations have resulted in identifying physical properties associated with ripening, the effects on phenolic content and antioxidant capacity have not been investigated. The objectives of the study were to investigate changes in phenolic content and antioxidant capacity and to identify physical parameters of pawpaw pulp during ripening. Sample extraction of pawpaw was achieved by adding acetone (2 mL/1 g of sample) to pulp of a pawpaw cultivar, PA Golden, and then vortexing (30 s) and sonicating (15 min) the sample and solvent, prior to centrifugation (15 min) twice at 2987 × g. Folin-Ciocalteu assay and ferric reducing antioxidant power (FRAP) assay were used for the estimation of phenolic content and the antioxidant capacity, respectively. While soluble solid content increased during ripening, the hardness of the fruit decreased, confirming previous reports. The pulp of unripe fruits had the greatest phenolic content (gallic acid eq. 131.2 mg/100 g FW) and antioxidant capacity (Trolox eq. 22.7 μM/g FW), which decreased by about 20% as the fruit ripened. Of three color properties measured, chroma, an estimate of color saturation, increased with ripening, while lightness of pawpaw pulp remained the same. A high correlation was found between chroma and hardness of fruits (r = 0.62), and between phenolic content and antioxidant capacity of pawpaw pulp (r = 0.80), suggesting these parameters can be incorporated into methods to estimate the ripeness of pawpaw fruit.

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Pawpaw [Asimina triloba (L.) Dunal], a native species of the eastern United States, bears the largest edible fruit of all indigenous trees. Chemoprotective properties of fruits have been partly attributed to phenolics such as gallic acid and chlorogenic acid, and the phenolic content generally correlates with antioxidant capacity for various kinds of fruits. Despite many reports of commonly available fruits, little information is available on phenolic content or antioxidant capacity for currently underused fruits. The objectives of this study were to determine the phenolic content (PC) and antioxidant capacity (AC) in fruit of two pawpaw cultivars at different stages of ripening. Sample extraction of pawpaw was achieved by adding acetone (2 mL/1g of sample) to the pulp of ‘PA-Golden (#1)’ and advanced selection 1-23, and then vortexing (30 s) and sonicating (15 min.) the sample and solvent before centrifuging it (15 min) twice at 2987 g. Folin-Ciocalteu assay and ferric reducing/antioxidant power assay were used for the estimation of PC and AC, respectively. PC and AC tended to decrease with ripening of fruit. The highest AC was found in the semiripe ‘PA-Golden (#1)’ puree (22.06 μmol TE/g fresh weight), whereas the puree of ripe fruit contained the lowest AC (17.04 μmol TE/g fresh weight), about a 23% decrease. In contrast, the greatest PC and AC were observed in intermediate fruits for 1-23. A positive correlation was found between PC and AC of fruit of ‘PA-Golden (#1)’ (r = 0.62) and 1–23 (r = 0.82). These results suggest that phenolic components of pawpaw pulp have a major effect on AC, as reported for other fruits and vegetables. The relatively high AC found in pawpaw pulp may motivate more health-conscientious people to consume pawpaw fruit. The diversity in PC and AC between pawpaw cultivars emphasizes the need for additional screening to identify cultivars with high AC and health-promoting potential.

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