How Many Acerola (Malpighia emarginata DC.) Fruit Are Required for Reliable Postharvest Quality Assessment?

Acerola (Malpighia emarginata DC.) is a tropical fruit known for its high vitamin C (ascorbic acid) content. This study aimed to determine the optimal sample size (OSS) required to reliably estimate postharvest quality traits in acerola. A total of 50 red-ripe fruit from four cultivars (BRS Rubra, Cabocla, Costa Rica, and Junko) were evaluated individually for their physical (weight, diameter, length, color, and firmness) and chemical (soluble solids content [SSC], titratable acidity [TA], SSC/TA ratio, and vitamin C) attributes. Bootstrap resampling and nonlinear power models were used to model the relationships between sample sizes and the width of 95% confidence intervals (CI95%). Three methods were applied to determine the maximum curvature point (MCP): general, perpendicular distance (PD), and linear response plateau (LRP). The PD and LRP methods led to consistent and conservative OSS estimates, which ranged from 12 to 28 fruit depending on the trait and cultivar. A sample size of 20 fruit was identified as a practical and reliable reference. Chemical traits showed greater variability and required larger samples. Cultivar comparisons indicated that ‘BRS Rubra’, ‘Cabocla’, and ‘Costa Rica’ are suitable for fresh consumption, while ‘Junko’ is ideal for vitamin C extraction. These results provide statistical support for experimental planning in acerola postharvest research.