Determination of the experimental unit size for postharvest quality trials in banana fruits (Musa sp., AAA group, Cavendish subgroup

Abstract

Introduction. In postharvest studies, physicochemical variables related to the quality of fresh produce are evaluated. However, there is no established optimal sample size that ensures efficient resource utilization and reliable results. Objective. To optimize the sample size for physicochemical postharvest evaluations in banana fruits. Materials and methods. Two experiments were conducted with evaluations performed on day 1, day 21, and day 28 (after ethylene exposure), using 100 fruits per evaluation. Soluble solids content, internal and external firmness, and external and internal color were assessed. A uniformity trial was established, where each fruit represented a basic experimental unit. An X–Y coordinate system was used to identify and locate each basic unit, which were arranged in 10 rows and 10 columns. Basic units were grouped to form secondary units, and the coefficient of variation was estimated for each grouping. The maximum curvature method was used to determine the optimal experimental unit size. A scatter plot was generated relating the coefficients of variation to experimental unit size, and a regression curve with its corresponding regression equation and coefficient of determination was obtained. Results. The point of maximum curvature, corresponding to the optimal experimental unit size, was estimated using the first derivative of the regression equation. The optimal experimental unit size for banana was determined to be 6 fruits, with an R² value of 74%, considering all evaluated variables and all postharvest quality assessment stages. Conclusion. The optimal sample size for postharvest quality evaluations (color, firmness, and soluble solids content) in banana fruit is 6 fruits.