Determination of Sugarcane Maturity and Optimal Harvest Time via UV-Vis Spectrophotometry and Digital Refractometry

Abstract

Accurate determination of sugarcane maturity is critical for maximizing sucrose yield and optimizing harvest efficiency; however, field-level assessment in smallholder systems remains largely subjective. This study determined the optimal harvest time for sugarcane (Saccharum officinarum L.) cultivated in Medellin, Cebu, Philippines, using systematic UV-Vis spectrophotometry and digital refractometry across five maturity stages (9-13 months after planting). Juice samples were extracted from three stalk positions (bottom, center, top) of ten randomly selected stalks per stage (n = 150 total). Total soluble solids (°Brix) and UV-Vis absorbance were measured, and data were analyzed using one-way and two-way ANOVA, Tukey’s HSD, Pearson correlation, linear discriminant analysis (LDA), and principal component analysis (PCA). The 12-month stage yielded the highest overall mean TSS (19.05 °Bx), the peak UV-Vis absorbance within the optimal range (1.1899 at 600 nm), and the lowest inter-sample variability (SD = 0.076). UV-Vis absorbance values were measured at stage-specific wavelengths (510–620 nm) as an exploratory chromophoric profiling approach; between-stage absorbance values are therefore not directly comparable on a single Beer–Lambert scale and should be interpreted as qualitative maturity indicators only. LDA correctly classified 83.33% of samples (Wilks’ λ, p < 0.05), and PCA confirmed the complementarity of the two methods. Twelve months after planting is recommended as the optimal harvest time, with a practical window of 11 to 12 months. Digital refractometry (≥18 °Bx at the bottom section) and UV-Vis spectrophotometry (absorbance 1.10–1.20 at 600 nm) together provide an accessible, scientifically validated decision-support framework for sugarcane harvest management in the Philippine context.