Composition Retention Metrics Reveal Route-Specific Controls of Glucose Release from Pretreated Kenaf Core

) that captures enrichment/depletion in the recovered solid and an absolute retention index (AR) that incorporates solid recovery to quantify true feedstock-basis retention. Glucose release was evaluated using paired yield bases (recovered-solid and raw-feedstock) together with solid yield and cellulose conversion to decouple digestibility from composition-driven enrichment effects. Across routes, recovered-solid-basis glucose yield reached 38.8% (autohydrolysis) and 37.6% (dilute acid) at moderate solid yields, whereas alkaline pretreatment combined higher recovery (up to 72.4%) with moderate-to-high digestibility (13.6-37.6%). Raw-feedstock-basis glucose yield ranged from 1.20-23.30% (autohydrolysis), 1.30-19.70% (dilute acid), and 8.70-18.00% (alkaline), showing that mass loss can offset apparent gains in digestibility. Route-resolved LOESS trends and quadratic response surfaces identify hemicellulose depletion as the most consistent predictor of glucose release, while lignin enrichment is not transferable across chemistries; AR-based lignin retention becomes a graded separator primarily under alkaline conditions. The results support routine paired reporting of R/AR metrics with solid yield, yield basis, and cellulose conversion for defensible cross-route comparison.