Sequential physicochemical extraction of high hexose-pentose syrups from pineapple processing residues

Pineapple is one of the most popular tropical fruits, enjoyed globally due to its numerous nutritional benefits and unique flavour. However, fruit processing generates substantial underutilized biowaste, highlighting the need for innovative valorization of this waste-stream to produce useful bio-based products. This supports Sustainable Development Goal (SDG) 12 that focuses on Responsible Production and a circular bioeconomy. This study investigated the sequential recovery of soluble and insoluble sugars from Pineapple Processing Residues (PPR) to formulate hexose–pentose syrups as an alternative approach to residue valorization. The recovery process utilised an integrated approach of solid–liquid extraction and chemical catalysts to efficiently hydrolyse complex biomass into fermentable sugars. The study established that all syrup yields from the various PPRs were within the ranges of 11–15% and with high concentrations of glucose (22–55 g/100 g syrup) and fructose (23–49 g/100 g syrup) and no significant variation in their monomeric sugar compositions. A further optimization study revealed that all PPR types can be hydrolysed under the same optimal conditions of 50 min reaction time, 120 °C temperature, and 0.3 M acid concentration. Among the PPRs, the core of the smooth cayenne cultivar (SCC) was identified as the most viable for soluble sugar yield (64.2 g/100 g DM) and insoluble sugar yield (17.74 g/100 g DM). Overall, the analysis revealed that all four PPRs were viable for producing high hexose-pentose syrups.