Pineapple peel waste was utilized as an unexplored source of hemicellulose (31.8 ± 1.9%) for value addition. Hemicellulose was extracted by an alkali-based method, where the peels were incubated at different alkali concentrations (5%, 10% and 15% w/v) at temperatures ranging from 35 °C to a maximum of 65 °C for a fixed period of 16 h. A maximum recovery of hemicellulose (95.9 ± 2.0%) was observed after incubating extractive-free pineapple peels in 15% (w/v) alkali solution for 16 h at 45 °C. Higher incubation temperatures (65 °C) for 16 h, resulted in a lower yield of hemicellulose (81.7 ± 3.7%) which can be attributed to the disintegration of the hemicellulose structure due to large severity factor (temperature–time combination). With low severity factor, it was noted that higher yields (96.6 ± 0.3%) were obtained 65 °C, 4 h). Hydrothermal-assisted alkali extraction was also evaluated for maximizing the recovery of pineapple peel hemicellulose. The maximum relative recovery of ˜87.6% was obtained with 10% (w/v) alkali at the end of 1.5 h of hydrothermal pretreatment (121 °C and 15 psi pressure). The hemicellulose extracted by hydrothermal-assisted alkali pretreatment was enzymatically hydrolyzed to produce XOS and the process was optimized in terms of enzyme dose (U), temperature (°C), pH and time (h). Direct hydrolysis of pineapple peels with dilute nitric acid produced xylose-rich liquor (˜91% xylose yield) at 0.5% nitric acid, reaction time of 1 h and solid–liquid ratio of 1:20. The xylose-rich liquor could be converted to potential chemicals such as xylitol.
- Pineapple peels