Pineapple peel waste valorization for extraction of bio-active compounds and protein: Microwave assisted method and Box Behnken design optimization

Pineapple peel waste (PPW) is obtained in huge quantities out of pineapple canning industries and it is found to be rich in bioactive compounds with antioxidant activity and an opulent source of bromelain protein having commercial importance. To fulfil the purpose, microwave assisted extraction was considered. Three parameters varied were solvent to substrate ratio, microwave power and extraction time. The independent variables were solvent to substrate ratio (10:1 mL/g to 20:1 mL/g), microwave power (300 W-600 W) and extraction time (40 min-50 min). Optimization was done with three factors and three level Box- Behnken Design (BBD). Each of the experiment has been analysed for Total phenolic content (TPC), Total flavonoid content (TFC), Total tannin content (TTC) as well as for protein content. The Folin- Ciocalteu method was utilized for analysing TPC, TTC and the colorimetric method (AlCl₃) was used for the analysis of TFC, protein content was analysed by lowry's method and antioxidant activity making use of 2,2-diphenyl-1-picrylhydrazyl (DPPH). The p values were less than 0.05 which showed all the four models were significant. The experimental values and the predicted values were harmonious for the optimum conditions. The optimum condition obtained out of BBD were solvent to substrate ratio of 20:1 mL/g, microwave power of 600 W and extraction time 40 min. Antioxidant activity for the extract was found out by DPPH assay under the optimized conditions was 75% along with proteolytic activity of bromelain as 1647.612 GDUg_concentrate^-1.