Efficient valorization of date fruit processing by-product through nano- and green-extraction technology: a response surface methodology-based optimization study

In this study, the synthesis of date seed nanoparticles (SNPs) was investigated using the acid hydrolysis method. Afterwards, the potential extraction of phenolics from the synthetized SNP using microwave was studied using water and methanol as recovery solvents. To accomplish this, the experiments were operated at different conditions following the response surface methodology (RSM). For the synthesis of SNPs, HCl concentration (38%), hydrolysis time (4 days), microwave power (0.5 kW), methanol concentration (80%), and solid/water ratio of 40/1 (w/v) were the main independent factors promoting particle size reduction and maintaining maximum TPC and bioactivities. UHPLC profiling of SNP extracts allowed the identification of 8 phenolic compounds in the methanol-based MAE samples, while only 6 compounds were detected in the water-based MAE extracts. The major phenolic constituents detected in the SNPs were 3,4-dihydroxy benzoic acid, ferulic acid, and p-coumaric acid. Herein, a successful and suitable approach for date seed waste valorization was proposed through SNPs synthesis with enhanced TPC, TFC, and antioxidant activities, being noteworthy to be used in food applications. Graphical abstract: [Figure not available: see fulltext.].