A comparative study on sequential green hybrid techniques (ultrasonication, microwave and high shear homogenization) for the extraction of date seed bioactive compounds and its application as an additive for shelf-life extension of Oreochromis niloticus

Abstract

This study focuses on the extraction of bioactive compounds from date seeds using five polyol-based deep eutectic solvents (P-DESs) in combination with hybrid green extraction techniques, specifically microwave-assisted extraction (MAE), homogenization-assisted extraction (HAE), and ultrasound-assisted extraction (UAE). The optimization of these extraction techniques was achieved using P-DESs showing the highest efficiency for extracting date seed bioactive compounds using response surface methodology (RSM) and central composite design (CCD) approach. The optimized conditions from three green techniques were further applied in the form of hybrid green extraction techniques, involving six binary and three ternary methods, to assess the percentage increase in the extraction efficiency of date seed bioactive polyphenolics. Among the five P-DESs tested, choline chloride: ethylene glycol (ChCl:Eg) exhibited the highest extraction efficiency for recovering date seed phenolic compounds. Using ChCl:Eg as the P-DES, the highest extraction efficacy was found with MAE, followed by > HAE and > UAE. In addition, all hybrid extraction techniques showed higher extraction efficiencies than the single extraction methods. Notably, the binary hybrid techniques combining UAE and MAE (UMAE), HAE and MAE (HMAE) resulted in significantly higher recovery of bioactive compounds, with 52 % and 49 % increases in total phenolic content, respectively, compared to single extraction techniques. The lowest MIC and MBC of P-DES (ChCl:Eg) and date seed P-DES based extract recorded against all the tested bacterial strains was 40 % and 20 % respectively. Furthermore, the date seed extract from MAE was used to extend the shelf life of Oreochromis niloticus stored at 4 °C for 10 days. The results indicated that the date seed polyphenolic extract effectively inhibited microbial growth in Oreochromis niloticus during refrigerated storage, with the total bacterial count (TBC) of all the treated samples within the recommended acceptability limit of < 6 log CFU/g compared to the untreated samples, which showed a total bacterial count (TBC) > 6 log CFU/g. This study demonstrated that sequential hybrid techniques enhance and intensify the recovery of bioactive compounds more effectively than any single green technique.