Optimisation of polyphenol extraction for the valorisation of spent gin botanicals

An average of 0.21 kg spent gin botanicals (SGB) is generated for every 1 L of gin, making it the major by-product of gin distillation. The present circular economy dynamics and increased awareness on resource use presents an opportunity for valorisation of SGB. SGB was optimised for polyphenol extraction using a three-factor Box-Behnken Design in response surface methodology (RSM). This was used to both optimise and study how the extraction variables affected yields and values of polyphenol and antioxidant activity of SGB. The generated optimum conditions for polyphenol extraction from SGB were 50% (v/v) solvent concentration, 40 mL g⁻¹ solvent: sample ratio, and 65 °C temperature. There is demand for polyphenols and natural antioxidants for use in both food and pharmaceuticals, and SGB is a natural bioresource material. The results from this study have shown a possible valorisation route for SGB and its potential for polyphenol extraction. This will create a sustainable pathway for the management of SGB and provide agro allied industries with a sustainable source of polyphenol. It will also provide a basis for process optimisation during gin distillation and possibility for reuse of botanicals materials.