Abstract
Fοllow up with our previous study on the extraction of saffron processing waste polyphenols using deep eutectic solvents, the objective of this examination was a comparative evaluation of pressurized liquid extraction (PLE), stirred-tank extraction (STE) and stirred-tank extraction with ultrasonication pretreatment (STE/UP) with respect to the recovery of pigments and antioxidant polyphenols from saffron processing waste. Aqueous solutions of citric and lactic acids at two different concentrations were used as green solvents. The extracts obtained under the specified conditions were analyzed for total pigment and total polyphenol yields as well as for their ferric-reducing power and antiradical activity. Furthermore, each produced extract was analyzed with liquid chromatography–mass spectrometry to profile its analytical polyphenolic composition. In all cases, PLE provided inferior results compared to the two other techniques, producing extracts with lower polyphenolic concentration and weaker antioxidant properties. On the other hand, no specific pattern was detected concerning the effect of ultrasonication, acid type and acid concentration. Hierarchical cluster analysis indicated that stirred-tank extraction with 1% (w/v) lactic acid and ultrasonication pretreatment might be the highest-performing combination, providing extracts with increased polyphenol and pigment concentration; however, it also enhanced antioxidant activity. It was also concluded that the significantly shorter extraction time when using PLE might be an important element in further optimizing the process, buttressing the use of this technique for the establishment of innovative and sustainable-by-design extraction methodologies.
Highlights
As the world’s population and industrial activity are rapidly expanding, resource depletion and environmental aggravation are challenges which need to be imminently addressed [1]
Follow up with a previous study of ours on the use of deep eutectic solvents, in this study, pressurized-liquid extraction was compared to conventional stirred-tank extraction and stirred-tank extraction integrated by ultrasonication pretreatment, in order to obtain evidence regarding their suitability for antioxidant polyphenol and pigment extraction from saffron processing wastes
The outcome of the investigation evidenced that stirred-tank extraction and stirred-tank extraction including ultrasonication pretreatment outperformed pressurized-liquid extraction under the conditions employed
Summary
As the world’s population and industrial activity are rapidly expanding, resource depletion and environmental aggravation are challenges which need to be imminently addressed [1]. The agricultural and food industries are responsible for a large share of waste and byproducts generated as a result of farming practices and the harvesting and processing of raw materials. These side-streams are rich in organic substances, and their uncontrolled dumping results in environmental pollution with detrimental consequences to the neighboring eco-systems and public health [2]. In the framework of the circular economy, the rational utilization of agri-food waste biomass within a biorefinery concept may contribute to a fully sustainable agri-food sector.
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