Pressurized Liquid Extraction of Polyphenols and Anthocyanins from Saffron Processing Waste with Aqueous Organic Acid Solutions: Comparison with Stirred-Tank and Ultrasound-Assisted Techniques

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.

The Greening of Anthocyanins: Eco-Friendly Techniques for Their Recovery from Agri-Food By-Products

“…From our bibliographic survey, five studies exploited the PLE technique with green solvents to extract anthocyanins from different matrices, such as saffron [22], black bean [25], jabuticaba [27], and red grape [40,41,44]. All studies agreed that the pressure did not significantly affect the extraction yield, while the temperature was the most important variable since it influenced both the polarity and the solubility.…”

“…Water, either pure or mixed with other solvents, emerged as the solvent of choice for the green recovery of anthocyanins in several cases. For the valorization of saffron (Crocus sativus L.) by-products, four out of five studies used just water or acidified water [19,[21][22][23]. The only one that did not report the use of water applied cold pressing, which is actually a solvent-free technique [20].…”

“…Pappas et al [22] carried out a comparative evaluation of different innovative technologies for the extraction of total anthocyanins from freeze-dried saffron tepals using aqueous solutions of citric acid (CA) and lactic acid (LA) at different concentrations. The outcomes indicated that no specific pattern was detected concerning the acid type and acid concentration, and the best performance, in terms of anthocyanin extraction and antioxidant capacity, was obtained using a stirred-tank extraction with 1% (w/v) LA solution, yielding 3.25 g cyanidin-3-O-glucoside equivalents (CGE)/kg in the dry weight (DW) of tepals.…”

Production and Analytical Aspects of Natural Pigments to Enhance Alternative Meat Product Color

“…The concentration-dependent extraction (0.1, 0.2, and 0.3%) revealed that 0.3% concentrations of these acids resulted in a higher yield of anthocyanin; however, higher or lower concentrations than 0.3% resulted in lower yields [ 51 ]. Similarly, based on the current observations, Pappas, Athanasiadis, Palaiogiannis, Poulianiti, Bozinou, Lalas and Makris [ 34 ] conducted a proportional evaluation of diverse novel technologies for the extraction of total anthocyanins from freeze-dried saffron tepals using aqueous solutions of citric acid and the lactic acid at various concentrations. Contrastingly, these results showed that no specific configuration was observed for the type of acid or concentration.…”

“…The existing literature regarding the production, extraction and analytical aspects of natural pigments developed for PBM is very limited; however, some corresponding studies have been reported [ 13 , 22 , 29 , 32 , 33 , 34 ]. Therefore, researchers are taking a profound interest in utilizing natural pigments as replacements for their synthetic counterparts, particularly by developing sustainable extraction techniques for the efficient retrieval of bioactive compounds for use in PBM products and nutraceuticals.…”