Extractor dimensions affect optimization of laboratory-scale batch solid-liquid extraction of polyphenols from plant material: potato peels as a case study

Abstract

Polyphenols are commonly retrieved from plant material with solid-liquid extraction, the optimization of which requires fundamental laboratory-scale investigation, to clearly identify variables and variable levels crucial to the process. When performing scaling-up, the process result should be the anticipated one, irrespective of the scale adopted. However, the use of different equipment (extractor) might affect key parameters pertaining to extraction performance, providing diversified outcome for the same plant matrix extracted with a given solvent. To test this hypothesis, potato peels were chosen as a model plant matrix and extraction optimization was carried out using water/ethanol mixtures. All process variables (ethanol concentration, liquid-to-solid ratio, stirring speed) were maintained unchanged, except for extractor volume, which varied from 25 to 250 mL, and stirring bar length, which varied from 19 to 40 mm. The set of optimized values in each case was different, illustrating the effect of extractor dimensions on the extraction optimization. However, extraction yield in total polyphenols was essentially the same in cases examined. Kinetics also revealed that depending on the extractor volume and stirring bar length, extraction rate constant and diffusivity may be significantly impacted. Notable differences were also found in the major potato peel polyphenols, chlorogenic and caffeic acids, but these differences were not reflected on the antioxidant characteristics of the extracts, which were virtually unaffected. This study demonstrated for the first time that extractor dimensions affect significantly the settings of optimization of stirred-tank polyphenol extraction on a laboratory scale, leading to diversified conclusions. © 2020 Taylor & Francis Group, LLC.