Kinetic modeling of ultrasound-assisted extraction of phenolic compounds from grape marc: Influence of acoustic energy density and temperature

Abstract

The effects of acoustic energy density (6.8-47.4 W/L) and temperature (20-50 °C) on the extraction yields of total phenolics and tartaric esters during ultrasound-assisted extraction from grape marc were investigated in this study. The ultrasound treatment was performed in a 25-kHz ultrasound bath system and the 50% aqueous ethanol was used as the solvent. The initial extraction rate and final extraction yield increased with the increase of acoustic energy density and temperature. The two site kinetic model was used to simulate the kinetics of extraction process and the diffusion model based on the Fick's second law was employed to determine the effective diffusion coefficient of phenolics in grape marc. Both models gave satisfactory quality of data fit. The diffusion process was divided into one fast stage and one slow stage and the diffusion coefficients in both stages were calculated. Within the current experimental range, the diffusion coefficients of total phenolics and tartaric esters for both diffusion stages increased with acoustic energy density. Meanwhile, the rise of temperature also resulted in the increase of diffusion coefficients of phenolics except the diffusion coefficient of total phenolics in the fast stage, the value of which being the highest at 40 °C. Moreover, an empirical equation was suggested to correlate the effective diffusion coefficient of phenolics in grape marc with acoustic energy density and temperature. In addition, the performance comparison of ultrasound-assisted extraction and convention methods demonstrates that ultrasound is an effective and promising technology to extract bioactive substances from grape marc.

Study of the Efficacy of Two Extraction Techniques from <i>Crithmum maritimum</i> and<i> Salicornia europaea</i>

“…However, it is noteworthy that with an extraction time of 30 min, their values decreased and then re-increased. In effect, Tao et al [26] found that in the first 10-20 min of extraction the dissolution of the soluble components on the surfaces of the matrix occurs and it is at this stage that up to 90% of the recovery of the total content of the phenolic compounds can be achieved, thus indicating a considerable rapid extraction rate. Probably, the exposure of an ultrasonic irradiation of 30 min caused negative effects like oxidation, degradation, and/or polymerization of the phenolic and flavonoid compounds [27,28,29].…”

Influence of microwave irradiation on kinetics and thermodynamics of extraction of flavonoids from Phyllanthus emblica

“…The change in flavonoid concentration in the solid phase with respect to time and radial position during MAE can be described using Fick's second law as follows (Tao et al, 2014a):…”

“…Also higher temperatures aid in desorption of the solutes from active sites within the plant matrix (Veggi et al, 2013). The solute transfer from the solid-to-liquid phase is affected by transport properties such as effective diffusion coefficient (Tao et al, 2014a). With the increase in temperature, the effective diffusion coefficient for MAE of flavonoids also increased (Table 6) due to higher thermal energy at elevated temperatures.…”

Optimisation of organic solvent-free polyphenol extraction from Hypericum triquetrifolium Turra using Box–Behnken experimental design and kinetics

“…Based on Fick's second law, the mathematical expression that links Y TP and the effective diffusion of the solute (polyphenols) can be described as follows [12]:…”

“…ð Þ Þ against t, it can be observed that in some instances, the points are scattered along two intersecting straight lines, one with a relatively steep slope and another one with a shallow slope [12,13]. As the first line corresponds to the fast stage of extraction (washing), which can be considered as the non-limiting stage, in this study the D e coefficients were calculated by determining the slope of the slow stage of diffusion process, which might be more indicative regarding the effect of the extraction medium.…”