Modeling and kinetics study of conventional and assisted batch solvent extraction

Polyphenols from Red Vine Leaves Using Alternative Processing Techniques

The extraction kinetics of polyphenols, which are leached from red vine leaves, are studied and evaluated using a laboratory robot and nonconventional processing techniques such as ultrasonic (US)-, microwave (MW)-, and pulsed electric field (PEF)-assisted extraction processes. The robotic high-throughput screening reveals optimal extraction conditions at a pH value of 2.5, a temperature of 56 °C, and a solvent mixture of methanol:water:HCl of 50:49:1 v/v/v. Nonconventional processing techniques, such as MW- and US-assisted extraction, have the fastest kinetics and produce the highest polyphenol yield. The non-conventional techniques yield is 2.29 g/L (MW) resp. 2.47 g/L (US) for particles that range in size from 450 to 2000 µm and 2.20 g/L (MW) resp. 2.05 g/L (US) for particles that range from 2000 to 4000 µm. PEF has the lowest yield of polyphenols with 0.94 g/L (450–2000 µm), resp. 0.64 g/L (2000–4000 µm) in comparison to 1.82 g/L (2000 to 4000 µm) in a standard stirred vessel (50 °C). When undried red vine leaves (2000 to 4000 µm) are used the total phenol content is 1.44 g/L with PEF.

Solid-liquid extraction of daidzein and genistein from soybean: Kinetic modeling of influential factors

The extraction of daidzein and genistein from soybean has been studied and the kinetic modeling was established using four modeling equations. The goodness of fit was evaluated by statistical errors including the standard error of means (SEM), the adjusted correlation coefficient (R2), and chi-square (χ2). The best model was considered to be the So and Macdonald model and it could give the most adequate description of solid-liquid extraction of daidzein and genistein from soybean sample. The effect of process parameters on extraction yields of daidzein and genistein also has been investigated. The optimized extraction condition was at 333.2 K using 70% ethanol solvent at a solvent-to-solid ratio of 20 mL g-1 with an agitation speed of 300 rpm. The highest extraction yields of daidzein and genistein from soybean were 0.126 ± 0.006 and 0.184 ± 0.013 mg g-1, respectively. The activation energies for extraction kinetics of soybean were found to be 11.10 kJ mol-1 (washing step) and 13.96 kJ mol-1 (diffusion step) for daidzein, 10.47 kJ mol-1 (washing step) and 19.70 kJ mol-1 (diffusion step) for genistein, respectively.

Extraction of Antioxidant Phenolic Compounds from Brewer's Spent Grain: Optimization and Kinetics Modeling

The kinetics of polyphenol extraction from brewer's spent grain (BSG), using a batch system, ultrasound assistance, and microwave assistance and the evolution of antioxidant capacity of these extracts over time, were studied. The main parameters of extraction employed in the batch system were evaluated, and, by applying response surface analysis, the following optimal conditions were obtained: Liquid/solid ratio of 30:1 mL/g at 80 °C, using 72% (v/v) ethanol:water as the solvent system. Under these optimized conditions, ultrasound assistance demonstrated the highest extraction rate and equilibrium yield, as well as shortest extraction times, followed by microwave assistance. Among the mathematical models used, Patricelli's model proved the most suitable for describing the extraction kinetics for each method tested, and is therefore able to predict the response values and estimate the extraction rates and potential maximum yields in each case.

A new kinetic model of ultrasound-assisted pretreatment on rice protein

The aim of this study was to establish a new model to reflect the real ultrasound pretreatment process on rice protein (RP). In this study, ultrasound treatment affected the yield of soluble protein of RP significantly and also improved the enzymatic hydrolysis efficiently. However, the aggregation of soluble protein occurred when ultrasonic power density and temperature reached a high level. The traditional model cannot reflect the real pretreatment process on RP due to the aggregation of protein. In this paper, a modified kinetic model was thus established by introducing a parameter of aggregation coefficient based on the Fick's second law, suggesting the two coefficients were highly dependent on the ultrasonic power density and temperature. Besides, the results of scanning electron microscope (SEM) both the untreated and samples pretreated by ultrasound indicated that the enzymatic hydrolysis efficiency was influenced by changing the structure of RP. Thereto, ultrasound treatment at proper conditions can shorten the enzymolysis time of RP and improve the efficiency of hydrolysis.

Kinetic improvement of olive leaves' bioactive compounds extraction by using power ultrasound in a wide temperature range

In this study, the effect of temperature and ultrasonic application on extraction kinetics of polyphenols from dried olive leaf was investigated. Conventional (CVE) and ultrasonic-assisted extraction (UAE) were performed at 10, 20, 30, 50 and 70°C using water as solvent. Extracts were characterized by measuring the total phenolic content, the antioxidant capacity and the oleuropein content (HPLC-DAD/MS-MS). Moreover, Naik's model was used to mathematically describe the extraction kinetics. The experimental results showed that phenolic extraction was faster in UAE (ultrasonic-assisted extraction) than in CVE (conventional extraction), being extraction kinetics satisfactorily described using Naik model (include VAR>98%). Besides, the total phenolic content, the antioxidant capacity and the oleuropein content were significantly (p<0.05) improved by increasing the temperature in both CVE and UAE. Oleuropein content reached 6.57±0.18 being extracted approximately 88% in the first minute for UAE experiments.

Characteristics of Subcritical Water Extraction and Kinetics of Pentacyclic Triterpenoids from Dry Loquat (Eriobotrya japonica) Leaves

In this study, pentacyclic triterpenoids (PTTs) were extracted from loquat leaves by subcritical water extraction (SWE) technique in a dynamic mode. The results revealed that PTTs yield increased up to 5.38±0.12 mg/g with the increasing temperature at 180 °C for corosolic acid (CA) and up to 7.20±0.11 mg/g at 200 °C for ursolic acid (UA) within experimental times. The optimum flow rates to obtain concentrated CA and UA extracts were found to be 33.33 and 41.67 mL/min, respectively. Furthermore, extraction temperatures strongly influenced the extraction rate as demonstrated by the rate constant of each temperature tested. Moreover, the kinetic rate constant decreased as the function of temperature indicating the yield of both CA and UA were significantly influenced by subcritical temperatures and extraction times.

Extraction Kinetics of phytochemicals and antioxidant activity during black tea (Camellia sinensis L.) brewing

BACKGROUND

Tea is the most consumed beverage in the world which is second only to water. Tea contains a broad spectrum of active ingredients which are responsible for its health benefits. The composition of constituents extracted to the tea brew depends on the method of preparation for its consumption. The objective of this study was to investigate the extraction kinetics of phenolic compounds, gallic acid, caffeine and catechins and the variation of antioxidant activity with time after tea brew is made.

METHODS

CTC (Crush, Tear, Curl) tea manufactured in Sri Lanka was used in this study. Tea brew was prepared according to the traditional method by adding boiling water to tea leaves. The samples were collected at different time intervals. Total phenolic and flavonoid contents were determined using Folin ciocalteu and aluminium chloride methods respectively. Gallic acid, caffeine, epicatechin, epigallocatechin gallate were quantified by HPLC/UV method. Antioxidant activity was evaluated by DPPH radical scavenging and Ferric Reducing Antioxidant Power (FRAP) assays.

RESULTS

Gallic acid, caffeine and catechins were extracted within a very short period. The maximum extractable polyphenols and flavanoids were achieved at 6-8 min after the tea brew is prepared. Polyphenols, flavanoids and epigallocatechin gallate showed a significant correlation (p < 0.001) with the antioxidant activity of tea.

CONCLUSION

The optimum time needed to release tea constituents from CTC tea leaves is 2-8 min after tea is made.