Ultrasonic degradation kinetics and isomerization of 3- and 4-O-caffeoylquinic acid at various pH: The protective effects of ascorbic acid and epigallocatechin gallate on their stability

Ultrasonic cavitation treatment of o-cresol wastewater and long-term pilot-scale study

Acoustic cavitation is a cutting-edge and eco-friendly advanced oxidation technology with significant efficacy in removing organic pollutants from water. Despite its potential, research on the degradation of o-cresol, a common and challenging phenolic pollutant, is limited. This study systematically investigates the optimal conditions for degrading o-cresol via acoustic cavitation and evaluates its application potential through extensive pilot tests. Batch test results indicate that ultrasonic cavitation effectively treats high concentrations of o-cresol (300 mg L-1), with aeration and neutral pH conditions enhancing removal efficiency, while the initial concentration has minimal impact on the removal rate. Additionally, analyses of total organic carbon (TOC), degradation products, and volatile organic compounds (VOCs) reveal that the main intermediates of o-cresol degradation through ultrasonic cavitation are substituted phenols and alkanes, with a mineralization rate reaching 60%. To assess the practical application of ultrasonic cavitation devices for o-cresol wastewater treatment, long-term pilot tests were conducted. These tests confirmed the device's effectiveness in removing o-cresol and its operational stability over 180 days. Furthermore, the study established the relationship between the o-cresol removal rate, hydraulic retention time (HRT), and operational cost. Consequently, this study demonstrates the feasibility of ultrasonic cavitation technology in treating high-concentration o-cresol wastewater and its potential for use in the pretreatment stage of biochemical treatment processes.

Treatment of high concentration phenol wastewater by low-frequency ultrasonic cavitation and long-term pilot scale study

Acoustic cavitation is an advanced, eco-friendly oxidation technology effective in removing organic pollutants from water. However, research on its use for degrading phenol, a common and challenging phenolic pollutant, is limited. This study explores the optimal conditions for phenol degradation using acoustic cavitation and assesses its practical application through extensive pilot tests. Results from batch tests show that low-frequency (15 kHz) ultrasonic cavitation effectively treats high concentrations of phenol (1000 mg L-1). Aeration and acidic pH enhance removal efficiency, while alkaline conditions inhibit degradation. Analysis of total organic carbon (TOC), degradation products, and volatile organic compounds (VOCs) reveals that the primary intermediates are substituted benzenes and alkanes. Long-term pilot tests demonstrated the device's effectiveness in phenol removal and its operational stability over 180 days. The study also establishes a relationship between removal efficiency, hydraulic retention time (HRT), and operating costs, highlighting the feasibility of low-frequency ultrasonic cavitation for treating high-concentration phenolic wastewater and its potential role in the pretreatment stage of biochemical processes.

New insights into ultrasound-assisted noncovalent nanocomplexes of β-lactoglobulin and neochlorogenic acid/cryptochlorogenic acid and its potential application for curcumin loading

The cross-linking sites and structure of protein-polyphenol complexes are susceptible to the type, structure, weight of polyphenols under nonthermal process. The low bioavailability and poor gastrointestinal instability of curcumin (CUR) hampers its application. Hence, changes in binding mechanism, structural and functional properties between β-lactoglobulin (β-LG) with two different configurations of chlorogenic acids (neochlorogenic acids (3-CQA) and cryptochlorogenic acids (4-CQA) by non-covalent binding under ultrasonic treatment, and the potential capacity for loading CUR were researched. The binding affinity scores of β-LG-4CQA was -7.1 kcal/mol. It is higher than β-LG-3CQA (-6.8 kcal/mol), which implied that the interaction between β-LG and 4-CQA was stronger. Circular dichroism calculations showed that the sonicated complex of the β-LG and 4-CQA with a decreased content of α-helices by 5.4 %, β-sheets by 4.6 %, and an increased content of irregular curls by 8.4 % (p < 0.05). The result demonstrated ultrasound and the binding of β-LG to 3/4-CQA improved the hydrophilicity, thermal stability, and antioxidant property of β-LG. Furthermore, the embedding rate of CUR in the ultrasound-assisted β-LG-4-CQA complex could reach 71.56 %. Consistent with the structural characterization results, the CUR release rate of ULG-4-CQA + CUR complex reached 17.36 % in simulated intestinal digestion, which was 8.09 % higher than free CUR. Indicating that after embedding with protein-polyphenol complexes, the stability and bioaccessibility of CUR was improved. This study reveals the potential application of ultrasound-assisted protein-polyphenol complexes for loading CUR.

Impact of thermal processing on dietary flavonoids

Flavonoids are a class of polyphenols which are widely distributed in natural products and foods. They have diverse bioactivities, including anti-inflammatory, anti-aging, and antioxidant activities. Generally, the foods rich in flavonoids are usually consumed after thermal processing. However, thermal stability of flavonoids is usually low, and thermal processing could cause either positive or negative influences on their stability and bioactivities. In this review, the effects of thermal processing on thermal stability and bioactivity of dietary flavonoids from different food sources are summarized. Then, strategies to improve thermal stability of dietary flavonoids are discussed and the effect of some promising thermal technologies are also preliminary clarified. The promising thermal technologies may be alternative to conventional thermal processing technologies.

Determination of Caffeoylquinic Acids Content by UHPLC in Scolymus hispanicus Extracts Obtained through Ultrasound-Assisted Extraction

Scolymus hispanicus L., also known as golden thistle, Spanish oyster thistle or, more commonly, as tagarnina is a plant that belongs to the Asteraceae family. It is collected from the wild for human consumption in Mediterranean countries. It is a relevant ingredient in Andalusian culinary culture, where the midribs of young plants are harvested for consumption. Scolymus hispanicus L. contains a wide variety of phenolic compounds such as caffeoylquinic acids (CQAs), among others. In the present work, the major phenolic compounds present in tagarnina have been identified, with 5-caffeoylquinic acid (5-CQA) and 3,5-dicaffeoylquinic acid (3,5-diCQA) being the main ones. A method based on ultrasound-assisted extraction (UAE) has been developed for the extraction of these compounds, with the percentage of methanol, sample-to-solvent ratio and the pH being the most influential factors. The developed method has been validated and employed to determine the concentration of 5-CQA and 3,5-diCQA in the midribs of Scolymus hispanicus, collected in six different places in the south of Spain. The antioxidant activity of the samples has also been determined, and a direct correlation with their caffeoylquinic compounds content has been established, showing an antioxidant effect.

Degradation, isomerization and stabilization of three dicaffeoylquinic acids under ultrasonic treatment at different pH

Dicaffeoylquinic acids (diCQAs) are found in a variety of edible and medicinal plants with various biological activities. An important issue is the low stability of diCQAs during extraction and food processing, resulting in the degradation and transformation. This work used 3,5-diCQA as a representative to study the influence of different parameters in ultrasonic treatment on the stability of diCQAs, including solvent, temperature, treatment time, ultrasonic power, duty cycle, and probe immersion depth. The generation of free radicals and its influence were investigated during the treatment. The stability of three diCQAs (3,5-diCQA, 4,5-diCQA and 3,4-diCQA) under the certain ultrasonic condition at different pH conditions was evaluated and found to decrease with the increase of pH, further weakened by ultrasonic treatment. Ultrasound was found to accelerate the degradation and isomerization of diCQAs. Different diCQAs showed different pattern of degradation and isomerization. The stability of diCQAs could be improved by adding epigallocatechin gallate and vitamin C.

Extraction, Isolation, and Purification of Value-Added Chemicals from Lignocellulosic Biomass

This review covers the operating conditions for extracting top value-added chemicals, such as levulinic acid, lactic acid, succinic acid, vanillic acid, 3-hydroxypropionic acid, xylitol, 2,5-furandicarboxylic acid, 5-hydroxymethyl furfural, chitosan, 2,3-butanediol, and xylo-oligosaccharides, from common lignocellulosic biomass. Operating principles of novel extraction methods, beyond pretreatments, such as Soxhlet extraction, ultrasound-assisted extraction, and enzymatic extraction, are also presented and reviewed. Post extraction, high-value biochemicals need to be isolated, which is achieved through a combination of one or more isolation and purification steps. The operating principles, as well as a review of isolation methods, such as membrane filtration and liquid–liquid extraction and purification using preparative chromatography, are also discussed.

Ultrasound-assisted assembly of β-lactoglobulin and chlorogenic acid for non covalent nanocomplex: fabrication, characterization and potential biological function

It is essential to understand the ultrasound-induced changes in assembly of proteins and polyphenols into non covalent nanocomplex. β-Lactoglobulin (LG) and chlorogenic acid (CA) with various biological activities can be combined to form food-grade nanocomplexes. This study systematically explored the role of high-intensity ultrasound pretreatment on the binding mechanisms of LG and CA, and the potential biological function for embedding curcumin (Cur). The scanning electron microscopy (SEM) revealed that ultrasound treatment could destroy the structure of LG, and the particle size of the protein was reduced to<50 nm. The change in secondary structure of the protein by ultrasound treatment could be revealed by the fourier transform infrared (FTIR) and fluorescence spectra. Besides, it was found that LG and CA were combined to form a complex under the hydrophobic interaction, and CA was bound in the internal cavity of LG with a relatively extended conformation. The result demonstrated that the ratio of Cur embedded in the ultrasonic sample could be effectively increased by 7% - 10%, the particle size in the emulsion was smaller, and the dispersion was more stable. This work contributes to the development of protein-polyphenol functional emulsion systems with the ability to deliver Cur.