Extraction of phenolic compounds from Siah‐Sardasht grape skin using subcritical water and ultrasound pretreatment

Plant Extraction in Water: Towards Highly Efficient Industrial Applications

Since the beginning of this century, the world has experienced a growing need for enabling techniques and more environmentally friendly protocols that can facilitate more rational industrial production. Scientists are faced with the major challenges of global warming and safeguarding water and food quality. Organic solvents are still widely used and seem to be hard to replace, despite their enormous environmental and toxicological impact. The development of water-based strategies for the extraction of primary and secondary metabolites from plants on a laboratory scale is well documented, with several intensified processes being able to maximize the extraction power of water. Technologies, such as ultrasound, hydrodynamic cavitation, microwaves and pressurized reactors that achieve subcritical water conditions can dramatically increase extraction rates and yields. In addition, significant synergistic effects have been observed when using combined techniques. Due to the limited penetration depth of microwaves and ultrasonic waves, scaling up entails changes to reactor design. Nevertheless, the rich academic literature from laboratory-scale investigations may contribute to the engineering work involved in maximizing mass/energy transfer. In this article, we provide an overview of current and innovative techniques for solid-liquid extraction in water for industrial applications, where continuous and semi-continuous processes can meet the high demands for productivity, profitability and quality.

A comprehensive review on current and emerging technologies toward the valorization of bio-based wastes and by products from foods

Industries in the agro-food sector are the largest generators of waste in the world. Agro-food wastes and by products originate from the natural process of senescence, pretreatment, handling, and manufacturing processes of food and beverage products. Notably, most of the wastes are produced with the transformation of raw materials (such as fruits, vegetables, plants, tubers, cereals, and dairy products) into different processed foods (e.g., jams, sauces, and canned fruits/vegetables), dairy derivatives (e.g., cheese and yogurt), and alcoholic (e.g., wine and beer) and nonalcoholic beverages (e.g., juices and soft drinks). Current research is committed not only to the usage of agro-food wastes and by products as a potential source of high-value bioactive compounds (e.g., phenolic compounds, anthocyanins, and organic acids) but also to the implementation of emerging and innovative technologies that can compete with conventional extraction methods for the efficient extraction of such biomolecules from the residues. Herein, specific valorization technologies, such as membrane-based processes, microwave, ultrasound, pulsed electric-assisted extraction, supercritical/subcritical fluids, and pressurized liquids, have emerged as advanced techniques in extracting various added-value biomolecules, showing multiple advantages (improved extraction yields, reduced process time, and protection to the bioactive properties of the compounds). Hence, this comprehensive review aims to analyze the ongoing research on applying such techniques in valorization protocols. A last-five-year review, together with a featured analysis of the relevant findings in the field, is provided.

Integrated Green Process for the Extraction of Red Grape Pomace Antioxidant Polyphenols Using Ultrasound-Assisted Pretreatment and β-Cyclodextrin

Winemaking is a process that generates a large volume of solid waste biomass, which is currently under extensive investigation as a bioresource of precious polyphenolic compounds. These substances are retrieved from vinification side streams principally by deploying solid–liquid extraction methods. In this frame, the present investigation had as objective the development of an alternative, green extraction process for polyphenols, through integration of ultrasonication as a pretreatment stage, and subsequent extraction with aqueous β-cyclodextrin. Polyphenol recovery from red grape pomace (RGP) was shown to be significantly enhanced by ultrasonication pretreatment, and the use of β-cyclodextrin effectively boosted the aqueous extraction. Under optimized conditions, established by response surface methodology, the maximum yield in total polyphenols was 57.47 mg GAE g−1 dm, at 80 °C, requiring a barrier of 10.95 kJ mol−1. The extract produced was significantly enriched in catechin and quercetin, compared to the aqueous extract, exhibiting also increased antiradical activity. These findings highlighted the value of the process developed for targeted recovery of certain polyphenols and the preparation of task-specific extracts.

Effects of pretreatment and type of hydrolysis on the composition, antioxidant potential and HepG2 cytotoxicity of bound polyphenols from Tartary buckwheat (Fagopyrum tataricum L. Gaerth) hulls

This study investigated the effects of ultrasound assisted-subcritical water (U-SW), subcritical water (SW), ultrasound (U) and hot water (HW) pretreatments and acid hydrolysis (AH) and alkaline hydrolysis (AlkH) on the phenolic composition, antioxidant potential and cytotoxicity of Tartary buckwheat hull extracts. The Folin Ciocalteu assay and HPLC-MS were used to characterize and quantify phenolics of the extracts. The ABTS, FRAP and TEAC assays were used to measure antioxidant activity and the MTT assay was used to measure cytotoxicity of the extracts in HepG2 human liver cancer cells. Results showed that U-SW gave the best AH yield of phenolics (128.45), followed by SW (85.82) and U (64.70), compared to the control, HW (35.82 mgg^-1). The same trend was observed for phenols extracted using AlkH. U-SW had the highest antioxidant activity, followed by SW and U regardless of hydrolytic method used. Cytotoxicity followed a similar trend with U-SW and SW being the most cytotoxic to liver cancer cells, followed by U, with the least being HW. The findings suggested that plant materials such as Tartary buckwheat hulls can be pretreated with U-SW, SW and U prior to hydrolytic recovery of bound polyphenols. Also, AH was more efficient than AlkH for phenol extraction, and gave extracts with higher antioxidant activity and cytotoxicity in HepG2 liver carcinoma cells. This application allows for beneficial usage of agricultural biomass and help diversify income sources and products for industry.