Low-Transition Temperature Mixtures (LTTMs) Made of Bioorganic Molecules: Enhanced Extraction of Antioxidant Phenolics from Industrial Cereal Solid Wastes

Valorization of barley (Hordeum vulgare L.) brans from the sustainable perspective: A comprehensive review of bioactive compounds and health benefits with emphasis on their potential applications

Barley is an important source of sustainable diets for humans, while its brans is commonly disposed as wastes. The recycling of barley brans has become a key for facilitating the valorization of barley as a whole to achieve its sustainable development. This review summarized the value of barley brans as an excellent source of multiple functional components (phenolic compounds, β-glucan, and arabinoxylan), which conferred extensive health benefits to barley brans mainly including antioxidant, anti-obesity and lipid-lowering, anti-diabetic, and hepatoprotective properties. The utilization of barley brans reflected a great potential for sustainable development. Exploiting of food products and edible films containing barley brans or their bioactive compounds and non-food applications (preparation of bioactive substances, laccase enzymes, and biosorbents) have been attempted for supporting the zero-waste concept and circular economy. Considering their diverse applications, effective extraction techniques of bioactive compounds from barley brans and their safety are the priority of future research.

Freezing-Tolerant Supramolecular Adhesives from Tannic Acid-Based Low-Transition-Temperature Mixtures

Natural polyphenols like tannic acid (TA) have recently emerged as multifunctional building blocks for designing advanced materials. Herein, we show the benefits of having TA in a dynamic liquid state using low-transition-temperature mixtures (LTTMs) for developing freezing-tolerant glues. TA was combined with betaine or choline chloride to create LTTMs, which direct the self-assembly of guanosine into supramolecular viscoelastic materials with high adhesion. Molecular dynamics simulations showed that the structural properties of the material are linked to strong hydrogen bonding in TA-betaine and TA-choline chloride mixtures. Notably, long-term and repeatable adhesion was achieved even at -196 °C due to the binding ability of TA's catechol and gallol units and the mixtures' glass transition temperature. Additionally, the adhesives demonstrated injectability and low toxicity against fibroblasts in vitro. These traits reveal the potential of these systems as bioadhesives for tissue repair, opening new avenues for creating multifunctional soft materials with bioactive properties.

Intensification of Enzymatic Sorbityl Laurate Production in Dissolved and Neat Systems under Conventional and Microwave Heating

Glycolipids such as sugar alcohol esters have been demonstrated to be relevant for numerous applications across various domains of specialty. The use of organic solvents and, more recently, deep eutectic solvents (DESs) to mediate lipase-supported bioconversions is gaining potential for industrial application. However, many challenges and limitations remain such as extensive time of production and relatively low productivities among others, which must be solved to strengthen such a biocatalytic process in industry. In this context, this study focuses on the intensification of sorbityl laurate production, as a model biocatalyzed reaction using Novozym 435, investigating the relevance of temperature, heating method, and solvent system. By increasing the reaction temperature from 50 to 90 °C, the space-time yield and product yield were considerably enhanced for reactions in DES and the organic solvent 2M2B, irrespective of the heating method (conventional or microwave heating). However, positive effects in 2M2B were more pronounced with conventional heating as 98% conversion yield was reached within 90 min at 90 °C, equating thus to a nearly 4-fold increase in performance yielding 118.0 ± 3.6 g/(L·h) productivity. With DES, the overall yield and space-time yield were lower with both heating methods. However, microwave heating enabled a 2-fold increase in both performance parameters when the reaction temperature was increased from 50 to 90 °C. Compared to conventional heating, a 7-fold increase in space-time yield at 50 °C and a 16-fold increase at 90 °C were achieved in DES by microwave heating. Furthermore, microwave irradiation enabled the usage of a neat, solvent-free system, representing an initial proof of concept with productivities of up to 13.3 ± 2.3 g/(L·h).

Polyphenol Release from Wheat Bran Using Ethanol-Based Organosolv Treatment and Acid/Alkaline Catalysis: Process Modeling Based on Severity and Response Surface Optimization

Wheat bran (WB) is globally a major food industry waste, with a high prospect as a bioresource in the production of precious polyphenolic phytochemicals. In this framework, the current investigation had as objectives (i) to use ethanol organosolv treatment and study the effect of acid and alkali catalysts on releasing bound polyphenols, (ii) establish linear and quadratic models of polyphenol recovery based on severity and response surface, and (iii) examine the polyphenolic composition of the extracts generated. Using sulfuric acid and sodium hydroxide as the acid and the alkali catalyst, respectively, it was found that the correlation of combined severity factor with total polyphenol yield was significant in the acid catalysis, but a highly significant correlation in the alkali-catalyzed process was established with modified severity factor, which takes into consideration catalyst concentration, instead of pH. Optimization of the process with response surface confirmed that polyphenol release from WB was linked to treatment time, but also catalyst concentration. Under optimized conditions, the acid- and alkali-catalyzed processes afforded total polyphenol yields of 10.93 ± 0.62 and 19.76 ± 0.76 mg ferulic acid equivalents g^-1 dry mass, respectively. Examination of the polyphenolic composition revealed that the alkali-catalyzed process had a striking effect on releasing ferulic acid, but the acid catalysis was insufficient in this regard. The outcome concerning the antioxidant properties was contradictory with respect to the antiradical activity and ferric-reducing power of the extracts, a fact most probably attributed to extract constituents other than ferulic acid. The process modeling proposed herein may be valuable in assessing both process effectiveness and severity, with a perspective of establishing WB treatments that would provide maximum polyphenol recovery with minimum harshness and cost.

An Update Regarding the Bioactive Compound of Cereal By-Products: Health Benefits and Potential Applications

Cereal processing generates around 12.9% of all food waste globally. Wheat bran, wheat germ, rice bran, rice germ, corn germ, corn bran, barley bran, and brewery spent grain are just a few examples of wastes that may be exploited to recover bioactive compounds. As a result, a long-term strategy for developing novel food products and ingredients is encouraged. High-value compounds like proteins, essential amino acids, essential fatty acids, ferulic acid, and other phenols, tocopherols, or β-glucans are found in cereal by-products. This review aims to provide a critical and comprehensive overview of current knowledge regarding the bioactive compounds recovered from cereal by-products, emphasizing their functional values and potential human health benefits.

Cereal Waste Valorization through Conventional and Current Extraction Techniques-An Up-to-Date Overview

Nowadays, in the European Union more than 100 million tons of food are wasted, meanwhile, millions of people are starving. Food waste represents a serious and ever-growing issue which has gained researchers’ attention due to its economic, environmental, social, and ethical implications. The Sustainable Development Goal has as its main objective the reduction of food waste through several approaches such as the re-use of agro-industrial by-products and their exploitation through complete valorization of their bioactive compounds. The extraction of the bioactive compounds through conventional methods has been used for a long time, whilst the increasing demand and evolution for using more sustainable extraction techniques has led to the development of new, ecologically friendly, and high-efficiency technologies. Enzymatic and ultrasound-assisted extractions, microwave-assisted extraction, membrane fractionation, and pressure-based extraction techniques (supercritical fluid extraction, subcritical water extraction, and steam explosion) are the main debated green technologies in the present paper. This review aims to provide a critical and comprehensive overview of the well-known conventional extraction methods and the advanced novel treatments and extraction techniques applied to release the bioactive compounds from cereal waste and by-products.

Extraction of Polyphenols from Olive Leaves Employing Deep Eutectic Solvents: The Application of Chemometrics to a Quantitative Study on Antioxidant Compounds

The extraction of phenolic compounds from olive leaves was optimized using three glycerol-based deep eutectic solvents (DESs) with lysine, proline, and arginine. A three-level Box–Behnken design was used to examine the influence of the liquid/solid ratio, concentration of DESs, and extraction temperature on the yield of the extraction process. A second-order polynomial model was used for predicting the polyphenol extraction yield. The optimal predicted conditions were used for extractions and they provided the highest total phenol yields with the glycerol–lysine exhibiting the best performance. Quantification of tyrosol, hydroxytyrosol, oleuropein, luteolin-7-O-glucoside, and rutin in the extracts showed high content in tyrosol in all DESs, particularly with glycerol–lysine and relatively similar contents with other studies for the other phenolic compounds. Finally, a linear relationship between tyrosol content and the total phenolic content of the extracts was observed.

Recent advances in green solvents for lignocellulosic biomass pretreatment: Potential of choline chloride (ChCl) based solvents

Biomass wastes exhibit a great potential to be used as a source of non-depleting renewable energy and synthesis of value-added products. The key to the valorization of excess lignocellulosic biomass wastes in the world lies on the pretreatment process to recalcitrant barrier of the lignocellulosic material for the access to useful substrates. A wide range of pretreatment techniques are available and advances in this field is continuously happening, in search for cheap, effective, and environmentally friendly methods. This review starts with an introduction to conventional approaches and green solvents for pretreatment of lignocellulosic biomass. Subsequently, the mechanism of actions along with the advantages and disadvantages of pretreatment techniques were reviewed. The roles of choline chloride (ChCl) in green solvents and their potential applications were also comprehensively reviewed. The collection of ideas in this review serve as an insight for future works or interest on biomass-to-energy conversion using green solvents.

Phytomass Valorization by Deep Eutectic Solvents—Achievements, Perspectives, and Limitations

In recent years, a plethora of extraction processes have been performed by a novel class of green solvents known as deep eutectic solvents (DESs), possessing several environmental, operational, and economic advantages proven by experience when compared to organic solvents and ionic liquids. The present review provides an organized overview of the use of DESs as extraction agents for the recovery of valuable substances and compounds from the original plant biomass, waste from its processing, and waste from the production and consumption of plant-based food. For the sake of simplicity and speed of orientation, the data are, as far as possible, arranged in a table in alphabetical order of the extracted substances. However, in some cases, the isolation of several substances is described in one paper and they are, therefore, listed together. The table further contains a description of the extracted phytomass, DES composition, extraction conditions, and literature sources. With regard to extracted value-added substances, this review addresses their pharmacological, therapeutic, and nutritional aspects. The review also includes an evaluation of the possibilities and limitations of using DESs to obtain value-added substances from phytomass.

A Green Extraction Process for Polyphenols from Elderberry (Sambucus nigra) Flowers Using Deep Eutectic Solvent and Ultrasound-Assisted Pretreatment

Sambucus nigra flowers, known as elderberry flowers (EBF), are a plant tissue rich in polyphenolic phytochemicals with important bioactivities. However, there are few studies dealing with the production of polyphenol-containing EBF extracts. The objective of the investigation presented herein was the development of a high-performance green extraction methodology, to generate EBF extracts enriched in polyphenolic substances, using an efficient deep eutectic solvent, combined with ultrasonication pretreatment. The DES was composed of L-lactic acid (hydrogen bond donor—HBD) and glycine (hydrogen bond acceptor—HBA) and, after an initial screening to properly regulate HBD/HBA ratio, the extraction was optimized by deploying response surface methodology. Under the optimized conditions, which were DES/water (85% w/v), liquid-to-solid ratio 60 mL g⁻¹, and stirring speed 200 rounds per minute, the extraction yield in total polyphenols amounted to 121.24 ± 8.77 mg gallic acid equivalents per g dry matter. The integration of ultrasonication prior to the batch stirred-tank extraction boosted polyphenol recovery of up to 174.73 ± 2.62 mg gallic acid equivalents per g dry matter. Liquid chromatography–mass spectrometry analysis showed that the richest EBF extract obtained was dominated by rutin, a di-p-coumaroylquic acid and chlorogenic acid.

Saffron Processing Wastes as a Bioresource of High-Value Added Compounds: Development of a Green Extraction Process for Polyphenol Recovery Using a Natural Deep Eutectic Solvent

The current investigation was undertaken to examine saffron processing waste (SPW) as a bioresource, which could be valorized to produce extracts rich in antioxidant polyphenols, using a green, natural deep eutectic solvent (DES). Initially, there was an appraisal of the molar ratio of hydrogen bond donor/hydrogen bond acceptor in order to come up with the most efficient DES composed of L-lactic acid/glycine (5:1). The following step was the optimization of the extraction process using response surface methodology. The optimal conditions thus determined were a DES concentration of 55% (w/v), a liquid-to-solid ratio of 60 mL g⁻¹, and a stirring speed of 800 rounds per minute. Under these conditions, the extraction yield in total polyphenols achieved was 132.43 ± 10.63 mg gallic acid equivalents per g of dry mass. The temperature assay performed within a range of 23 to 80 °C, suggested that extracts displayed maximum yield and antioxidant activity at 50–60 °C. Liquid chromatography-mass spectrometry analysis of the SPW extract obtained under optimal conditions showed that the predominant flavonol was kaempferol 3-O-sophoroside and the major anthocyanin delphinidin 3,5-di-O-glucoside. The results indicated that SPW extraction with the DES used is a green and efficient methodology and may afford extracts rich flavonols and anthocyanins, which are considered to be powerful antioxidants.

Polyphenol Extraction from Humulus lupulus (Hop) Using a Neoteric Glycerol/L-Alanine Deep Eutectic Solvent: Optimisation, Kinetics and the Effect of Ultrasound-Assisted Pretreatment

The investigation presented herein had as its scope the development of an integrated process for the efficient extraction of polyphenols from hop. For this purpose, a novel, natural deep eutectic solvent (DES) was synthesised, composed of glycerol and L-alanine, and the process was optimised by deploying a response surface methodology based on a Box–Behnken design. The variables considered were the DES/water proportion, the liquid-to-solid ratio and the stirring speed. Under the optimised conditions, the yield in total polyphenols achieved was 118.97 ± 8.27 mg gallic acid equivalents per g of dry mass. Ultrasonication, incorporated into the process as a pretreatment step, was shown to significantly change the kinetic pattern of polyphenol extraction and contributed to attaining higher yields only at 80 °C, whereas at lower temperatures a supressing effect was observed. Furthermore, increasing temperature was negatively correlated with the second-order extraction rates, evidencing a slow-down of the extraction rate at elevated temperatures.