Fractionation of red wine grape pomace by subcritical water extraction/hydrolysis

Antioxidant and antimicrobial extracts from grape stalks obtained with subcritical water. Potential use in active food packaging development

In order to valorise winemaking grape stalks, subcritical water extraction at 160 and 180 °C has been carried out to obtain phenolic-rich extracts useful for developing active food packaging materials. Red (R) and white (W) varieties (from Requena, Spain) were used, and thus, four kinds of extracts were obtained. These were characterised as to their composition, thermal stability and antioxidant and antibacterial activity. The extracts were incorporated at 6 wt% into polylactic acid (PLA) films and their effect on the optical and barrier properties of the films and their protective effect against sunflower oil oxidation was analysed. Carbohydrates were the major compounds (25-38%) in the extracts that contained 3.5-6.6% of phenolic compounds, the R extracts being the richest, with higher radical scavenging capacity. Every extract exhibited antibacterial effect against Escherichia coli and Listeria innocua, while PLA films with extracts preserved sunflower oil against oxidation.

Fruit pomace as a promising source to obtain biocompounds with antibacterial activity

The demand for natural compounds to replace synthetic additives has aroused the interest of different sectors of society, especially the scientific community, due to their safety, biocompatibility, biodegradability and low toxicity. Alternative sources for antimicrobial compounds have been explored, such as fruit pomace. These by-products have essential compounds in their composition with different potential for application in food and packaging. In this context, this review systematizes the use of pomace from different fruits as a source of antibacterial compounds. Also, it summarizes the extraction methods and the applications of these compounds. Grape pomace, cranberry, and apple extracts are the most explored for antibacterial control, especially against genus Listeria, Salmonella, Staphylococcus, and Escherichia. In addition, phenolic acids, anthocyanins, flavonoids, and proanthocyanins are the main compounds identified in the studied fruit pomace extracts. In the reviewed articles, the biocompounds recovery is performed by methods with the absence of high temperatures (>80 °C); in some studies, the solid-liquid extraction method at mild temperatures (<30 °C) was well explored, using ethanol and water as solvent. The use of fruit processing by-products for bacterial control highlights the possibility of favoring the three pillars of sustainability (social, economic, and environmental) in the food industry.

Current Challenges in the Sustainable Valorisation of Agri-Food Wastes: A Review

In the upcoming years, the world will face societal challenges arising, in particular, from the impact of climate change and the inefficient use of natural resources, in addition to an exponential growth of the world population, which according to the United Nations (UN) estimations will be 9.8 billion in 2050. This increasing trend requires optimized management of natural resources with the use of value-added waste and a significant reduction in food loss and food waste. Moreover, the recent pandemic situation, COVID-19, has contributed indisputably. Along with the agri-food supply chain, several amounts of waste or by-products are generated. In most cases, these biomass wastes cause serious environmental concerns and high costs to enterprises. The valorisation of the agri-food loss and food industry wastes emerged as a useful strategy to produce certain value-added compounds with several potential applications, namely in the food, health, pharmaceutical, cosmetic, and environmental fields. Therefore, in this review, some of the crucial sustainable challenges with impacts on the valorisation of agri-food loss/wastes and by-products are discussed and identified, in addition to several opportunities, trends and innovations. Potential applications and usages of the most important compounds found in food loss/waste will be highlighted, with a focus on the food industry, pharmaceutical industry, and the environment.

Potential Use of Grape Stems and Pomaces from Two Red Grapevine Cultivars as Source of Oligosaccharides

Grape pomace (grape skin and seeds) and stems are major by-products of winemaking, of lignocellulosic nature. The aim of this study was to value grape pomace and stems to produce prebiotic oligosaccharides (OS). Grapes from Touriga Nacional and Marselan cultivars (Vitis vinifera L.) were used for conventional red winemaking. The total of extractives, obtained by sequential extraction with dichloromethane, ethanol, and water, was approx. 64.0% (d.w.) for both pomaces, and 46.2% and 59.5% for Marselan and Touriga Nacional stems, respectively. Lignin contents in Marselan stems (26.4%) and pomace (20.4%) were higher than in Touriga Nacional pomace (19.3%) or stems (17.3%). Polysaccharides (hemicelluloses and cellulose) represented 9 and 8.2% of Marselan and Touriga pomaces, and 22.3 and 18.7% of respective stems. After extractives removal, the pomaces and stems were submitted to a hydrothermal treatment (autohydrolysis) to release oligosaccharides from the hemicellulose fraction. Autohydrolysis was carried out following a central composite rotatable design (CCRD) as a function of temperature (142–198 °C) and time (48–132 min). For all materials of both varieties, the production of sugars by autohydrolysis could be described by second-order models. Highest sugar productions were: 81.2 g/kg (d.w.) extracted Marselan pomace; 76.3 g/kg (d.w.) extracted Touriga Nacional pomace; 116.3 g/kg (d.w.) extracted Marselan stems; and 168.4 g/kg (d.w.) extracted Touriga Nacional stems. Yields of 99% OS were obtained by autohydrolysis at 170 °C/90 min.

Subcritical water extraction of bioactive phenolic compounds from distillery stillage

Distilleries generate huge amounts of by-products that have a negative impact on the environment, so the management of wastes generated by this sector should be improved. Because distillery by-products are a source of bioactive compounds, the recovery of these compounds not only reduces issues with environmental protection but also provides the basis for a waste-to-profit solution. Following the latest trends in the search for so-called green extraction techniques for recovering valuable products, this study investigated the effect of subcritical water extraction (SWE) conditions (temperature (25-260 °C), time (5-90 min), and solid-to-solvent ratio (1:5-1:50, w:v)) on the efficiency of recovery of bioactive compounds, i.e., polyphenols from distillery stillage, and on the antioxidant activity of the extracts. The highest extraction yield was obtained with 30-min SWE with a solid-to-solvent ratio of 1:15 at either 140 °C (for total polyphenol content and phenolic acid content) or 200 °C (for total flavonoid content), as indicated by the Response Surface Methodology analysis. Phenolic acids in the extracts were present mainly in free forms (up to 88% of the total content). The antioxidant activity, which was measured using several assays, correlated positively with the content of phenolic acids, which confirmed their significant contribution to the bioactive properties of the extracts. The antioxidant effects of the extracts were mostly due to hydroxycinnamic acids (especially ferulic and p-coumaric acids). Principal component analysis showed that the temperature and time of SWE were the factors that can explain the greatest amount of variation in the extraction yield, composition, and bioactive properties of the polyphenols. These results will influence the design of further processes, such as purification and concentration, which are necessary before using the extracted compounds as substrates that are applicable in various industries. Based on the analysis of the elemental composition, the biomass remaining after SWE was evaluated to consider the possibilities of its further utilization.

Subcritical Water as a Pre-treatment of Mixed Microbial Biomass for the Extraction of Polyhydroxyalkanoates

Polyhydroxyalkanoate (PHA) recovery from microbial cells relies on either solvent extraction (usually using halogenated solvents) and/or digestion of the non-PHA cell mass (NPCM) by the action of chemicals (e.g., hypochlorite) that raise environmental and health hazards. A greener alternative for PHA recovery, subcritical water (SBW), was evaluated as a method for the dissolution of the NPCM of a mixed microbial culture (MMC) biomass. A temperature of 150 °C was found as a compromise to reach NPCM solubilization while mostly preventing the degradation of the biopolymer during the procedure. Such conditions yielded a polymer with a purity of 77%. PHA purity was further improved by combining the SBW treatment with hypochlorite digestion, in which a significantly lower hypochlorite concentration (0.1%, v/v) was sufficient to achieve an overall polymer purity of 80%. During the procedure, the biopolymer suffered some depolymerization, as evidenced by the lower molecular weight (M_w) and higher polydispersity of the extracted samples. Although such changes in the biopolymer’s molecular mass distribution impact its mechanical properties, impairing its utilization in most conventional plastic uses, the obtained PHA can find use in several applications, for example as additives or for the preparation of graft or block co-polymers, in which low-M_w oligomers are sought.

White wine grape pomace as a suitable carbon source for lipid and carotenoid production by fructophilic Rhodorotula babjevae

AIM

We aim to explore the non-structural sugars from white wine grape pomace (WWGP) as the input carbon source for the co-production of multiple high-value products by the non-fastidious yeast Rhodotorula babjevae to create a sustainable and economically appealing process.

METHODS AND RESULTS

Water extraction of unfermented, soluble sugars from WWGP yielded extracts with similar amounts of glucose and fructose, which were used to prepare a growth medium. R. babjevae multiplied as fast on WWGP-based medium as on a reference medium but achieved higher cell dry weight (CDW) and lower intracellular triacylglycerol accumulation (22.5% vs 28.6%) in WWGP-based medium. In addition, R. babjevae produced mannitol and arabitol, carotenoids, and secreted polyol esters of fatty acids (PEFA), a rare type of glycolipid as confirmed by FTIR, NMR and HPLC analyses. Remarkably, R. babjevae consumed simultaneously both fructose and glucose when on WWGP-based medium and left glucose practically untouched in the reference medium, evidencing a fructophilic character.

CONCLUSIONS

R. babjevae, a metabolic versatile yeast, proliferated on a minimally processed extract and successfully converted glucose and fructose into high-value products.

SIGNIFICANCE AND IMPACT OF STUDY

Different chemicals with market potential can be produced through the valorization of abundant waste feedstocks generated by the wine industry to which R. babjevae can contribute.

Bio-Wastes as Aggregates for Eco-Efficient Boards and Panels: Screening Tests of Physical Properties and Bio-Susceptibility

Screening tests were developed or adapted from RILEM recommendations, standards and past studies, and carried out to characterize some agro-industrial wastes and to assess their feasibility as aggregates for eco-efficient building composites. Spent coffee grounds, grape and olive press waste and hazelnut shells were used, as well as maritime pine chips as control material. Particle size distribution, loose bulk density, thermal conductivity and hygroscopicity properties were analysed. The selected bio-wastes did not show good thermal insulation properties if compared with some bio-wastes already studied and used for thermal insulation composites. Values of loose bulk density and thermal conductivity were between 325.6–550.5 kg/m3 and 0.078–0.107 W/(m·K); moisture buffering values higher than 2.0 g/(m2·%RH). Biological susceptibility to mould and termites were also tested, using not yet standardized methods. The low resistance to biological attack confirms one of the greatest drawbacks of using bio-wastes for building products. However, final products properties may be changed by adding other materials, pre-treatments of the wastes and the production process.

Bioactive pectic polysaccharides from bay tree pruning waste: Sequential subcritical water extraction and application in active food packaging

The potential isolation of bio-active polysaccharides from bay tree pruning waste was studied using sequential subcritical water extraction using different time-temperature combinations. The extracted polysaccharides were highly enriched in pectins while preserving their high molecular mass (10-100 kDa), presenting ideal properties for its application as additive in food packaging. Pectin-enriched chitosan films were prepared, improving the optical properties (≥95% UV-light barrier capacity), antioxidant capacity (˃95% radical scavenging activity) and water vapor permeability (≤14 g·Pa^-1·s^-1·m^-1·10^-7) in comparison with neat chitosan-based films. Furthermore, the antimicrobial activity of chitosan was maintained in the hybrid films. Addition of 10% of pectins improved mechanical properties, increasing the Young's modulus 12%, and the stress resistance in 51%. The application of pectin-rich fractions from bay tree pruning waste as an additive in active food packaging applications, with triple action as antioxidant, barrier, and antimicrobial has been demonstrated.

Bio Discarded from Waste to Resource

The modern linear agricultural production system allows the production of large quantities of food for an ever-growing population. However, it leads to large quantities of agricultural waste either being disposed of or treated for the purpose of reintroduction into the production chain with a new use. Various approaches in food waste management were explored to achieve social benefits and applications. The extraction of natural bioactive molecules (such as fibers and antioxidants) through innovative technologies represents a means of obtaining value-added products and an excellent measure to reduce the environmental impact. Cosmetic, pharmaceutical, and nutraceutical industries can use natural bioactive molecules as supplements and the food industry as feed and food additives. The bioactivities of phytochemicals contained in biowaste, their potential economic impact, and analytical procedures that allow their recovery are summarized in this study. Our results showed that although the recovery of bioactive molecules represents a sustainable means of achieving both waste reduction and resource utilization, further research is needed to optimize the valuable process for industrial-scale recovery.

Progress in the Valorization of Fruit and Vegetable Wastes: Active Packaging, Biocomposites, By-Products, and Innovative Technologies Used for Bioactive Compound Extraction

According to the Food Wastage Footprint and Climate Change Report, about 15% of all fruits and 25% of all vegetables are wasted at the base of the food production chain. The significant losses and wastes in the fresh and processing industries is becoming a serious environmental issue, mainly due to the microbial degradation impacts. There has been a recent surge in research and innovation related to food, packaging, and pharmaceutical applications to address these problems. The underutilized wastes (seed, skin, rind, and pomace) potentially present good sources of valuable bioactive compounds, including functional nutrients, amylopectin, phytochemicals, vitamins, enzymes, dietary fibers, and oils. Fruit and vegetable wastes (FVW) are rich in nutrients and extra nutritional compounds that contribute to the development of animal feed, bioactive ingredients, and ethanol production. In the development of active packaging films, pectin and other biopolymers are commonly used. In addition, the most recent research studies dealing with FVW have enhanced the physical, mechanical, antioxidant, and antimicrobial properties of packaging and biocomposite systems. Innovative technologies that can be used for sensitive bioactive compound extraction and fortification will be crucial in valorizing FVW completely; thus, this article aims to report the progress made in terms of the valorization of FVW and to emphasize the applications of FVW in active packaging and biocomposites, their by-products, and the innovative technologies (both thermal and non-thermal) that can be used for bioactive compounds extraction.

Thermal decomposition and oxidation of β-caryophyllene in black pepper during subcritical water extraction

Subcritical water extraction is an efficient technique for extracting components from various plants by changing the polarity of water. β-caryophyllene is a natural bicyclic sesquiterpene with the highest content found among black pepper essential oils. In this study, the efficiency of extraction and yield of β-caryophyllene from black pepper were investigated using a subcritical water extraction technique. The optimal conditions of β-caryophyllene (1.19 ± 0.38 mg/g), and caryophyllene oxide (0.82 ± 0.38 mg/g) were obtained from black pepper under extraction conditions of 170 °C/10 min, and 200 °C/15 min, respectively. As the extraction temperature was increased, β-caryophyllene oxidation proceeded and the extraction content of caryophyllene oxide increased. It is anticipated that both β-caryophyllene and caryophyllene oxide with high biological activity can be used to selectively extract compounds using subcritical water extraction, which will be helpful in industrial applications.

Highly Efficient Semi-Continuous Extraction and In-Line Purification of High β-O-4 Butanosolv Lignin

Innovative biomass fractionation is of major importance for economically competitive biorefineries. Lignin is currently severely underutilized due to the use of high severity fractionation methodologies that yield complex condensed lignin that limits high-value applicability. Mild lignin fractionation conditions can lead to lignin with a more regular C-O bonded structure that has increased potential for higher value applications. Nevertheless, such extraction methodologies typically suffer from inadequate lignin extraction efficiencies and yield. (Semi)-continuous flow extractions are a promising method to achieve improved extraction efficiency of such C-O linked lignin. Here we show that optimized organosolv extraction in a flow-through setup resulted in 93-96% delignification of 40 g walnut shells (40 wt% lignin content) by applying mild organosolv extraction conditions with a 2 g/min flowrate of a 9:1 n-butanol/water mixture with 0.18 M H2SO4 at 120°C in 2.5 h. 85 wt% of the lignin (corrected for alcohol incorporation, moisture content and carbohydrate impurities) was isolated as a powder with a high retention of the β-aryl ether (β-O-4) content of 63 linking motifs per 100 C9 units. Close examination of the isolated lignin showed that the main carbohydrate contamination in the recovered lignin was butyl-xyloside and other butoxylate carbohydrates. The work-up and purification procedure were investigated and improved by the implementation of a caustic soda treatment step and phase separation with a continuous integrated mixer/separator (CINC). This led to a combined 75 wt% yield of the lignin in 3 separate fractions with 3% carbohydrate impurities and a very high β-O-4 content of 67 linking motifs per 100 C9 units. Analysis of all the mass flows showed that 98% of the carbohydrate content was removed with the inline purification step, which is a significant improvement to the 88% carbohydrate removal for the traditional lignin precipitation work-up procedure. Overall we show a convenient method for inline extraction and purification to obtain high β-O-4 butanosolv lignin in excellent yields.

Recovery of Phenolic Compounds from Red Grape Pomace Extract through Nanofiltration Membranes

The winemaking process generates a large amount of residues such as vine shots, stalks, grape pomace, and wine lees, which were only recently considered for exploitation of their valuable compounds. The purpose of this work was to investigate the performance of nanofiltration for the recovery of phenolic compounds, with bioactive capacity like antioxidant, from red grape pomace extract. Four membranes were compared in this study-three cellulose acetate (CA series: lab-prepared by phase inversion) and one commercial (NF90). All membranes were characterized for their hydraulic permeability and rejection coefficients to reference solutes like saccharose, glucose, raffinose, polyethylene glycol, sodium chloride, and sodium sulfate. Permeation flowrates and rejection coefficients towards total phenolics content, antioxidant activity, proanthocyanidins, glucose and fructose were measured in the nanofiltration of grape pomace extract using selected operating conditions. Among the investigated membranes, the CA400-22 exhibited the highest permeate flux (50.58 L/m² h at 20 bar and 25 °C), low fouling index (of about 23%), the lowest rejection coefficients towards the reference solutes and the best performance in terms of separation between sugars and phenolic compounds. Indeed, the observed rejections for glucose and fructose were 19% and 12%, respectively. On the other hand, total phenolics content and proanthocyanidins were rejected for 73% and 92%, respectively.

Green processing and biotechnological potential of grape pomace: Current trends and opportunities for sustainable biorefinery

Grape pomace is a high quality biodegradable residue of the winery industry. It is comprised of grape seed, skin and stalks, and is blessed with substantial quantities of phenols, flavonoids and anthocyanins with high antioxidant potential. Currently, there is huge emphasis on the isolation of bioactive molecules of grape pomace using green technologies such as microwave, ultrasound, supercritical fluids, high voltage discharge, enzymatic methods and other hybrid techniques. The major applications of these bioactives are contemplatedas nutraceuticals and extension in shelf-life of perishable foodstuffs. Alternatively, the crude form of grape pomace residues can be used for the production of energy, biofertilizers, biochar, biopolymers, composites, feed for ruminants and also, mushroom cultivation through microbial processing. This review discusses value-addition to grape pomace through biotechnological interventions and green processing, providing state-of-art knowledge on current scenario and opportunities for sustainability.

Dietary Fiber from Underutilized Plant Resources—A Positive Approach for Valorization of Fruit and Vegetable Wastes

Agri-food industries generate enormous amounts of fruit and vegetable processing wastes, which opens up an important research area aimed towards minimizing and managing them efficiently to support zero wastes and/or circular economy concept. These wastes remain underutilized owing to a lack of appropriate processing technologies vital for their efficient valorization, especially for recovery of health beneficial bioactives like dietary fibers. Dietary fiber finds wide applications in food and pharmaceutical industries and holds high promise as a potential food additive and/or as a functional food ingredient to meet the techno-functional purposes important for developing health-promoting value-added products. Based on this, the present review has been designed to support ‘zero waste’ and ‘waste to wealth’ concepts. In addition, the focus revolves around providing updated information on various sustainability challenges incurred towards valorization of fruit and vegetable wastes for extraction of health promoting dietary fibers.