Hydrogen-rich solvent method in phytochemical extraction: Potential mechanisms and perspectives.

INTRODUCTION: Phytochemicals are used in many products, including foods, beverages, pharmaceuticals, and cosmetics. The extraction of phytochemicals is considered one of the best solutions to valorize these underestimated materials. Many methods have been developed to efficiently extract phytochemicals at high quality, high purity, and low costs without harming the environment. Recently, molecular hydrogen (H2 ) has shown its ability to improve the extraction of phytochemicals from plant materials. Due to its unique physicochemical and biological properties, H2 showed an efficient ability to extract phenolics and antioxidants at high yields with cost-effective potential. Without sophisticated equipment and high energy and solvent consumption, the hydrogen extraction method is a green and applicable alternative for the extraction of phytochemicals. OBJECTIVES: This review aims to provide the latest knowledge and results concerning the studies on using hydrogen-rich solvents to extract phytochemicals from different agri-food wastes, by-products, and other plant materials. MATERIALS AND METHODS: Recent literature relating to extracting phytochemicals by the hydrogen-rich solvent method and its potential mechanisms is summarized to provide a basic understanding of how hydrogen can improve the extraction of phytochemicals. RESULTS: This review describes, for the first time, the practical procedure of how researchers and laboratories can apply the hydrogen extraction method under safe conditions at a low-budget scale. The review provides some examples of the hydrogen extraction method and the mechanisms and rationale behind its effectiveness. CONCLUSIONS: It can be concluded that the hydrogen-rich solvent method is a green and cost-effective method for extracting phytochemicals from different plant materials.

Selective separation of nutrients and volatile fatty acids from food wastes using electrodialysis and membrane contactor for resource valorization.

Transport and selectivity parameters describe the quantity and purity of nutrients and volatile fatty acids (VFAs) separated from fermentation media. However, the complexity of fermentation media and low nutrient concentrations hinder the optimal conditions of such parameters. Exploring technologies to overcome such limitations is crucial for selectively separating VFAs from nutrients in fermented media. The objectives of this study were to investigate the: (1) flux, (2) recovery, (3) concentration factor, and (4) specific energy consumption of nutrients (NH4+, K+, NO3-, and PO43-) and VFAs (acetic, propionic, and butyric acid) via electrodialysis (ED), and (5) selectively separate the VFAs from the nutrients in the ED concentrate using a hydrophobic membrane contactor (HMC). Synthetic feed and real industrial fermented food wastes were used for ED and HMC experiments. The ED consumed 0.395 kWh/kg, recovering 64-95% of the nutrients and VFAs, corresponding to 4.1-9.4 and 0.6-22.1 g/L nutrients and VFAs, respectively. The HMC selectively separated over 94% of VFAs after ED, with <2% nutrients contamination in the final VFA stream. The results suggest that applying HMC after ED can concentrate and selectively separate VFAs from nutrients in fermented food wastes, which can be valorized for bio-based fertilizers and chemical platforms.

Valorisation of Agri-Food Waste for Bioactive Compounds: Recent Trends and Future Sustainable Challenges.

Worldwide, a massive amount of agriculture and food waste is a major threat to the environment, the economy and public health. However, these wastes are important sources of phytochemicals (bioactive), such as polyphenols, carotenoids, carnitine, coenzymes, essential oils and tocopherols, which have antioxidant, antimicrobial and anticarcinogenic properties. Hence, it represents a promising opportunity for the food, agriculture, cosmetics, textiles, energy and pharmaceutical industries to develop cost effective strategies. The value of agri-food wastes has been extracted from various valuable bioactive compounds such as polyphenols, dietary fibre, proteins, lipids, vitamins, carotenoids, organic acids, essential oils and minerals, some of which are found in greater quantities in the discarded parts than in the parts accepted by the market used for different industrial sectors. The value of agri-food wastes and by-products could assure food security, maintain sustainability, efficiently reduce environmental pollution and provide an opportunity to earn additional income for industries. Furthermore, sustainable extraction methodologies like ultrasound-assisted extraction, pressurized liquid extraction, supercritical fluid extraction, microwave-assisted extraction, pulse electric field-assisted extraction, ultrasound microwave-assisted extraction and high hydrostatic pressure extraction are extensively used for the isolation, purification and recovery of various bioactive compounds from agri-food waste, according to a circular economy and sustainable approach. This review also includes some of the critical and sustainable challenges in the valorisation of agri-food wastes and explores innovative eco-friendly methods for extracting bioactive compounds from agri-food wastes, particularly for food applications. The highlights of this review are providing information on the valorisation techniques used for the extraction and recovery of different bioactive compounds from agricultural food wastes, innovative and promising approaches. Additionally, the potential use of these products presents an affordable alternative towards a circular economy and, consequently, sustainability. In this context, the encapsulation process considers the integral and sustainable use of agricultural food waste for bioactive compounds that enhance the properties and quality of functional food.

Review of osmotic dehydration: Promising technologies for enhancing products' attributes, opportunities, and challenges for the food industries.

Osmotic dehydration (OD) is an efficient preservation technology in that water is removed by immersing the food in a solution with a higher concentration of solutes. The application of OD in food processing offers more benefits than conventional drying technologies. Notably, OD can effectively remove a significant amount of water without a phase change, which reduces the energy demand associated with latent heat and high temperatures. A specific feature of OD is its ability to introduce solutes from the hypertonic solution into the food matrix, thereby influencing the attributes of the final product. This review comprehensively discusses the fundamental principles governing OD, emphasizing the role of chemical potential differences as the driving force behind the molecular diffusion occurring between the food and the osmotic solution. The kinetics of OD are described using mathematical models and the Biot number. The critical factors essential for optimizing OD efficiency are discussed, including product characteristics, osmotic solution properties, and process conditions. In addition, several promising technologies are introduced to enhance OD performance, such as coating, skin treatments, freeze-thawing, ultrasound, high hydrostatic pressure, centrifugation, and pulsed electric field. Reusing osmotic solutions to produce innovative products offers an opportunity to reduce food wastes. This review explores the prospects of valorizing food wastes from various food industries when formulating osmotic solutions for enhancing the quality and nutritional value of osmotically dehydrated foods while mitigating environmental impacts.

PHB production from food waste hydrolysates by Halomonas bluephagenesis Harboring PHB operon linked with an essential gene.

Food wastes can be hydrolyzed into soluble microbial substrates, contributing to sustainability. Halomonas spp.-based Next Generation Industrial Biotechnology (NGIB) allows open, unsterile fermentation, eliminating the need for sterilization to avoid the Maillard reaction that negatively affects cell growth. This is especially important for food waste hydrolysates, which have a high nutrient content but are unstable due to batch, sources, or storage conditions. These make them unsuitable for polyhydroxyalkanoate (PHA) production, which usually requires limitation on either nitrogen, phosphorous, or sulfur. In this study, H. bluephagenesis was constructed by overexpressing the PHA synthesis operon phaCABCn (cloned from Cupriavidus necator) controlled by the essential gene ompW (encoding outer membrane protein W) promoter and the constitutive porin promoter that are continuously expressed at high levels throughout the cell growth process, allowing poly(3-hydroxybutyrate) (PHB) production to proceed in nutrient-rich (also nitrogen-rich) food waste hydrolysates of various sources. The recombinant H. bluephagenesis termed WZY278 generated 22 g L-1 cell dry weight (CDW) containing 80 wt% PHB when cultured in food waste hydrolysates in shake flasks, and it was grown to 70 g L-1 CDW containing 80 wt% PHB in a 7-L bioreactor via fed-batch cultivation. Thus, unsterilizable food waste hydrolysates can become nutrient-rich substrates for PHB production by H. bluephagenesis able to be grown contamination-free under open conditions.

A review on the hydration properties of dietary fibers derived from food waste and their interactions with other ingredients: opportunities and challenges for their application in the food industry.

Dietary fiber (DF) significantly affects the quality attributes of food matrices. Depending on its chemical composition, molecular structure, and degree of hydration, the behavior of DF may differ. Numerous reports confirm that incorporating DF derived from food waste into food products has significant effects on textural, sensory, rheological, and antimicrobial properties. Additionally, the characteristics of DF, modification techniques (chemical, enzymatic, mechanical, thermal), and processing conditions (temperature, pH, ionic strength), as well as the presence of other components, can profoundly affect the functionalities of DF. This review aims to describe the interactions between DF and water, focusing on the effects of free water, freezing-bound water, and unfreezing-bound water on the hydration capacity of both soluble and insoluble DF. The review also explores how the structural, functional, and environmental properties of DF contribute to its hydration capacity. It becomes evident that the interactions between DF and water, and their effects on the rheological properties of food matrices, are complex and multifaceted subjects, offering both opportunities and challenges for further exploration. Utilizing DF extracted from food waste exhibits promise as a sustainable and viable strategy for the food industry to create nutritious and high-value-added products, while concurrently reducing reliance on primary virgin resources.

Recent Advances in Health Benefits of Bioactive Compounds from Food Wastes and By-Products: Biochemical Aspects.

Bioactive compounds, including terpenoids, polyphenols, alkaloids and other nitrogen-containing constituents, exert various beneficial effects arising from their antioxidant and anti-inflammatory properties. These compounds can be found in vegetables, fruits, grains, spices and their derived foods and beverages such as tea, olive oil, fruit juices, wine, chocolate and beer. Agricultural production and the food supply chain are major sources of food wastes, which can become resources, as they are rich in bioactive compounds. The aim of this review is to highlight recent articles demonstrating the numerous potential uses of products and by-products of the agro-food supply chain, which can have various applications.

Valorization of food wastes with a sequential two-step process for microbial ß-carotene production: A zero waste approach.

Here, two consecutive ß-carotene fermentation processes were carried out with Rhodotorula glutinis yeast in the growth media obtained from orange and grape wastes. Firstly, waste biomasses were subjected to hot water extraction. Effects of waste type, drying pretreatment, particle size and solid/liquid ratio on the total concentration and yield of sugars recovered were tested. The highest sugar concentration was obtained by the hot water extraction of fresh grape pomace as 61.2 g total reducing sugars (TRS)/L at a solid/liquid ratio of 100 g/L. In the first fermentation process, effect of solid/liquid ratio (initial TRS concentration) on ß-carotene production pattern of R. glutinis was investigated in the media obtained directly by hot water extraction of the wastes. Microorganism and ß-carotene concentrations increased with increasing solid/liquid ratio (range 10-100 g/L), and the microbial growth data fit the Monod model well for all cases. Maximum ß-carotene concentration in the growth medium obtained from hot water extraction of 100 g/L of grape pomace was determined as 5988.6 mg/L. In the second fermentation process, ß-carotene was produced in the acid hydrolysate of extraction residues. 10.1 g/L and 6.7 g/L of TRS was obtained after acid hydrolysis of orange and grape residues, respectively, and the highest ß-carotene concentration of 370.0 mg/L was found in the medium of hydrolyzed orange peel extraction residue. Total ß-carotene production increased to 1777.1 and 3279.6 mg/L (26% and 4.9% of increase) after the second fermentation step. 85.3% and 80.2% of reduction in orange and grape waste weights were observed at the end of the process, which was an indicator of efficient waste biomass disposal. Two sequential ß-carotene fermentation steps offered significant advantages in terms of both efficiency and a zero waste approach.

Low-carbon emitting university campus achieved via anaerobic digestion of canteen food wastes.

University campuses of China accommodate over 30 million students and consume a large amount of fossil fuel energy, leading to high carbon emission. Implementation of bioenergy (e.g. biomethane) is one of promising ways to mitigate emission and foster low-carbon emitting campus. Biomethane potential from anaerobic digestion (AD) of food waste (FW) in 2344 universities of 353 cities of mainland China have been estimated herein. Results have shown that 1.74 million tons of FW are discharged from campus canteens annually, that can generate 195.8 million m3 biomethane and reduce 0.77 million ton CO2-eq. Wuhan, Zhengzhou, and Guangzhou are the top three cities having the most biomethane potential from campus FW, accounting up to 8.92, 7.89, and 7.28 million m3 year-1, respectively. Technical challenges and solutions have been summarized and discussed such as FW purity, accumulation of ammonia and fatty acid, foaming, and plant site selection. Low-carbon campuses are supposed to be achieved by using bioenergy, like biomethane, in appropriate ways after resolving technical and management challenges.

Hornification: Lessons learned from the wood industry for attenuating this phenomenon in plant-based dietary fibers from food wastes.

A significant amount of waste is annually generated worldwide by the supply chain of the food industry. Considering the population growth, the environmental concerns, and the economic opportunities, waste recovery is a promising solution to produce valuable and innovative ingredients for food and nonfood industries. Indeed, plant-based wastes are rich in dietary fibers (DF), which have relevant technical functionalities such as water/oil holding capacity, swelling capacity, viscosity, texture, and physiological properties such as antioxidant activity, cholesterol, and glucose adsorption capacities. Different drying technologies could be applied to extend the shelf life of fresh DF. However, inappropriate drying technologies or process conditions could adversely affect the functionalities of DF via the hornification phenomenon. Hornification is related to the formation of irreversible hydrogen bindings, van der Waals interactions, and covalent lactone bridges between cellulose fibrils during drying. This review aims to capitalize on the knowledge developed in the wood industry to tackle the hornification phenomenon occurring in the food industry. The mechanisms and the parameters affecting hornification as well as the mitigation strategies used in the wood industry that could be successfully applied to foods are summarized. The application of conventional drying technologies such as air or spray-drying increased the occurrence of hornification. In contrast, solvent exchange, supercritical drying, freeze-drying, and spray-freeze-drying approaches were considered effective strategies to limit the consequences of this phenomenon. In addition, incorporating capping agents before drying attenuated the hornification. The knowledge summarized in this review can be used as a basis for process design in the valorization of plant-based wastes and the production of functional DF that present relevant features for the food and packaging industries.

Production of high-value oxidative enzymes by Cyathus bulleri on agricultural and agri-food wastes for application in the textile sector.

Ligninolytic and other oxidative enzymes have emerged as promising biocatalysts in several industries. Since their production at a low cost is necessary for any large-scale application, we demonstrate the use of rice bran (RB), an agricultural waste and agri-food wastes such as potato peelings (PP), banana peelings (BP), and green pea peelings (GPP) for their production. High activity of laccase (12 U/ml), manganese peroxidase (16.11 ± 1.43 U/ml), and aryl alcohol oxidase (1.25 U/ml) was obtained on the PP on the 12th day of growth and ~ 6 U/ml of lytic polysaccharide monooxygenase was obtained on the 14th day of growth demonstrating PP to be a good substrate for their production. RB served as the next best substrate for the production of these enzymes. While the GPP was effective for the production of laccase (9.2 U/ml), this and the BP were not good substrates for the production of other enzymes. Efficient (48-82%) decolorization of several azo-, triarylmethane- dyes, and real textile effluent, without the addition of any mediator, demonstrated the high oxidative ability of the crude culture filtrate produced on the PP (CF-PP), which was a significant improvement compared to the treatment given by the previously reported culture filtrate obtained on wheat bran (CF-WB). An extensive breakdown of Reactive Orange (RO) 16 was demonstrated using CF-PP resulting in the formation of a new product at m/z of 294.05 (6-acetamido-3,4-dioxo-3,4-dihydronapthalene-2-sulfonate), previously reported to be produced on ozonation/advanced oxidation of RO16. The predominant laccase and manganese peroxidase isoforms produced on the PP were also identified.

Yarrowia lipolytica as a biorefinery platform for effluents and solid wastes valorization - challenges and opportunities.

Due to its physiological and enzymatic features, Yarrowia lipolytica produces several valuable compounds from a wide range of substrates. Appointed by some authors as an industrial workhorse, Y. lipolytica has an extraordinary ability to use unrefined and complex low-cost substrates as carbon and nitrogen sources, aiding to reduce the waste surplus and to produce added-value compounds in a cost-effective way. Dozens of review papers regarding Y. lipolytica have been published till now, proving the interest that this yeast arouses in the scientific community. However, most of them are focused on metabolic pathways involved in substrates assimilation and product formation, or the development of synthetic biology tools in order to obtain engineered strains for biotechnological applications. This paper provides an exhaustive and up-to-date revision on the application of Y. lipolytica to valorize liquid effluents and solid wastes and its role in developing cleaner biotechnological approaches, aiming to boost the circular economy. Firstly, a general overview about Y. lipolytica is introduced, describing its intrinsic features and biotechnological applications. Then, an extensive survey of the literature regarding the assimilation of oily wastes (waste cooking oils, oil cakes and olive mill wastewaters), animal fat wastes, hydrocarbons-rich effluents, crude glycerol and agro-food wastes by Y. lipolytica strains will be discussed. This is the first article that brings together the environmental issue of all such residues and their valorization as feedstock for valuable compounds production by Y. lipolytica. Finally, it will demonstrate the potential of this non-conventional yeast to be used as a biorefinery platform.

Nanocellulose: a promising green treasure from food wastes to available food materials.

The synthesis of novel functional materials from abundant food waste resources has great application potentials and ecological benefits. Nanocellulose is a renewable and sustainable polymer that possesses a modifiable surface, excellent mechanical strength, and high aspect ratio, and it is nontoxic. These unique properties garner nanocellulose a promising prospect for multi-various applications including the food industry. This review presents the structural characteristics and advances in the extraction approaches of nanocellulose, with an emphasis in recent progress on the various applications of nanocellulose in the field of food industry. Finally, the environmental and human health issues related to the production of nanocellulose are evaluated. The scheme to extract and produce nanocellulose from food wastes provides a platform for the sustainable utilization of waste biomass. These nanocelluloses exhibit excellent performances in green food packaging materials, emulsion stabilizers, dietary fiber, nutrition delivery and food three-dimensional (3 D) printing hydrogels. To ensure the security and regulatory issues, validated standards to characterize the structure and evaluate its toxicity are still indispensable to achieve the commercialization of nanocellulose in the food industry.

Impact of Chitosan on the Mechanical Stability of Soils.

Chitosan is becoming increasingly applied in agriculture, mostly as a powder, however little is known about its effect on soil mechanical properties. Uniaxial compression test was performed for cylindrical soil aggregates prepared from four soils of various properties (very acidic Podzol, acidic Arenosol, neutral Fluvisol and alkaline Umbrisol) containing different proportions of two kinds of chitosan (CS1 of higher molecular mass and lower deacetylation degree, and CS2 of lower molecular mass and higher deacetylation degree), pretreated with 1 and 10 wetting-drying cycles. In most cases increasing chitosan rates successively decreased the mechanical stability of soils that was accompanied by a tendential increase in soil porosity. In one case (Fluvisol treated with CS2) the porosity decreased and mechanical stability increased with increasing chitosan dose. The behavior of acidic soils (Podzol and Arenosol) treated with CS2, differed from the other soils: after an initial decrease, the strength of aggregates increased with increasing chitosan amendment, despite the porosity consequently decreasing. After 10 wetting-drying cycles, the strength of the aggregates of acidic soils appeared to increase while it decreased for neutral and alkaline soils. Possible mechanisms of soil-chitosan interactions affecting mechanical strength are discussed and linked with soil water stability and wettability.

Recent Advances in Natural Polyphenol Research.

Polyphenols are secondary metabolites produced by plants, which contribute to the plant's defense against abiotic stress conditions (e.g., UV radiation and precipitation), the aggression of herbivores, and plant pathogens. Epidemiological studies suggest that long-term consumption of plant polyphenols protects against cardiovascular disease, cancer, osteoporosis, diabetes, and neurodegenerative diseases. Their structural diversity has fascinated and confronted analytical chemists on how to carry out unambiguous identification, exhaustive recovery from plants and organic waste, and define their nutritional and biological potential. The food, cosmetic, and pharmaceutical industries employ polyphenols from fruits and vegetables to produce additives, additional foods, and supplements. In some cases, nanocarriers have been used to protect polyphenols during food processing, to solve the issues related to low water solubility, to transport them to the site of action, and improve their bioavailability. This review summarizes the structure-bioactivity relationships, processing parameters that impact polyphenol stability and bioavailability, the research progress in nanocarrier delivery, and the most innovative methodologies for the exhaustive recovery of polyphenols from plant and agri-waste materials.

Natural plant fibers obtained from agricultural residue used as an ingredient in food matrixes or packaging materials: A review.

Every year, agrifood activities generate a large amount of plant byproducts, which have a low economical value. However, the valorization of these byproducts can contribute to increasing the intake of dietary fibers and reducing the environmental pollution. This review presents an overview of a wide variety of agricultural wastes applied in the formulation of different food products and sustainable packaging. In general, the incorporation of fibers into bakery, meat, and dairy products was successful, especially at a level of 10% or less. Fibers from a variety of crops improved the consistency, texture, and stability of sauce formulations without affecting sensory quality. In addition, fiber fortification (0.01-6.4%) presented considerable advantages in terms of rheology, texture, melting behavior, and fat replacement of ice cream, but in some cases had a negative impact on color and mouthfeel. In the case of beverages, promising effects on texture, viscosity, stability, and appetite control were obtained by the addition of soluble dietary fibers from grains and fruits with small particle size. Biocomposites used in packaging benefited from reinforcing effects of various plant fiber sources, but the extent of modification depended on the matrix type, fiber pretreatment, and concentration. The information synthesized in this contribution can be used as a tool to screen and select the most promising fiber source, fiber concentration, and pretreatment for specific food applications and sustainable packaging.

Production of arachidonic acid by Mortierella alpina using wastes from potato chips industry.

AIMS: This research aimed to determine the potential use of wastes from the potato chips industry as a carbon source to develop an economical culture medium for the production of biomass, lipids and arachidonic acid (ARA) by Mortierella alpina. METHODS AND RESULTS: A synthetic culture medium was optimized using a Plackett-Burman and central composite rotatable design, and used as a base to evaluate and characterize the potential use of wastes from the potato chips industry as carbon sources for the production of biomass, lipids and ARA by M. alpina. The waste was selected among other solid and liquid hydrolysed residues/by-products, and local low-cost alternatives for nitrogen sources were also evaluated. After 6 days of fermentation, the biomass concentration reached 20 g l-1 with 40% of total lipids, and a 35% ARA content in the lipids fraction. Savings in production were calculated using a sensitivity analysis for the alternative culture medium in different scenarios. CONCLUSIONS: This study showed a 7% savings in culture media expenses in the production of ARA-enriched biomass of M. alpina, compared to the conventional synthetic culture medium, when waste from the potato chips industry was used as an alternative source of carbon and macro/microelements, supplemented with a low-cost yeast extract alternative. SIGNIFICANCE AND IMPACT OF THE STUDY: The demonstration of the use of potato chips wastes as a low-cost carbon source for the biomass, lipids and ARA production, suggesting an eco-friendly alternative for the use of agri-food wastes for valuable metabolites production.

Recovery of Chlorogenic Acids from Agri-Food Wastes: Updates on Green Extraction Techniques.

The agri-food sector produces a huge amount of agri-food wastes and by-products, with a consequent great impact on environmental, economic, social, and health aspects. The reuse and recycling of by-products represents a very important issue: for this reason, the development of innovative recovery and extraction methodologies must be mandatory. In this context of a circular economy, the study of green extraction techniques also becomes a priority in substitution of traditional extraction approaches. This review is focused on the recovery of chlorogenic acids from agri-food wastes, as these compounds have an important impact on human health, exhibiting several different and important healthy properties. Novel extraction methodologies, namely microwave and ultrasound-assisted extractions, supercritical fluid extraction, and pressurized-liquid extraction, are discussed here, in comparison with conventional techniques. The great potentialities of these new innovative green and sustainable approaches are pointed out. Further investigations and optimization are mandatory before their application in industrial processes.

Impact of the dietary inclusion of dried food residues on the apparent nutrient digestibility and the intestinal microbiota of dogs.

The use of food residues for animal nutrition might imply ecological and economic advantages; however, their effects as a potential ingredient have not yet been evaluated in dogs. In the present study, four diets with 0, 5, 10 and 15% dried food residues (DFR), derived from hotel catering, were fed to 10 healthy adult dogs. At the end of each three-week feeding period, faeces and blood were collected. The apparent nutrient digestibility was calculated by the dietary inclusion of titanium dioxide as an inert marker. The results demonstrated that the apparent crude protein digestibility and ether extract digestibility decreased with increasing amounts of DFR in the diets (p < 0.05). In addition, an increase of the faecal concentrations of acetic acid, propionic acid, n-butyric acid and total short-chain fatty acids (SCFA) was observed (p < 0.05). Faecal ammonium and lactate concentrations, as well as plasma phenol and indole concentrations, were not linearly affected by the dietary inclusion of DFR. The relative abundance of Fusobacteria in the faeces of the dogs decreased, and the relative abundance of Actinobacteria and Bacteroidetes increased with increasing amounts of DFR in the diets (p < 0.05). In conclusion, the DFR seemed to be intensively fermented by the intestinal microbiota of the dogs, as indicated by the increased faecal SCFA concentrations and the shifts in the composition of the faecal microbiota. Dietary inclusion levels of up to 5% can be recommended based on our results, as the observed lower apparent crude protein and ether extract digestibility might limit the use of food residues for dogs at higher amounts.

An overview of the recent trends on the waste valorization techniques for food wastes.

A critical and up-to-date review has been conducted on the latest individual valorization technologies aimed at the generation of value-added by-products from food wastes in the form of bio-fuels, bio-materials, value added components and bio-based adsorbents. The aim is to examine the associated advantages and drawbacks of each technique separately along with the assessment of process parameters affecting the efficiency of the generation of the bio-based products. Challenges faced during the processing of the wastes to each of the bio-products have been explained and future scopes stated. Among the many hurdles encountered in the successful and high yield generation of the bio-products is the complexity and variability in the composition of the food wastes along with the high inherent moisture content. Also, individual technologies have their own process configurations and operating parameters which may affect the yield and composition of the desired end product. All these require extensive study of the composition of the food wastes followed by their effective pre-treatments, judicial selection of the technological parameters and finally optimization of not only the process configurations but also in relation to the input food waste material. Attempt has also been made to address the hurdles faced during the implementation of such technologies on an industrial scale.