Ultrasonic Processing of Food Waste to Generate Value-Added Products

Raw biowaste conversion to high-value compounds for food, cosmetic and pharmaceutical industries

Biowaste valorisation into high-value compounds is one of the main challenges of green chemistry, as chemicals produced from biological sources are identified as key substances in the development of a low-carbon and circular bioeconomy in connection with the transition from fossil to renewable feedstocks. The review summarizes the production of high-value products such as glucose-based chemicals, phenolic compounds and volatile-fatty acids prepared from biomass waste. Biowaste pretreatment methods such as milling, filtration and extraction followed by current non-catalytic methods such as microwave or ultrasound extraction and catalytic methods for the production value-added compounds in the presence of various catalyst types in conventional, nano or enzyme form are listed with a focus on value-added chemicals applied in the food, cosmetic and pharmaceutical industries. The economic feasibility, technical aspects and concept of the biorefinery are briefly mentioned, emphasizing the necessity of life cycle assessment for each bioproduct and technological process. Finally, it provides a future perspective and makes recommendations for potential research strategies, recognizing the importance of utilizing biomass waste for the production of useful compounds as an attractive and environmentally friendly approach whose development should be encouraged. The utilization of biowaste for high-value chemicals production shows high potential, however, there are still many challenges to be resolved throughout the entire production chain, reflecting technological, economic, ecological, sociological and long-term issues.

Modeling of the biomethane production from ultrasonic pretreated fruit and vegetable waste via anaerobic digestion

The global dependency on the depleted fossil fuels has led to the quest for acquiring alternative energy sources. Different types of waste material are generated at a high rate and tapping into their use for greener, alternative energy production is an option. The mesophilic anaerobic co-digestion of fruit and vegetable waste and wastewater treatment plant sewage sludge experiments were conducted using ultrasonic pretreated substrates. Sonication exposure times from 0 to 45 min were selected for the experiments. An automatic methane potential test system (BMP) was used to determine the production rate of biomethane of the fruit and vegetables waste containing 60% fruit and 40% vegetables. The highest cumulative methane production of 238 mL g-1 VS was achieved at sonication time exposure of 45 min. It was observed that an increase in ultrasonic sonication exposure time, improved methane yield. The resulting experimental data was fitted with the modified Gompertz, co-digestion modified Gompertz, original Richards, modified Richards and co-digestion modified Richards models. IBM SPSS Statistics software was used for curve fitting and the estimation of the models' kinetic parameters. The modified Gompertz and Richards models showed higher goodness fit, both with R2 of 0.93 and modified Richards models did not produce a good fit for the data, with R2 of 0.7. The developed co-digestion models considered a combination of substrates that were easily digested as well as complex substrates that required multiple steps of digestion. The results show that the co-digestion modified Gompertz model had a goodness of fit of 0.98. Co-digestion modified Richard's model perfectly fit the experimental data, with R2 of 1. Both the co-digestion modified models are recommended due to their fitting performance. Fruit and vegetable waste comprise multiple substrates including simple sugars that digest readily and much more complex cellulose substrates that require more steps to digest and requiring the second step of digestion after undergoing hydrolysis. Both models took that into account. The aim of this study was to evaluate the suitability of the Gompertz and Richards model in the co-digestion of fruit and vegetables waste with sludge, as well as to develop co-digestion models for the substrates at hand.

Producing and Characterizing Polyhydroxyalkanoates from Starch and Chickpea Waste Using Mixed Microbial Cultures in Solid-State Fermentation

The environmental impact of plastic waste is a growing global challenge, primarily due to non-biodegradable plastics from fossil resources that accumulate in ecosystems. Biodegradable polymers like polyhydroxyalkanoates (PHAs) offer a sustainable alternative. PHAs are microbial biopolymers produced by microorganisms using renewable substrates, including agro-industrial byproducts, making them eco-friendly and cost-effective. This study focused on the isolation and characterization of PHA-producing microorganisms from agro-industrial waste, including chickpeas, chickpeas with bean residues, and starch. Screening via Sudan Black staining identified PHA-accumulating strains such as Brevibacillus sp., Micrococcus spp., and Candida krusei, among others. To assess the potential for PHA biosynthesis, solid-state fermentation (SSF) was conducted using agro-industrial waste as substrates, along with a mixed culture of the isolated microorganisms. The highest observed yield was a PHA accumulation of 13.81%, achieved with chickpeas containing bean residues. Structural and thermal characterization of the PHAs was performed using Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). FTIR-ATR spectra indicated polyhydroxybutyrate (PHB), suggesting it as the synthesized PHA type. This study highlights the potential of agro-industrial waste for sustainable PHA production and eco-friendly bioplastics.

Microwave-sonication synergistic extraction of dairy waste proteins: A review of green approach for dairy waste proteins valorization

Ultrasonic and microwave extraction process has great prospects to convert food and agricultural waste from food industries to value-added goods. Also, this review extensively elaborates the utilization of ultrasonication and microwave extraction (US-MW) process for valorization of dairy waste extracted proteins into novel foods. Both of these extraction and processing techniques are considered as green technologies when compared with the other conventional or chemical extraction and processing techniques. Further, this review also explains the impact of US-MW alone and in combination on the dairy waste proteins extraction, nutritional and techno-functional attributes of these dairy-waste proteins. The review also highlights the economic and cost-effective benefits of US-MW processes for extracting the proteins from dairy waste, indicating their feasibility and sustainability. The review also elucidated the synergistic utilization of US-MW extraction as a viable processing technique in extraction or production of bioactive compounds like dairy proteins. In conclusion, this review elucidates the US-MW, both individually and in synergy as a viable source of dairy waste proteins extraction and their application in functional foods. Moreover, in accordance to the latest developments and future prospects at pilot and commercial level to assess the practicability of synergistic use of US-MW extraction in bioenergy production from food wastes other than dairy waste for extraction and production of biodiesel, hydrogen, green methane, and ethanol.

Optimizing physicochemical properties, antioxidant potential, and antibacterial activity of dry ginger extract using sonication treatment

This research paper focused on enhancing the physico-chemical attributes, antioxidant capacity, and antibacterial effectiveness of dry ginger extract through sonication as an assistant extraction treatment. Ginger, resulting from the rhizome of Zingiber officinale Roscoe, is known for its culinary and medicinal uses outstanding to its antioxidant and antimicrobial possessions from phenolic acids and flavonoids. The study explored the use of sonication as an assistant extraction method and found that it significantly augmented the total phenolic content of the ginger extract by 28 % compared to traditional extraction methods, reaching 10.55 ± 1.50 mg GAE/g, DW. The research assessed the physicochemical belongings, antioxidant action, and antibacterial possibility of the sonicated ginger extract. The sonicated extract exhibited scavenging activity against the DPPH radical of 56.0 %. Pearson correlation investigation revealed a strong confident correlation between the phenolic content and antioxidant activity (r = 0.92, p < 0.01), as well as volatile compounds exhibited a moderate confident correlation with antibacterial action (r = 0.67, p < 0.05). The sonicated ginger extract also demonstrated potent antibacterial action, preventing the growth of both Gram-positive and Gram-negative bacteria. These findings contribute to the development of more efficient methods for extracting phenolic from ginger and provide insights into the relationships between phenolic and bioactive properties.

Influence of intensity ultrasound on rheological properties and bioactive compounds of araticum (Annona crassiflora) juice

The use of extracts rich in bioactive compounds is becoming increasingly common in the food, cosmetics, and pharmaceutical industries for the production of functional products. Araticum is a potential fruit to be analyzed due to its content of phenolic compounds, carotenoids and vitamins, with antioxidant properties. Therefore, this study aimed to investigate the effect of ultrasound on total phenolic compounds, total carotenoids, ascorbic acid, color, turbidity and rheology in araticum juice. Response surface methodology based on a central composite design was applied. Araticum juice was subjected to sonication at amplitude levels ranging from 20 to 100 % of the total power (400 W) at a constant frequency of 20 kHz for different durations (2 to 10 min). Morphological analysis was conducted to observe microscopic particles, and viscosity and suitability to rheological models (Newtonian, Power Law, and Herschel-Bulkley) were assessed. The ultrasonic probe extraction method was compared to the control juice. According to the responses, using the desirability function, the optimal conditions for extraction were determined to be low power (low amplitude) applied in a short period of time or low power applied in a prolonged time. These conditions allowed an ultrasonic probe to act on releasing bioactive compounds without degrading them. All three rheological models were suitable, with the Power Law model being the most appropriate, exhibiting non-Newtonian pseudoplastic behavior.

New Perspectives to Enhance Wastes and By-Products from Agro-Food Processing

The exploitation of by-products and waste from the agri-food industry represents a sustainable approach within the frame of the circular economy, the basis of the European Green Deal and ecological transition [...].

Potential of Modification of Techno-Functional Properties and Structural Characteristics of Citrus, Apple, Oat, and Pea Dietary Fiber by High-Intensity Ultrasound

Plant fibers are rich in dietary fiber and micronutrients but often exhibit poor functionality. Ultrasonication can affect the particle size of plant fiber, thereby influencing other techno-functional properties. Therefore, this study aimed to investigate the effects of high-intensity ultrasound on citrus, apple, oat, and pea fiber. Initially, solutions containing 1 wt% of plant fiber were homogenized using ultrasonication (amplitude 116 µm, t = 150 s, energy density = 225 kJ/L, P¯ = 325 W). Due to cavitation effects induced by ultrasound, differences in particle size and a shift in the ratio of insoluble and alcohol-insoluble fractions for dietary fiber were observed. Additionally, viscosities for citrus and apple fiber increased from 1.4 Pa·s to 84.4 Pa·s and from 1.34 Pa·s to 31.7 Pa·s, respectively, at shear rates of 100 1s. This was attributed to observed differences in the microstructure. Freeze-dried samples of purified citrus and apple fiber revealed thin and nearly transparent layers, possibly contributing to enhanced water binding capacity and, therefore, increased viscosity. Water binding capacity for citrus fiber increased from 18.2 g/g to 41.8 g/g, and a 40% increase was observed for apple fiber. Finally, ultrasound demonstrated itself be an effective technology for modifying the techno-functional properties of plant fiber, such as water binding capacity.

Emerging trends in the appliance of ultrasonic technology for valorization of agricultural residue into versatile products

The utilization of agricultural residues to obtain biocompounds of high-added value has significantly increased in the past decades. The conversion of agro-based residues into valuable products appears to be an economically efficient, environment-friendly, and protracted waste management practice. The implementation of ultrasonic technologies in the conversion of value-added goods from agricultural waste materials through pre-treatment and valorization processes has imparted many advantageous effects including rapid processing, effective process performance, minimization of processing steps, minimal dependency on harmful chemicals, and an increased yield and properties of bio-products. To further enliven the literature and inspire new research investigations, this review covers the comprehensive work including theoretical principles, processes, and potential benefits of ultrasonic treatment technologies to assist the production of bio-products which emphasize the extraction yield and the characteristic of the end-product extracted from agriculture residues. A detailed evaluation of these methods and key aspects impacting their performance as well as the features and shortcomings of each ultrasound-assisted approach is also discussed. This review also addressed some of the challenges associated with using ultrasonic irradiation and proposed several potential techniques to maximize productivity. Understanding the concept of ultrasonication technique allow the academician and industrial practitioners to explore the possibility of applying a greener and sustainable approach of biomass extraction to be translated into higher scale production of commercial products.

Influence of High-Intensity Ultrasound on Characteristics and Bioaccessibility of Pea Protein in Fiber-Enriched Suspensions

Pea protein is of high interest for the food industry owing to its low allergenicity and high nutritional value. However, it often exhibits poor functionality, such as low solubility. The presence of dietary fiber in food products is beneficial for human health but may decrease the bioaccessibility of nutrients. Ultrasound, as a promising green technology, may influence properties of fibers and proteins and, thus, bioaccessibility. Therefore, this study investigated the effects of high-intensity ultrasound on the characteristics and protein bioaccessibility of protein-fiber suspensions. Suspensions containing different fiber compounds (1 wt.%) and pea protein (5 wt.%) were homogenized using high-intensity ultrasound (amplitude 116 µm, t = 150 s, energy density = 225 kJ/L, P¯ = 325 W). Owing to sonication-induced cavitation, the dispersibility of the protein was enhanced, and the viscosity of solutions containing citrus or apple fiber was increased. FE-SEM revealed the formation of different fiber-protein networks during sonication. Even if viscosity is known to have an impact on the bioaccessibility of nutrients, no restrictions on the digestibility of protein were detected during an in vitro digestion. Thus, protein uptake is probably not affected, and ultrasound can be used to modify the technofunctionality of fibers and proteins without any nutritional disadvantages.

Environment friendly emerging techniques for the treatment of waste biomass: a focus on microwave and ultrasonication processes

In the recent past, an increasing interest is mostly observed in using microwave and ultrasonic irradiation to aid the biological conversion of waste materials into value-added products. This study is focused on various individual impacts of microwaves and ultrasonic waves for the treatment of biomass before the synthesis of value-added products. Following, a comprehensive review of the mechanisms governing microwaves and ultrasonication as the treatment methods, their effects on biomass disruption, solubilization of organic matter, modification of the crystalline structure, enzymatic hydrolysis and production of reducing sugars was performed. However, based on the lab-scale experiments evaluated, microwaves and ultrasonication were studied to be economically and energetically ineffective despite their beneficial effects on the waste biomass. This article reviews some of the difficulties associated with using microwaves and ultrasonic irradiation for the efficient processing of waste biomasses and identified some potential directions for future study.

Ultrasound-Assisted Extraction of Isoquercetin from Ephedra alata (Decne): Optimization Using Response Surface Methodology and In Vitro Bioactivities

Isoquercetin (ISQ) is reported to be a powerful antioxidant with extremely high bioavailability and structural stability compared to aglycone quercetin. Despite this, it is not well studied due to the limited methods for its extraction. With the growing interest in the research and analysis of ISQ-rich herbs, there is a need to optimize an efficient and rapid method for their extraction. In the present study, the ultrasound-assisted extraction of ISQ from Ephedra alata Decne was optimized by a response surface methodology (RSM) using high-performance liquid chromatography as a separation method. The best possible ranges for extraction time (10–30 min), temperature (50–70 °C), ultrasonic power (60–90 W), solvent-to-solid ratio (50–70 mL/g), and ethanol concentration (50–70%) were determined using a single factor analysis. Subsequently, an optimization of the extraction conditions was performed with RSM using the Box–Behnken design. An ultrasonication time of 10 min, a temperature of 60 °C, a power of 75 W, a solvent-to-solid ratio of 60 mL/g, and an ethanol concentration of 70% were determined to be the optimal conditions for the highest recovery of isoquercetin (1033.96 ± 3.28 µg/g). Furthermore, E. alata powder morphology (using a scanning electron microscope), antioxidant activities, and the inhibition potential of key enzymes involved in skin aging (elastase and collagenase), hyperpigmentation (tyrosinase), diabetes (α-amylase), inflammation (hyaluronidase), and neurodegenerative disorders (cholinesterase) were determined and compared with those using the Soxhlet method. This study established a highly efficient method for ISQ extraction and suggested several potential applications of ISQ in the pharmaceutical and cosmetics industries.