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This study produced pH-sensing carboxymethyl cellulose (CMC) films functionalized with bioactive compounds obtained by pressurized liquid extraction (PLE) of grape peel to monitor the freshness of pork and milk. A semi-continuous PLE was conducted using hydroethanolic solution (70:30, v/v) at a flow rate of 5 mL/min, 15 MPa, and 60 °C. The films were produced by the casting technique using CMC (2.5 %, w/v), glycerol (1 %, v/v), and functionalized with 10, 30, and 50 % (v/v) grape peel extract. From the results obtained, LC-MS/MS revealed that PLE extracted twenty-seven phenolic compounds. The main phenolic compounds were kaempferol-3-glucoside (367.23 ± 25.88 µg/mL), prunin (270.23 ± 3.62 µg/mL), p-coumaric acid (236.43 ± 26.02 µg/mL), and procyanidin B1 (117.17 ± 7.29 µg/mL). The CMC films presented suitable color and mechanical properties for food packaging applications. The addition of grape peel extract promoted the pH-sensing property, showing the sensitivity of anthocyanins to pH changes. The films functionalized with grape peel extract presented good release control of bioactive compounds, making them suitable for food packaging applications. When applied to monitor the freshness of pork and milk, the films exhibited remarkable color changes associated with the pH of the food during storage. In conclusion, PLE is a sustainable approach to obtaining bioactive compounds from the grape peel, which can be applied in the formulation of pH-sensing films as a promising sustainable material to monitor food freshness during storage.

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This study evaluated the use of a semi-continuous high-pressure hydrothermal process for the recovery of value-added products from pitaya peel. The process was carried out at 15 MPa, a water flow rate of 2 mL/min, a solvent-to-feed ratio of 60 g water/g pitaya peel, and temperatures ranging from 40 to 210 °C. The results show that extraction temperatures (between 40 and 80 °C) promoted the recovery of betacyanin (1.52 mg/g), malic acid (25.6 mg/g), and citric acid (25.98 mg/g). The major phenolic compounds obtained were p-coumaric acid (144.63 ± 0.42 µg/g), protocatechuic acid (91.43 ± 0.32 µg/g), and piperonylic acid (74.2 ± 0.31 µg/g). The hydrolysis temperatures (between 150 and 210 °C) could produce sugars (18.09 mg/g). However, the hydrolysis process at temperatures above 180 °C generated Maillard reaction products, which increased the total phenolic compounds and antioxidant activity of the hydrolysates. Finally, the use of semi-continuous high-pressure hydrothermal process can be a sustainable and promising approach for the recovery of value-added compounds from pitaya peel, advocating a circular economy approach in the agri-food industry.

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ABSTRACTThis study evaluated the effectiveness of a semi-continuous flow-through subcritical water hydrolysis (SWH) pretreatment of brewer's spent grains (BSG) for subsequent application in the anaerobic digestion (AD) process. BSG pretreatment was conducted at 160 °C and 15 MPa with a flow rate of 10 mL water min-1 and 15 g water g-1 BSG. The results revealed that SWH attacked the hemicellulose structure, releasing arabinose (46.54 mg g-1) and xylose (39.90 mg g-1) sugars, and proteins (34.89 mg g-1). The start-up of anaerobic reactors using pretreated BSG (747.71 L CH4 kg-1 TVS) increased the methane yield compared with the reactor without pretreatment (53.21 L CH4 kg-1 TVS). For the process with pretreatment, the generation of electricity (134 kWh t-1 BSG) and heat (604 MJ t-1) are responsible for the mitigation of 43.90 kg CO2 eq t-1 BSG. The adoption of SWH as an eco-friendly pretreatment of biomass for AD could be a technological route to increase methane-rich biogas and bioenergy production, supporting the circular economy transition by reducing the carbon footprint of the beer industry.

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The detection of analytes in complex organic matrices requires a series of analytical steps to obtain a reliable analysis. Sample preparation can be the most time-consuming, prolonged, and error-prone step, reducing the reliability of the investigation. This review aims to discuss the advantages and limitations of extracting bioactive compounds, sample preparation techniques, automation, and coupling with on-line detection. This review also evaluates all publications on this topic through a longitudinal bibliometric analysis, applying statistical and mathematical methods to analyze the trends, perspectives, and hot topics of this research area. Furthermore, state-of-the-art green extraction techniques for complex samples from vegetable matrices coupled with analysis systems are presented. Among the extraction techniques for liquid samples, solid-phase extraction was the most common for combined systems in the scientific literature. In contrast, for on-line extraction systems applied for solid samples, supercritical fluid extraction, ultrasound-assisted extraction, microwave-assisted extraction, and pressurized liquid extraction were the most frequent green extraction techniques.

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This study aimed to extract anthocyanins from dried and semi-defatted açaí pulp using green technologies based on the coupling of pressurized liquid extraction (PLE) with in-line purification through solid-phase extraction (SPE) and on-line analysis by high-performance liquid chromatography (HPLC). Critical parameters that affect the extraction efficiency and purification were investigated and optimized by response surface methodology (RSM). PLE was performed with acidified water at different pH (2.0, 4.5, and 7.0) and temperatures (40, 80, and 120 °C) at 15 MPa, 2 mL/min, and solvent-to-feed mass ratio equal to 40. SPE was optimized in a column packed with the adsorbent PoraPak™ Rxn. Different ethanol concentrations (50, 75, and 100 %) and temperatures (30, 40, and 50 °C) were evaluated for the anthocyanin's elution. The optimal conditions of the two experimental designs were determined by the RSM, firstly for PLE: 71 °C and pH 2; then using this PLE condition, the optimization of the SPE was obtained: 30 °C and 50 % ethanol. The developed PLE method provided similar anthocyanin yield to other techniques, and the coupling with SPE in-line produced an extract 5-fold more concentrated than PLE alone. Therefore, the system (PLE-SPE × HPLC-PDA) proved to be a powerful tool for monitoring the extraction process in real-time.

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The valorization of the by-product of the agro-industrial processing of jabuticaba (Myrciaria cauliflora) was studied by hydrothermal pretreatment. Experiments were carried out in a semi-continuous flow-through process for 45 min, at 15 MPa, a water flow rate of 5 mL min-1, and at different temperatures (60 - 210 °C). The results demonstrate that fructose and glucose were the sugars with the highest concentration in all analyzed treatments. Arabinose and cellobiose were obtained only at higher temperatures (above 130 °C), demonstrating that they were released from the hydrolysis of polysaccharides. The highest cyanidin-3-glucoside yield (1.88 mg g-1) was achieved at 60 °C. The treatments at 135 and 210 °C promoted the degradation of cyanidin-3-glucoside, leading to yields lower than 0.05 mg g-1. At 60 °C, it was possible to recover 74.18 mg g-1 of glucose, 103.77 mg g-1 of fructose, 30.75 mg g-1 of citric acid, and 1.88 mg g-1 of cyanidin-3-glucoside, without the presence of furfural and 5-hydroxymethylfurfural. The results suggest that hydrothermal pretreatment is a promising eco-friendly technology to recover sugars, organic acids, and anthocyanins from jabuticaba by-products in a circular economy framework.

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This study evaluated the subcritical water hydrolysis (SWH) of brewer's spent grains (BSG) to obtain sugars and amino acids. The experimental conditions investigated the hydrolysis of BSG in a single flow-through reactor and in two sequential reactors operated in semi-continuous mode. The hydrolysis experiments were carried out for 120 min at 15 MPa, 5 mL water min-1, at different temperatures (80 - 180 °C) and using an S/F of 20 and 10 g solvent g-1 BSG, for the single and two sequential reactors, respectively. The highest monosaccharide yields were obtained at 180 °C in a single reactor (47.76 mg g-1 carbohydrates). With these operational conditions, the hydrolysate presented xylose (0.477 mg mL-1) and arabinose (1.039 mg mL-1) as main sugars, while low contents of furfural (310.7 µg mL-1), 5-hydroxymethylfurfural (<1 mg L-1), and organic acids (0.343 mg mL-1) were obtained. The yield of proteins at 180 °C in a process with a single reactor was 43.62 mg amino acids g-1 proteins, where tryptophan (215.55 µg mL-1), aspartic acid (123.35 µg mL-1), valine (64.35 µg mL-1), lysine (16.55 µg mL-1), and glycine (16.1 µg mL-1) were the main amino acids recovered in the hydrolysate. In conclusion, SWH pretreatment is a promising technology to recover bio-based compounds from BSG; however, further studies are still needed to increase the yield of bioproducts from lignocellulosic biomass to explore two sequential reactors.

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The comprehensive analysis of phenolic compounds from natural products comprises critical steps, including quantitative extraction, extract preparation, and chromatographic procedure. Performing these steps off-line requires a long time to obtain results, besides being laborious and more error-prone. This work discusses the concept and presents the details of assembling and validating a new system to comprehensively analyze phenolic compounds in natural products. The system is based on a bidimensional separation through the combination of pressurized liquid extraction with in-line solid-phase extraction coupled online with HPLC-PDA. The system proved to be able to perform a bidimensional separation to characterize the sample and ensure quantitative extraction of all detected components using the most appropriate extraction solvent gradient depending on the raw sample analyzed. The 1st dimension separation is achieved by PLE-SPE with a solvent gradient and differential interactions of extracted compounds with the adsorbent. The 2nd dimension presents the HPLC-PDA separation. The extraction/separation process can be monitored in real-time, and kinetic extraction curves for individual compounds can also be obtained to ensure quantitative extraction. Thus, the 2D PLE-SPE × HPLC-PDA may provide fast and precise comprehensive analyses of a large plethora of phenolic compounds, finding relevant applications in the chemical, food, pharmaceutical, and agricultural fields.

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Flavonoids are one of the main groups of polyphenols found in natural products. Traditional flavonoid extraction techniques are being replaced by advanced techniques to reduce energy and solvent consumption, increase efficiency and selectivity, to meet increased market demand and environmental regulations. Advanced technologies, such as microwaves, ultrasound, pressurized liquids, supercritical fluids, and electric fields, are alternatives currently being used. These modern techniques are generally faster, more environmentally friendly, and with higher automation levels compared to conventional extraction techniques. This review will discuss the different methods available for flavonoid extraction from natural sources and the main parameters involved (temperature, solvent, sample quantity, extraction time, among others). Recent trends and their industrial importance are also discussed in detail, providing insight into their potential. Thus, this paper seeks to review the innovations of compound extraction techniques, presenting in each of them their advantages and disadvantages, trying to offer a broader scope in the understanding of flavonoid extraction from different plant matrices.

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This work involves the application of physical separation methods to concentrate the pigment of semi-defatted annatto seeds, a noble vegetal biomass rich in bixin pigments. Semi-defatted annatto seeds are the residue produced after the extraction of the lipid fraction from annatto seeds using supercritical fluid extraction (SFE). Semi-defatted annatto seeds are use in this work due to three important reasons: i) previous lipid extraction is necessary to recovery the tocotrienol-rich oil present in the annatto seeds, ii) an initial removal of the oil via SFE process favors bixin separation and iii) the cost of raw material is null. Physical methods including i) the mechanical fractionation method and ii) an integrated process of mechanical fractionation method and low-pressure solvent extraction (LPSE) were studied. The integrated process was proposed for processing two different semi-defatted annatto materials denoted Batches 1 and 2. The cost of manufacture (COM) was calculated for two different production scales (5 and 50L) considering the integrated process vs. only the mechanical fractionation method. The integrated process showed a significantly higher COM than mechanical fractionation method. This work suggests that mechanical fractionation method is an adequate and low-cost process to obtain a rich-pigment product from semi-defatted annatto seeds.

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