Generating phytosterol nanoparticles in nanoporous bioaerogels via supercritical carbon dioxide impregnation: Effect of impregnation conditions

Cornstarch aerogels with thymol, citronellol, carvacrol, and eugenol prepared by supercritical CO2- assisted techniques for potential biomedical applications

This study focuses on the development of bioactive materials using environmentally friendly techniques, renewable, biocompatible, and biodegradable polysaccharide, as well as natural bioactive compounds (NBCs) found in plant extracts. First, cornstarch aerogels with a porosity of 86 % and a specific surface area of 225 m2/g were produced via supercritical CO2- assisted drying. Further, thymol, citronellol, carvacrol, and eugenol were incorporated into the aerogels by supercritical CO2- assisted impregnation, which allowed variation in loadings of NBCs (12.8-17.6 %). Interaction between cornstarch aerogels and NBCs determined impregnation rate, pore wall thickness (in the range 18-95 nm), liquid absorption capacity (from 265 to 569 %), dehydration mass loss, and release in phosphate-buffered saline. Controlled release of NBCs was maintained over a 3-day period. Moreover, impregnated aerogels showed a significant antioxidant effect with the highest value for DPPH radical inhibition of 25.5 % determined for the aerogels impregnated with eugenol. Notable antimicrobial activity against tested Gram-negative bacteria, Gram-positive bacteria, and fungi was also observed, being the highest for thymol-loaded aerogel with the diameter of the inhibition zones of up to 37.5 mm. This work shows a promising green approach for the production of bioactive two-component starch-based materials for potential applications in skin infection treatment.

Current and New Insights on Delivery Systems for Plant Sterols in Food

Plant sterols are minor bioactive components of food lipids, which are often used for the formulation of functional foods due to their cholesterol-lowering properties. However, they have low solubility and tend to crystallize, which may affect their biological effects, the sensory profile of the sterol-enriched food, and its consumer acceptability. Moreover, due to the unsaturated structure of sterols, they are susceptible to oxidation, so different encapsulation systems have been developed to improve their dispersibility/solubility, stability, delivery, and bioaccessibility. This chapter provides an overview of the main encapsulation systems currently used for plant sterols and their application in model and food systems, with a particular focus on their efficiency and impact on sterol bioaccessibility.

Absorbent bioactive aerogels based on germinated wheat starch and grape skin extract

This study aimed to produce water-absorbent bioactive aerogels using biodegradable raw materials, wheat starch and poly ethylene oxide (PEO), and derived from agro-industrial residues (grape skin) obtained in the wine industry. The aerogels were produced using germinated wheat starch (GWS), with and without PEO, and incorporating grape skin extract (GSE) at concentrations of 5 and 10 % (w/w). The GSE was evaluated for total and individual phenolic compounds, anthocyanins, and antioxidant activity. The starch aerogels were characterized for morphology, density, porosity, functional groups by FT-IR, relative crystallinity and diffraction pattern, water absorption capacity, antioxidant activity, and in vitro release profile of phenolic compounds in food simulant medium. The total phenolic compounds in GSE was 226.25 ± 0.01 mg equivalent of gallic acid/g GSE. The aerogels showed low density and high porosity. All aerogels demonstrated high water absorption capacity (581.4 to 997.5 %). The antioxidant activity of the aerogels increased with increasing GSE concentration and the addition of PEO. The aerogels could release GSE gradually for up to 120 days in the hydrophilic simulant medium and 240 h for the hydrophobic medium. Starch-based aerogels with GSE showed potential to be applied as exudate absorbers with antioxidant activity to develop active food packaging.

Amylose content and pre-freezing regulate the structure and oil absorption of polyelectrolytes-based starch cryogel

Starch cryogel is a potential material for oil absorption. This study provided a facile and convenient polyelectrolyte-based preparation strategy of starch cryogel, in which the structural properties of the cryogel were regulated by amylose content and pre-freezing without long-time retrogradation. Sodium laurate was used as a guest model to form starch-fatty acid salt complex (polyelectrolyte). The amount of amylose content and sodium laurate added led more polyelectrolytes, significantly increased V-type crystallinity from 3.72 % to 22.40 % and complexing index from 4.32 % to 28.48 %. As the uniform pore structure improved the oil absorption ability of starch cryogel, the starch cryogel prepared by waxy maize starch followed by quick pre-freezing showed the highest specific surface area (9.87 m²/g) and oil absorption capacity (32.94 g/g). Our findings suggest that polyelectrolyte properties have great potential in the preparation of starch-based cryogels, which could be applied in the design of novel starch-based porous materials.

Polysaccharide-based porous biopolymers for enhanced bioaccessibility and bioavailability of bioactive food compounds: Challenges, advances, and opportunities

Bioactive food compounds, such as lycopene, curcumin, phytosterols, and resveratrol, have received great attention due to their potential health benefits. However, these bioactive compounds (BCs) have poor chemical stability during processing and low bioavailability after consumption. Several delivery systems have been proposed for enhancing their stability and bioavailability. Among these methods, porous biopolymers have emerged as alternative encapsulation materials, as they have superior properties like high surface area, porosity, and tunable surface chemistry to entrap BCs. This reduces the crystallinity (especially for the lipophilic ones) and particle size, and in turn, increases solubilization and bioavailability. Also, loading BCs into the porous matrix can protect them against environmental stresses such as light, heat, oxygen, and pH. This review introduces polysaccharide-based porous biopolymers for improving the bioaccessibility/bioavailability of bioactive food compounds and discusses their recent applications in the food industry. First, bioaccessibility and bioavailability are described with a special emphasis on the factors affecting them. Then, porous biopolymer fabrication methods, including supercritical carbon dioxide (SC-CO₂ ) drying, freeze-drying, and electrospinning and electrospraying, are thoroughly discussed. Finally, common polysaccharide-based biopolymers (i.e., starch, nanocellulose, alginate, and pectin) used for generating porous materials are reviewed, and their current and potential future food applications are critically discussed.

Supercritical CO2 Impregnation of Thymol in Thermoplastic Starch-Based Blends: Chemico-Physical Properties and Release Kinetics

The aim of the present study was to investigate starch-based materials, prepared in an environmentally friendly way and from renewable resources, suitable for the development of biodegradable active food packaging. For this purpose, a bioactive compound (thymol) was incorporated into thermoplastic starch (TPS) and a TPS blend with poly (ε-caprolactone) (TPS-PCL) by the supercritical CO₂ (scCO₂) impregnation process. Impregnation experiments with scCO₂ were carried out at a pressure of 30 MPa and temperatures in the range of 40-100 °C during 1 to 20 h. The structural, morphological, and thermal properties of the obtained materials were comprehensively evaluated. Bioactive component release kinetic studies were performed in water at 6 °C and 25 °C. It was shown that the scCO₂ impregnation process could be successfully employed for thymol loading into TPS and TPS-PCL. The process was significantly influenced by the operating temperature and time as well as content of PCL. The samples showed a controlled release of thymol within seven days with a higher amount of released thymol from the TPS-PCL blend. The obtained materials are solvent-free and release the bioactive component in a controlled manner.

Bio-aerogels: Fabrication, properties and food applications

Traditional inorganic aerogels sustainability, biodegradability, and environmental safety concerns have driven researchers to find their safe green alternatives. Recently, interest in the application of bio-aerogels has rapidly increased in the food industry due to their unique characteristics such as high specific surface area and porosity, ultralow density, tunable pore size and morphology, and superior properties (physicochemical, mechanical, and functional). Bio-aerogels, a special category of highly porous unique materials, fabricated by the sol-gel method followed by drying processes, comprising three-dimensional networks of interconnected biopolymers (e.g., polysaccharides and proteins) with numerous air-filled pores. The production of bio-aerogels begins with the formation of a homogeneously dispersed precursor solution, followed by gelation and wet gel drying procedures by employing special drying techniques including atmospheric-, freeze-, and supercritical drying. Due to their special properties, bio-aerogels have emerged as sustainable biomaterial for many industrial applications, i.e., encapsulation and controlled delivery, active packaging, heavy metals separation, water and air filtration, oleogels, and biosensors. Bio-aerogels are low-cost, biocompatible, and biodegradable sustainable material that can be used in improving the processing, storage, transportation, and bioavailability of food additives, functional ingredients, and bioactive substances for their health benefits with enhanced shelf-life.

Enhancing the bioaccessibility of lycopene from tomato processing byproducts via supercritical carbon dioxide extraction

Tomato peel and seed from tomato processing industry are treated as waste; however, they contain lycopene, a high-value bioactive compound. In this study, lycopene was extracted from tomato peel and seed using supercritical carbon dioxide (SC–CO₂) and hexane, and the bioaccessibilities of lycopene in the SC-CO₂- and hexane-extracted oleoresins were investigated for the first time. The (Z)-lycopene content of the SC-CO₂-extracted oleoresin (69%) was higher than that of hexane-extracted oleoresin (45%). Separation of the insoluble fraction from the oleoresins increased the (Z)-lycopene contents of the SC-CO₂- and hexane-extracted oil fractions to 80% and 49%, respectively. The bioaccessibility of total-lycopene in the oleoresins was increased by 3.3-fold via SC-CO₂ extraction, which was attributed to higher (Z)-lycopene content, and small-sized uniform distribution of lycopene in the oleoresin. SC-CO₂ extraction is not only a green method for extraction of bioactive compounds, but also has the potential to improve health benefits of bioactive compounds.

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Lycopene-rich oleoresins were extracted from tomato processing byproducts.

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Supercritical carbon dioxide (SC–CO₂) and hexane extractions were compared.

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SC-CO₂ extraction increased the cis-lycopene content of the oleoresins up to 69%.

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SC-CO₂-extracted oleoresins contained uniform well-dispersed lycopene.

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The bioaccessibility of lycopene was enhanced by 3.3-fold by SC-CO₂ ext.

Water-Dispersible Phytosterol Nanoparticles: Preparation, Characterization, and in vitro Digestion

For improving solubility and bioaccessibility of phytosterols (PS), phytosterol nanoparticles (PNPs) were prepared by emulsification–evaporation combined high-pressure homogenization method. The organic phase was formed with the dissolved PS and soybean lecithin (SL) in anhydrous ethanol, then mixed with soy protein isolate (SPI) solution, and homogenized into nanoparticles, followed by the evaporation of ethanol. The optimum fabrication conditions were determined as PS (1%, w/v): SL of 1:4, SPI content of 0.75% (w/v), and ethanol volume of 16 ml. PNPs were characterized to have average particle size 93.35 nm, polydispersity index (PDI) 0.179, zeta potential −29.3 mV, and encapsulation efficiency (EE) 97.3%. The impact of temperature, pH, and ionic strength on the stability of fabricated PNPs was determined. After 3-h in vitro digestion, the bioaccessibility of PS in nanoparticles reached 70.8%, significantly higher than the 18.2% of raw PS. Upon freeze-drying, the particle size of PNPs increased to 199.1 nm, resulting in a bimodal distribution. The solubility of PS in water could reach up to 2.122 mg/ml, ~155 times higher than that of raw PS. Therefore, this study contributes to the development of functional PS-food ingredients.

Natural antimicrobials and antioxidants added to polylactic acid packaging films. Part I: Polymer processing techniques

Currently, reducing packaging plastic waste and food losses are concerning topics in the food packaging industry. As an alternative for these challenges, antimicrobial and antioxidant materials have been developed by incorporating active agents (AAs) into biodegradable polymers to extend the food shelf life. In this context, developing biodegradable active materials based on polylactic acid (PLA) and natural compounds are a great alternative to maintain food safety and non-toxicity of the packaging. AAs, such as essential oils and polyphenols, have been added mainly as antimicrobial and antioxidant natural compounds in PLA packaging. In this review, current techniques used to develop active PLA packaging films were described in order to critically compare their feasibility, advantages, limitations, and relevant processing aspects. The analysis was focused on the processing conditions, such as operation variables and stages, and factors related to the AAs, such as their concentrations, weight losses during processing, and incorporation technique, among others. Recent developments of active PLA-based monolayers and bi- or multilayer films were also considered. In addition, patents on inventions and technologies on active PLA-based films for food packaging were reviewed. This review highlights that the selection of the processing technique and conditions to obtain active PLA depends on the type of the AA regarding its volatility, solubility, and thermosensitivity.

A review on chemical and physical modifications of phytosterols and their influence on bioavailability and safety

Phytosterols have been shown to lower cholesterol levels and to have antioxidant, anti-inflammatory and other biological activities. However, the high melting point and poor solubility limit their bioavailability and practical application. It is advantageous to modify phytosterols chemically and physically. This article reviews and discusses the chemical and physical modifications of phytosterols, as well as their effects on the bioavailability and possible toxicity in vivo. The current research on chemical modifications is mainly focused on esterification to increase the oil solubility and water solubility. For physical modifications (mainly microencapsulation), there are biopolymer-based, surfactant-based and lipid-based nanocarriers. Both chemical and physical modifications of phytosterols can effectively increase the absorption and bioavailability. The safety of modified phytosterols is also an important issue. Phytosterol esters are generally considered to be safe. However, phytosterol oxides, which may be produced during the synthesis of phytosterol esters, have shown toxicity in animal models. The toxicity of nanocarriers also needs further studies.

Biorefinery Approach for Aerogels

According to the International Energy Agency, biorefinery is "the sustainable processing of biomass into a spectrum of marketable bio-based products (chemicals, materials) and bioenergy (fuels, power, heat)". In this review, we survey how the biorefinery approach can be applied to highly porous and nanostructured materials, namely aerogels. Historically, aerogels were first developed using inorganic matter. Subsequently, synthetic polymers were also employed. At the beginning of the 21st century, new aerogels were created based on biomass. Which sources of biomass can be used to make aerogels and how? This review answers these questions, paying special attention to bio-aerogels' environmental and biomedical applications. The article is a result of fruitful exchanges in the frame of the European project COST Action "CA 18125 AERoGELS: Advanced Engineering and Research of aeroGels for Environment and Life Sciences".

Fabrication of nanostructured mesoporous starch encapsulating soy-derived phytoestrogen (genistein) by well-tuned solvent exchange method

The present research was concerned with preparation of mesoporous starch (MPS) as a carrier for genistein, a model of poorly water-soluble phytoestrogen isoflavone; and exploration of the impact of different fabrication parameters on structural and loading properties. MPS is considered as a highly porous biomaterial which typically possesses nanometer-sized porous microstructure and low density, providing a large effective specific surface area (SSA) and hydrophilic surface to improve solubility, stability and bioavailability of poorly water-soluble active agents. To fabricate MPS, various concentrations (8-14% w/v) of starch from different sources (corn, potato and tapioca) was used for gel formation and the successive solvent exchange process was performed with use of various ethanol concentrations (40-70% v/v), which were then dried by different techniques (rotary vacuum evaporation, microwave and freeze drying). MPS quality attributes such as SSA, total porous volume, BJH pore diameter and swelling ratio were determined and effects of the fabrication parameters were investigated using L9-Taguchi orthogonal array design. The results indicate that second order polynomial regression models were well fitted for all response variables. Interestingly, the starch components greatly influenced physical properties of MPS. Also, the drying type and ethanol concentration altered significantly the model equations. The overall best fabrication condition (14% corn starch, 100% ethanol concentration in aging step and rotary vacuum drying) resulted in favorable MPS preparation with mean size of 105.4 nm and unimodal distribution. In the next step, genistein was encapsulated in MPS microstructure at different ratios, resulting in high loading capacity and efficiency (44.71% and 79.9%, respectively) at 1:1 weight ratio. Equilibrium adsorption isotherm of genistein was evaluated also by four different kinetics models including Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherms. The experimental data were found to be fitted well to the Langmuir model (R2 = 0.989). According to the electron microscopy and XRD analysis, the degree of genistein crystallinity lowered remarkably after the impregnation in to MPS, indicating improved solubility. In-vitro release profile of genistein from MPS in the simulated gastrointestinal buffer solutions (pH 1.2 and 6.8) demonstrated that incorporating genistein into the MPS enhanced the dissolution rate compared with genistein powder. Release kinetic data were fitted to the Higuchi model (R2 = 0.98), indicating diffusion-controlled release mechanism. Altogether, well-tuned MPS fabrication method can be utilized for an efficient encapsulation and dissolution enhancement of poorly soluble phytochemicals, such as genistein.

Pt-Ni Nanoalloys for H2 Generation from Hydrous Hydrazine

Hydrous hydrazine (N2H4∙H2O) is a candidate for a hydrogen carrier for storage and transportation due to low material cost, high hydrogen content of 8.0%, and liquid stability at room temperature. Pt and Pt nanoalloy catalysts have been welcomed by researchers for the dehydrogenation of hydrous hydrazine recently. Therefore, in this review, we give a summary of Pt nanoalloy catalysts for the dehydrogenation of hydrous hydrazine and briefly introduce the decomposition mechanism of hydrous hydrazine to prove the design principle of the catalyst. The chemical characteristics of hydrous hydrazine and the mechanism of dehydrogenation reaction are briefly introduced. The catalytic activity of hydrous hydrazine on different supports and the factors affecting the selectivity of hydrogen catalyzed by Ni-Pt are analyzed. It is expected to provide a new way for the development of high-activity catalysts for the dehydrogenation of hydrous hydrazine to produce hydrogen.

Structural characterization of oleogels from whey protein aerogel particles

Oleogels intended as fat substitutes were prepared by oil dispersion of aerogel particles obtained through freeze-drying (FD) or supercritical-CO₂-drying (SCD) of whey protein isolate (WPI) hydrogels (20 g/100 g). SEM revealed that freeze-dried particles presented larger dimensions than supercritical-dried ones. The latter also showed higher oil dispersibility, forming aggregates with lower dimension (300 nm) than those formed by freeze-dried particles (700 nm). Both particles presented oil structuring capability. Freeze-dried particles gave a weak oleogel, while supercritical-dried ones gave a strong (G' = 3.1 × 10⁵ Pa) and plastic (critical stress = 723.2 Pa) oleogel, with rheological features comparable to those of traditional fats. These results can be explained based on the lower aggregation induced by SCD and on the higher capacity of supercritical-dried particles to form a network in oil through hydrophilic interactions, as suggested by FTIR. Therefore, WPI aerogel particles show the potentiality to be used as food ingredients to prepare oleogels with tailor-made physical properties.

Functional Foods: Product Development, Technological Trends, Efficacy Testing, and Safety

Functional foods is a very popular term in the social and scientific media; consequently, food producers have invested resources in the development of processed foods that may provide added functional benefits to consumers' well-being. Because of intrinsic regulation and end-of-use purposes in different countries, worldwide meanings and definitions of this term are still unclear. Hence, here we standardize this definition and propose a guideline to attest that some ingredients or foods truly deserve this special designation. Furthermore, focus is directed at the most recent studies and practical guidelines that can be used to develop and test the efficacy of potentially functional foods and ingredients. The most widespread functional ingredients, such as polyunsaturated fatty acids (PUFAs), probiotics/prebiotics/synbiotics, and antioxidants, and their technological means of delivery in food products are described. The review discusses the steps that food companies should take to ensure that their developed food product is truly functional.

A novel and green nanoparticle formation approach to forming low-crystallinity curcumin nanoparticles to improve curcumin's bioaccessibility

Health-promoting effects of curcumin are well-known; however, curcumin has a very low bioavailability due to its crystalline structure. The main objective of this study was to develop a novel green nanoparticle formation method to generate low-crystallinity curcumin nanoparticles to enhance the bioavailability of curcumin. Nanoporous starch aerogels (NSAs) (surface area of 60 m²/g, pore size of 20 nm, density of 0.11 g/cm³, and porosity of 93%) were employed as a mold to produce curcumin nanoparticles with the help of supercritical carbon dioxide (SC-CO₂). The average particle size of the curcumin nanoparticles was 66 nm. Impregnation into NSAs decreased the crystallinity of curcumin and did not create any chemical bonding between curcumin nanoparticles and the NSA matrix. The highest impregnation capacity was 224.2 mg curcumin/g NSA. Curcumin nanoparticles significantly enhanced the bioaccessibility of curcumin by 173-fold when compared to the original curcumin. The concentration of curcumin in the bioaccessible fraction was improved from 0.003 to 0.125 mg/mL by impregnation of curcumin into NSAs (42-fold). This is a novel approach to produce food grade curcumin nanoparticles with reduced crystallinity and maximize the utilization of curcumin due to increased bioaccessibility.

In Vitro Bioaccessibility of Low-Crystallinity Phytosterol Nanoparticles Generated Using Nanoporous Starch Bioaerogels

Phytosterols are natural health-promoting bioactive compounds; however, phytosterols have very limited bioavailability due to their crystalline lipophilic structure. With the aim of improving bioaccessibility, low-crystallinity phytosterol nanoparticles were generated by supercritical carbon dioxide (SC-CO₂ ) impregnation of phytosterols into nanoporous starch aerogels (NSAs). The in vitro bioaccessibility of the phytosterol nanoparticles (35%) was significantly higher than that of the crude phytosterols (3%) after sequential oral, gastric, and intestinal digestion. The percentages of starch hydrolysis were not different among the various NSA preparations and reached to 64% after sequential digestion. The zeta potential of the phytosterol nanoparticles was higher compared to that of crude phytosterols in the micellar phase; indicating higher stability. The findings of this study support the use of NSA to produce nanoparticles of reduced crystallinity to improve the bioaccessibility of the lipophilic bioactive compounds. PRACTICAL APPLICATIONS: This novel process can decrease the size and crystallinity of phytosterols and thus improve phytosterols' bioavailability. It is a blueprint to apply to other water insoluble food bioactives. This novel approach may (i) improve the health benefits of water-insoluble bioactives; (ii) enable food manufacturers to add water-insoluble bioactives into low- and high-fat foods to produce health-promoting foods; and (iii) enhance the cost-benefit ratio of water insoluble bioactives.

Supercritical impregnation for food applications: a review of the effect of the operational variables on the active compound loading

The scCO₂-assisted impregnation process has arisen as an effective method to impregnate solid materials. Its multiple advantages include high diffusion, it allows to obtain free-solvent materials and to operate under low temperatures, which permits to process thermolabile solutes. These characteristics have allowed its application at industrial scale for the impregnation of wood with fungicides and in the last years for textile dyeing. Meanwhile, other numerous applications are still being studied at laboratory scale. One potential field of application corresponds to the food-related industry, which includes the use of scCO₂-assisted impregnation process to develop active materials for food packaging and to generate food-grade materials loaded with nutraceuticals for functional food applications. In this framework, this article summarizes the advantages and the main drawbacks with the scCO₂-assisted impregnation process. The effect of the processing variables of the scCO₂-assisted impregnation process is discussed in terms of the incorporation of active compounds within polymer structures. Including the principles and description of the process and a review of the investigated systems for a better understanding.

In Vitro Digestibility of Nanoporous Wheat Starch Aerogels

This study reports the in vitro digestibility of starch aerogels for the first time. The relative crystallinities of the wheat starch aerogels (WSAs) produced at gelatinization temperatures of 120 °C (WSA-120C), 130 °C (WSA-130C), and 120 °C with the addition of sodium metaphosphate (STMP) (WSA-STMP) and xerogel were similar. However, WSA-120C showed the highest amylose-lipid complex content. The addition of STMP created some cross-linked starch with a phosphorus content of 0.023%. Resistant starch (RS) contents of WSA-STMP (33.5%) and xerogel (26.9%) were higher than the other samples when they were uncooked prior to digestion. Nevertheless, the RS contents of WSA-STMP and xerogel decreased drastically with cooking. RS contents of WSA-120C and WSA-130C were stable with cooking and provided 4.5- and 3.0-fold increases in the RS content, respectively. WSA is a promising functional food ingredient with a high RS content, even after cooking.