Optimization of microcapsules shell structure to preserve labile compounds: A comparison between microfluidics and conventional homogenization method

Finger pump microfluidic detection system for methylparaben detection in foods

A novel assay platform consisting of a finger pump microchip (FPM) and a WiFi-based analytical detection platform is presented for measuring the concentration of methylparaben (MP) in commercial foods. In the presented approach, a low quantity (5 μL) of distilled food sample is dripped onto the FPM and undergoes a modified Fenton reaction at a temperature of 40 °C to form a green-colored complex. The MP concentration is then determined by measuring the color intensity (RGB) of the reaction complex using APP software (self-written) installed on a smartphone. The color intensity Red(R) + Green(G) value of the reaction complex is found to be linearly related (R² = 0.9944) to the MP concentration for standard samples with different MP concentrations ranging from 100 to 3000 ppm. The proposed method is used to detect the MP concentrations of 12 real-world commercial foods. The MP concentrations measurements are found to deviate by no more than 5.88% from the results obtained using a conventional benchtop method. The presented platform thus offers a feasible and low-cost alternative to existing macroscale techniques for measuring the MP concentration in commercial foods.

Iron from Co-Encapsulation of Defatted Nannochloropsis Oceanica with Inulin Is Highly Bioavailable and Does Not Impact Wheat Flour Shelf Life or Sensorial Attributes

Defatted green microalgae Nannochloropsis oceanica (DGM) is a rich source of bioavailable iron. However, its use in foods results in unacceptable color and taste development. Therefore, the purpose of this study was to investigate strategies to enhance the use of DGM in foods. DGM and inulin were encapsulated (EC) in an oil-in-water emulsion using high-pressure homogenization. To confirm iron bioavailability, C57BL/6 mice were fed an iron-deficient diet (ID) for 2 weeks. The mice were then fed one of the four diets: ID, ID + DGM (DGM), ID + EC (EC50 or EC100) for 4 weeks. To test the stability of DGM as an iron fortificant at two different fortification rates of 17.5 mg Fe/kg (50%) or 35 mg Fe/kg (100%), whole (DGM50/DGM100), encapsulated (EC50/EC100) and color-masked (CM50/CM100) DGM were added to wheat flour (WF) at two different temperatures: 20 °C and 45 °C and were examined for 30 days. Acceptability studies were conducted to determine sensory differences between rotis (Indian flat bread) prepared from WF/EC50/CM50/EC100. The mice consuming EC50/EC100 diets showed comparable iron status to DGM-fed mice, suggesting that encapsulation did not negatively impact iron bioavailability. Addition of EC to wheat flour resulted in the lowest Fe²⁺ oxidation and color change amongst treatments, when stored for 30 days. There were no differences in the overall liking and product acceptance of rotis amongst treatments at both day 0 and day 21 samples. Our results suggest that EC50 can be effectively used as an iron fortificant in WF to deliver highly bioavailable iron without experiencing any stability or sensory defects, at least until 30 days of storage.

Recent Trends of Microfluidics in Food Science and Technology: Fabrications and Applications

The development of novel materials with microstructures is now a trend in food science and technology. These microscale materials may be applied across all steps in food manufacturing, from raw materials to the final food products, as well as in the packaging, transport, and storage processes. Microfluidics is an advanced technology for controlling fluids in a microscale channel (1~100 μm), which integrates engineering, physics, chemistry, nanotechnology, etc. This technology allows unit operations to occur in devices that are closer in size to the expected structural elements. Therefore, microfluidics is considered a promising technology to develop micro/nanostructures for delivery purposes to improve the quality and safety of foods. This review concentrates on the recent developments of microfluidic systems and their novel applications in food science and technology, including microfibers/films via microfluidic spinning technology for food packaging, droplet microfluidics for food micro-/nanoemulsifications and encapsulations, etc.

Trends in "green" and novel methods of pectin modification - A review

Modification of hydrocolloids to alter their functional properties using chemical methods is well documented in the literature. There has been a recent trend of adopting eco-friendly and "green" methods for modification. Pectin, being a very important hydrocolloid finds its use in various food applications due to its gelling, emulsifying, and stabilizing properties. The adoption of various "green" methods can alter the properties of pectin and make it more suitable for incorporation in food products. The novel approaches such as microwave and pulsed electric field can also be utilized for solvent-free modification, making it desirable from the perspective of sustainability, as it reduces the consumption of organic chemicals. Pectic oligosaccharides (POSs) produced via novel approaches are being explored for their biological properties and incorporation in various functional foods. The review can help to set the perspective of potential scale-up and adoption by the food industry for modification of pectin.

Fabrication of zein-modified starch nanoparticle complexes via microfluidic chip and encapsulation of nisin

A microfluidic chip is a micro-reactor that precisely manipulates and controls fluids. Zein is a group of prolamines extracted from corn that can form self-assembled nanoparticles in water or a low concentration of ethanol in a microfluidic chip. However, the zein nanoparticles have stability issues, especially in a neutral pH environment due to the proximity of the isoelectric point. This study was designed 1) to evaluate the effect of octenyl succinic anhydride (OSA) modified starch on the stability of zein nanoparticles formed using a microfluidic chip and 2) to apply the zein-OSA starch for encapsulation of nisin and evaluate its anti-microbial activity in a model food matrix. A T-junction configuration of the microfluidic chip was used to fabricate the zein nanoparticles using 1% or 2% zein solution and 0–10% (w/w) of OSA starch solution. The stability of the nanoparticles in various ionic strength environments was assessed. Encapsulation efficiency and anti-microbial activity of nisin in the zein nanoparticles against Listeria monocytogenes in a fresh cheese were measured. As the concentration of OSA starch increased from 0 to 10%, effective diameter increased from 117.8 ± 14.5 to 198.7 ± 13.9 nm without affecting polydispersity indexes and zeta-potential changed toward that of the modified starch indicating the zein surface coverage by the OSA starch. The zein-OSA starch nanoparticle complexes were more stable at various sodium chloride concentrations than the zein nanoparticles without OSA starch. The encapsulation efficiency of nisin was positively correlated with the OSA starch concentration. The anti-microbial activity of nisin in the fresh cheese also increased until 3-days of storage as the concentration of the OSA starch increased, which presented both a potential and challenge toward applications.

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Microfluidic chip formed zein nanoparticles with OSA-modified starch.

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Zein nanoparticle size and stability were affected by zein and modified starch concentration.

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Nisin was encapsulated in the zein nanoparticles via microfluidic chip.

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Anti-microbial activity of nisin was improved by the encapsulation.

Preparation and Characterization of Pendimethalin Microcapsules Based on Microfluidic Technology

Microencapsulation of pesticides is a promising attempt to reduce environmental pollution and prevent the active ingredients from the interference of external factors. In this paper, pendimethalin microcapsules were prepared by the interfacial polymerization of 4,4-methylenediphenyl diisocyanate (MDI) and ethylenediamine (EDA) based on microfluidic technology. Effects of the microchannel structure, reaction temperature, surfactant type, and fluid flow rates were investigated and evaluated. The results showed that pendimethalin microcapsules prepared under suitable conditions had a smooth surface, good monodispersity, a high encapsulation efficiency (96.7%), and excellent thermal stability. The size and morphology control of microcapsules were realized by adjusting the flow rates of the continuous phase and the hydrophilic monomer EDA aqueous solution. The release of pendimethalin had a sustained release characteristic that was closely related to the morphology of microcapsules. Compared with the pendimethalin emulsifiable concentrate, pendimethalin microcapsules exhibited outstanding herbicidal activity in the weed control experiments. Therefore, pendimethalin microcapsules with tunable properties were successfully obtained from the microfluidic device and showed great potential in agricultural applications.

Microfluidic Assembly: An Innovative Tool for the Encapsulation, Protection, and Controlled Release of Nutraceuticals

Nutraceuticals have been gradually accepted as food ingredients that can offer health benefits and provide protection against several diseases. It is widely accepted due to potential nutritional benefits, safety, and therapeutic effects. Most nutraceuticals are vulnerable to the changes in the external environment, which leads to poor physical and chemical stability and absorption. Several researchers have designed various encapsulation technologies to promote the use of nutraceuticals. Microfluidic technology is an emerging approach which can be used for nutraceutical delivery with precise control. The delivery systems using microfluidic technology have obtained much interest in recent years. In this review article, we have summarized the recently introduced nutraceutical delivery platforms including emulsions, liposomes, microspheres, microgels, and polymer nanoparticles based on microfluidic techniques. Emphasis has been made to discuss the advantages, preparations, characterizations, and applications of nutraceutical delivery systems. Finally, the challenges, several up-scaling methods, and future expectations are discussed.

Recent advances in microfluidic-aided chitosan-based multifunctional materials for biomedical applications

Chitosan-based biomaterials has shown great advantages in a broad range of applications, including drug delivery, clinical diagnosis, cell culture and tissue engineering. However, due to the lack of control over the fabrication processes by conventional techniques, the wide application of chitosan-based biomaterials has been hampered. Recently, microfluidics has been demonstrated as one of the most promising platforms to fabricate high-performance chitosan-based multifunctional materials with monodisperse size distribution and accurately controlled morphology and microstructures, which show great promising for biomedical applications. Here, we review recent progress of the fabrication of chitosan-based biomaterials with different structures and integrated functions by microfluidic technology. A comprehensive and in-depth depiction of critical microfluidic formation mechanism and process of various chitosan-based materials are first interpreted, with particular descriptions about the microfluidic-mediated control over the morphology and microstructures. Afterwards, recently emerging representative applications of chitosan-based multifunctional materials in various fields, are systematically summarized. Finally, the conclusions and perspectives on further advancing the microfluidic-aided chitosan-based multifunctional materials toward potential and versatile development for fundamental researches and biomedicine are proposed.

Microfluidic colorimetric analysis system for sodium benzoate detection in foods

Sodium benzoate (SBA) is a widely-used additive for preventing food spoilage and deterioration and extending the shelf life. However, the concentration of SBA must be controlled under safe regulations to avoid damaging human health. Accordingly, this study proposes a microfluidic colorimetric analysis (MCA) system composing of a wax-printed paper-microchip and a self-made smart analysis equipment for the concentration detection of SBA in common foods and beverages. In the presented method, the distilled SBA sample is mixed with NaOH to obtain a nitro compound and the compound is then dripped onto the reaction area of the paper-microchip, which is embedded with two layers of reagents (namely acetophenone and acetone). The paper-microchip is heated at 120 °C for 20 min to cause a colorimetric reaction and the reaction image is then obtained through a CMOS (complementary metal oxide semiconductor) device and transmitted to a cell-phone over a WiFi connection. Finally, use the self-developed RGB analysis software installed on the cell-phone to obtain the SBA concentration. A calibration curve is constructed using SBA samples with known concentrations ranging from 50 ppm (0.35 mM) to 5000 ppm (35 mM). It is shown that the R + G + B value (Y) of the reaction image and SBA concentration (X) are related via Y = -0.034 X +737.40, with a determination coefficient of R² = 0.9970. By measuring the SBA concentration of 15 commercially available food and beverage products, the actual feasibility of the current MCA system can be demonstrated. The results show that the difference from the measurement results obtained using the macroscale HPLC method does not exceed 6.0%. Overall, the current system provides a reliable and low-cost technique for quantifying the SBA concentration in food and drink products.

Reducing carotenoid loss during storage by co-encapsulation of pequi and buriti oils in oil-in-water emulsions followed by freeze-drying: Use of heated and unheated whey protein isolates as emulsifiers

Buriti and pequi oils are rich in carotenoids and beneficial to human health; however, carotenoid oxidation during storage causes color loss in foods, making it difficult to use these oils in food products. This research aimed to encapsulate pequi oil and co-encapsulate pequi and buriti oils by emulsification using whey protein isolate (WPI) as an emulsifier in two forms, natural (unheated) and heated, followed by freeze-drying. The emulsions were studied by droplet size under different stress conditions, instability index, and rheology. The freeze-dried (FD) samples were studied after accelerated oxidation and the total carotenoid retention was determined; for the reconstituted FD, the zeta potential and droplet size were recorded after storage at 37 °C for 30 days. The emulsions were stable in all conditions, with average droplet sizes between 0.88 ± 0.03 and 2.33 ± 0.02 μm, and formulations with heated WPI presented the lowest instability index values. The FD's zeta potential values ranged from -50 ± 3 to -32 ± 3 mV. The co-encapsulated oils presented higher carotenoid retention (50 ± 1 and 48 ± 1%) than the free oils (31 ± 2%) after 30 days. The oxidative stability indexes were 51 ± 4 and 46 ± 3 for the co-encapsulated oils with unheated and heated WPI, respectively, and 20.5 ± 0.1 h for the free oils. FD formulations with 1:3 ratio of oil: aqueous phase and heated or unheated WPI showed the best carotenoid retention and oxidative stability, indicating that FD oil emulsions have potential as next-generation bioactive compound carriers.

Controllable preparation of monodisperse alginate microcapsules with oil cores

Here we report a novel strategy for controllable preparation monodisperse alginate microcapsules with oil cores, where the thickness of the alginate shells, as well as the number and diversity of the oil cores can be tailored precisely. Monodisperse oil-in-water-in-oil (O/W/O) emulsions are generated in a microfluidic device as templates, which contain alginate molecules and a water-soluble calcium complex in the middle aqueous phase. Alginate microcapsules are produced by gelling O/W/O emulsions in oil solution with acetic acid, where the pH decreasing will trigger the calcium ions being released from calcium complex and cross-linking with alginate molecules. Increasing the alginate molecule concentration in emulsion templates affects little on the thickness of the microcapsules but improves their stability in DI water. The strength of alginate microcapsules can be reinforced by post cross-linking in calcium chloride, polyetherimide, or chitosan solution. Typical payloads, such as thyme essential oil, lavender essential oil and W/O emulsions are encapsulated in alginate microcapsules successfully. Furthermore, tailoring the thickness of the alginate shells, as well as the number and the diversity of the oil cores precisely by manipulation the emulsion templates with microfluidics is also demonstrated. The proposed method shows excellent controllability in designing alginate microcapsules with oil cores.

l-Histidine Crystals as Efficient Vehicles to Deliver Hydrophobic Molecules

l-Histidine (l-His) molecules can form highly ordered fluorescent crystals with tunable size and geometry. The polymorph A crystal of l-His contains hydrophobic domains within the structure's interior. Here, we demonstrate that these hydrophobic domains can serve as vehicles for highly efficient entrapment and transport of hydrophobic small molecules. This strategy shows the ability of l-His crystals to mask the hydrophobicity of various small molecules, helping to address issues related to their poor solubility and low bioavailability. Furthermore, we demonstrate that we can modify the surface of these crystals to define their function, suggesting the significance of l-His crystals in designing site-specific and bioresponsive platforms. As a demonstration, we use l-His crystals with loaded doxorubicin, featuring hyaluronic acid covalently bonded on the crystal surface, controlling its release in response to hyaluronidase. This strategy for entrapment of hydrophobic small molecules suggests the potential of l-His crystals for targeted drug-delivery applications.

Microfluidic Systems for Droplet Generation in Aqueous Continuous Phases: A Focus Review

Microfluidics is one of the most fascinating fields that researchers have been trying to apply in a large number of scientific disciplines over the past two decades. Among them, the discipline of food and pharmaceutical formulation encountered several obstacles when combining microfluidics with aqueous media. Indeed, the physical properties of liquids at micrometric volumes being particular, the droplet generation within microfluidic devices is a big challenge to be met. This focus review is intended to be an initiation for those who would like to generate microdroplets in microfluidic systems involving aqueous continuous phases. It provides a state-of-the-art look at such systems while focusing on the microfluidic devices used, their applications to form a wide variety of emulsions and particles, and the key role held by the interface between the device channels and the emulsion. This review also leads to reflections on new materials that can be used in microfluidic systems with aqueous continuous phases.

Photo-Cross-Linked Poly(ethylene glycol) Diacrylate Hydrogels: Spherical Microparticles to Bow Tie-Shaped Microfibers

Bow tie-shaped fibers and spherical microparticles with controlled dimensions and shapes were fabricated with poly(ethylene glycol) diacrylate hydrogel utilizing hydrodynamic shear principles and a photopolymerization strategy under a microfluidic regime. Decreasing the flow rate ratio between the core and sheath fluids from 25 (50:2) to 1.25 (100:80) resulted in increasing the particles size and reducing the production rate by 357 and 86%, respectively. The width of the fibers increased by a factor of 1.4 when the flow rate ratio was reduced from 2.5 to 1 due to the decrease of the shear force at the fluid/fluid interface. The stress at break and Young's modulus of the fibers were enhanced by 32 and 63%, respectively, when the sheath-to-core flow rate ratio decreased from 100:40 to 100:80. The fiber fabrication was simulated using the finite element method, and the numerical and experimental results were in agreement. Adult hippocampal stem/progenitor cells and bone-marrow-derived multipotent mesenchymal stromal cells were seeded onto the fibrous scaffolds in vitro, and cellular adhesion, proliferation, and differentiation were investigated. Microgrooves on the fibers' surface were shown to positively affect cell adhesion when compared to flat fibers and planar controls.

Controlling the Release from Enzyme-Responsive Microcapsules with a Smart Natural Shell

We design a natural and simple core-shell-structured microcapsule, which releases its cargo only when exposed to lipase. The cargo is entrapped inside a gel matrix, which is surrounded by a double-layer shell containing an inner solid lipid layer and an outer polymer layer. This outer polymer layer can be designed according to the intended biological system and is responsible for protecting the microcapsule architecture and transporting the cargo to the desired site of action. The lipid layer contains natural ester bonds, which are digested by lipase, controlling the release of cargo from the microcapsule core. To demonstrate the feasibility of this approach, our model system includes a colorant bixin entrapped inside a κ-carrageenan gel matrix. This core is surrounded by an inner beeswax-palmitic acid layer and an outer casein-poloxamer 338 layer. These fabricated microcapsules are then applied into Cheddar cheese, where they selectively color the cheese matrix.

Enhancing the physicochemical stability of β-carotene solid lipid nanoparticle (SLNP) using whey protein isolate

β-Carotene is a nutraceutical that acts as a coloring agent and as pro-vitamin A, but its incorporation into foods is limited because of its hydrophobicity and low chemical stability. The aim of this study was to improve the physicochemical stability of β-carotene by encapsulating into solid lipid nanoparticles (SLNPs) containing palmitic acid and corn oil, stabilized using whey protein isolate (WPI). The palmitic acid crystals covered the surface of the oil droplets and formed a solid shell to protect the encapsulated β-carotene. Corn oil decreased the exclusion of β-carotene from the solid lipid matrix to the surface of SLNPs. WPI increased the colloidal stability of the system, and improved β-carotene oxidative stability. The rate of color fading due to β-carotene degradation increased with increasing temperature and was faster at lower pH. Lower ionic strengths had a slight impact on β-carotene degradation, while higher ionic strengths accelerated β-carotene breakdown.