Microfluidic paper-based device coupled with 3D printed imaging box for colorimetric detection in resource-limited settings.

Rapid and effective methods for the detection of analytes such as water contaminants, food adulterants and biomolecules are essential for the protection of public health and environmental protection. Most of the currently established analytical techniques need sophisticated equipment, centralized testing facilities, costly operations, and trained personnel. Such limitations make them inaccessible to the general populace, particularly in regions with limited resources. The emergence of microfluidic devices offers a promising alternative to overcome several such constraints. This work describes a protocol for fabricating a low-cost, open-source paper-based microfluidic device using easily available tools and materials for colorimetric detection of analytes. The ease and simplicity of fabrication allow users to design customized devices. The device is coupled with an imaging box assembled from 3D printed parts to maintain uniform lighting conditions during analytical testing. The platform allows digital imaging using smartphones or cameras to instantaneously capture images of reaction zones on the device for quantitative analysis. The system is demonstrated for detecting hexavalent chromium, a toxic water contaminant. The image analysis is performed using open-source ImageJ for quantification of results. The approach demonstrated in this work can be readily adopted for a wide range of sensing applications.

Extraction techniques in food industry: Insights into process parameters and their optimization.

This review presents critical evaluation of the key parameters that affect the extraction of targeted components, giving due consideration to safety and environmental aspects. The crucial aspects of the extraction technologies along with protocols and process parameters for designing unit operations have been emphasized. The parameters like solvent usage, substrate type, concentration, particle size, temperature, quality and storage of extract as well as stability of extraction have been elaborately discussed. The process optimization using mathematical and computational modeling highlighting information and communication technologies have been given importance aiming for a green and sustainable industry level scaleup. The findings indicate that the extraction processes vary significantly depending on the category of food and its structure. There is no single extraction method or universal set of process conditions identified for extracting all value-added products from respective sources. A comprehensive understanding of process parameters and their optimization as well as synergistic combination of multiple extraction processes can aid in enhancement of the overall extraction efficiency. Future efforts must be directed toward the design of integrated unit operations that cause minimal harm to the environment along with investigations on economic feasibility to ensure sustainable extraction systems.

Paper-based microfluidic colorimetric sensor on a 3D printed support for quantitative detection of nitrite in aquatic environments.

To ensure safe drinking water, it is necessary to have a simple method by which the probable pollutants are detected at the point of distribution. Nitrite contamination in water near agricultural locations could be an environmental concern due to its deleterious effects on the human population. The development of a frugal paper-based microfluidic sensor could be desirable to achieve the societal objective of providing safe drinking water. This work describes the development of a facile and cost-effective microfluidic paper-based sensor for quantitative estimation of nitrite in aquatic environments. A simple punching machine was used for fabrication and rapid prototyping of paper-based sensors without the need of any specialized equipment or patterning techniques. A reusable 3D printed platform served as the support for simultaneous testing of multiple samples. The nitrite estimation was carried out with smartphone-assisted digital image acquisition and colorimetric analysis. Under optimized experimental conditions, the variation in average grayscale intensity with concentration of nitrite was linear in the range from 0.1 to 10 ppm. The limits of detection and quantitation were 0.12 ppm and 0.35 ppm respectively. The reproducibility, expressed as relative standard deviation was 1.31%. The selectivity of nitrite detection method was determined by performing interference studies with commonly existing co-ions in water, such as bicarbonates, chloride and sulphate. The paper-based sensor was successfully applied for estimation of nitrite in actual water samples and showed high recoveries in the range of 83.5-109%. The results were in good agreement with those obtained using spectrophotometry. The developed paper-based sensor method, by virtue of its simplicity, ease of fabrication and use, could be readily extended for detection of multiple analytes in resource-limited settings.

Lab-on-a-chip technologies for food safety, processing, and packaging applications: a review.

The advent of microfluidic systems has led to significant developments in lab-on-a-chip devices integrating several functions onto a single platform. Over the years, these miniature devices have become a promising tool for faster analytical testing, displaying high precision and efficiency. Nonetheless, most microfluidic systems are not commercially available. Research is actually undergoing on the application of these devices in environmental, food, biomedical, and healthcare industries. The lab-on-a-chip industry is predicted to grow annually by 20%. Here, we review the use of lab-on-a-chip devices in the food sector. We present fabrication technologies and materials to developing lab-on-a-chip devices. We compare electrochemical, optical, colorimetric, chemiluminescence and biological methods for the detection of pathogens and microorganisms. We emphasize emulsion processing, food formulation, nutraceutical development due to their promising characteristics. Last, smart packaging technologies like radio frequency identification and indicators are highlighted because they allow better product identification and traceability.

Valorization of food waste as adsorbents for toxic dye removal from contaminated waters: A review.

Industrial contaminants such as dyes and intermediates are released into water bodies, making the water unfit for human use. At the same time large amounts of food wastes accumulate near the work places, residential complexes etc. polluting the air due to putrefaction. The need of the hour lies in finding innovative solutions for dye removal from wastewater streams. In this context, the article emphasizes adoption or conversion of food waste materials, an ecological nuisance, as adsorbents for the removal of dyes from wastewaters. Adsorption, being a well-established technique, the review critically examines the specific potential of food waste constituents as dye adsorbents. The efficacy of food waste-based adsorbents is examined, besides addressing the possible adsorption mechanisms and the factors affecting phenomenon such as pH, temperature, contact time, adsorbent dosage, particle size, and ionic strength. Integration of information and communication technology approaches with adsorption isotherms and kinetic models are emphasized to bring out their role in improving overall modeling performance. Additionally, the reusability of adsorbents has been highlighted for effective substrate utilization. The review makes an attempt to stress the valorization of food waste materials to remove dyes from contaminated waters thereby ensuring long-term sustainability.

Eco-friendly pH detecting paper-based analytical device: Towards process intensification.

This work describes the development of a miniaturized paper-based pH detection platform using natural dye extracted from red cabbage (Brassica oleracea). The easily available paper was used as a substrate and the requisite patterned zone was created with the aid of a punching machine. Experimental parameters were optimized to obtain the best signal readout. The performance of the device at different pH values was quantitatively assessed using digital image analysis with various color space models. Regression analysis suggested that a∗ parameter in CIEL∗a∗b∗ color space model, which captures the variations on the red-green scale, exhibited the best fit with experimental data (R2 = 0.9754). This parameter was used for the quantitative estimation of pH variations in a wide range of pH (1-12). A series of real test samples were examined using the paper-based device and results validated with a standard pH meter. The use of paper and natural dye makes the device eco-friendly. The simplicity of fabrication, ease of usage and low reagent and sample volume requirements render the methodology suitable for in situ measurements of pH. The approach demonstrated here would pave the way for the development of clean, sustainable and intensified chemical sensor technologies.

Techniques and modeling of polyphenol extraction from food: a review.

There is a growing demand for vegetal food having health benefits such as improving the immune system. This is due in particular to the presence of polyphenols present in small amounts in many fruits, vegetables and functional foods. Extracting polyphenols is challenging because extraction techniques should not alter food quality. Here, we review technologies for extracting polyphenolic compounds from foods. Conventional techniques include percolation, decoction, heat reflux extraction, Soxhlet extraction and maceration, whereas advanced techniques are ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, high-voltage electric discharge, pulse electric field extraction and enzyme-assisted extraction. Advanced techniques are 32-36% more efficient with approximately 15 times less energy consumption and producing higher-quality extracts. Membrane separation and encapsulation appear promising to improve the sustainability of separating polyphenolic compounds. We present kinetic models and their influence on process parameters such as solvent type, solid and solvent ratio, temperature and particle size.

Food preservation techniques and nanotechnology for increased shelf life of fruits, vegetables, beverages and spices: a review.

Food wastage is a major issue impacting public health, the environment and the economy in the context of rising population and decreasing natural resources. Wastage occurs at all stages from harvesting to the consumer, calling for advanced techniques of food preservation. Wastage is mainly due to presence of moisture and microbial organisms present in food. Microbes can be killed or deactivated, and cross-contamination by microbes such as the coronavirus disease 2019 (COVID-19) should be avoided. Moisture removal may not be feasible in all cases. Preservation methods include thermal, electrical, chemical and radiation techniques. Here, we review the advanced food preservation techniques, with focus on fruits, vegetables, beverages and spices. We emphasize electrothermal, freezing and pulse electric field methods because they allow both pathogen reduction and improvement of nutritional and physicochemical properties. Ultrasound technology and ozone treatment are suitable to preserve heat sensitive foods. Finally, nanotechnology in food preservation is discussed.

Optimization, equilibrium, kinetic and thermodynamic studies on adsorptive remediation of phenol onto natural guava leaf powder.

Environmental considerations require disposal of the contaminants in a safe manner without causing any harm. Accordingly, the contaminants should be removed and recovered as value or disposed without any burden to the environment. In this context, natural biodegradable adsorbents could possibly be an answer as they get biodegraded along with the organic contaminants including phenol. Having observed from literature that the natural guava leaf powder (NGLP) can be used as an adsorbent, experimental studies were carried out to investigate the potential of NGLP to remove phenol from aqueous solutions. Batch experiments were carried out using NGLP and the effect of different variables such as pH, NGLP dosage, contact time and agitation speed was studied using response surface methodology (RSM) with Box-Behnken approach and the significant parameters were optimized by subsequent experimentation. The optimized parameters obtained in our studies correspond to pH 5.85 for a NGLP dosage of 2.15 g/L, at an agitation speed of 140 rpm and a contact time of 9 h for the initial phenol concentrations ranging from 50 to 250 mg/L. The absorption of phenol onto NGLP was confirmed using FTIR and SEM-EDX. Thermodynamic, kinetic and equilibrium isotherm studies were conducted using the optimal parameters. The adsorption data fitted well with Langmuir isotherm (R2= 0.9982) for the batch equilibrium studies and the pseudo-second-order type model (R2= 0.9743-0.9921) depicted the phenol adsorption kinetics. The maximum adsorption capacity of NGLP for phenol was 10.85 mg/g. The results inferred the feasibility of using NGLP as a phenol adsorbent and Box-Behnken design as an effective tool for the optimization of process conditions. Even though the studies are not intended to reuse the adsorbent in view of abundance and biodegradability, the preliminary experiments have indicated the possible potential of desorption and reusability.