Innovative Technologies for Extraction and Microencapsulation of Bioactives from Plant-Based Food Waste and Their Applications in Functional Food Development

Abstract

The by-products generated from the processing of fruits and vegetables (F&V) largely are underutilized and discarded as organic waste. These organic wastes that include seeds, pulp, skin, rinds, etc., are potential sources of bioactive compounds that have health imparting benefits. The recovery of bioactive compounds from agro-waste by recycling them to generate functional food products is of increasing interest. However, the sensitivity of these compounds to external factors restricts their utility and bioavailability. In this regard, the current review analyses various emerging technologies for the extraction of bioactives from organic wastes. The review mainly aims to discuss the basic principle of extraction for extraction techniques viz. supercritical fluid extraction, subcritical water extraction, ultrasonic-assisted extraction, microwave-assisted extraction, and pulsed electric field extraction. It provides insights into the strengths of microencapsulation techniques adopted for protecting sensitive compounds. Additionally, it outlines the possible functional food products that could be developed by utilizing components of agricultural by-products. The valorization of wastes can be an effective driver for accomplishing food security goals.

Anthocyanins Recovered from Agri-Food By-Products Using Innovative Processes: Trends, Challenges, and Perspectives for Their Application in Food Systems

“…When the electric field strength exceeds a certain critical limit (E c ), usually around 0.2–1 V/m for plant cells, the elastic properties of the cell membrane does not resist the electrostatic attraction that leads to reversible (E ≈ E c ) or irreversible (E >> E c ) formation of micropores in weaker areas of the cell membrane, increasing cell permeability. Thereby, PEF treatment enhances the migration of target compounds located in the cytoplasm across the cell membrane, which boosts mass transfer and, consequently, increases the extraction rates and yield [ 108 , 109 ].…”

“…Furthermore, the critical electric field strength required to promote electroporation in cell membranes can differ for each agri-food by-product. As discussed previously, the closer the electric field strength values to the critical value (E c ), the greater the extent of the electroporation phenomenon and, consequently, higher compounds release into the extraction medium [ 108 , 109 ]. However, when the electric field strength values overcome the critical value (E c ), the excess energy can promote structural changes and/or degradation of organic molecules [ 100 ].…”

“…Microwave (MW) is another innovative and green extraction technology considered to be more advantageous than conventional extraction technologies due to its high extraction rate, less use of solvents, and shorter extraction time [ 109 ]. Anthocyanins from different plant sources have been successfully extracted by using MW technology [ 116 , 117 , 118 , 119 , 120 ].…”

“…Thus, cell rupture is needed to boost anthocyanin extraction from plant matrices. When microwave irradiation is applied to a matrix or extraction medium, microwave energy is absorbed by polar compounds causing ion conduction and dipole rotation [ 109 ]. In ionic conduction, the electric field produced by the microwaves induces electrophoretic migration of charge carriers (e.g., ions and electrons), generating friction between the moving ions and the medium that causes heating.…”

“…In plant matrices, the water naturally present inside their structure selectively absorbs the microwave energy favoring localized heating above or near the boiling point of water. This internal overheating causes the expansion and rupture of cell structures (especially cell walls and cell membranes) by disrupting the dipole attractions, hydrogen bonds, and van der Waals forces, which facilitates the release of target compounds bound to the matrix and solvent penetration into the plant materials, resulting in the improved mass transfer of these compounds into the extraction medium [ 17 , 109 ]. Moreover, MW-induced temperature rise modifies the solvent properties, reducing its viscosity and surface tension while increasing its diffusivity and molecular mobility, improving the mass transfer rates [ 19 ].…”