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Lignin-based ingredients formulated from food waste for sustainable approaches to food safety and a healthy diet

Primary Supervisor: Professor Bettina Wolf, School of Chemical Engineering

Secondary supervisor: Dr Tim Overton

PhD project title: Lignin-based ingredients formulated from food waste for sustainable approaches to food safety and a healthy diet

University of Registration: University of Birmingham

Project outline:

Lignin is the second most abundant polymer after cellulose, found in all vascular plants. Nature has designed lignin as a complex aromatic structure to support plant wall strength and water transport. Industrial lignin occurs as a waste product of the paper and pulp industry and is removed from feedstock for bioenergy processes. The large quantity (~ 100 Mt per annum worldwide2) has triggered research into value added processes and products, alternative to burning as fuel for heat and power. Most relevant to health- and food-related end application, lignin has been shown to be antimicrobial, lignin nanoparticles to provide antioxidant and UV protection (better than bulk lignin), and processes for transformation into phenolic compounds2. However, industrial lignin removal processes involving toxic chemicals and wood as the predominant bioresource not part being part of the food supply chain renders application of value-added lignin as functional ingredients for consumer goods challenging.

Plant-based co-products of the food manufacturing industry represents a source of lignin that is already part of the food supply chain. Applying lignin extraction and conversion processes utilising green solvents will contribute to future application in foods or healthcare products. Possible feedstocks include peanut husk and coconut shell (30-35% lignin), sugar cane bagasse (20-25%), cocoa shell (10-20%) and citrus peel (~5-10%) among others. A solvent system selected for lignin will co-extract other in this solvent soluble feedstock components, such as fatty acids and polyphenols which themselves have beneficial properties including food microstructure stabilisation and antioxidant properties. Therefore, and in line with the idea of contributing to a circular economy and maximising the use of bioresource already within the economic cycle, research in the group of the Primary Supervisor focusses on value-added processing of lignin-rich extracts1. Via precipitation of ethanolic lignin-rich extract solutions into water (a lignin anti-solvent), particulate emulsifiers for oil-in-water emulsion stabilisation can be fabricated utilising simple batch processes and continuous processes such as coaxial jet mixing. With research on the impact of processing parameters and physicochemical material properties (solvent, antisolvent and extract composition) on the microstructure functionality of precipitate particles under way, the overall aim of this PhD project is to exploit antimicrobial and health beneficial properties of co-extracted components in the value-added processing chain of lignin-rich functional food ingredients processed from plant-based food industry co-products.

The research will involve the selection of a most promising feedstock for this research, development of extraction protocols and extract characterisation (composition, antimicrobial properties against representative Gram-positive and -negative bacteria, antioxidative properties), processing into a food ingredient and validation of functionality in representative food microstructure systems such as emulsions.

The PhD student will be trained in all the necessary techniques required including microbiology, solvent extraction, relevant physicochemical material characterisation techniques, imaging of food microstructures and systems as well as their physiochemical properties pertinent to the overall aim of their research.

References:

  1. Cuthill, H.; Elleman, C.; Curwen, T.; Wolf, B., Colloidal particles for Pickering emulsion stabilization prepared via antisolvent precipitation of lignin-rich cocoa shell extract. Foods 2021, 10, 371.
  2. Bajwa, D. S.; Pourhashem, G.; Ullah, A. H.; Bajwa, S. G., A concise review of current lignin production, applications, products and their environmental impact. Industrial Crops and Products 2019, 139, 11.

BBSRC Strategic Research Priority: Sustainable Agriculture and Food: Microbial Food Safety & Renewable Resources and Clean Growth: Industrial Biotechnology & Integrated Understanding of Health: Diet and Health

    Techniques that will be undertaken during the project:

    • Green solvent extraction of biomaterials
    • Spectroscopy methods for compositional analysis
    • Antisolvent precipitation in continuous flow process
    • Batch and continuous emulsion processing
    • Light scattering for particle size
    • Zeta potential for particle and emulsion droplet surface charge
    • Optical, confocal laser scanning and electron microscopy for particle and food microstructure visualisation
    • Rheology and interfacial tension methods
    • Standard microbiology methods for determination of antimicrobial activity (CFU, MIC assays)
    • Flow cytometry and confocal microscopy for non-culture based determination of antimicrobial activity
    • Standardised antioxidant assays

    Contact: Professor Bettina Wolf, University of Birmingham