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Summary
Food components, such as starch and other biopolymers and macromolecules (proteins), are being used in the food industry as thickeners, gelling agents, or emulsifiers in a variety of products. Plant-based proteins with high functionality with respect to the stabilization of multiphase systems are needed. There are many existing modification methods used to modulate plant proteins, which generally use harsh fractionation conditions, such as the use of water, corrosive chemicals or high physical stresses. This project will aim to investigate dry fractionation via milling and air classification as a milder and more sustainable processes in which protein functionality can be retained. The fractions will then be processed via electrospraying to produce particles of 200-1000 nm range . Electrospraying, is an emerging technology used to produce dried particles and shows great advantages over conventional spraying systems because it does not require heat and therefore consumes less energy.
Background
Food components, such as starch and other biopolymers and macromolecules (proteins), are being used in the food industry as thickeners, gelling agents, or emulsifiers in a variety of products, including sauces, dressings, and ice-creams. The texture and stability of these products depend on the structure and function relationship of the added ingredients.
The use of a wide range of plant protein sources in food formulation has raised a remarkable attention during the last decade. It is now clearly advocated that rebalancing diets by increasing the proportion of plant-based proteins, in so-called flexitarian diets, will be among the only options to achieve a sustainable global food system, combined with a substantial reduction of food waste. Some of the challenges faced in using plant proteins as emulsifiers or food ingredients result from the techniques used to isolate plant proteins from raw material (e.g. peas or pea flour) compared to those used to isolate animal proteins that affect the techno-functional properties such as solubility, texture and mouthfeel. Many plant proteins have poor solubility in water.
Plant-based proteins with high functionality with respect to the stabilization of multiphase systems, such as foams and emulsions are needed. There are many existing modification methods used to modulate plant proteins. Most of the extraction methods generally use harsh fractionation conditions, such as the use of water, corrosive chemicals or high physical stresses. During the extraction process, the protein fractions are separated from the plant cell’s oil, fibre or starch components employing wet treatment depending on the initial raw material properties. Wet decantation and isoelectric precipitation are used for oilseeds or membrane proteins extracted from green leaves, which leads to relatively pure protein isolate. The current generation of meat alternatives are produced from protein-rich ingredients obtained from such extraction procedures.
Aims and objectives
This project will aim to investigate dry fractionation via milling and air classification as a milder and more sustainable processes in which protein functionality can be retained. This involves the fine milling of the grains during which starch fragments are released from a protein matrix that break up into small fragments. This step follows an air classification process, during which the protein fragments are separated by the starch granules on the basis on their size. A protein concentrate is then obtained with 50 g protein/100 g of dry matter and a starch concentrate is obtained with up to 67 g starch/100 g of dry matter. It is hypothesized that both these fractions' recovery, characterization, and gleaned understanding of the structure-fucntion relationships will underpin future applications and a more sustainable food production.
The fractions will then be processed via electrospraying to produce particles of 200-1000 nm range. Electrospraying, is an emerging technology used to produce dried particles and shows great advantages over conventional spraying systems because it does not require heat and therefore consumes less energy. An electrical potential is created between the polymer solution or emulsion and a grounded collector, leading to a spray of particles. The particle sizes produced are much smaller than via other techniques, down to the nano-scale and with a more narrow size distribution (i.e., less aggregated) facilitating their solubility and functional properties.
This PhD project will seek to develop this low carbon footprint fractionation process for legumes such as pea, fava bean, and lentil. The composition (fibre, protein and starch) of the produced fractions will be determined using a range of multi-scale techniques. Differential scanning calorimetry (DSC) will be used to measure the protein denaturation temperature and the starch gelatinization temperature for the grains, legumes, flour and the present fractions. Asymmetric flow field flow fractionation (AF4) with multidetection (DRI, MALS, UV-VIS) will enable to characterize the molecular weight distribution of the protein and polysaccharide fractions. The viscoelastic properties of the fractions in solution will be measured using small deformation rheology and the contact angle and interfacial tension will be measured by a tensiometer. Other biophysical properties, including size, structure, solubility, and zeta-potential, will be evaluated. For the first time, small angle X-ray scattering (SAXS) will be used to investigate the internal nanostructure and crystallinity of starch and proteins of the the ocurring fractions. The morphology of the obtained particles will be probed by microscopy (optical, scanning electron microscope) will be used, while their chemical structure will be characterized using Fourier-transform infrared spectroscopy (FT-IR), while their functional properties will be compared with the conventional powders.
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