The race to develop plant-based foods has intensified to reduce greenhouse-gas emissions and thus the burden on the environment. However, replicating meat texture with plant material is not easy. Current products are based on purified proteins from soybeans or peas. For meat lovers, plant-based foods are often too soft and not tender enough. Now researchers have provided understanding to unlock the use of less-refined proteins to more closely recreate the texture that gives a meat-like mouthfeel.
Using plant protein in innovative formulation of food products is becoming one of the most popular options to maintain a global food system within its environmental limits. However, this protein is extracted and purified from various plants by a range of resource-intensive processes involving chemicals and considerable water to maximise protein recovery. According to researchers, the raw ingredients must be sustainably produced in truly sustainable plant-based food production.
“If we work with ultra-pure protein – protein isolates – then we are not remedying the problem but creating a new one. So, our philosophy is to work with ‘dirty’ protein fractions: the natural fractions from plants that contain, besides protein, other things such as polysaccharides and minerals. We examined commercial fractions from eight plants to understand the interactions between their components. We found high-performing protein fractions, such as those in pumpkin and mung beans. After being extrusion-cooked, they develop matrices with certain textural attributes similar to some types of meat,” explains Mario Martinez-Martinez, Associate Professor of Food and Food Technology at Aarhus University.
Dry and too easy to chew
According to the researchers, addressing the vast meat consumption is a promising strategy to reduce the environmental burden, at least that related to the food sector. Food production accounts for one quarter of global greenhouse-gas emissions, and meat accounts for nearly 60% of the greenhouse gases from food production.
“Consumers are segmented into categories, and the traditional meat lovers represents the largest category. Making plant-based foods that optimally resemble meat is obviously advisable if we want to make the biggest impact. So that is the plan,” says Mario Martinez-Martinez.
However, replicating the texture of meat with plant proteins is far from easy, and this explains why most meat lovers still find the plant-based foods too soft and not tender enough.
“That means that you do not chew them much before you swallow them, which is far different from meat. They are also a little dry,” explains Mario Martinez-Martinez.
Thus, the texture comprises much of the problem. Many studies have focused on ultrapure proteins or soy and pea protein.
“The results suggest some mechanisms that could support the structuring of foods using less-refined fractions from plants containing a mixture of protein, polysaccharides and minerals. Instead of purifying one protein and then adding other components to test the resulting texture, we instead tested the synergistic effects of the components already present in the one single ingredient we used: the ‘dirty protein’. Using raw extracts is not only cheaper but more environmentally friendly,” says Mario Martinez-Martinez.
Very simple processes and very complex ingredients
The researchers tested commercially available protein fractions from plant sources: pulses such as peas, chickpeas, fava beans and mung beans, cereals such as gluten and rice and oilseeds such as soybeans and pumpkin seeds.
“All samples were analysed for composition and then individually extruded into a thermoplastic mass and investigated for structural synergy such as the molecular properties of the protein, water mobility, ion interactions and also visual appearance and texture,” explains Mario Martinez-Martinez.
Extrusion is far from a new technology. It is actually more than two centuries old and has been used intensively in the plastic industry but also for producing snacks and breakfast cereals.
“The extrusion unfolds the proteins, enabling them to interact, but also the non-proteinaceous components lead some of the interactions occurring in these complex materials that could be main drivers of the food texturisation,” says Mario Martinez-Martinez.
The interactions between components seemed to result in phase separations and complex formation, with polysaccharides and minerals influencing not only the conformation of the proteins but also the structure and texture of the final food product prototypes.
“These processing technologies are very simple, but the raw materials are difficult to study, so we had to resort to a broad set of analytical procedures,” explains Mario Martinez-Martinez.
The experiments showed that especially the fractions from pumpkin and mung beans were promising for closing the tenderness gap between plant-based products and meat. They displayed the highest fibrousness and tenderness and are therefore the most obvious ones to use.
“So, we are trying to get close just by using one ingredient. We are still not as tender as meat, but our latest results indicate that we are moving towards that. We are not discarding the possibility to create new textures that perhaps some other consumers will love, but right now we will focus on the biggest segments – the meat lovers and the flexitarians,” says Mario Martinez-Martinez.
The researchers’ studies focused on cheap materials and cheap and scalable processes, so the food industry should be able to adapt these technologies if they understand the properties of the materials. The producers may not have the same analysis capability as a research laboratory, so the idea is to support them in understanding what is happening in crafting these novel food structures from plant materials.