Illustration created by Elena Bergamasco, a PhD student working on the Immune SEEDstem project.
strand of research, Dr Duque-Estrada has performed fractionation processes on peas in collaboration with project partners; this resulted in two different protein ingredients, which were then compared and analysed. “From dry fractionation, we obtained a protein-enriched fraction, also called a protein concentrate, which still contains some ANFs, together with some starch and fibres. It’s a complex process, but it’s also very sustainable, as we don’t add water or heat,” she explains. The wet fractionation process, commonly used in the food industry, by contrast involves adding water and chemicals to purify the proteins. “Our partners Bioptimate looked into changing the pH and the salt concentration, and in that way modifying the solubility of the proteins. With this method we can remove most of the starch and the fibres,” continues Professor Petersen. “We get a very pure fraction of proteins, also called a protein isolate, with some of the ANFs removed, but we have also used more energy during processing.” The pure protein isolate is often found to have a higher nutritional quality. Both the less pure protein concentrate and the protein isolate may then be processed further before eventually forming part of a product like a beef patty alternative. As part of the project,
Processing the benefits of plant-based foods Plant-based diets are growing increasingly popular, yet plant proteins are less digestible than those from animals, so some processing may be required to improve their nutritional quality. We spoke to Dr Iben Lykke Petersen and Dr Patrícia DuqueEstrada about their research into the extent to which plant-based foods should be processed in the context of the shift towards a more sustainable food supply chain. The agricultural sector is a major contributor to global warming, motivating many people to move to plant-based diets. However, plant proteins are less digestible than those from animals, so some processing may be necessary to improve their nutritional quality. “We need to process sources of plant proteins so that people can properly digest proteins and absorb amino acids and other nutrients,” outlines Dr Patrícia Duque-Estrada, Assistant Professor in the Food Analytics and Biotechnology Section of the Department of Food Science at the University of Copenhagen. This may negate the environmental benefits of plant-based diets to some degree, and it can be difficult to identify the degree of processing that should be applied, a topic Dr Duque-Estrada is exploring in the BEYOND project (Beyond sustainability: a holistic approach to evaluate the nutritional quality of plant protein-based foods). “If we process these plants too much it can lead to some negative effects – maybe we
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don’t absorb the proteins as well any more. It’s also important to consider the impact on sustainability, as if plants are processed more, that’s less sustainable,” she explains. “In the project we are looking at the extent to which we need to process plant-based foods. Can we process them less and still provide proteins with good nutritional quality?”
Beyond sustainability This research is focused specifically on proteins from yellow split peas, which are an important source of protein in a plant-based diet. When plant seeds such as peas are processed or exposed to high temperatures it may lead to certain modifications, such as glycation or protein oxidation, which can affect the nutritional quality of the protein. “After we digest proteins we absorb aminoacids, which are the building blocks of proteins. If we modify these amino-acids to a certain level, we might not be able to use them any more,” says Dr Duque-
Estrada. Naturally occurring substances inside beans and other legumes can also affect digestibility, some of which may be toxic and need to be removed. “We know for example that certain lectins are toxic. This is why we have to soak legumes and boil them for a certain amount of time, to reduce the amount of lectins,” outlines Iben Lykke Petersen, Associate Professor in the Department of Food Science “There are also other compounds that have a negative effect on nutritional quality, at least if they are present in amounts above a certain threshold. They can also react with proteins when plant-based foods are processed at higher temperatures. That can have negative effects on the bioavailability of proteins.” Researchers in the project are considering both the natural substances in plant-based foods that may affect digestibility, antinutritional factors (ANFs) such as protease inhibitors, and also the modifications that can occur as a result of processing. In one
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Immune SEEDstem project Researchers are also looking at protease inhibitors from a different angle in the Immune SEEDstem project, with Professor Petersen and her team aiming to characterise levels of protease inhibitors in several types of legumes from different locations and different growing years. The idea is to characterise these legumes on a fairly basic level and investigate whether levels of protease inhibitors remain consistent or whether they fluctuate according to soil conditions and other factors, then Professor Petersen plans to look at how protease inhibitors complex with proteins as they move through the human digestive system. “The inhibitors probably make complexes with our own digestive enzymes, so that our digestive enzymes cannot digest the proteins that we eat,” she says. While this might seem to suggest that it would be desirable to reduce the level of these protease inhibitors, some research suggests that they can have beneficial effects on the immune system. “One type of these inhibitors – called Bowman-Birk inhibitor – has been shown to have beneficial effects on another type of proteases present in our gut (the matrix metalloproteinases), that have been found to be up-regulated in the pre-states of cancer,” continues Professor Petersen.
“We are looking at the extent to which we need to process plant-based foods. Can we process them less and still provide proteins with good nutritional quality?” Professor Petersen is investigating whether using less pure or more pure protein has an effect on the nutritional value of the end food product. “Proteins are combined with other macronutrients during processing, leading to reactions like the Maillard reaction and protein oxidation. Does using a higher nutritional quality protein make a difference? Or can we just use the less pure ingredient with lower nutritional quality?” she outlines. The aim is to look beyond the nutritional value of individual ingredients, such as the isolates and concentrates, and take a holistic view of a product as a whole. “There are more and more plant-based products on the market, and there are lots of different components inside their matrix,” says Dr Duque-Estrada. “We want to look more into that, and to understand what happens when we mix all the various components together. How does it affect stability? How would the process affect the way proteins are digested and absorbed in our body? We want to look at the final cooked product itself, as this is what we as consumers eat.”
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This would seem to indicate that eating more legumes can boost our immune system, a topic that Professor Petersen plans to investigate further in future. If researchers can show that certain protease inhibitors enhance resilience against disease, this would dramatically change perceptions of these compounds. “We would be able to say that they have some beneficial effects, and so maybe we shouldn’t remove all of them during processing,” outlines Dr Duque-Estrada. If health benefits can be demonstrated, this would be a powerful argument for increasing legume consumption, believes Professor Petersen. “In Denmark it is currently recommended to eat 100 grams of cooked legumes a day, while average intake is around 3-5 grams,” she explains. “If it can be shown that adhering to these recommendations will help prevent the prestates of cancer and other conditions, such as chronic intestinal diseases and inflammatory bowel disease, this would be a powerful motivation for increasing legume consumption. However, the project only started a year ago, so we’re still in the early stages.”
Beyond Sustainability
Beyond sustainability: a holistic approach to evaluate the nutritional quality of plant protein-based foods
Project Objectives
The Beyond Sustainability project are supporting the green transition, aiming to gain deeper insights into the ideal balance between sustainability and nutritional quality. While plant-based diets are increasingly popular, plant proteins are less digestible than those from animals, so some processing may be necessary to improve their nutritional quality. The project team aims to help identify the right level of processing for plant-based foods, with a view to maintaining nutritional standards and encouraging the shift towards a more sustainable agricultural model.
Project Partners
• Wageningen University & Research (NL): Prof. Maarten Schutyser, Prof. Atze Jan van der Goot • Federal University of Rio de Janeiro (BR): Prof. Anna Paola Pierucci • Brazilian Agricultural Research Corporation (BR): Dr. Caroline Mellinger • Bioptimate, bioptimate.com (DK): Dr. Keld Ejdrup Markedal, Dr. Jens Christian Sørensen
Project Funding
Independent Research Fund Denmark (Danmarks Frie Forskningsfond) (project number 1127-00274B).
Contact Details
Iben Lykke Petersen, PhD Associate Professor in Plant Proteins for Food Department of Food Science University of Copenhagen Rolighedsvej 26, DK-1958 Frederiksberg C T: +45 35 32 13 26 E: ilp@food.ku.dk W: https://food.ku.dk/english/research_at_food/ research-projects/2022/beyond-sustainabilitya-holistic-approach-to-evaluate-the-nutritionalquality-of-plant-protein-based-foods/
Iben Lykke Petersen Patricia Duque-Estrada
Iben Lykke Petersen is Associate Professor in the Department of Food Science at the University of Copenhagen. Her research interests include plant protein ingredients, particularly from pulses, and the nutritional quality of plant proteins. Patricia Duque-Estrada is an Assistant Professor in the Department of Food Science at the University of Copenhagen. She is a food and nutrition scientist, focused on the nutritional quality of plant proteins. Immune SEEDstem project Funded by Plant2Food, A Novo Nordisk Foundation Sponsored Initiative (Grant number NNF22SA0081019).
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