Soy protein dominates the plant-based space. Ninety-five percent of all plant-based proteins, with the exception of wheat, come from this legume – which originally hails from East Asia.
Soy protein contains no cholesterol, a minimum amount of fat, and perhaps most importantly for consumers seeking a high-protein meat alternative, soy is a complete protein. This means that it contains all nine essential amino acids, including those humans cannot produce themselves.
Dependence on a singular plant-protein source, however, can encourage monoculture cropping and have detrimental effects on global biodiversity. The vast majority of soy (80%) is produced in just three countries – the US, Brazil, and Argentina – and is regarded a major contributor to deforestation in South America.
But what if there was another high-protein crop that could help meet growing global demand for plant-based foods? Researchers in Germany suspect they have found just the thing: rapeseed.
“Due to a rising world population it will become increasingly important to open up further protein sources, to guarantee the supply for the world population with enough protein,” nutritionist Christin Volk from the Institute of Agricultural and Nutritional Sciences at Martin Luther University Halle-Wittenberg told FoodNavigator.
“Previous studies showed a valuable amino acid profile [in rapeseed], which is comparable to that of soy protein. For this reason, rapeseed protein is a promising new protein source.”
Rapeseed protein and our metabolism
Rapeseed, or canola as it is known in the US and Canada, contains approximately 20% high-quality protein.
Rapeseed also contains phytochemicals – chemical compounds produced by plants – which the researchers believe could have beneficial effects on health. Another advantage is that rapeseed is already being cultivated in Europe, predominantly to produce rapeseed oil.
Rapeseed cake, a by-product of oil production, is currently used as a nutritious feed for livestock, but the researchers see potential for this protein-rich side stream to be used as an ingredient for new food products.
Having determined that rapeseed has a comparably beneficial composition of amino acids to soy, the researchers set out to investigate its effects on metabolism. “So far, only a few data on the effect of rapeseed protein intake in humans had been available,” said Volk’s colleague Gabriele Stangl.
The researchers conducted a study with 20 participants, who were invited to eat a specifically prepared meal on three separate days: noodles with tomato sauce, that either contained no additional protein or was enriched with soy or rapeseed protein.
At the end of each meal, blood was regularly drawn from the participants over a six-hour period. According to Stangl, this study design enabled the researchers to assess the acute metabolic response of each study participant to the dietary requirements.
“The rapeseed protein induced comparable effects on metabolic parameters and cardiovascular risk factors as soy protein,” noted Volk. “Rapeseed even produced a slightly more beneficial insulin response in the body.”
Another benefit of rapeseed, the researchers reported, was that participants had a longer feeling of satiety after consuming the rapeseed protein.
Masking the ‘mustard flavour’
The one key drawback of rapeseed protein is its bitter taste, which the researchers described as similar to that of mustard. This is why rapeseed has predominantly been used for its oil, and its by-product, for animal feed.
For Volk, this characteristic means that any ingredient produced from rapeseed protein should be geared towards savoury, rather than sweet. “The mustard flavour of rapeseed protein limits its use for protein shakes or sweets,” he told FoodNavigator.
“It is suggested that kaempferol 3-O-(2'''-O-sinapoyl-ß-sophoroside) is mainly responsible for the bitter off-taste. Currently, suitable technological processes or breeding strategies are [being] developed to remove these plant constituents from rapeseed.”
Indeed, with the origin of the bitter taste now known, two options have been suggested for industry: the first would be to develop an extraction scheme to minimise the kaempferol derivative or to chemically convert or destroy the bitter component, the second would be for plant breeding companies to breed varieties with low or no kaempferol.
Food formulation and consumer acceptance
Volk concluded that rapeseed appears to be a valuable alternative to soy in the human diet.
Concerning its functionality in food formulation, the nutritionist stressed the study focused more on the impact on the human metabolism, rather than its potential in food manufacturing facilities. “Therefore, this is a challenge for the food industry,” he told us. “But I am confident that with some research, there will be many products suitable for the use of rapeseed protein.”
Volk also suspected consumer acceptance of rapeseed protein would be high, in part due to concerns over soy’s phytoestrogen content. Phytoestrogens – known as isoflavones in soy – have a weak estrogen-like action, and it has been suggested that when consumed in high quantities, they have the potential to disrupt the female hormone system.
“Since rapeseed oil is already in daily use in many households in Europe, rapeseed is a familiar product.
“Additionally, it has some strong advantages to soy products: it is free of genetic modifications and phytoestrogens. For those reasons, I assume rapeseed protein will be easily accepted.”
Source: Nutrients
‘Postprandial Metabolic Response to Rapeseed Protein n Healthy Subjects’
Published 29 July 2020
DOI: https://doi.org/10.3390/nu12082270
Authors: Christin Volk, Corrina Brandsch, Ulf Schlegelmilch, Monika Wensch-Dorendorf, Frank Hirche, Andreas Simm, Osama Gargum, Claudia Wiacek, Peggy G. Braun, Johannes F. Kopp, Tanja Schwerdtle, Hendrik Treed, and Gabriele I. Stangl.