Fermenting soy beans could lead to the removal of proteins behind soy allergies, suggest two recent studies from Spanish and American scientists.
The escalation in the incidence of food allergies over the past few decades has resulted in significant changes on both sides of the Atlantic, and while there are some positive signs that developments in science help, avoidance currently remains the only safe option.
However, new research from researchers at the University of Illinois and the Instituto de Fermentaciones Industriales (CSIC) in Madrid, Spain suggests that allergen-free soy products could be nearer than previously thought, simply by fermenting the beans with a number of microorganisms, including bacteria, molds, and yeast.
"When we fermented soy seeds, flour, or meal by introducing certain microorganisms, inmmunoreactivity was significantly reduced - by as much as 99 per cent. This shows that we have the potential of developing nutritious, hypoallergenic soy products," said researcher Elvira de Mejia from the University of Illinois.
While the actual prevalence of soybean allergy in the general population is unknown, some have estimated that it affects only 0.5 per cent of the population. However, according to de Mejia, soybean allergy may be on the rise. Because soy is used as in ingredient in many food products a technique that can eliminate its allergenicity is widely sought.
The researchers analysed the amino acid profile of soy products after fermenting them with Lactobacillus plantarum, Bifidobacterium lactis, Saccharomyces cereviseae, Aspergillus oryzae, Rhizopus oryzae, and Bacillus subtilis.
In reports in the Journal of Agricultural and Food Chemistry and Food Chemistry, de Mejia and co-workers state that the L. plantarum-fermented soy flour showed the highest reduction in immunoreactivity, ranging from 96 to 99 per cent, depending upon the sensitivity of the human plasma, obtained from the World Health Organization (WHO).
"Why do we see this reduced immunoreactivity? During the fermentation process, proteins are broken down into very small pieces, pieces that can't be identified by the antibodies that produce the allergic reaction," she explained.
The essential amino acid profile of the soy products was improved as a result of fermentation, noted the researchers, with the production of new peptides that may be beneficial.
"We want to evaluate some of the bioactive peptides that were produced during fermentation because we believe they may have other benefits. In particular, we're interested in their effect on lipogenesis, so we'll be testing these hydrolysates in adipose cells," said de Mejia.
Writing in the journal Food Chemistry, the researchers state: "Studies on the optimization of the effect of fermentation and hydrolysis on the reduction of immune response are on-going in our laboratory, which may lead to the development of hypoallergenic soy foods."
The studies were funded by the USDA Future Foods Initiative and the Illinois Soybean Association.
Determination of safe levels
In the absence of hypoallergenic foods, researchers from Switzerland, Denmark and Italy reported last summer that the no observed adverse effect level (NOAEL) for soy in Europe should be two milligrams.
"Knowledge of the severity of symptoms of soy allergy and the threshold dose of soy is most important and might have a major effect on food-labelling directives," they wrote in the Journal of Allergy and Clinical Immunology (June 2007, Volume 119, Issue 6, Pages 1489-1496).
The European researchers tested blood from volunteers for specific immunoglobulin E (IgE), the predominant antibody associated with an allergic response, to soy, peanut, and soy proteins, Bet v 1 and Gly m 4.
"None of our patients with soy allergy reacted to the starting dose of 2 mg of soy (1 mg of soy protein), which thus was the NOAEL for our study population," wrote the researchers.
Sources: Food Chemistry
Volume 108, Issue 2, Pages 571-581
"Immunoreactivity reduction of soybean meal by fermentation, effect on amino acid composition and antigenicity of commercial soy products"
Authors: Y.-S. Song, J. Frias, C. Martinez-Villaluenga, C. Vidal-Valdeverde and E.G. de Mejia
Journal of Agricultural and Food Chemistry
Volume 56, Issue 1, Pages 99-105, doi: 10.1021/jf072177j
"Immunoreactivity and Amino Acid Content of Fermented Soybean Products"
Authors: J. Frias, Y.S. Song, C. Martinez-Villaluenga, E.G. De Mejia, C. Vidal-Valverde