Karlsruhe Institute of Technology (KIT)
Prof. Dr. Katharina Scherf leads the Department of Bioactive and Functional Food Chemistry at the Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany. Together with her team, she studies the complex interplay between structure, functionality and bioactivity of food proteins. One of her main research interests are wheat-related disorders. Having studied food chemistry at the Technical University of Munich (TUM), Katharina Scherf obtained her PhD degree from the TUM. Then she worked at the Leibniz-Institute for Food Systems Biology at the Technical University of Munich and led the research group Functional Biopolymer Chemistry. Her research was awarded with several prestigious scientific prizes, including the ERC Starting Grant 2022, the Research Award of the German Coeliac Society (2019 and 2014), the Young Scientist Research Award of the Cereals & Grains Association (2018) and the Gerhard-Billek-Prize of the German Chemical Society (2015).
Department of Bioactive and Functional Food Chemistry, Institute of Applied Biosciences, Karlsruhe Institute of Technology (KIT), Adenauerring 20a, 76131 Karlsruhe, Germany
Wheat products are one of the pillars of food security worldwide. In European countries, bread consumption provides about 30% of carbohydrates, 25% of dietary fibre, 30% of protein and 12-30% of B-vitamins and minerals for human nutrition. However, wheat proteins are also known as triggers of wheat-related disorders in susceptible individuals. These include wheat allergy, celiac disease and non-celiac gluten sensitivity. More and more studies provide evidence for an increasing prevalence of wheat-related disorders, but the causes are still largely unknown. Next to changes in the human immune system, changes may also have occurred on the side of cereals. Wheat breeding for increased yield and resistance to abiotic and biotic stress factors may have changed the protein composition and the resulting immunoreactivity of wheat. To test this hypothesis, we investigated changes in agronomic characteristics, protein content and protein composition of German winter wheat cultivars first registered from 1891 to 2010.
The five hexaploid wheat (Triticum aestivum) cultivars most widely grown in Germany in each decade from 1891 to 2010 were sampled from the German Federal ex situ Genebank of crops at the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK, Gatersleben, Germany). All cultivars were grown together with three biological replications at Gatersleben in the harvest years 2015, 2016 and 2017. The protein content and composition of the wholemeal flours were determined by the Dumas combustion method and modified Osborne fractionation combined with RP-HPLC-UV. The content of selected celiac disease-active peptides was quantitated by LC-MS/MS. The results are presented as average of the three harvest years in the following and cultivars first registered before 1950 were designated as old, while those registered after 1950 were called modern.
According to expectations, the plant height decreased from 117-153 cm (old cultivars) to 76-99 cm (modern cultivars), whereas the yield increased significantly from 31-49 dt/ha to about 76 dt/ha. The protein content showed high variations within the five cultivars per decade and a slight decreasing trend from old to modern cultivars, but the differences were not significant. The overall protein content was less than 10% in most samples, because no fertilization was used in the field trials. Regarding protein composition, the proportion of albumins/globulins was between 17% and 26%. The albumin/globulin fraction comprises water- and salt-soluble proteins and contains enzymes, enzyme inhibitors and other protective proteins, many of which are also recognized as allergens. In the absence of any change over time, the allergenic potential of the set of wheat cultivars studied remained unaffected by breeding.
The proportions of gliadins decreased significantly over time from 62% to 46%, whereas those of glutenins increased significantly from 17% to 33%, resulting in a decreasing gliadin/glutenin ratio from 3.6 to 1.4. The total gluten proportion and content did not show any significant changes over time, because gliadins decreased and glutenins increased, so that the sum of both remained largely constant. The absolute content of four known celiac disease-active peptides including the so-called 33-mer, also showed no tendency to decrease or increase from old to modern cultivars. Furthermore, the variability caused by environmental effects in each year was higher than that caused by the genetic background of each cultivar. Taken together, all results point to the conclusion that the immunoreactivity of old and modern wheat cultivars appears to be similar.