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Gluten from some wheat varieties: a comparative study

by luciano

Knowledge of the gluten composition of soft, durum and spelt wheat is relevant for the success of final baked products (especially salty baked product) and/or for the production of pasta. The characteristics of gluten are also fundamental if the aim is to create products suitable for people genetically predisposed to celiac disease, for those who are sensitive to gluten without celiac disease and, extensively, for those who suffer from intestinal inflammation. For all these people it is important to make products that are as digestible and tolerable as possible. Of all the known grains, einkorn wheat is the one that is considered the most suitable for this purpose.
The study “Comparative Study on Gluten Protein Composition of Ancient (Einkorn, Emmer and Spelt) and Modern Wheat Species (Durum and Common Wheat). Sabrina Geisslitz et al. Published: 12 September 2019 in Foods (MDPI)” analyzes some characteristics of the gluten of some grains (300) highlighting the differences; it also analyzes the effect on them of the use of nitrogenous fertilizers in cultivation.

The reason for the interest in the search for varieties of einkorn, emmer and spelt:
The “ancient” wheats einkorn (Triticum monococcum L., diploid), emmer (T. dicoccum L., tetraploid) and spelt (T. aestivum ssp. spelta, hexaploid) have been cultivated in very low amounts compared to the “modern” wheat species common wheat (T. aestivum L., hexaploid) and durum wheat (T. durum L., tetraploid) in the 20th century. The reasons for the low cultivation of ancient wheats are 30–60% lower grain yields, the presence of husks and poor baking properties compared to common wheat [1]. Nevertheless, ancient wheats have been rediscovered in the last 20 years, because a growing number of consumers associate their consumption with sensory and health benefits due to their comparatively higher contents of e.g., ferulic acid, vitamins, alkylresorcinols and lutein [2–8].
Common wheat is most suitable for bread making, because the flour forms a viscoelastic dough with a high gas holding capacity when it is mixed with water. In contrast, flours of ancient wheats yield softer dough with low elasticity and high extensibility because of their poor gluten quality [1,9–11].
This latter feature translates into a less “strong”[A] and therefore more digestible gluten. In addition, einkorn and emmer do not contain the gluten fraction (33mer” : Quantitation of the immunodominant 33-mer peptide from α-gliadin in wheat flours by liquid chromatography tandem mass spectrometry. Kathrin Schalk et al. 2017. Scientific Reports.) which is considered the one that most activates the immune response in celiac subjects as well as being among the least digestible. This last feature makes these grains, especially einkorn[B], the main candidates for decreasing exposure to celiac disease in genetically predisposed subjects.

Featured in the study:
The total protein content was equally influenced by location and wheat species, however, gliadin, glutenin and gluten contents were influenced more strongly by wheat species than location. Einkorn, emmer and spelt had higher protein and gluten contents than common wheat at all four locations. However, common wheat had higher glutenin contents than einkorn, emmer and spelt resulting in increasing ratios of gliadins to glutenins from common wheat (< 3.8) to spelt, emmer and einkorn (up to 12.1). With the knowledge that glutenin contents are suitable predictors for high baking volume, cultivars of einkorn, emmer and spelt with good predicted baking performance were identified. Finally, spelt, emmer and einkorn were found to have a higher nitrogen partial factor productivity than common and durum wheat making them promising crops for a more sustainable agriculture.

It is generally accepted that gluten proteins are one of the most important factors determining the baking quality of wheat flours. Gluten proteins are storage proteins and classified into gliadins (GLIA) soluble in aqueous alcohol and glutenins (GLUT) soluble in aqueous alcohol only after reduction of disulfide bonds. Not only the amount, but the ratio between GLIA and GLUT (GLIA/GLUT) has been shown to be responsible for good baking quality. GLIA/GLUT of common wheat is typically 1.5–3.1 [12,13], but a recent study showed that the GLIA/GLUT of ancient wheats was much higher (spelt: 2.8–4.0; emmer: 3.6–6.7; einkorn: 4.2–12.0)
Quantitation of GLIA, GLUT, Gluten and Total Protein Contents