Researchers from the Swedish University of Agricultural Sciences (SLU), Alnarp, found that extrusion processing of quinoa grains increased its protein crosslinking and specific fiber type solubility. At the same time, the nanostructure investigated by SAXS and WAXS showed that extrusion processing caused morphological changes in the protein and starch of the extruded quinoa foods. While nutritional characteristics of quinoa foods were surprisingly impacted mildly, e.g., reduced essential amino acids to a minor extent (except valine and methionine), the final products met the nutritional requirements of the FAO.
Quinoa is the golden protein grain from Peru with a high nutritional value such as proteins, vitamins, minerals, dietary fibers, starch, bioactive compounds, etc. It is increasingly attractive for many food product applications. With the rise of quinoa as an alternative protein source worldwide, more knowledge on the effect of extrusion processing of quinoa towards its protein chemistry and interactions as well as its structure is needed for better nutritional and functional tuning of processed quinoa foods.
This study was conducted to enhance the value of traditional Peruvian foods, which were primarily produced by extrusion processing to develop breakfast cereals, ready-to-eat snacks, porridge, and instant quinoa products. The extrusion method was proven to be more favorable due to its mild impact on the protein properties of quinoa compared to other processing methods such as boiling, roasting, or microwave processing.
“Learning about good ways to preserve nutrients such as essential amino acids while processing is an essential knowledge for us all food consumers and the food processing industry,” explained Associate Professor Ramune Kuktaite, lead investigator of the study at SLU, Alnarp.
Innovative methods for sustainable food production
The research was a part of the Protein2Food project funded by the EU’s Horizon Research and Innovation Framework Program and the strategic national research program “Trees and Crops for the Future (TC4F)”. In the investigation, four different forms of quinoa were studied using the small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) at MAX IV.
“From our previous studies in explaining plant protein structures in the bio-based materials and composites, we learned that SAXS could be an advantageous method to determine plant protein arrangement in temperature-processed bio-based products. For this study, it was also of high relevance to use the WAXS method to investigate the impact of processing on quinoa starch crystallinity,” explained Kuktaite.
With the use of SAXS and WAXS synchrotron techniques, the researchers were able to uniquely monitor how the protein and starch components (and in some cases their types) in quinoa foods were affected by the temperature processing and connect the synchrotron data with the observed changes in the nutritional characteristics of the processed quinoa foods. However, differentiating the protein types in quinoa by SAXS was still a challenge, and therefore it needs to be explored further.
“We were surprised by the microstructure differences in quinoa breakfast cereals observed by X-ray tomography. Despite a very similar appearance of the extruded breakfast foods and extruded-dried foods, we found that the inner microstructure of these two products were essentially differing in the porosity, which might result in different liquid absorption behavior, “explained Kuktaite
Kuktaite R, Repo-Carrasco-Valencia R, de Mendoza CC, Plivelic TS, Hall S, Johansson E. Innovatively processed quinoa (Chenopodium quinoa Willd.) food: chemistry, structure and end-use characteristics. J Sci Food Agric. 2021 Mar 12. DOI: 10.1002/jsfa.11214. Epub ahead of print. PMID: 33709442.