Effects of germination on physical and technological characteristics of quinoa (Chenopodium quinoa Willd.)

Quinoa is a pseudocereal belonging to the Chenopodiaceae family; it is widespread in South America countries where is mainly consumed as cooked seed. Quinoa is rich in saponins, that are bitter compounds responsible for the decrease in product acceptability. They are mainly located in the external layers. In order to remove saponins, quinoa is generally washed and/or pearled before its consumption. However, washing contaminates water whilst pearling lowers the nutritional properties of seeds. In this study, controlled germination has been explored as an alternative treatment to decrease quinoa bitterness, avoiding polluting processes and loss of nutrients. Seeds were germinated at 22 ºC for 12, 24, 48 and 72 hours, then dried at 55ºC for 6 hours and maintained at 4 ºC until analysis. Untreated and pearled quinoa were used as references. Chemical, physical, technological and sensory changes were assessed in both seeds and flours. Germination was associated with a decrease in seed diameter, test weight, and thousand-kernel weight, as a result of macromolecular hydrolysis occurring during germination. Germination process seemed to promote a significant decrease in saponin content (from about 4 mg/g in native seeds to 2.61 mg/g after 48 h), evaluated by the official Ecuadorian method NTE INEN 1672, an indirect approach, based on the foam height developed after vigorous agitation of seeds in water. Nevertheless, this trend is opposed to that shown by the spectrophotometric method: the latter exhibited an increase in saponin content during germination, from 5.3 to 6.6 mg/g db after 48 h. Moreover, other potential bitter compounds, as phenols and flavonoids, increased from 2.06 to 3.57 mg GAE/g db and from 3.18 to 4.09 mg QE/g db, respectively. Nevertheless, germination enhanced sugar formation, likely responsible for masking the perception of bitter taste, as shown by e-tongue results. The main effects occurred during the first 48 hours of the process. The relevant increase in amylase activity during germination highly affected the starch content, its pasting properties and water affinity. Foaming capacity of quinoa flour decreased from 30.5 to 18.4 %v/v, nevertheless, its stability increased from 47.0 to 54.1 %. On the other hand, no changes in freeze-thaw stability were observed. Information about the effects of germination on technological properties of quinoa flour will be useful for the development quinoa-enriched products. In this context, the bread-making performance of flour from germinated quinoa will be evaluated, taking into account both gluten and gluten-free formulations.