Characterisation And Food Applications Of Frafra Potato (Solenostemon Rotundifolius) Flour

Abstract

Frafra potato (Solenostemon rotundifolius) is an underutilised climate-resilient tuber crop commonly cultivated in the tropics, including Ghana. Several accessions of Frafra potato have been identified and bred to broaden its application in different food products. This study characterised the starch and flour made from ten (10) Frafra potato (FP) accessions, from Ghana (released) and Burkina Faso (unreleased), in terms of their starch (FPS) and flour (FPF) yield, and their physicochemical and functional characteristics. FPS yields were similar (p < 0.05) and ranged from 35 to 39% dry matter. FPS also had similar (p < 0.05) colour but differed in paste clarity, ranging from 51 to 63% of the FPS gels. The starches from all accessions displayed similar (p < 0.05) amylose/amylopectin ratio, syneresis %, granule types and shapes. Differences were observed in the thermal properties of the starches, even though XRF and FTIR spectra revealed them to be A-type starches, which is typical of root crops. The variations in granule size and thermal properties between FPS likely affect FP's cooking and eating quality. The released accessions had significantly higher (p < 0.05) protein and ash, ranging from 5.1 to 8.7% and 5.1 to 6.5%, respectively, relative to the unreleased accessions. Four proteins commonly found in tuber crops (lipoxygenase, patatin, sporamin and tarin) and protease inhibitors (Bowman-Birk PIs) were identified in FPF based on their molecular weight (SDS-PAGE). Amino acids analyses (LC/MS) of the FPF identified seven (7) essential amino acids (Valine, Tryptophan, Threonine, Histidine, Methionine, Lysine, and Isoleucine). FPF showed similar functional properties, and their slurries exhibited typical shear-thinning pseudoplastic flow. Particle size analyses of FPF showed them to be generally fine particles, mostly passing through sieve size 100μm, and their sorption behaviour was characterised by a maximum allowable 10% EMC at about 0.5 aw. Considering their fine particle size distribution, relatively high protein content and other functional properties, FPF was used as a replacement for wheat flour in the processing of gluten-free bread. The results showed that the application of dough conditioners (egg-gelatin powder combination) followed by Transglutaminase treatment could technologically be used to develop gluten-free bread from FPFwith comparable attributes as that obtained from wheat flour (WTB). The dough and bread structure showed that the dough conditioners technologically mimicked the gluten-like network, as demonstrated by textural and dough properties. SEM revealed the improved network matrix and well-embedded starch granules in FPB comparable to WTB. A panel of nine (9) trained assessors were used to assess six (6) bread samples, five of which were gluten-free, and one was typical wheat bread, using the Quantitative Descriptive Analysis (QDA®) method. The products were differentiated in appearance by brown crust (top and bottom), smooth bottom crust and homogeneous bottom crust and by a minor bitter flavour note perceived in the gluten-free products. The top and bottom crusts of WTB and B14 had the lowest intensity (lightest) of brown colour in the sample set, but they differed statistically (p ≤ 0.05) from each other. All the bread samples smelled and tasted like typical wheat bread. Sensory profile of the products correlated strongly with the colour and dough properties of FPF. Thus, in developing bread from FPF, attributes of colour and dough properties should be considered. The study showed that FPF has characteristics that make it suitable for gluten-free bakery applications and can help address nutrition and food security in Ghana and Sub-Sahara Africa by promoting its utilisation.