Evaluation of techno-functional, morphological, and rheological characteristics of spontaneously fermented wheat starch

This research shows that spontaneous fermentation can be used as an efficient and environmentally sustainable bioprocessing method for tailoring the structural and functional properties of commercially available wheat starch. In this study, fermentation was continued for 360 h in order to bring the pH below 3.5 and titratable acidity above 5%, which was the required standard as per review of literature for fermented starch. The pH of wheat slurry was reduced to 3.33, while titratable acidity was increased to 6.28% lactic acid. Compared to native starch, 360 h fermentation led to significant ( p ≤ 0.05) relative increase in amylose content (47.06%), water absorption index (103.74%), oil absorption capacity (16.27%), swelling power (63.20%), water solubility index (133.50%) and relative decrease in paste clarity (82.14%). To investigate the changes in starch structure, representative samples were taken at 0, 144 and 360 h. These samples were examined for morphological, pasting, rheological, particle size and multivariate analyses, which enabled the development of structure-function relationships. FE-SEM analysis indicated the occurrence of progressive surface erosion and granular fragmentation, along with changes in size distribution due to intergranular association. Fermentation of starch resulted in relative increase in the peak viscosity by 14.59% and final viscosity by 53.97%. In addition, texture profile analysis showed that spontaneous fermentation resulted in formation of hard gels with increased gumminess. The results of principal component analysis confirmed that fermented starch samples could be distinguished from fermentation period. The obtained results indicated that fermentation is a feasible and sustainable method for starch modification without use of chemical reagents.