Influence of particle size distribution on nutritional composition, microstructural and antioxidant properties of orange and purple‐fleshed sweet potato flour

Abstract

Influence of particle size distribution on nutritional composition, microstructural, physicochemical, and antioxidant properties of orange and purple‐fleshed sweet potato flour (SPF) with particle sizes 75–355 µm were investigated. As particle size decreased, protein content, water absorption capacity, and water solubility index of both SPF decreased, whereas starch, reducing sugar, and crude fat increased. Total polyphenol contents (TPC) in purple‐fleshed SPF (8.25–9.27 mg GAE/g DW) were higher than orange ones (0.22–0.28 mg GAE/g DW), whereas vitamin C contents in orange‐fleshed SPF (23.59–29.26 mg/100 g DW) were higher than purple ones (4.24–4.89 mg/100 g DW). Antioxidant capacities of both SPF were gradually increased with decrease of particle size due to the contribution of higher TPC and vitamin C contents. All SPF fractions exhibited irregular‐shaped surface. SPF with particle size 75 µm might be used to produce novel food products with desired nutrients and functional properties. Novelty Impact Statement Both orange and purple‐fleshed SPF with different particle sizes possessed significant difference in nutritional composition and antioxidant properties. TPC contents in purple‐fleshed SPF were higher than orange ones, whereas vitamin C contents in orange‐fleshed SPF were higher than purple ones. SPF with particle size 75 µm with higher polyphenols and vitamin C contents and stronger antioxidant activities might be used to produce novel food products.

Characterization and Technological Potential of Underutilized Ancestral Andean Crop Flours from Ecuador

“…These authors observed that according to the particle size selected for these flours, the starch content could vary up to 20%; thus, in flours of sizes > 32 mesh, 42-80 mesh and 125-400 mesh, the starch content was 50.6%, 60.2% and 68.4%, respectively, indicating that large agglomerates could accumulate in the first two fractions. A similar effect was observed in yam (Ipomoea batatas) flours from Hebei (China), and the starch percentages obtained (43.58%), similar to those of the present work, presented a particle size of 355 µm; however, with particle size 75 µm, these authors obtained a somewhat higher content of starch (61.90%) [44]. The increase in starch with smaller particle sizes is attributed to the breakage of the flour structure so more active sites are exposed for enzymatic degradation [45].…”

“…The increase in starch with smaller particle sizes is attributed to the breakage of the flour structure so more active sites are exposed for enzymatic degradation [45]. In parallel, it has also been observed that the sugar content may increase slightly for the finest particle sizes, while decreasing for medium and coarse particle sizes, attributing this fact to the hydrolysis of starch into oligosaccharides and monosaccharides in the flour [44].…”

Technological Properties of Orange Sweet Potato Flour Intended for Functional Food Products as Affected by Conventional Drying and Milling Methods

“…In addition, there were no significant differences among flours produced at 80 °C with one and two grindings. Azeem et al observed a similar trend: starch content increased as particle size decreased in SPFs …”

“…The same behavior was reported by Azeem et al in SPFs. They attributed this behavior to the individual hydration capacity of particles, intercellular microstructure, and degree of arrangement of hydroxyl groups in covalent bonds between chains of starch . Kerr et al reported that the WHC of cowpea flour was significantly less in finely milled flours.…”

“…This reveals the importance of the particle size of sweet potato flour in its technological and nutritional properties. 16 Drying and milling are two steps that individually define the quality of sweet potato flour by changes in functional characteristics. Importantly, knowledge of the consecutive effect of drying and milling is likely to improve control of the desired final quality of the flour and even define its use as a food ingredient.…”