Comparative Physicochemical and Functional Properties of Yellow- and Purple-Fleshed Sweet Potato (Ipomoea batatas Lam.) Flours and Their Application in Macaron Shells

Diversification of food systems creates opportunities for locally grown tropical crops. This study characterized flours obtained from purple-fleshed (PSP) and yellow-fleshed (YSP) sweet potato (Ipomoea batatas Lam.) roots cultivated in Guadeloupe and evaluated their use as the sole flour component of macaron shells. Chemical composition, particle size distribution, techno-functional properties, pasting behaviour, gel texture, small-amplitude oscillatory rheology, color, pigment content and antioxidant capacity (DPPH, ABTS, FRAP, and total phenolics; aqueous and 80% ethanolic extracts) were determined, and the physical parameters of the resulting shells were measured. YSP contained slightly more total starch (61.82 vs. 58.15 g/100 g DM), whereas PSP had a markedly higher amylose proportion (29.44 vs. 19.27% of starch). YSP milled to a finer powder showed higher water-holding capacity (7.98 vs. 4.97 g/g DM), water absorption, and swelling power, whereas foaming and emulsifying properties were comparable. YSP developed a much higher peak viscosity (1119.3 vs. 447.3 mPa·s) with a large breakdown, while PSP showed minimal breakdown, higher setback and final viscosity, harder and more resilient gels, and a faster increase in storage modulus during the first hour after pasting. PSP was darker and redder, whereas YSP was lighter and more yellow. YSP contained more total carotenoids (7.58 vs. 1.04 µg β-carotene eq/g DM), while PSP contained 17.25 mg C3G eq/100 g DM of total monomeric anthocyanins and had a richer aqueous phenolic fraction with higher ABTS and FRAP activity. Both flours produced shells of comparable dimensions, but YSP shells were heavier and had higher water activity. Overall, both flours could serve as the sole flour base of macaron shells, but their contrasting starch composition, hydration, pasting and pigment profiles means the two varieties are suited to different product objectives.