Jackfruit seed flour substitution reduces oil uptake in yeast-raised doughnuts: role of amylose content, crust microstructure, and textural properties

Jackfruit seeds can be valorized into jackfruit seed flour (JSF), a starch-rich plant-based ingredient with the potential to partially replace wheat flour in fried products and reduce oil uptake. This study evaluated the effects of substituting wheat flour with 5%–20% JSF on oil uptake, moisture loss, texture, microstructure, and sensory acceptability in yeast-raised doughnuts. JSF was prepared by boiling, drying, milling, and sieving, with a flour yield of 21.58%. Doughnuts containing 0%, 5%, 10%, and 20% JSF were deep-fried at 165 ± 5°C for 2 min and analyzed for amylose content, fat and moisture contents, oil uptake, texture, scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared (ATR–FTIR) spectra, and sensory quality. JSF significantly increased amylose content from 19.17% in the control to 41.86% at 20% substitution (p < 0.05). Doughnuts containing 20% JSF showed significantly lower oil content (23.21 g/100 g) and oil uptake (13.37 g/100 g) than the control (27.01 and 17.19 g/100 g, respectively), together with lower moisture loss (9.75 g/100 g). SEM revealed a denser and less porous crust and crumb structure with increasing JSF substitution, while ATR–FTIR indicated lipid-associated bands consistent with oil retention in the starch-rich crust matrix. Hardness increased significantly at 20% JSF in both dough and doughnuts. Amylose content was negatively correlated with oil uptake (r = −0.89) and positively correlated with hardness (r = 0.94). Sensory acceptability was not significantly affected. Overall, JSF shows promise as a sustainable ingredient for producing lower-fat doughnuts with acceptable consumer quality. Practical Applications: Jackfruit seed flour (5%–20%) significantly reduced oil uptake and final oil content in yeast-raised doughnuts, with 20% substitution giving the greatest reduction. Higher JSF substitution increased amylose content and produced a denser, less porous crust and crumb structure, which was associated with lower oil absorption. Despite increased hardness at 20% JSF, sensory acceptability was not significantly affected, suggesting good potential for reformulating lower fat doughnuts.

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