Influence of Maturity and Geographical Origin on the Quality Characteristics of Fox Nut (Euryale ferox) Seeds from Bihar and Manipur

Abstract

Euryale ferox Salisb. (fox nut) is an important aquatic crop cultivated in the stagnant water bodies of northeastern India, particularly in Bihar, Manipur, West Bengal, Assam, Uttar Pradesh, and Madhya Pradesh. Bihar contributes nearly 80% of global fox nut production; however, exploring the popping potential of seeds from other regions is essential for expanding sustainable production. This study investigated the influence of seed maturity on the popping quality characteristics of fox nut seeds collected from Bihar and Manipur. Seeds were harvested at five developmental stages: 10, 20, 30, and 40 days after flowering, along with naturally abscised mature seeds. The quality attributes associated with popping were evaluated through engineering properties, proximate composition, scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), pasting properties, rheological behavior, dynamic light scattering (DLS), and textural analysis. The results revealed that the carbohydrate content increased progressively with seed maturity, rising from 17.84% to 48.03% in Bihar seeds and from 22.90% to 51.10% in Manipur seeds. SEM observations revealed that maturation promoted the development of a dense and compact starch–protein matrix in Bihar seeds, which is expected to improve the retention of internal steam pressure during roasting and thereby enhance popping performance. In contrast, mature Manipur seeds exhibited a comparatively less compact starch matrix, suggesting lower structural integrity for pressure retention during popping. Furthermore, water absorption capacity increased with maturity in both seed origins, corresponding to the progressive accumulation of starch during seed development. Overall, the findings demonstrate that seed maturity significantly influences the structural and physicochemical characteristics governing popping quality, with mature Bihar seeds exhibiting superior microstructural features favourable for efficient popping. These results provide valuable insights for determining the optimum harvest stage and evaluating the commercial potential of fox nut cultivation beyond Bihar.