Ultrasound modification of grass pea starch: Amplitude-time effects on gel strength and structural properties

Grass pea (Lathyrus sativus L.) starch (GPS) was treated with ultrasound at different amplitudes (30 %, 60 %, 100 %) and sonication time (10, 20, 30 min) to investigate its impact on structural and functional properties. The effects of ultrasound treatment on the physicochemical, pasting, textural, thermal, and morphological properties of the starch were examined. Scanning electron microscopy (SEM) revealed that ultrasound treatment generated surface pores on the granules, with their number increasing at higher amplitudes. Increasing the sonication amplitude and time significantly enhanced the swelling power and solubility of the starch. Ultrasound treatment reduced the gelatinization enthalpy (ΔH) by disrupting the crystalline regions of starch granules, thereby decreasing their crystallinity. The GPS treated at 100 % amplitude for 30 min had the lowest crystallinity (28.38 %) and ΔH (5.95 J/g) compared to native starch (53.85 % crystallinity and 12.55 J/g ΔH). While ultrasound treatment overall increased the onset gelatinization temperature (To), extended sonication time to 30 min at higher amplitudes ultimately led to a reduction in To. Moreover, the treated starches exhibited higher peak, breakdown, and final viscosities than the native GPS. The gel prepared from starch sonicated at 100 % amplitude for 10 min demonstrated the highest hardness among all samples. Therefore, the modifications induced by ultrasound have the potential to strengthen the gel structure of the modified starch, highlighting its suitability as a strong gelling agent for various applications in the food industry.