Impact of Phosphorylation on Techno-Functional, Rheological, and Digestibility Characteristics of Split Red Lentil Starch

Abstract

Crude starch is obtained as a by-product during production of lentil protein isolates and concentrates; thus, this starch carries the potential for value addition through chemical modifications. The present study therefore exploited split red lentil starch (LS) for development of cross-linked starches using phosphorous oxychloride (POCl₃). The lentil starches treated with 0.03%, 0.06%, 0.09%, and 0.2% levels of POCl₃ (starch dry weight basis) were labeled as CLS_0.03, CLS_0.06, CLS_0.09, and CLS_0.2, respectively. All phosphorylated lentil starches were observed to be safe for consumption, as phosphorous content was observed to be in the range of (0.0034–0.0154)%, which was below the prescribed limit of FAO (i.e., 0.4%). The lentil starches after phosphorylation exhibited reduced swelling power and solubility. The lower % breakdown values observed in pasting properties and lesser increment observed in phase angles values with rising frequency for phosphorylated lentil starches confirmed their high shear tolerance. The CLS_0.09 and CLS_0.2 also showed higher (1047/1022 cm⁻¹) ratio observed through FTIR compared to LS confirming the development of more ordered structure with the increase in distarch phosphate crosslinks. The spectra also shower higher absorption intensity of phosphorylated starches in the range of (900–1100) cm⁻¹. Moreover, it was observed that increase in levels of POCl₃ treatment led to development of more resistant starch (RS4) and also decreased the readily digestible starch content at higher treatment levels, suggesting its use in development of food products for diabetic patients with better sensory properties compared to conventional fibers which negatively affects food esthetics.