Extraction and Comprehensive Characterization of Starch From Ryegrass (Lolium multiflorum L.) Seeds as a Non-Conventional Source

Abstract

Our research group focused on natural, but unexploited starches, specifically ryegrass seed starch, which was obtained using aqueous (AE) and reducing (RE) extraction. The physical-chemical, structural, morphological, rheological, and nutritional properties were evaluated. RE starch showed a higher yield (37.81%) compared to AE (31.55%) and exhibited higher luminosity and transmittance, making it the clearest sample. AE starch exhibited a mean particle size (D50) of 6.95 ± 0.08 µm, whereas RE starch showed a mean particle size (D50) of 7.54 ± 0.07 µm. Both starches presented small variations among samples and an irregular trimodal particle size distribution. The apparent amylose content of RE starch (17.25%) was higher than AE. RE starch exhibited greater solubility with increasing temperature, reaching a maximum of 7.27 g of gel/g of sample. The highest swelling power (2.56%) was observed in RE starch. RE extraction also resulted in a higher paste temperature (95◦C) and greater retrogradation tendency (2954 mPa.s). The highest syneresis occurred at 48 h, with AE and RE showing 24.20% and 27.58%, respectively. RE starch increased both rapidly and total starch digestibility, while slowly digestible and resistant starch fractions, as well as the glycemic index, remained unaffected.