The formation of starch-lipid complexes in instant rice noodles incorporated with different fatty acids: Effect on the structure, in vitro enzymatic digestibility and retrogradation properties during storage

Abstract

The formation of starch-lipid complexes in instant rice noodles (IRN) free from and incorporated with fatty acids (FAs) and their impacts on textural, in vitro digestive and retrogradation properties were investigated. The gelatinization enthalpy values of IRN samples (1.24-4.93 J/g) were noticeably decreased (P < 0.05) compared to rice starch samples (2.54-6.89 J/g) fortified with FAs. Additionally, long-chain saturated FAs (stearic acid (SA, C18:0)) complexes produced higher ordered structures than the shorter-chain FAs (C12:0-C16:0), for 18-carbon FAs, the unsaturated FAs (linoleic acid (LOA, C18:2)) exhibited the strongest intermolecular interactions with rice starch. The relative crystallinity of IRN (27.01%-38.47%) was lower than the rice starch-FAs complexes (38.36%-56.80%). FAs delayed the retrogradation degree of IRN storaged at 4 °C for 21 days ascribed to the formation of V-type complexes. Higher enzymatic resistance was observed in IRN added FAs with resistant starch content increased from 5.13% to 14.42% (LOA), and the sample fortified with SA exhibited the highest slowly digestible starch content (35.92%). SEM revealed that the IRN compounded with palmitic acid, SA and LOA displayed more compact and regular structures. Overall, the formation of starch-FAs complexes probably is a novel strategy in improving the textural, digestive, and retrogradation properties of IRN.

Keywords: Crystal structure; Digestibility; Instant rice noodles; Retrogradation; Rice starch; Starch-fatty acid complexes.