Enhancing mechanical and water barrier properties of starch film using chia mucilage.

Biodegradable packaging materials are increasingly being investigated due to rising concerns about food safety and environmental conservation. This study examines the incorporation of chia mucilage (CM) into starch-based films using the casting method, aiming to understand its effects on the structure and functionality of the films. CM, an anionic heteropolysaccharide, is hypothesized to enhance the mechanical and barrier properties of the films through polymer interactions and hydrogen bonding. Our findings confirm that CM incorporation results in films with uniformly smooth surfaces, indicating high compatibility and homogeneity within the starch matrix. Notably, CM improves film transparency and crystallinity. Mechanical assessments show a remarkable elevation in tensile strength, soaring from 5.21 MPa to 12.38 MPa, while elongation at break decreases from 61.73 % to 31.42 %, indicating a trade-off between strength and flexibility. Additionally, water solubility decreases from 57.97 % to 41.40 %, and water vapor permeability is reduced by 30 % with CM loading. These results highlight the role of CM in facilitating the formation of a dense, interconnected polymeric network within the starch matrix. Given the soluble dietary fiber nature of CM, the CS/CM (corn starch/chia mucilage) blended films are expected to be safe for food packaging and applicable as edible films with health benefits.

Addition of amino acids modulates the in vitro digestibility of corn starch.

The addition of amino acids (AAs) including glycine (Gly), lysine (Lys) and glutamic acid (Glu) with different concentrations on starch morphological, physicochemical and in vitro digestion properties were studied. While AAs showed no effects on neither morphology nor crystalline characters, they all significantly influenced the starch relative crystallinity and swelling capacity in an order of Glu > Lys > Gly. For all samples, both fastly- and slowly- digestible starch fractions (SF and SS) were observed. While Glu and Gly increased SF content with a faster digestion rate, they reduced SS content with a slower digestion rate. On contrary, Lys reduced SF content and the digestion rate of SS. The inhibitory effects of AAs on starch retrogradation and enzyme activities, the acidic environment and Maillard reaction between starch phosphate monoester and Lys are responsible for altered starch digestibility. This study betters our understanding concerning how AAs interactions affect starch functional properties.

Mutual interactions between α-amylase and amyloglucosidase in the digestion of starch with distinct chain-length distributions at a fully gelatinized state.

Amyloglucosidase (AMG) and α-amylase (AMY) are both involved in starch digestion in human small intestine, whereas their mutual interactions with starch molecules of distinct structures are still unknown. In the current study, starches with different amylose contents (from waxy to high amylose content) were used to investigate the starch-enzyme interactions in the in vitro starch digestibility at a fully gelatinized state. The starch chain-length distributions (CLDs) before and after digestion were obtained by size-exclusion chromatography (SEC), and the in vitro digestograms with a single or combined AMY and AMG were obtained. The results showed that the digestion extent generally followed an order of AMG > AMG + AMY > AMY, suggesting that there was an antagonistic effect between AMG and AMY. Starches with distinct structures were preferred differently by these enzyme combinations. For example, waxy starch could be digested at a much faster rate by AMG + AMY than by a single enzyme. By fitting to the logarithm of slope plot and the combination of parallel and sequential kinetics models, two different starch digestible fractions (slowly vs. rapidly) were identified, and AMG and AMY typically had an antagonistic effect in digesting the rapidly digestible fraction. Finally, the CLD results suggested that a small starch portion with DP 7-2000, not present in the original starch samples, was formed after the digestion. The starch portion with DP > 2000 could be very rapidly digested by AMY, whereas the starch portion with DP 7-2000 could only be less effectively digested by AMY, and the addition of AMG could further reduce this activity. This study provides important information for understanding the starch-enzyme interactions as well as their effects on starch digestibility at a molecular level.