Physicochemical Properties of Mung Bean Starches Isolated From Four Varieties Grown in Sri Lanka

Printable hydrogels based on starch and natural rubber latex with high toughness and self-healing capability

Fully bio-based hydrogels with printability, high toughness, self-healing, robust mechanical property and conductivity are highly desired but now remain a huge challenge. In this work, inspired by preparation of "Liangpi" (cold noodles, a traditional Chinese food), a satisfactory hydrogel was constructed using starch and natural rubber latex through a simple heating process. Benefitting from the physical dual cross-linked network, the resultant composite hydrogels exhibited high mechanical properties (ultimate tensile stress of 1.01 MPa with a failure strain of 1500 %, high toughness of 6.28 MJ m^-3), good self-healing ability and 3D printability. Moreover, a conductive hydrogel can be easily obtained by in-situ silver mirror reaction during the heating process, which enable the hydrogel to be used as a wearable sensor to monitor human motions with high gauge factor of 2.027 and good durability (1000 cycles). Taking the advantage of its printability, electronic glove (E-glove) has been easily prepared by printing the precursor sol directly on the glove and successfully used to detect the hand motions exactly. This work provides a new route for the fabrication of multifunctional hydrogels with high performance and opens a new road for designing complex wearable sensors to monitor human motions.

Characterization of acid hydrolysis based nano-converted mung bean (Vigna radiata L.) starch for morphological, rheological and thermal properties

Mung bean starch nanocrystals (SNC) were fabricated using acid hydrolysis. The resulting nanocrystals were studied for their morphological, thermal, and rheological properties. Irregular or round-shaped nano-scale crystals with average hydrodynamic diameter of 179 nm obtained after acid hydrolysis. The mung bean SNC revealed a C_B-type crystalline pattern with enhanced crystallinity as studied by X-ray diffraction (XRD). Lower negative zeta potential was obtained for mung bean SNC as compared to its native starch. Thermal peaks disappeared for nanocrystals, which indicated an increased thermal instability of mung bean SNC. A shear-thinning behavior, even at high concentrations of SNC in the suspension was noticed. The elastic behavior was observed at all studied concentrations and it was independent of the frequency change.

Enhancement of the water-resistance properties of an edible film prepared from mung bean starch via the incorporation of sunflower seed oil

Mung bean starch (MBS)-based edible films with incorporation of guar gum (GG) and sunflower seed oil (SSO) were developed in this study. MBS, GG, and SSO were used as the main filmogenic biopolymer, thickener, and hydrophobicity-imparting substance, respectively. To investigate the effect of SSO content on the physicochemical, mechanical, and optical properties of the films, they were supplemented with various concentrations (0, 0.5, 1, and 2%, w/w) of SSO. Increasing SSO content tended to decrease tensile strength, elongation at break, crystallinity, water solubility, and the water vapor permeability; in contrast, it increased the oxygen transmission rate and water contact angle. Consequently, the incorporation of SSO into the matrix of MBS-based films decreased their mechanical strength but effectively enhanced their water-resistance properties. Therefore, the MBS-based film developed here can be properly used as an edible film in settings that require high water-resistance properties but do not call for robust mechanical strength.

Effect of Controlled Hydrothermal Treatments on Mung Bean Starch Structure and Its Relationship with Digestibility

The changes in structure and digestion properties of mung bean starch due to hydrothermal treatment at various controlled temperatures were investigated. Results showed the increase in onset temperature (T_o) from 66.33 °C to 76.69 °C and decrease in enthalpies (∆H_g and ∆H_r) until the starch was completely gelatinized. The degree of molecular order (DMO) and degree of double helix (DDH) were significantly (p < 0.05) reduced from 1.35 to 1.01 and 1.38 to 0.98 respectively. X-ray diffraction (XRD) indicated the consecutive decrease in relative crystallinity (RC) while RVA analysis showed that peak and final viscosities were decreased significantly (p < 0.05). However, digestion kinetics indicated that degree of gelatinization increased the access of enzymes. As starch was partially gelatinized it yielded significantly lower glycemic index but no significant (p > 0.05) change in starch digestibility was observed after 70 °C. Hence, 70 °C can be considered as the critical hydrothermal treatment temperature in mung bean starch. Pearson's correlation analysis indicated that controlled hydrothermal treatment had negative effect on the DMO, DDH, RC and the granular damage increased vulnerability of mung bean starch to digestion. These findings gave insight into sequential changes in the structure and digestibility occurring during gelatinization process due to hydrothermal treatment. Controlled gelatinization in mung beans at 70 °C is useful and must be employed to produce the foods with lower starch digestibility.

Moth bean starch (Vigna aconitifolia): isolation, characterization, and development of edible/biodegradable films

In the current work, moth bean starch was separated from the moth bean seeds which were cultivated in the semi arid regions of Haryana and Rajasthan, India using alkali treatment technique and characterized. Isolated and purified moth bean starch comprised (12.89-20.37%) amylose, 0.8% protein, 0.4% ash, swelling index and solubility were 10.8-14.7% and 6.4-9.8% respectively. For wrapping application, starch was modified using citric acid as cross linking agent (1-7% w/w of total starch) and film was made using casting method, and investigated the influence of citric acid on the functional properties of the films such as moisture content, solubility, swelling index, water vapor permeability and mechanical property. Significant difference in the functional properties among native and modified moth bean starch films was noticed. Interactions among starch chains due to cross linking in the modified starch films were reported using FTIR spectra. Surface micrographs of both purfied starch granules and films were studied using scanning electron microscopy. From the outcomes, it was exhibited that obtained starch granules has range large to small size with distorted cylinder and oval shapes. While cross linked starch films showed compact, slightly rough and homogeneous surface. Tested modified moth bean starch films containing citric acid (CA) and sorbitol were utilized as wrapping films to improve the shelf life of fresh lemon. Outcomes showed that the film contains 5% CA could be most promising wrapping materials for lemon that enhanced the shelf life of lemon additionally up to 12 days.