Effects of gellan gum and calcium fortification on the rheological properties of mung bean protein and gellan gum mixtures.

In this study, the effects of gellan gum types and CaCl2 addition on the rheological characteristics of mung bean protein (MBP)-gellan gum mixtures at varying protein contents (1-7 wt%) were investigated. Two types of gellan gum, high acyl gellan (HAG) and low acyl gellan (LAG), at 0.5 wt% were used. MBP-HAG system showed soft and elastic gels at below 3 wt% MBP content, but gel became weaker due to protein network disruption at higher MBP content. In contrast, MBP-LAG system exhibited a liquid-like behavior and a synergistic interaction between LAG and MBP. High calcium concentration can cause proteins to aggregate leading to protein precipitation. However, such phenomenon could be retarded by both types of gellan gum in the MBP-gellan gum mixtures studied herein. The calcium addition of up to 50 mM did not significantly alter the overall viscoelastic property of MBP-HAG system. In contrast, MBP-LAG system fortified with calcium formed solid gel at low protein content (1 wt%), but excessive calcium ions were required to maintain the strong gel characteristic at higher protein concentration (≥ 3 wt%) due to the competitive binding of calcium between the protein and gellan gum. These results were also supported by their microstructure observed through CLSM and SEM experiments. PRACTICAL APPLICATION: The application of hydrocolloids as rheology modifiers is useful to improve the stability and textural properties of plant-based protein drinks. Results from this study are helpful for the industry to understand the textural properties of mung bean protein at varying concentrations in the presence of gellan gum and calcium. Especially, at high calcium fortification which is desirable in plant-based protein drinks, protein aggregation could be retarded by gellan gum. Overall, the finding demonstrated that a range of rheological characteristics of mung bean protein and gellan gum mixtures could be manipulated as desired to meet both nutritional quality and product stability.

Studies on chemical composition, rheological and antioxidant properties of pectin isolated from Riang (Parkia timoriana (DC.) Merr.) pod.

Although synthetic antioxidant food additives are widely used in a variety of food products, some of them are suspected of having a noxious effect on human health. As a consequence, much research attention has been focused on developing natural antioxidant compounds from plants. Riang (Parkia timoriana (DC.) Merr.) is known as a traditional medicinal plant in which its various parts have been reported to exhibit antioxidant and numerous biological activities. In this study, pectins from Riang pod husk and pod powder were extracted, and their physico-chemical, rheological, and antioxidant properties were characterized. The extracted pectins showed high uronic acid content (> 65%) and high molecular weight (200-250 kDa) and the yields were approximately 15 and 36%w/w (dry basis), for Riang husk pectin (RHP) and Riang pod powder pectin (RPP), respectively. Furthermore, both pectins were classified as a high methoxyl with their DE of ~66%. Rheological measurements revealed a pseudoplastic behavior above 2% w/v. RHP contained higher content of total phenolics, flavonoids and tannin, compared with RPP. Antioxidant activities of RHP were consequently higher than RPP in all studied assays. The highest antioxidant activities of RHP and RPP, obtained from ABTS assay, were 0.95 and 0.24 mmol Trolox equivalents/g, respectively.

Physicochemical properties of starches and proteins in alkali-treated mungbean and cassava starch granules.

This study explored the influences of envelope integrity of cooked starch granules on physicochemical and thermophysical properties of mungbean and cassava starches. Alkali treatment was used to selectively leach amylose from the amorphous region of both starches and partially fragmented starch molecules into lower-molecular-weight polymers. It was found that despite the loss of 40% of the original content of amylose, both mungbean and cassava starches retained similar crystallinities, gelatinization temperature ranges, and pasting profiles compared to the native starches. However, the loss of granule-bound starch synthases during alkali treatment and subsequent alkali cooking in excess water played significant roles in determining granular disintegration. The alterations in envelope integrity due to the negative charge repulsion among polymers within the envelope of swollen granules, and the fragmentation of starch molecules, were responsible for the alterations in thermophysical properties of mungbean and cassava starches cooked under alkaline conditions.