Rice proteins - Gum arabic coacervates: Effect of pH and polysaccharide concentration in oil-in-water emulsion stability.

In the context of replacing animal proteins in food matrices, rice proteins (RP) become promised because they come from an abundant plant source, are hypoallergenic, and have high digestibility and nutritional value. However, commercial protein isolates obtained by spray drying have low solubility and poor functionality, especially in their isoelectric point. One way to modify these properties is through interaction with polysaccharides, such as gum arabic (GA). Therefore, this work aims to evaluate the effects of pH and GA concentration on the interaction and emulsifying activity of RP:GA coacervates. First, the effects of pH (2.5 to 7.0) and GA concentrations (0.2 to 1.0 wt%, giving rise to RP:GA mass ratios of 1:0.2 to 1:1.0) in RP:GA blends were evaluated. The results demonstrated that biopolymers present opposite net charges at pH between 2.5 and 4.0. At pH 3.0, insoluble coacervates with complete charge neutralization were formed by electrostatic interactions, while at pH 5.0 it was observed that the presence of GA prevented the RP massive aggregation. Second, selected blends with 0.4 or 1.0 wt% of GA (RP:GA mass ratios of 1:0.4 or 1:1.0) at pH 3.0 or 5.0 were tested for their ability to stabilize oil-in-water emulsions. The emulsions were characterized for 21 days. It was observed that the GA increased the stability of RP emulsions, regardless of the pH and polysaccharide concentration. Taken together, our results show that it is possible to combine RP and GA to improve the emulsifying properties of these plant proteins at pH conditions close to their isoelectric point, expanding the possibility of implementation in food systems.

Effect of partial substitution of wheat flour by quinoa (Chenopodium quinoa Willd.) and tarwi (Lupinus mutabilis Sweet) flours on dough and bread quality.

Bread is the main important food product worldwide. In this study, eleven bread formulations were developed by partial substitution of wheat flour with quinoa and tarwi flours, to evaluate the effect on the rheological and pasting properties of mixtures, as well as on the physicochemical and textural properties of the final product. Partial substitution with quinoa flour generated similar thermomechanical and textural properties in the dough, and similar bread technological characteristics related to the control bread (100% wheat). In the case of tarwi, the increase in the concentration of this legume showed a negative effect on the bread quality parameters (specific volume, crumb porosity, textural properties, etc.). A negative technological impact of high percentages of wheat flour substitution by the mixture of both Andean flours was found, but it was contrasted with a positive effect on nutritional quality, particularly evidenced by a high content of proteins and dietary fiber. An optimal formulation considering technological and nutritional quality was obtained, presenting the maximum analyzed substitution level (13.35% quinoa flour and 6.65% tarwi flour). This study showed that these Andean grains are suitable for developing bread of good technological quality and improved nutritional profile, adding value to these underused ancestral flours.

Andean crops: kañiwa and tarwi flours used for the development of vegan gluten-free muffins.

BACKGROUND: The flours of two Andean crops, tarwi (Lupinus mutabilis) and kañiwa (Chenopodium pallidicaule Aellen), present an excellent nutritional profile for inclusion in vegan gluten-free muffin formulations. In this study, the proximal composition and techno-functional properties of tarwi and kañiwa flours, and the technological quality of batters and muffins (potato starch-based) formulated with 50% of these flours were evaluated. RESULTS: Andean flours have high protein, fiber, and fat content, and display high water and oil absorption. In premixes formulated with potato starch and Andean flours, a reduction in paste viscosity was observed due to starch dilution and lower water availability. Depending on their ability to interact with water, the batters formulated with these flours had a higher consistency. Confocal laser scanning micrographs showed that batters with Andean flours presented a complex matrix with dispersed starch granules surrounded by proteins and fiber fragments. Muffins made with Andean flours had a slightly lower specific volume than the control, but crumb hardness was not modified by tarwi flour (50%) and a mixture of tarwi (25%) and kañiwa (25%) flours. The intrinsic color of these flours modified crumb color, and their reducing sugar content also favored Maillard reactions in the crust. These color changes are desirable in gluten-free products because such products are frequently pale due to their high starch content. CONCLUSIONS: This study showed that tarwi and kañiwa flours are suitable for developing vegan, gluten-free muffins of good technological quality and improved nutritional profile, adding value to these underutilized ancestral flours. © 2022 Society of Chemical Industry.

Emulsifying properties of defatted rice bran concentrates enriched in fiber and proteins.

BACKGROUND: Rice bran (RB), a by-product of the rice milling industry, constitutes around 10% of the total weight of rough rice. The interest in the use of RB is centered on its nutritional quality, its low cost, and its extensive worldwide production. As RB is commonly used for oil extraction, the defatted rice bran (DRB) is obtained as a second by-product. The aim of this work was to obtain a defatted rice bran concentrate (DRBC), enriched in protein and fiber, from defatted rice bran flour (DRBF) and to determine its physicochemical and emulsifying properties. RESULTS: To obtain the DRBC, the starch was efficiently hydrolyzed (> 98%) with α-amylase and amyloglucosidase, with a concomitant increase in the proportions of crude protein (from 154.7 to 274.3 g kg-1 ) and total dietary fiber (from 276.1 to 492.3 g kg-1 ). Defatted rice bran concentrate exhibited a loss of protein solubility and increased surface hydrophobicity compared with DRBF. Defatted rice-bran concentrate dispersions with and without previous ultrasound treatment were prepared. The sonication led to an increase in the apparent viscosity. Emulsions were prepared with dispersions with and without previous ultrasound treatment and showed high stability in quiescent conditions over 28 days. However, the emulsions prepared with dispersions treated with ultrasound resulted in lower D4,3 values and higher elastic and viscous moduli. CONCLUSION: The rice bran concentrate can be used to obtain stable oil-in-water (O/W) emulsions, including both soluble and insoluble fractions, in acidic and neutral conditions. These innovative findings thus contribute to increasing the added value of this important by-product of the rice-milling industry. © 2019 Society of Chemical Industry.

Effect of salt content and type on emulsifying properties of hull soy soluble polysaccharides at acidic pH.

Hull soluble polysaccharide (HSPS) is a novel product consisting in a mixture of polysaccharides and proteins extracted from soy hulls by using a methodology based on the extraction of citric pectins. In this work we studied the effect of the addition of two different salts (NaCl and CaCl2) on the emulsifying properties of HSPS at acidic conditions. Low and high homogenization energies were used, obtaining coarse and fine emulsions, respectively. Mean droplet size, the stability against destabilizing processes (creaming, flocculation and coalescence) and the rheological properties of the emulsions were analyzed. Also, the rheology of the O/W interface was studied by using du Noüy ring geometry. Coarse HSPS emulsions were unstable to creaming, being more stable in the presence of salts. In contrast, fine HSPS emulsions showed long-term creaming stability similar to those performed with commercial citric pectin (CCP), although they differ in particle size distribution and flocculation degree. The presence of CaCl2 reduced the mean size of droplets in fine HSPS emulsions and improved their stability to flocculation and coalescence. Significant differences were observed in the rheological behavior of O/W emulsions and interfaces of HSPS and CCP with respect to the salt addition. Our results indicate that HSPS can be used in the formulation and stabilization of acidic O/W emulsions. Besides, HSPS generates emulsions with different characteristics than those obtained with citric pectins. The use of HSPS provides a suitable alternative in food engineering contributing to the exploitation and valorization of soy hulls, which represents an important waste material in soybean processing.