Modificação do amido de arroz preto e vermelho por calor-umidade e aplicação como espessante em bebida láctea fermentada.

Abstract

A valuable energy source for human nutrition and processed foods is starch, which is the most abundant reserve carbohydrate in plants. Starch can be found in cereal grains, including rice, with a high potential for the formulation of products in industry. The thermal modification of starch by heat-moisture (HMT) is justified because it is characterized as a low-cost process that simulates the cooking process, in addition to the fact that types of rice with colored pericarp retain part of the phenolics responsible for the color, which increases the acceptability of the product after application in the dairy drink since they replace the use of artificial colorings. Therefore, this research aimed to evaluate black and red rice starch modified by heat-moisture as a thickener for a fermented dairy drink. The starches went through the heat-moisture modification process, heated to a temperature of 110 °C for 3 h to reach a final water content of 20%, with the aid of an electric oven (1200 W) and dried in an oven with air circulation at 50 ºC and air speed of 1.0 m s-1. To characterize the starch of the two types of rice, extraction yield, starch and amylose content, color, and phenolic compounds were analyzed using high-performance liquid chromatography (HPLC). Functional analyses were observed based on the processes of water and oil absorption capacity, absorption index of whole milk, and zero lactose and syneresis index. The structural analysis of the starches was carried out using Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) processes. In contrast, the morphological analysis was evaluated using scanning electron micrographs (SEM), and the texture profile was made following the TPA method. For the characterization and production of the dairy drink using starch as a thickener, the textural profile and proximate analysis (water, ash, protein, lipid, and total carbohydrate content) were observed. The values obtained were 52.06 ± 1.14% for the extraction yield, 12.11 ± 0.55 g/100g for the starch content, and 0.91 ± 0.09 g/100g for the amylose content. Functional properties of starches: The values obtained were 0.49 ± 0.04 for the water absorption capacity, 0.47 ± 0.02 for the oil absorption capacity, and 0.32 ± 0.06 for the absorption index of whole milk and zero lactose. Structural analysis of starches: The results showed FT-IR spectra and XRD diffractograms, indicating the structure and characteristics of the modified starches. The micrographs revealed the morphology of the modified starches, showing characteristics such as size, shape, and surface. This information is relevant to understanding the physical structure of starches and their potential for interaction with other components in food formulations. Texture profile of starches: The values obtained were 0.59 ± 0.05 N for firmness, 0.51 ± 0.08 N for stickiness, 0.42 ± 0.04 N for cohesiveness, and 0.33 ± 0.03 N for gumminess. Characterization of the fermented milk drink: The values obtained were 71.16 ± 1.08 g/100g for water content, 0.92 ± 0.14 g/100g for ash, 2.37 ± 0.15 g/100g for proteins, 0.30 ± 0.03 g/100g for lipids and 25.15 ± 0.28 g/100g for total carbohydrates. The color attributes of the drink were evaluated, obtaining values such as L 67.17 ± 0.01, a* -4.10 ± 0.52, and b* 18.63 ± 0.11. The use of modified black and red rice starches directly influenced these properties, providing a solid basis for the formulation of dairy products.