Embalagens bioativas para alimentos a base de amido de diferentes variedades de arroz

Abstract

Starch is a polymer derived from plants that after extraction can be widely used for various industrial purposes in its native and / or modified form and it is currently considered a promising raw material for the development of edible and / or biodegradable packaging. Due to its applicability and practicality, rice is one of the most consumed cereals in the world, with high percentage of starch on its composition. The aim of this work was to extract and characterize starches from different rice varieties (white, red and black) and to develop and characterize edible and/or biodegradable films with the obtained starches. The extraction yield of white, red and black rice was 44.05, 47.05 and 35.74%, respectively. By scanning electron microscopy, which showed no impurities and chemical analyzes, which had a carbohydrate content above 83.0%, the efficiency of the starch extraction was confirmed. Red rice starch showed a higher percentage of amylose (25.75%) compared to others (18.61% for white and 20.02% for black). There was retention of the phenolic compounds of the raw material in the starches. Analyzing pasting properties of the starches, there was no change in viscosity for the first 3 minutes, but there was difference in the initial temperature, being 80.65, 79.10 and 88.80ºC for white, red and black rice starch , respectively. Black rice starch expressed peaks of lower intensities, observed by X-ray diffractograms, when compared to white and red rice starches. The starches have shown a high content of phenolic compounds, even after the extraction and drying process, and this content was different according to the solvents used, in which the water presented better performance. Less crystallinity was observed for black rice starch. After the extraction and characterization of the different starches, those were used for the elaboration of flexible films by the casting technique. The films have presented a homogeneous matrix and variation in the hue, with naked eye, as a function of the starch used. The change in the type of starch and plasticizer, or their concentrations, resulted in films with differences in thickness, water solubility, water vapor permeability and opacity. Films prepared with 5% of starch and 30% of sorbitol have showed phenolic compounds and antioxidant capacity, using the DPPH and ABTS methods, indicating that these can be considered bioactive packages, being suitable for food application.