Extração e caracterização da mucilagem e de subprodutos da semente de chia (Salvia hispanica L.)

Abstract

Chia seeds (Salvia hispanica L.) are a natural source of Omega 3 fatty acids, antioxidants, proteins, vitamins, minerals, dietary fiber and mucilage. When immersed in water, the seeds produce a highly viscous solution because due to the release of mucilage, high molecular weight complex carbohydrates with wide application in the food industry. Thus, this study is about developing a new method for extracting mucilage of chia seeds based on mechanical processes at low temperatures, evaluating its performance, rheological properties, composition and structure, as well as by-products of the extraction process. For that, it was evaluated the chemical composition of the raw material (chia seed) of national culture from the city of Entre-Ijuís / RS, Brazil, as well as the yield of mucilage for different seed:water ratio. The new method is based on extraction by cold pressing and drying by lyophilization. Analysis was made of the chemical composition, color, rheology, microstructure (scanning electron microscopy/SEM), the mineral profile (X-ray microanalysis) and the fatty acid profile by chromatography of chia seed, mucilage and by-products. To evaluate the technological properties the capacity, stability and microstructure of the emulsion were assessed. The chia seed mucilage cultivated in Brazil was successfully extracted by the new method of extraction at low temperatures. The optimal process parameters occurred at 27 °C with seed: water ratio of 1:20, with yield of 8.46%. Overall, there was no statistical difference in rheological behavior (flow behavior index, viscosity and scan frequency), color and yield among the mucilage obtained in the seed:water ratio of 1:20, 1:30 and 1:40. These showed non-Newtonian behavior, with the Power-law model was the one that best explained the experimental data. The results obtained for chia seed composition are in accordance with its profile. The different extraction processes led to changes in the composition of mucilage and their by-products. In general, chia seed, its mucilage and byproducts had interesting properties for food industry, such as high levels of protein, minerals, fibers and polyunsaturated fatty acids, that can be used, for example, in bakery products, powdered drinks, ice creams, yogurts, among others. The SEM allowed the observation of macroscopic fibrous structure of mucilage obtained through cold extraction process, indicating that the macromolecular network formed by fibrous material contained in mucilage maintained its structure in the process of deep freezing and lyophilization. The Xray microanalysis made it possible to identify the mineral elements in chia seed and its byproducts. The extraction method did not significantly influence the emulsifying ability of gum, with an average of 98%. The mucilage obtained by cold extraction was more stable, with 45% of stability and droplets of disuniform sizes.