Caracterização química, ação antioxidante e influência do consumo de grão de chia (Salvia hispanica L.) nos níveis glicêmicos

Abstract

Chia seeds have been consumed by healthy people and by those bearing pathologies around the world. To have scientific evidence on its beneficial properties and of the byproduct formed by it and, also, verify its influence in the glucose levels of healthy volunteers, this work aimed at characterizing the chia seed produced in Brazil and analyzing the hydrocolloid formed as byproduct, in addition to determining its antioxidant activity and the glucose index of a standard meal supplemented with this seed. Among the analysis performed on the chia seed are chemical composition, mineral content, pH, total soluble solids, titratable total acidity, total dietary fiber, as well as determining the contents of nitrate, oxalic acid and tannins. After 28 days of storage, it was verified that the content of total soluble phenolics and the antioxidant activity of the seeds were determined by DPPH and the β-carotene/Linoleic Acid system. The determination of the fatty acids and the amino acid profile were performed by gas chromatography. The organic acids were identified by high performance liquid chromatography. The levels of post-prandial glucose levels were evaluated based on the intake of the standard meal. The values of humidity, lipids, protein, crude fiber and nitrogen-free extract found for the chia seed and for the hydrocolloid-free chia seed were 6.49%, 30.22%, 22.78%, 11.45%, 22.9% and 8.13%, 26.93%, 27.71%, 9.5% and 24.34%, respectively. The minerals found in more elevated concentrations were potassium, phosphorus and calcium. The chia seed presented considerable concentrations of dietary fiber (45.37%), in counterpart, the hydrocolloid-free seed presented more elevated contents of dietary fiber (50.95%). The content of phenolic compounds on the chia seeds of day 0 (control) was of 488.8 mg.100g-1, no significant difference was observed in the remaining analyzed days. The potential of the chia seed sequestering free radicals was expressed as final extract concentration, necessary to inhibit the oxidation of the DPPH radical in 50% (EC50), with results from 0.75 to 0.94 mg.mL-1 between days 0 and 28. While the total antioxidant activity in the whole matter of the chia seeds, in different temperatures, evaluated by the β-carotene/Linoleic Acid system method, presented the highest concentration (1.60 mg.mL-1) in the control group. The contents of fatty acids determined for omega-3 and omega-6 were 565.08 mg/g and 175.14 mg/g, respectively. The glucose index of the standard meal and of the standard meal supplemented with 5 g of the chia seed was, respectively, 104.3 and 99.2.