Avaliação dos grãos de soja BRS 232 em diferentes safras

Abstract

Soybeas is one of the main sources of protein and vegetable oils in the world, and has substances beneficial to health, such as isoflavones, saponin, polypeptides, dietary fiber, oligosaccharide, and phospholipids. Its composition is influenced by numerous intrinsic and extrinsic factors throughout its cultural cycle, and also during storage, suffering interference from periods of drought, excessive rainfall, temperature extremes, and low light, which also affect its technofunctional characteristics. The objective of the work was to evaluate the characteristics of BRS 232 soybeans coming from different harvests. The soybean samples, BRS 232 from the 2015/2016 (S1), 2016/2017 (S2), 2018/2019 (S3) and 2019/2020 (S4) harvests, cultivated in the Ponta Grossa-PR region were donated by EMBRAPA Soja. Analyses were performed to determine the chemical composition (moisture, ash, total protein, lipids, total carbohydrates, phenols, antioxidant activity and isoflavones profile), instrumental analyses (Color, X-ray diffraction and pH) and technofunctional analyses (volume of swelling (VI), water and oil absorption index (IAA and IAO), water solubility index (ISA), soluble proteins, emulsifying activity (AE), emulsifying capacity (EC), emulsion stability (EE) and apparent density). The chemical and technofunctional analyses showed that they are closely related to compose the general characteristics of the products, where sample S2 presented the highest protein content, when compared to S3 and S4, which resulted in higher values of the lipophilic properties: emulsifying capacity, emulsifying activity and emulsifying stability. As well as the content of total dietary fiber, in larger amounts in sample S1, caused the highest water absorption index and the lowest oil absorption index. During storage, oxidative alterations occur, which resulted in a gradual decrease of total phenols and antioxidant activity, and the total isoflavones presented the lowest value in sample S1 and the highest in S4 (younger grains). The S1 grains presented more intense red color, greater color difference and lower pH. The crystallinity of the samples was also altered, because a low intensity peak, around 35º, was not perceived in the youngest sample, while the high intensity peak referring to cellulose, around 20º, was present in all samples. S3 and S4, had the highest percentages of soluble dietary fibers, and S1 had the highest content of insoluble fibers. With the passing of time the hydrophobicity increases, altering the techno-functional properties, corroborating with the other data there was also the behavior of protein solubility, which decreased in the older samples, especially S1, due to the morphological changes that occurred. In general, the results showed that the storage time influences the characteristics of soybeans, with morphological changes that affect their technological and structural properties.