Aproveitamento tecnológico e compostos bioativos da semente de goiaba (Psidium guajava L.)

Abstract

During the change of fresh fruits for many manufactured products in industry, several coproducts are generated. In this context, studies have been carried on in order to investigate the nutritional value of these co-products, valuing them and suggesting new alternatives of use. Thus, the purpose of this study was to investigate the use of the seeds of guava (Psidium guajava L. var. Paluma) for the extraction of oil and also their potential use as flour in cookie formulation. Moreover, the phenolic content and antioxidant capacity of seeds were evaluated. After drying and grinding the guava seeds, they were used to determine the chemical composition and the characterization of both lipid and fatty acids profile present in the seeds. The analyses of phenolic content and antioxidant capacity by DPPH and FRAP methods were performed in nine extracts prepared with the seed. The guava seed flour was obtained by seed grinding and subsequent granulometric standardization, and then analyses of the physicochemical composition were performed. The viability of the use of seed as flour was verified through the production of cookies. Formulations with 10%, 30% and 50% of guava seed flour were developed, partially replacing the wheat flour. The cookies elaborated were evaluated regarding their chemical composition as well as physical, texturometric and color characteristics. The cookies sensory analysis, made with different guava seed flour concentrations, was performed by testing the ordering concerning the preference and acceptability. In addition, a review on the product purchase intention and the index calculation of acceptability were performed. The results showed the seed is a fiber-rich material, highlighting the high content of insoluble fiber. The highest oil yield was obtained for the cold extraction with a chloroform and methanol mixture. The fatty acids found in greater quantities for all the solvents used in the extraction were: the stearic, elaidic, linoleic and palmitic acids. However, the palmitic acid was absent in the extraction with petroleum ether. The hydromethanolic extract at a temperature of 50 °C exhibited both higher phenolic content and greater antioxidant capacity by the FRAP method. The guava seed flour presented humidity content according to the standard required by Brazilian law, and also high levels of protein, fat and dietary fiber, especially the insoluble fraction. The gradual addition of this flour to cookies increased lipid and dietary fiber content, and reduced humidity, carbohydrate and energy value. The weight and post-firing diameter, as well as cookies instrumental hardness increased according to the addition of guava seed flour, and their color became darker. The elaborated cookies presented acceptable sensory properties, and the percentage of substitution used in this study was accepted by the judges amongst all sensory attributes. In conclusion, the guava seed is an alternative ingredient for using a product that is usually discarded. The flour obtained from this co-product is an alternative to partially substitute wheat flour in cookies, in order to improve its nutritional value without interfering with the sensory characteristics.