Obtaining fermentable sugars and fiber concentrate from asparagus by‐product

Abstract

In this study, different solid–liquid extraction conditions to obtain fermentable sugars from an asparagus by-product were investigated to produce a fiber concentrate. To evaluate the effects of agitation, solvent:sample ratio and temperature, an experimental design was used and the maximum extraction conditions of reducing sugars (RS) were determined. The diffusion coefficient of sugars in water at different temperatures was obtained, as well as the thermodynamic parameters of the process. The materials obtained before and after the extraction were characterized as composition, technological properties, and functional groups. The results showed that, under the conditions evaluated, agitation had the highest influence on the RS extraction, followed by the solvent:sample ratio and temperature. The maximum RS content (~30 g 100 g−1 dry asparagus by-product) was obtained at 125 rpm, 60°C, 30 min, and solvent:sample ratio of 20 ml/g. The values for the diffusion coefficient were directly proportional to the temperature increase, and the extraction was characterized as endothermic, irreversible, and spontaneous. The infrared spectrum showed that RS extraction did not alter the functional groups present in the sample, but this treatment promoted the concentration of soluble and insoluble dietary fiber, improving the balance of these fractions and the technological properties. Practical applications The asparagus by-product used in this study is of interest because it has a high dietary fiber content. Maximizing the reducing sugars extraction is necessary since the high amount of these compounds makes it difficult to employ the material in the development of new functional products. In addition, the extract rich in fermentable sugars obtained has potential use in the alcoholic fermentation. Therefore, the use of eco-friendly solubilization techniques is of interest to improve the composition and properties of the fiber concentrate obtained after this process. In addition, the determination of the thermodynamic parameters of the process and the diffusion coefficient allowed a better understanding of the mechanisms that characterize the extraction.