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The Influence of the Parameters of the Subcritical Water Extraction Process on the Efficiency of Isoflavones Elicitation from Soy Meal

Topicality. Incidental products of soy processing (okara, meal, millcake) contain a large amount of protein, and, additionally, other valuable biologically active substances. Among them, isoflavones are of particular researchers’ interest. Subcritical water extraction is a promising method for elicitation biologically active substances from plant raw material. However, such a method of extracting isoflavones, and its rational parameters for soy meal, remain insufficiently investigated.
Aim and methods. The aim of this work is to study the influence of parameters (temperature: 120...160°С, duration of extraction: 5...15 min, hydromodule: 1:15...25) of the extracting process of soy meal with subcritical water on the isoflavones content in the dry material of the extract. The empirical research method is applied, using the second-order orthogonal compositional outline for a fractional factor experiment. The samples of soy meal extract are obtained using the experimental setup, based on the high-pressure reactor “RHP-2-500”. The total isoflavones content in the dry extract material is defined in terms of gallic acid with absorption spectrophotometry method.
Results. Based on the obtained results, the quadratic interpolation model is constructed. This model links the total isoflavones content in the dry extract material with the extraction parameters. The analysis of the constructed model makes it possible to establish rational measures of extraction parameters.
Conclusions and discussion. In this study, the intensive growth of soflavones content in the dry extract with highing the temperature process, and a relatively small influence of the process duration on this indicator, were defined. The influence of the hydromodule is ambiguous. The lowest yield of isoflavones is noted at hydromodule ≈1:21,41. Its increase or decrease lead to the growth of isoflavones content in the extract. In this paper, for the first time, the existence of rational measures of parameters in the process of extracting isoflavones with subcritical water from soy meal is studied and established. The obtained results can be used in the elaboration of the technology for producing isoflavones enriched soy protein concentrate.