RESULTS OF LABORATORY STUDIES OF THE EXPANDATE FORMATION PROCESS

Abstract

The expanded preparation of feeds is carried out using high-temperature (80–140 °C) expanders. These expanders perform the task of preparing food products and feeds under high pressure (1–10 MPa). The expansion process is accompanied by chemical changes such as denaturation of proteins, amino acids, vitamins, starch, and enzymes. Additionally, there is a transformation of the physical and mechanical properties of the feed components, converting them into expandates. The laboratory research aims to establish the regularities of the compression pressure changes with the deformation of feed components and the density of the obtained expandates under various technological parameters. The study explores the impact of the granulometric composition of the feed, its moisture, and temperature on the deformation diagram, representing the relationship between stress and material deformation. For this purpose, testing was conducted using the Heckert FP-100/1 testing machine and additional devices and equipment. As research factors, the feed's moisture W (10 %, 20 %, 30 %), temperature T (80 °C, 110 °C, 140 °C), and the average particle diameter of ground feed components Dμ (0.5 mm, 1.5 mm, 2.5 mm) were selected. The study was conducted using a full-factor experiment, comprising a total of 27 experiments with three repetitions. For each experiment, a relationship of compression pressure changes with deformation (elastic hysteresis) of the feed components ΔP(εz) was obtained. The research criteria include: the area SΔP enclosed inside the elastic hysteresis loop ΔP(εz); the coefficient of mechanical losses (or relative hysteresis) Ψ, calculated as the ratio of the hysteresis loop area SΔP to the area enclosed between the stress-strain curve and the abscissa axis, where deformations SP1 are plotted; the height of the obtained expandate sample ha; and the density of the obtained expandates ρa. As a result of the laboratory research on the expandation process, dependencies of the compression pressure changes with the deformation of feed components ΔP(εz) were established. Additionally, correlations of the area of the elastic hysteresis loop SΔP, the coefficient of mechanical losses Ψ, the height of the obtained expandate sample ha, and the density of the obtained expandates ρa with the feed's moisture W, temperature T, and the average particle diameter of ground components Dμ were determined. By solving the compromise task of minimizing the coefficient of mechanical losses Ψ and maximizing the density of the obtained expandates ρa, the following rational technological parameters were obtained, ensuring the most effective feed expansion process: Dμ = 0.5 mm, T = 119.2 °C, W = 19.1%, ρa = 292.9 kg/m3.