Strelchenko L. Improvement of the process of drying apple raw materials by convective-thermoradiation with a power supply

The Dissertation work is devoted to the improvement of convective-thermoradiation drying of apple raw materials. The work presents the results of research on the process of drying apples of the «Golden Delicious» variety using classical technology by thermoradiation, convective and convective-thermoradiation methods, as well as their energy analysis. The technology of apple snack production has been improved, preliminary preparation of apple raw materials has been studied and the duration of blanching has been established, which is 60…90 s with peroxidase activity of 4.55… 3.44%. The necessity of blanching apple particles in sugar syrup (with a sugar concentration of 30…40 %) with the addition of citric acid and antioxidant (ascorbic acid), which contributes to the partial osmotic dehydration of apples, is substantiated. The main factors influencing the process of drying apple snack, which include the concentration of sugar syrup in which the semi-finished product was blanched; temperature regime; power of thermoradiation emitters; coolant speed; specific load of the semi-finished product. The comparative analysis of the two-stage mode of drying of apple raw materials with obtaining dried apples, apple snack and candied fruits from apples is scientifically substantiated. Differential-thermal analysis is highlighted and heat and mass transfer characteristics for apple products are determined. Mathematical-statistical processing of the process of storing apple snack for which the optimization criterion is the content of ascorbic acid, derived an adequate regression equation. It is established that the main factors influencing the content of ascorbic acid are: coolant temperature, the amount of irradiation of thermoradiation emitters, the duration of storage of snack in the package and the activity of water during storage. Active packaging systems have been developed for the optimal way of storing apple snack, which allow to preserve the chemical composition of the product for 12 months. Two packaging systems proved to be effective: with the environment of the food gas mixture CO2:N2 in the ratio of 30:70 % and with the air environment with additional placement in both packages of the sachet-package of the oxygen absorber. A convective-thermoradiation drying unit with a heat pump has been developed. The principle-technological and hardware-technological scheme of making apple snack is made. Regulatory documentation for apple snack has been developed and approved (TU U 1.10 –02070938-217: 2018, TI U 1.10 –02070938-217: 2018). The economic effect from production on the convective-thermoradiation installation with the heat pump in comparison with the thermoradiation (prototype installation) is established. The production cost of dried apples produced on a convective-thermoradiation plant with a heat pump can be reduced by 3,148 UAH /t. The economic effect of the introduction of advanced technology for the production of apple snack in comparison with the classic production of dried apples. Net profit is 66,405 UAH/100 t. The developed convective-thermoradiation installation and technology of production of apple snack are tested in production conditions at LLC «Prodservice-IR». The results obtained during the dissertation were introduced into the educational process of training specialists in the field of «Food Technology and Engineering», as well as during the study of the discipline «Processes and Apparatus of Food Production».