The thesis is devoted to the intensification of heat and mass transfer in order to develop energy efficient heat technology for producing chips from apples.
For the first time, the kinetics of adsorption of water vapor during dehydration to low final humidity was investigated for Renet Simirenko apples. Based on the obtained experimental data, the maximum hygroscopic moisture for apples was determined. Based on the analysis of the adsorption isotherm of the water vapor by the apple, the equilibrium state of the material at the given parameters and the conditions of packing and storage of the finished product were determined.
For the first time, the derivatographic method for the apples of the Renet Simirenko variety showed that in the scalded samples the redistribution of free and bound water occurred, part of the bound water converted to free water, which is confirmed by the values of the average specific heat of dehydration, which is set at the level of 2630 kJ/kg for fresh apples of the Renet Simirenko variety and
2500 kJ/kg for the blanched ones.
The average specific heat for the evaporation of water from apples in the studied range of humidity of the material, for fresh samples is 2550 kJ/kg, for steam-scalded samples – 2450 kJ/kg.
In order to determine the energy-efficient dehydration regimes, a study was conducted to determine the influence of the drying agent's thermal parameters on the drying process and the organoleptic characteristics of the chips on a convective drying stand, which is equipped with an automated system of collection and processing information.
Studies show that increasing the temperature to intensify the process, for thermolabile raw materials, is only possible until it reaches the maximum permissible temperature.
The analysis of the drying kinetics curves showed that, compared to the state low-temperature regime of 60 °C, the duration of the drying process is reduced under state conditions at temperatures of the drying agent 80...60 °C by 18% and at 100...80...60 °C by 21%.
For the first time, a study was conducted to determine the effect of different types of pre-treatment of apples on the drying process using the developed stage mode and on the organoleptic characteristics of fresh samples and chips. The kind of pre-heat treatment – scalding by steam at the temperature of apples t = 85...95 °С with holding of 30...40 s is scientifically substantiated.
In order to verify the correctness of the developed stage regimes and the quality of the chips, their reproducibility was investigated as one of the criteria for assessing the quality of the dried product. The reproducibility of the chips obtained from scalded by steam apples under the staged mode is the highest for both varieties and is 85...87%.
Studies have shown that the combination of steam scalding and the use of developed stage dehydration regimens are successful and economically feasible in obtaining chips.
In the thesis the numerical modeling of the process of drying of apples during the production of chips was performed.
On the basis of generalization of the results of experimental studies, energy-efficient thermal technology of obtaining chips was developed, which is based on the method of rapid convective drying of scalded by steam apples in the modes of stage dehydration. Unlike the world's developments, the technology involves the production of natural chips without artificial preservatives and fillers with the maximum degree of preservation of natural components of raw materials, the recoverability of which is 20...25% higher than existing analogues.
The chemical composition of fresh apples and the resulting chips was determined. The analysis showed that all components of the raw material were stored in the chips. Tasting evaluation, comparison of organoleptic parameters and the reproducibility of chips from different manufacturers, including chips obtained by the Institute's technology, were conducted. The chips developed by the heat technology obtained the preference for all indicators. The estimated cost of the chips made it possible to compare the cost of known analogues and chips obtained by the created heat technology.
The cost of chips in the trading network is 800...1100 UAH/kg. The cost of chips obtained by heat technology (taking into account profitability and retail mark-up) is 450...715 UAH/kg depending on the type of energy resources.
For the first time, technical specifications of Ukraine 10.3-05417118-053: 2016 “Fruit and vegetable chips” were developed, agreed and approved by Ukrmetrteststandart and technological instructions for production were developed. The innovativeness of the research results is confirmed by 5 patents of Ukraine.
