The choice of parameters for vacuum freeze-drying of dry heat-sensitive material with predetermined properties
DOI: 10.21047/1606-4313-2017-16-1-18-24
UDC 637.182
Semenov G. V., Krasnova I.S., Petkov I.I.
Keywords: vacuum freeze-drying, temperature regimes, energy consumption, quality, comprehensive quality index.
UDC 637.182
The choice of parameters for vacuum freeze-drying of dry heat-sensitive material with predetermined properties
For citation: Семенов Г.В., Краснова И.С., Петков И.И. Выбор режимных параметров вакуумной сублимационной сушки сухих термолабильных материалов с заданным уровнем качества // Вестник Международной академии холода. 2017. № 1. С. 18-24
Abstract
The article deals with freeze drying of fruits (apples, pears, plums, melon) at the temperatures of moisture removal with phase transition from ice to vapor (from –10 oC to –35 oC) corresponding to the vacuum depth in dryers, and at different regimes for refrigerating machines and vacuum pumps operation. Before drying the layer of sliced fruits were placed on the pan and were freezed under forced convection at the refrigerating chamber at –20 оС. After refrigeration the raw material was placed into freeze drying unit. Drying temperature at sublimation stage varied from –10 to –35оС. The temperature of drying completion was 38–40 оС. The final moisture content of the samples was 1.5–2.2%. The sublimation temperature drop from –10 oC to –30 oC results in increasing drying time from 7.5 to 22 h. At the same time the content of ascorbic acid increases from 30% to 80% from the original one. Then, sublimation temperature effect on drying quality is proved. The lower temperatures of sublimation are shown to result in an increased general power consumption. At –10 оС it is 2.4-2.8 kWh/kg of removed moisture. Wham sublimation temperature drops to –30 оС specific power consumption increases up to 3.5-3.7 kWh/kg of removed moisture. The possibility of reducing the specific energyconsumption on the vacuum freeze-drying by adapting the installation design of drying devices and adapting the regimes of their work to the level of quality parameters necessary for the customeris shown.
Abstract
The article deals with freeze drying of fruits (apples, pears, plums, melon) at the temperatures of moisture removal with phase transition from ice to vapor (from –10 oC to –35 oC) corresponding to the vacuum depth in dryers, and at different regimes for refrigerating machines and vacuum pumps operation. Before drying the layer of sliced fruits were placed on the pan and were freezed under forced convection at the refrigerating chamber at –20 оС. After refrigeration the raw material was placed into freeze drying unit. Drying temperature at sublimation stage varied from –10 to –35оС. The temperature of drying completion was 38–40 оС. The final moisture content of the samples was 1.5–2.2%. The sublimation temperature drop from –10 oC to –30 oC results in increasing drying time from 7.5 to 22 h. At the same time the content of ascorbic acid increases from 30% to 80% from the original one. Then, sublimation temperature effect on drying quality is proved. The lower temperatures of sublimation are shown to result in an increased general power consumption. At –10 оС it is 2.4-2.8 kWh/kg of removed moisture. Wham sublimation temperature drops to –30 оС specific power consumption increases up to 3.5-3.7 kWh/kg of removed moisture. The possibility of reducing the specific energyconsumption on the vacuum freeze-drying by adapting the installation design of drying devices and adapting the regimes of their work to the level of quality parameters necessary for the customeris shown.
Keywords: vacuum freeze-drying, temperature regimes, energy consumption, quality, comprehensive quality index.
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