The Study of Thermal Reversibility of the Freezing-defrost Process of Browned Onion

The features and dynamics of the freezing-defrost processes of the studied sample of browned onion were established and studied. At the research it was revealed, that at freezing temperature –20 °С the value of maximal freezing speed does not change.The process of defrost of browned onion was carried out using calorimeter with the reverse connection on temperature and PID-regulator, on the temperature curve of its freezing. It was determined, that the process of defrost of the studied sample needs more heat that is educed at freezing. The modes of stepped defrost that testify to the possibility of thermal reversibility of freezing process were experimentally established.The direct dependence of educed and consumed heat quantity on the mode of thermal processing of studied sample was revealed. The more moisture was eliminated from the food product, the less heat must be consumed for defrost. The analogous dependence is typical also for the freezing process.The received data can be used for determination of the rational modes of freezing and defrost of the browned onion

Effect of Sautéing of Onion on Its Storage at Low Temperatures

We studied dynamics of freezing and defrosting of sautéed onion, determined its acidic and peroxide number, which was stored during 30 days at temperature of –18 °C. The change in anatomical structure of frozen onion depending on thermal pre–treatment was examined.The technology of production of frozen vegetable mixes implies the use of thermal treatment; therefore, selecting the method of canning, which will make it possible to maximally preserve useful substances of chemical composition of a product, is relevant.As the object of experiment we used fresh and frozen sautéed onionIt was found as a result that at temperature of freezing – 20 °C, the value of maximum speed of freezing practically does not change; this indicates that the rate of cooling is not limited by thermal and physical properties of the sample. We also experimentally determined the increase in acid number in the process of refrigeration storage during 30 days and the decrease in peroxide number in the examined samples of sautéed and frozen onion.It was revealed that the cells of onion after sautéing changed their form and structure: they do not have a clear form and orderliness; the breaks are visible at the contours of the walls of cells. The luminescent formations after sautéing of onion change their form as a result of deformation of cellular membranesThe obtained data may be used for providing high quality of the frozen vegetable mixes for soups and for determining rational regimes of freezing and defrosting of sautéed onion in their composition. Adding sautéed onion to the frozen vegetable mixes is expedient and will not change organoleptic properties of a product; it will not accelerate the oxidation processes of fats, but will only help to preserve the integrity of shape and delicate consistency of onion in a soup prepared from such a mix

Improvement of the Method for Producing Confitures From Fruit Raw Materials

The object of research is the method of production of comfiture from fruit and vegetable raw materials. The production of comfiture using traditional technologies is characterized by the loss of physiologically functional ingredients of raw materials. Such losses can reach up to 60 % of the initial amount, depending on the temperature regime and the duration of heat treatment. A negative factor in the storage of ready-made comfitures is sugar crystallization. Equipment for the implementation of traditional processes of processing fruits and vegetables is characterized by high productivity, low efficiency and operational difficulties. Boiling in the traditional way is carried out at high-temperature conditions, which leads to a decrease in the content of functionally physiological ingredients and the nutritional value of the resulting comfitures. In the production of comfiture on the basis of fruit and vegetable raw materials, the following recipe ratio of components was used: apple – 60 %; Jerusalem artichoke – 25 %; cornelian cherry – 15 %. The improved method is characterized by gentle heat exchange operations, in particular: drying is carried out in an infrared dryer at a temperature of 40–50 °C to a dry matter content of 30–40 %. And also by further boiling of the mass in a vacuum evaporator based on a flexible film resistive radiating electric heater (FFRREH) at 50–60 °C. The use of inverted syrup in the recipe during boiling prevents sugar crystallization during storage of the finished product. Comparative analysis of the heating kinetics of comfiture from fruit and vegetable raw materials confirms the reduction in the duration of reaching the stationary mode (55 °C) when using a vacuum evaporator based on FFRREH by 1.6 times, compared with an analog apparatus. Such a hardware-constructive solution will ensure a decrease in the consumption of energy resources with a simultaneous increase in the quality characteristics of products

Determination of the Heat Transfer Coefficient of A Rotary Film Evaporator with A Heating Film-forming Element

A model of a rotary film evaporator with a film-forming element with a reflective heated surface has been developed. This will allow stabilizing the hydraulic movement of the cut wave flow due to the reflective surface of the geometric shape for the forced direction of the cut raw material to the heating surface. Autonomous heating of the reflective surface additionally provides a temperature effect in the conditions of movement of particles of raw materials after cutting. The analysis of the experimental and theoretical parameters of heat transfer made it possible to substantiate the criterion equation for determining the heat transfer coefficient of an evaporator with the proposed film-forming element and a reflective heated surface for calculating the coefficient from the working surface to the raw material. The resulting equation takes into account the influence of the vertical component of the motion of the raw material film, centrifugal movement during the rotation of the film-forming element, mixing of the boiling film of the raw material with steam bubbles, and the geometric characteristics of the film-forming blade on the hydrodynamic flow of the raw material. The calculation of the rotary-film evaporator was carried out using the criterion equation and the obtained useful heat exchange surface – 0.75 m2. The specific metal consumption in a rotary film evaporator with a film-forming element having a reflective surface is 57 kg/m2, compared to the vacuum evaporator traditionally used in canning industries (410 kg/m2), which is 7.1 times less. The duration of the temperature effect on the raw material is also reduced: a rotary film evaporator – 200 s and 3600 s in a traditional apparatus. The data obtained will be useful for the design of rotary-film devices of different geometric parameters using articulated blades with a reflective plate