Professor S. V. Lebedev and M. P. Parfatskaya.

Heat of Thawing of Sugar Beet

The idea of a sugar industry in Siberia is now being put into real life, taking concrete form in the Altai sugar factory now under construction. In connection with this, a number of questions of a production character arise for Siberian industry, as a consequence of the distinctive climatic conditions of Siberia. One of the characteristic features of the latter is its long cold winter, which makes it possible to store the sugar beet processed at the factory in a frozen state. The effect of prolonged freezing of sugar beet has already been examined in a special work by S. V. Lebedev and V. P. Chekhov, which led to the following conclusion of interest in the present case:

“The sugar-beet root, when subjected under the natural conditions of the Siberian winter to the prolonged action of steady cold, undergoes profound changes. At the same time, ruptures appear in the root in its parenchymatous tissue between the vascular-fibrous bundles. The size and number of these ruptures increase with time. Masses of ice of pure water, which initially appear in the intercellular spaces, gradually increase with time, forming elongated accumulations that penetrate the body of the frozen root. By January the sugar beet, under the action of the natural cold of the Siberian winter, has already been transformed into a new material, completely unknown to European sugar production, differing in its biochemical, physical, and mechanical properties from ordinary sugar beet stored in an unfrozen state.”

The statement cited is of importance for many processes of sugar production and, in particular, for juice extraction, where the first task is the thawing of frozen beet, or more precisely of its beet cossettes. Without touching here upon the various aspects and technical conditions of carrying out this task, in the present case we shall dwell only on the question of the quantity of heat required for thawing frozen beet. It is evident that this expenditure of heat will be an addition to the normal expenditure under ordinary conditions of work with unfrozen beet. At the low temperatures of the Siberian winter, this new component of heat expenditure in a Siberian sugar factory may be quite considerable. In view of this, it appears necessary to determine its magnitude, as a new item in the heat balance of juice extraction when working with frozen beet.

The sugar industry, working under normal conditions with unfrozen beet, has hitherto been interested in its heat capacity only at temperatures above 0°. Its magnitude, as determined by various authors, has fluctuated around 0.85–0.87. The divergence of individual statements in this respect is quite natural, since the composition of sugar beet is very variable. The content in it of pulp, sugar, non-sugar substances,

...of sugars, water is very variable, depending on climate, soil, vegetation conditions, degree of maturity, duration and conditions of storage of the beets, etc.

The temperature of sugar beet also affects the magnitude of its heat capacity. This should be especially noticeable at the temperatures at which ice forms in the beet during its freezing. The inevitability of this is determined, on the one hand, by the fact that the mass of the beet root contains about 70% water, and, on the other hand, by the fact that the heat capacity of water at \(0^\circ\) is 0.9992 according to Regnault, whereas the heat capacity of ice at \(0^\circ\) corresponds to only 0.505, decreasing with a subsequent lowering of the temperature of the ice, as is seen from the data given below:

Under such conditions the heat capacity of frozen beet, owing to the considerable content of water in it, must of course be less than the heat capacity of unfrozen beet. It is obvious that the magnitude of the heat capacity of frozen beet, for many entirely understandable reasons, cannot be constant; moreover, one of these reasons lies in the fact that the quantity of ice present in the frozen beet depends on the depth and duration of its freezing.

The mass of the beet root is very complex and variable in its composition. Besides sugar, water, and pulp, it also contains a large number of substances differing in their physical properties, chemical nature, and amount: nitrogenous, non-nitrogenous, organic, and inorganic substances. The heat capacity of these constituents of the beet root appears to be very different, and for many substances has not yet been established. All this makes it impossible to solve theoretically the question of the heat capacity of frozen sugar beet on the basis of the established chemical composition and heat capacities of its constituent substances.

This problem is all the more difficult because the quantity of ice from pure water frozen out of the cell sap of the beet, as well as the quantity, concentration, composition, and heat capacity of the portion of the cell sap remaining in the unfrozen state in beet kept at temperatures below \(0\), inevitably change depending on the degree and duration of freezing of the beet. All the foregoing indicates that the amount of heat required for thawing frozen beet depends on many conditions and is very difficult to account for. At the same time, it should nevertheless be expected that the heat capacity of beet frozen under the conditions of a Siberian winter must be somewhat different from the heat capacity of sugar beet that has only accidentally and briefly been subjected to freezing in ordinary clamps in beet-sugar regions of a temperate climate.

The total amount of heat required for thawing frozen beet shavings is composed of the following: first, of the heat expended on heating the entire mass of frozen beet from the initial temperature to the melting temperature of the ice contained in it;

second, of the quantity of heat going to the melting of the ice and, finally, of the quantity of heat necessary to warm the entire mass of thawed beet to the final temperature. The principal component of the total quantity of heat expended in thawing frozen beet is the latent heat of fusion of the ice contained in it. In dwelling on this question, one may note the following, according to the indications of Khvolson*:

“Latent heat must depend on the temperature at which the transition of a substance from one state to another occurs. The phenomenon of supercooling indicates the possibility of a change in the solidification temperature, defined for water as the freezing temperature....” If the melting temperature is lowered by one degree, then the latent heat \(S\) decreases by \(C_1 - C_2\), i.e. by the difference between the heat capacities of the liquid and solid body; moreover, for all the substances investigated \(C_2 > C_1\), so that \(S\) always decreases with a lowering of the melting temperature. In the notation adopted: \(C_1\)—the heat capacity of the solid body, \(C_2\)—the heat capacity of the liquid body.

In addition to the foregoing, it is also of interest to note the considerations of Rubinstein cited below:**)

“Living tissues usually freeze only with very strong supercooling. The temperature of a muscle, for example, can be lowered to \(-10^\circ\) C, sometimes even to \(-18^\circ\) C, and only after this does it suddenly begin to solidify, the temperature rising to the freezing point of the organ, which lies only a few tenths of a degree below zero. The same considerable and variable coolings are required for the freezing of whole animals. Bakhmetev’s experiments show that in one and the same species of butterfly freezing occurred in some cases beginning at minus \(2.1^\circ\) C, and in others at minus \(12.9^\circ\) C. Under such conditions the determination of the true freezing point becomes extremely inaccurate. In quite a similar way, a solution outside an organism, in thin capillary vessels, may be supercooled. In a capillary cross-section of \(0.4\) mm, water remains liquid at minus \(7^\circ\) C and even at minus \(10^\circ\) C. With increasing capillarity, the degree of supercooling necessary for freezing also increases. Capillarity at the same time lowers the freezing point of the solution itself. The distribution of solutions present in the organism not as continuous masses, but in small capillary tubes and cavities, constitutes an important protective means, protecting them in winter from freezing. The larger the caliber of the vessel, the less does it hinder the freezing of the liquid contained in it. As a consequence of this dependence of freezing on capillarity, the endurance of cellular structures under supercooling increases as their dimensions decrease. Supercooling is eliminated by introducing into the solution an ice crystal, which serves as a center of crystallization. Under normal conditions the cell membrane prevents the penetration into the cell of such centers of crystallization. When it is damaged, the cell readily freezes through.”

In this connection it should be noted that the phenomenon of supercooling due to capillarity, of course, also takes place in the freezing of sugar beet; but since its roots, depending on a whole series of diverse conditions, may in this respect be unequal—

) Khvolson, Textbook of Physics, vol. III, p. 512.
) Rubinstein, Introduction to Physico-Chemical Biology*, pp. 14–15.

…therefore the freezing temperatures of beet may in individual cases differ appreciably.

The uncertainty of the freezing temperature of beet introduces still another difficulty for the possibility of a theoretical calculation of the quantity of heat required for thawing frozen sugar beet. Under such conditions, in resolving this question it appears necessary to proceed experimentally, which is the task of the present work.

Let us first consider the setting and conditions under which the sugar beet was prepared for the experiments.

The material for the investigation was frozen beet obtained from the Barnaul district, Aleisk region (the site of construction of the Siberian sugar factory). The beet was transported by rail in wooden boxes. The dates of dispatch of the beet were December 30 and February 8.

In Tomsk the frozen beet was stored in boxes in a cold room—a wooden shed.

The temperature of the shed corresponded to the temperature of the outside air, so that the beet did not undergo thawing during the winter. Experiments with the beet were carried out over the course of three winter months: December, January, and February; the temperature of the outside air during this time, according to data from the meteorological station of the Siberian Technological Institute, was as follows:

For preparing the beet for the experiments, a special cellar at the Laboratory of Nutrient Substances of the Technological Institute, built in 1928, was used. This cellar is a separate stone structure adjoining the outer wall of the laboratory, sunk 1.5 meters below ground level, and has two separate rooms: first, an unheated laboratory; second, an inner reinforced-concrete chamber for storing beet, surrounded by an air space separating the walls of the chamber from the outer walls, ceiling, and brick walls of the cellar, set back from them by a distance of one meter. The cold laboratory is separated from the reinforced-concrete chamber by a thick brick wall, being connected with it by double doors, covered with felt, cloth, and oilcloth, leading into the chamber. Temperature fluctuations with such an arrangement were very slight.

The mean temperature in the cellar rooms during the performance of the experiments was as follows:

The preparation of the frozen beet was carried out in the following order: the beet, as needed, was transferred from the above-mentioned outdoor wooden shed into the chamber, where it remained for a short interval of time, about 15 minutes, while the apparatus for the experiment was being prepared. In the cold laboratory everything necessary for grinding and weighing the beet was placed, i.e. a cutter and grater, balances with weights, desiccators with dishes, etc.

All the apparatus was kept constantly in the cold laboratory and had the temperature of the air present there. The beet was first cleaned of dirt by means of a dry brush, then finally wiped clean with a dry towel, after which it was converted into shavings; the cutting was done with the aid of the knife of a factory beet slicer, placed in a knife frame and set for a shaving thickness of 5 mm. Some of the experiments were carried out with beet pulp; in this case the beet was converted into pulp on a coarse grater. The preparation of the beet for the experiments and its conversion into shavings were done by hand, with special double thick mittens worn in order to eliminate, as far as possible, warming of the beet. From the total quantity of shavings prepared in this way, thoroughly mixed, a sample was taken for the calorimetric investigation and a sample for analysis, carried out for the content of water, sugar, and proteins. For the calorimetric determination, the beet shavings were weighed out in an amount of 50–100 g, with an accuracy of 0.1 g, into a special aluminum dish, previously weighed together with a glass rod; then the beet, together with the dish and rod, was placed in a small desiccator with a thermometer for low temperatures. The thermometer was fixed in the lid of the desiccator, in the middle of which there was an opening, and was immersed with its mercury bulb in the mass of beet shavings, so that the thermometer readings corresponded to the temperature of the cooled beet shavings. The desiccator had an open side tubulure. The desiccator with the beet was quickly carried out into the open air, the tubulure was opened, and from time to time the temperature of the shavings placed in the desiccator was observed. The entire operation of grinding and weighing the sample before cooling it in the open air was performed within 15–20 minutes.

Thus, all the work of grinding and preparing the shavings was carried out at a low temperature with apparatus that had been previously cooled; and if, in doing so, a brief partial warming of the shavings did occur—unavoidable even under these conditions, since the beet was brought from an outdoor room with a lower temperature than in the basement—then this warming, after the shavings had been obtained, was eliminated by subsequent cooling of them in the desiccator in the outside air, where the shavings assumed a lower temperature. The tempering of the shavings in the outside air continued for 4–5 hours, until the beet had assumed a completely stable temperature. During the first three or four hours the fall in temperature proceeded rather rapidly, but as the beet cooled its temperature fell more and more slowly, until it began to change by half a degree per hour. The final temperature of the shavings was taken to be one that differed from the temperature of the outside air by one degree C. It was not possible to obtain beet with a temperature equal to that of the outside air.

In this way the beet shavings were prepared for the experiment.

The determination of the quantity of heat required for thawing frozen shavings was carried out in a Regnault calorimeter by the method of mixtures. This determination was conducted at a room temperature of 17–20° C. The room in which the experiments were performed was the reading room of the Laboratory of Nutrients—a small room with a stable temperature. No other work was being carried out in this room; there were no gas burners, and sharp air currents—drafts, fans, etc.—were absent. The calorimeter was placed on a separate table.

The Regnault calorimeter with which the experiments were carried out consisted of a brass cylindrical vessel with ebonite insulating supports, with a capacity of 1000 cm³, a copper stirrer, and a thermometer graduated in 0.1°. The brass calorimeter was placed in a double-walled metal vessel, covered on the outside with insulating felt; the space between the walls of this vessel was filled with water. On top, the calorimeter was closed with a lid, likewise covered with an insulating layer. In the middle of the lid there was an opening in which the thermometer was fixed. Both the brass thermometer and its stirrer were weighed to an accuracy of 0.1 g.

The experiment itself was carried out in the manner described below.

Into the brass calorimeter, as the calorimetric liquid, a definite weighed quantity of kerosene or water was poured, weighed to an accuracy of 0.1 g, at room temperature of 15–18° C. The liquid (kerosene or water) was taken in an amount of 300 or 600 g, depending on the sample weight of beet taken and its temperature, and also because the heat capacity of kerosene is half that of water.

The tempering of the liquid continued for 2–3 hours, until it assumed the stable temperature of the room in which the calorimetric determination was carried out.

After this, the beet shavings, cooled in the desiccator in the open air to its temperature, were transferred into the laboratory room, the desiccator tubus having first been closed. Having accurately noted, from the thermometer reading in the desiccator, the temperature of the shavings, and also having established the temperature of the liquid in the calorimeter, the beet shavings were quickly poured into the calorimeter liquid. The calorimeter was then closed with the lid and the liquid was subjected to continuous stirring. Readings during the experiment were taken every minute on the thermometer immersed in the calorimeter liquid, until the temperature began to rise quite uniformly and very slowly (approximately by 0.1° per minute). This uniform rise in temperature indicated that heat absorption had ended and that heating was occurring owing to the difference in temperature between the calorimeter and the air surrounding it.

After the end of the experiment, the aluminum cup that had contained the shavings was weighed again. Equating the quantity of heat lost by the calorimeter and the liquid to the quantity of heat received by the beet shavings, we obtain equation (I), by which we carry out the calculation of the heat balance:

\[ C_c p_1 (T - t_1) + S p_1 = (p_2 C_{\mathrm{ж}} + C_k p_3)\cdot (t_2 - T) + q = Q \ldots \ldots \ldots (1) \]

where:

\(p_1\) — weighed sample of frozen beet,
\(t_1\) — initial temperature of the beet,
\(p_2\) — weighed amount of calorimetric liquid,
\(t_2\) — initial temperature of the calorimetric liquid,
\(T\) — final temperature, or temperature of the mixture,
\(C_c\) — heat capacity of the beet,
\(C_{\mathrm{ж}}\) — heat capacity of the calorimetric liquid,
\(C_k\) — heat capacity of the calorimeter-stirrer,
\(p_3\) — weight of the calorimeter and stirrer,
\(S\) — latent heat of thawing,
\(q\) — correction for radiation (heat emission).

In this series of experiments the heat capacity of the beet was conventionally taken to be 0.87 both for the frozen and for the thawed beet.

Kerosene was taken with a heat capacity equal to 0.48. The latent heat of thawing \(S\) was calculated per 1 gram of the beet taken. In the experiments in which the percentage water content in the beet was determined, the latent heat of thawing was conventionally calculated per 1 gram of water contained in the weighed sample of beet.

In the experiment a correction was introduced for the zero point of the calorimetric thermometer in order to determine the temperature of the frozen beet. In addition, a correction was introduced for the calorimetric thermometer for its heat value according to the formula:

\[ q = v \times 0.46 \ldots \ldots \ldots \ldots \ldots \ldots (II) \]

Calculating the amount of heat going into the actual thawing of the beet, so to speak, the latent heat of thawing per 1 g of water contained in the beet, and taking the average of these data, we see that this amount of heat is equal to 40.5 calories. At the same time we may note that the amount of frozen-out water is not the same and depends on the conditions under which the beet was frozen.

Subsequently, for all experiments the water content of the beet was determined, and the latent heat of its thawing was calculated per 1 g of water contained in the beet. Since, in setting up the experiments presented in Table I, different beets were taken, it was therefore very difficult to ascertain the difference in the use of kerosene and water taken as the calorimetric liquid; and in order finally to clarify this dependence, a series of experiments was conducted in which two experiments were set up in parallel with kerosene and with water from one and the same beet sample. The results of these experiments are presented in Table III.

Considering these data, one can see that this dependence, if it exists at all, proves to be so insignificant that it is not possible to establish it from our data. Some experiments, as, for example, 54–56, 66–67, almost completely agree with one another.

Since, in addition to the frozen water, which has a dominant influence on the amount of heat required for thawing the beet, other constituent parts of the beet also play a role, therefore, in parallel with the calorimetric investigation, an analysis was also carried out for the content of the principal constituent parts of the beet, namely—sugar and

Table 1

Experiments in thawing frozen beet.

Experiments on thawing frozen beet of cellular structure.

Table II.

On average.

Experiments in thawing frozen beets

Table III

Table IV

Experiments on thawing of frozen beets

*) In experiments 69 and 70, the calorimetric liquid was water.

proteins. The analysis of sugar in normal juice was carried out by polarizing it; the analysis of sugar in the beet was conducted by the method of aqueous digestion. Protein nitrogen was determined by the Barnstein method and then converted to proteins by means of the conversion coefficient—6.25. The results of these experiments are presented in Table VI.

Considering these experiments, we see that the latent heat of thawing of beet, calculated per 1 g of water, decreases as the percentage content of sugar in the normal juice increases; thus, at 22.3% sugar in the juice this quantity of heat is on average equal to 44.4 cal., while at 19.9% sugar in the juice the quantity of heat spent on thawing already amounts to 49.2 calories. Proteins, which constitute a broad and diverse group, beginning with the higher proteins and ending with albumoses and peptones, form such a relatively small component part of the beet that it is very difficult to establish any dependence between their percentage content and the quantity of heat spent on thawing the beet.

A small group of experiments was carried out with frozen beet shavings in a cold laboratory at a temperature from minus 5° to minus 7°C, in order to determine the heat capacity of frozen beet shavings; it was assumed in this case that at these temperatures the beet shavings, previously cooled considerably below this, do not thaw, but only raise their temperature to the indicated limit. Kerosene served as the calorimetric liquid in these experiments. The results of the experiments are presented in Table V.

Table V.

Experiments to determine the heat capacity of frozen beet shavings.

Considering these experiments, we see that at temperatures from minus 5.7°C to minus 7.1°C (the final temperature of the mixture) the beet shavings already partially thaw, since the heat capacity of the beet in these cases turned out to be much higher than is theoretically possible.

In order to make it easier to orient oneself in the results of the numerous experiments performed, Table VI below gives a general summary of them by groups corresponding to the distribution of the experiments in Tables I—IV. For each of these groups, Table VI gives the mean temperatures, as well as the corresponding amplitudes of variation of the beet-cooling temperatures.

Data are presented in the same form also for the temperatures of the final warming of the beet in the calorimeter. In the same form are also shown the heat expenditures in gram-calories with respect to: first, the heat required for the overall warming of the frozen beet; second, the latent heat of its thawing, relating this value to one gram of beet; and, finally, the same revealed heat of thawing of beet is presented recalculated per one gram of water contained in this beet.

Table VI*).

From Table VI it is evident that in the experiments performed the mean cooling temperature of the beet varied by groups from minus 15° to minus 21.0°C, with a total temperature amplitude of cooling of the sugar beet from minus 5.0° to minus 35.0°C. The mean temperature of the final heating of the beet varied from 5° to 8°C, with a total amplitude from 1° to 14°C.

Comparing the data of the individual experiments in Tables I—IV, one can see that the total amount of heat going to thaw sugar beet that had remained frozen for a long time under the natural conditions of the Siberian winter, at temperatures of the frozen beet down to minus 35° and when heated to plus 14°C, lies below 64 calories per one gram of beet—

*) The numbers are given rounded—without decimal fractions.

which, under the conditions of the experiments carried out, corresponds on average to 50 cal. per 1 gram of beet.

The latent heat of thawing of sugar beet under the same conditions, but calculated per one gram of water contained in the beet, gives an average value of 45 calories, remaining in all the experiments performed below 55 calories.

The expenditure of heat for the overall warming of frozen beet is not always numerically in a correct dependence on the degree of cooling of the beet immediately before the experiment and on the height of its subsequent heating in the calorimeter. In individual cases rather considerable deviations from this dependence are observed, both in the direction of increase and in the direction of decrease.

The reasons for this, besides differences in the properties, composition, water content, etc., of the individual tested samples of sugar beet, must also be connected with certain other factors of a different character. One of these, under the conditions of the experiments under consideration, is the assumption as a general proposition for all experiments that the heat capacity of sugar beet at all temperatures both before and after 0° remains unchanged and equal to 0.87. Meanwhile, in reality, as was already clarified in the preceding exposition, this value gradually, and indeed very considerably, decreases with a lowering of the freezing temperature of the beet.

Under such conditions, the heat calculation giving the latent heat of thawing of the beet and the amount of heat expended on warming it is, naturally, not entirely correct. Moreover, this incorrectness increases with the lowering of the cooling of the beet, which to a certain degree explains some discrepancies in the results of individual experiments.

Another reason for the discrepancies among the obtained experimental data—namely, the absence in places of a logically correct dependence of the quantity of heat required for warming frozen beet on the depth of cooling of the latter immediately before the experiment—is determined by the fact that the quantity of ice actually present in the frozen beet at the moment of warming it in the calorimeter may, in individual cases, not always correspond to its temperature at that moment. This is explained as follows. The means of freezing the beet, and also of cooling it at individual moments of the experiments, was cold atmospheric air, into which the freshly cut and weighed sample of beet shavings intended for calorimetric determination was taken. For final cooling and tempering it was taken out for 3–4 hours, as already indicated above, into the outside air. Upon reaching the temperature of the latter, it was introduced directly into the calorimeter.

Thus, the calculated freezing temperature of sugar beet was taken to be its temperature, which at the same time was the temperature of the outside winter air at the moment the experiment was performed. It was assumed that this temperature determines the quantity of ice frozen out and present in the tested beet. Meanwhile, the quantity of ice actually contained in this beet is determined not only by the temperature of its three-hour cooling immediately before the experiment, but is established by the totality of the temperature conditions and by the duration of freezing of this beet in the out-

outdoor air during the entire period of its freezing preceding the moment of calorimetric testing.

The temperature conditions of the outside air are, in general, very changeable; in Siberia they are extremely rapid and are associated with sharp temperature jumps both upward and downward. It is obvious that, with changes in temperature, the amount of ice contained in the beet also changes to a certain extent. However, quantitatively these changes of ice in the beet, for a whole series of understandable reasons, cannot keep pace with the temperature changes of the outside air.

In this connection, the inevitability becomes clear of the discrepancy observed in some cases between the heat expended on warming frozen beet and the depth of its cooling.

Examples of such a situation may be provided by experiments Nos. 12, 13, 14, and 15, presented in Table I.

In experiment No. 13, at a beet temperature of minus 9° C, the amount of heat used for warming it is equal to 64.1 calories, while 45.0 calories are spent on thawing one gram of it. Moreover, these values turn out to be, respectively, considerably greater than in experiment No. 14, where the beet had a much lower temperature, corresponding to minus 29° C. The same discrepancy, though in other numerical values, is also observed when mutually comparing the results of experiments No. 12 and No. 15, when, at different cooling temperatures of the beet—namely, at minus 12° and at minus 26° C—the expenditures of heat for the general warming of the beet, as well as for the thawing of one gram of it, turn out to be, respectively, almost identical for these two experiments.

Several more such examples could be found, alongside which there are many cases illustrating entirely correct dependences of heat expenditures on the degree of cooling of the beet.

In general, however, it must be noted that the value of the degree of cooling of the beet nevertheless has a relatively small influence on the expenditure of heat used for general warming.

The reasons for this, it must be supposed, lie in the fact that the principal expenditure of heat goes to the thawing of the beet, more precisely, to the melting of the ice contained in it. And since this quantity is evidently established, under the conditions of the Siberian winter, rather soon after the onset of severe frosts, the quantities of heat expenditure for the general warming of the beet therefore do not fluctuate greatly and, on average, amount to 50 calories per 1 gram of beet, varying within rather narrow limits if one compares the averages for individual groups of experiments, as is presented in Table VI.

The same table, giving the latent heat of thawing of frozen beet, calculated per one gram of water, as an average of 45 calories, makes it possible to obtain an idea of how much water in the beet during the winter period, when it is stored in Siberia in the open air, passes into ice. This quantity is easy to calculate if one assumes that, on average, the beet contains 70% water by weight, and that the latent heat of fusion of water is 80 calories.

Under these conditions, for the freezing of the entire amount of water attributable to 1 gram of beet, there should have been expended

\[ \frac{80 \times 70}{100} = 56 \text{ calories}. \]

And since empirically this quantity is established, on average, for beets at 45 calories, the amount of water frozen out from one gram of beets must therefore correspond to

\[ \frac{45 \times 70}{56} = 56.3\% \]

of its weight.

Conclusions:

1) The degree of initial cooling of beet shavings has almost no effect on the magnitude of the latent heat of thawing of beets.

2) The amount of ice in frozen sugar beet is not constant and depends on the depth and duration of the beet’s freezing.

3) The amount of water freezing out in beets when they freeze under the conditions of the Siberian climate in the January–February period is close to half the weight of the beet.

4) With an increase in the percentage content of sugar in beet juice, the latent heat of thawing of beets, calculated per 1 gram of water, decreases.

5) When strongly cooled beets are warmed to temperatures of minus \(5^\circ\text{C}\)—minus \(7^\circ\text{C}\), partial thawing of frozen sugar beet already occurs.

Tomsk.
Laboratory of Nutritional Substances
Siberian Technological Institute.