FI75429C - ANALYSIS OF FISHING AGAINST CRYSTALS AND CHARACTERISTICS HOS FETT. - Google Patents

Description

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Analytical method for the determination of the crystallization behavior of fat

The invention relates to an analytical method for determining the crystallization behavior of natural fats and fat blends, in which a DSC curve is measured and printed graphically by cooling a fat sample from a molten state to a fully or partially crystallized state and then heating the sample, usually to a molten state. By fat blends is meant here also fats and other substances e.g. mixtures of proteins 10 and / or water.

The DSC (differential scanning calorymetry) curve is obtained by measuring the heat of crystallization of fat fat, the temperature when calculating and raising the state Tn. In known devices, e.g. the Mettler TA 3000 System, this is done by measuring the temperature differences from the bottom of the sample cup and the reference cup when placed in dimension u directions, model DSC-30, whose temperature behavior is programmable. Since no crystallization occurs in the reference cup in the measuring range, it binds or releases only its specific heat of heat when heated or cooled. In a dynamic measurement, after reaching equilibrium, the instantaneous temperature difference between the fat and the reference sample indicates the binding or release of the heat of crystallization and in particular its rate, i.e. the heat of crystallization. The DSC device 25 actually controls the oven temperature and measures the temperature differences of the samples, from which the microprocessor calculates and converts the data into printed curves.

The aforementioned DSC curves have been known per se, but the physical background of crystallization is almost unknown. It has not been possible to draw any conclusions from the curves about fat-thinning behavior. According to the prior art, curves are considered worthless in some respects because they have no reproducibility. This statement appears in the professional literature.

3b In Whittam, J.H. and Rosano, H.L. "Physical

Aging of Even Saturated Monoacid Triglycerides "; Journal of the American Oil Chemists' Society, vol. 52, April 75, discusses the effect of aging of the pure fat component (monoacid triglycerides) on changes in crystal form. DSC heating curve series p. , in which the parameter has been an aging time at -26 ° C. The publication presents the use of DSC curves only to determine whether the test sample is aged or not, and has not sought a means of optimally obtaining a fat sample in a stable crystalline form. Clear.

The object of the invention is to provide an analytical method by which fat samples for the crystallization of fat 10 provide both useful information on the crystallization properties and directly control values to be set in the manufacturing process.

The characteristic features of the analytical method according to the invention appear from the appended claims. The invention cannot be utilized without new knowledge of the physics of crystallization. Substantial new information as a basis for the invention relates to the findings that the dynamic behavior of the heating or melting phase of the fat depends on the crystallization history, which can be utilized in the optimal crystallization of the fat. If the crystallization history of the fat sample is the same in different measurements, melting always takes place in the same way. The measurements are thus reproducible as long as the conditions and the crystallization history are kept the same. Another important piece of information for utilization is that the crystallization properties of the fat can be studied using heating curves measured from samples known in the history of crystallization. The most important result of the analytical method according to the invention is a picture of the effect of the crystallization history on the melting behavior. From this, the crystallization properties of the fat can then be interpreted.

The main basis of the invention is the findings on the general crystallization behavior of fats. The fat and also the crystallization of the fat blends starts in a crystalline form which is unstable at a certain temperature. Crystallization to the final densest crystal form occurs through at least one, often two or three non-permanent crystal forms.

35 If the fat cools too quickly, the volatile crystal form will not "melt" out of the way and will be retarded by final crystallization. Each crystal form often has its own melting range. The existence of a crystalline-inhibiting crystalline form 3 75429 can be seen from the heating curves e.g. so that in addition to melting, crystallization also occurs in the heating step.

The invention will now be described with reference to the accompanying drawings, which both illustrate the crystallization flask of the invention and present some of the results of the analysis according to the invention.

Figures 1a and Ib show curves of beef fat crystallization and melting rates as a function of temperature, i.e. DSC curves. Figure 2 shows the curtain surface of DSC curves of beef fat heating stage obtained as a result of the analysis method according to the invention graphically with the isothermal intermediate duration.

Figure 3 shows graphically the envelope of the DSC curves of the heating stage of beef fat obtained as a result of the analysis method according to the invention, in which the parameter is the temperature of the isothermal intermediate stage, T ^ sot.

Figures 1a and Ib are provided by the previously mentioned differential scanning calorimetry device, which is controlled by a microprocessor 20 first programmed to cool the fat sample from 65 ° C to 0 ° C (Figure 1a) and wait 10 minutes and then reheat the sample to 65 ° C: seen, (Fig. Ib). Cooling and heating of the chamber was performed at a constant rate. Crystallization and melting, i.e. the binding and release of the heat of crystallization, are observed from the temperature differences between the sample cup and the reference cup, and from these the heat of crystallization power, corresponding to the quantity, is calculated. The measurement results are stored on a magnetic disk, from which they are extracted after the entire series of measurements for calculation of / ^ kit curves and plotter printing.

30 For the exemplary fat, the cooling rate of 6 ° C / min seems to be too fast, since after a sudden onset of crystallization it slows down to almost non-existent for about 3 minutes. Alongside the temperature scale, the time scale must also be considered. Here, in particular, the time difference is more important 35 than the drop in temperature to 15 ° C, where, according to Fig. 1a, crystallization intensifies again. The slowdown in crystallization is apparently due to the fact that the first crystal form remains to inhibit the progress of crystallization.

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Figure Ib clearly shows the braking effect of the unstable crystal form. The heating step normally involves melting alone, but since the sample was not crystallized into its final crystalline form, the heating step is more complex. Figure Ib shows the endothermic side of the reaction, i.e. the area where the fat sample binds the heat of crystallization, i.e. the melt.

However, crystallization is also observed at about 34 ° C. This can be explained by the fact that the unstable and crystallization-inhibiting crystal form was melted off just before this point, whereby crystallization started again. At 34 ° C, the fat is still in the subcooled region, so there is still a need for the fat to crystallize here, which discharges as a strong crystallization peak. The novel crystallization physics underlying the invention has been described above. In particular, the fact that the crystallization history can be read from the heating phase curves is essential for the utilization of the invention. As a result of the analysis method according to the invention, e.g. to study the effect of changes in crystallization history on awkward and inhibitory crystal forms and to search for their melting areas. In the production process) the information obtained can be utilized e.g. so that cooling is interrupted at the temperature of the formation of the awkward crystal form.

Figure 2 shows the DSC heating curves of beef tallow after crystallization of the sample from 60 ° C to -5 ° C at a constant cooling rate of 6 ° C / min, but the duration of the isothermal intermediate step at 0 ° C has varied before heating 1 '. .6760 * (minutes).

; The longest isothermal time (6760 ') reflects the situation where the tallow has reached its stable crystalline form at 0 ° C, which shows that the shape of the DSC curve no longer changes even if the duration of the 30 isothermal phases is further extended.

Comparing the 1-minute curve with the stable fat curve referred to above (6760 ', i.e. about 5 days), it is observed that these differ very much from each other in the heating range + 5 ° C to + 43 ° C. Since the heating curve follows a dynamic 35 events and registers only the net reactot, i.e., the sum of the endo- and exothermic reactions, the following conclusions can be drawn from the differences between the curves.

s 75429 1) Melting in the range of +5 ... + 17 ° C in the 1 'curve is the melting of unstable crystalline forms and not the melting of any permanent form of triglyceride (TG), because in the region in the 5-day curve no corresponding melting occurs at all.

5 2) The crystallization in the range of +32 ... + 36 ° C in the l'-minute curve is either the transition of the unstable crystalline forms to the more stable crystalline form or the crystallization of the as yet uncrystallized TG (cf. Such intense crystallization during heating clearly reflects 10 how "internal friction" at too low temperatures may prevent the crystallization from progressing to a more stable crystalline form over long periods of time. In this example case, it is only in the 960 'or 16 h curve that the net reaction remains entirely on the endothermic side (melting side).

15 The strong exothermic phase in the heating curve (1 ') immediately after crystallization (6 ° C / min, from 60 ° C to 0 ° C) in the narrow temperature range of 32 to 36 ° C gradually shifts to lower temperatures when the isothermal duration extended. Up to 40 min, the exothermic phase remains above 30 ° C as a narrow peak, but then a wide crystallization zone in the range of 20 to 30 ° C is already visible, which at 100 'is the only broad crystallization step. In this case, only an endothermic reaction takes place in the range of 30 to 36 ° C, which corresponds to the melting of an almost constant (5 days) form in the same range. From 16 h to 30 h, crystallization apparently also occurs in the narrow zone of 21-25 ° C, although the net reaction no longer goes to the exothermic side.

The melting of the last, permanent state in the heating curve (5 days) must be considered only for the melting of the permanent crystal forms and no more crystallization occurs during the heating. In this curve, no melting occurs in the range of 5 ... 20 ° C and melting in the range of 13 ... 20 ° C is negligible. Curves of less than 1 h (60 ') show two melting peaks between 5 ... 20 ° C, one 5 ... 13 ° C and the other 35 in the range 13 ... 20 ° C. In curves less than 10 ', melting between 5 .. .13 ° C is at its peak and from 40' to more than 30 h 13 .. .20 ° C melting is more dominant, being the only melting towards the end. At about 15 ', the meltings in both regions are approximately equal.

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The curves in Figure 2 are seen; when the tallow is heated from a state where it has not yet reached its final permanent crystalline form. the meltings at the lower end of the curve at temperature are meltings of the unstable crystalline forms and the subsequent crystallizations are in question. the transition of unstable crystal forms to more stable states. The melting at the end of the curve is the melting of these permanent states.

When tallow is heated from a steady state, all melting is the melting of permanent crystalline forms.

10 Keeping the sample at a constant temperature, eg 0 ° C, and monitoring the transition of the crystals to stable forms as a function of time, we can see how the unstable crystalline forms melting at 5 ... 13 ° C have transitioned to more stable forms by prolonging the isothermal time alone, the "crystallization peak" disappears from the heating curve. This happens in the example at about 40 min to 60 min. When melting is no longer observed in the range of 13 to 20 ° C, no signs of an exothermic mixture appear on the heating curve. In the example, this only happens sometimes after more than 20 to 30 hours.

From this it can be concluded that in the exemplary case, if the crystallization step is not extended to 0 ° C, but is stopped, e.g., to + 20 ° C, the crystallization proceeds much faster, because then crystalline forms causing "internal friction" cannot be formed. In the case of initial crystallization, the most preferred temperature range would be 32 to 36 ° C, but in order for crystallization to begin with rapid cooling, the temperature must first be lowered below 33 ° C (see Figure 1a).

Figure 3 shows graphically the effect of the 10 minute isothermal intermediate temperature, T ^ sot, placed in the crystallization history on the crystallization of a bovine fat sample. It can be seen from the figure that a 10 minute break in the range of 25 to 35 ° C during the crystallization of the fat is sufficient to remove the awkward and otherwise crystallization-inhibiting form of crystal-35.

When making margarine with continuous tube coolers, the isothermal phase cannot be extended for very long periods of time. 10 min represents such a practical rest- 'i Λ,:. .

7 75429 kaa in the process. Figure 3 shows the heating curves of beef tallow 0 ... 60 ° C (6 ° C / min), when the sample is crystallized at 6 ° C / min to 60 .. .0 ° C, an isothermal phase of 10 min in different heating conditions 0 ... 36 ° C in one degree S increments.

Exothermic crystallization occurs during heating, indicating that the sample crystallized into an unstable crystalline form, according to Figure 3, in the event that the isothermal phase of the sample is between 0 and 18 ° C or above + 32 ° C, with no crystallization during 10 isothermal phases ( the latter phenomenon is hidden in Figure 3 in the background).

Figure 3 clearly shows that the 10 minute isothermal phase in the middle of the crystallization is in no way long enough for the crystallization to be more stable than these forms. This is seen from the melting event in the range of 5 to 18 ° C, where there was no significant melting in the case of the steady state.

Optimal crystallization refers to bringing a sample to or near its more stable crystalline form as quickly as possible, or at least within the time available in the process.

It can be seen from Figures 1-3 of the analysis that the sample fat is difficult to crystallize, so that the rapid cooling process does not provide optimal crystallization. 25 Thus, there is no need to test this in the actual production process. By comparing the DSC curve measured from a single batch in Figure 1a with previous curves for the same raw material, any necessary changes in process conditions (e.g. cooling temperatures and / or times) can be predicted. In practice, it has been found that a single batch may differ significantly in crystallization properties from other batches of the same raw material, although there is no otherwise detectable difference in quality.

According to the invention, the meaningful temperature of the isothermal intermediate 35 is in the range from 0 to 45 ° C, since in this range the melting zones of the different crystalline forms of the fats are located. The range + 10 ° C to 30 ° C is especially important for the margarine production process. When an intermediate stage is set in this range, it can even be assumed that the analysis describes the production process, i A, *. 1

Claims (4)

8 Claims 7 5 4 2 9 An analytical method for determining the crystallization behavior of natural fats and fat blends, in which method S measures and graphically prints DSC curves when cooling a fat sample from a molten state to a fully or partially crystallized state and then heating the same sample, usually to a molten state, characterized by two or more cooling and a series of measurements comprising heating, in which the duration of the isothermal intermediate in the cooling phase at a certain temperature, tisot or the temperature of the isothermal intermediate of a certain length are always the same, and that the isothermal intermediate stages of the cooling phase 0 ... 45 ° C., The analysis method according to claim 1, wherein the parameter of the measurement series is the temperature of the isothermal intermediate phase, T ^ sot, characterized in that the curtain surface of the DSC curves is printed graphically at least from the heating phase. The analysis method according to claim 1, wherein the parameter of the measurement series is the duration of the isothermal intermediate phase, t ^ sot, characterized in that the curtain surface of the DSC curves is printed graphically at least from the heating phase. Analysis method according to Claim 2 or 3, characterized in that those parts of the surface curves which, at an axonometric viewing angle, are covered by other parts of the surface are not printed in a graphical representation. 35 t Λ, t *.