JPH0662937B2 - Ultra-low temperature immersion freezing mixed brine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a mixed brine that can be used at an ultralow temperature necessary for freezing foods and raw materials thereof by an ultralow temperature immersion freezing method.

[Conventional technology]

Non-mixed brines conventionally used in the immersion freezing method include sodium chloride aqueous solution, propylene glycol aqueous solution, calcium chloride aqueous solution, ethyl alcohol aqueous solution and the like. Further, as the mixed brine, one obtained by adding sodium chloride or propylene glycol to ethyl alcohol is used.

[Problems to be Solved by the Invention]

The eutectic point of sodium chloride aqueous solution, which is an unmixed brine, is -21.6 ° C (23.2% by weight, hereinafter referred to as "wt%"), so the brine temperature is kept at -55 to -40 ° C before use. Needless to say, it cannot be used in the ultra-low temperature immersion freezing method. The concentration of propylene glycol aqueous solution is 60wt
%, The freezing point approaches −60 ° C., but since the viscosity increases and it cannot be used, the viscosity is at most 1.
The limit is a 43 wt% aqueous solution of 00 cp, and the freezing point is −
It becomes 23 ° C. The eutectic point of calcium chloride aqueous solution is -55.
Since it is ℃ (29.9 wt%), it can be used at a temperature higher than -50 ℃ as a limit, but it has a peculiar astringency, and if it adheres to food, its flavor may be significantly impaired. The eutectic point of the ethyl alcohol aqueous solution is -12.
Although it is 5 ° C (92.5 wt%), 60 wt% or more is regulated as dangerous goods by the Fire Service Law, and in Japan it is necessary to establish a special facility or a legal liaison such as establishing a dedicated handling chief. Have challenges. The freezing point of the mixed brine obtained by adding sodium chloride to ethyl alcohol is -35 ° C in the case of adding 40 wt% ethyl alcohol aqueous solution to 3 wt% sodium chloride, and the freezing point of 60 wt% ethyl alcohol aqueous solution to 3 wt% sodium chloride. For the added ones,
It becomes about -51 ° C. In other words, the freezing points of 40 wt% and 60 wt% ethyl alcohol aqueous solutions are −0.55 respectively.
Since the temperatures are ℃ and -43.5 ℃, the freezing point depressions of 4.5 ℃ and 7.5 ℃ can be obtained by adding 3 wt% sodium chloride, respectively. Since the freezing point of the mixed brine prepared by adding 3 wt% sodium chloride to 60 wt% ethyl alcohol aqueous solution is -50.1 ℃, if the temperature 5 ℃ higher than this freezing point is used as the lower limit, in this case the minimum brine temperature will be Is about -45 ° C. Therefore, in order to obtain a mixed brine that can be used at an ultra-low temperature below the temperature, the freezing point depressing is further attempted by increasing the amount of sodium chloride, but according to the experiment of the present inventors, the amount of sodium chloride is the amount of ethyl alcohol. In contrast, as the concentration of ethyl alcohol approaches 5 wt% and the concentration of ethyl alcohol becomes higher than 45 wt%, the phenomenon of poor solubility in sodium chloride appears, and sodium chloride 9 wt%
In addition, when the temperature is once lowered to the freezing point and the temperature is again raised, not only sodium chloride precipitates, but also the freezing point of the mixed solution tends to rise as the concentration of the ethanol aqueous solution becomes higher, which is higher than the freezing point of the ethanol aqueous solution itself. It was found to exhibit a freezing point. In other words, there is a limit to lowering the freezing point by adding sodium chloride, and there is a problem in concentration as mixed brine and temperature control. Next, the freezing point of a mixed solution of propylene glycol added to an ethyl alcohol aqueous solution is −52 ° C. for a 60 wt% ethyl alcohol aqueous solution to which, for example, 5% by weight of propylene glycol is added. Since it exceeds 100 cp, there is a problem that the heat transfer area of the heat exchanger increases and the power for flowing the mixed solution becomes large.

[Means for Solving the Problems]

In order to solve the above technical problems, the present invention provides about 45-
It consists of a mixed solution of 60 wt% ethanol aqueous solution and 9 wt% or less calcium chloride, and according to the present invention, the freezing point can be lowered to about -60 to -40 ° C, and the ultra-low temperature immersion has a small viscosity. It is possible to obtain a mixed brine for freezing.

〔Example〕

When the concentration of the aqueous ethanol solution and the amount of calcium chloride added are changed, the freezing point changes as shown in FIG. In the figure, A is an ethyl alcohol aqueous solution, and B, C and D are calcium chloride 3, 5 and
Represents a solution with 9 g added. As is clear from this figure, 4
The freezing points of 0 wt%, 50 wt% and 60 wt% ethanol aqueous solutions are -30.5 ° C, -38.0 ° C and -43.5 ° C, respectively, but 3 g / 100 g of 40 wt% ethanol aqueous solution,
The freezing points of the mixed brine containing 5 g and 9 g of calcium chloride were -34.8 ° C, -38.5 ° C, and -43.5, respectively.
The freezing points of the mixed brine obtained by similarly adding 3 g, 5 g and 9 g of calcium chloride to 100 g of a 50 wt% ethanol aqueous solution are -44.2 ° C. and -48.0, respectively.
2 ° C and -53.8 ° C. Similarly, the freezing points of the mixed brine obtained by adding 3 g, 5 g and 9 g of calcium chloride to 100 g of a 60 wt% ethanol aqueous solution were −50.1 ° C., −54.5 ° C. and −60.6 ° C., respectively. It was

From the above results, the freezing point decreases as the concentration of the aqueous ethanol solution increases, but the concentration of 60% or more is regulated as a dangerous substance by the Fire Service Act and handling is difficult, so the concentration of the aqueous solution is limited to 60%. Is appropriate. Similarly, as the amount of calcium chloride added to the aqueous ethanol solution increases, the freezing point decreases, but if the weight ratio to the aqueous solution is 9% or more, astringent taste is exhibited and the flavor of food is impaired. It is appropriate to set the upper limit to 9% by weight with respect to the aqueous ethanol solution. That is, in the present invention, a freezing point of about −60 to −40 ° C. could be obtained by using a mixed brine in which 9 wt% or less of calcium chloride was added to an ethanol aqueous solution of 60 wt% or less. Therefore, the mixed brine according to the present invention can be used at a temperature above the freezing point of 5 ° C. as a lower limit. Next, the physical property of brine, which greatly affects the performance of the heat exchanger, is viscosity. The viscosity of the mixed brine of the present invention is determined by the mixed brine temperature used, for example, -4.
It is 100 cp or less at about 5 ° C. and does not significantly impair the performance of the heat exchanger.

The usage of the mixed brine of the present invention will be described in detail with reference to FIG. Reference numeral 1 denotes a heat-insulated brine tank, which is provided with a conveyer 2 which conveys a frozen product 4 at an arbitrary speed from the right end to the left end of the blinder ink 1, and the brine is passed from the brine tank 1 through a brine suction pipe 7 to generate brine. The mixed brine 3 supplied to the brine cooler 6 via the circulation pump 5 and the brine discharge pipe 8 and cooled to an ultralow temperature of about −55 to −35 ° C. is again supplied to the brine tank 1 via the brine supply pipe 9. The product to be frozen 4 conveyed by the conveyor 2 in the brine tank 1 is frozen. When the temperature of the mixed brine is kept at −50 ° C. in the tank name and the product 4 to be frozen, for example, a film-wrapped food, is frozen, the freezing time is 50% or less and the energy consumption is 45% or less as compared with the air freezing method at the same temperature. It became possible to do. The frozen food had better freshness after thawing than that obtained by the air freezing method at the same temperature.

〔The invention's effect〕

In the present invention, the freezing point of the mixed brine obtained by adding 9 wt% or less of calcium chloride to 45-60 wt% ethyl alcohol aqueous solution is in the range of about -60 to -40 ° C.
As shown in the figure, a linear freezing point depression curve is obtained. In the conventional mixed brine containing a trace amount of sodium chloride added to ethyl alcohol, sodium chloride is deposited depending on the concentration, or the freezing point is higher than the freezing point of ethyl alcohol itself at that concentration, but in the mixed brine of the present invention, Calcium chloride has a very high solubility and does not precipitate, nor does the freezing point rise above the freezing point of an ethanol solution of the same concentration. Further, in a conventionally known mixed brine of ethyl alcohol aqueous solution and propylene glycol, the viscosity rapidly increases as the concentration of ethyl alcohol decreases, the amount of propylene glycol added increases, and the temperature lowers, and a brine cooler (heat exchanger) is used. (3) Not only the performance of (1) is significantly impaired, but an increase in power is required to flow the mixed solution having a high viscosity, but this is not necessary because the brine does not have a high viscosity. The brine of the present invention has a specific gravity of 0.
It is about 9, and the frozen product does not float up. That is, according to the present invention, as described above, it can be used at an ultralow temperature, its freezing point characteristics are more stable than a mixed brine of sodium chloride, and the concentration control is extremely easy, and it is peculiar to a concentrated calcium chloride aqueous solution. A safe immersion-freezing mixed brine with no astringency was obtained.

[Brief description of drawings]

FIG. 1 shows the freezing point of a mixed solution obtained by adding calcium chloride to an ethyl alcohol aqueous solution, and FIG. 2 shows an outline of an ultralow temperature immersion freezing apparatus for carrying out the present invention. In FIG. 2, 1 is a brine tank, 2 is a conveyor, 3 is an ultra low temperature mixed brine, 4 is a frozen product, 5 is a brine circulation pump, 6 is a brine cooler, 7 is a brine suction pipe, 8 is a brine discharge pipe, 9 Indicates a brine supply pipe, and 10 indicates a refrigerant inlet / outlet pipe.

Claims (1)

[Claims] 1. A mixed brine for ultra-low temperature immersion freezing, wherein the freezing point is about -60 to -40 ° C. by adding 9% by weight or less of calcium chloride to a 45 to 60% by weight ethyl alcohol aqueous solution.