Gas hydrate-containing ice or frozen desserts containing the gas hydrate-containing ice

Abstract

To provide novel gas hydrate-containing ice in which the stability of the hydrate is improved. [Solution] Gas hydrate-containing ice that satisfies the following conditions. <Condition> a) In differential scanning calorimetry (DSC), it exhibits an endothermic peak with an extrapolated onset temperature of -5°C or higher. b) (Estimated average amount of solvent in the solution before gas hydrate formation) / (Estimated amount of solvent in the gas hydrate-containing ice after gas hydrate formation) > 1.2

Description

[Technical Field]

[0001] The present invention relates to gas hydrate-containing ice or a frozen dessert containing the gas hydrate-containing ice. [Background technology]

[0002] In recent years, development of gas hydrate-containing ice has been progressing as a new food ingredient. Gas hydrate generally refers to solid ice crystals formed by ice and gases such as methane, ethane, and carbon dioxide.

[0003] When gas hydrate is decomposed below the freezing point, the water produced by the decomposition undergoes a phase transition to ice on the surface of the gas hydrate, suppressing the decomposition of the gas hydrate, a phenomenon known as the self-preservation effect (Non-Patent Document 1).While gas hydrate maintains its storage stability due to the self-preservation effect, it is known that gas hydrates with a high content of impurities have a reduced storage stability.

[0004] Gas hydrate-containing ice made from a solution is produced, for example, by the method described in Patent Document 1. The method described in Patent Document 1 is a so-called batch method, in which hydrate is produced in a slurry production vessel, and the sherbet-like slurry containing the produced hydrate is cooled to produce gas hydrate-containing ice. Also, as disclosed in Patent Document 2, a method is known in which gas hydrate-containing ice is produced from raw water using a circulation-type production device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-148370 [Patent Document 2] Japanese Patent Publication No. 2020-081964 [Non-patent literature]

[0006] [Non-Patent Document 1] E. Dendy Sloan Jr et al., “Clathrate Hydrates of Natural Gases”, 3rd Edition, CRC Press, 2007 Summary of the Invention [Problem to be solved by the invention]

[0007] Here, a decrease in the storage stability of gas hydrate can affect the palatability of the gas hydrate-containing ice. For example, if the gas hydrate is decomposed too much, the carbonated taste will be lost. The present inventors have discovered that certain parameters are involved in the storage stability of gas hydrate in gas hydrate-containing ice.

[0008] Therefore, an object of the present invention is to provide novel gas hydrate-containing ice in which the stability of the hydrate is improved.

[0009] The present invention that solves the above problems includes the following [1] to [5]. [1] Gas hydrate-containing ice that meets the following conditions: <Condition> a) In differential scanning calorimetry (DSC), it exhibits an endothermic peak with an extrapolated onset temperature of -5°C or higher. b) (Estimated average amount of solvent in the solution before gas hydrate formation) / (Estimated amount of solvent in the gas hydrate-containing ice after gas hydrate formation) > 1.2

[0010] [2] Gas hydrate-containing ice according to [1], having a gas content of 3% by weight or more.

[0011] [3] Gas hydrate-containing ice according to [1] or [2], made with a flavored solution.

[0012] [4] Gas hydrate-containing ice according to any one of [1] to [3], containing one or more components selected from the group consisting of flavorings, sweeteners, acidulants, salts, emulsifiers, inorganic substances, and amino acids.

[0013] [5] A frozen dessert comprising the gas hydrate-containing ice according to any one of [1] to [4]. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide novel gas hydrate-containing ice in which the stability of the hydrate is improved. DETAILED DESCRIPTION OF THE INVENTION

[0015] In the present invention, "gas hydrate-containing ice" refers to ice obtained by mixing gas and solution and applying low temperature and high pressure to generate gas hydrate, and freezing a slurry containing unreacted solution that was not used in the generation of gas hydrate. In other words, gas hydrate-containing ice is in a state in which the gas hydrate is surrounded by ice of the solution. Since only the water in the solution is used to generate gas hydrate, the concentration of the unreacted solution that is not used to generate gas hydrate becomes higher than the concentration before the generation of gas hydrate.

[0016] Gas hydrates are solid ice crystals formed by the interaction of gases such as methane, ethane, and carbon dioxide with ice. Gas hydrates can be produced by subjecting gases and water (including those in solution) to low temperature and high pressure conditions. The gas is not particularly limited as long as it can generate a gas hydrate, but is preferably a gas that can be used in food. Examples include carbon dioxide, helium, hydrogen, oxygen, nitrogen, nitrous oxide, and argon. Examples of the gas hydrate that can be generated include carbon dioxide hydrate, helium hydrate, and oxygen hydrate.

[0017] The gas hydrate in the present invention is preferably carbon dioxide hydrate. Carbon dioxide hydrate can be produced, for example, by mixing carbon dioxide with a solution, applying a pressure of 1 to 5 MPa, preferably 1.3 to 3.2 MPa, at a temperature of 0 to 10°C, and cooling the mixture.

[0018] In the present invention, gas hydrate-containing ice can be produced by mixing a raw material solution with a raw material gas, applying low temperature and high pressure to the mixture, and freezing a slurry containing the gas hydrate produced by the mixture and unreacted raw material solution that was not used to produce the gas hydrate. Here, when a flavored aqueous solution is used as the solution in producing gas hydrate-containing ice, flavored gas hydrate-containing ice can be produced.

[0019] The solution in the present invention is not particularly limited as long as it can produce gas hydrate, but is an aqueous solution containing ingredients such as flavorings, sweeteners, acidulants, emulsifiers, stabilizers, salts, amino acids, coloring agents, dietary fiber, thickening polysaccharides, vitamins, minerals, inorganic substances, and / or fruit juice, and is preferably a flavored aqueous solution containing one or more ingredients selected from the group consisting of flavorings, sweeteners, acidulants, salts, emulsifiers, inorganic substances, and amino acids.

[0020] In the present invention, inorganic substances preferably refer to inorganic elements such as magnesium, iron, copper, zinc, manganese, etc., which are contained in trace amounts in the raw materials and water, and compounds thereof.

[0021] The frozen dessert of the present invention contains gas hydrate-containing ice that satisfies the following conditions. <Condition> a) In differential scanning calorimetry (DSC), it exhibits an endothermic peak with an extrapolated onset temperature of -5°C or higher. b) (Estimated average amount of solvent in the solution before gas hydrate formation) / (Estimated average amount of solvent in the gas hydrate-containing ice after gas hydrate formation) , the estimated mass of solvent not used in gas hydrate formation )>1.2 Gas hydrate-containing ice that meets all of the above conditions has excellent storage stability when stored at -25°C (defrosted twice a day) for one week.

[0022] In the present invention, when the gas hydrate-containing ice is divided into multiple pieces, the proportion of gas hydrate-containing ice that satisfies the above conditions is preferably 50% or more of the total number of pieces of gas hydrate-containing ice, more preferably 60% or more, even more preferably 70% or more, even more preferably 80% or more, and even more preferably 90% or more.

[0023] In this specification, dividing the gas hydrate-containing ice into a plurality of pieces includes dividing the gas hydrate-containing ice into a plurality of ice blocks by crushing the gas hydrate-containing ice, and dividing a plurality of pieces of gas hydrate-containing ice into several units. "Dividing a plurality of pieces of gas hydrate-containing ice into several units" means dividing separate pieces of gas hydrate-containing ice before crushing into units of one or two or more pieces. In the present invention, the gas hydrate-containing ice is divided into preferably 3 or more, more preferably 4 or more, even more preferably 5 or more, and even more preferably 10 or more pieces.

[0024] In the present invention, the "estimated average amount (kg) of solvent contained in the solution before gas hydrate formation" means the average mass of the solvent contained in the solution for producing gas hydrate-containing ice measured multiple times.

[0025] In the present invention, "gas hydrate-containing ice after gas hydrate formation" , the estimated mass of solvent not used in gas hydrate formation "(kg)" means the mass of the solvent in the solution for making gas hydrate-containing ice minus the amount of water used to form the gas hydrate.

[0026] The extrapolated onset temperature is preferably −4.5° C. or higher, more preferably −4° C. or higher, even more preferably −3.5° C. or higher, even more preferably −3° C. or higher, and most preferably −2.5° C. or higher, with the upper limit being 0° C.

[0027] The extrapolated onset temperature of the endothermic peak in differential scanning calorimetry (DSC) of the gas hydrate-containing ice in the present invention can be measured by a conventional method.

[0028] The extrapolation onset temperature can be adjusted depending on the type and mass of solute contained in the gas hydrate-containing ice.

[0029] For example, since organic solvents contained in alcohols and perfumes have very low melting points, the extrapolated onset temperature tends to be low when a large amount of such organic solvent is contained as a solute.

[0030] Furthermore, since the number of particles of electrolytes such as sodium chloride increases upon dissolution, the extrapolation onset temperature tends to be lower when a large amount of electrolytes such as salts is contained as solutes.

[0031] Furthermore, since substances with low molecular weights have a greater number of particles per mass than substances with high molecular weights, the extrapolated onset temperature tends to be lower when a large amount of substances with low molecular weights is included.

[0032] The estimated average amount of solvent contained in the solution before gas hydrate formation / the amount contained in the gas hydrate-containing ice after gas hydrate formation , the estimated mass of solvent not used in gas hydrate formation is preferably greater than 1.22, more preferably greater than 1.25, and even more preferably greater than 1.28.

[0033] The method for measuring the estimated amount of solvent contained in the solution before gas hydrate formation in the present invention is not particularly limited, but examples include a method of measuring the amount of solvent contained in a solution for preparing gas hydrate-containing ice in advance, a method of measuring the amount of solvent contained in a solution obtained by melting gas hydrate-containing ice after gas hydrate formation, and a method of calculating the amount of solvent in ice with a hydrate rate of 0% prepared with the same amount of solvent as the gas hydrate-containing ice using the following formula (1).

[0034] ΔT f =K f m (1) ΔT f :Freezing point depression degree K f : Molar freezing point depression (K kg / mol) m: molar mass concentration (mol / kg)

[0035] In the present invention, ΔT f (Freezing point depression) can be the absolute value of the extrapolated onset temperature in differential scanning calorimetry (DSC). In the present invention, when an aqueous solution is used as the solution, K f The molar freezing point depression is 1.85 (K·kg / mol).

[0036] In the present invention, the amount of solvent obtained by formula (1) can be taken as the estimated amount of solvent contained in the solution before gas hydrate formation.

[0037] The gas hydrate-containing ice after gas hydrate formation according to the present invention , the estimated mass of solvent not used in gas hydrate formation The method for measuring is not particularly limited, but examples include a method of calculating from the amount of solvent contained in a solution obtained by melting the gas hydrate-containing ice after gas hydrate formation and the hydrate ratio of the gas hydrate-containing ice, a method of determining from the above formula (1), and a method of calculating by X-ray analysis.

[0038] The solvent amount measured by either of the above methods was used to calculate the "estimated average solvent amount contained in the solution before gas hydrate formation / the amount contained in the gas hydrate-containing ice after gas hydrate formation." , the estimated mass of solvent not used in gas hydrate formation When " is greater than 1.2, gas hydrate-containing ice satisfies <condition>b).

[0039] The gas hydrate-containing ice of the present invention exhibits excellent storage stability of the gas hydrate when stored at −25° C. (defrosted twice a day) for one week.

[0040] In the present invention, defrosting is performed for 30 minutes every 12 hours. Specifically, defrosting is performed based on a program that raises the surface temperature inside the freezer to 5°C and then lowers the temperature again to -25°C.

[0041] In the present invention, the storage stability of a gas hydrate when stored at −25° C. (defrosted twice a day) for one week can be evaluated by the residual rate calculated by the following formula (2), where S0 is the average hydrate rate at the time of making or obtaining the gas hydrate-containing ice, and S1 is the average hydrate rate after storage at −25° C. (defrosted twice a day) for one week. Survival rate (%) = 100×S1 / S0 (2)

[0042] The hydrate ratio of gas hydrate-containing ice means the ratio of the weight of gas hydrate when the weight of the gas hydrate-containing ice block is taken as 1. There are no particular restrictions on the method for calculating the hydrate ratio of gas hydrate-containing ice, but it can be calculated, for example, by the following formula (3). It can also be calculated by X-ray analysis.

[0043] Hydrate rate (%) = {(sample weight before melting - sample weight after melting) ÷ 44 × (44 + 6.2 × 18)} ÷ sample weight before melting × 100 (3)

[0044] (Sample weight before melting - sample weight after melting) is the weight of carbon dioxide encapsulated in the gas hydrate-containing ice. The amount of water required to encapsulate carbon dioxide as a hydrate is calculated using a theoretical hydration number of 6.2, a molecular weight of carbon dioxide of 44, and a molecular weight of water of 18 (Reference: Udachin, KA et al., (2001) "Structure, Composition, and Thermal Expansion of CO2 Hydrate from Single Crystal X-ray Diffraction Measurements", The Journal of Physical Chemistry B, 105(19), pp. 4200-4204.).

[0045] The gas hydrate-containing ice of the present invention preferably has a gas content of 3% by weight or more. The gas content can be adjusted by adjusting the pressure conditions when producing the gas hydrate-containing ice of the present invention. For example, increasing the pressure can increase the gas content of the gas hydrate-containing ice. Furthermore, lowering the temperature increases the reaction rate, thereby increasing the gas content of the gas hydrate-containing ice. Furthermore, under the same pressure and temperature conditions, extending the reaction time can increase the gas content of the gas hydrate-containing ice. Furthermore, the gas content of the gas hydrate-containing ice can be increased by dehydrating a slurry containing gas hydrate and unreacted solution not used in producing the gas hydrate before freezing it.

[0046] The gas content of gas hydrate-containing ice can be calculated, for example, from the change in weight when the gas hydrate-containing ice is melted at room temperature using the following formula (4). Gas content (%) = (sample weight before melting - sample weight after melting) / sample weight before melting × 100 (4) When the gas content of the gas hydrate-containing ice is within the above range, the frozen dessert of the present invention has an excellent foaming sensation when eaten.

[0047] The frozen dessert of the present invention may be in the form of gas hydrate-containing ice eaten as is, or may be in the form of a frozen dessert containing gas hydrate-containing ice in, for example, whipped cream, custard cream, chocolate cream, ice cream, or the like eaten at freezing temperatures.

[0048] In the gas hydrate-containing ice of the present invention, when the gas hydrate-containing ice is divided into a plurality of pieces, the coefficient of variation of the Brix values ​​of the plurality of pieces of gas hydrate-containing ice is 0.4 or less. The coefficient of variation of the Brix values ​​is preferably 0.35 or less, more preferably 0.3 or less, even more preferably 0.25 or less, still more preferably 0.2 or less, and most preferably 0.15 or less.

[0049] The coefficient of variation is given by the following equation (5): Coefficient of variation = standard deviation / mean (5)

[0050] The Brix value of the gas hydrate-containing ice can be calculated from a solution obtained by melting the gas hydrate-containing ice. An example of a method for calculating the Brix value of gas hydrate-containing ice is to calculate the Brix value at 20° C. using a refractometer (manufactured by ATAGO, model: RX-5000i).

[0051] In a preferred embodiment of the present invention, the coefficient of variation of Brix values ​​of each of the plurality of gas hydrate-containing ice blocks is 0.4 or less.

[0052] The method for producing gas hydrate-containing ice of the present invention will now be described in detail.

[0053] First, a raw material solution and a raw material gas for producing a gas hydrate are mixed together, and the raw material gas is mixed into the raw material solution (S11; gas-liquid mixing step).

[0054] Next, gas hydrate is produced from the raw material solution and the raw material gas (S12: gas hydrate production step).

[0055] Finally, the gas hydrate slurry containing the gas hydrate and a portion of the raw material solution is frozen to produce gas hydrate-containing ice (S13; freezing step).

[0056] Between the gas hydrate production step and the freezing step, the gas hydrate slurry may be subjected to a dehydration treatment (dehydration step).

[0057] The gas hydrate-containing ice of the present invention may be produced using either a batch-type or a circulation-type gas hydrate-containing ice production apparatus, but the use of a circulation-type gas hydrate-containing ice production apparatus is preferred from the viewpoint of reducing the uneven distribution of gas hydrate contained in the gas hydrate-containing ice and reducing the variation in taste.

[0058] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. [Example]

[0059] [Storage stability of ice containing gas hydrates that meet specific conditions] <Test Example> Creation of ice containing gas hydrate First, flavored solutions were prepared according to the formulations shown in Table 1 below. The amount of solute (mol) in each formulation is determined taking into account the ionization of electrolytes.

[0060] [Table 1]

[0061] Gas hydrate-containing ice was prepared using flavored solutions of formulations 1 to 5. Specifically, the flavored solutions of Blends 1 to 5 were each placed in a batch-type gas hydrate-containing ice manufacturing device, and carbon dioxide gas was supplied at a pressure of 2 to 3 MPa to achieve the hydrate percentages shown in Table 1. The mixture was then cooled to the gas hydrate formation temperature while stirring. Gas hydrate was formed in this process. The mixture was then frozen in an environment of -20°C to obtain gas hydrate-containing ice. The gas hydrate-containing ice was then crushed to obtain samples of Examples 1 to 9 and Comparative Examples 1 to 5. The hydrate percentages listed in Table 2 are design values, and the actual hydrate percentages differ for each sample, just as the "solvent amount (after)" differs between the samples of Examples 1 to 9 and Comparative Examples 1 to 5. The gas content of each sample was 3 wt % or more.

[0062] For each sample, the extrapolated onset temperature of the endothermic peak in differential scanning calorimetry (DSC) was measured. Then, from the above formula (1), the estimated average amount of solvent contained in the solution before gas hydrate formation and the estimated amount of solvent contained in the gas hydrate-containing ice after gas hydrate formation were calculated, and the ratio was calculated as follows: (estimated average amount of solvent contained in the solution before gas hydrate formation) / (estimated average amount of solvent contained in the gas hydrate-containing ice after gas hydrate formation) , the estimated mass of solvent not used in gas hydrate formation The ratio of the gas hydrate content (%) to the total content (%) was calculated ("solvent volume ratio" in Table 2). In addition, the gas hydrate remaining rate ("remaining rate" in Table 2) of each sample was measured after storage at -25°C (defrosting twice a day) for one week, and evaluated according to the following evaluation criteria.

[0063] (Evaluation criteria) [Storage stability] ○: Gas hydrate remaining rate is 50% or more △: Gas hydrate remaining rate is 40% or more but less than 50% ×: Gas hydrate remaining rate is less than 40%

[0064] Next, each sample was evaluated for carbonation by three experienced evaluators. When the gas hydrate-containing ice to be evaluated had a strong carbonated taste, it was rated as ⊚. When the gas hydrate-containing ice to be evaluated had a slightly strong carbonated taste, it was rated as ◯. When the carbonation sensation felt from the gas hydrate-containing ice to be evaluated was weak, the evaluation was rated as △. When the gas hydrate-containing ice to be evaluated had no sense of carbonation at all, it was rated as x.

[0065] (Evaluation criteria) [Sensory evaluation] Gas hydrate-containing ice that was rated as ⊚ by two or more evaluators was given an overall rating of ⊚ for carbonation. Gas hydrate-containing ice that was rated as ○ by two or more evaluators was given an overall rating of ○ for carbonation. For gas hydrate-containing ice that was rated △ by two or more evaluators, the overall carbonation rating was △. Gas hydrate-containing ice that was rated x by two or more evaluators was given an overall rating of x for carbonation.

[0066] [Table 2]

[0067] From Example 1 and Comparative Examples 1 and 2, it was found that gas hydrate-containing ice satisfying both conditions a and b had a gas hydrate residual rate of over 50% when stored at -25°C (defrosted twice a day) for one week, demonstrating excellent storage stability of the gas hydrate. It was also found that the overall carbonation rating was good or better.

[0068] Furthermore, Example 1 and Comparative Examples 3 to 5 show that gas hydrate-containing ice satisfying both conditions a and b has a gas hydrate residual rate of over 50% when stored at -25°C (defrosted twice a day) for one week, demonstrating excellent storage stability of the gas hydrate. It was also found that the overall carbonation rating was good or better. [Industrial Applicability]

[0069] According to the present invention, it is possible to provide gas hydrate-containing ice in which the stability of the hydrate is improved, or a frozen dessert containing the gas hydrate-containing ice.

Claims

1. The flavored aqueous solution is prepared using a flavored aqueous solution containing one or more ingredients selected from the group consisting of flavorings, sweeteners, acidulants, salts, emulsifiers, inorganic substances, and amino acids. Flavored gas hydrate-containing ice that meets the following conditions: <Conditions> a) In differential scanning calorimetry (DSC), it exhibits an endothermic peak with an extrapolated onset temperature of -5°C or higher. b) (Estimated average amount of solvent contained in the solution before gas hydrate formation) / (Estimated mass of solvent contained in the gas hydrate-containing ice after gas hydrate formation that was not used to produce the gas hydrate) > 1.25

2. 2. The flavored gas hydrate-containing ice according to claim 1, wherein the gas hydrate is carbon dioxide hydrate.

3. 3. The flavored gas hydrate-containing ice according to claim 1 or 2, wherein the gas content is 3% by weight or more.

4. A frozen dessert comprising ice containing the flavored gas hydrate according to claim 1 or 2.

5. Flavored gas hydrate-containing ice, wherein when the flavored gas hydrate-containing ice is divided into a plurality of pieces, the proportion of flavored gas hydrate-containing ice that satisfies the following conditions is 80% or more of the entire plurality of flavored gas hydrate-containing ice pieces. <Conditions> a) In differential scanning calorimetry (DSC), it exhibits an endothermic peak with an extrapolated onset temperature of -5°C or higher. b) (Estimated average amount of solvent contained in the solution before gas hydrate formation) / (Estimated mass of solvent contained in the gas hydrate-containing ice after gas hydrate formation that was not used to produce the gas hydrate) > 1.25

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