Ice containing gas hydrate or frozen desserts containing such ice.

Abstract

To provide a novel gas hydrate-containing ice with improved hydrate stability. [Solution] Ice containing gas hydrate that satisfies the following conditions. <Condition> a) In differential scanning calorimetry (DSC), exhibiting an endothermic peak with an extrapolation start 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 ice containing gas hydrate or a frozen confection containing the ice containing gas hydrate.

Background Art

[0002] In recent years, the development of ice containing gas hydrate as a new food material has been promoted. Gas hydrate generally refers to an ice-like solid crystal formed by a gas such as methane, ethane, and carbon dioxide and ice.

[0003] When gas hydrate is decomposed below the freezing point, a phenomenon called self-preservation effect is observed, in which the water generated by the decomposition undergoes a phase transition to ice on the surface of the gas hydrate, suppressing the decomposition of the gas hydrate (Non-Patent Document 1). While gas hydrate maintains storage stability due to the self-preservation effect, it has been found that the storage stability of gas hydrate with many impurities decreases.

[0004] Ice containing gas hydrate prepared from a solution is produced, for example, by the method described in Patent Document 1. The method described in Patent Document 1 is a method called a so-called batch method, in which hydrate is generated in a slurry preparation container, and the sherbet-like slurry containing the generated hydrate is cooled to produce ice containing gas hydrate. Also, as in Patent Document 2, a method of generating ice containing gas hydrate from raw water using a circulation type production apparatus is known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0006] [Non-Patent Document 1] E. Dendy Sloan Jr et al., “Clathrate Hydrates of Natural Gases”, 3rd Edition, CRC Press, 2007 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In this context, a decrease in the storage stability of gas hydrates can affect the palatability of ice containing gas hydrates. For example, if the gas hydrates decompose too much, the carbonation is lost. The inventors have discovered that specific parameters are involved in the storage stability of gas hydrates in gas hydrate-containing ice.

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

[0009] The present invention, which solves the above problems, is as follows [1] to [5]. [1] Gas hydrate-containing ice that meets the following conditions: <Condition> a) In differential scanning calorimetry (DSC), exhibiting an endothermic peak with an extrapolation start 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 as described in [1], wherein the gas content is 3% by weight or more.

[0011] [3] Gas hydrate-containing ice as described in [1] or [2], made with a flavored solution.

[0012] [4] Gas hydrate-containing ice according to any 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 containing gas hydrate ice as described in any of [1] to [4]. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a novel gas hydrate-containing ice with improved hydrate stability. [Modes for carrying out the invention]

[0015] In this invention, "gas hydrate-containing ice" refers to ice obtained by freezing a slurry containing gas hydrate, which is produced by mixing gas and a solution and applying low temperature and high pressure, as well as unreacted solution that was not used to produce the gas hydrate. In other words, gas hydrate-containing ice is a state in which the gas hydrate is surrounded by ice made from the solution. Since only water in the solution is used to form gas hydrates, the concentration of unreacted solution that was not used to form gas hydrates becomes higher than the concentration before gas hydrate formation.

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

[0017] The gas hydrate in the present invention is preferably a carbon dioxide hydrate. The 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.

[0018] In the present invention, the ice containing gas hydrate can be produced by freezing a slurry containing the gas hydrate produced by mixing a raw material solution and a raw material gas under low temperature and high pressure, and the unreacted raw material solution not used for the production of the gas hydrate. [[ID=�]]Here, when a seasoned aqueous solution is used as the solution in the production of the ice containing gas hydrate, the seasoned ice containing gas hydrate can be produced.

[0019] The solution in the present invention is not particularly limited as long as it can produce a gas hydrate, but is an aqueous solution containing components such as flavors, sweeteners, acidulants, emulsifiers, stabilizers, salts, amino acids, colorants, dietary fibers, thickening polysaccharides, vitamins, minerals, inorganic substances, and / or fruit juices, etc., and preferably, it is a seasoned aqueous solution containing one or more components selected from the group consisting of flavors, sweeteners, acidulants, salts, emulsifiers, inorganic substances, and amino acids.

[0020] The inorganic substances in the present invention preferably refer to inorganic elements and their compounds contained in trace amounts in each raw material and water, such as magnesium, iron, copper, zinc, manganese, etc.

[0021] The frozen confection of the present invention contains ice containing gas hydrate that satisfies the following conditions. <Condition> a) In differential scanning calorimetry (DSC), it shows an endothermic peak with an extrapolated onset temperature of -5 °C or higher b) (Estimated average solvent amount contained in the solution before gas hydrate formation) / (Estimated solvent amount contained in the ice containing gas hydrate after gas hydrate formation) > 1.⒉ The ice containing gas hydrate that satisfies all of the above conditions has excellent storage stability when stored at -25 °C (defrosting twice a day) for one week.

[0022] In the present invention, when the gas hydrate-containing ice is divided into multiple portions, it is preferable that the proportion of gas hydrate-containing ice that satisfies the above conditions is 50% or more of the total gas hydrate-containing ice of the multiple portions, 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 multiple parts includes dividing the gas hydrate-containing ice into multiple ice blocks by crushing it, and dividing multiple gas hydrate-containing ice into units of several pieces. "Dividing multiple gas hydrate-containing ice into units of several pieces" means dividing separate gas hydrate-containing ice before crushing into units of one or more pieces. In the present invention, the gas hydrate-containing ice is preferably divided into 3 or more, more preferably 4 or more, even more preferably 5 or more, and even more preferably 10 or more.

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

[0025] Furthermore, in this invention, "estimated amount of solvent (kg) contained in gas hydrate-containing ice after gas hydrate formation" means the mass of solvent obtained by subtracting the amount of water used to form the gas hydrate from the solution used to produce the gas hydrate-containing ice.

[0026] The extrapolation start 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. The upper limit is 0°C.

[0027] In the present invention, the extrapolation start temperature at the endothermic peak of differential scanning calorimetry (DSC) of gas hydrate-containing ice can be measured by a conventional method.

[0028] The extrapolation start 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 fragrances have very low melting points, the extrapolation start temperature tends to be lower when a large amount of the aforementioned organic solvent is included as the solute.

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

[0031] Furthermore, because substances with smaller molecular weights have a higher number of particles per unit mass than substances with larger molecular weights, the extrapolation start temperature tends to be lower when a mixture contains a large amount of substances with smaller molecular weights.

[0032] The estimated average amount of solvent contained in the solution before gas hydrate formation / estimated amount of solvent contained in the gas hydrate-containing ice after 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 a solution before gas hydrate formation according to the present invention is not particularly limited, but examples include a method for measuring the amount of solvent contained in a solution for producing gas hydrate-containing ice in advance, a method for measuring the amount of solvent contained in a solution obtained by melting gas hydrate-containing ice after gas hydrate formation, and a method for determining the amount of solvent in ice with a hydrate content of 0% produced with the same amount of solvent as gas hydrate-containing ice from 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: Molality (mol / kg)

[0035] In the present invention, ΔT f The freezing point depression can be defined as the absolute value of the extrapolation start 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 assumed to be 1.85 (K·kg / mol).

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

[0037] The method for measuring the estimated amount of solvent contained in the gas hydrate-containing ice after gas hydrate formation according to the present invention is not particularly limited, but examples include a method of calculating from the amount of solvent contained in the 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] When the "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," calculated using the amount of solvent measured by one of the above methods, is greater than 1.2, the gas hydrate-containing ice satisfies condition b).

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

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

[0041] In the present invention, the storage stability of gas hydrate after being stored at -25°C (defrosted twice a day) for one week can be evaluated by the remaining percentage calculated using the following formula (2), where S0 is the average hydrate percentage at the time of creating or obtaining the gas hydrate-containing ice, and S1 is the average hydrate percentage after being stored 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 refers to the ratio of the weight of gas hydrate to the weight of the ice mass, where gas hydrate-containing ice mass is considered to be 1. While there are no particular limitations on the method for calculating the hydrate ratio of gas hydrate-containing ice, it can be calculated, for example, using the following formula (3). It can also be calculated using X-ray analysis.

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

[0044] The ratio (sample weight before melting - sample weight after melting) represents the weight of carbon dioxide encapsulated in the gas hydrate-containing ice. The amount of water required to encapsulate the carbon dioxide as hydrate is calculated using the theoretical hydration number of 6.2, the molecular weight of carbon dioxide of 44, and the 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] In the present invention, the gas hydrate-containing ice preferably has a gas content of 3% by weight or more. The gas content can be adjusted by the pressure conditions when producing the gas hydrate-containing ice in the present invention. For example, increasing the pressure can increase the gas content of the gas hydrate-containing ice. Also, lowering the temperature increases the reaction rate and can increase the gas content of the gas hydrate-containing ice. Furthermore, if the pressure and temperature are the same, increasing the reaction time can increase the gas content of the gas hydrate-containing ice. In addition, the gas content of the gas hydrate-containing ice can be increased by dehydrating the slurry containing the gas hydrate and the unreacted solution not used in the production of the gas hydrate before freezing.

[0046] The gas content of gas hydrate-containing ice can be calculated, for example, from the weight change 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 exhibits excellent effervescence when consumed.

[0047] The frozen dessert of the present invention may be in a form in which gas hydrate-containing ice is consumed as a frozen dessert, or it may be in a form in which gas hydrate-containing ice is included in whipped cream, custard cream, fresh chocolate cream, ice cream, etc., which are consumed at freezing temperatures, and then consumed as a frozen dessert.

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

[0049] The coefficient of variation is obtained by the following equation (5). Coefficient of variation = Standard deviation / Mean ... (5)

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

[0051] In a preferred embodiment of the present invention, the coefficient of variation of the Brix value of each ice block containing a plurality of gas hydrates is 0.4 or less.

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

[0053] First, the raw material solution and raw material gas for generating the gas hydrate are mixed, 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] The gas hydrate slurry may be dehydrated between the gas hydrate generation process and the freezing process (dehydration process).

[0057] In producing gas hydrate-containing ice according to the present invention, either a batch-type or circulating-type gas hydrate-containing ice production apparatus may be used. However, using a circulating-type gas hydrate-containing ice production apparatus is preferable from the viewpoint of reducing the uneven distribution of gas hydrate contained in the gas hydrate-containing ice and reducing variations 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. [Examples]

[0059] [Storage stability of gas hydrate-containing ice that meets specific conditions] <Example Test> Creation of Gas Hydrate-Containing Ice First, flavored solutions were prepared according to the formulations shown in Table 1 below. Here, the solubility (mol) of each formulation is the solubility considering the ionization of the electrolyte.

[0060] [Table 1]

[0061] Gas hydrate-containing ice was prepared using flavored solutions with formulations 1 to 5. Specifically, flavored solutions 1 to 5 were each introduced into a batch-type gas hydrate-containing ice production apparatus. Carbon dioxide gas was supplied at a pressure of 2 to 3 MPa to achieve the hydrate ratios shown in Table 1, and the mixture was cooled to the gas hydrate generation temperature while stirring. Gas hydrate was generated in this process. Subsequently, the mixture was frozen at -20°C to obtain gas hydrate-containing ice. The gas hydrate-containing ice was then crushed to obtain samples for Examples 1-9 and Comparative Examples 1-5. Here, the hydrate percentages listed in Table 2 are design values, and the actual hydrate percentage differs for each sample, as evidenced by the different "solvent amount (after)" values ​​for Examples 1-9 and Comparative Examples 1-5. Furthermore, the gas content of each sample was 3% by weight or more.

[0062] For each sample, the extrapolation start temperature at the endothermic peak was measured using differential scanning calorimetry (DSC). Then, using equation (1) above, 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 of (estimated average amount of solvent contained in the solution before gas hydrate formation) / (estimated amount of solvent contained in the gas hydrate-containing ice after gas hydrate formation) was determined (see "solvent ratio" in Table 2). In addition, the gas hydrate retention rate (see "retention rate" in Table 2) was measured for each sample after storage at -25°C (defrosted twice a day) for one week, and evaluated according to the following evaluation criteria.

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

[0064] Next, the carbonation level of each sample was evaluated. The evaluation was conducted by three experienced evaluators. If the carbonation sensation felt strongly from the gas hydrate-containing ice being evaluated, it was given a rating of ◎. If the carbonation sensation felt slightly strong in the gas hydrate-containing ice being evaluated, it was given a rating of ○. If the carbonation sensation felt weak for the gas hydrate-containing ice being evaluated, it was given a rating of △. If no carbonation sensation was felt at all with the gas hydrate-containing ice being evaluated, it was given a rating of ×.

[0065] (Evaluation Criteria) [Sensory evaluation] Ice containing gas hydrate that received a rating of ◎ from two or more evaluators received an overall rating of ◎ for its carbonation level. Ice containing gas hydrate that received a "○" rating from two or more evaluators was given an overall "○" rating for its carbonation level. Ice containing gas hydrate that received a △ rating from two or more evaluators received an overall △ rating for its carbonation level. Ice containing gas hydrate that received a "×" rating from two or more evaluators received an overall "×" rating for its carbonation level.

[0066] [Table 2]

[0067] From Example 1 and Comparative Examples 1 and 2, it was found that ice containing gas hydrate that satisfies both conditions a and b had a gas hydrate retention rate of over 50% after being stored at -25°C (defrosted twice a day) for one week, indicating excellent storage stability of the gas hydrate. Furthermore, it was found that the overall carbonation level was rated as ○ or higher.

[0068] Furthermore, from Example 1 and Comparative Examples 3-5, it was found that gas hydrate-containing ice satisfying both conditions a and b had a gas hydrate retention rate exceeding 50% after being stored at -25°C (defrosted twice a day) for one week, indicating excellent storage stability of the gas hydrate. It was also found that the overall carbonation level was rated as ○ or higher. [Industrial applicability]

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

Claims

1. Ice containing gas hydrate that meets the following conditions. <Conditions> a) In differential scanning calorimetry (DSC), an endothermic peak is observed with an extrapolation start 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

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

3. Ice containing gas hydrate as described in claim 1 or 2, prepared with a flavored solution.

4. The gas hydrate-containing ice according to claim 1 or 2, which contains one or more components selected from the group consisting of flavorings, sweeteners, acidulants, salts, emulsifiers, inorganic substances, and amino acids.

5. A frozen dessert comprising gas hydrate-containing ice according to claim 1 or 2.

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