MXPA99005429A - Manufacture of frozen products comestib - Google Patents

Abstract

The present invention relates to a simple and inexpensive method for producing a gas hydrate comprising the steps of: (i) filling a vessel with an amount of liquid water and / or frozen water, (ii) adding the vessel an amount of hydrate-forming condensed gas in such a way that the condensed gas does not come into contact with liquid water, (iii) contact the condensed gas, and / or its products of sublimation or liquefaction, at a suitable pressure, with the water mixture liquid and / or frozen to produce a reaction mixture, and keep the reaction mixture at or below the maximum temperature at which the gas hydrate is stable, and at a suitable pressure for a sufficient time to produce the gas hydrate. The gas hydrate produced by the method, which has a high gas content, is also provided. There is also provided a reaction vessel comprising means for separating the condensed hydra forming gas from the liquid / frozen water.

Description

MANUFACTURE OF COMBUSTIBLE FROZEN PRODUCTS The invention relates to the manufacture of frozen products and, more precisely, to the manufacture of edible solid gas hydrates for use in food products. Various methods for manufacturing gas hydrates are known, for example US-A-4 347 707, US-A-4 487 023 and US-A-3 217 503. Ws 94/02414 (EP 651 727) describes a method for the manufacture of solid gas hydrates in which an aqueous liquid as a continuous phase, which has dissolved the. Hydrate-forming gas is cooled to a low enough temperature to form the solid gas hydrate. All the methods described above require careful control of the reaction conditions or, more importantly, complicated or expensive equipment or conditions. In the methods of U.S. Pat. As mentioned above, the composition of the final product can not be readily predetermined, in particular as regards higher gas contents. Conventionally, a liquefied or gaseous hydrate forming gas, for example C02, is used in the preparation of gas hydrates, and it is therefore necessary to address safety problems and well-known technical problems. The present invention addresses these problems by providing a method for the manufacture of solid gas hydrates, which requires only a simple pressure vessel and the use of commonly existing freezing facilities. Solid gas hydrates are of particular use in frozen food products. Accordingly, the invention provides a method for producing a gas hydrate comprising the steps of: (i) filling a vessel with an amount of liquid water and / or frozen water, (ii) adding to the vessel a quantity of condensed gas hydrate former such that the condensed gas does not come into contact with liquid water, (iii) contacting the condensed gas, and / or its products of sublimation or liquefaction, - at a suitable pressure, - with the water mixture liquid and / or frozen to produce a reaction mixture, and keep the reaction mixture at or below the maximum temperature at which the gas hydrate is stable, and at a suitable pressure for a sufficient time to produce the gas hydrate. Also provided by the present invention is a gas hydrate produced by the method of the invention. The method of the present invention provides several advantages not previously associated with the manufacture of solid gas hydrates. These advantages include low cost, flexibility to manufacture large or small scale and / or total or partial automation or manual operation (even by one person). In addition, the products have high activity, that is, large volumes of gas per unit of weight. Therefore, the present invention provides an effective and yet surprisingly simple method for producing gas hydrates by the use of condensed hydrate forming gases, for example solid C02. This makes the procedure much easier to control and perform. The above advantages have not been provided so far due to the difficulties involved in handling conventionally used gaseous gases.

Ingredients and product The gas hydrate produced can be any that can be prepared by the method, in particular C02 gas hydrate. It is especially preferred that the gas hydrate comprises CO gas hydrate? . The hydrate-forming condensed gas used corresponds to the gas hydrate to be produced. Preferably, the hydrate-forming condensed gas comprises C02. Water is used in the method of the present invention. Preferably, purified or pure water is used. The water can be added to the vessel as liquid water and / or as frozen water. Preferably, a mixture of liquid and frozen water is added to the vessel, but it is possible to add only frozen water to the vessel and allow it to melt completely or partially. As an alternative, only liquid water can be added and the water can be totally or partially frozen. When "gas hydrate" is mentioned herein, this includes within this term gas / ice hydrate composites. The hydrate-forming condensate gas is used in the present method in the form in which it exists at atmospheric pressure. For example, condensed carbon dioxide exists in solid form at atmospheric pressure and is thus used in this form. The references to condensed gas forming hydrate in this specification are to be interpreted accordingly. Typically, the hydrate-forming condensed gas will be in the solid state. The method of the invention will now be described in more detail with reference to steps (i) to (iii). It will be understood that within the present invention one or more of the following steps may occur concurrently or that the order of steps (i) and (ii) may possibly be reversed.

Step (i) In the first step of the method, the vessel is filled with a quantity of liquid water and / or frozen water. Any suitable method can be used, for example dose-measurement, pouring, filling by weighing, etc. In a preferred embodiment the vessel is filled with a mixture of liquid water and frozen water so that the latter floats on the surface of the former. Preferably, before the hydrate-forming condensed gas is added to the vessel, the vessel contains a mixture of 10-80% by weight of water frozen in liquid water,. based on the total amount of water, preferably 20-40%, for example 25-40%, based on the total amount of water. If a mixture of liquid water and frozen water is used, the proportions of liquid water to frozen water (expressed as the above percentages by weight) can be controlled so as to have the appropriate heat content for the vessel to equilibrate at a temperature to which at least substantially all of the gas hydrate has been formed and at least substantially all of the ice has been consumed. In other words, the reaction in the vessel is largely self-regulating when the ice level is controlled within the limits indicated here. The desired ratio of liquid water is obtained: frozen water using the above percentages by weight of frozen water in liquid water. In one embodiment of the invention, a hydrated, pulverized, finely divided or granular hydrate-forming condensed gas, for example C02 solidified, is added to the vessel containing liquid water and frozen water. Hydrated pulverized hydrate forming gas is preferred. An ice plug is thus formed through the surface of the liquid water by the action of the solidified gas on ice floating in the water, and this plug forms an at least substantially complete barrier through the cross section of the vessel. The ice cap is ideally formed as a solid "plug" of ice that extends across the entire cross section of the vessel. The ice cap could also be formed by other methods. The "ice plug barrier" described above is a method for achieving physical separation of the liquid water and the hydrate-forming condensed gas as required in step (ii). Other suitable methods for achieving separation can be used, and some other suitable methods are described later in step (ii). The term "filling", as used herein, does not necessarily describe the vessel being filled to its full capacity. Usually, the vessel is filled to 65-90% of its volume, for example 75-90% of its volume.

Alternatively, the vessel can be filled only with frozen water in step (i) so that the use of a hydrate-forming condensed gas to form the ice plug is not required. Normally, the amount of liquid and / or frozen water is predetermined before filling the vessel so that the exact amount of each ingredient is added. Alternatively, a first calculated amount of an ingredient may be added, and the amount of the second ingredient may be calculated accordingly.

Step (ii) In the second step, an amount of a hydrate-forming condensed gas is added to the vessel in such a manner that liquid water and the condensed hydrate-forming gas do not come into contact, ie they are physically separated. It should be noted that the order of steps (i) and (ii) can be reversed when only the frozen water is added to the vessel. Therefore, in practice, the hydrate-forming condensed gas can be added before, during or after the step (i) • The physical separation of liquid water and condensed gas (when it is in solid form) can be achieved by any suitable method. Suitable methods include, for example, using a vessel with a stepped internal diameter in conjunction with a block of condensed gas forming hydrate (e.g., Solid C02), or fix a block of hydrate-forming condensed gas (eg, solid C02) to the lid of the vessel, or arrange 'shelves in the vessel above the water level. In a preferred embodiment, the condensed hydrate-forming gas is added to the vessel, preferably in the form of granules, so that it remains on an ice plug (formed in the first step) and thus contact with liquid water is avoided until required . Preferably, the ice cap has liquid water on one side and the condensed gas forming hydrate on the other side, whereby the two ingredients do not come into contact until the ice plug is melted or the ice plug loses its integrity from some other way. In another embodiment separation can be obtained by using a platform comprising a shelf and a support column, wherein the shelf is supported by the support column, which extends from the base of the vessel to above the surface of the water. (be it liquid, frozen or a mixture of both) in the vessel. The shelf is located above the surface of the water when the vessel is upright. The platform comprises a support column that can be detached from the base of the vessel. Preferably, the shelf is concentric with the support column or is positioned so that it rests on the cusp of the column. The outer edge (cross section) of the shelf may be of any suitable shape, although, to provide an effective physical barrier, it is preferred that the shelf have a cross-sectional shape substantially congruent with that of the interior surface of the sides of the vessel . However, there must be a sufficient gap between the edge of the shelf and the interior surface of the vessel to allow the reaction mixture to mix properly. The supporting column can extend above the shelf to the lid of the vessel when the vessel is in vertical position. In a preferred vessel type, the support column is preferably positioned in the center of the vessel cavity and extends from the base of the vessel 'to the lid. The platform can be made of any suitable material, but is preferably of a flexible material that is easily peeled off from the gas hydrate product (e.g., polytetrafluoroethylene (PTFE)). The platform must be removable from the vessel to allow effective removal of the product. According to this embodiment, the support column preferably provides a central annular crown with respect to the reaction vessel. This provides the advantage of a reduced processing time. Before, during or after the hydrate-forming condensed gas is added, in any method of performing the second step, an amount of the pre-formed product of the gas hydrate can be added to induce a nucleation of the gas hydrate product. Preferably, a pre-formed product of finely divided, pulverized or granular gas hydrate is added to the ice plug formed in the first step. The preformed gas hydrate product can be added at any time before the condensed hydrate-forming gas and liquid water are brought into contact. Preferably, the preformed hydrate product is added to the ice cap before it is melted. The hydrate-forming condensed gas and the gas hydrate pre-formed product (if used) are supported by the ice plug or platform shelf, and are kept physically separate from the liquid water. This allows the safe sealing of the vessel, since the two components of the gas hydrate product have not yet been put into intimate contact. The ingredients are usually added at atmospheric pressure. The weight ratio of condensed hydrate-forming water: frozen water and total liquid is preferably in the range of 1: 2, 35 to 1:11, preferably 1: 3 to 1:10, for example 1: 4 to 1: 7, such as 1: 5.5 for the preparation of C02 gas hydrate. This corresponds to molar ratios for C02: water of 1: 5.75 to 1: 26.9, preferably 1: 7.33 to 1: 24.5, for example 1: 9.8 to 1: 17.1, such as 1: 13.4. For other hydrate-forming condensed gases the molar ratio of solidified gas to frozen water and total liquid is as before for C02. The gas hydrate C02 has the so-called structure I (SI). The above molar ratios are applied to make other SI gas hydrates by this method. Gas hydrates with the so-called structure II (Sil) can be prepared using gas: water / ice molar ratios that take into account the stoichiometry of the Sil gas hydrates. At the end of the second step, the vessel is sealed from the atmosphere before it is pressurized (usually by self-pressurization, since the solid CO 2 sublimes and, at the appropriate temperature and pressure, melts and boils).

Step (iii) In the third step liquid water and the hydrate-forming condensed gas and / or its sublimation or liquefaction products are allowed or made to come into contact to form the reaction mixture. It is most preferable that this occurs at a temperature at or below the maximum temperature at which the gas hydrate is stable. The contacting to form the reaction mixture can be effected by contacting the condensed gas and / or its sublimation products with liquid water alone or with an ice / liquid water mixture. This includes melting frozen water. When the separation of liquid water and hydrate-forming condensed gas occurs by the use of an ice plug, this ice plug can be melted with any suitable means, for example a heated jacket, hot air, hot water, etc., for put in contact the liquid water and the condensed gas. The fusion can be localized or produced by the general application of the fusion medium. If the hydrate-forming condensate gas is supported by a shelf of a platform, the requirement to melt an ice plug is avoided. In practice, an ice film (which is not as thick as an ice plug) will form through the vessel due to the conditions existing within it. However, this movie melts easily. The reaction mixture can be mixed with the aid of any suitable means, including rotating or tilting the vessel about its axis or a vertical axis. The reaction to produce the gas hydrate typically begins to develop in the third step of the method. The temperature of the reaction mixture in the vessel should not exceed the maximum temperature at which the gas hydrate is stable, and is preferably in the range of 0 ° C-5 ° C, preferably 0 ° C-2 ° C. . The temperature of the reaction mixture is maintained at or below the maximum temperature at which the gas hydrate is stable for a sufficient time to produce the gas hydrate. An additional freezing or cooling of the mixture is usually necessary. The temperature of the reaction mixture can be lowered to below the maximum temperature at which the gas hydrate is stable with the aid of any suitable means of heat extraction, for example water bath or cooling jacket comprising cooling liquid such as as brine and / or glycol, or evaporation of liquid, for example ammonia, if a jacketed vessel is used, either conventional refrigeration (e.g., cold storage) or any conventional freezing method (e.g., forced fast freezer). Typically, the gas hydrate product will be formed by subjecting the reaction mixture to freezing at rest by placing the vessel in a freezer, for example a forced fast freezer.

Removal of the product The fully solidified gas hydrate product can be removed from the vessel with the aid of any suitable means, for example, heat can be applied to the outer surface of the vessel to melt the part of the product in contact with a heated part of the vessel. vessel, thus helping the withdrawal. Suitable means to facilitate removal include the application of hot water, hot air or heated liners to the reaction vessel. Alternatively, the product can be removed from the vessel manually or mechanically.

Optional Ingredients The edible gas hydrate product can be prepared to include minor amounts of conventional ingredients of frozen confectionery products, such as flavors, colorants, etc.

Vessel The vessel can be any suitable vessel capable of withstanding the pressure increases that occur during the reaction to form the gas hydrate product, preferably being a pressure vessel. It is especially preferred that the vessel be freestanding and of a suitable size and shape so that it can be filled, maneuvered and emptied manually, for example by a person. A suitable vessel, and one that is particularly preferred, has an elongated reaction chamber, for example a substantially cylindrical reaction chamber formed by a vessel having narrow and parallel long sides. In terms of cost of the pressure vessel, it is advantageous that it is substantially cylindrical. To optimize the surface area of cooling and nucleation of the reactions and to minimize the costs, the vessel preferably has a high ratio of internal length to internal diameter in the range of 3: 1 to 20: 1, preferably 7: 1 to 20. : 1, and more preferably between 10: 1 and 15: 1. Although, for reasons of cost, substantially cylindrical vessels are preferred, they are also encompassed by the term "substantially cylindrical" pressure vessels that taper internally up to 20%, the base having an internal diameter smaller than the internal diameter of the vessel at its end cap. The vessel may be equipped with wheels (or the like) to allow its movement, and preferably is capable of being oriented through different positions, for example from vertical to horizontal. This change of orientation can be achieved with the aid of any suitable means, for example lathe, handles or any suitable automated means. Typically, the vessel has a lid, or other suitable closure means, which can be tightened or loosened as necessary, for example by bolts. Figure 1 shows a reaction vessel for use in the second embodiment of the method of the present invention. The vessel 1 has parallel sides 8, a removable lid 5, a base 6 and a platform 2 disposed in the center of the cavity 7 of the reaction vessel. The platform 2 comprises a support column 3 which extends upwards from the base 6 when the vessel is in vertical position. A shelf 4 is located in the column 3 at a suitable distance from the base 6 so that the shelf 4 is above the water located in the base 6 of the vessel 1 when the vessel is upright during use. The outer cross section of the shelf 4 is preferably substantially congruent with the internal cross section of the sides 8 of the reaction vessel. Preferably, the panel 4 is substantially horizontal. Preferably, the column 3 is arranged so as to provide an annular space in the product. A variant of the vessel shown in figure 1 has the platform 2, comprising the support column 3 and the panel 4, arranged as in figure 1, but the support column 3 does not extend above the panel 4 when the vessel It is in vertical position. An alternative form of the vessel is one in which the vessel is angled or bent so that it is substantially V-shaped or C. However, it has been seen in practice that this vessel form is less preferred than the vessel described above. , since it is more difficult to remove the product from them. The method of the invention is cheap and simple and can be fully or partially automated. If desired, any part of the method can be automated.

EXAMPLES The method of the present invention will be further illustrated with the help of the following example. Other examples and modifications that fall within the scope of the present invention will be apparent to the skilled person. Having described the invention in general, the following examples will be described, which clarify the preparation of C02 hydrate, to illustrate the method of the invention, which can also be applied to produce equally other desirable gas hydrates. The following examples are also a demonstration of the claimed product.

Example 1 - ice plug separation method A gas / ice hydrate composite was prepared as follows: They were added to a cylindrical pressurized vessel (mounted inside a wheel stand) 7 kg of pure water and 4 kg of ice so that the vessel contained a mixture of ice and water containing approximately 36% ice (before any amount of ice melted). The ice floated to the top of the water.

The floating ice was hardened by spraying on it powdered solid C02 (100 g) to reduce the temperature of the ice and form a firm ice plug through the surface of the water. An additional 2 kg of solid C02 was added to the vessel. The solid C02 was kept separate from the liquid water below by means of the ice plug and thus no reaction between the solid C02 and the liquid water took place at this time. A pulverized hydrate product composed of C02 / ice gas (100 g), taken from a previous preparation, was sprayed onto the solid C02 to ensure nucleation of the gas hydrate phase. The lid of the pressure vessel was put in place and secured with tight nuts to the desired torque using a pneumatic tool. The vessel was sealed (closing a tap on the lid) and manually moved from a vertical position to a horizontal position by rotating the vessel through 90 degrees so that it rested on its wheels. The sublimation of C02 cooled the part of the vessel that contained C02 (that is, the part that was the "upper" part when the vessel was full). The fusion of C02 produced a rapid cooling, and the vessel soon contained liquid CO2 in what was the upper part of the vessel when it was filled, a plug of ice and liquid water in what was the base of the vessel. The mixing of liquid C02 and liquid water was allowed to start by melting the ice plug by applying hot running water to the outside of the vessel. The vessel (which was balanced around its center of gravity) was gently swung by hand to provide sufficient agitation to mix the contents. In this step, the vessel contained a suspension mainly of C02 gas hydrate crystals in water. The vessel was allowed to stand for several minutes and then taken to a forced fast freezer to freeze the contents. The vessel was left at -35 ° C for 4 hours to allow the contents to freeze. When the contents had been given sufficient time to freeze, the pressurized vessel was removed from the freezer and the excess pressure was released from the vessel through a pressure relief tap before loosening the lid. The open vessel was returned to its almost vertical position, but with the end provided with the lid facing down to allow the removal of the frozen product. The gas hydrate product was removed from the vessel by running hot water on the outside of the vessel, thereby melting and separating the product upon melting the part of the product in contact with the vessel. The ratio of solid C02: water plus ice initially placed in the vessel was chosen so as to produce the desired carbon dioxide content in the product of the gas / ice hydrate composition, ie, in ml of C02 g_1. The water: ice ratio was selected so as to provide the correct heat content to drive the reaction to completion. The carbon dioxide content of the product was 55 ml of C02 g_1 of composite material. Gas / ice hydrate composites produced using only dissolved C02 typically contain up to 25 ml of C02 g "1., the method of Example 1 produces gas hydrate with a carbon dioxide content higher than that of a method using only dissolved gas.

Example 2 - platform separation method Example 1 was repeated, but using the cylindrical pressurized vessel of Example 1 modified to contain a platform comprising a support column and a shelf as shown in figure 1. Using the vessel of Figure 1, an annular ingot of gas / ice hydrate composite product is obtained. The mixture of ice and water of Example 1 was added to the vessel to a level that was below the platform shelf when the vessel was in the upright position. Solid C02 was added to the vessel on the platform so that it would not come into contact with any liquid or frozen water. The pulverized preformed product of C02 gas hydrate was sprayed onto the solid C02 disposed on the platform as in Example 1. The vessel was closed and the reaction mixture was formed and mixed as for Example 1. The method of freezing and removal of the gas hydrate product followed the method of Example 1. The method of Example 2 produced an edible gas hydrate having carbon dioxide equivalent to that of Example 1. It was found that Example 2 was particularly advantageous in terms of freezing time. required, while still providing an acceptable quantity of product for each batch.

Claims (17)

1. A method for producing a gas hydrate comprising the steps of; (i) filling a vessel with a quantity of liquid water and / or frozen water, (ii) adding to the vessel a quantity of condensed gas forming hydrate in such a way that the condensed gas does not come into contact with liquid water, (iii) ) contacting the condensed gas, and / or its sublimation or liquefaction products, at a suitable pressure, with the mixture of liquid and / or frozen water to produce a reaction mixture, and maintaining the reaction mixture at or below the maximum temperature at which the gas hydrate is stable, and at a suitable pressure for a sufficient time to produce the gas hydrate.

2. A method according to claim 1, wherein the hydrate-forming condensed gas comprises solidified carbon dioxide. A method according to claim 1 or claim 2, wherein step (i) comprises filling the vessel with an amount of liquid water and frozen water and adding thereto a quantity of hydrated, hydrate-forming, condensed gas. divided or granular, to form an ice cap on the liquid water. 4. A method according to claim 3, wherein in step (ii) an amount of condensed hydrate-forming gas is added to the ice plug formed in step (i). A method according to any one of claims 2 to 4, wherein step (iii) comprises melting an ice plug to contact the liquid water and the condensed gas forming hydrate, and / or its sublimation products / liquefaction, to form a reaction mixture. 6. A method according to claim 1, wherein in step (ii) an amount of condensed hydrate-forming gas is added to the vessel by placing it on a removable platform above the level of the frozen water and / or the liquid water in the tank. vessel. A method according to any one of the preceding claims, wherein pulverized, finely divided or granular preformed gas hydrate is added to the vessel in step (ii). A method according to any one of the preceding claims, wherein the hydrate-forming condensed gas, which contains a mixture of 10-80% by weight of water frozen in liquid water, is added to the vessel. 9. A method according to any one of the preceding claims, wherein step (iii) comprises freezing the reaction mixture. 10. A method according to claim 9, wherein the freezing is produced by placing the vessel in a forced fast freezer. A method according to any one of the preceding claims, wherein the condensed gas forming hydrate is C02 and the weight ratio of condensed C02: frozen water and total liquid in step (ii) is between 1: 2, 35 and 1:11. 12. A method according to claim 11, wherein the molar ratio of C02 condensed to frozen water and total liquid is from 1: 5.75 to 1: 26.9. A method according to any one of the preceding claims, wherein the vessel has an elongated reaction chamber, preferably with an internal length ratio of the vessel: internal diameter of the vessel of 3: 1 or more. 14. A method according to claim 13, wherein the vessel is a pressure vessel. 15. A gas hydrate obtainable by the method of any one of the preceding claims. 16. A reaction vessel having a base, parallel sides and a removable lid defining a vessel cavity with a platform disposed in the center of the cavity, the platform comprising a support column extending upwardly from the base when the vessel is in a vertical position, and a shelf located in the support column at a distance from the base to arrange the shelf on the column at a height that is above the content of the reaction vessel placed at the base of the vessel . 17. A reaction vessel according to claim 16, wherein the platform support column extends upwardly from the base to substantially the removable cover.