MXPA99007374A - Method and apparatus for continuous reduction of microbial activity flow in a liquid product using carbon dioxide presuriz - Google Patents

Abstract

A continuous method using a pressurized flow of liquefied carbon dioxide to reduce microbial and / or enzymatic activity in a liquid product is described. A flow of liquefied carbon dioxide is combined with a pressurized flow of the liquid product. The pressure and temperature in the flow regions are maintained at a level which is sufficient to maintain the carbon dioxide in a continuous liquid state, but which does not freeze the liquid product. The pressurized mixture of carbon dioxide and liquid product flows through a reaction zone for a time sufficient to reduce harmful microorganisms and / or inactivate undesirable enzymes and then enters a plurality of expansion stages wherein the pressure of the The mixture is sufficiently reduced to evaporate the carbon dioxide by separation of the liquid product. Heat is applied in at least some of the expansion stages to prevent a cooling of the mixture flow to the freezing point of the liquid product. Heat can be applied to control the temperature of the liquid product such that it does not exceed a temperature at which harmful effects are experienced.

Description

METHOD AND APPARATUS FOR CONTINUOUS FLOW REDUCTION MICROBIAL ACTIVITY IN A LIQUID PRODUCT USING PRESURED CARBON DIOXIDE FIELD OF THE INVENTION This invention relates to a method and apparatus for processing liquids to reduce microbial and / or enzymatic activity in those and, more particularly, to the use of pressurized carbon dioxide to achieve reductions in microbial and / or enzymatic activity. .

BACKGROUND OF THE INVENTION There are many methods to improve the shelf life of liquid products such as orange juice, apple juice, milk, latex paints, peanut butter, soup, etc. Commercially, thermal methods such as pasteurization are the predominant methods used to improve the shelf life of liquid foods. Ultra-high pressure treatment is also used for liquid foods, but much less frequently. In high pressure treatment facilities, fluids containing microbial contamination are hydrostatically pressurized to kill most bacteria. In such systems, pressures are created that equal or exceed 21 1 1 kg / cm2 abs. Such hydrostatic treatment, however, does not destroy enzymes, is unsafe due to very high pressures, is a prolonged process, is batch instead of continuous, and is expensive due to the high capital costs of the equipment required. Other methods for shelf life of liquids include nuclear irradiation, ultra violet exposure and microwave application. These treatments are expensive and not widely used commercially at present. High pressure homogenization has been used to increase shelf life of orange juice and other citrus juices of simple gradation as described in the U.S. Patent. , No. 5, 232,726 of Clark et al. It is described that a citrus juice that is processed is subject to a high pressure of approximately 1055.5 kg / cm2 abs, the result being a significant reduction in biological activity in the juice. Carbon dioxide has been used to inactivate enzymes in foods and reduce microbial populations in fruit juices as described in the U.S. Patent. , No. 5,393,547 to Balaban et al. Balaban et al. Describes a method for inactivating enzymes in liquid food products where the food is exposed to pressurized carbon dioxide which, in turn, produces a carbonic acid solution with a pH that is sufficiently low to irreversibly inactivate enzymes in the liquid food. The method of Balaban et al. Is indicated as being applicable to food processing either in batch mode or continuous mode. Balaban et al. Further indicates that super-critical carbon dioxide is introduced at a sufficient rate to allow enough of it to dissolve in the feed to activate the enzymes. After the enzymatic inactivation, the feed flows to a section where the pressure is reduced and the carbon dioxide released can be recycled to repeat its use. U.S. Patent No. 5,704,276 to Osajima et al. Describes a method for continuous deactivation of enzymes in liquid foods, using a supercritical form of carbon dioxide. Osajima et al. Indicate that the density of the supercritical fluid is less than that of the liquid food and that the supercritical carbon dioxide is continuously injected into the liquid food and is separated from it at a later stage of the process. Osajima and colleagues also indicate that their process deodorizes the liquid food and removes volatile components. Arreóla y colaboradores ^ n "Effect of Super-critical Carbon Dioxide in Microbial Populations in Orange Juice of Simple Graduation", Journal of Food Quality, Volume 14, (1991), pp. 275-284, describe the effect of super-critical carbon dioxide on microbial populations in orange juice. Using a batch process, Arreóla and colleagues concluded that treatment with high pressure carbon dioxide resulted in microbial reduction in orange juice of simple graduation, even at low temperatures. In addition, they conclude that a combination of high pressure, and shear forces to which the orange juice is subjected during depressurization and lower pH due to the temporary formation of carbonic acid may have additional inhibitory effects on the normal flora within the juice. orange.

During the processing described in this work, the minimum temperature used was 35 ° C. It is an object of this invention to provide an improved method and apparatus for reducing microbial and / or enzymatic activity in liquid products. It is a further object of this invention to provide a method and apparatus for reducing microbial and / or enzymatic activity in liquid products using pressurized carbon dioxide, wherein the processing temperature at which the liquid is held does not detrimentally affect the liquid products. It is still another object of this invention to provide a continuous flow method and apparatus for reducing microbial and / or enzymatic activity in liquid products using pressurized carbon dioxide.

BRIEF DESCRIPTION OF THE INVENTION A continuous method is described which uses a pressurized carbon dioxide flow for the reduction of microorganisms present in the liquid product and / or the inactivation of one or more enzymes in a pressurized flow of the liquid product. The pressure in the flow regions is maintained at a level which is sufficient to keep the carbon dioxide in dense phase, but at a temperature that does not freeze the liquid product. The pressurized mixture of carbon dioxide and liquid flows through a reaction zone for a sufficient time to reduce harmful microorganisms and inactivate undesirable enzymes and then enters a plurality of expansion stages where the pressure of the mixture flow is decreased sufficiently to allow the separation of carbon dioxide from the liquid product. Heat is applied in at least some of the stages of the expansion to prevent a cooling of the mixture flow to the freezing point of the liquid product. Heat may be applied to prevent freezing of the liquid product to control the temperature such that it does not exceed a temperature at which damaging effects are experienced. (Freezing and excessively high temperature can have negative effects on the quality of the juice, temperatures above 40 ° C begin to degrade the product). The present invention is contemplated for use with any fluid that can be transported through a conduit, including for example, beverage products such as juices and milk, semi-liquid foods such as mayonnaise, salad dressings, soup and cottage cheese, and other fluids such as sterile paint and injectables.

BRIEF DESCRIPTION OF THE DIAMETER The Figure is a schematic flow diagram of the apparatus that performs the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to the Figure, pressurized carbon dioxide is fed from the carbon dioxide supply 10 through the optional pressure regulator 12 to the pump 14 which increases the pressure of the dioxide flow. The carbon dioxide is then fed through a check valve 16 to a confluence 18. The carbon dioxide is pressurized in the pump 14 to avoid any boiling of the dense phase carbon dioxide during later stages of the process. Similarly, liquid product is fed from a tank for feeding liquid product through a valve 20 to a pump 24. The pump 24 raises the supply pressure of the liquid product to the same level as the dense phase carbon dioxide leaving the pump 14. The feed of Pressurized liquid product passes through check valve 26 to confluence 18 where it is combined with the pressurized flow of carbon dioxide. The mixture of the liquid product and carbon dioxide then passes to an in-line mixer 28 essentially comprising a baffle-filled conduit that perfectly mixes the carbon dioxide and liquid product streams. Of course, other mixers can be used that achieve a desired level of liquid product / carbon dioxide mixing. The liquid mixture leaves the mixer 28 in line and is further pressurized by the action of the pump 30 at a process pressure. Depending on the specific liquid product feed, the process pressure will vary as a result. It is preferred that the process pressure be within the range of 21.1 kg / cm2 abs to 1407 kg / cm2 abs. If orange juice is being processed as a liquid food, a preferred range of pressure is approximately 123 kg / cm2 abs to approximately 154.8 kg / cm2 abs.

Once the liquid mixture leaves the pump 30, it enters a reaction zone 32 which is of adequate size and length to provide sufficient contact time (or residence) for the carbon dioxide and the liquid product to interact in a manner which reduces microorganisms and / or inactivates undesirable enzymes present in the liquid product. The selected residence time will depend on the liquid product to be processed and its flow rate, as well as the size and length of the reaction zone. It is preferred that the residence time in the reaction zone be in the range of about 1.0 to about 15.0 minutes. For example, to process orange juice, at a flow rate of 20-200 ml / min in a reaction zone that has a length of approximately 6.1 meters and a pipe size of approximately 7.9 mm internal diameter (ID), the preferred residence time is from about 1.5 to 13.0 minutes, and more preferably about 3.0 minutes of residence time. As the liquid mixture stream leaves the reaction zone 32, it enters one or more interaction chambers 34 (optional) where high shear forces are applied which enable a rupture of microbial cell walls in the liquid mixture. Such action allows an additional reduction of microbial populations in the liquid mixture. The high-cut interaction chambers that are suitable for inclusion in this process are manufactured by the Microfluidics International Corp., Newton, Massachusetts.

In this step, the carbon dioxide / pressurized liquid product mixture must be depressurized in order to avoid freezing of the liquid product (due to the Joule-Thompson cooling effect of the expansion of carbon dioxide). If the pressure is lowered to the ambient in one or two stages, a very large heat exchange or application of complementary heat is required. If too much heat is added to the mixture, damage will occur to the liquid product, either in its flavor characteristics or its pomposition. Also, important volatiles such as flavor components can be eliminated. Consequently, it has been found that substantial care must be taken during the depressurization action to keep the liquid mixture within two limits. The lower limit is the freezing point of the liquid mixture and the upper limit point is the maximum temperature at which the liquid product can be held, without damaging the product. In the case of orange juice, the maximum temperature is about 50 ° C and the minimum temperature is about 0 ° C. Consequently, when a pressure reduction scheme is chosen, a pressure / enthalpy chart for dioxide is followed of carbon to determine the optimal heating pressure and temperature necessary- for plural stages of pressure reduction, while maintaining (in this example) the orange juice at a temperature between that which will damage its flavor and freezing point. It has been determined that at least two depressurization steps are required, but it is preferred that they be at least three stages.

Returning to the Figure, the first depressurization step includes a pressure control device 36, such as a pressure backup regulator, followed by a heat exchanger 38. Assuming that the liquid product being processed is orange juice and that the process pressure within the reaction zone 32 and the interaction chamber 34 is approximately 140.74 kg / cm2 abs, a first depressurization step 35 reduces the pressure of the liquid mixture to approximately 42.22 kg / cm2 abs and applies sufficient heat through the heat exchanger 38 to maintain the liquid mixture at about 30 ° C. A second depressurization step 40 includes a pressure control device 42 and heat exchanger 44 which, in combination, reduce the pressure of the liquid mixture at approximately 17.6 kg / cm2 abs and maintains its temperature at approximately 30 ° C. A final stage 46 depressurizer includes only a pressure control device 48 for reducing the pressure of the liquid mixture to the point where the dense phase carbon dioxide will evaporate and can be separated from the liquid products while minimizing the loss of important volatile components. In the modality shown in the Figure, no heat exchanger subsequent to the pressure control device 48 is required, however, one may be provided, if required, to keep the liquid mixture within the required range of temperature. As the liquid mixture leaves the pressure control device 48, it enters a liquid product / carbon dioxide separator vessel or other collection device under reduced pressure. There, the carbon dioxide vapor is separated from the liquid product, captured and passed through a filter 52, flow meter 54 (if desired) and is either vented to the atmosphere or passed through a stage of depressurization (not shown) to recycle it to the supply 10 of carbon dioxide. Well 56 of liquid product can then be drained through valve 58 for further processing and / or use. It is understood that the continuous process method shown in the Figure is made practical by the multiple depressurization steps that allow the liquid mixture to be maintained within the aforementioned temperature limits. As a result, a continuous process for reducing microbial and / or enzymatic activity is achieved while overcoming the main problem of the prior art, ie, batch processing which is an undesirable and undesirable processing procedure in a commercial environment. If the carbon dioxide gas is going to be recycled, it is preferred that it be passed through a coalescing filter to remove droplets of the processed liquid product. Then, the gas is recondensed to the liquid state by passing through a condensing heat exchanger. In addition, to ensure the removal of the dissolved carbon dioxide in the processed liquid product, a liquid product / carbon dioxide separator downstream of the separator tank 50 may include means for deaeration. The resulting gas, which remains after processing, may carry additional valuable aromas and / or flavors. To recover or remove such flavors or aromas, a method such as condensation or absorption may be used. It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications may be devised by those skilled in the art without departing from the invention.

Claims (10)

1. REVIVAL NAME IS 1. A continuous method for reducing microorganisms in a liquid product, said method comprising the steps of: a) combining a pressurized flow of said liquid product with a flow of pressurized liquefied carbon dioxide to create a pressurized mixture in a flow state, said dioxide of carbon at a pressure sufficient to maintain it in a liquid state and at a temperature that does not freeze said liquid product; b) flowing said pressurized mixture through a reaction zone for a sufficient time to reduce microorganisms in said liquid product; c) feeding said pressurized mixture from said reaction zone through plural expansion stages wherein the pressure of said mixing flow is lowered to evaporate the liquefied carbon dioxide in said mixing flow; and d) applying heat in at least some of said expansion steps to said mixing flow to prevent a cooling of said carbon dioxide causing a freezing of said liquid product.
2. 2. The continuous method as recited in claim 1, wherein step d) maintains a temperature of said mixture within a range between a freezing temperature of said liquid product and approximately 60 ° C.
3. 3. The continuous method as it was mentioned in claim 1, wherein step c) feeds said mix flow through two or more expansion steps to evaporate said liquefied carbon dioxide.
4. 4. The continuous method as recited in claim 1, wherein step a) feeds said pressurized flow of said mixture into said reaction zone at a pressure within a range of about 21.1 1 kg / cm2 abs to about 1407 kg / cm2 abs.
5. The continuous method as recited in claim 1, wherein step b) maintains said pressurized flow of said mixture in said reaction zone for a duration of about 5 seconds.
6. 6. The continuous method as recited in claim 1, wherein said liquid product is a food product and said method inactivates one or more undesirable enzymes.
7. 7. A continuous method for reducing microorganisms and inactivating one or more undesirable enzymes in liquid juice product, said method comprising the steps of: a) combining a pressurized flow of said liquid juice product with a flow of pressurized liquefied carbon dioxide to creating a pressurized mixture in a state of flow, said carbon dioxide at a pressure sufficient to maintain it in a liquid state and at a temperature that does not freeze said liquid juice product; b) flowing said pressurized mixture through a reaction zone for about 1.0 to about 15 minutes to reduce said microorganisms present therein and inactivating said one or more undesirable enzymes; c) feeding said pressurized mixture from said reaction zone through two or more expansion stages wherein the pressure of said mixture flow is lowered to approximately 140.74 kg / cm2; and d) applying heat in at least some of said expansion steps to said mixing flow to prevent a cooling of said carbon dioxide causing a freezing of said liquid juice product.
8. 8. The continuous method as recited in claim 7, wherein the juice is a vegetable or fruit juice and wherein the time of contraction in step b) is about 1.5 to about 13 minutes.
9. 9. The continuous method as recited in claim 7, wherein step d) maintains a temperature of said mixture within a range between a freezing temperature of said liquid juice product and approximately 30 ° C.
10. 10. The method continuous as mentioned in claim 8, wherein said juice is orange juice, said contact time is approximately 3 minutes, and wherein step d) maintains a temperature of said mixture at approximately 30 ° C. RESU M EN A continuous method using a pressurized flow of liquefied carbon dioxide to reduce microbial and / or enzymatic activity in a liquid product is described. A flow of liquefied carbon dioxide is combined with a pressurized flow of the liquid product. The pressure and temperature in the flow regions are maintained at a level which is sufficient to maintain the carbon dioxide in a continuous liquid state, but which does not freeze the liquid product. The pressurized mixture of carbon dioxide and liquid product flows through a reaction zone for a time sufficient to reduce harmful microorganisms and / or inactivate undesirable enzymes and then enters a plurality of expansion stages wherein the pressure of the The mixture is sufficiently reduced to evaporate the carbon dioxide by separation of the liquid product. Heat is applied in at least some of the expansion stages to prevent a cooling of the mixture flow to the freezing point of the liquid product. Heat may be applied to control the temperature of the liquid product such that it does not exceed a temperature at which detrimental effects are experienced.