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Title:
THERMAL PROCESSING OF BEVERAGES WITH HYDROLYSIS MIXTURES OF ALDONIC ACIDS
Document Type and Number:
WIPO Patent Application WO/1993/004590
Kind Code:
A1
Abstract:
Preparing commercially sterilized aqueous coffee and tea extracts in hermetically sealed containers by sealing a container of coffee or tea extract. The extract contains a sufficient amount of an hydrolysis mixture of an aldonic acid and its lactones or a precusor so that the equilibrium pH of the extract is up to 4.6. The sealed container is processed at a temperature from about 180 °F to 210 °F for a period of from 3 to 10 minutes.

Inventors:
Buytendorp, Henry C.
Zenger, Richard D.
Application Number:
PCT/US1992/007587
Publication Date:
March 18, 1993
Filing Date:
September 09, 1992
Export Citation:
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Assignee:
AMERICAN NATIONAL CAN COMPANY.
International Classes:
A23F3/16; A23F5/24; (IPC1-7): A23F3/16; A23F5/24
Foreign References:
US4696580A
US4741911A
US4789553A
US4946701A
Other References:
A Complete Course in Canning, The Canning Trade Lopez, 1969, pages 115, 116, 129, 343-345.
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Claims:
WHAT IS CLAIMED IS:
1. A process for the preparation of commercially sterilized, potable, aqueous coffee and tea extracts in an hermetically sealed container comprising hermetically sealing in a container a coffee or tea extract containing a sufficient amount of an hydrolysis mixture of an aldonic acid and its lactones or a precursor thereof so that the equilibrium pH of the extract is up to 4.6 and maintaining the container at a temperature of from about 180°F to 210°F for a period of from about 3 to 10 minutes.
2. A process as in claim 1 wherein the equilibrium pH is from about .3 to 4.6.
3. A process as in claim 1 wherein the extract is sealed in the container under an inert gas.
4. A process as in claim 3 wherein the inert gas s nitrogen.
5. A process as in claim 3 wherein the inert gas s carbon dioxide.
6. A process as in claim 3 wherein the inert gas s a blend of nitrogen and carbon dioxide.
7. A process as in claims 1, 2, 3, 4, 5 or 6 wherein the temperature of the extract prior to sealing in the container is less than 180 F.
8. A process as in claims 1, 2, 3, 4, 5 or 6 wherein the temperature of the extract prior to sealing in the container is less than 180°F.
9. A process for the preparation of commercially sterilized, potable, aqueous coffee and tea extracts in an hermetically sealed container comprising the steps of: 1 forming an aqueous extract of coffee or tea and thermally processing said extract at a temperature of from about 180°F to 210°F, said extract containing a sufficient amount of an hydrolysis mixture of an aldonic acid and its lactones or a precursor thereof so that the equilibrium pH of the thermally processed extract is up to 4.6,.
10. hermetically sealing the extract in a container at a temperature of from aabboouutt 11880°F to 210°F and thereafter cooling; the total time that the extract is at a temperature of from about 180°F to 210°F being from about.
11. to 10 minutes.
12. 10 A process as in claim 9 wherein the aqueous extract is formed utilizing an hydrolysis mixture of gluconic acid and its lactones or a precursor thereof.
13. 11 A process as in claim 10 wherein the extract is hermetically sealed in a container at a temperature between 180°F and 210°F and permitted to cool as a rate such that the temperature of the extract is from about 180°F to 210°F for a period of from about 3 to 10 minutes.
14. 12 A process as in claim 9, 10 or 11 in which the equilibrium pH is from about 4.3 to 4.6.
15. A process for the preparation of commercially sterilized, potable, aqueous coffee and tea extracts in an hermetically sealed container comprising the steps of: 1 forming an aqueous extract of the coffee or tea and thermally processing said extract to at a temperature of from about 180°F to 210°F, said extract containing a sufficient amount of an hydrolysis mixture of an aldonic acid and its lactones or a precursor thereof so that the equilibrium pH of the thermally processed extract is up to 4.6,.
16. hermetically sealing the extract in a container under an inert gas.
17. the total time that the extract is at a temperature of from about 180°F to 210°F being from about.
18. to 10 minutes.
19. 14 A process as in claim 13 wherein the aqueous extract is formed utilizing an hydrolysis mixture of gluconic acid and its lactones or a precursor thereof.
20. 15 A process as in claim 14 wherein the extract is hermetically sealed in a container at a temperature between 180°F and 210°F and permitted to cool as a rate such that the temperature of the extract is from about 180°F to 210°F for a period of from about 3 to 10 minutes.
21. 16 A process as in claim 13, 14 or 15 wherein the equilibrium pH is from about 4.3 to 4.6.
22. A process as in claim 16 wherein the inert gas is nitrogen.
23. A process as in claim 16 wherein the inert gas is carbon dioxide.
24. A process as in claim 16 wherein the inert gas is a blend of nitrogen and carbon dioxide.
Description:
THERMAL PROCESSING OF BEVERAGES WITH HYDROLYSIS MIXTURES OF ALDONIC ACIDS

BACKGROUND AND OBJECTS OF THE INVENTION

This invention relates to thermally processed beverages. More specifically it relates to commercially sterile potable coffee and tea extracts. By "thermally processing", as used herein, is meant subjecting the extract to a time-temperature parameter which results in a "commercially sterilized" product as defined in Title 21 CFR Par 113 (Definitions, Sec. 13.2).

"Commercial sterility of processed foods means the condition achieved "(i) By the application of heat which renders the food free of "(a) Microorganisms capable of reproducing in the food under normal nonrefrigerated conditions of storage and distribution; and "(b) Viable microorganism (including spores) of public health significance; or

"(ii) By the control of water activity and the application of heat, which render the food free of microorganisms capable of reproducing in the food under normal nonrefrigerated conditions of storage and distribution".

Conventionally, coffee, tea and other potable liquid foods having a natural pH of 4.6 or higher, i.e. low acid foods, when they are intended to be sold as beverages for human consumption from hermetically

sealed containers undergo thermal processing to provide a commercially sterile product. It is also conventional to package the liquid food in a container under an inert gas such as nitrogen, carbon dioxide or other suitable gas. The gas has two functions. One is to provide a hostile atmosphere for the growth of aerobic microorganisms. The other is to provide additional structural integrity to the thin walled containers, such as aluminum cans often used in the purveyance of such drinks. The use of the gas permits several cans to be stacked one upon the other without danger that the lower members of the stack will collapse, and it minimizes denting or permanent distortion of the container caused by abusive handling.

A typical procedure for the preparation of a canned coffee beverage is described in international Application WO91/0019 which was published on January 10, 1991. The process of this patent publication features the use of an antioxidant selected from the group consisting of erythrobic acid, ascorbic acid and water soluble salts thereof in the preparation of " a co fee beverage which is packaged under an inert atmosphere comprising a mixture containing at least two of steam, carbon dioxide and nitrogen.

A somewhat similar process is described in U.K.

Patent Application 2,134,496 published August 16, 1984. Other procedures, which may be applicable to the preparation of commercially sterile coffee and tea extracts (hereinafter, for convenience sometimes

referred to more simply as coffee or tea) are known, for example from U.K. Patent Application 2,089,191 and U.S. Patent 4,674,267.

In the process of WO91/0019 referred to above, roasted pulverized coffee is extracted with hot water at about 210°F and the extract rapidly cooled to about 65 F. The antioxidant is added to the extract, the extract filled into the container and topped with the inert gas under pressure. Finally, the can is hermetically sealed and thermally sterilized at about 240°F.

The process, as will be seen, requires a specific commercial sterilization step at high temperature. One consequence of the high temperature thermal processing step is the necessity for high quality enamels and varnishes if the container is a metal container. Enamels are the materials coated on the inner surface of the metal container to inhibit reaction between the metal and the contained product. Varnish is the material coating the outside of the can to protect it from air oxidation and to provide a base upon which the label can be adhered or imprinted. If the container is plastic, it is necessary to select a plastic which can withstand the rigors of thermal processing to commercial sterilization without distortion.

Generally, these are the more expensive plastics. With glass containers, the rate at which the container is cooled from the thermal processing temperature must be

carefully controlled in order to avoid thermal shock which would introduce unwanted stresses into the glass making it susceptible to easy breakage.

The tops are sealed to the cans with a sealant material generally referred to as End Compound or

Sealing Compound. It may be a mixture of food grade synthetic rubber and clay type compounds, although other materials can be employed.

United States Patent 4,741,911 describes and claims the use of hydrolysis mixtures of aldonic acids and their lactones, preferably gluconic acid and its lactones, for the commercial sterilization of low acid foods. Two principal methods are disclosed. In one method, commercial sterilization is conducted on the low acid food prior to placing the food in the container and hermetically sealing. In the second method, the food is commercially sterilized after it has been hermetically sealed in the container. Although the patent clearly contemplates the use of hydrolysis mixtures of aldonic acids and their lactones for the commercial sterilization of potable coffee extracts and similar beverage foods, there is no specific disclosure of such beverages.

Commercial sterilization in accordance with the second method described in the patent is normally conducted in a retort. Typically, the retort is a substantially closed vessel in which the containers are subjected for a selected period of time to a

commercially sterilizing temperature usually employing high temperature steam or water under pressure. The containers may be stationary during the whole process or they may move through the retort on a conveyor mechanism. Some retorts are constructed so that the food to be sterilized is alternately subjected to high/low temperature cycles. Other retorts are designed to roll cans or turn them end for end to achieve product agitation and accelerate the transfer of heat to all parts of the contents (a stirring with an air bubble) .

The use of retorts for commercial sterilization markedly increases the costs of production. Commercial retorts may cost several million dollars. Additionally, the high temperatures employed in such procedures require the use of high quality enamels, varnishes and plastic as discussed above.

A further disadvantage of the high temperatures required for commercial sterilization is the deleterious effect on the organoleptic properties of the beverage, especially flavor and aroma. The taste of coffees, especially, is adversely affected by high temperatures. Additionally, some of the volatile oils responsible for the attractive aroma of fresh coffee may be heat sensitive and decompose during thermal processing.

An object of this invention is to commercially sterilize coffee and tea beverages for dispensing from a container without the disadvantages aforesaid.

Another object of this invention is to commercially sterilize coffee and tea beverages without the use of a retort.

Another object of this invention is to commercially sterilize coffee and tea beverages without adversely affecting the organoleptic properties of the beverage.

Another object of this invention is to commercially sterilize coffee and tea beverages under low process parameter conditions utilizing, for instance, the hot fill hold (HFH) method in which the filled container is held at a selected temperature below the initial temperature to permit cooling.

The process parameters referred to herein are the conditions under which a product of the invention has been thermally processed to commercial sterility. Principally, they are pH, temperature and time. With potable beverages such as are the subject of this invention, the usual commercial parameters are about 240°F to 275°F during a period of from about 15 to 35 minutes. A particular advantage of this invention is that it permits commercial sterilization at lower

temperatures for shorter periods of time without the use of retorts while preserving organoleptic properties.

SUMMARY OF THE INVENTION

It has now been discovered that commercially sterilized, potable, aqueous, liquid coffee and tea extracts can be prepared from coffee and tea which are low acid foods by a one step process in which the liquid extract containing a sufficient amount of an hydrolysis mixture of an aldonic acid and its lactones or a precursor thereof so that the equilibrium pH is 4.6 or below, preferably 4.0 to 4.6 is heated at a temperature of from about 180°F to 210°F for a period of from about 3 to 10 minutes. The coffee or tea substrate is preferably extracted with the hydrolysis mixture or it may be extracted with hot water, at a temperature which is below or the same as the temperature of thermal processing and the hydrolysis mixture or a precursor thereof added to the untreated extract prior to the actual thermal processing.

The selected temperature, pH and time of thermal processing are interrelated. Generally, higher temperatures are associated with high pH and longer treatment periods. Lower pH permits the use of lower temperatures and shorter heating periods.

After the extract has been prepared, selected volumes may be added to the container. The container is hermetically sealed in the conventional manner. The extract may, if desired, be packaged under inert gas or a blend of inert gases including, for example, carbon dioxide, nitrogen, or a mixture thereof. This procedure is often used with thin walled containers such as aluminum cans to improve the structural integrity of the can. The procedure is conventional and its application is well known and understood by those skilled in the art. In the practice of this invention, the packaging pressure is normally from about 15 to 25 pounds per square inch, although appreciable variations from this range are possible.

The period during which the extract is at elevated temperature i.e. the heating period is normally from about 3 to 10 minutes. It can be divided over different periods of the processing. For example, the extract can be held at a selected temperature range for commercial sterilization for a portion of the total period and thermal processing to commercial sterility completed after hermetic sealing, with or without nitrogen or other inert gas.

Alternatively, the extract can be formed at any selected temperature, cooled and thereafter thermally processed to commercial sterility. The skilled artisan can readily conceive of a variety of heating regimens for conducting the process of this invention. To insure commercial sterility of the product in the

hermetically sealed container, thermal processing in the container is conducted for approximately 3 minutes depending on pH and temperature so that the period of time the product is thermally processed in the container at the temperature range is normally about 3 minutes, although lesser period are acceptable at the lower end of the pH range.

The size of the container may affect the heating protocol. For instance, the extract at 205 F can be filled into large containers after heat treatment for a selected period and then allowed to cool. The cooling rate may be sufficiently slow so that the temperature will be above 180°F for a sufficiently long period of time so that commercial sterilization will be completed. This HFH process may be applied to smaller containers by holding them in a controlled environment such as an atmospheric steam tunnel or a hot water bath.

There are many advantages to the process of this invention, the most significant of which are; (1) the process parameters are appreciably lower than those normally employed for commercial sterilization of such products when the hydrolysis mixture of an aldonic acid and its lactones or a precursor thereof is not employed, (2) the organoleptic properties of the liquid extract are retained, (3) the process does not require a retort so that the costs and difficulties of commercial retorts are avoided and (4) because of the

lowered process parameters, the specifications of the containers can be less stringent and therefore, the containers less costly, as explained above.

The usual additives employed with such products such as non- dairy type lightness, sweeteners, lemon extract, orange flavors or any of the wide variety of flavoring agents currently utilized in coffee and tea drinks can be employed in the usual manner. Typically, flavoring agents will be added shortly before filling and hermetically sealing the extract to avoid loss of volatile components in the flavoring agent. As will be recognized by the skilled artisan, dairy products will not be employed in this invention because their isoelectric point is within the pH range of thermal processing with the result that coagulation and precipitation will take place.

Equilibrium pH refers to the pH of the liquid extract after thermal processing. More specifically, by equilibrium pH is meant the negative log of the hydrogen ion concentration of the blended product, taken in accordance with CFR 114.80(a) (1) , (2) and CFR 114.90, each incorporated herein by reference, but in any case taken not more than 24 hours after completion of the thermal process, i.e. when the application of heat is terminated. To achieve this pH status, it is advisable that all parts of the product be below 4.6 within 6 hours of the thermal process.

The aldonic acids which can be utilized with low acid extract foods accordance with this invention are prepared, for example, by oxidation of sugars or aldoses, preferably from those having six carbon atoms, although they could be prepared from those having five carbon atoms. Those acids prepared from sugars having six carbon atoms are talonic, galactonic, idonic, gulonic, mannonic, gluconic, altronic and allonic (although currently these acids, with the exception of gluconic, may be unavailable commercially). These acids are respectively derived from their aldoses- talose, galactose, idose, gulose, mannose, glucose, altrose and allose. Sugars having five carbon atoms are lyxose, xylose, arabinose and ribose. Those skilled in the art will understand from this disclosure regarding six and five carbon atom aldonic acids, that other acids which form their own lactone(s) and mixtures of other acids and their lactones, which perform the same functions and objectives of this invention, particularly regarding lowering the pH and regarding lack of an objectionable acid taste in the processed foodstuff, would be within the scope of this invention. For example, aldaric acids, i.e. dibasic acids such as glucaric which forms saccharo lactone, might be employed.

As indicated above, the liquid extracts of this invention can be produced by extracting the extractable food with water containing sufficient hydrolysis mixture or precursor thereof to achieve the desired equilibrium pH, or by adding the hydrolysis mixture or

its precursor to a previously formed aqueous extract of the extractable food. In the first case the formation of the liquid extract and the thermal processing thereof are essentially concurrent. In the latter case, the formation of the extract and the thermal processing thereof may be considered as successive. In any event, the liquid extract is thermally processed in an hydrolysis mixture of an aldonic acid and its lactones or a precursor thereof. The coffee or tea used to form the extract may be in an convenient form, e.g. powder, crystals, concentrated liquid or syrup and equivalent forms.

Any suitable method may be employed to form the hydrolysis mixture. While the acid might be added by itself (since the acid, when in contact with moisture or water in the foodstuff, will be converted to a mixture of the acid and its lactones) , doing so currently does not appear practical since aldonic acids are not known to be commercially available in crystalline form or in food grade. This is the case with preferred gluconic acid. These acids may be commercially available in technical grade in aqueous solutions. For example, gluconic acid is so available in aqueous solutions stated to be about 50% (by weight) gluconic acid. These aqueous solutions of the acid are equilibrium mixtures of gluconic acid and its lactones, glucono-delta lactone and glucono-gamma lactone.

The preferred method for providing the aldonic acid and its lactones is to utilize a precursor of the aldonic acid. A precursor of the acid herein means a liquid, material or compound which adds the acid to, or forms or provides it in the low acid foodstuff with which it is combined. Again, when the acid contacts moisture or water, it will convert partially to and will co-exist with its lactones. Precursors of these acids which can be employed include their lactones themselves (which can be said to be latent acids since they hydrolyze in water to form a mixture of the acid and its lactones) , mixtures of these lactones, and salts of the acids in combination with certain strong acids. For example, precursors of the preferred gluconic acid which can be employed include glucono- delta-lactone, glucono-gamma lactone, mixtures of these lactones, and gluconate salts in combination with the strong acid, hydrochloric. By far, the most preferred precursor for this invention is glucono-delta lactone (GDL) . It is commercially available in food grade as a free-flowing, odorless, white powder. It has a sweet taste. GDL is an inner ester of gluconic acid which when hydrolyzed forms gluconic acid. Hydrolysis occurs when GDL is combined with water. Hydrolysis of the glucono-delta lactone results in an equilibrium mixture of from about 55% to about 60% (by weight) gluconic acid and from about 45% to about 40% (by weight) of a mixture of glucono-delta lactone and glucono-gamma lactone. The rate of acid formation during hydrolysis is affected by the temperature, the pH value and concentration of the solution. Hydrolysis of delta

lactones tends to be more rapid than hydrolysis of gamma lactone. In the absence of heat, hydrolysis tends to be slow.

In a typical application of the process of this invention, tea leaves are treated with water at approximately 180° to 210°F to form an extract. Sufficient GDL is then added to produce an equilibrium pH below 4.6 which, depending on water conditions can range from approximately 0.5% to 2.0% GDL by weight. Sweeteners and/or lighteners can be added to this hot mixture which may require a brief holding period (the holding time is dependent on the temperature of the liquid, but should not exceed 15 minutes) to allow for hydrolysis of the GDL. The beverage is then filled into a container, hermetically sealed and held at about 180°F to 210°F for approximately 3 minutes, depending on the pH, to achieve commercial sterility before cooling the product to room temperature or below for subsequent storage and consumption. When light weight aluminum or steel carbonated beverage type cans are used liquid nitrogen or some other suitable gas is injected into the cans before sealing to obtain a positive pressure in the can for added container strength.

In another procedure, lyophilized or spray dried crystals of coffee or tea are reconstituted with a 180 - 210°F hot solution of GDL (approximately .5% - 2% in water) . Sweeteners or lighteners can be added as desired. The resultant liquid is then filled into a

container at a selected temperature within the range and held for approximately 5 minutes depending on pH and temperature to achieve commercial sterility. The container is then cooled to room temperature or below for subsequent storage and consumption. Liquid nitrogen or other suitable gas can be employed to provide added container strength.

To produce a potable coffee beverage, roasted and ground coffee beans are extracted with water at about 190°F containing 0.5% to 2.0% GDL. Sweeteners and/or lighteners can be added to the resultant drink before filling into containers at 180° to 210°F and subsequently hermetically sealing the container. After sealing, the containers are held for approximately 3 minutes, depending on pH and the selected temperature, before cooling. The containers can then be stored and shipped without refrigeration until the beverage is consumed. Liquid nitrogen may be employed as described above.

Generally it would be preferable to add the GDL into the water before heating and extracting the roasted and ground coffee beans or tea leaves. This would also be true when reconstituting dried coffee or tea powder or crystals with hot water. This helps to ensure the complete hydrolysis of the GDL such that the pH of the liquid would be below 4.6 during the holding time at elevated temperature.