JP4750011B2 - Method for stabilizing liquid coffee - Google Patents

Description

  The present invention relates to a method for producing liquid coffee and liquid coffee produced by the method. Specifically, the present invention relates to liquid coffee having improved storage stability and a method for producing the same. More specifically, the present invention relates to a method for producing liquid coffee that can suppress an increase in acidity during storage of liquid coffee, improve a flavor retention period, and maintain initial production quality over a long period of time.

  Liquid coffee products are complex systems that contain a large amount of moisture, and also include various components such as acid components, acid component precursors, flavor components, sugars, amino acids, proteins, and lipids. Particularly during storage of liquid coffee products, the acid component precursor may be hydrolyzed to produce an acid component, which reduces the pH of the liquid coffee and increases the acidity in terms of functionality. Can be no flavor. Such component change is the biggest factor that reduces the commercial value of liquid coffee during storage. Therefore, various proposals have been made on methods for suppressing the increase in acidity of liquid coffee products.

For example, there is a method of increasing the initial pH of a liquid coffee product with sodium hydrogen carbonate (Patent Document 1), but even if the initial pH is increased in this way, the pH can still decrease during storage. There is a method of increasing the pH with a strong alkali and converting the precursor of the acid component to an acid component, and then adding the acid to return the pH (Patent Document 2). However, the salt produced by the added alkali and acid makes the flavor of liquid coffee There is a risk of impact. Even in the method of adding a weak alkali and an acid and suppressing the increase in acidity by buffer action (Patent Document 3), there is a concern about the influence on the flavor because a large amount of weak alkali and acid are used.
JP-A-6-292509 Japanese Laid-Open Patent Publication No. 10-215771 Japanese Laid-Open Patent Publication No. 2004-187517

  An object of the present invention is to suppress the change in the components of liquid coffee as much as possible, thereby improving the shelf life of the product.

As a result of intensive studies to solve the above problems, the present inventors can store liquid coffee for a long period of time by heat-treating liquid coffee and then adding alkali to the liquid coffee after heat-treatment. As a result, the present invention has been completed. Thus, embodiments of the present invention are as follows:
1. Heat treating liquid coffee, changing the acid component precursor contained in the liquid coffee to an acid component, adding alkali to the heat-treated liquid coffee, and neutralizing the acid component generated in the above step A process for producing a stabilized liquid coffee comprising:
2. The method according to 1 above, further comprising a step of adding alkali to the liquid coffee prior to the heat treatment.
3. 3. The method according to 1 or 2 further comprising a step of adding a coffee aroma component to the heat-treated liquid coffee after the heat treatment.
4). 4. The method according to any one of 1 to 3 above, wherein the temperature of the heat treatment is 120 ° C. or more and 150 ° C. or less, and the treatment time is within one hour.
5. 5. The method according to any one of 1 to 4 above, wherein the liquid coffee is sugar-free or sweetened black coffee that does not contain milk.
6). 6. The method according to any one of 1 to 5 above, wherein the temperature of the heat treatment is from 135 ° C. to 145 ° C., and the treatment time is from 1 minute to 10 minutes.
7). Liquid coffee manufactured by the method according to any one of 1 to 6 above, wherein the initial pH is 5.2 to 6.8.
8). 8. The liquid coffee according to 7 above, wherein the pH drop after storage at room temperature for 1.5 months is 0.3 or less.
9. 9. The liquid according to 7 or 8 above, wherein the increase in titrated acidity up to the end point pH 6.1 after storage at room temperature for 1.5 months is 0.9 [ml-0.1 mol NaOH / g-ss] or less coffee.
10. Liquid coffee as described in any one of said 7-9 whose increase rate of the content quinic acid after preserve | saving for 6 months at room temperature is 7% or less compared with this storage start.
11. The increase rate of the quinic acid contained after the liquid coffee produced by the method according to any one of 1 to 6 above and stored at room temperature for 1.5 months at room temperature for 4.5 months is Liquid coffee as described in any one of said 7-9 which is 4% or less compared with 4.5 months before storage start.
12 The liquid coffee product which added the additive selected from a sweetener, a fragrance | flavor, milk, and these mixtures to the liquid coffee as described in any one of said 7-11.

Hereinafter, the present invention will be described in detail.
In the present invention, “liquid coffee” refers to a product obtained by roasting and pulverizing green coffee beans, extracting the coffee beans with hot water or water, and concentrating or diluting as appropriate. The coffee beans to be used may be any kind such as Arabica, Robusta, Revelica, or a hybrid of these, or may be used by blending them. For roasting of coffee beans, any roasting method such as direct fire, hot air, far infrared ray, microwave, charcoal fire, ceramic, superheated steam, etc. may be used, and the roasting degree is light, cinnamon, Medium, high, city, full city, french, italian and charcoal roasts can be used. The roasted coffee beans obtained by pulverizing the roasted coffee beans using a general pulverizer, a roll mill, etc., are used for roast pulverized coffee (coarse, intermediate, intermediate, fine, etc. (Including those having a shape) and extracting with water, hot water or pressurized hot water. The extraction method may be a general filtration method, a boiling method, a dipping method, or a pressure extraction method.

  The liquid coffee obtained in this way is a system containing various components such as water, acid components, acid component precursors, flavor components, sugars, amino acids, proteins, lipids, and usually soluble solids concentration (Brix concentration) ) 0.5-50%, pH 4.5-6.0. Among these, the “acid component precursor” particularly refers to a component that can be changed to an acid component with heat treatment or the passage of time, for example, esters, ethers, which generate an acid by hydrolysis with water, Includes lactones and the like. The change of the “acid component precursor” to the acid component greatly affects the flavor of the liquid coffee. Liquid coffee originally contains acid components (for example, chlorogenic acids, quinic acid, caffeic acid, and other organic acids), and sourness is an important factor in evaluating the flavor of liquid coffee. . However, if the acid content is too high, so-called sour coffee is produced, and many consumers dislike it. Immediately after making liquid coffee, it can be adjusted to an appropriate sourness that is most favored by consumers.However, if the acid component precursor is changed to an acid component during storage, the sourness of liquid coffee increases. As a result, the commercial value of the product may decrease, and it may eventually have a sour taste that it cannot withstand. From the viewpoint of such an increase in sourness, the shelf life of conventional liquid coffee products has generally been set to 6 months. Controlling the production of acid components in liquid coffee is therefore important in determining product shelf life.

  In the present invention, the liquid coffee obtained as described above is first heat-treated. When the liquid coffee is heated, the acid component precursor contained in the liquid coffee reacts with water to be hydrolyzed and converted into an acid component. In order to change the acid component precursor to an acid component, it is preferably heated to 100 ° C to 180 ° C, more preferably 120 ° C to 150 ° C, and most preferably 135 ° C to 145 ° C. In addition to heating the liquid coffee in a predetermined amount of reactor, the coffee liquid is heated to a predetermined temperature through a plate-type or tube-type heat exchanger, and the metal tube or stainless steel tube is further maintained while maintaining the temperature. It can also be carried out by holding the time until the coffee liquid passes through. When liquid coffee is heated and passed through a metal tube while maintaining the temperature, the heating time can be adjusted by adjusting the flow rate or the length of the metal tube, generally several seconds to 10 minutes, preferably 1 It can be heated for a period of 7 minutes to 7 minutes, most preferably 1.5 minutes to 6 minutes. When the liquid coffee is heat-treated, the concentration of the acid component increases, and accordingly, the pH of the liquid coffee decreases to 4.0 to 5.5.

  The alkali is then added to the liquid coffee having an increased acid component concentration. When an alkali is added, the acid component is neutralized to form a salt, and the pH increases accordingly. It is preferable to add an alkali in such an amount that the acid component contained in the liquid coffee is almost neutralized. For that purpose, the pH of the liquid coffee is adjusted to about 5 to 7, preferably about 5.5 to 6.5. Good. Although strong alkalis such as sodium hydroxide and potassium hydroxide can be used as the alkali, it is preferable to use weak alkalis such as calcium carbonate, sodium hydrogen carbonate, sodium carbonate and potassium carbonate.

The pH-adjusted liquid coffee is mixed with milk, sugars, fragrances, coloring agents and the like as necessary, and then subjected to necessary sterilization treatment by a method well known to those skilled in the art, and then packed into a final product.
The liquid coffee product obtained by such a method has decomposed almost all of the acid component precursor originally contained in the liquid coffee, that is, almost all components that can be converted into acid components have been eliminated. Therefore, an increase in the acid component during storage is suppressed, and the storage period is greatly extended.

  Prior to the method of the present invention, an alkali component can be first added to liquid coffee and then heat-treated. First, when alkali is added, the pH of the liquid coffee rises to about 6 to 7. However, when heat treatment is performed in this state, the acid component precursor contained in the liquid coffee can be efficiently lost.

  When there is a possibility that the scent of coffee is affected by the heat treatment, it is preferable to add a coffee scent component to the liquid coffee after the heat treatment in the method of the present invention. The coffee scent component refers to a product obtained by removing a volatile component that constitutes a coffee-specific scent, and is considered to be a mixture of various aldehydes, pyrazines, esters, ketones, and the like. By returning such a scent component to the liquid coffee after the heat treatment, it is possible to obtain a liquid coffee product in which only the acid component precursor has disappeared without reducing the scent of the coffee.

  The liquid coffee produced by the method of the present invention has an initial pH of 5.2 to 6.8, and the pH reduction value after storing it at room temperature for 1.5 months is preferably 0.3 or less. . Further, after the liquid coffee produced by the method of the present invention is stored at room temperature for 1.5 months, the increase in titrated acidity up to the end point pH 6.1 is preferably 0.9 [ml-0.1 mol NaOH / g-ss. It is the following.

The increase rate of the contained quinic acid after storing the liquid coffee produced by the method of the present invention at room temperature for 6 months is preferably 7% or less as compared to before the start of the storage.
Furthermore, after the liquid coffee produced by the method of the present invention was stored at room temperature for 1.5 months after the production, and further stored at room temperature for 4.5 months, the increase rate of quinic acid contained was 4.5 months. It is preferably 4% or less as compared to before storage.

In the present invention, “preservation” means that liquid coffee is packed in a sterilized plastic bottle or the like and stored at a predetermined temperature without opening the stopper.
In the above, the accelerated test corresponding to the state of “storage at room temperature for 1.5 months” is “storage at 40 ° C. for 1 week”, and the acceleration test corresponding to the state of “storage at room temperature for 6 months” is “4 weeks storage at 40 ° C.”. Therefore, values such as the above-mentioned pH decrease value and increase rate of contained acid can also be obtained by corresponding accelerated tests.

  In this specification, the term “liquid coffee product” includes any of “coffee”, “coffee beverage”, “soft drink with coffee” and “milk beverage” based on the “Fair Competition Rules for Labeling Coffee Drinks”. Shall be.

  Further, the liquid coffee product that can be produced by the method according to the present invention can include, for example, bottling, canning, retort pouch products, and PET bottled products, and is particularly effective when producing PET bottled products. It is expected.

  The liquid coffee product produced by the method of the present invention suppresses the generation of acid components during storage, so that the change in flavor during storage is minimized, thus extending the storage period (ie, shelf life). It becomes possible.

BEST MODE FOR CARRYING OUT THE INVENTION

A method for carrying out the method of the present invention will be specifically described.
The liquid coffee used in the method of the present invention can be produced using a conventional method for obtaining liquid coffee in the food industry. The coffee beans to be used are not limited in variety, production area, quality, and coffee beans roasting method, crushing method and extraction method. The pH of the obtained liquid coffee is about 4.5 to 6.0.

  The liquid coffee is heated to 120 to 150 ° C. and passed through the metal tube while maintaining the temperature, thereby performing a heat treatment. The heat treatment time can be adjusted by adjusting the length of the metal tube and the flow rate through which the metal tube passes, and for example, it is preferable to heat for about 1 to 10 minutes. The pH of the liquid coffee obtained by the heat treatment is lowered to about 4 to 5.5. This is because the acid component precursor contained in the liquid coffee is hydrolyzed by the heat treatment to produce an acid component.

Next, an alkali component is added to neutralize the acid component thus produced. As the alkali component to be added, it is preferable to use a weak alkali component that is acceptable in the food industry, such as sodium hydrogen carbonate or calcium carbonate. Such a weak alkali component is added, and the pH of the liquid coffee after the sterilization treatment described below is adjusted to about 5 to 7, preferably 5.5 to 6.8.
Liquid coffee that has been subjected to heat treatment and alkali treatment is diluted with water as necessary, preferably adjusted to a Brix concentration of 1% to 3%, and sweeteners, fragrances, and milk are added as appropriate, and sterilization treatment (ultra-high temperature instant sterilization) (According to the method (UHT sterilization method) etc.) and can be packed into a liquid coffee product.

As another aspect, the heat treatment can be performed after the alkali is added prior to the heat treatment. In this case, since both heat treatment and sterilization can be performed, the sterilization process can be omitted and the container can be packed as it is to obtain a liquid coffee product.
As another aspect, prior to carrying out the method of the present invention, a coffee scent component can be previously separated from liquid coffee using a volatile component separation device or the like. It is desirable that the volatile coffee scent component thus separated is refrigerated or frozen. While the liquid coffee is heat-treated by the method of the present invention, the volatile coffee scent component may volatilize. By returning it, it becomes possible to obtain a liquid coffee product in which only the acid component precursor has disappeared without reducing the original aroma of coffee. As the coffee scent component, a commercially available coffee scent component can be used in addition to the one previously separated from the liquid coffee.

Comparative Example 1
A deeply roasted coffee bean blended with Colombia, Brazil, and Indonesia was ground and thinned and extracted with hot hot water to obtain a coffee extract with a Brix concentration of 10%. This extract is diluted with water to a concentration of 1.55%, sodium hydrogen carbonate (Tosoh Corporation) is added so that the pH after sterilization becomes 5.7, and ultra high temperature instant (UHT) sterilizer is used. Sterilization was performed at 133.8 ° C. for 39.4 seconds. A 500 milliliter PET (PET) bottle was hot packed at about 85 ° C.
Example 1
The coffee extract obtained in the same manner as in Comparative Example 1 was heat-treated at 138 ° C. for 5 minutes using a heat treatment apparatus (experimental sterilizer FPO-7845, Nippon APV Co., Ltd.). The pH of the coffee extract before the heat treatment was 4.9. The pH after the heat treatment dropped to 4.6. The coffee extract after the heat treatment was diluted with water to a Brix concentration of 1.55%. Next, sodium hydrogen carbonate (Tosoh Corporation) was added so that the pH after sterilization was 5.7, and sterilization was performed at 133.8 ° C. for 39.4 seconds using a UHT sterilizer. A 500 ml plastic bottle was hot-packed at about 85 ° C.
Sensory test The liquid coffees of Comparative Example 1 and Example 1 were placed in a constant temperature bath at 40 ° C., pH values were measured after 1, 2, 3 and 4 weeks, respectively, and a sensory test was conducted using a specialized panel. A typical PET bottle liquid coffee product has a shelf life of 6 months at room temperature, but 4 weeks at 40 ° C. is an accelerated test corresponding to this period.

  The results are shown in Table 1.

In the table, the sourness is a sensory evaluation value from "no acidity is recognized ... 0" to "very sourness ... 10".
As is apparent from the table, the liquid coffee subjected to the heat treatment has a small pH change and an increase in sourness.
Example 2
Sodium bicarbonate was added to the coffee extract obtained in the same manner as in Example 1 to adjust the pH to 6.3. Next, heat treatment was performed at 138 ° C. for 5 minutes in the same heat treatment apparatus as in Example 1. With this treatment, the pH of the liquid coffee was 5.7. The solution was diluted with water to a Brix concentration of 1.55%, and sterilized at 133.8 ° C. for 39.4 seconds using a UHT sterilizer. A 500 ml plastic bottle was hot-packed at about 85 ° C. The same acceleration test and sensory test as described above were performed. The results are shown in Table 2.

  The liquid coffee of Example 2 has very little pH change, and the increase in sourness is effectively suppressed.

Table 3 shows the analytical data of the acids contained in Comparative Example 1 and Example 2.
Here, with respect to the amount of quinic acid, Example 2 has a higher initial concentration than that of Comparative Example 1, and the increase during storage is small. This means that the quinic acid precursor, such as quinic acid lactone, has been changed to quinic acid by heat treatment, so that there is no increase during storage. Since the quinic acid produced by the heat treatment has already been neutralized at the stage of commercialization, it can be said that the initial acidity of the product is not too strong and the acidity does not increase during storage.

  Table 4 shows data on the titratable acidity (end point pH 6.1) of Comparative Example 1 and Example 2 and the amount of change of quinic acid with 40 ° C. storage.

The liquid coffee of Comparative Example 2 was stored frozen at −40 ° C. as a control for the initial quality product, and the taste test of the samples of Comparative Examples 1 and 2 stored at 40 ° C. for 1 month was performed. It was.

The preference test is a percentage of which 18 panels drink each sample and which sample is preferred.
The results are shown in Table 5.

In the product stored at 40 ° C. for 1 month in Comparative Example 1, a decrease in preference was recognized with a significance level of 5% compared to the product stored frozen at −40 ° C. However, the 40 ° C. 1 month storage product of Comparative Example 2 maintained the same palatability as the −40 ° C. frozen storage product.
Example 3
Volatile coffee scent components and scents were obtained from the coffee extract obtained in the same manner as in Example 1 by steam distillation using a volatile component separator (packed tower type gas-liquid countercurrent contact volatile component separator, Kotobuki Techlex Co., Ltd.). Separated into free coffee ingredients. The volatile scent component was refrigerated, sodium bicarbonate was added to the coffee component not containing the scent component, the pH was adjusted to 6.3, and heat treatment was performed at 138 ° C. for 5 minutes in the same manner as in Example 1. By this treatment, the pH of the coffee component containing no volatile scent component was lowered to 5.7. The volatile scent component was returned to the coffee component and diluted with water to a Brix concentration of 1.55%. After sterilization at 133.8 ° C. for 39.4 seconds using a UHT sterilizer, hot pack filling was performed at about 85 ° C. on a 500 ml PET bottle.

  Table 6 shows changes in pH and acidity when the sample of Example 3 was stored at 40 ° C.

  The liquid coffee of Example 3 had very little pH change like that of Example 2, and was able to suppress an increase in sourness. Since a volatile scent component was added later, a product maintaining the original scent of coffee could be produced.

Claims (11)

The liquid coffee is heated at a temperature of 0.99 ° C. 120 ° C. or higher, by adding an alkali to the liquid coffee that is heat treatment, includes neutralizing the acid component generated by the heat treatment, the stabilized liquid How to make coffee. The method according to claim 1 , further comprising adding a coffee scent component to the heat-treated liquid coffee after the heat treatment. The method according to claim 1 or 2 , wherein the heat treatment is performed within one hour. The method according to any one of claims 1 to 3 , wherein the liquid coffee is sugar-free or sweetened black coffee containing no milk. The temperature of the heat treatment is at 135 ° C. or higher 145 ° C. or less, The method according to any one of claims 1 to 4, within 10 minutes or 1 minute processing time. Liquid coffee manufactured by the method according to any one of claims 1 to 5 , wherein the pH at the initial storage is 5.2 to 6.8. The liquid coffee according to claim 6 , wherein the pH drop after storage at room temperature for 1.5 months is 0.3 or less. Rise value of titratable acidity to the end point pH6.1 after storage 1.5 months room temperature, 0.9 is [ml-0.1 mol NaOH / g- ss Hereinafter, according to claim 6 or 7 Liquid coffee. The liquid coffee of any one of Claims 6-8 whose increase rate of the content quinic acid after preserve | saving for 6 months at room temperature is 7% or less compared with this storage start. The increase rate of quinic acid contained after the liquid coffee produced by the method according to any one of claims 1 to 5 and stored at room temperature for 1.5 months at room temperature for 4.5 months is The liquid coffee according to any one of claims 6 to 8 , which is 4% or less as compared with 4.5 months before the start of storage. The liquid coffee product which added the additive selected from the sweetener, the fragrance | flavor, milk, and these mixtures to the liquid coffee of any one of Claims 6-10 .