JP2002000215A - Method for treating citrus fruit, and citrus fruit having flavor improved by the treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating a citrus fruit, which can safely and sanitarily improve the flavor of the citrus fruit without ethylene or a spraying agent and without giving an unnecessary anxiety to consumers, and to provide the citrus fruit to which the treating method has been applied. SOLUTION: This method for treating the citrus fruit, characterized by thermally treating the citrus fruit in a temperature range of 35 to 60 deg.C to reduce sour ingredients, thereby improving the flavor of the fruit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for treating citrus fruits and a citrus fruit whose flavor is improved by the treatment method.

[0002]

2. Description of the Related Art Citrus fruits are often used as desserts or as fruit juice drinks, and have a unique acidity. The balance between this unique acidity and sweetness is a great taste food. It has become attractive. However, on the other hand, many consumers generally dislike the acidity peculiar to the citrus fruit, and this point is a bottleneck in expanding consumption of the citrus fruit.

[0003] In citrus fruits, the acid concentration of the juice is a major factor that affects the taste together with the sugar concentration. Among the acid concentrations in the juice, the free acid concentration is closely related to the acidity. There are many investigations on the free acid concentration, which vary depending on cultivation conditions and the like, but it is known that the difference between types and varieties is remarkable. Here, the free acid concentration is the difference between the total acid concentration and the concentration of a bound acid bound to a cation such as potassium or calcium. On the other hand, in order to capture the acid concentration in fruit juice not only from the viewpoint of taste problems, but also from a physiological viewpoint, the acid concentration of the juice is reduced to three concentrations: total acid concentration, free acid concentration, and bound acid concentration. It is necessary to divide and view them (Journal of the Horticultural Society, Vol. 56, No. 3, pp. 263 to 267, 1987). From such a viewpoint, the balance of the taste of citrus fruits and the content of free acids have been attracting attention as indicators of the taste of citrus fruits.

[0004] Conventionally, in order to improve the flavor of the fruit, a technique of treating the fruit with ethylene gas having a ripening accelerating action has been attempted (hereinafter referred to as prior art 1). When the ripening of citrus fruits is promoted by such a method, various changes such as an increase in the concentration of juice and an increase in the sugar content occur inside the fruits, and the flavors match the tastes of general consumers. -It is expected to have a texture (Kuniyasu Ogata, "Processing and Utilization of Horticultural Foods", pp. 118-127, Yokendo Co., Ltd., August 1, 1976).

As a technique relating to ripening of citrus fruits, there is disclosed a technique for increasing the sugar content of citrus fruits by microwave irradiation (Japanese Patent Application Laid-Open No. 6-343442) (hereinafter referred to as prior art 2).

Japanese Patent Application Laid-Open No. 10-248385 discloses a technique for relatively improving the sweetness of fruits by spraying an agent for reducing organic acids, which are sour components of citrus fruits, onto fruits and leaves of fruit trees. Disclosed (hereinafter referred to as prior art 3
Described as ").

[0007]

In the prior art 1 described above,
Since gaseous ethylene is difficult to store and treat, it is poor in practical use. Therefore, there has been a tendency to frequently use a spraying agent such as chloroethylphosphonic acid, which is derived from ethylene. Also,
Since the pulp is wrapped in the pericarp and the pericarp is thick, the spraying agent does not sufficiently penetrate, and when the pulp is aged until the sugar content increases, the pericarp becomes soft and its commercial value decreases. I will. Furthermore, the use of such a chemical spraying agent for fruits is feared to affect the human body and the environment, and is a factor that gives a bad impression to general consumers in modern society.

[0008] Further, in the prior art 2, it is necessary to once treat the citrus fruits at a low temperature, a large-scale microwave generator is required, and it is considered that the citrus fruits are not versatile in terms of equipment and cost.

In the above-mentioned prior art 3, it is necessary to spray an organic acid deoxidizer, and as in the above-mentioned prior art 1, there is a concern about the influence on the human body and the environment. In addition, it is considered that reducing the total acid concentration in citrus fruits by adding an organic acid deacidifier improves the flavor by using a chemical, and may impair the original flavor of citrus fruits.

[0010] Therefore, even if there is no problem with the quality of the actual citrus fruits, the fruits treated by the above-mentioned prior arts 1 to 3 have to be disadvantageous in terms of developing a market as a product. In addition, such a problem was the same also in the fruit juice which squeezed the citrus fruit. For these reasons, there has been a strong demand for a simple and excellent treatment method for improving the flavor of citrus fruits without any problem in safety.

The present invention does not use ethylene or a spraying agent,
An object of the present invention is to provide a treatment method for improving the flavor of citrus fruits which is safe and sanitary without causing unnecessary anxiety to consumers, and which can be easily carried out.

Another object of the present invention is to provide a citrus fruit whose flavor is improved by such a method.

[0013]

Means for Solving the Problems A first invention of the present invention for solving the above-mentioned problems is to prepare a citrus fruit at 35 ° C. or higher.
This is a method for treating citrus fruits, which comprises performing heat treatment in a temperature range of 0 ° C. or lower to reduce the free acid concentration in fruits and improve flavor.

A second aspect of the present invention for solving the above-mentioned problems is a citrus fruit having an improved flavor according to the first aspect.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first invention of the present invention is a treatment method for improving the flavor of citrus fruits. In the method of the present invention,
First, the citrus fruit is heat-treated in a temperature range of 35 ° C or more and 60 ° C or less. As a mode of the heat treatment, any mode such as a mode of immersion in hot water, a mode of heating by a shower, a mode of heating by warm air or steam, and the like may be used. put in,
This basket can be immersed in stored hot water. In this case, the hot water is preferably maintained at a constant temperature, and in particular, it is recommended that the hot water be stored in a thermostat and maintained at a constant temperature. In addition, such a heating operation is desirably performed continuously industrially.For example, citrus fruits are placed on a mesh-shaped conveyor, and the mesh-shaped conveyor is set in advance in a form where the mesh-shaped conveyor is heated. By doing so, it is possible to continuously process citrus fruits. In this case,
The temperature and heating time of the hot water can be appropriately set according to the variety, weight, ripeness and free acid concentration of the citrus fruit before the treatment. In addition, when heating the citrus fruit, the citrus fruit may be appropriately divided and then treated, but a whole state is preferable.

In the method of the present invention, it is desirable that the time of the heat treatment is 10 minutes or less. In this case, the heating time can be set as appropriate, but is most preferably 10 minutes or less, and it is easily adapted to practice on an industrial scale. In particular, when the heat treatment is performed for 10 minutes or more, discoloration of the outside of the citrus fruit becomes remarkable, which is not preferable. Further, after the heat treatment, drying and waxing may be performed in a usual manner.

In citrus fruits, the acid concentration in the juice is a major factor that affects the taste as well as the sugar concentration, and the free acid has a deep relationship with the acid concentration. In the present invention, as shown in the test examples described below, by reducing the free acid concentration by heating, the sweetness of the fruit is relatively increased and the flavor is improved. Incidentally, the free acid in the present invention, among all acids,
It represents an acid other than a binding acid bound to a cation such as potassium or calcium. It is desirable that the free acid concentration be relatively reduced by changing the component ratio of the free acid and the bound acid without reducing the total acid concentration. In addition, the organic acid described in the prior art 3 refers to the total acid of the present invention, and the technology of the present invention is different from the prior art 3.

Further, it is desirable that the heat treatment of the citrus fruits does not cause a change in the vitamin C concentration in the fruits before and after heating.

A second aspect of the present invention is a citrus fruit having an improved flavor according to the first aspect. The citrus fruit whose flavor has been improved by the first invention has a relatively strong sweetness, matches the taste of the consumer, and can be prepared as an ideal fruit. Such citrus fruits include Unshu mandarin orange, summer tangerine, Iyo citrus, kumquat, ponkan, sudachi,
Orange, grapefruit, sweetie, lemon and the like can be exemplified. Incidentally, the first invention described above,
Although the present invention relates to citrus fruits, such a technique of the first invention can be applied to juice obtained by squeezing citrus fruits.

Next, the present invention will be described in detail with reference to test examples.

Test Example 1 This test was conducted to confirm the change in the acidity of citrus fruits due to the heat treatment.

(1) Preparation of sample Five commercially available summer tangerines are divided into two, and each is cut in half. One of the cut half is immersed in hot water at 55 ° C. and 52 ° C. (stored in a thermostat). After 5 minutes, the sample was taken out of the hot water to obtain Samples 1 and 2, respectively. Samples 1 and 2
The other half cut corresponding to the above, that is, the half cut not immersed in the hot water was designated as control samples 1 and 2, respectively. In addition, commercially available lemon 5
Each of the pieces was cut into two halves, and one of the cut halves was immersed in hot water at 50 ° C. and 48 ° C. (stored in a constant temperature bath), pulled up from the hot water three minutes later, and samples 3 and 4, respectively. And The other half cut corresponding to Samples 3 and 4, that is, the half cut not immersed in hot water was designated as Control Samples 3 and 4, respectively.

(2) Test method Each of the sample and the control sample was squeezed, and the concentrations of free acid, total acid, and bound acid were measured, and all were converted to citric acid and expressed. At the same time, the vitamin C concentration in the fruit was also measured. The measured value of each sample was an average value of five halves. In addition, each concentration (% by weight) of the free acid, the total acid, and the bound acid was measured by the following method. First, [Journal of Horticultural Society, Vol. 35, No. 1, pp. 36-42, 1
966], a heat-treated citrus fruit sample and a control sample were crushed with a homogenizer, filtered through a Buchner funnel, the residue was washed several times with demineralized water, and the filtrates were combined for analysis. . Further, a part of the filtrate is subjected to a titration method for determining the acid content (supervised by the Japan Juice Association, “Latest Juice and Fruit Beverage Encyclopedia”, pp. 568-569, Asakura Shoten, 1997) (hereinafter referred to as titration method 1). Will be described.)
Using phenolphthalein as an indicator according to the above, the addition amount (ml) of the 0.1 N sodium hydroxide solution until color change from colorless to red was measured. 0.0064
g, and the free acid content (%) in the sample was determined as the amount of citric acid per 100 g of the sample. The total acid content was determined by using a 50 to 100 mesh cation exchange resin (Dowex Co., Ltd., Dowex50W-X1) for the above filtrate.
2) The value passed through the column was determined by the same method as in the titration method 1. The bound acid content was calculated by determining the difference in free acid content from the total acid content. Vitamin C concentration in fruit can be measured with ascorbic acid test kit (Merck)
It measured using.

(3) Test Results The results of this test are as shown in Table 1. Table 1
It is a table | surface which shows the change of the sourness of summer tangerine and lemon by immersing in hot water. As is evident from Table 1, when the untreated control sample 1 in summer tangerine was compared with the sample 1 heated at 55 ° C. for 5 minutes, the free acid concentration was reduced from 0.96% to 0.77%. The binding acid concentration is 0.32%
From 0.57% to 0.57%. However, the vitamin C concentration was 200 mg / L before and after heating, and did not change. Similarly, comparing untreated control sample 2 with sample 2 heat treated at 52 ° C. for 5 minutes, the free acid concentration is 1.22%
From 1.09%. The binding acid concentration is 0.3
It increased from 2% to 0.45%. However, the vitamin C concentration before and after heating was 500 mg / L, and did not change. Also, untreated control samples 3 and 50 in lemon
Comparing Sample 3 which was heat treated at 3 ° C. for 3 minutes, the free acid concentration was reduced from 5.70% to 5.50%. Also, the bound acid concentration increased from 0.64% to 0.84%. However, the vitamin C concentration before and after heating was 500 mg / L.
And did not change. Similarly, untreated control sample 4
When the sample 4 and the sample 4 heat-treated at 48 ° C. for 3 minutes were compared, the free acid concentration was reduced from 7.01% to 6.70%. Also, the bound acid concentration increased from 0.76% to 1.01%. However, the vitamin C concentration was 500 before and after heating.
mg / L and did not change.

From these results, it was found that the heat treatment can change the free acid into a bound acid without changing the vitamin C concentration in the citrus fruit, and can effectively improve the flavor of the citrus fruit. did.

[0026]

[Table 1]

Test Example 2 This test was performed to confirm the change in sugar content of citrus fruits due to heat treatment.

(1) Preparation of Sample Five commercially available summer tangerines are cut in half vertically, and one of them is cut into 55 pieces.
The sample was immersed in hot water at 50 ° C. and 50 ° C. (stored in a constant temperature bath), and after 5 minutes, pulled out of the hot water to obtain Samples 5 and 6. Sample 5
The other half corresponding to Sample 6 and the other half, that is, the half not immersed in the hot water, were taken as Control Samples 5 and 6, respectively. Also, five commercially available lemons are cut in half vertically, and one of them is 55 ° C.
Was immersed in hot water (stored in a constant temperature bath), and after 3 minutes, pulled up from the hot water to obtain Sample 7. A half cut on the opposite side corresponding to sample 7, that is, a half cut not immersed in hot water was used as control sample 7.

(2) Test Method After the heat treatment, the temperature in the pulp of the citrus fruit was 21 to 23.
The solution was left to stand until the temperature reached ℃, and the sample and the control sample were each squeezed, and the sugar content, free acid concentration and vitamin C concentration were measured.
The sugar content was measured using a refractometer (manufactured by Atago Co., Ltd.). The free acid concentration and vitamin C concentration were measured by the same method as in Test Example 1. In addition, similarly to the said test example 1, the measured value calculated the average value of each half cut, and was considered as the measured value of each sample. Sugar content, free acid concentration and vitamin C
In order to observe the change in the concentration, the value obtained by dividing the measured value of the sample by the measured value of the control sample was evaluated as a rate of change (%).

(3) Test Results The results of this test are as shown in Table 2. Table 2
It is a table | surface which shows the change of the sugar content of a citrus-type fruit, a free acid concentration, and a vitamin C concentration by immersing in hot water. As is evident from Table 2, in Sample 5, which was heat-treated at 55 ° C for 5 minutes in summer tangerine, the sugar content and the vitamin C concentration did not change, and the free acid concentration decreased to 92.8% on average. Also,
In Sample 6, which was heated at 50 ° C. for 5 minutes, the sugar content and the vitamin C concentration did not change, and the free acid concentration was 90.1% on average.
Decreased to. Furthermore, in Sample 7, which was heat-treated with lemon at 55 ° C. for 3 minutes, the sugar content and vitamin C concentration did not change, and the free acid concentration decreased to 96.0% on average.

As a result, the sugar content and the vitamin C concentration of the citrus fruits did not change even after the heat treatment, and it was clarified that the flavor of the citrus fruits could be improved by reducing the free acid concentration exclusively in the method of the present invention. Was.

[0032]

[Table 2]

Next, the present invention will be described in more detail with reference to examples, but the scope of the present invention is not limited to the following examples.

[0034]

EXAMPLE 1 50 commercially available summer tangerines were placed in a wire mesh basket, the wire mesh basket was immersed in a constant temperature bath (hot water) at 55 ° C., and heat-treated. To 21 to 23 ° C. to obtain a heat-treated product. A panel of 20 men and women in their 20s and 40s performs a sensory test on the obtained fruit for sweetness, sourness and overall flavor. Good taste (0 points), good taste (1 point) , The flavor was slightly poor (2 points), and the flavor was poor (3 points). From the average of the evaluation points, less than 0.5 points are good, 0.5 or more and less than 1.5 points are slightly good, 1.5 or more and less than 2.5 points are slightly poor, and 2.5 or more points are 3 or more. Less than 0.0 point was judged as defective. Apart from this, summer tangerine which was not heat-treated was regarded as an untreated product, and was compared for determination. The results are as shown in Table 3. In terms of sweetness, sourness, and overall evaluation, the heat-treated product was higher than the untreated product.

[0035]

[Table 3]

[0036]

Industrial Applicability The method for improving the flavor of citrus fruits of the present invention is safe and sanitary, and does not use ethylene or a spraying agent. Since it can be carried out simply and at low cost without giving, it is suitable for industrial use. The citrus fruit of the present invention has a safe and hygienically improved flavor, and has extremely high commercial value.

Claims (2)

[Claims] 1. A citrus fruit is subjected to heat treatment in a temperature range of 35 ° C. or more and 60 ° C. or less to reduce the free acid concentration in the fruit,
A method for treating citrus fruits, characterized by improving flavor. 2. A citrus fruit whose flavor has been improved by the treatment method according to claim 1.