JPS6291157A - Method of treating raw mushroom - Google Patents

Abstract

PURPOSE:To obtain a mushroom product having improved fragrance and flavor, enriched nutritive component and stable quality, preservable for a long period, by cooling raw mushroom to reduce life metabolism and freezing it rapidly. CONSTITUTION:Fresh raw mushroom is cooled in an environment at <=10 deg.C as soon as possible, to reduce live metabolism of mushroom. Then, mushroom is kept in a frozen state for at least <=2hr, preferably <=1hr so that the temperature of the axial center or the mushroom is cooled to <=-20 deg.C. Then, the temperature of the frozen mushroom is raised in an environment at <=0 deg.C, preferably about -3--5 deg.C in a range not to thaw it and the mushroom is preserved in a frozen state as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for processing mushrooms, particularly for enhancing the aroma and taste of edible mushrooms and increasing the content of free amino acids, resulting in nutritionally improved food products. Regarding the processing method for

Conventional technology Conventionally, mushrooms such as shiitake, matsutake, and even pine mushrooms are usually eaten as soon as possible after being harvested, but when stored raw, the quality deteriorates within 3 to 4 days and the product becomes unusable. Value is lost. With the desire to serve these mushrooms on the table regardless of the growing season, for example, shiitake mushrooms are dried into dried shiitake mushrooms, and pine mushrooms and nameko mushrooms are prepared with pre-cooking such as boiling to produce enzymes. Methods of preservation are used, such as destroying and canning or bottling it, or freezing it.

However, these processed foods lose the original flavor of fresh mushrooms and have a different flavor, so they can be considered to be different foods from so-called raw mushrooms. In particular, the shiitake mushrooms that are processed into dried shiitake mushrooms are of a different variety in shape and thickness from those used raw. Processing improves the aroma and taste, but there is a problem in that the quality of the product is unsatisfactory.

In response to the desire to obtain fresh mushrooms whenever they want without being affected by changes in production volume, the inventor has already invented a method for processing edible fungi and has filed a patent application ( JP-A-60-105452).

However, although the fungi obtained by the processing method of the present invention can maintain a shape, color, and taste comparable to the raw state for a long period of time, they have the disadvantage that the quality is not necessarily constant.

In other words, if we take shiitake mushrooms as an example, even if the same processing is performed, there will be differences not only depending on the variety of the mushroom, but also due to factors such as the temperature and weather at the time of collection, and even the holding time between collection and processing. There was a problem in that the product value decreased due to variations in quality.

Problems to be Solved The present inventor proposed the invention previously proposed, that is, edible fungi in a live state are cooled and frozen in an atmosphere of -30°C or less for 2 hours or more, and then the frozen edible fungi are We conducted further research on a processing method that involves leaving the mushrooms undisturbed for at least several days in an atmosphere below ℃, and attempted to provide a method that can consistently obtain mushroom foods of excellent quality without variation.

Means for Solving the Problems The object of the present invention as described above is to first heat fresh mushrooms at 10°C.
Cool the mushroom in the following environment to lower its daily metabolism, then transfer it to a frozen environment and rapidly cool it until the core temperature of the mushroom reaches 120°C or less, and then keep it in an environment below 0'C without thawing. This is achieved by raising the temperature at a temperature of 100 mL, and then holding the temperature for the required period of time without thawing.

The first step in the method of the invention is to collect 10 ml of fresh, raw mushrooms.
The method is to reduce the metabolic rate of mushrooms by cooling them in an environment below °C. Mushrooms that have just been harvested still have a vigorous metabolism and continue to grow, and their respiration is also active. If the mushrooms are packed in bags or piled up as they are, the temperature of the mushrooms will rise and their metabolic rate will become even more pronounced.However, cooling the freshly collected mushrooms by exposing them to cold air below 10 degrees Celsius as soon as possible will slow down their metabolic rate. quality variation.

At this time, it is preferable to transport the mushrooms to a refrigerator or the like immediately after collecting them.

In the next step, the pre-chilled raw mushrooms are rapidly frozen and cooled so that the core temperature of the mushrooms is below -20°C.

Such rapid cooling means that cooling is completed within at least 2 hours, preferably within 1 hour, and more preferably within 30 minutes. For rapid cooling in this way, for example, liquid nitrogen may be used to cool the mushrooms, but it is also possible to transport pre-chilled raw mushrooms into a -30°C freezer, or even place them in a -50°C freezer. Even better if you use it. Of course, if there is sufficient ventilation space between the mushrooms, a freezing room with milder temperature conditions than when the mushrooms are piled up can be used. The temperature of the freezing room and the time required for freezing are as follows: The temperature at the center of the mushroom shaft is 120°C.
It is necessary to make appropriate selections and decisions, taking into consideration the accumulation conditions and packaging conditions during the freezing treatment of pre-cooled raw mushrooms, within a range that achieves this.

The mushrooms frozen in the second stage are heated while frozen in the next third stage. In other words, mushrooms that have been frozen to a core temperature of 120°C or below should be kept at 0°C or below, preferably -3 to -3°C.
It is transferred to a freezing room at about -5°C, and the temperature is gradually raised. There is no particular limit to the rate of temperature increase, but in general, when mushrooms are packaged and piled up, it is desirable to store them in a freezer at about -3°C for one day or more. However, if sufficient air permeability is ensured, it is not necessary to store it for such a long time. In order to ensure uniform quality of the mushrooms, it is desirable that the mushrooms be stored in a frozen state in such a freezing chamber until they reach the consumer. Even if the mushrooms are stored under such conditions for a considerable period of time, for example over a year, the quality of the mushrooms will not deteriorate.

Frozen mushrooms treated according to the present invention can be thawed in a refrigerator or a microwave oven like well-known frozen foods, but they may also be simply left indoors to thaw naturally. In addition, they may be cooked immediately after being frozen, and all of them maintain excellent quality as food.

The treatment method of the present invention requires the above-mentioned three stages to be carried out in sequence. If the first pre-cooling step is omitted, the resulting frozen mushrooms may partially turn black or undergo partial deterioration; however, such deterioration does not occur in mushrooms frozen after pre-cooling. After cooking, all mushrooms have the same color and texture as cooked raw mushrooms. That is, according to the improved freezing processing method of the present invention, the degree of improvement in aroma and taste and enhancement of nutritional components such as amino acids achieved by conventional freezing processing methods is more reliable, and the occurrence of defective products such as deterioration is prevented. This has the effect of significantly reducing the amount of mushrooms produced, and allows for economical production of homogeneous processed mushrooms with high commercial value at a high yield.

Example 1 Shiitake mushrooms with a cap diameter of about 4 to 5 cm, which are generally available on the market as fresh shiitake mushrooms, were collected and placed in a basket.
It was loaded into a refrigerator at 5 to 8°C within 0 minutes, and transported to a frozen warehouse at -30°C after about 3 hours. The temperature at the center of the root axis of the mushroom cap reached 120°C in about 1 hour and 20 minutes after being brought into the warehouse, so the temperature was reduced to 15°C after 1 hour and 30 minutes.
The mixture was transferred to a freezer in storage at 10°C, and after one day and night had passed, it was taken out and left indoors to thaw naturally.

The thawed mushrooms had a good aroma, the color tone was the same as fresh shiitake mushrooms, and there was no discoloration at all, and the elasticity and texture after cooking were the same as when fresh shiitake mushrooms were used.

Comparative Example 1 After collecting, it was deposited in a basket, and about 4 hours later, 13
Regarding the shiitake mushrooms that were delivered to a frozen warehouse at 0°C, the temperature at the root axis of the mushroom cap reached 120°C after about 2 hours, so the process was carried out in the same manner as in Example 1. .

The thawed mushrooms had a good aroma, but some discoloration had occurred and the commercial value was poor.

Example 2 Shiitake mushrooms were collected in the same manner as in Example 1 and then loaded into a refrigerator.
After about 4 hours, the mushrooms were transferred to a -55°C freezer and kept for 40 minutes to freeze, and the core temperature of the mushrooms reached -25°C. After that, it was processed and thawed in the same manner as in Example 1.
Mushrooms of almost the same quality as the thawed mushrooms obtained in Example 1 were obtained.

Comparative Example 2 Shiitake mushrooms were frozen in a freezer at -55°C in almost the same manner as in Example 2. Thirty minutes after the start of freezing, the core temperature of the mushrooms reached -18°C, so they were immediately transferred to a freezer for storage at -15°C, and thereafter treated in the same manner as in Example 2 to obtain thawed mushrooms.

The thawed mushrooms had a good aroma and had a similar appearance to the mushrooms of Example 2, but tasting after cooking revealed that they were partially softened and did not have a good texture.

Comparative Example 3 Shiitake mushrooms were collected in the same manner as in Example 1 and then loaded into a refrigerator.
After preserving for 3 hours, transfer to a frozen warehouse at -30°C for 1 hour.
The core temperature of the mushrooms was lowered to -22°C by freezing them in portions. Thereafter, it was immediately left indoors to thaw naturally.

The thawed mushrooms obtained in this way did not have much fragrance, and although their appearance was the same as the thawed mushrooms of Example 1 immediately after thawing, they began to partially turn black 30 minutes after thawing. The frozen shiitake mushrooms of Example 1, raw unprocessed shiitake mushrooms, and dried shiitake mushrooms obtained by drying similar shiitake mushrooms were tested. The samples were left indoors or allowed to absorb water at room temperature for 2 hours, then boiled in water for 30 minutes, and then analyzed for aroma and taste components.

The aroma components were extracted from the mushroom part and the extract part using hexane, water was removed using anhydrous sodium sulfate, and then the aroma components were detected using a gas chromatograph. As a result, it was found that when the amount of aroma components in fresh shiitake mushrooms is 1, the amount of aroma components in dried shiitake mushrooms is 2, and in frozen shiitake mushrooms it is 5.

In addition, the flavor components were extracted from the mushroom part and the extract part using ethanol, and once dried, they were dissolved in citric acid buffer and 5' extracted using liquid chromatography.
- Separation and detection of nucleotides. The results were 88 mg/100 g of fresh shiitake mushrooms and 245 mg/100 g of dried shiitake mushrooms.
100 g, whereas frozen shiitake mushrooms according to the invention were found to contain 336 mg/100 g.

Furthermore, the content of free amino acids was measured using an amino acid analysis needle, and the results are shown in Table 1. All values are in mg per 100g of solid content of shiitake mushrooms.

Looking at this, it can be seen that free amino acids, especially essential amino acids, are clearly increasing.

Table 1 Effects of the Invention The mushroom food obtained by the processing method of the present invention before freezing has improved aroma and taste, enhanced nutritional components, can be stored for a long period of time, and has a texture similar to fresh mushrooms at any time. The method of the present invention has all the advantages of the prior invention in that mushrooms can be obtained, but in addition, the method of the present invention eliminates the drawback of unstable quality and can obtain processed mushrooms with high commercial value at a good yield. It has its features.

Claims (1)

[Claims] Fresh raw mushrooms are cooled in an environment below 10°C to lower their metabolic rate, and then transferred to a frozen environment to reduce the core temperature of the mushrooms to -
A method for processing raw mushrooms, which comprises rapidly cooling the mushrooms until they reach 20°C or lower, then increasing the temperature in an environment of 0°C or lower without thawing, and then holding the temperature for a required period of time.