JPH03180139A - Drying of common scallop - Google Patents

Abstract

PURPOSE:To extremely shorten drying time by heating common scallops with high humidity, high temperature hot air, maintaining the high temperature and the high velocity of hot air and mainly drying while gradually reducing humidity. CONSTITUTION:In drying of common scallops by storing common scallops 3 in a dryer 1 and circulating hot air 4 through the dryer 1, the following constitution is adopted. Namely, the hot air 4 is humidified 8 to 65-75% relative humidity, heated 7 to 60-80 deg.C, to heat the common scallops 8. Then the common scallops are mainly dried while keeping the temperature of the hot air 4 constant, regulating the velocity of the hot air 4 0.6-1.1m/s and gradually reducing the relative humidity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the drying of scallops, and particularly to a method for drying scallops that is suitable for shortening the drying time without pretreatment such as boiling in hot water.

[Conventional technology]

Generally, scallops contain 70 to 75% moisture, and in order to make dried scallops that can retain this moisture, drying is required to reduce the moisture content to 5 to 20%.

A common method for artificially drying scallops is hot air drying, and the drying time in this drying method is shortened by increasing the hot air temperature and hot air speed (hot air volume).

However, the drying heat source is hot air that has been heated by a heater, etc., so if such hot air is used at an early stage of drying, the temperature difference between this hot air and the surface of the scallops will become large. As a result, evaporation (transpiration) of water from the surface becomes active.

On the other hand, the temperature of the hot air cannot be made too high because the movement (diffusion) of moisture from the inside of the scallop to the surface cannot follow this movement.

If you rush the drying process and make the hot air temperature higher than necessary,
Colloidal substances, sugars, acids, free amino acids, inorganic salts, etc. contained in scallops stick to the surface layer, causing a so-called surface hardening phenomenon.

This surface hardening of the scallop prevents internal moisture from evaporating to the outside, further delaying subsequent drying.

Therefore, the reality is that drying requires several days of repeated electrical steaming at a low drying hot air temperature of 30 to 45°C.

As a method for producing dried foods aimed at shortening the drying time, for example, Japanese Patent Application Laid-Open No. 1114-1983
It is possible to raise the number of publications.

However, even with this drying method, after pretreatment by steaming, boiling, etc., the advantages of high-frequency dielectric heating and hot air heating are utilized to maintain the uniform temperature of the food to be dried below a certain temperature through a complicated process. This is a manufacturing method in which the water content is lowered to 10 to 30% or less by intermittent and repeated drying, and the drying temperature must be set low to prevent surface hardening due to the above-mentioned reasons.

According to the disclosed example, even this method requires several rounds of electrovaporation.

[Problem to be solved by the invention]

In conventional methods of drying scallops, increasing the temperature of the hot air causes surface hardening of the scallops and delays subsequent drying, so the temperature of the hot air is set low and drying takes a long time. The purpose of the present invention is to provide a method for drying scallops that can significantly shorten the drying time by using a closed circuit drying method that controls and circulates hot air at high temperature and high humidity. be.

[Means to solve the problem]

In order to achieve the above object, the method for drying scallops according to the present invention is a method for drying scallops in which raw scallops are placed in a dryer without any pretreatment such as boiling, and hot air is passed through the dryer. At the same time, the relative humidity of hot air was humidified to 65 to 75%, and the temperature was heated to 60 to 80°C, and the scallops were heated to 30%.
After heating for 1 minute to 1 hour, the temperature of the hot air is kept constant and the speed of the hot air is controlled within a range of 0.6 to 1.1 m/s to gradually lower the relative humidity for main drying. ing.

[Effect]

According to the method for drying scallops of the present invention, after heating with high humidity and high temperature hot air, the high temperature and wind speed of the hot air are maintained,
By performing main drying while gradually lowering the humidity, the surface of the scallop is humidified and heated to a high temperature, which balances the rate of moisture diffusion from the inside of the scallop to the surface and the evaporation of water from the surface, resulting in surface hardening. It never happens.

Next, by keeping the high temperature and wind speed of the hot air almost constant and gradually lowering the relative humidity, one electric steaming process smoothly promotes a reduction in the moisture content of the scallops, and there is no outflow of nutrients and the shrinkage rate is also reduced. few.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 to 3.

As shown in FIG. 1, scallops 3 are housed in a batch type ventilation dryer l and placed on a tray 2, and hot air heated by a hot air generator 7 using high temperature exhaust gas 9 etc. is blown into the dryer 1. In a method of drying scallops that is passed through a pipe 4, the relative humidity of the hot air is humidified to 65-75% with steam from a steam generator (humidifier) 8, and the temperature is adjusted using a heat exchanger 7.
After heating the scallops 3 to 60 to 80°C, the temperature of the hot air is kept constant at 60 to 80°C, and the speed (air volume) of the hot air is controlled within the range of 0.6 to 1.1 m/s. The structure is such that the relative humidity is gradually lowered and the main drying process is carried out.

Note that the blower pipe 4 opens above the tray 2, and the return pipe 5 is connected below the tray 2. And each tube 4,
5 is connected to a circulation fan 6, and drying air 16 is taken in through a damper 11. The humidity of the hot air is regulated by controlling the control valve 15 by the output signal of the sensor that detects the humidity inside the blast pipe 4, and steam flows in from the steam generator 8, and the temperature of the hot air is adjusted by detecting the temperature inside the blast pipe 4. The control valve 14 is controlled by the output signal of the sensor, and the amount of high temperature exhaust gas 17 is changed and regulated. A three-way valve 12, 13 and an exhaust pipe 10 are attached to the piping system.

Next, the operation of this embodiment will be explained.

The tray 2 containing the scallops 3 to be dried is placed in the dryer 1, and the air taken in by the circulation fan 6, the exhaust hot air sucked from the return pipe 5, and the humidifier 8 are sent to the return pipe 5. The supplied steam is sent to the heat exchanger 7 through the blast pipe 4 to make it high temperature, and the high temperature hot air obtained here is sent to the dryer 1 through the blast pipe 4, and the scallops are heated by this hot air. . Next, the control valve 15 of the humidifier 8 is controlled by the dehumidification program and slightly opened while sending high-temperature humidified hot air into the dryer V&1, and the scallops are dried by this hot air. In addition, during the above operation, a part of the exhaust heat air is exhausted from the exhaust pipe ↓O.
do. Raw scallops can be cooked without pre-treatment such as steaming or boiling.
After heating for 30 minutes to 1 hour in hot air at 60 to 80 °C humidified to a relative humidity of 65 to 75%, the scallops were heated in a hot air velocity range of 0.6 to 1 m/s while keeping the temperature constant. The humidity of the hot air is gradually reduced at a rate that balances the rate of moisture diffusion from the inside to the surface and the rate of moisture evaporation from the surface, and the moisture content is smoothly reduced with one electric vaporization while preventing surface hardening. This reduces the amount of carbon dioxide to 15-20%.

Relative humidity is related to hot air temperature and wind speed, which will be described later, but as a first step, fish and shellfish are dried all at once to a moisture content of 40% or less, which allows them to be stored for a long time without breeding spoilage bacteria. For 1 minute to 1 hour, raise the temperature of the scallops sufficiently in a humidified atmosphere of 65 to 75%. (It may be thawed from the frozen state and heated.) If the initial relative humidity of the hot air is 65% or less, the movement of internal moisture due to contraction of the scallops will be slow, and the degree of water loss relative to the drying time will be reduced. descend.

On the other hand, if it exceeds 75%, water droplets will form on the surface and the water loss at the initial stage of main drying will become slow, so it is set at 65 to 75%.

Furthermore, if the dehumidification program rate is 5%/hour or more, surface hardening of the scallops will occur and drying will not proceed smoothly, while if the dehumidification program rate is 2.5%/hour or less, the drying time will be prolonged and moisture will be absorbed. The rate is set at 2.5 to 5%/hour because the transpiration of the water becomes slow and the product becomes uneven. As shown in FIG. 2, which shows the drying temperature T and time characteristics, the higher the temperature T, the shorter the drying time H, but if the hot air temperature is less than 70°C,
It takes a long time to dry, and if the temperature exceeds 80°C, it becomes very difficult to control the relative humidity and surface cracks are likely to occur, so the temperature is set in the range of 70 to 80'C.

On the other hand, as for the hot air speed, as the wind speed V increases, the drying time T will be shortened, but if it is below 0.6 m/s, the variation in the wind speed V in the drying chamber will be large and the product will be likely to be uneven, and conversely, the drying time T will be shorter as the wind speed V increases. If the speed is higher than /s, surface hardening phenomenon is likely to be induced, so the speed is set in the range of 0.6 to 1.1 m/s.

There is a close relationship between relative humidity and hot air temperature T, and by using humidified hot air, the surface of the scallop can be kept appropriately moist, which makes it possible to use high-temperature hot air. , it can also significantly raise the temperature of the body.

Hereinafter, specific examples will be given and explained.

Using a dryer, scallops 3 with a pre-drying temperature of 75% were arranged on a tray 2, and the tray 2 was placed in the dryer 1 and treated under the conditions shown in FIG. That is, relative humidity 870
%, heated at a drying temperature T of 80°C for 1 hour, and then, while maintaining a drying temperature of T80°C and a wind speed of 1.1 m/s, the relative humidity of the hot air was dehumidified from 70% to 40% over 5 hours. After that, the scallops were sufficiently electrically steamed, and the relative humidity of the hot air was dehumidified from 35% to 15% over 4 hours while maintaining the drying temperature of 80'C1 and the wind speed of 1.1 m/s. Drying was carried out until the temperature difference from the actual temperature was within 5°C.

The total time required for drying was 11 hours.

FIG. 4 shows the results of measuring how the temperature (physical temperature) TA of the scallop under the above conditions actually changes over time H.

From the results of the above examples, 1. In the case of the present invention, the temperature of the scallop is significantly increased by high-humidity, high-temperature hot air prior to main drying, and the movement of internal moisture is significantly activated.
The surface is also humidified and becomes hot, causing active water evaporation from the surface.Moreover, this water evaporation and internal water diffusion are balanced, and the surface is dried without hardening. Gradual dehumidification allowed the scallops to maintain a high temperature even during high-temperature drying, and to suppress transpiration on the surface, allowing the scallops to dry rapidly without surface hardening caused by high-temperature hot air. The total drying time was substantially shortened to approximately 11 hours without any pretreatment such as boiling in hot water.

Furthermore, the measurement results of the moisture content G with respect to the drying time T based on the above example are shown in FIG.

As a result, the product of the present invention showed a rapid water reduction curve and was dried to a predetermined moisture content (15% to 17% dry moisture) in an extremely short period of time.

Note that the water reduction curve is illustrated for each combination of drying temperature T and drying air speed (air volume) ■. The right side of the figure shows the condition of the dried material for each moisture content G. During the period from freezing to thawing, there is no outflow of nutrients during the pretreatment stage and high temperature drying is used, so quality deterioration due to putrefying bacteria occurs. It can be prevented. In drying 1, the material is dried all at once to a moisture content of about 40%, which prevents the growth of spoilage bacteria. Electrical steaming avoids surface hardening due to rapid drying and aims to equalize moisture content through electric steaming.

In drying 2, the scallops with uniform water density by electric steaming are
Dry at once to 2-15%.

〔Effect of the invention〕

According to the method for drying scallops of the present invention, since the scallops are heated with high temperature and high-temperature hot air and then dried with high-temperature hot air, the surface hardening phenomenon does not occur and the diffusion of internal moisture is significantly activated. The drying time can be drastically reduced.

Furthermore, since the drying time is short, energy consumption is significantly reduced, and uniform shrinkage has the effect of producing high-quality, candy-colored scallops with high commercial value with little deformation.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a graph showing the influence of drying temperature and wind speed in the present invention, and FIG. 3 is a graph showing changes in hot air temperature and relative humidity in the present invention. , FIG. 4 is a graph showing the average temperature of scallops according to the present invention. 1...Dryer, 3...Scallops, 4...Blower pipe (hot air).

Claims (1)

[Claims] 1. In a method of drying scallops in which scallops are placed in a dryer and hot air is passed through the dryer, the relative humidity of the hot air is humidified to 65 to 75%, and the temperature is adjusted to 60 to 80°C.
After warming the scallops, the temperature of the hot air is kept constant and the speed of the hot air is controlled within a range of 0.6 to 1.1 m/s to gradually lower the relative humidity and perform main drying. A method for drying scallops characterized by: