CN111436484A - Method for drying okra - Google Patents
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- CN111436484A CN111436484A CN202010255585.7A CN202010255585A CN111436484A CN 111436484 A CN111436484 A CN 111436484A CN 202010255585 A CN202010255585 A CN 202010255585A CN 111436484 A CN111436484 A CN 111436484A
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Classifications
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- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
- A23B7/00—Preservation or chemical ripening of fruit or vegetables
- A23B7/02—Dehydrating; Subsequent reconstitution
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
- A23B7/00—Preservation or chemical ripening of fruit or vegetables
- A23B7/02—Dehydrating; Subsequent reconstitution
- A23B7/0205—Dehydrating; Subsequent reconstitution by contact of the material with fluids, e.g. drying gas or extracting liquids
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- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23V—INDEXING SCHEME RELATING TO FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES AND LACTIC OR PROPIONIC ACID BACTERIA USED IN FOODSTUFFS OR FOOD PREPARATION
- A23V2002/00—Food compositions, function of food ingredients or processes for food or foodstuffs
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
- Y02A40/90—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in food processing or handling, e.g. food conservation
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- General Chemical & Material Sciences (AREA)
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- Polymers & Plastics (AREA)
- Preparation Of Fruits And Vegetables (AREA)
Abstract
The invention relates to the technical field of okra drying, and provides a method for drying okra aiming at the problems of severe crust formation, increased hardness and poor rehydration effect of okra caused by hot air drying, wherein tender okra fruits are selected, cleaned, drained of surface moisture, subjected to low-pressure pre-dehydration, hot air drying and sealed storage, wherein the low-pressure pre-dehydration and the hot air drying are alternately carried out, the pressure of a low-pressure environment is gradually reduced, the temperature of the hot air drying is gradually increased, the low-pressure is 100-700 Pa, and the final temperature after pre-dehydration is 4-10 ℃; the air speed of hot air drying is 1.0-1.5 m/s, and the temperature of hot air is 45-55 ℃. Compared with the prior art, the method for drying the okra adopts low-pressure pre-dehydration to generate air holes on the surface of the okra, provides a water vapor escape path for drying and dehydrating the okra, weakens salt migration caused by dehydration of the okra and hardening of the okra caused by the salt migration, and improves the rehydration performance of the okra.
Description
Technical Field
The invention relates to the technical field of okra drying, and particularly relates to a method for drying okra.
Background
Okra is commonly called sheep's horn bean, okra and the like, is originally produced in Africa, is planted in Zhejiang, Shanghai, Guangdong and the like, contains nutrient substances such as protein, pectin, polysaccharide, carbohydrate, vitamin, dietary fiber and the like, and is a nutritional health-care vegetable. The existing research shows that the okra contains natural hormone-like substances, and the extract of the okra has the biological activities of clearing free radicals, resisting fatigue and the like. However, fresh okra is thin in skin and high in water content, so that the okra is easy to lose water and deteriorate after being picked, the okra can be stored for 2-3 days at normal temperature, if the okra is not eaten in time, waste is caused, and the storage time of the okra can be effectively prolonged by drying and dehydrating the okra.
The drying method of the okra mainly comprises vacuum freeze drying, hot air drying and the like, wherein the moisture contained in the okra is directly sublimated and removed from a solid state by the vacuum freeze drying, so that the migration of substances in the okra is avoided, the dehydration uniformity is higher, the quality of the obtained okra is better, and the rehydration ratio is better. In contrast, hot air drying causes water migration from inside to outside due to water evaporation from the surface, which increases the surface hardness of okra after drying, and causes poor rehydration, and high temperature causes high activity of pectinase and the like, which causes pectin decomposition. But compared with the vacuum freeze drying which is still in the research stage at present and has large energy consumption, the hot air drying is more suitable for the large-scale production and application of the okra. Therefore, how to improve the quality reduction of the okra caused by hot air drying has positive significance for realizing the hot air drying application of the okra.
Chinese patent 201610283643.0, the patent name is a method for improving retention rate of antioxidant components in an okra microwave vacuum-dried product by low-frequency ultrasonic wave hot blanching, and discloses a method for vacuum microwave drying okra, wherein the quality of the dried okra can be improved by vacuum microwave drying compared with hot air drying, but the vacuum microwave drying is only suitable for small-scale treatment of okra, and the industrial and large-scale development is still difficult.
Disclosure of Invention
Aiming at the problems of serious surface crusting, increased hardness and poor rehydration effect of the okra caused by hot air drying, the invention aims to provide a method for drying the okra, improve the quality of the okra after hot air drying, improve the rehydration effect of the dried okra and provide a path for realizing large-scale hot air drying of the okra.
The invention provides the following technical scheme:
a method for drying okra, comprising the steps of:
(1) selecting fresh and disease-free okra tender fruits, cleaning surface impurities, and draining surface water;
(2) pre-dehydrating the tender okra fruits treated in the step (1) at low pressure;
(3) hot air drying the tender okra fruits obtained in the step (2);
(4) sealing and storing the tender okra fruits after hot air drying.
The hot air drying mechanism is that the okra is treated by hot air, heat is transferred from the outside to the inside, and when corresponding moisture is evaporated, the moisture on the surface is evaporated first, so that a water pressure difference is formed between the inside and the surface of the okra, and the moisture is gradually transferred and evaporated from the inside to the outside. Because the okra fruits contain a large amount of free water which is a good solvent for components such as inorganic salts in the okra fruits, the migration of the free water to the surface drives the migration of the components such as the inorganic salts to the surface, so that the surface of the okra is crusted and becomes dry and hard. The rehydration performance of the okra dried by hot air is greatly reduced. The inventor finds that the okra is subjected to pre-dehydration treatment in a low-pressure environment, water is directly boiled and evaporated in the okra by utilizing the reduction of the boiling point of the water at low pressure, and the migration of inorganic salts and the like caused by the movement of water is avoided. More importantly, the direct vaporization and evaporation of the moisture enables the surfaces of the okra to generate air holes, so that a more direct escape channel can be provided for the escape of the internal moisture under the action of hot air, the process intensity of the moisture re-evaporation after the moisture migrates from the inside to the surfaces in the hot air drying process is reduced, and the quality of the okra after the hot air drying is improved.
Preferably, the low-pressure in the step (2) is 100-700 Pa, and the final temperature after pre-dehydration is 4-10 ℃. The appropriate low pressure and final temperature after pre-dewatering should be maintained to remove the appropriate moisture.
Preferably, the air speed of the hot air drying in the step (2) is 1.0-1.5 m/s, and the temperature of the hot air is 45-55 ℃. Too high hot air temperature or too large solution causes the violence of water evaporation, resulting in large adverse effect of hot air drying.
Preferably, the low-pressure pre-dehydration of the tender okra fruits in the step (2) and the hot air drying in the step (3) are alternately carried out; preferably, the pressure of the low-pressure pre-dehydration is lower than that of the previous time, and the temperature of the hot air drying is higher than that of the previous time. The hot air drying process is a process of gradually removing water, the dehydration process is gradually deepened, the migration degree of inorganic salt and the like is also gradually deepened, and adverse phenomena such as aggravation of crusting and the like are possibly generated at the later stage of hot air drying and dehydration. Therefore, the low-pressure pre-dehydration and the hot air drying are alternately performed, and the deep hot air drying is avoided by using the air hole generation of the low-pressure pre-dehydration, so that the application intensity and the required maintenance time of the hot air drying are weakened. Meanwhile, a heat source for low-pressure dehydration is provided by utilizing the high temperature of the materials dried by the hot air, the dehydration capability and the moisture removal ratio of the low-pressure pre-dehydration to the hot air drying are enhanced, and the quality of the okra dried by the hot air is further improved.
Preferably, the alternating operation further comprises maintaining the okra for 1-2 hours under the environment with the relative humidity of 60-70% after the hot air drying and before the next low-pressure pre-dehydration. Because the shape difference of the different positions of okra makes the different positions of okra have the difference of being heated with the position of placing, hot air drying aggravates the uneven phenomenon of moisture distribution of each department of okra, through the moisture that the okra made each part of standing behind hot air drying takes place to remove, promotes the even maintenance of the inside moisture of okra to avoid lasting the moisture under the hot air drying condition and lack the dry and hard change at position.
Preferably, the step (1) further comprises the step of blanching the cleaned okra in water at 90-98 ℃ for 60-120 s. The mucilage contained in okra fruits is okra pectic polysaccharide, and the existing research shows that the reduction of pectin content can be caused by adopting hot air drying to prepare okra dry products, which probably causes that the high-temperature environment provided by the hot air drying is beneficial to the action of pectinase, so that the decomposition of pectin is accelerated (Xukang, the quality characteristics of okra and the application thereof in beer processing [ D ], Shandong agriculture university, 2016). Therefore, the okra is placed in water with the temperature of 90-98 ℃ for blanching in the pretreatment process to inhibit and destroy the activity of enzymes including pectinase, peroxidase and the like, and the decomposition energy of pectin in the hot air drying process is weakened. Meanwhile, researches show that the blanching treatment also has certain effect on improving the rehydration property of the okra and the like.
According to the method, the concentration of chitosan oligosaccharide is 35-45 g/L, and the concentration of tartaric acid is 0.8-2 g/L, the inventor finds that the rehydration of the dried okra obtained after the okra is blanched in an aqueous solution containing oligochitosan and tartaric acid is obviously improved, probably because okra fruits contain a large amount of high-esterified pectic polysaccharide mucilage, the okra is soaked in the aqueous solution of tartaric acid and oligochitosan, and the oligochitosan is soaked in the okra to enable the pectic polysaccharide in the okra to form a slight hydrophilic gel under the action of tartaric acid, so that the rehydration of the dried okra is improved, and the hydrophilic and film-forming properties of the oligochitosan enable the oligochitosan to form a hydrophilic film on the surface of the okra and enhance the rehydration of the dried okra.
Preferably, the water content of the okra preserved in a sealing way in the step (4) is less than or equal to 5 percent.
The invention has the following beneficial effects:
compared with the prior art, the method for drying the okra adopts low-pressure pre-dehydration to generate air holes on the surface of the okra, provides a water vapor escape path for drying and dehydrating the okra, weakens salt migration caused by dehydration of the okra and hardening of the okra caused by the salt migration, and improves the rehydration performance of the okra. Meanwhile, hot air drying and low-pressure dehydration are alternately carried out, and the mixed solution of chitosan oligosaccharide and tartaric acid is adopted for further treatment, so that the rehydration and hardness of the dried okra are effectively improved, and the quality of the hot air-dried okra is improved.
Detailed Description
The following further describes the embodiments of the present invention.
The starting materials used in the present invention are commercially available or commonly used in the art, unless otherwise specified, and the methods in the following examples are conventional in the art, unless otherwise specified.
Example 1
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh and disease-free okra tender fruits, cleaning surface impurities, and draining surface water;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at a low pressure of 200Pa, wherein the final temperature is 5 ℃ after pre-dehydration;
(3) hot air drying the okra tender fruit obtained in the step (2) until the water content of the okra is less than or equal to 5%, wherein the air speed of the hot air drying is 1.2m/s, and the temperature of the hot air is 50 ℃;
(4) sealing and storing the tender okra fruits after hot air drying.
Example 2
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh and disease-free okra tender fruits, cleaning surface impurities, and draining surface water;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at a low pressure of 100Pa, wherein the final temperature is 4 ℃ after pre-dehydration;
(3) hot air drying the okra tender fruit obtained in the step (2) until the water content of the okra is less than or equal to 5%, wherein the air speed of the hot air drying is 1.0m/s, and the temperature of the hot air is 55 ℃;
(4) sealing and storing the tender okra fruits after hot air drying.
Example 3
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh and disease-free okra tender fruits, cleaning surface impurities, and draining surface water;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at low pressure of 700Pa, wherein the final temperature is 10 ℃ after pre-dehydration;
(3) hot air drying the okra tender fruit obtained in the step (2) until the water content of the okra is less than or equal to 5%, wherein the air speed of the hot air drying is 1.5m/s, and the temperature of the hot air is 45 ℃;
(4) sealing and storing the tender okra fruits after hot air drying.
Example 4
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh and disease-free okra tender fruits, cleaning surface impurities, and draining surface water;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at a low pressure of 200Pa, wherein the final temperature is 5 ℃ after pre-dehydration;
(3) then hot air drying the tender okra fruits at the hot air drying speed of 1.2m/s and the hot air temperature of 50 ℃ until the water content of the okra is 55 +/-3 wt%;
(4) pre-dehydrating and hot-air drying okra tender fruits under the low pressure of 200Pa, wherein the final temperature is 5 ℃ after pre-dehydrating; then hot air drying treatment is carried out, wherein the hot air drying temperature is 50 ℃ until the water content of the okra is less than or equal to 5%;
(5) sealing and storing the tender okra fruits after hot air drying.
Example 5
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh and disease-free okra tender fruits, cleaning surface impurities, and draining surface water;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at low pressure of 700Pa, wherein the final temperature is 10 ℃ after pre-dehydration;
(3) then hot air drying the tender okra fruits at the hot air drying speed of 1.5m/s and the hot air temperature of 45 ℃ until the water content of the okra is 55 +/-3 wt%;
(4) pre-dehydrating and hot-air drying okra tender fruits under the low pressure of 100Pa, and keeping the final temperature of the pre-dehydrated tender fruits at 4 ℃; then hot air drying treatment is carried out, wherein the hot air drying temperature is 55 ℃ until the water content of the okra is less than or equal to 5%;
(5) sealing and storing the tender okra fruits after hot air drying.
Example 6
A method for drying okra, which is different from the method in example 4, in that the pressure of the primary low-pressure pre-dehydration in the step (2) is 600Pa, and the final temperature after pre-dehydration is 9 ℃.
Example 7
A method for drying okra, which is different from example 4 in that the pressure of the primary low-pressure pre-dehydration in the step (3) is 500Pa, and the final temperature after pre-dehydration is 8 ℃.
Example 8
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh and disease-free okra tender fruits, cleaning surface impurities, and draining surface water;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at low pressure of 700Pa, wherein the final temperature is 10 ℃ after pre-dehydration;
(3) then hot air drying the tender okra fruits at the hot air drying speed of 1.5m/s and the hot air temperature of 45 ℃ until the water content of the okra is 55 +/-3 wt%; placing the hot-air dried okra in an environment box with the temperature of 37 ℃ and the relative humidity of 70% for 1 h;
(4) pre-dehydrating the tender okra fruits taken out from the environmental box again under the low pressure of 100Pa, wherein the final temperature is 4 ℃ after pre-dehydration; then hot air drying treatment is carried out, wherein the hot air drying temperature is 55 ℃ until the water content of the okra is less than or equal to 5%;
(5) sealing and storing the tender okra fruits after hot air drying.
Example 9
A method for drying okra, which is different from embodiment 7 in that the okra young fruit subjected to the first hot air drying in step (3) is placed in an environment box with the temperature of 32 ℃ and the relative humidity of 60% for 2 hours.
Example 10
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh disease-free okra tender fruits, cleaning surface impurities, blanching in water at the temperature of 98 ℃ for 90s, taking out, and draining surface water;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at a low pressure of 200Pa, wherein the final temperature is 5 ℃ after pre-dehydration;
(3) hot air drying the okra tender fruit obtained in the step (2) until the water content of the okra is less than or equal to 5%, wherein the air speed of the hot air drying is 1.2m/s, and the temperature of the hot air is 50 ℃;
(4) sealing and storing the tender okra fruits after hot air drying.
Example 11
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh and disease-free okra tender fruits, cleaning surface impurities, blanching in water at the temperature of 98 ℃ for 90s, taking out and draining surface water, wherein the water contains 35 g/L oligochitosan and 0.8 g/L tartaric acid;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at a low pressure of 200Pa, wherein the final temperature is 5 ℃ after pre-dehydration;
(3) hot air drying the okra tender fruit obtained in the step (2) until the water content of the okra is less than or equal to 5%, wherein the air speed of the hot air drying is 1.2m/s, and the temperature of the hot air is 50 ℃;
(4) sealing and storing the tender okra fruits after hot air drying.
Example 12
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh disease-free okra tender fruits, cleaning surface impurities, blanching in water at the temperature of 98 ℃ for 90s, taking out and draining surface water, wherein the water contains 45 g/L oligochitosan and 2 g/L tartaric acid;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at a low pressure of 200Pa, wherein the final temperature is 5 ℃ after pre-dehydration;
(3) hot air drying the okra tender fruit obtained in the step (2) until the water content of the okra is less than or equal to 5%, wherein the air speed of the hot air drying is 1.2m/s, and the temperature of the hot air is 50 ℃;
(4) sealing and storing the tender okra fruits after hot air drying.
Example 13
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh and disease-free okra tender fruits, cleaning surface impurities, blanching in water at the temperature of 98 ℃ for 90s, taking out and draining surface water, wherein the water contains 40 g/L oligochitosan and 1.5 g/L tartaric acid;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at a low pressure of 200Pa, wherein the final temperature is 5 ℃ after pre-dehydration;
(3) hot air drying the okra tender fruit obtained in the step (2) until the water content of the okra is less than or equal to 5%, wherein the air speed of the hot air drying is 1.2m/s, and the temperature of the hot air is 50 ℃;
(4) sealing and storing the tender okra fruits after hot air drying.
Example 14
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh and disease-free okra tender fruits, cleaning surface impurities, blanching in water at the temperature of 98 ℃ for 90s, taking out and draining surface water, wherein the water contains 40 g/L oligochitosan and 1.5 g/L tartaric acid;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at low pressure of 700Pa, wherein the final temperature is 10 ℃ after pre-dehydration;
(3) then hot air drying the tender okra fruits at the hot air drying speed of 1.5m/s and the hot air temperature of 45 ℃ until the water content of the okra is 55 +/-3 wt%;
(4) pre-dehydrating and hot-air drying okra tender fruits under the low pressure of 100Pa, and keeping the final temperature of the pre-dehydrated tender fruits at 4 ℃; then hot air drying treatment is carried out, wherein the hot air drying temperature is 55 ℃ until the water content of the okra is less than or equal to 5%;
(5) sealing and storing the tender okra fruits after hot air drying.
Example 15
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh and disease-free okra tender fruits, cleaning surface impurities, blanching in water at the temperature of 98 ℃ for 90s, taking out and draining surface water, wherein the water contains 40 g/L oligochitosan and 1.5 g/L tartaric acid;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at low pressure of 700Pa, wherein the final temperature is 10 ℃ after pre-dehydration;
(3) then hot air drying the tender okra fruits at the hot air drying speed of 1.5m/s and the hot air temperature of 45 ℃ until the water content of the okra is 55 +/-3 wt%; placing the hot-air dried okra in an environment box with the temperature of 37 ℃ and the relative humidity of 70% for 1 h;
(4) pre-dehydrating the tender okra fruits taken out from the environmental box again under the low pressure of 100Pa, wherein the final temperature is 4 ℃ after pre-dehydration; then hot air drying treatment is carried out, wherein the hot air drying temperature is 55 ℃ until the water content of the okra is less than or equal to 5%;
(5) sealing and storing the tender okra fruits after hot air drying.
Comparative example 1
Cleaning fresh okra without insect pests, draining off surface water, and drying with hot air at a wind speed of 1.5m/s and a temperature of 45 ℃ until the water content of the okra is less than or equal to 5 wt%.
Comparative example 2
A method for drying okra, comprising the steps of:
(1) selecting 50 fresh and disease-free okra tender fruits, cleaning surface impurities, blanching in water at the temperature of 98 ℃ for 90s, wherein the water contains 2 g/L calcium chloride, taking out, and draining off surface water;
(2) pre-dehydrating the okra tender fruit treated in the step (1) at a low pressure of 200Pa, wherein the final temperature is 5 ℃ after pre-dehydration;
(3) hot air drying the okra tender fruit obtained in the step (2) until the water content of the okra is less than or equal to 5%, wherein the air speed of the hot air drying is 1.2m/s, and the temperature of the hot air is 50 ℃;
(4) sealing and storing the tender okra fruits after hot air drying.
Results testing
The dried okra tender fruit products obtained in examples 1 to 15 and comparative examples 1 to 2 were rehydrated, shrunk and hardened.
Wherein:
the rehydration is to keep the temperature of the okra tender fruit dry product in water at 35 ℃ for 60min, take out the product and drain the surface water, and calculate the mass ratio of the product after rehydration to the product before rehydration.
The methods for testing the shrinkage and hardness refer to a method for determining the appearance quality of the fresh okra fruits at dawn (research on the process of drying the fresh okra fruits in a vacuum freezing-hot air series combined manner [ D ], Jiangsu university, 2013).
The above test results were recorded for each okra in the examples and comparative examples, and then averaged.
The test results of each example and comparative example are shown in table 1 below.
As can be seen from the above table, the quality of the okra treated by the method of the invention, such as rehydration property, hardness and the like, is obviously improved compared with the quality of the okra treated by direct hot air drying.
Claims (8)
1. A method for drying okra, which is characterized by comprising the following steps:
(1) selecting fresh and disease-free okra tender fruits, cleaning surface impurities, and draining surface water;
(2) pre-dehydrating the tender okra fruits treated in the step (1) at low pressure;
(3) hot air drying the tender okra fruits obtained in the step (2);
(4) sealing and storing the tender okra fruits after hot air drying.
2. The method for drying okra according to claim 1, wherein the low pressure in the step (2) is 100 to 700Pa, and the final temperature after pre-dehydration is 4 to 10 ℃.
3. The method for drying okra according to claim 1, wherein the air speed of the hot air drying in the step (2) is 1.0 to 1.5m/s, and the temperature of the hot air is 45 to 55 ℃.
4. The method for drying okra according to any one of claims 1 to 3, wherein the low-pressure pre-dehydration of okra young fruits in the step (2) and the hot air drying of the step (3) are alternately performed.
5. The method for drying okra according to claim 4, wherein the alternating operation further comprises maintaining the okra at a relative humidity of 60% to 70% for 1 to 2 hours after the hot air drying and before the next low-pressure pre-dehydration.
6. The method for drying the okra according to claim 1, wherein the step (1) further comprises the step of blanching the cleaned okra in water at 90-98 ℃ for 60-120 s.
7. The method for drying okra according to claim 6, wherein the blanching water of step (1) contains 35-45 g/L oligochitosan and 0.8-2 g/L tartaric acid.
8. The method for drying okra according to claim 1, wherein the water content of okra preserved in a sealed manner in the step (4) is less than or equal to 5%.
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