What are the prospects for freeze-dried food development and freeze-dried foods for okra?

Freeze-dried food is the use of vacuum freeze-drying technology for primary agricultural products to maintain freshness, color, quality, dehydrated new food, its shape unchanged, color, aroma, taste, protein, carbohydrates, vitamins and other nutrients are well preserved, and after sealing and packaging, freeze-dried food can be at room temperature for long-term storage, transportation and sales.

Okra is a new type of healthy vegetables with high nutritional value, in addition to rich in carbohydrates, proteins, fats, vitamins, minerals and dietary fiber and other basic nutrients, rich in flavonoids, polysaccharides so that okra has a higher nutritional value and more health care functions, not only help to protect the skin, gastrointestinal tract, liver, but also improve the ability to resist fatigue. In addition, the low-sugar and low-fat characteristics of okra can be used as a slimming food, and even become the first choice of vegetables for athletes’ nutritional diets in many countries.

Freeze-drying technology has great advantages in the preservation of food and the retention of nutrients, and the use of freeze-drying technology for the processing of okra will produce considerable benefits. At present, the freeze-dried food types of okra include okra freeze-dried powder, freeze-dried crisps, freeze-dried prototype okra fruits and so on.

Through the freeze-drying process developed by the freeze-dried okra food, with the unchanged unique appearance, crunchy taste, salty and sweet, nutritious and other advantages, will become a popular new leisure health food.

Development and utilization of okra

China began to introduce okra in 1996, in recent years, there are cultivation in some areas of China, but also began the demonstration and promotion, the initial formation of industrialized mode of operation. As a new characteristic vegetable, the development and utilization of okra has a broad development prospect. Our researchers are working hard to study the comprehensive development and utilization of okra.

1.okra young fruit

1.1 okra young fruit preservation

Okra can be used for quick-freezing and fresh refrigeration, harvesting its young fruit often in the hot season. Because of the thin skin and high moisture content of okra, coupled with developed stomata and lenticels, the temperature and various types of preservatives are also more sensitive, in the summer temperature is more than 28 ℃ in Guangdong, the picking of water loss and respiration rate is extremely fast, its storage resistance is very poor, generally after picking the okra young fruits placed at room temperature for a few hours, there will be a reduction in the quality of the quality of the fiber increase, quality deterioration, etc., 2 ~ 3d after the may be completely wilted or even rot, even if the low temperature of the young fruits of the okra. Even if stored at low temperature, the longest freshness period is only 2~3 d, which seriously affects the shelf time of okra, and if directly put into cold storage, it is easy to be frostbitten, resulting in serious losses.

And okra harvest period is concentrated in May ~ October each year, uneven distribution of the listing period, often appear off-season supply shortage, the phenomenon of a sharp rise in prices. In the future, in the okra young fruit preservation, mainly to use the series of quick-frozen process for its preservation of cold storage, and research on its most suitable storage and preservation methods.

Quick-frozen okra young fruit process method:

Selection of raw materials and finishing → cleaning → drying → drug immersion → scalding → leaching intervention cold → packaging → quick-freezing → refrigeration.

One of the “bleaching” process is the key technology of frozen okra products, the quality of its young fruit plays a key role. Without bleaching directly frozen okra poor color, poor taste, after 4 months of storage will begin to taste. And after appropriate rinsing of okra in storage after 9 months taste is still fresh, flavor remains, the shortcomings of the fiber slightly increased.

In order to extend the storage time of okra, Huang Shao Li et al. flash-frozen frozen okra with a series of quick-freezing process, after bleaching treatment, its freshness can reach 9 months. Chen Jiangping’s study was carried out at a temperature of 1 to 3°C. The storage time of okra could be extended to 30 d by using a freshness preservative mixed with a deethening agent (K2MnO4) consisting of 0.1 g/kg of sodium dehydroacetate, 2.0% N,O-carboxymethylchitosan, and 25 μg/mL of 6-benzylaminoadenine (6-BA) together with a plastic bag with a thickness of 0.02 mm for packing the okra.

Although the storage conditions of okra have been gradually improved, researchers are also constantly conducting in-depth research to find more suitable storage methods, but so far okra is still not in the market to get the majority of the crowd’s favorite, the reason is that the product taste can not cater to the public, such as the product a little bit old fiber is too much, the taste is very light, there is a viscous material, the appearance of the color is easy to turn brown, coupled with the high cost of production leading to the selling price In addition, the high production cost leads to the high selling price, which makes it not attractive enough, and its nutritional function has not been popularized and so on.

As the appearance of okra itself is unique, striking, if you can keep its appearance beautiful, but also can be made into leisure health food, will be more attractive to the public eye. Crunchy taste, nutritious okra processing products will be the public’s expectations.

1.2 Canned okra

Okra young fruit can be made canned, the basic processing technology is as follows:

Selection of raw materials → cleaning and trimming → lye treatment → hot blanching → vacuum hardening and preservation of crisp → rinsing → bagging → vacuum sealing sterilization → cooling → finished product.

Hot blanching at 85 ~ 95 ℃ canning 2 ~ 3min, while adding green combination of liquid (200 mg / kg CuCl2 + 200 mg / kg ZnCl2), is conducive to maintaining the bright green and crispy quality of okra; the first infiltration temperature of 60 ℃, the concentration of sodium alginate 1.4%, the second infiltration temperature of 60 ℃, the concentration of calcium chloride 0.5%; 121 ℃ sterilized 15 ~ 20 min to achieve the ideal temperature! The ideal effect can be achieved in ～20 min.

Thus developed canned okra production process, due to ensure its color, crisp quality, nutritional value, etc., after canning okra crispy, soup bright, shelf life of 18 months.

1.3 Okra health yogurt

Okra can make health milk. Li Yi-en and other okra and milk powder as the main raw material, optimize the amount of okra added, homogenization pressure, hydration time and other conditions, developed a new type of health care yogurt okra, its flavor is also very good.

2.Okra natural coloring and stem and leaf powder

The leaves of okra are rich in lutein and β-carotene. Okra has the advantageous conditions for cultivation and application as a natural colorant resource plant, which is a rare new feed colorant resource plant and is very suitable for the production of natural feed colorant.

The biological yield of okra is high, and the production cost of stem and leaf powder is low. Using okra stem and leaf powder as coloring agent, adding 4% or 5% of okra stem and leaf powder to the full-price feed of laying hens, the eggs and the chicken skin can reach a more desirable coloring effect in about 14 d. The coloring effect can be achieved by adding okra stem and leaf powder as a feed ingredient for laying hens.

It is added as a feed ingredient, comprehensively said to play a coloring agent and as a feed ingredient of the double effect, can play a good coloring effect, to provide part of its nutrition, eliminating the original coloring agent, egg yolk color level and broiler, egg economic benefits have been significantly improved, but also more in line with people’s security psychological needs. Therefore, okra in the egg and broiler rearing industry has a broader application prospects.

3.Okra seed oil

Okra seeds are nearly spherical, 4~5mm in diameter, although the fat content is high, but its skin is very hard, which brings some difficulties to the oil production and processing technology. Okra and cotton belong to the same mallow family, the chemical composition of its seed oil is similar to that of cottonseed oil, therefore, the preparation and refining of okra seed oil can be taken to the preparation of cottonseed oil process and equipment, without change can be used directly to produce okra seed oil. Okra seed oil contains a small amount of cotton phenol, can be removed after refining, after refining the okra seed oil can be consumed.

4. Flavonoids of okra

The extraction methods of flavonoids in soybean mainly include: acid hydrolysis, enzyme hydrolysis, high-pressure extraction, organic solvent extraction, microwave extraction, ultrafiltration extraction, ultrasonic technology extraction and supercritical fluid extraction. Determined that the total flavonoid content of okra seeds is 2.8%, compared with soybeans, the content is very rich, and can be used as a new source of natural flavonoids.

5. Okra functional food

The use of aqueous extract of okra can significantly improve the endurance of mice and heat, cold and hypoxia resistance, significantly reduce the level of blood lactate after strenuous exercise, improve the ability of mice to survive in a state of stress, the recovery of physical strength, anti-fatigue ability of the improvement of the experimental results have a promotional role in the research and development of the development of okra as a functional food or drink, to provide to the needs of a specific group of people.

Application status of freeze-drying technology

Freeze-drying is the abbreviation of vacuum freeze-drying technology, which is a high-end food processing technology for astronautics that has not yet been popularized, and it is also the best processing method for producing high-quality dehydrated food. In the low temperature below freezing point using the principle of sublimation, in a vacuum state so that the pre-frozen agricultural materials water without the melting of ice directly to ice sublimation of water vapor and remove, so that agricultural materials quickly dry, with this technology to produce food is freeze-dried food.

Now China’s food freeze-drying technology application is still very insufficient or less, but China can use freeze-drying technology to process food resources are very rich, especially high-priced agricultural products and local specialties, such as honey, oysters, abalone, okra, four-pronged bean, rose eggplant, ganoderma lucidum, mushrooms, lychee, kiwi fruit, longan, soybean products, corn, coconut milk, garlic, carex, tea and other products. It is expected that the food freeze-drying industry will be rapid development in China’s new, fashionable and other agricultural applications.

However, freeze-drying technology also exists many problems to be solved, for example, the main obstacle affecting the wide application of freeze-drying technology is that the production cost is still too high, shorten the freeze-drying cycle, improve the comprehensive utilization of energy, strengthen the function of the device, reduce the energy consumption of the device, reduce the cost of the equipment, and improve the production efficiency of the unit of time, etc. are all the topics that need to be solved for the development of the food freeze-drying industry.

1. Comparison of freeze-drying and thermal drying processes

Freeze-drying technology is a kind of drying process to make materials dehydrated under low temperature and low pressure. Compared with other drying methods, it has the advantages of no deterioration of drugs, easy long-term storage, accurate dosing of pharmaceutical agents, thorough dehydration, easy rehydration and regeneration, easy aseptic operation, conducive to the maintenance of activity of heat-sensitive drugs, and less loss of volatile components. The following is a comparison of freeze-drying and thermal drying two processes, discussing the advantages of freeze-drying technology in the food drying process.

1.1 Sensory aspect

Freeze-drying okra and other food products such as shape, color, taste basically maintained, in the process of water sublimation, its water molecule state from the surface and gradually removed, neither destroy the organizational structure, nor take away the aromatic substances and natural pigments. The sensory quality of heat-dried okra is poor.

1.2 rehydration

After drying (processing) of okra and other foodstuffs are generally rehydrated before cooking and eating, and its product quality is generally measured by the degree of rehydration to restore the original fresh state. Okra and other freeze-dried food can be basically restored to the fresh state before dehydration after rehydration, its tissue from brittle to soft, can quickly and completely re-absorb water recovery, easy to eat. This is because in the sublimation process, its food in the location of ice crystals formed similar to the sponge like microporous, immersed in water can be immediately absorbed water recovery, recovery and the original fresh products almost. The organization of thermally dried foods such as okra is relatively dry and thin and tough, so it cannot be consumed immediately after rehydration. This may be thermal drying process processing temperature is high, so that the solid cell wall collapse, the tissue is easy to soften, water and gas diffusion channel is often closed due to.

1.3 Nutritional composition

Freeze-drying technology process is less destructive to the nutrient composition, mainly because freeze-drying is a technology to produce food under low temperature and low air pressure (lack of oxygen), which effectively prevents the decomposition or oxidation of some components in the material, inhibits the harmful effects of microorganisms and biological enzymes, and has the advantages of maintaining the freshness of the food and retaining its nutrient composition.

In the preservation of general nutrients such as fat, starch, crude fiber, dietary fiber, total sugar, etc., the difference between freeze-drying process and thermal drying process is not very big; however, freeze-drying process is better for the preservation of proteins and amino acids, while thermal drying process is more destructive to them.

Both processes are destructive to vitamins, but comparatively speaking, freeze-drying process can preserve more vitamins than thermal drying process, and freeze-drying process can protect most vitamins from being destroyed in large quantities, such as the protection of VC. In addition, the freeze-drying process did not affect unsaturated fatty acids significantly.

Freeze-drying and heat-drying dehydrated okra and other foods are edible and convenient cooking, easy to long-distance transportation and long-term storage of common characteristics, but the advantages of freeze-dried food is more prominent. With the expansion of the scale of processing freeze-dried food, technological advances, freeze-dried okra and other food production costs will gradually reduce the benefits will be increasingly high.

The development prospect of freeze-dried okra and other foods

In the early stage of the development of freeze-dried food, due to the high cost of production, resulting in low yield, high prices, freeze-dried food use is limited to the universe of spaceflight, ocean fishing voyage, mountainous areas of operation, polar expedition and disaster relief and rescue, and so on. Since the 1990s, with the increase of domestic and foreign demand, the expansion of production scale, the updating of production technology and the improvement of localization of production equipment, the production cost of freeze-dried food has been decreasing, and the varieties and quantities of freeze-dried food have been growing rapidly.

1. Huge market demand

At present, freeze-dried food is in short supply in the international market. On the one hand, our country has abundant fruits and vegetables, meat and aquatic resources, on the other hand, the cost of processing such food resources into freeze-dried food is relatively low, therefore, the development of freeze-dried okra and other vegetables, lychee, longan, freeze-dried beef jerky, oysters and so on for export is a project of exporting foreign exchange earning with large profit, small risk and promising future. With the economic development, China’s affluent well-off families are more and more, and their demand for nutritious, healthy and safe agricultural food is also gradually increasing, freeze-dried food in line with the development trend of this domestic market, which undoubtedly gives the development of freeze-dried food to provide a larger domestic market and stage.

2. Considerable economic benefits

Freeze-dried food production costs are higher, the sales price is higher, but as a leisure food can also be small packages, so the benefits are very good. Due to the low moisture content of freeze-dried food, good quality and light weight, greatly reducing its transportation and operating costs. For example, after freeze-drying process, 1kg of fresh tomato paste material can be processed into 320g of freeze-dried tomato paste powder, its freshness period of 3 ~ 5a. Freeze-dried tomato paste powder has become a substitute for ketchup.

The larger the scale of processing freeze-dried food, the higher its benefits. Such as freeze-drying area of 200m2 production line, need to invest in production equipment more than 600 million yuan, each year, each with 100d processing carrots diced, garlic slices, beef and other products, the annual output value of up to more than 3,000 million yuan. If the processing and production of more high-grade agricultural products, such as okra, beans, oysters, abalone, ganoderma lucidum powder, etc., the benefit is higher.

China has abundant fruits and vegetables, meat, aquatic and other resources, agricultural products have long been hovering in the export of raw materials or primary processing stage, the added value is very low, the economic benefits are not ideal. If such food resources are processed into freeze-dried food, to develop a variety of such as freeze-dried okra and other vegetables, freeze-dried meat and other high-value-added deep-processed products, will bring considerable economic and social benefits.

3. Considerable development prospects

China’s okra and other agricultural products processing has been seriously inadequate, often hovering in the unprocessed crude products or primary processed products stage, the technical content is low. The development of freeze-dried okra vegetables and other food products, will obtain a higher added value, improve the grade of China’s export food. The successful development of freeze-dried okra and other freeze-dried food will bring a surprise to the mid- and high-grade emerging markets and consumers.

Long-term traditional industrialized means to produce a large number of food, the impact on health so that consumers are worried about food safety has become an imminent livelihood issues. Freeze-dried food is non-toxic, harmless, green, natural and traceable, which will ease the worries of consumers. This kind of assured and traceable medium and high-grade food is bound to be very popular in the market.

Some local famous and special agricultural products around China will become high-grade dehydrated famous and special products after freeze-drying process. The successful development of freeze-dried food, China’s agriculture, food industry, is a “good” news. The popularization of freeze-drying technology will boost China’s resource advantages into economic advantages and market advantages, and promote China’s transformation from a large agricultural country into an agricultural powerhouse.

Summarize

For some time now, okra has not been given enough attention in China’s agricultural development, but its potential business opportunities cannot be ignored. With the increasing demand for nutritious, healthy and safe functional food, coupled with the outstanding nutritional and medicinal functions and processing characteristics of okra, it can be used as a high-grade vegetable and can be developed into a new type of nutritious, healthy and safe functional food, which has received more and more widespread attention.

At present, the domestic research on okra is still mainly focused on the appearance of morphology, nutrient content, the introduction of cultivation, variety selection and breeding, on the comprehensive development and utilization of its whole body of research is very little, the future further development and utilization of this new vegetable with high potential, serving the people’s healthy life will become a R & D hotspot, it is worth looking forward to.

Looking ahead, to play the potential value of okra, we must find a new way to store okra, which not only reduces the effect of fiber on taste, but also maintains the unique appearance of okra, the use of freeze-drying technology is expected to make it become a new type of leisure and health food that attracts the public’s attention, and is integrated into people’s daily life.