Microwave combined color protection pretreatment method for improving quality of mangoes dried by hot air

Abstract

The invention belongs to the technical field of fruit and vegetable product processing, and discloses a microwave combined color protection pretreatment method for improving the quality of hot air dried mangoes. The method comprises the following steps: selecting mango which is smooth in appearance and free of mechanical damage and is 70-80% mature as a raw material; cleaning the selected mangoes, peeling and denucleating the mangoes, and cutting the mangoes into mango blocks; soaking the mango blocks in a color protection solution (the formula of the color protection solution is as follows: 100mL of the color protection solution contains 0.5 g of ascorbic acid, 0.5 g of citric acid and 0.5 g of calcium chloride), and then treating for 1min under 800W microwaves; and drying the pretreated mango blocks in a hot air drying box until the water mass content is 20%, so as to obtain the dried mango product. By adopting the method disclosed by the invention, the drying time of the mangoes can be shortened to a certain extent, the browning phenomenon of the mangoes in the drying process is inhibited, the color is better, the nutritional components of the mangoes are retained to the maximum extent, and the nutritional value is higher.

Description

Technical Field

[0001] The invention belongs to the technical field of fruit and vegetable product processing, and particularly relates to a microwave combined color protection pretreatment method for improving the quality of hot air dried mangoes. Background Art

[0002] Mango is a fruit widely grown in tropical and subtropical regions. It has a juicy flesh, a sweet and delicious taste, and a high nutritional value. As a respiratory climacteric fruit, mangoes still undergo metabolism after harvest and are easily rotten and deteriorated by microorganisms, resulting in great waste. In order to extend the shelf life, mangoes are often processed into various products, such as dried mangoes, mango candies, and mango powder. In recent years, snack foods such as dried mangoes have been deeply loved by consumers because of their convenience and unique taste, and have good market prospects.

[0003] Drying and dehydration are the core steps in making dried fruits and vegetables. Among them, hot air drying is favored by processing companies because of its low cost and simple operation. However, traditional hot air drying takes a long time, and long-term heat treatment damages the texture, color and nutritional value of the product, which cannot meet consumers' demand for high-quality products. In order to overcome the limitations of traditional hot air drying process, it is possible to consider using advanced pretreatment technology to enhance the efficiency of hot air drying.

[0004] Pretreatment technologies to enhance the efficiency of hot air drying can be divided into physical pretreatment and chemical pretreatment:

[0005] Microwaves are a common physical pretreatment method, in which microwaves use electromagnetic fields to cause fruit and vegetable molecules to oscillate rapidly and generate heat through friction. Its internal heating mode can create a pressure gradient within the material, promote water seepage, and accelerate dehydration.

[0006] Ethanol, sucrose and acid treatment are common methods in chemical pretreatment. For ethanol pretreatment, although it can greatly shorten the drying time of fruits and vegetables, a large number of alcohol-soluble nutrients will be degraded during the pretreatment process, resulting in a decrease in the nutritional value of the product. Sugar solution pretreatment is a method of soaking fruits and vegetables in a high-concentration sugar solution and removing part of the water from the material tissue by using the high osmotic pressure difference between the material and the solution as a driving force. In this process, water diffuses from the tissue cells of the material to the hypertonic solution, and the solutes in the hypertonic solution enter the interior of the material. It is worth noting that as the water migrates to the outside, the soluble substances in the material may also be dissolved, which will have a certain impact on the quality of the product. As for acid treatment, it can reduce the rate of enzymatic browning by inhibiting the activity of polyphenol oxidase in fruits and vegetables. In addition, acidic conditions can enhance the stability of pigments such as betaine, anthocyanin and carotenoid. At present, citric acid and ascorbic acid are the two most studied and used colorants. Citric acid is an organic acid and is the most commonly used browning inhibitor and texture modifier in fruits and vegetables. At the same time, the acidic environment created by citric acid can weaken the cell walls of fruits and vegetables, thereby promoting the removal of water and accelerating the drying process. Ascorbic acid is an antioxidant that can reduce quinone compounds to colorless dihydroxyphenols. However, since ascorbic acid has difficulty penetrating into the cell matrix, its inhibitory effect on browning is poor, so it is generally combined with citric acid to protect the color of fruits and vegetables.

[0007] Generally speaking, the effect of physical pretreatment or chemical pretreatment alone is not obvious. With the increasing demand for product quality, we can explore pretreatment technologies with higher drying efficiency and greater positive impact on product quality by combining physical pretreatment with chemical pretreatment. Summary of the invention

[0008] In order to overcome the shortcomings and deficiencies in the prior art, the object of the present invention is to provide a microwave combined color protection pretreatment method for improving the quality of hot air dried mangoes, so as to achieve the effect of improving the color and nutritional quality characteristics of dried mangoes.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A microwave combined color protection pretreatment method for improving the quality of hot air dried mangoes, comprising the following steps:

[0011] (1) Raw material selection: Select mangoes that are 70% to 80% mature and have a smooth surface and no mechanical damage as raw materials;

[0012] (2) Pre-treatment: Wash the selected mangoes, peel and core them, and then cut them into mango pieces;

[0013] (3) Pretreatment: pretreating the mango pieces obtained in step (2), immersing the mango pieces in a color protection solution, and performing microwave pretreatment;

[0014] (4) Hot air drying: The mango pieces pretreated in step (3) are dried in a hot air drying oven until the moisture content is 20% by weight, thereby obtaining a dried mango product.

[0015] The mango pieces in step (2) have a diameter of 2.5 cm and a height of 1.0 cm, and each piece of mango weighs 5.0±0.1 g.

[0016] The formula of the color protection solution in step (3) is as follows: 100 mL of the color protection solution contains 0.5 g of ascorbic acid, 0.5 g of citric acid, and 0.5 g of calcium chloride.

[0017] In step (3), the mango pieces are immersed in a color protection solution at a solid-liquid ratio of 1 g:10 mL; and the microwave pretreatment is performed at 800 W microwave for 1 min.

[0018] The temperature of the hot air drying oven in step (4) is set at 60°C.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] (1) The microwave-color protection technology of the present invention can shorten the drying time of mangoes to a certain extent.

[0021] (2) The pretreatment technology of the present invention can suppress the browning of mangoes during the drying process, and the color is better.

[0022] (3) By adopting the pretreatment technology of the present invention, the nutritional components of mango are retained to the greatest extent, and the obtained dried mango product has a higher nutritional value. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The figure is a flow chart of the pretreatment and drying method of the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described below with reference to specific embodiments, but they should not be construed as limiting the present invention.

[0025] Embodiment 1 (microwave-color protection pretreatment):

[0026] (1) Raw material selection: Select mangoes that are 70% to 80% mature and have a smooth surface and no mechanical damage as raw materials;

[0027] (2) Pretreatment: The selected mangoes were cleaned, peeled and pitted, and then cut into mango pieces with a diameter of 2.5 cm and a height of 1.0 cm (each piece weighing about 5.0 ± 0.1 g);

[0028] (3) Pretreatment: The mango pieces obtained in step (2) were pretreated by soaking the mango pieces in a color protection solution (containing 0.5 g ascorbic acid, 0.5 g citric acid, and 0.5 g calcium chloride per 100 mL of the color protection solution) at a solid-liquid ratio of 1 g:10 mL, and then treated under 800 W microwave for 1 min;

[0029] (4) Hot air drying: The mango pieces pretreated in step (3) are quickly removed from the color protection solution, the surface moisture of the pulp is absorbed with absorbent paper, and the mango pieces are dried in a hot air drying oven at 60° C. until the moisture content is 20% by weight, thereby obtaining a dried mango product.

[0030] Example 2 (control pretreatment):

[0031] (1) Raw material selection: Select mangoes that are 70% to 80% mature and have a smooth surface and no mechanical damage as raw materials;

[0032] (2) Pretreatment: The selected mangoes were cleaned, peeled and pitted, and then cut into mango pieces with a diameter of 2.5 cm and a height of 1.0 cm (each piece weighing about 5.0 ± 0.1 g);

[0033] (3) Pretreatment: No pretreatment was done on the mango pieces;

[0034] (4) Hot air drying: The mango pieces were dried in a hot air drying oven at 60° C. until the moisture content was 20% by weight, thereby obtaining a dried mango product.

[0035] Embodiment 3 (microwave-ethanol pretreatment):

[0036] (1) Raw material selection: Select mangoes that are 70% to 80% mature and have a smooth surface and no mechanical damage as raw materials;

[0037] (2) Pretreatment: The selected mangoes were cleaned, peeled and pitted, and then cut into mango pieces with a diameter of 2.5 cm and a height of 1.0 cm (each piece weighing about 5.0 ± 0.1 g);

[0038] (3) Pretreatment: pretreating the mango pieces obtained in step (2), soaking the mango pieces in a 75% volume percent ethanol solution at a solid-liquid ratio of 1 g:10 mL, and treating them under a microwave at 800 W for 1 min;

[0039] (4) Hot air drying: The mango pieces pretreated in step (3) are quickly removed from the color protection solution, the surface moisture of the pulp is absorbed with absorbent paper, and the mango pieces are dried in a hot air drying oven until the moisture content is 20% by weight, thereby obtaining a dried mango product.

[0040] Embodiment 4 (microwave-sucrose pretreatment):

[0041] (1) Raw material selection: Select mangoes that are 70% to 80% mature and have a smooth surface and no mechanical damage as raw materials;

[0042] (2) Pretreatment: The selected mangoes were cleaned, peeled and pitted, and then cut into mango pieces with a diameter of 2.5 cm and a height of 1.0 cm (each piece weighing about 5.0 ± 0.1 g);

[0043] (3) Pretreatment: pretreating the mango pieces obtained in step (2), immersing the mango pieces in a sucrose solution with a mass percentage concentration of 50% at a solid-liquid ratio of 1 g:10 mL, and treating them under a microwave at 800 W for 1 min;

[0044] (4) Hot air drying: The mango pieces pretreated in step (3) are quickly removed from the color protection solution, the surface moisture of the pulp is absorbed with absorbent paper, and the mango pieces are dried in a hot air drying oven until the moisture content is 20% by weight, thereby obtaining a dried mango product.

[0045] In order to illustrate the beneficial effects of the present invention in detail, experimental results are further provided. The relevant physical and chemical indicators of the dried mango products produced by the four different processing processes of the above Examples 1-4 are detected and recorded, as shown in the following Table 1:

[0046] Table 1 Physical and chemical indicators of dried mango produced by different pretreatment methods

[0047]

[0048] As can be seen from the experimental results in Table 1 above, when dried to a moisture content of 20%, the drying time of microwave-color-protected dried mango is less than that of the control treatment and microwave-sucrose pretreatment. In addition, the browning degree of the dried mango treated by the control and microwave-sucrose pretreatment is higher, and the biological activity is significantly reduced. The dried mango processed by the pretreatment method of the present invention has moderate hardness, improved brightness (L*), reduced browning degree, better protection of nutritional components (total phenols, carotenoids, ascorbic acid), and significant improvement in antioxidant activity (DPPH free radical scavenging rate), indicating that the nutritional value of the product is higher. Although the drying time can be greatly shortened by soaking mango in ethanol solution pretreatment, its flavor and nutritional value will be affected compared with the soaking treatment of the color-protecting solution of the present invention, which is far less good than the flavor of the present invention and high nutritional value.

[0049] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A microwave combined color protection pretreatment method for improving the quality of hot air dried mangoes, characterized in that The steps include: (1) Raw material selection: Select mangoes that are 70% to 80% mature and have a smooth surface and no mechanical damage as raw materials; (2) Pre-treatment: Wash the selected mangoes, peel and core them, and then cut them into mango pieces; (3) Pretreatment: pretreating the mango pieces obtained in step (2), immersing the mango pieces in a color protection solution, and performing microwave pretreatment; (4) Hot air drying: The mango pieces pretreated in step (3) are dried in a hot air drying oven until the moisture content is 20% by weight, thereby obtaining a dried mango product.

2. A microwave combined color protection pretreatment method for improving the quality of hot air dried mangoes according to claim 1, characterized in that: The mango pieces in step (2) have a diameter of 2.5 cm and a height of 1.0 cm, and each piece of mango weighs 5.0±0.1 g.

3. A microwave combined color protection pretreatment method for improving the quality of hot air dried mangoes according to claim 1, characterized in that: The formula of the color protection solution in step (3) is as follows: 100 mL of the color protection solution contains 0.5 g of ascorbic acid, 0.5 g of citric acid, and 0.5 g of calcium chloride.

4. A microwave combined color protection pretreatment method for improving the quality of hot air dried mangoes according to claim 1, characterized in that: In step (3), the mango pieces are immersed in a color protection solution at a solid-liquid ratio of 1 g:10 mL; and the microwave pretreatment is performed at 800 W microwave for 1 min.

5. The microwave combined color protection pretreatment method for improving the quality of hot air dried mangoes according to claim 1, characterized in that: The temperature of the hot air drying oven in step (4) is set at 60°C.

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