Dehydration method of fresh and wet sweet potato residues

Abstract

The invention discloses a fresh and wet sweet potato residue dehydration method which comprises the following steps: preparing fresh and wet sweet potato residues and a water absorbing medium, and determining the compounding mass ratio of the water absorbing medium to the fresh and wet sweet potato residues based on the condition that the moisture content of the compounded sweet potato residues is less than or equal to 60%; pouring the fresh and wet sweet potato residues and a water absorbing medium into stirring equipment according to a compounding mass ratio, and uniformly stirring and mixing to obtain compound sweet potato residues; the obtained compound sweet potato residues are dried through a roller dryer until the water content is reduced to be within 10%, finished sweet potato residues are obtained, dehydration is completed, and the whole dehydration process is low in manufacturing cost, short in consumed time, low in energy consumption and beneficial to popularization.

Description

Technical Field

[0001] The present invention relates to the technical field of fresh and wet sweet potato residue treatment, and particularly relates to a method for dehydrating fresh and wet sweet potato residue. Background Art

[0002] The difficulty in dehydrating sweet potato residue has always been the primary technical bottleneck affecting the resource utilization of sweet potato residue. At present, in industry, the combination of pressure filtration and hot air drying is often used to treat fresh and wet sweet potato residue. However, the filter press can only squeeze out about 20% of the water, that is, 60 - 70% of the water in the sweet potato residue still needs to be further dried. The treatment efficiency is low, and the sweet potato residue after pressure filtration is prone to caking during the drying process. Through research by the research group, it is found that the presence of pectin in fresh and wet sweet potato residue is the reason why fresh and wet sweet potato residue binds water and makes the sweet potato residue have a certain viscosity. Research shows that the pectin molecular chain binds components such as cellulose and hemicellulose that break the cell wall together through forces such as hydrogen bonds and van der Waals forces to form a stable porous network structure that intercepts most of the bound water.

[0003] Accordingly, in the experiment, by adding an "absorbent medium" to the fresh and wet sweet potato residue, the bound water intercepted by the porous network structure is adsorbed out, and the water distribution in the new system of the sweet potato residue is balanced, so that caking does not occur during the subsequent drying process. And dry sweet potato residue is rich in components with strong water absorption such as pectin, cellulose, and starch, and is itself an ideal "absorbent medium". In addition, if the finished sweet potato residue is applied to the feed industry, food by-products such as dry straw and dry peanut vines can also be used as absorbent media.

[0004] Based on the above, we propose a method for dehydrating fresh and wet sweet potato residue. Summary of the Invention

[0005] The purpose of the present invention is to solve the deficiencies existing in the prior art, and a method for dehydrating fresh and wet sweet potato residue is proposed.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A method for dehydrating fresh and wet sweet potato residue includes the following steps:

[0008] S1: Prepare fresh and wet sweet potato residue and an absorbent medium, and determine the compound mass ratio of the absorbent medium to the fresh and wet sweet potato residue based on the water content of the compounded sweet potato residue ≤ 60%;

[0009] S2: Pour the fresh and wet sweet potato residue and the absorbent medium into a stirring device according to the compound mass ratio, stir and mix evenly to obtain compounded sweet potato residue;

[0010] S3: Dry the obtained compounded sweet potato residue using a drum dryer until the water content drops to less than 10% to obtain finished sweet potato residue, and the dehydration is completed.

[0011] Preferably, the water-absorbing medium is dry sweet potato residue powder that has been dried in an oven at 60°C until the moisture content is 5%, taken out, coarsely pulverized, and passed through a 20-mesh sieve.

[0012] Preferably, the water-absorbing medium is dry straw powder or dry peanut vine powder that has been dried in a hot air drying oven until the moisture content is 5%, taken out, coarsely pulverized, and passed through a 20-mesh sieve.

[0013] A method for dehydrating fresh and wet sweet potato residue proposed by the present invention has the beneficial effects that for dehydrating fresh and wet sweet potato residue, first, the moisture contents of the water-absorbing medium and the fresh and wet sweet potato residue are measured. According to the moisture content of the compounded sweet potato residue not exceeding 60%, the compounding mass ratio of the water-absorbing medium and the fresh and wet sweet potato residue is calculated. The compounded sweet potato residue is dried using a drum dryer until the moisture content drops to within 10% to obtain the finished sweet potato residue. The entire process has a low cost, short time consumption, and low energy consumption, which is conducive to popularization. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a drying curve graph of the compound of different ratios of water-absorbing medium - fresh and wet sweet potato residue (taking the first group as an example).

[0015] Figure 2 It is a drying curve graph of fresh and wet sweet potato residue.

[0016] Figure 3 Drying rate curve of the compound of different ratios of water-absorbing medium - fresh and wet sweet potato residue (taking the first group as an example).

[0017] Figure 4 Drying rate curve graph of fresh and wet sweet potato residue. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0019] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0020] Example 1

[0021] A method for dehydrating fresh and wet sweet potato residue includes the following steps:

[0022] S1: Prepare fresh wet sweet potato residues and water-absorbing medium. Based on the moisture content of the compounded sweet potato residues ≤ 60%, determine the compounding mass ratio of the water-absorbing medium to the fresh wet sweet potato residues.

[0023] S2: Pour the fresh wet sweet potato residues and the water-absorbing medium into a stirring device according to the compounding mass ratio, stir and mix evenly to obtain compounded sweet potato residues.

[0024] S3: Dry the obtained compounded sweet potato residues using a drum dryer until the moisture content drops below 10% to obtain the finished sweet potato residues, and the dehydration is completed.

[0025] Example 1

[0026] Prepare fresh wet sweet potato residues and water-absorbing medium. If the dehydrated sweet potato residues are applied to the food industry and are required not to be mixed with other substances, that is, use dry sweet potato residues as the water-absorbing medium. Take an appropriate amount of fresh wet sweet potato residues, place them in an oven at 60°C, take them out when the moisture content reaches 5%, coarsely crush them, and pass through a 20-mesh sieve to obtain the water-absorbing medium.

[0027] If the finished sweet potato residues are applied to the feed industry, use feed additives such as dry straw and dry peanut vines as the water-absorbing medium. Take an appropriate amount of straw (cut into small sections) or peanut vines, place them in a hot air drying oven, take them out when the moisture content reaches 5%, coarsely crush them, and pass through a 20-mesh sieve to be used as the water-absorbing medium.

[0028] Furthermore, the fresh wet sweet potato residues are all taken from the sweet potato starch processing factory in Wulong District, Chongqing. One portion is taken from Yuhui Agricultural Development Co., Ltd., with a moisture content of 75.30%; the other portion is taken from Shanping Agricultural Development Co., Ltd., with a moisture content of 86.48%. The two groups of fresh wet sweet potato residues and the water-absorbing medium are compounded at mass ratios of 1:1, 1:1.4, 1:1.8, 1:2, 1:2.5, and 1:3 respectively, stirred and mixed evenly, balanced for 10 minutes, and the moisture contents of the compounded substances with different ratios are measured as shown in Table 1 below:

[0029] Table 1 Moisture contents of different ratios of water absorbing medium and wet sweet potato residues

[0030] Table 1 Moisture contents of different ratios of water absorbing medium and wet sweet potato residues

[0031]

[0032] Note: 1:3 means that the water-absorbing medium and the fresh wet sweet potato residues are compounded at a mass ratio of 1:3. The similar definitions apply to the right five columns. Different lowercase letters in the same column indicate significant differences (P < 0.05).

[0033] There was no significant difference in the moisture content of the water-absorbing media used in the two groups, and continuing hot air drying would not significantly reduce the moisture content of the water-absorbing media. This is because there is approximately 2% of constitutional water and immobilized water in the water-absorbing media, and this part of the moisture cannot be removed by hot air drying at 60°C.

[0034] The moisture content of the potato residue after the water-absorbing media and fresh wet potato residue were compounded at a mass ratio of 1:3 to 1:1 is shown in Table 1. It can be seen that there is no significant difference between the actual moisture content of the compounded potato residue and the theoretical moisture content calculated by proportion. Therefore, if you want to obtain compounded potato residue with a certain moisture content, only the moisture content of the water-absorbing media and fresh wet potato residue needs to be measured.

[0035] The fresh wet potato residue and different ratio compounds were separately packed in 150 mm disposable petri dishes of known mass, and the initial weights of the samples and petri dishes were measured. Then they were placed in an oven at 60°C for hot air drying, and the weight was measured every half hour until the weight basically no longer changed and then taken out.

[0036] Taking the drying time as the abscissa and the dry basis moisture content as the ordinate, a drying curve was plotted; taking the dry basis moisture content as the abscissa and the drying rate as the ordinate, a drying rate curve was plotted, as Figure 1 、 Figure 2

[0037] For Figure 1 、 Figure 2 The data was used for non-linear curve fitting of the variation law of the dry basis moisture content with the drying time, and the curve equation was obtained as: y = 135.20477 - 66.32601x + 8.44138x 2 , R 2 = 0.9999(1:3); y = 122.36696 - 60.61466x + 7.87655x 2 , R 2 = 0.99993(1:2.5); y = 106.98958 - 47.76156x + 5.51758x 2 , R 2 = 0.99979(1:2); y = 97.96862 - 50.71408x + 6.74511x 2 R 2 = 0.99952(1:1.8); y = 85.84448 - 41.16462x + 5.26422x 2 , R 2 = 0.99996(1:1.4); y = 64.78646 - 31.48403x + 4.09193x 2 , R 2= 0.9984 (1:1); y = 309.41674 - 90.00198x + 6.58756x 2 , R 2 = 0.99982 (fresh wet sweet potato residue). The R values of the seven curve equations 2 are all greater than 0.99, indicating that the model has a high degree of fitting to the data and can better explain and predict the changing trend of the data.

[0038] From Figure 2 and 3 , it can be seen that with the increase of time, the moisture content on dry basis first decreases rapidly and then slowly. The moisture evaporation during the hot air drying process is a gradually slowing process. The moisture in the different proportion compounding groups of the water-absorbing medium - fresh wet sweet potato residue reaches equilibrium at 3 h. Among them, the moisture content of the 1:1 compounding group can be reduced to 10% at 2 h, while the same amount of fresh wet sweet potato residue needs 6 h to reach the above drying standard. That is, compared with direct hot air drying (oven), the medium dehydration technology can save more than half of the time.

[0039] For the further 1:3 and 1:2.5 compounding groups, there is a small amount of agglomeration phenomenon for the dried sweet potato residue, but it can be easily dispersed with a little pinch. The sweet potato residue of the remaining compounding groups is in the form of scattered particles. If the moisture content of the compounded sweet potato residue exceeds 60%, the agglomeration phenomenon of the dried sweet potato residue is more serious, and the agglomerated sweet potato residue becomes hard and is not easy to rub into pieces. Therefore, the moisture content of the compounded sweet potato residue should not exceed 60%.

[0040] It can be known that based on the moisture content of the compounded sweet potato residue ≤ 60%, the compounding mass ratio of the water-absorbing medium and fresh wet sweet potato residue is determined.

[0041] Pour the fresh wet sweet potato residue and the water-absorbing medium into the stirring equipment according to the compounding mass ratio and stir evenly to obtain the compounded sweet potato residue.

[0042] The drying rate of the material depends on the surface vaporization rate and the diffusion rate of the internal moisture. Usually, the drying rate in the early stage of drying is controlled by the surface vaporization rate; then, as long as the external drying conditions remain unchanged, the drying rate and the surface temperature of the material will remain stable, and this stage is called the constant rate drying stage; when the moisture content of the material decreases to a certain extent, the diffusion rate of the internal moisture to the surface decreases and is less than the surface vaporization rate, the drying rate is mainly determined by the internal diffusion rate and continuously decreases with the decrease of the moisture content, and this stage is called the falling rate drying stage.

[0043] Refer to Figures 3 - 4, it can be seen that the drying rate curve of the 1:3 compounded potato residue has a similar changing trend to that of the fresh and wet sweet potato residue. As the moisture content on dry basis decreases, the drying rate first increases and then decreases; the drying rate curves of the 1:2 - 1:1 compounded potato residues have a similar changing trend. As the moisture content on dry basis decreases, there is a period of balance or increase in the drying rate, which is closely related to the initial moisture content of the compounded potato residue. The lower the initial moisture content, the lower the surface vaporization rate and the diffusion rate of internal moisture, that is, the lower the drying rate in the early stage of drying, which can be observed from the ordinate value at the highest point of the moisture content on dry basis in the figure. In addition, after the water absorption medium and the fresh and wet sweet potato residue are compounded in different ratios, the moisture distribution of the compounded potato residue is also different, which will also affect the drying rate of the compounded potato residue.

[0044] Based on Table 2 below

[0045] Table 2 List of 4 Dehydration Technologies for Sweet Potato Residue

[0046]

[0047]

[0048] It can be seen from Table 2 that in terms of the equipment cost of the technologies used, the "belt filter press + hot air drying" technology > the "centrifugation + hot air drying" technology > the "screw press + hot air drying" technology > the "medium dehydration + hot air drying" technology; in terms of energy consumption, the "screw press + hot air drying" technology > the "centrifugation + hot air drying" technology > the "belt filter press + hot air drying" technology > the "medium dehydration + hot air drying" technology; in terms of time consumption, the "screw press + hot air drying" technology > the "centrifugation + hot air drying" technology > the "belt filter press + hot air drying" technology > the "medium dehydration + hot air drying" technology. In summary, the medium dehydration technology for sweet potato residue has the lowest equipment cost, the lowest energy consumption, and the shortest time consumption.

[0049] Based on the above, since drum drying is a type of hot air drying and is more suitable for drying viscous substances, the obtained compounded sweet potato residue is dried using a drum dryer until the moisture content drops below 10%, obtaining the finished sweet potato residue, and the dehydration is completed.

[0050] In summary, for dehydrating fresh and wet sweet potato residue, first measure the moisture content of the water absorption medium and the fresh and wet sweet potato residue, calculate the compounded mass ratio of the water absorption medium and the fresh and wet sweet potato residue according to the fact that the moisture content of the compounded potato residue should not exceed 60%, dry the compounded sweet potato residue using a drum dryer until the moisture content drops below 10% appropriately, obtaining the finished sweet potato residue. Moreover, this method has low cost, short time consumption, and low energy consumption, which is conducive to promotion.

[0051] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A method for dehydrating fresh sweet potato residue, characterized in that: The steps include: S1: preparing fresh and wet sweet potato residue and a water absorbing medium, and determining a composite mass ratio of the water absorbing medium to the fresh and wet sweet potato residue based on the moisture content of the sweet potato residue after composite being ≤60%; S2: pouring the fresh wet sweet potato residue and the water absorbing medium into a stirring device based on the composite mass ratio and stirring and mixing them evenly to obtain composite sweet potato residue; S3: Dry the obtained composite sweet potato residue using a drum dryer until the moisture content drops to less than 10% (on a wet basis) to obtain a finished sweet potato residue, and dehydration is completed.

2. A method for dehydrating fresh sweet potato residue according to claim 1, characterized in that: The water absorbing medium is dry sweet potato residue powder which is dried in an oven at 60° C. to a moisture content of 5%, and then coarsely ground and passed through a 20-mesh sieve.

3. A method for dehydrating fresh sweet potato residue according to claim 1, characterized in that: The water absorbing medium is dry straw powder or dry peanut vine powder which is dried in a hot air drying oven to a moisture content of 5%, taken out and roughly ground to pass through a 20-mesh sieve.

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