Method for separating crude starch and purifying dried sweet potatoes through dry-process grinding

Abstract

The invention discloses a method for separating crude starch and purifying by grinding dried sweet potatoes by a dry method, which comprises the following steps: by taking the dried sweet potatoes with the moisture content of 16-20% as raw materials, carrying out multi-stage double-roller grinding and crushing and multi-stage screening to separate the crude starch and sweet potato residues, and washing and purifying the crude starch with a proper amount of water to obtain sweet potato starch. In the processing process, the water consumption is low, the obtained sweet potato starch can be used for producing food processing raw materials such as vermicelli and vermicelli, and the sweet potato residues can be used as high-fiber food processing raw materials.

Description

Technical Field

[0001] The invention belongs to the technical field of water-saving and environment-friendly sweet potato starch processing, and in particular relates to a method for separating and purifying crude starch by dry-rolling sweet potato stems. Background Art

[0002] Sweet potato is an important dryland food crop in my country, which plays an important role in ensuring food security. Starch processing is the most important use of sweet potato in my country. At present, the processing of sweet potato starch mainly adopts fresh potato with water hammer or file grinding to free starch particles from cells, and then a large amount of clean water is used to rinse the screen, and the starch particles are small and the potato residue (cell wall, crude fiber, etc.) particles are large, and the separation is carried out, and the starch is further precipitated and dried. There are also useful dried potatoes after rehydration and soaking, and the same method as fresh potatoes is used for production. This kind of method has the advantages of high efficiency and good starch purity, but the production process requires a large amount of clean water for cleaning and precipitation of starch, and the soluble components (sugar, protein, phenolic substances, etc.) in sweet potatoes are discharged with wastewater, causing environmental pollution. Although, existing environmental protection technologies can effectively treat these wastewaters and make resource utilization of sugars, proteins, etc. therein. However, since starch processing with fresh sweet potatoes as raw materials is usually completed within one month after harvest, a large amount of wastewater is generated in a short period of time. At the same time, the concentration of soluble components in the wastewater is low, resulting in extremely high costs for wastewater treatment or resource utilization, which is economically unaffordable for most small and medium-sized sweet potato starch processing plants. On the other hand, although the separated sweet potato residue is rich in dietary fiber, it has a water content of up to 70-90%, which makes it difficult to effectively utilize the huge output in a short period of time and often becomes one of the environmental pollutants.

[0003] The Chinese patent "Refined Starch from Dried Potatoes CN94110693.4" discloses a method of using dried potatoes as raw materials, soaking, grinding, washing and precipitation; "A potato flour vermicelli, rice noodle skin and its production method CN200710049518.4" discloses a method of producing vermicelli and rice noodle skin by mixing potato flour and starch in a certain proportion, but does not involve how to produce starch from dried potatoes. The dried potato starch production process involved in "Dried Potato Vermicelli Production Method CN00114676.9" is also a soaking, beating, washing and filtering method.

[0004] Therefore, it is urgent to study a method for dry separation of starch from sweet potatoes to reduce water consumption and reduce costs. Summary of the invention

[0005] The purpose of the present invention is to provide a method for separating crude starch from dried sweet potatoes by dry pressing and purifying the raw starch, in view of the shortcomings of large water consumption and high cost of treating or utilizing waste water and waste residue in the existing sweet potato starch production process of fresh potato or dried sweet potatoes, washing and precipitation.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] 1. A method for separating crude starch from dried sweet potatoes by dry rolling, comprising the following steps:

[0008] (1) Adjust the moisture content of the dried potatoes to 16-20%;

[0009] (2) rolling the dried potatoes in step 1 with a roller having a smooth surface and rotating at a constant speed;

[0010] (3) Repeat the rolling of the compacted material obtained in step 2 for 2-3 times;

[0011] (4) The rolled material obtained in step 3 is sieved with a 20-40 mesh screen, and the material on the screen is returned to step 2 and continued to be rolled until it can pass the screen;

[0012] (5) The material under the sieve in step 4 is sieved again with a 80-120 mesh sieve, the material on the sieve is potato residue, and the material under the sieve is crude starch.

[0013] Furthermore, the method for adjusting the moisture content of the dried potatoes to 16-20% is as follows: the dried potatoes are placed in a moisture regeneration chamber, and the relative humidity of the air is adjusted to 85%-95% by a humidifier, and the dried potatoes are placed until the moisture content of the dried potatoes reaches 16-20%.

[0014] Furthermore, the method also includes: utilizing the obtained potato residue as a raw material for processing high-fiber food.

[0015] 2. A method for purifying crude starch obtained by dry separation comprises the following steps:

[0016] (1) Add 2-4 times the weight of crude starch in water, stir evenly to form a slurry, and let stand for 0-4 hours;

[0017] (2) Using filter press or centrifugal treatment to remove most of the water from the slurry after standing;

[0018] (3) Repeat steps 1 and 2 1-2 times;

[0019] (4) drying to obtain purified sweet potato starch.

[0020] The beneficial effects of the present invention are:

[0021] 1. The quality of the sweet potato starch produced is equivalent to that produced by the traditional grinding and washing method, and can be used for processing starchy foods such as vermicelli and rice noodle wrappers;

[0022] 2. It uses less water and produces less wastewater, and the concentration of soluble components in the wastewater is high, which is conducive to resource utilization;

[0023] 3. Potato residue is in a dry state and can be directly used as a raw material for high-fiber food processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0025] Sweet potato tubers mainly contain fibrotic cells and storage cells rich in starch. The idea of ​​the present invention is to use smooth, equal-speed rollers to roll the dried potatoes with appropriate water content, avoiding the use of toothed, differential-speed rollers or other hammer mills, so as to achieve the effect of cell crushing and freeing the starch therein, avoiding the breakage and crushing of crude fibers and cell walls, thereby achieving the screening and separation of starch and potato residues. The separated crude starch contains soluble components such as sugar, protein, and minerals, which can be removed by washing with an appropriate amount of water. The specific steps are as follows: Figure 1 shown.

[0026] Embodiment 1:

[0027] 100 kg of dried potatoes with a moisture content of 13.1% were placed on a multi-layer mesh rack, put into a moisture regeneration room, and the relative humidity of the air was adjusted to 85%-95% with a humidifier. After 12 hours, the dried potatoes were taken out, and the moisture content of the dried potatoes was 16.0%, and the total weight was 103.5 kg. The dried potatoes were placed in a smooth, constant-speed roller roller mill and rolled for 3 times, and passed through a 20-mesh oscillating sieve to obtain 82.2 kg of undersize and 21.3 kg of oversize. The oversize was further rolled for 3 times, passed through a 20-mesh oscillating sieve to obtain 19.1 kg of undersize, and 2.2 kg of oversize was reserved for the next batch to be combined and processed, and the combined undersize was 101.3 kg.

[0028] The combined undersize material was further passed through a 120-mesh vibrating sieve to obtain 67.5 kg of undersize material, i.e., crude starch, and 33.8 kg of oversize material, i.e., potato residue.

[0029] Add 270 kg of clean water to 67.5 kg of crude starch, stir evenly, let it settle for 4 hours, put it into a filter press bag for filtration, add 135 kg of clean water to the residue, stir evenly, and put it into the filter press bag for filtration again.

[0030] After the filter residue was broken up and dried, 49.2 kg of purified dry starch was obtained. The extraction rate of purified starch from potato stems was 49.2% and the starch purity was 88.9%.

[0031] Embodiment 2:

[0032] 100 kg of dried potatoes with a moisture content of 13.3% were placed on a multi-layer mesh rack, put into a moisture regeneration room, and the relative humidity of the air was adjusted to 85%-95% with a humidifier. After 24 hours, the dried potatoes were taken out, and the moisture content was 19.9% ​​and the total weight was 108.7 kg. The dried potatoes were placed in a smooth, constant-speed roller roller mill and rolled for 4 times, and passed through a 40-mesh oscillating sieve to obtain 77.8 kg of undersize and 30.9 kg of oversize. The oversize was further rolled for 3 times, passed through a 40-mesh oscillating sieve to obtain 24.4 kg of undersize, and 6.5 kg of oversize was reserved for the next batch to be combined and processed, and the combined undersize was 102.2 kg.

[0033] The combined undersize material was further passed through a 120-mesh vibrating sieve to obtain 72.4 kg of undersize material, i.e., crude starch, and 29.8 kg of oversize material, i.e., potato residue.

[0034] Add 200 kg of clean water to 72.4 kg of crude starch, stir evenly, let it settle for 0.5 h, put it into a filter press bag for filtration, add 150 kg of clean water to the residue, stir evenly, and put it into the filter press bag for filtration again.

[0035] After the filter residue was broken up and dried, 50.3 kg of purified dry starch was obtained. The extraction rate of purified starch from potato stems was 50.3% and the starch purity was 88.7%.

[0036] Embodiment 3:

[0037] 100 kg of dried potatoes with a moisture content of 12.8% were placed on a multi-layer mesh rack, put into a moisture regeneration room, and the relative humidity of the air was adjusted to 85%-95% with a humidifier. After 15 hours, the dried potatoes were taken out, and the moisture content of the dried potatoes was 18.3%, and the total weight was 106.0 kg. The dried potatoes were placed in a smooth, constant-speed roller roller mill and rolled for 3 times, and passed through a 40-mesh oscillating sieve to obtain 71.4 kg of undersize and 34.6 kg of oversize. The oversize was further rolled for 3 times, passed through a 40-mesh oscillating sieve to obtain 26.4 kg of undersize, and 8.2 kg of oversize was reserved for the next batch to be combined and processed, and the combined undersize was 97.8 kg.

[0038] The combined undersize material was further passed through an 80-mesh oscillating sieve to obtain 82.3 kg of undersize material, i.e., crude starch, and 15.5 kg of oversize material, i.e., potato residue.

[0039] Add 164.4 kg of clean water to 82.3 kg of crude starch, stir evenly, and immediately put it into a centrifuge for dehydration. Add water, stir, and centrifuge for dehydration for a total of 3 times.

[0040] The solid material was taken out, broken up and dried to obtain 57.5 kg of purified dry starch. The extraction rate of purified starch from dried potato was 57.5% and the starch purity was 86.2%.

[0041] Embodiment 4:

[0042] 100 kg of dried potatoes with a moisture content of 13.4% were placed on a multi-layer mesh rack, put into a moisture regeneration room, and the relative humidity of the air was adjusted to 85%-95% with a humidifier. After 24 hours, the dried potatoes were taken out, and the moisture content of the dried potatoes was 20.0%, and the total weight was 108.7 kg. The dried potatoes were placed in a smooth, constant-speed roller roller mill and rolled for 3 times, and passed through a 40-mesh oscillating sieve to obtain 73.3 kg of undersize and 35.4 kg of oversize. The oversize was further rolled for 3 times, passed through a 40-mesh oscillating sieve to obtain 26.1 kg of undersize, and 9.3 kg of oversize was reserved for the next batch to be combined and processed, and the combined undersize was 99.4 kg.

[0043] The combined undersize material was further passed through a 100-mesh vibrating sieve to obtain 76.3 kg of undersize material, i.e., crude starch, and 23.1 kg of oversize material, i.e., potato residue.

[0044] Add 250 kg of clean water to 76.3 kg of crude starch, stir evenly, and immediately put it into a filter press bag for filtration. Add 200 kg of clean water to the residue, stir evenly, and put it into the filter press bag for filtration again.

[0045] After the filter residue was broken up and dried, 53.3 kg of purified dry starch was obtained. The extraction rate of purified starch from potato stems was 53.3% and the starch purity was 87.1%.

[0046] It should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Without making creative work, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims

1. A method for separating crude starch from dried sweet potatoes by dry rolling, characterized in that: The following steps are involved: The moisture content of the dried potatoes is adjusted to 16-20%; the dried potatoes are rolled with a roller having a smooth surface and rotating at a constant speed, and the rolling is repeated 2-3 times to obtain a rolled material; the rolled material is sieved with a 20-40 mesh screen to obtain a sieved material, and then sieved with an 80-120 mesh screen, the sieved material is potato residue, and the sieved material is crude starch.

2. The method according to claim 1, characterized in that The method further comprises: purifying the separated crude starch, comprising the following steps: Add clean water 2-4 times the weight of the crude starch, stir evenly to form a slurry, let it stand for 0-4 hours, dehydrate by filter pressing or centrifugation, repeat 1-2 times; dry to obtain purified sweet potato starch.

3. The method according to claim 1, characterized in that The material on the sieve obtained by screening with a 20-40 mesh screen is crushed with the next batch of materials.

4. The method according to claim 1, characterized in that: The method for adjusting the moisture content of the dried potatoes to 16-20% is as follows: the dried potatoes are placed in a moisture-reintroducing room, the relative humidity of the air is adjusted to 85%-95% by a humidifier, and the dried potatoes are placed until the moisture content of the dried potatoes reaches 16-20%.

5. The method according to claim 1, characterized in that The method further comprises: utilizing the obtained potato residue as a raw material for processing high-fiber food.

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