Study on flour processing Technology mechanical separation in food processing under the New situation
This paper analyzes the flour processing technology from three aspects: cleaning section, milling section and blending section in the process of flour processing, and puts forward the adjustment method of flour processing technology in order to produce flour with stable quality and strong adaptability. improve the added value of flour.
Key words: flour; processing technology; production equipment
With the development of the times, the increasing national wealth and the change of career intention, the manufacturing industry, such as flour processing enterprises and downstream flour end customers (users) are faced with the problem of difficult employment. In addition, the rise in rent, labor costs and other costs has led to the continuous compression of the profit space of flour processing enterprises, and even losses. Therefore, it is comic relief 2017 urgent to improve the profitability of flour processing enterprises. Increasing the added value of flour and reducing labor costs can greatly increase the profitability of enterprises. This requires more advanced flour processing technology, which can not only reduce the number of operators, but also reduce the skill requirements of operators, and produce flour with stable quality and strong adaptability. This paper analyzes the process from three aspects: cleaning section, milling section and blending section in the process of flour processing.
1 cleaning section
1.1 the setting of the cleaning screen the first layer of the raw grain cleaning screen (vibrating screen, rotary vibrating screen) has dropped more than 90% of the wheat in 4 places. The material falls too fast, the material flow moves in the vertical direction, the strap is mixed and stands up (the wheat orange how to calculate mesh size to micron rod is slender), and passes through the sieve hole along the material flow; the material layer of the lower sieve surface is too thick, the vibration effect of the material is poor, the automatic classification effect is not good, and the perforation opportunity of fine material is less, the screening effect is poor. Based on this, the cleaning screen is improved by the following methods.
The main results are as follows: (1) the sieve hole of Φ 5.5 mm (traditionally larger than Φ 6.5 mm) is used in the front section, which reduces the blanking speed, the falling speed of the material is slow, the movement trajectory is mainly horizontal movement, and the large impurity moves along the horizontal direction, so it is not easy to perforate, which can improve the separation effect of large impurity. Due to the reduction of the screen hole in the front section of the upper screen surface and the slow blanking speed, the material layer in the front section of the lower screen surface becomes thinner, the material is easy to vibrate, cocoa powder production the automatic classification effect is good, and the effect of separating small impurities on the lower sieve surface is improved. Under the action of automatic classification, the small particles pass through preferentially in the front part of the upper screen surface, and almost all the small particles pass through the middle part of the upper screen surface, and the thickness of the material layer under the screen almost does not affect the separation effect of small impurities.
(2) the tail section of the upper screen and the bottom of the large miscellaneous aggregate trough are replaced by braided screen. After encrypting the upper sieve surface, a small amount of large-grain and round-grain wheat will pop out. The braided sieve has a high perforation rate and can recover wheat from large miscellaneous materials. After the first layer screen in the early cleaning process section, the series plane rotary screen can further pick out the wheat from the large impurities and solve the problem of running wheat on the screen.
(3) the selection of a combined cleaning screen and a horizontal suction duct to remove 90% impurities in the initial cleaning section can solve the problems of poor quality of wheat at the bottom of the warehouse caused by automatic classification and the instability of the cleaning process section. It is especially beneficial to the equipment which is very sensitive to wheat flow, such as stone remover, automatic water feeder and so on.
1.2 setting of graded specific gravity stone removal machine
The graded specific gravity stone removal machine is the most difficult equipment to adjust in the cleaning section. If the material flow on the grading screen is too small, the stone removal effect is poor, the removal of light impurities is not clean, and the material flow on the screen is too large, which contains wheat. As shown in figure 1, the small classifier is connected in series on the grading screen to screen out the wheat; at the stone mouth, the small stone remover is connected in series to screen the wheat from the pebbles, and the stable stone removal and classification effect can be achieved.
Fig. 1 schematic diagram of classifier in series
1.3 use of color sorter
Color sorter is a kind of equipment which uses photoelectric detection technology to automatically sort out the discolored particles in granular materials according to the differences of optical properties of materials. With its ultra-clear color micron camera and advanced targeting technology, the impurity center can be accurately located, the micro-color difference recognition ability is excellent, and all kinds of micro-color difference impurities can be easily removed, such as pebbles, cinder, disease spot mildew, a large number of grains, wheat knots, scab diseased grains and weed seeds, etc.
1.4 using secondary wheat moistening
The time of grinding moisture and moistening wheat has a great influence on the milling process and quality, and the time of one wheat moistening is generally more than 24 hours. The setting of moistening wheat moisture should fully take into account the weather conditions of the next day and make appropriate adjustments. This requires higher experience of production personnel, as well as high requirements for hydraulic skills and sense of responsibility. The use of secondary wheat moistening can better meet the requirements of ground wheat, especially the processing of high hardness wheat in cold weather. The second wheat moistening usually takes only about 6 hours, so the adjustment is flexible and the skill requirement for hydraulic engineering is reduced.
In addition, the moisture on the surface of wheat will be lost to varying degrees in the process of secondary cleaning. When the wheat after secondary cleaning goes directly into the milling process, the wheat skin is dry and fragile, which can be reduced by spraying and adding water, but it will increase the difficulty of peeling and scraping. If you enter the warehouse after the second cleaning, the moisture can spread from the inside of the wheat to the cortex, and then the core of the flour section can be separated more easily. In addition, if there is more water added to the wheat at one time, there will be different degrees of water infiltration. Through the second moistening of wheat, the redistribution of water in wheat can not only slow down the infiltration of water, but also solve the problem of more water absorption of soft wheat and less water absorption of durum wheat.
1.5 using secondary wheat blending
The use of secondary wheat blending can slow down the automatic classification of wheat caused by impurity, ensure the stable flow and quality of wheat out of the warehouse, reduce the range of cleaning equipment that needs to be adjusted, and the cleaning equipment is easier to operate. At the same time, the cleaning process can be separated from the water process, and the wheat moistening time can be set arbitrarily.
2 milling section
2.1 Pretreatment of ground wheat
Wheat pretreatment can instantly make the wet wheat pass through the drum at 90 ℃, which can not only kill the fungi on the wheat surface and in the groin, but also improve the toughness of the cortex. Reduce the fermentation instability of dough caused by miscellaneous bacteria infection and sprouting, germination and immature wheat. Flour has stronger adaptability in extreme environment and adapts to factory assembly line processing.
2.2 cushioning process of pre-stripping and scraping multi-slag mill
Before entering the mill, the pre-ground smooth roller is used to squeeze and knead the wheat, which makes the interior of the wheat crack and soften. The softer the wheat is, the smaller the change is, and the harder the wheat is, the greater the change is. The ideal state of wheat in the seed-breaking stage is gradual extrusion pressure, so that the ground material has large sheet shape and uniform particles. If the wheat entering the grinding zone has high hardness and smooth surface, the grain in the grinding zone will slide along the inclination of the grinding teeth, cushioning off part of the extrusion pressure, and then have a sudden impact force, resulting in greater damage. The pre-ground lower roll peels off the wheat and separates the impurities in the grooves. The stripping rate of the first three mills in the milling process is the most important operation index in the inter-flour operation, which affects the material distribution of the whole system and has a great influence on the flour quality. It is generally required to adjust in time with the changes of raw materials, climate, product structure, grinding state and other factors, and the allowable range of adjustment is very small. The higher the scraping rate is, the higher the flour extraction rate is, but the flour extraction rate of leather mill is high, the extensibility of front flour is poor, the rate of high grade flour is low, and the dough of middle and rear road flour is stiff. If the moisture content of the ground wheat is high and the raw grain is soft, the grain under the skin mill is small, while the moisture content of the ground wheat is low, the climate is dry, and the raw grain is hard.
Grind off the big particles. The incoming flow of the powder cleaner is dynamic, so it is necessary to adjust the air volume and screen number in time, which requires high requirements for operators.
The traditional critical scraping rate 1B (1 skin) is about 22% (2 skin) about 38%. In order to ensure the rate, the general peeling rate is slightly higher than the critical point. The higher the stripping rate is, the smaller the particle size is. When the stripping rate exceeds the critical point, the material distribution changes due to the change of particle size, and the change of core abrasive layer leads to the change of flour particle size, which leads to the change of dough water absorption process.
Pre-stripping and scraping expands the wheat grain, the critical point of 1B (1 skin) stripping rate can be increased to 38%, and the tightness of mill spacing has little effect on the grinding particle size; because 1B (1 skin) increases the stripping rate, 2B (2 skin) can meet the requirement of flour extraction rate within the critical stripping rate. In this way, the rolling distance of 1B (1 skin) and 2B (2 skin) mill is looser and tighter, and the operation of leather mill becomes easier.
Usually adjust the powder machine to the material in the lower part of the screen, choose between entering the slag mill or entering the center mill, and strive to balance between the rate and quality. Now the multi-slag grinding process is adopted, the material of 1s (1 slag) goes into 1m (1 core), the material of 2s (2 slag) goes into 2m (2 core), and the material of 3s (3 slag) enters 3M (3 core) after treatment. Materials with poor glossiness are preferred to enter the slag mill, which basically does not affect the recovery rate. The operation of the cleaner becomes easier, as shown in figure 2.
Note: 3P1 (3 clear 1), 2s P (2 slag clear).
Fig. 2 configuration diagram of multi-slag grinder
Materials with different characteristics enter different slag mills, and the particles can be separated by lower powder extraction. The operation of the slag mill and its corresponding cleaning machine has also become easier.
The relative scraping rates of 1B (1 skin) and 2B (2 skin) are basically the same. The materials of 1B (1 skin) and 2B (2 skin) are cleaned separately and ground separately. As shown in figure 3, the heart of 1B (1 skin) is hard and yellowing, and the heart of 2B (2 skin) is soft and white, which is treated separately, the cleaning machine is easy to adjust, and the mill is also easy to adjust. If the hardness difference of the incoming material is too big, the soft material is over-ground, the damaged starch is high; the hard material is impenetrable and the time is too long, the dough is stiff in the early stage and sticky in the later stage. The core materials with different processing and quality characteristics are put into the corresponding core mill, the hard material is tightly ground, the dough has better water absorption, better softness, and the formation time is shortened.
Note: 1Bc (1 skin thick), 2Bc (2 skin thick), 1P1 (1 clear 1), 1P2 (1 clear 2), 2P1 (2 clear 1), 2P2 (2 clear 2).
Fig. 3 configuration diagram of high square screen and powder cleaner for pre-grinding process 1B and 2B
2.3 appropriate use of 8-roll mill
The more endosperm on the cortex, the more brittle and fragile the material is. If the eight-roll mill is used, the upper roll peels off part of the endosperm, the material becomes soft and tough, and the grinding material of the lower roll will have good shape and uniform particles, so that there is a higher scraping rate and less powder.
The incoming material of slag mill and fine skin mill generally contains the slag with skin core, the hard core side squeezes the skin side, and the material is sticky and black after grinding. The upper roll of the eight-roll mill is used to separate the skin and the core, and the lower roll is used to break the particles, so that the leather material is less damaged and the core material has good gloss. The upper roll of the eight-roll core mill grinds the small particle size, and preheat and soften the material, and the particle of the lower roll is more uniform. In addition, the eight-roll mill is easier to operate than the four-roll mill, the extrusion pressure is smaller, and the grinding roller wear is slower.
2.4 Secondary powder extraction
For the pure core material with large particle size, due to the different internal composition of the particles, the processing characteristics are also different, which makes the dough sticky and the dough inelastic. In this regard, we can appropriately increase the flow rate, buffer hard impact, soft material first take powder, through sieving, clear powder after heavy pressure hard material. In this way, the flour particles are uniform, the water absorption speed is fast, and the dough formation time is short. After the secondary powder is taken, the rolling distance of the loose mill will not reduce the rate, and the rolling distance of the compact mill will not increase the damaged starch, so the operation is simple.
2.5 extraction technology of germ
The germ extraction site is generally 1s (1 slag and) 1T (1 tail), considering the loose operation of the slag grinding system, therefore, at present, the germ extraction part is generally concentrated on 1T (1 tail) pressed into pieces and extracted, 1T (1 tail) incoming material only contains germ and bran slices, does not contain slag, core, tight mill distance, will not reduce the poor quality of 1T (1 tail) flour.
2.6 Air separation process between powders
The powder remover can purify the core material, but it is not good at handling the light throwing material. The light material is suitable for air separation. If the light material is removed by pre-air selection, the remaining materials have good fluidity. Therefore, after the cleaning machine is equipped with air separation, the cleaning machine can be adjusted better.
(3) flour blending section
The co-production process can mix powder horizontally and must have all the powder mouths. although some powder mouths have a negative impact on the quality, they can not be discarded. The multi-base powder blending process can mix powder longitudinally, concentrate the powder with similar quality characteristics, and select the powder that can achieve specific functional requirements according to the needs. Such as high water absorption to do fermented food, low water absorption to do non-fermented food, boiling resistance, foam resistance, good taste; leather characteristics of the material purification into the front, improve extensibility, to make up for the middle powder stiff defect. The higher the unit yield (the more perfect the milling process of daily treatment of wheat is more than 800 tons, and the most perfect of the process of daily treatment of wheat is 1 600 tons), the more varieties of base flour, the easier the characteristics are subdivided, the more flexible the product structure is, and the higher the added value is.
(4) improve the adaptability of the product
Flour end-users have the problems of difficult employment, high rent and high cost of water and electricity, so they are more inclined to choose flour with high adaptability and easy mechanization.
The gluten strength of flour is used for mixing, pressing, molding and fermentation. If the water absorption rate of flour particles is the same and the flour and water are mixed evenly, the mixing and pressing time can be shortened, more gluten strength can be reserved for molding and fermentation, the processing cycle of flour products can be shortened, and the requirement for the quality of raw grain can be reduced.
The softer the flour particles are, the faster the water absorption speed is; the harder the flour particles are, the slower the water absorption speed is. In the conventional flour processing process, soft particles are often ground finer than hard particles. When using this kind of flour and dough with large differences between soft and hard particles, because the soft particles absorb water faster, which is equivalent to dough and soft, the dough is stiff at the beginning, sticky at the later stage, long processing cycle and poor dough strength. Therefore, the particle size, softness and hardness of the core material should be as close as possible, and secondary powder extraction should be used for large particles. When selecting the cleaner, pay attention to the classification function of the cleaner, light grinding soft material, heavy pressure hard material; the speed of the mill is high when the soft material is grinded, and the speed of the mill is low when the hard material is grinded.
The flour processing process is relatively complex and there are many nodes, so there is still a lot of room for flour processing technology research. Through the more fine process adjustment of the cleaning section, the milling section and the flour blending section, especially the multi-base flour blending process, not only the diversified flour can be produced, but also the flour which is simple and easy to operate can be processed, which can improve the added value of the flour.
Article source: grain circulation
Author: Liu Ruiqing, Zhengzhou Jiuyi Food Engineering Co., Ltd.
Pay attention to Douyin account of "Grain and Oil Marketing Branch"
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