阅读说明：本技术 一种去除甜菜制糖稀汁己糖碱性降解色素的方法 (Method for removing alkaline degradation pigments of sugar beet sugar-making dilute juice hexose ) 是由 李文 郭丽云 程莉芸 骆文静 陆海勤 李凯 谢彩锋 杭方学 于 2020-05-26 设计创作，主要内容包括：一种去除甜菜制糖稀汁己糖碱性降解色素的方法,步骤如下：将甜菜稀汁与接枝季铵化磁性壳聚糖微球混合均匀,吸附稀汁色素；外施加电磁场,将吸附色素后的微球与稀汁分离；吸附色素后的微球依次采用氢氧化钠溶液及饱和食盐水浸泡后,用蒸馏水将其洗涤至中性,循环使用。所述的接枝季铵化磁性壳聚糖微球是以壳聚糖为原料、戊二醛为交联剂,通过悬浮交联聚合法包埋四氧化三铁纳米颗粒制作而成,再将壳聚糖分子链上的氨基进行接枝修饰,接枝可吸附稀汁色素的季铵基。本发明以天然无毒、环境友好的壳聚糖为原料制备糖用脱色剂,解决甜菜制糖过程因碳饱充生成己糖碱性降解色素,导致成品白砂糖色值高的技术问题,进一步提高成品白砂糖的品质。(A method for removing alkaline degradation pigments of sugar beet sugar-making dilute juice hexose comprises the following steps: uniformly mixing beet dilute juice and grafted quaternized magnetic chitosan microspheres, and adsorbing dilute juice pigment; externally applying an electromagnetic field to separate the microspheres adsorbed with the pigment from the dilute juice; after the microspheres absorbing the pigments are soaked in sodium hydroxide solution and saturated salt solution in sequence, the microspheres are washed to be neutral by distilled water and recycled. The grafted quaternized magnetic chitosan microsphere is prepared by embedding ferroferric oxide nanoparticles by a suspension crosslinking polymerization method by using chitosan as a raw material and glutaraldehyde as a crosslinking agent, and grafting amino groups on a chitosan molecular chain for modification so as to graft quaternary ammonium groups capable of adsorbing dilute juice pigments. The invention takes natural, non-toxic and environment-friendly chitosan as a raw material to prepare the decoloring agent for sugar, solves the technical problem of high color value of finished white granulated sugar due to hexose alkaline degradation pigment generated by carbon saturation in the beet sugar making process, and further improves the quality of the finished white granulated sugar.)

1. A method for removing hexose alkaline degradation pigments in beet sugar dilute juice is characterized by comprising the following steps:

(a) fully and uniformly mixing beet dilute juice and grafted quaternized magnetic chitosan microspheres in a dilute juice box according to the mass ratio of 30: 1-500: 1;

(b) after the reaction is finished, externally applying an electromagnetic field in a dilute juice box, and separating the grafted quaternized magnetic chitosan microspheres adsorbed with the pigments from the dilute juice to obtain decolorized dilute juice;

(c) evaporating and concentrating the decolorized dilute juice, and boiling and crystallizing to obtain white granulated sugar;

(d) and (3) sequentially and respectively soaking the grafted quaternized magnetic chitosan microspheres adsorbed with the pigments in a sodium hydroxide solution and a saturated saline solution, washing the soaked chitosan microspheres to be neutral by using distilled water, and recycling the washed chitosan microspheres.

2. The preparation method of the grafted quaternized magnetic chitosan microsphere of claim 1, characterized by comprising the following steps:

(1) uniformly mixing chitosan, acetic acid aqueous solution with the concentration of 1% -3% and ferroferric oxide nanoparticles according to the mass ratio of 1.0-1.5: 50-100: 0.2-0.5 to obtain chitosan-ferroferric oxide water-phase mixed solution;

(2) uniformly mixing the Sichuan disk 80 and the liquid paraffin according to the mass ratio of 2.0-6.0: 25-100 to obtain a Sichuan disk 80-liquid paraffin oil phase mixed solution;

(3) placing the Sichuan 80-liquid paraffin oil phase mixed solution into a reaction kettle, adjusting the stirring speed of a stirrer to be 200-300 revolutions per minute, and slowly dropwise adding the chitosan-ferroferric oxide water phase mixed solution with the same volume into the reaction kettle;

(4) after the temperature of the materials in the reaction kettle is raised to 40-50 ℃, adding 15-35% glutaraldehyde aqueous solution, wherein the addition amount of the glutaraldehyde aqueous solution is 3-8% of the total mass of oil-water two phases in the reaction kettle;

(5) after the stirring reaction of the materials in the reaction kettle is finished, an electromagnetic field is applied to the outside of the reaction kettle, magnetic chitosan microspheres with superparamagnetic property are collected, the microspheres are sequentially washed by petroleum ether, absolute ethyl alcohol and distilled water,

(6) freeze-drying the wet magnetic chitosan microspheres, and then vacuum-drying to constant weight;

(7) uniformly mixing the magnetic chitosan microspheres dried to constant weight, a sodium hydroxide solution with the concentration of 38-42% and isopropanol according to the mass ratio of 2.0-3.0: 5.7-8.6: 28-42, and slowly stirring for reaction at 45-50 ℃;

(8) slowly dropwise adding a 58-62% mass concentration 3-chloro-2-hydroxypropyl trimethyl ammonium chloride aqueous solution into the reaction liquid, wherein the dropwise adding amount is 35.56-53.33% of the mass of the reaction liquid, raising the reaction temperature to 68-72 ℃ after the dropwise adding is finished, and discharging after the reaction is finished;

(9) adjusting the pH of the reaction solution to be neutral by using dilute hydrochloric acid, and externally applying an electromagnetic field to collect a product, namely grafted quaternized magnetic chitosan;

(10) the obtained product grafted quaternized magnetic chitosan is repeatedly soaked and washed by methanol, washed by absolute ethyl alcohol and dried in a vacuum drying oven to constant weight.

3. The method for preparing in-situ quaternized magnetic chitosan microspheres of claim 2, wherein the degree of deacetylation of chitosan in step (1) is not less than 80%.

4. The method for preparing grafted quaternized magnetic chitosan microspheres of claim 2, wherein the stirrer in steps (3) and (5) is a paddle stirrer.

5. The method for preparing the grafted quaternized magnetic chitosan microsphere of claim 2, wherein in the step (6), the wet magnetic chitosan microsphere is frozen at-15 to-18 ℃ for 20 to 24 hours, and then dried in vacuum at 45 to 55 ℃ to constant weight.

Technical Field

The invention relates to a method for removing hexose alkaline degradation pigments in thin beet sugar-making juice, and belongs to the technical field of sugar-making engineering.

Background

In the production of beet sugar, most sugar-making businesses mainly use the traditional carbonic acid filling method to produce white granulated sugar in farmland, which mainly comprises four procedures of squeezing, cleaning, evaporating and crystallizing. In the cleaning of beet exudation juice, a large amount of lime milk is required to be added into the exudation juice, and carbon dioxide is charged to generate calcium carbonate to adsorb non-sugar impurities in the sugar juice, so as to achieve the purpose of clarification, and finally, a plate-and-frame filter press is adopted to filter and remove the generated calcium carbonate particles and suspended impurities in the sugar juice, so that the cleaner thin beet juice can be obtained. The color value of dilute juice is always a major concern in the sugar production process of beet, because it directly affects the color value of the finished white granulated sugar, and the color value of white granulated sugar is one of the important indexes for evaluating the quality of the white granulated sugar. During the clarification of the exuded juice, most of the pigments in the sugar juice are removed by the nascent calcium carbonate. However, carbonation needs to be performed under a strong alkaline condition (pH is 8.0-11.5), hexoses (mainly glucose and fructose) in the juice are very easily degraded into a large amount of alcohol, aldehyde, ketone and carboxylic acid compounds under the alkaline condition, and the alkaline hexose degradation products are very easily condensed into macromolecular colored substances under the alkaline condition and are remained in the dilute juice, so that the quality of the final finished sugar product is influenced. This class of macromolecular coloured materials, which are formed by the degradation and polymerization of hexoses under alkaline conditions, is commonly referred to in the sugar industry as hexose alkaline degradation pigments. Coca et al (Coca M, Garc i a M T, Mato S, Cart Lou n A, Gonz < lez G. evolution of color essence of juice essence degradation using styrenated colors [ J ]. Journal of food Engineering,2008,89: 429-434) found that more than 80% of the colored substances in the thin beet juice originated from hexose alkaline degradation pigments. Therefore, if a method can be developed to effectively remove the hexose alkaline degradation pigments in the dilute juice, the method has important significance for further improving the quality of the beet sugar.

The chitosan is a product of natural polysaccharide chitin with partial acetyl removed, and has the advantages of convenient raw material acquisition, low price, naturalness, no toxicity, environmental friendliness, strong thermal stability and the like. The chitosan molecular chain also contains a large amount of chemical reaction active groups, namely amino and hydroxyl, and the chitosan molecular chain can be chemically modified or modified to prepare materials with various functions, and is applied to various industries. Therefore, if chitosan can be subjected to directional chemical modification to prepare the adsorption decolorant for sugar according to the structural characteristics of the hexose basic degradation pigment, the adsorption decolorant has important practical significance for removing the hexose basic degradation pigment in the beet dilute juice. However, in the existing reports, no relevant literature is clear about the structural characteristics of hexose basic degradation pigments. In order to directionally modify chitosan to prepare a sugar decolorizing adsorbent for adsorbing and removing hexose alkaline degradation pigments in beet dilute juice, the patent inventor constructs a hexose degradation-polycondensation reaction model system in the carbon saturation process of beet exudation juice, obtains the hexose alkaline degradation pigments, and researches the unit structure characteristics of the hexose alkaline degradation pigments. FIG. 1 shows that hexose is alkaline to degrade pigments¹³C-NMR(D₂O), wherein the chemical shift of the graph is a broader absorption peak of 170-190 ppm, and the broader absorption peak is a characteristic absorption peak of ketone, aldehyde (or carbonyl), carboxyl and carboxylate; an absorption peak with a chemical shift of 90-130 ppm, which is mainly a characteristic absorption peak of a carbon-carbon double bond; an absorption peak with a chemical shift of 60-80 ppm, which is mainly specific to alcoholic hydroxylCharacterizing an absorption peak; the chemical shift is an absorption peak of 0-50 ppm, and is mainly a characteristic absorption peak of saturated alkane. In order to further clarify the structure of the carbon-carbon double bond in the hexose alkaline degradation pigment, the inventor also adopts the ultraviolet-visible spectrum to characterize the hexose alkaline degradation pigment, and the obtained result is shown in the attached figure 2. As shown in FIG. 2, the hexose basic degradation pigment has a strong absorption peak at a wavelength of 272nm, which indicates that the molecular chain of the hexose basic degradation pigment contains more conjugated double bonds. For further clarity¹³The chemical shift in C-NMR is the structural characteristic of a functional group at 170-190 ppm, the Zeta potential of the hexose alkaline degradation pigment is measured by the inventor by adopting a Zeta potentiometer and changes along with the pH value of a system where the hexose alkaline degradation pigment is located, and the obtained result is shown in an attached figure 3. As can be seen from fig. 3, the Zeta potential of the hexose alkaline degradation pigment shows a tendency to decrease as a whole with increasing pH. In addition, within the pH value range of 2-4, the Zeta potential of the hexose alkaline degradation pigment is in a sharp descending trend, and HADPs contain a large number of carboxyl groups or carboxylate radicals. FIG. 4 shows that hexose is alkaline to degrade pigments¹The H-NMR spectrum (with the solvent peak removed) does not show a peak for the carboxyl hydrogen, mainly because the sample is measured under neutral conditions (pH 7) where the carboxyl group is mainly present as carboxylate. As can also be seen from FIG. 4, the hexose basic degradation pigment also contains a small amount of aldehyde groups in the molecular structure.

The research shows that the hexose basic degradation pigment mainly comprises unit structures such as carboxyl (carboxylate), aldehyde, carbonyl, carbon-carbon (conjugated double bond), saturated alkane and the like. The formation of hexose alkaline degradation pigments is probably due to the fact that a large amount of aldehyde ketone compounds are generated when hexose is degraded under alkaline conditions; under alkaline conditions, the aldehyde ketone compounds are easy to generate aldol condensation reaction to generate products containing aldehyde groups and hydroxyl groups. The aldol condensation product is easy to dehydrate to generate olefine aldehyde, and the olefine aldehyde contains two unsaturated double bonds and is easy to be condensed to form a macromolecular compound. Under alkaline conditions, oxygen in the air can oxidize aldehyde groups at the tail ends of the macromolecular substances into carboxyl groups, however, not all aldehyde groups are oxidized into carboxyl groups, so that a small amount of aldehyde groups still exist in the hexose alkaline degradation pigments.

In the sugar industry, the processing of sugar juice is suitably carried out under neutral conditions, since this both avoids the conversion losses of sucrose under acidic conditions and prevents the degradation of monosaccharides (or hexoses) to pigments under alkaline conditions. Under neutral conditions, most of carboxyl groups in the hexose basic degradation pigment exist in a carboxylate radical in a negative charge form. Therefore, the hexose alkaline degradation pigments in the thin beet juice can be better adsorbed and removed only by preparing the chitosan into the adsorbent with the punctuation through directional modification.

Disclosure of Invention

The invention aims to provide a method for removing hexose alkaline degradation pigments in beet sugar making dilute juice, which solves the technical problem that the color value of finished white granulated sugar is higher due to the hexose alkaline degradation pigments generated by carbon saturation in the beet sugar making process, and further improves the quality of the finished white granulated sugar.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for removing hexose alkaline degradation pigments in beet sugar dilute juice comprises the following steps:

(a) mixing beet dilute juice and grafted quaternized magnetic chitosan microspheres in a mass ratio of 30: 1-500: 1 in a dilute juice box, and reacting for 0.5-2 h;

(b) applying an electromagnetic field to the dilute juice box, and separating the grafted quaternized magnetic chitosan microspheres adsorbed with the pigments from the dilute juice to obtain decolorized dilute juice;

(c) evaporating and concentrating the decolorized dilute juice, and boiling and crystallizing to obtain white granulated sugar;

(d) and (3) sequentially soaking the grafted quaternized magnetic chitosan microspheres adsorbed with the pigments in 0.8-1.2 mol/L sodium hydroxide solution and saturated salt solution for 8-12 h, washing the soaked chitosan microspheres to be neutral by using distilled water, and recycling the washed microspheres.

The preparation method of the grafted quaternized magnetic chitosan microsphere comprises the following steps:

(1) uniformly mixing chitosan, acetic acid aqueous solution with the concentration of 1% -3% and ferroferric oxide nanoparticles according to the mass ratio of 1.0-1.5: 50-100: 0.2-0.5 to obtain chitosan-ferroferric oxide water-phase mixed solution;

(2) uniformly mixing the Sichuan disk 80 and the liquid paraffin according to the mass ratio of 2.0-6.0: 25-100 to obtain a Sichuan disk 80-liquid paraffin oil phase mixed solution;

(3) placing the Sichuan 80-liquid paraffin oil phase mixed solution into a reaction kettle, adjusting the stirring speed of a stirrer to be 200-300 revolutions per minute, and slowly dropwise adding the chitosan-ferroferric oxide water phase mixed solution with the same volume into the reaction kettle;

(4) after the temperature of the materials in the reaction kettle is raised to 40-50 ℃, adding 15-35% glutaraldehyde aqueous solution, wherein the addition amount of the glutaraldehyde aqueous solution is 3-8% of the total mass of oil-water two phases in the reaction kettle;

(5) adjusting the stirring speed of a stirrer in a reaction kettle to 350-650 revolutions per minute, reacting for 2-4 hours, applying an electromagnetic field to the outside of the reaction kettle, collecting magnetic chitosan microspheres with superparamagnetic property, washing the microspheres for 3 times by respectively adopting petroleum ether, absolute ethyl alcohol and distilled water in turn,

(6) freezing the wet magnetic chitosan microspheres at-15 to-18 ℃ for 20 to 24 hours, and then drying the magnetic chitosan microspheres at 45 to 55 ℃ in vacuum to constant weight;

(7) uniformly mixing the magnetic chitosan microspheres dried to constant weight, a sodium hydroxide solution with the concentration of 38-42% and isopropanol according to the mass ratio of 2.0-3.0: 5.7-8.6: 28-42, and slowly stirring for reaction at 45-50 ℃ for 4-6 hours;

(8) slowly dropwise adding a 58-62% mass concentration 3-chloro-2-hydroxypropyl trimethyl ammonium chloride aqueous solution into the reaction liquid, wherein the dropwise adding amount is 35.56-53.33% of the mass of the reaction liquid, raising the reaction temperature to 68-72 ℃ after the dropwise adding is finished, reacting for 6-8 hours, and discharging;

(9) adjusting the pH of the reaction solution to be neutral by using dilute hydrochloric acid, and externally applying an electromagnetic field to collect a product, namely grafted quaternized magnetic chitosan;

(10) the obtained product grafted quaternized magnetic chitosan is repeatedly soaked and washed by methanol for 3 times, then washed by absolute ethyl alcohol for 3 times, and dried in a vacuum drying oven to constant weight.

The deacetylation degree of the chitosan in the step (1) is not less than 80%.

The stirrer in the steps (3) and (5) is a paddle stirrer.

The reaction process is as follows: chitosan is dissolved into a water phase under the action of acetic acid, ferroferric oxide nano particles are dispersed into the water phase containing chitosan under the condition of continuous stirring to form a suspension, and the chitosan microspheres can be promoted to form spheres by the Sichuan 80-liquid paraffin oil phase mixed solution. Increasing the temperature of the oil phase mixed solution to accelerate the reaction rate, adding glutaraldehyde to connect single chitosan molecules into a cross-linked sphere, carrying out cross-linking reaction on amino groups on the chitosan and the glutaraldehyde, wrapping a magnet in the cross-linked sphere in the cross-linked process to obtain a magnetic chitosan microsphere with superparamagnetic property, and washing and removing unreacted reactants by adopting petroleum ether, absolute ethyl alcohol and distilled water. The freeze-drying process enables the interior of the chitosan to form a porous structure, and the adsorption performance is enhanced. And (6) preparing a grafting reaction condition by using a sodium hydroxide solution and isopropanol, and (7) grafting a quaternary ammonium group onto the magnetic chitosan microsphere by using 3-chloro-2-hydroxypropyl trimethyl ammonium chloride. And after the reaction of the grafted quaternary ammonium group is finished, externally applying an electromagnetic field to collect the grafted quaternized magnetic chitosan, and finally washing, drying and storing to obtain the grafted quaternized magnetic chitosan.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention directionally modifies chitosan based on the structural characteristics of hexose alkaline degradation pigments in thin beet juice, prepares sugar, adsorbs and removes the hexose alkaline degradation pigments in the thin beet juice by using a decolorizing agent, solves the technical problem that the color value of finished white granulated sugar is higher due to the hexose alkaline degradation pigments generated by carbon saturation in the sugar preparation process of beet, and further improves the quality of the finished white granulated sugar.

(2) In the prior art, styrene (divinylbenzene) type anion exchange resin also has certain adsorption removal effect on hexose basic degradation pigments in beet dilute juice. However, both styrene and divinylbenzene have been classified as 2B carcinogens by the world health organization international cancer research institution and are extremely harmful to human bodies. And the styrene and the divinylbenzene are both from petroleum, so that the raw materials can not be regenerated and are difficult to degrade, and the environmental pollution is serious. With the continuous increase of economy, the continuous reduction of petroleum reserves and the continuous increase of price, the cost of petroleum-based materials is increased year by year, and great restriction is also caused to the development of the petroleum-based materials. The chitosan is a natural and renewable resource substance, compared with styrene-based anion resin, the invention takes the chitosan as the raw material to prepare the decoloring agent for sugar to adsorb and remove hexose alkaline degradation pigment in the beet dilute juice, and has the advantages of convenient acquisition of raw materials, low price, natural non-toxicity, environmental protection and the like.

(3) The chitosan-based sugar is made into microspheres by using the decolorizing agent, compared with the existing amorphous adsorbent, the microsphere has larger specific surface area and can provide more adsorption sites, so that the adsorbent is easy to fully contact with pigment in the beet dilute juice and carry out adsorption reaction to realize decolorization.

(4) The existing adsorbent (such as activated carbon) is usually an amorphous adsorbent, and after the adsorption reaction is finished, a plate-and-frame filter press is required to separate the adsorbent from the adsorbate. The adsorbent is made into microspheres and endowed with superparamagnetism, and the microspheres and the cane juice can be quickly separated by applying an electromagnetic field after the adsorbent adsorbs pigments in the beet dilute juice, so that the method has the advantages of compact equipment structure, high separation efficiency, high yield, few auxiliary equipment and the like.

Drawings

FIG. 1 shows the degradation of pigments by hexose bases¹³C-NMR(D₂O) diagram.

FIG. 2 shows the degradation of pigments by hexose bases¹H-NMR(D₂O) diagram.

FIG. 3 is a UV-Vis spectrum of hexose basic degradation pigment.

FIG. 4 shows the effect of pH on Zeta potential of aqueous hexose alkaline degradation pigments.

FIG. 5 is a scanning electron microscope micrograph of the grafted quaternized magnetic chitosan prepared in example 1.

Detailed Description

The technical solution of the present invention is further illustrated by the following examples.