A progressive extraction method and device for citrus peel

Abstract

The invention discloses a citrus peel progressive extraction method and a device thereof. Citrus peel essential oil and citrus core can be recovered by pretreating and progressively extracting the citrus peel. In the process of progressive extraction of the citrus peel, high value-added products such as citrus peel infusion syrup, hesperidin, pectin, dietary fiber, etc. can be obtained in sequence, which has extremely important economic value. The method and the device of the invention can sequentially complete the extraction of citrus infusion syrup, hesperidin, pectin and purification of dietary fiber raw materials without transferring the citrus peel, transforming the traditional complicated extraction operation into a simplified, systematic and continuous operation, greatly improving labor efficiency and reducing material and power consumption. The invention adopts a secondary or tertiary extraction phase process, greatly improving the concentration of the extract in the extract, improving the product recovery rate, and truly realizing the full utilization of the citrus peel, thus expanding extremely important new resources for the development of the food processing industry.

Description

Technical Field

[0001] The invention relates to the technical field of fruit peel recovery and extraction, in particular to a citrus peel progressive extraction method and a device thereof. Background Art

[0002] my country ranks first in the world in terms of citrus planting area and production. However, the processing utilization rate of citrus is only 8% to 9% and less than 10%, and its utilization rate is even lower in citrus juice processing. At present, China has a citrus juice consumption market with a population of 1.4 billion, and the total consumption is rising year by year. About 80,000 to 100,000 tons of citrus juice are imported each year. So what is the reason for the large production of citrus fruits but the low processing utilization rate of citrus? The demand for citrus juice consumption market is large, but it has to rely on imports.

[0003] There are four main reasons: First, juice processing enterprises do not have the ability to build citrus orchard raw material bases. Faced with the high price of citrus raw materials, the manufacturing cost of citrus juice processing products is unbalanced with the input cost of product manufacturing; second, the non-standardized orchard citrus raw materials purchased on the market are difficult to meet the product technical requirements, resulting in unstable product quality and failure to form an influence in the market; third, due to the insufficient supply of citrus raw materials, the citrus juice processing cycle is short, which seriously restricts enterprises from achieving large-scale production; fourth, the industrial structure is unreasonable and the processed products are single, so enterprises have no room for maneuver in the face of market changes. Due to the above reasons, citrus juice processing enterprises that do not have economic strength or unreasonable industrial structure can only be trapped in difficulties for a long time, or even forced to stop production and disintegrate. Summary of the invention

[0004] In order to solve the problems in the above-mentioned background technology, the present invention provides a method and a device for the progressive extraction of citrus peels. By pretreating the citrus peels, citrus peel essential oil and citrus cores can be recovered. In the progressive extraction process of citrus peels, the extraction operations of substances with higher value in the citrus peels are connected, and citrus infusion syrup, hesperidin, pectin and dietary fiber products can be obtained in sequence, which have extremely important economic value.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a method for progressive extraction of citrus peels, by progressively extracting citrus peels, citrus infusion syrup, hesperidin, pectin and dietary fiber products are obtained in sequence, and the specific process steps of progressive extraction of citrus peels are as follows:

[0006] A. Pretreatment of citrus peels: Take the citrus peels after juicing, crush them into particles with a size of 10-18 mm, spray softened water into the citrus peels while crushing them, and the crushed citrus peels become peel pulp, which is then transported to three extraction tanks respectively; spraying softened water while crushing is beneficial to the crushing operation of the citrus peels and helps to improve the fluidity of the peel pulp;

[0007] B. Extracting citrus infusion syrup: add 2-3 times (by weight) of softened water to the first extraction tank, immerse the peel pulp completely in the softened water, and let it stand for 20 minutes; transfer the extract in the first extraction tank to the second extraction tank, and let it stand for 20 minutes to extract the peel pulp; transfer the extract in the second extraction tank to the third extraction tank, and let it stand for 20 minutes to extract the peel pulp; collect the extract in the third extraction tank, filter it with a 120-160 mesh filter screen, remove the impurities of the peel and pulp suspended in the extract, and obtain the citrus peel water-washed sugar solution;

[0008] The citrus peel water-washed sugar liquid is pasteurized by a plate heat exchanger at a sterilization temperature of 90 to 93° C. and a sterilization time of 15 to 20 seconds. The outlet temperature of the citrus peel water-washed sugar liquid is controlled to be between 50° C. and 55° C., 0.03% to 0.06% (by weight) of activated carbon is added to the citrus peel water-washed sugar liquid for decolorization, and pectinase is added at the same time. The pectinase is obtained by dissolving pectinase solid in 5 times softened water in advance, and the temperature is maintained at 50° C. to 55° C. and the enzymolysis time is 40 to 60 minutes to decompose the pectin in the citrus peel water-washed sugar liquid; the enzymolysis is stopped when the pectin enzymolysis test is negative; when the enzymolysis reaches the end point, the suspended matter in the citrus peel water-washed sugar liquid is mutually adsorbed and flocculated, and a precipitate is formed and settled at the bottom, and the citrus peel water-washed sugar liquid is clarified;

[0009] The supernatant of the citrus peel water-washed sugar solution after enzymatic hydrolysis is taken out, and the suspended pulp and high molecular polymer therein are separated by an ultrafiltration device, the pore size of the ultrafiltration membrane core is 1-50 nm, the temperature is 50° C.-55° C., the operating pressure is 0.50-0.56 MPa, and the ultrafiltration liquid circulation volume is 8-12 times the ultrafiltration separation capacity, wherein water and monosaccharides, disaccharides, and organic acid soluble solids pass through the ultrafiltration membrane, and the transparent ultrafiltration permeate is collected, and then it is concentrated to soluble solids 70.0-70.5 Brix by a low-temperature vacuum evaporator to obtain a clear citrus infusion syrup;

[0010] In this step B, the viscosity of the citrus water-washed sugar solution is reduced by pectinase enzymolysis treatment, so that its fluidity is effectively improved to adapt to the subsequent concentration operation of the low-temperature vacuum falling film evaporator, so as to obtain a citrus infusion syrup with a soluble solid content of 70.0-70.5 Brix, which improves the safety of product storage, greatly reduces packaging, saves storage space, and reduces logistics costs; the activated carbon adsorption decolorization combined with ultrafiltration process is used to make the water-washed sugar solution clear and transparent, and the peel water-washed sugar solution is converted into an edible citrus peel infusion sugar solution, which greatly improves the added value of the product. In this step B, softened water is used to wash the residual sugar in the citrus peel to obtain the citrus peel infusion sugar solution; the citrus peel is effectively removed by water washing and leaching, and the impurities such as soluble solids, pigments, organic acids and aromatic substances in the citrus peel are conducive to the purification of the subsequent extraction product. At the same time, the low-temperature extraction can ensure that the structure of the citrus peel does not change significantly during the operation of step B, thereby ensuring the smooth progress of the subsequent extraction.

[0011] C. Extraction of hesperidin by primary enzymatic hydrolysis: After the sugar solution is extracted in step B, softened water of 2 to 3 times (by weight) of the peel pulp is added to the three extraction tanks respectively, and then 0.01% to 0.03% (by weight) of cellulase is added to the peel pulp. Before adding the cellulase, the cellulase is diluted and dissolved into a cellulase solution with softened water of 5 times (by weight) of the cellulase. The extract in the extraction tank is circulated and heated by a plate heat exchanger, and the cellulase solution and the extract are fully mixed at the same time. When the extract reaches 40° C. to 50° C., the circulation is stopped, and the enzymatic hydrolysis is allowed to stand for 3 to 4 hours. The extract is separated from the three extraction tanks to obtain a primary hesperidin extract;

[0012] In step C, the hydrolysis of cellulase is used to change the cell structure of citrus peel tissue, so that the hesperidin in the peel cells is released, and a higher extraction rate can be obtained;

[0013] D. Secondary hot water continuous extraction of hesperidin: After completing the bioenzymatic extraction of hesperidin in step C, add softened water twice (by weight) of the peel pulp into the first extraction tank, heat to 90° C. using a plate heat exchanger, and extract for 20 minutes, transfer the hot water extract in the first extraction tank to the second extraction tank, control the temperature at 85° C. in the second extraction tank, and extract for 20 minutes, then transfer the extract in the second extraction tank to the third extraction tank, control the temperature at 85° C., and extract for 20 minutes, separate the extract to obtain a third hesperidin hot water extract, mix the third hesperidin hot water extract with the first hesperidin extract extracted by the bioenzymatic method in step C, and obtain a hesperidin extraction mixture;

[0014] The hesperidin extraction mixed solution is filtered through a diatomaceous earth filter to remove insoluble impurities therein, and then concentrated using a low-temperature vacuum evaporator to evaporate 70% to 80% of water with a concentration ratio of 3:1 to 5:1 times, and the concentrated solution is cooled to 0 to 3° C. and allowed to stand for 10 hours to allow hesperidin to crystallize;

[0015] The hesperidin crystals are taken out and washed with water, then dissolved with 20 times (by weight) of 1% food-grade sodium hydroxide solution, and filtered with a 200-mesh filter screen; the pH value is adjusted to 10 with a food-grade acidic pH regulator, and then carbon dioxide gas is introduced to reprecipitate the hesperidin to obtain a hesperidin extract; the hesperidin extract is dehydrated by filtering with a filter press, and then dried with hot air at a temperature of 70° C. to 80° C. until the water content is less than 5%, and the hesperidin product is obtained after crushing;

[0016] In this step D, cellulase is first used to extract hesperidin, and then hot water is used to continuously extract hesperidin, which overcomes the process defects of the current use of lime milk to extract hesperidin. Since the calcium ions in the lime milk combine with pectin to form calcium pectinate and solidify, the pectin in the citrus peel can no longer be extracted after the hesperidin is extracted. The use of this technology eliminates the adverse effects on the subsequent pectin extraction. Therefore, the continuous extraction of hesperidin and pectin from the citrus peel is achieved, and two high-value-added extraction substances are obtained in sequence from the citrus peel, which has extremely important economic value.

[0017] E. Extracting pectin: adding 2-3 times (by weight) softened water of the peel pulp to the three extraction tanks after the hesperidin extraction in step D, respectively, adjusting the pH value to 2 with a food-grade acidic pH regulator, heating to 95-98° C., extracting for 60 minutes, separating the extract to obtain a pectin extract solution; washing the peel pulp in the three extraction tanks with softened water in turn, and mixing the recovered washing liquid with the pectin extract solution; outputting the peel pulp in the three extraction tanks to a filter press by a screw pump for squeezing and dehydration, and recovering the squeezed separation liquid of the peel pulp, and mixing it with the pulp extract solution; filtering the above three liquids through a 120-160 mesh filter screen after mixing to obtain a pectin extract solution;

[0018] The pectin extract is filtered through a diatomaceous earth filter to remove insoluble impurities; 0.1% to 0.3% (by weight) of activated carbon is added and stirred evenly; the temperature is controlled at 60°C to 65°C and allowed to stand for 60 to 90 minutes for adsorption and decolorization;

[0019] The pectin extract is concentrated by an ultrafiltration device, the water in the pectin extract is separated through the ultrafiltration membrane, and the pectin and activated carbon are retained by the ultrafiltration membrane to become a pectin concentrate containing activated carbon; the pectin concentrate is filtered again by a diatomaceous earth filter to remove the activated carbon therein, and liquid pectin is obtained;

[0020] Slowly add 90% to 95% food-grade ethanol to the liquid pectin while stirring until the ethanol concentration reaches 50%, and let it stand for 30 minutes to allow the pectin to fully precipitate; take out the precipitated pectin and crush it, and add 2 to 3 times (by weight) of 95% food-grade ethanol again to fully wash and remove residual moisture in the pectin; vacuum dry at a temperature of 60° C. to 70° C. until the moisture content is less than 10%, crush it with a grinder, and sieve it with an 80-100 mesh sieve to obtain pectin powder.

[0021] The pectin extraction in step E adopts the ultrafiltration pectin concentration process. Since pectin is viscous and has poor fluidity, it is difficult to achieve the desired concentration multiple. In this step, a diatomaceous earth filter is used to filter the pectin extract. First, insoluble solids such as citrus peel fibers in the pectin extract are removed, so that the pectin extract is preliminarily purified. After the diatomaceous earth filtration, activated carbon is added to the pectin extract for adsorption and decolorization. In the ultrafiltration concentration operation of the pectin extract, the high-speed flowing pectin extract carries non-sticky activated carbon particles and flows synchronously. The high-speed flowing activated carbon particles have a flushing and cleaning effect on the ultrafiltration membrane surface, so that the ultrafiltration during the pectin extract concentration process can be kept stable. Then, a diatomaceous earth filter is used to filter the pectin concentrate for a second time to remove the activated carbon in the pectin concentrate. In this step, the ultrafiltration concentration of the pectin extract is used to increase the concentration of the pectin extract by 2 to 3 times, which not only greatly improves the concentration operation efficiency and saves the energy consumption of evaporation and concentration, but also reduces the ethanol consumption by 30% to 50% when ethanol is used to precipitate pectin, greatly improving the economy of the process.

[0022] In the pectin extraction of step E, the pectin extract is decolorized by activated carbon, the adsorption temperature is controlled to be 60° C. to 65° C., and the treatment time is 60 to 90 min; then the pectin extract is concentrated by an ultrafiltration device, the water in the pectin extract is separated through the ultrafiltration membrane, and the pectin and activated carbon are retained by the ultrafiltration membrane to form a pectin concentrate; the pectin concentrate is filtered again by a diatomaceous earth filter to remove the activated carbon, so that the quality of the pectin product is greatly improved.

[0023] Furthermore, in step B, pectinase is used to decompose pectin in the water-washing immersion liquid, and the amount of pectinase added is determined by a pectin enzymolysis test, and the test method is as follows:

[0024] Add 10ml of acidified alcohol to a test tube, then take 5ml of the washed sugar solution to which pectinase has been added and enzymatically hydrolyzed for 1h, filter it with filter paper and put it into a test tube, block the mouth of the test tube and gently invert it upside down 3 to 5 times to fully mix the contents. After mixing, judge the degree of pectin degradation based on the size and number of precipitated floccules and the speed of precipitation. A small amount of coagulation after mixing for 30s indicates that the pectin has begun to decompose. Observe after standing for 15min. If no white gel or floccules appear, it can be determined that the pectin decomposition test is negative, that is, the enzymatic reaction has reached the end point.

[0025] The best data obtained from this pectin enzymolysis test is used as the process guidance parameter. If the amount of pectinase added is insufficient, it can be remedied by adding pectinase or extending the enzymolysis time. In subsequent production, the amount of pectinase added is adjusted as the properties of the raw materials change, but other process conditions remain unchanged.

[0026] Due to the citrus variety, maturity, and picking season, the pectin content and pH value in citrus peel fluctuate greatly. When using pectinase to decompose the pectin in the washed sugar solution, it is not easy to give a fixed parameter value for the amount of pectinase added. Therefore, this step uses on-site pectin tests as a guide to determine the range of pectinase addition, which can not only meet production needs but also avoid unnecessary pectinase waste.

[0027] Furthermore, in the step B, the clear citrus infusion syrup is a concentrated solution containing monosaccharides, disaccharides, and organic acid-soluble solids. It can be widely used in the manufacture of condiments in the food industry, the provision of sugar sources for brewing product processing, etc.

[0028] Furthermore, in the step D, the hesperidin extraction mixed solution is filtered through a diatomaceous earth filter to remove insoluble impurities therein, and then the hesperidin extraction mixed solution is concentrated using a low-temperature vacuum evaporator to evaporate 70% to 80% of water, with a concentration ratio of 3:1 to 5:1 times, and the concentrated solution is cooled to 0 to 3° C. and allowed to stand for 10 hours to allow hesperidin to crystallize and precipitate, and the remaining residual liquid after recovering the crystals is returned to the extraction tank and reused 2 to 3 times, thereby improving the hesperidin extraction yield.

[0029] Because the residual liquid still contains about 40% to 50% hesperidin, recycling the residual liquid remaining after the precipitation of hesperidin can greatly improve the extraction rate of hesperidin.

[0030] Furthermore, in the step E, an ultrafiltration device is used to separate the pectin extract, and the ultrafiltration separation operation process parameters are: ultrafiltration membrane pore size 1-50nm, feed liquid temperature 60°C-65°C, operating pressure 0.50-0.56Mpa, and ultrafiltration feed liquid circulation volume 8-12 times the ultrafiltration separation capacity; water in the pectin extract is separated through the ultrafiltration membrane, and pectin and activated carbon are retained by the ultrafiltration membrane to become a pectin concentrate containing activated carbon. The pectin concentrate is filtered again by a diatomaceous earth filter to remove the activated carbon therein to obtain liquid pectin; the activated carbon adsorption decolorization combined with ultrafiltration concentration is adopted to greatly improve the quality of pectin products.

[0031] Furthermore, before the citrus peels in step A are crushed, citrus peel essential oil is extracted, citrus juice is squeezed, the core is separated and the peels are crushed. The specific method steps are as follows:

[0032] A1 Peel essential oil extraction: The citrus fruits are peeled by a peel grinding machine to destroy the tissue cells on the surface of the citrus peel, so that the peel essential oil is fully released from the peel cells, and the emulsion containing the peel essential oil is recovered. The emulsion containing the peel essential oil is centrifuged to obtain the citrus peel cold-pressed essential oil; by separating and recovering the peel essential oil, the citrus peel essential oil can be prevented from entering the extract and causing adverse effects on the quality of subsequent processed products;

[0033] A2 citrus juice extraction: the citrus after the peel essential oil is removed in step A1 is juiced by a juicer, and the obtained citrus juice is used to process citrus juice;

[0034] A3 Fruit core separation: After the citrus juice is squeezed in step A2, the citrus peel is subjected to fruit core separation, and the citrus core and the citrus peel are separated by stirring and centrifugal action generated by the rotation of the spiral blade, so that the citrus core in the citrus peel is removed; the separated citrus cores are collected and washed with water, and then soaked in 5% hydrogen peroxide at room temperature for 5 minutes, and then washed with running softened water for 5 minutes to remove the hydrogen peroxide, and dried to a moisture content of 8% to 10%, to obtain citrus cores; the citrus core separation in this step can avoid adverse effects on subsequent product processing and product quality;

[0035] A4 Peel crushing: The citrus peel separated from the core in step A3 is crushed by a crusher. An equal amount of softened water is sprayed into the crusher while the citrus peel is crushed. The particle size of the crushed citrus peel is between 10 and 18 mm. The crushed citrus peel is converted into peel pulp and then transported to three extraction tanks. Spraying softened water at the same time during crushing is beneficial to the crushing operation of the citrus peel and improves the fluidity of the peel pulp.

[0036] Further, in the step E, after the pectin extraction is completed, the peel pulp in the three extraction tanks is output to the filter press for squeezing and dehydration by a screw pump, and the peel pulp is used for dietary fiber preparation after being squeezed and dehydrated by the filter press. The specific method steps are as follows:

[0037] F. Preparation of dietary fiber: In the step E, the peel pulp from which pectin has been extracted in the three extraction tanks is output to a filter press by a screw pump for squeezing and dehydration. The peel pulp after squeezing and dehydration by the filter press becomes a peel wet cake, which is soaked and washed with softened water at 50°C to 60°C for 2 to 3 times, and then soaked in a 5% hydrogen peroxide solution at room temperature for 20 to 30 minutes for decolorization; then washed with flowing softened water to remove hydrogen peroxide, and the citrus peel is filtered and dehydrated again to obtain a citrus peel wet cake again; the citrus peel wet cake is crushed and dried to a moisture content of 6% to 8%, and then activated by screw extrusion technology to make it biologically active, and the extrusion conditions are: feed moisture 191.0 g / kg, terminal temperature 140°C, screw speed 60 r / min, the activated dietary fiber is dried again to a moisture content of less than 10%, crushed and sieved through a 120-mesh filter screen to obtain dietary fiber.

[0038] Furthermore, the citrus peel is the peel of any one of citrus, orange, grapefruit, and lemon; the peel is freshly squeezed peel or dried peel. The method of the present invention can be applied to citrus, orange, grapefruit, lemon and other fruits, and the peel is freshly squeezed peel or dried peel.

[0039] Furthermore, the present invention provides a citrus peel progressive extraction device, comprising a citrus peel pretreatment system and a citrus peel progressive extraction system;

[0040] The citrus peel pre-treatment system comprises a fruit core separation device, a citrus peel grinding machine, a juicer, a fruit peel crusher, a fruit peel pulp tank, and a screw pump. The fruit peel outlet of the juicer is arranged above the feed inlet of the fruit core separation device; the discharge port of the fruit core separation device is arranged above the feed inlet of the fruit peel crusher; the discharge port of the fruit peel crusher is arranged above the feed inlet of the fruit peel pulp tank; the screw pump is connected to the conveying pipeline of the discharge port at the bottom of the fruit peel pulp tank;

[0041] The citrus peel progressive extraction system comprises a first leaching tank, a second leaching tank, a third leaching tank, a storage tank group, a plate heat exchanger, a pipeline switching plate, a diatomaceous earth filter, an ultrafiltration device, a low-temperature vacuum evaporator, a filter press, a dryer, and a screw extruder;

[0042] The discharge port of the peel pulp tank is connected to the tank tops of the first extraction tank, the second extraction tank, and the third extraction tank respectively through a delivery pipe provided with a screw pump;

[0043] The bottoms of the first leaching tank, the second leaching tank, and the third leaching tank are respectively connected to the storage tank group through a delivery pipeline, and the delivery pipeline is also provided with a three-way valve and a bypass pipe respectively connected to the plate heat exchanger and the pipeline switching plate;

[0044] The storage tank group is connected to the ultrafiltration device, the low-temperature vacuum evaporator, the diatomaceous earth filter, and the filter press through a delivery pipeline; the pipeline switching plate is connected to the plate heat exchanger through a delivery pipeline; and the delivery pipeline is provided with a centrifugal pump.

[0045] The first leaching tank, the second leaching tank and the third leaching tank are respectively provided with a water inlet pipe with a nozzle.

[0046] By switching the pipelines connected by the pipeline switching plate and automatically switching the valves, the extraction liquid transportation can meet the various different process requirements of each step. The dryer and the screw extruder are combined to form a citrus peel dietary fiber puffing processing system.

[0047] Furthermore, the fruit core separation device includes a fruit core separation screen cylinder, spiral blades, a rotating shaft, a driving motor, and a fruit core collecting plate; the driving motor is connected to the spiral blades located in the fruit core separation screen cylinder through the rotating shaft, and the lower cylinder body of the fruit core separation screen cylinder is provided with fruit core screen holes for separating fruit cores; an arc-shaped fruit core collecting plate is provided below the fruit core separation screen cylinder, a fruit peel feed port is provided at one end of the fruit core separation screen cylinder, and a fruit peel discharge port is provided at the other end, a fruit core collecting groove is provided at the left end of the fruit core collection plate, and a spray pipe for flushing is provided between the fruit core separation screen cylinder and the fruit core collection plate.

[0048] During the process of being conveyed by the core separation screen, the citrus core is gradually separated from the citrus peel by the stirring and centrifugal action generated by the continuous rotation of the spiral blades, and falls through the core sieve holes of the core separation screen onto the core collecting plate, and is collected by the core collecting trough to obtain the citrus core.

[0049] Citrus pits recovered from citrus fruits have an oil content of up to 20% to 25% after washing and drying, and have a variety of uses: for example, the fatty acid composition of citrus pit oil is 35% to 37% linoleic acid, 26% to 31% palmitic acid, and 24% to 28% oleic acid, which is close to cottonseed oil and can be used as edible oil; the crude oil of the pit can be decolorized, deodorized and refined to obtain refined oil with an aroma similar to olive oil; the pit oil can be used to make margarine after hydrogenation; and can be used as a flavor for soft drinks after bromination. Citrus pits are rich in protein. Crushing citrus pits or adding citrus pit oil residues to animal feed can increase the oil and protein content of feed and obtain high-quality feed with higher value. Crude citrus pit oil can also be used as a raw material for processing soaps and sulfonated oils. Since summer citrus seed oil contains limonoids with a strong bitter taste, it can be used for limonin extraction and can also be used as a pharmaceutical raw material.

[0050] Furthermore, the bottoms of the first, second and third extraction tanks are conical, and a conical filter screen is provided in the bottom of the tank. A spacing is provided between the conical filter screen and the conical bottom, and the volume formed between the two is the buffer space for the extraction liquid level. When the extraction liquid separated from the bottom of the tank is filtered through the conical filter screen, the granular peel in the extraction liquid is intercepted, which is conducive to controlling the mixing of peel materials in the extraction liquid.

[0051] Furthermore, filter screens are provided at the upper parts of the first extraction tank, the second extraction tank and the third extraction tank respectively, and the filter screens limit the floating of the citrus peels to ensure that all the peel pulp is effectively extracted.

[0052] The beneficial effects of the present invention are as follows: the present invention adopts citrus peel to continuously extract citrus peel, and can gradually complete the continuous extraction of citrus peel washing liquid syrup, hesperidin and pectin substances without multiple transfer and transportation of citrus peel residue; compared with the traditional extraction process, the extraction process does not require multiple transfer and transportation of citrus peel and several squeezing and dehydration operations, and transforms the traditional complicated extraction operation into a simplified, continuous and systematic one, greatly reducing repetitive labor, power and energy consumption, and also greatly reducing material loss in the processing process, shortening the product processing operation cycle, having good economic benefits, and having very important strategic significance for promoting the sustainable economic development of my country's citrus industry.

[0053] In step B of the present invention, three extraction tanks are used to extract and recover citrus peel extraction sugar solution in sequence at room temperature. Extraction under low temperature conditions can ensure that the extraction process will not have a significant impact on the structural changes of the citrus peel.

[0054] In step B, process water is used to wash citrus peels to obtain citrus peel extract sugar solution, the main components of which are water, soluble monosaccharides, disaccharides, some oligosaccharides, organic acids and citrus aromatic substances. After decolorization, the obtained citrus extract syrup has the basic characteristics of clarified juice. In this way, the peel water-washed sugar solution is converted into edible citrus peel extract sugar solution, which greatly increases the added value of the product.

[0055] In step B, the viscosity of the citrus water-washed sugar solution is reduced by enzymatic hydrolysis with pectinase, thereby effectively improving its fluidity to adapt to the subsequent concentration operation of a low-temperature vacuum falling film evaporator, so as to obtain a citrus infusion syrup with a soluble solid content of 70.0 to 70.5 Brix, thereby improving the safety of product storage, greatly reducing packaging, saving storage space, and reducing logistics costs.

[0056] In step B, soluble solids, pigments, organic acids, aroma and other impurities in the citrus peel are effectively removed by water washing, so that the components of the citrus peel are deeply purified, providing favorable conditions for the subsequent preparation of high-purity products.

[0057] Step D uses cellulase extraction and hot water to continuously extract hesperidin, which overcomes the process defects of using lime milk to extract hesperidin. The calcium ions in the lime milk combine with pectin to form calcium pectinate and solidify, resulting in the inability to extract pectin from the citrus peel after the hesperidin is extracted. In this way, the subsequent pectin extraction process obstacles are eliminated, and the continuous extraction of hesperidin and pectin from the citrus peel is achieved.

[0058] Since the residual extract after obtaining the hesperidin crystals still contains about 40% to 50% of hesperidin, in step D, the residual extract after obtaining the crystals is used again for the extraction of hesperidin, which greatly improves the extraction rate of hesperidin.

[0059] Step E Pectin extraction, because pectin is viscous and has poor fluidity, it is difficult to concentrate the pectin extract to achieve the expected concentration multiple. The technology of the present invention first uses a diatomaceous earth filter to filter the pectin extract to remove insoluble solids such as citrus peel fiber in the pectin extract, so that the pectin extract is initially purified; after diatomaceous earth filtration, activated carbon is added to the pectin extract for adsorption and decolorization. During the ultrafiltration concentration operation of the pectin extract, the high-speed flowing pectin extract carries the non-sticky activated carbon particles and flows synchronously. The high-speed flowing activated carbon particles have a flushing and cleaning effect on the ultrafiltration membrane surface, thus achieving the stable operation of the ultrafiltration device in the pectin extract concentration process.

[0060] In step E pectin extraction, the pectin extract is decolorized by activated carbon, the adsorption temperature is controlled at 60℃~65℃, and the treatment time is 60~90min; then the pectin extract is concentrated by ultrafiltration device to separate the water in the pectin extract, while the pectin and activated carbon are retained by the ultrafiltration membrane to form pectin concentrate; the pectin concentrate is filtered again by diatomaceous earth filter to remove the activated carbon. The quality of pectin products is greatly improved by using activated carbon adsorption decolorization and ultrafiltration non-heating concentration;

[0061] In step E, the pectin extract is concentrated by ultrafiltration, which can increase the concentration of the pectin extract by 2 to 3 times, which not only greatly improves the concentration efficiency and saves the energy consumption of evaporation and concentration, but also reduces the ethanol consumption by 30% to 50% when ethanol is used to precipitate pectin, thereby greatly improving the economy of the process.

[0062] Citrus peels that have been subjected to pectin extraction are used to prepare dietary fiber. The citrus peels have completed pretreatments such as decolorization, debittering, and removal of impurities during the gradual extraction process. There is very little soluble fiber material remaining in the peels, and the main components are relatively simple fiber materials such as insoluble cellulose, hemicellulose, and lignin. The above peels are directly used for the processing of dietary fiber, and all pretreatment operations of the citrus peels can be omitted.

[0063] The citrus peel progressive extraction device system of the present invention can meet various process requirements of each step by connecting the pipelines through the pipeline switching plate and automatically switching the valves. If the connecting pipelines are designed to be fully automated, the process operation will be simplified and the production efficiency will be greatly improved.

[0064] The present invention adopts a process combining the circulation of the extracting liquid with the secondary extraction, which greatly increases the concentration of soluble solids in the extracting liquid, saves heat energy consumption when the extracting liquid is evaporated and concentrated, and greatly improves the operating efficiency. At the same time, the concentration of organic matter discharged in the production discharge water is also greatly reduced, thereby effectively reducing the operating cost of sewage treatment in production. The implementation of the progressive extraction of citrus peel not only obtains rich and valuable products, but also realizes the full utilization of citrus peel, eliminating the environmental pollution risk caused by poor management of citrus peel.

[0065] The present invention adopts a technology that combines graded recovery with progressive extraction. Citrus peel essential oil and important substances in citrus core can be obtained during the pretreatment of citrus peel; high value-added products such as citrus infusion syrup, hesperidin, pectin, etc. can be obtained during the progressive extraction process, thereby expanding new resources for the development of the food processing industry. From the perspective of resource utilization, the full recovery and utilization of effective ingredients in citrus peel is truly realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic diagram of the structure of the present invention;

[0067] Figure 2 It is a structural schematic diagram of the fruit core separation device of the present invention.

[0068] Parts and numbers in the picture:

[0069] 1-fruit core separation device; 2-citrus peel grinding machine; 3-juicer; 4-fruit peel crusher; 5-fruit peel pulp tank; 6-screw pump; 11-fruit core separation screen cylinder; 12-spiral blade; 13-rotating shaft; 14-driving motor; 15-fruit core collection plate; 16-fruit core sieve hole; 17-fruit peel feed port; 18-fruit peel discharge port; 19-fruit core collection tank; 20-spray pipe; 21-plate heat exchanger; 22-pipeline switching plate; 23-diatomaceous earth filter; 24-ultrafiltration device; 25-low-temperature vacuum evaporator; 26-filter press; 27-dryer; 28-screw extruder; 111-storage tank group; 101-first leaching tank; 102-second leaching tank; 103-third leaching tank; 222-water inlet pipe; 300-filter screen plate; 333-conical filter screen plate; 600-Centrifugal pump. DETAILED DESCRIPTION

[0070] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0071] Example 1

[0072] A method for progressive extraction of citrus peels, wherein citrus infusion syrup, hesperidin, pectin and dietary fiber products are obtained in sequence by progressive extraction of citrus peels. The specific process steps of the progressive extraction of citrus peels are as follows:

[0073] A. Pretreatment of citrus peels: Take the citrus peels after juicing, crush them into particles with a size of 10-18 mm, spray softened water into the citrus peels while crushing them, and the crushed citrus peels become peel pulp, which is then transported to three extraction tanks respectively;

[0074] B. Extracting citrus infusion syrup: add 2-3 times (by weight) of softened water to the first extraction tank, immerse the peel pulp completely in the softened water, and let it stand for 20 minutes; transfer the extract in the first extraction tank to the second extraction tank, and let it stand for 20 minutes to extract the peel pulp; transfer the extract in the second extraction tank to the third extraction tank, and let it stand for 20 minutes to extract the peel pulp; collect the extract in the third extraction tank, filter it with a 120-160 mesh filter screen, remove the impurities of the peel and pulp suspended in the extract, and obtain the citrus peel water-washed sugar solution;

[0075] The citrus peel water-washed sugar liquid is pasteurized by a plate heat exchanger at a sterilization temperature of 90 to 93° C. and a sterilization time of 15 to 20 seconds. The outlet temperature of the citrus peel water-washed sugar liquid is controlled to be between 50° C. and 55° C., 0.03% to 0.06% (by weight) of activated carbon is added to the citrus peel water-washed sugar liquid for decolorization, and pectinase is added at the same time. The pectinase is obtained by dissolving pectinase solid in 5 times softened water in advance, and the temperature is maintained at 50° C. to 55° C. and the enzymolysis time is 40 to 60 minutes to decompose the pectin in the citrus peel water-washed sugar liquid; the enzymolysis is stopped when the pectin enzymolysis test is negative; when the enzymolysis reaches the end point, the suspended matter in the citrus peel water-washed sugar liquid is mutually adsorbed and flocculated, and a precipitate is formed and settled at the bottom, and the citrus peel water-washed sugar liquid is clarified;

[0076] The supernatant of the citrus peel water-washed sugar solution after enzymatic hydrolysis is taken out, and the suspended pulp and high molecular polymer therein are separated by an ultrafiltration device, the pore size of the ultrafiltration membrane core is 1-50 nm, the temperature is 50° C.-55° C., the operating pressure is 0.50-0.56 MPa, and the ultrafiltration liquid circulation volume is 8-12 times the ultrafiltration separation capacity, wherein water and monosaccharides, disaccharides, and organic acid soluble solids pass through the ultrafiltration membrane, and the transparent ultrafiltration permeate is collected, and then it is concentrated to soluble solids 70.0-70.5 Brix by a low-temperature vacuum evaporator to obtain a clear citrus infusion syrup;

[0077] Finally, the clear citrus infusion syrup is a concentrated solution containing monosaccharides, disaccharides, and organic acid soluble solids. It can be widely used in the manufacture of condiments in the food industry, as an additive, and as a carbon source for brewing product processing.

[0078] C. Extraction of hesperidin by primary enzymatic hydrolysis: After the sugar solution is extracted in step B, softened water of 2 to 3 times (by weight) of the peel pulp is added to the three extraction tanks respectively, and then 0.01% to 0.03% (by weight) of cellulase is added to the peel pulp. Before adding the cellulase, the cellulase is diluted and dissolved into a cellulase solution with softened water of 5 times (by weight) of the cellulase. The extract in the extraction tank is circulated and heated by a plate heat exchanger, and the cellulase solution and the extract are fully mixed at the same time. When the extract reaches 40° C. to 50° C., the circulation is stopped, and the enzymatic hydrolysis is allowed to stand for 3 to 4 hours. The extract is separated from the three extraction tanks to obtain a primary hesperidin extract;

[0079] D. Secondary hot water continuous extraction of hesperidin: After completing the bioenzymatic extraction of hesperidin in step C, add softened water twice (by weight) of the peel pulp into the first extraction tank, heat to 90° C. using a plate heat exchanger, and extract for 20 minutes, transfer the hot water extract in the first extraction tank to the second extraction tank, control the temperature at 85° C. in the second extraction tank, and extract for 20 minutes, then transfer the extract in the second extraction tank to the third extraction tank, control the temperature at 85° C., and extract for 20 minutes, separate the extract to obtain a third hesperidin hot water extract, mix the third hesperidin hot water extract with the first hesperidin extract extracted by the bioenzymatic method in step C, and obtain a hesperidin extraction mixture;

[0080] The hesperidin extraction mixed solution is filtered through a diatomaceous earth filter to remove insoluble impurities therein, and then concentrated using a low-temperature vacuum evaporator to evaporate 70% to 80% of water with a concentration ratio of 3:1 to 5:1 times, and the concentrated solution is cooled to 0 to 3° C. and allowed to stand for 10 hours to allow hesperidin to crystallize;

[0081] The hesperidin crystals are taken out and washed with water, then dissolved with 20 times (by weight) of 1% food-grade sodium hydroxide solution, and filtered with a 200-mesh filter screen; the pH value is adjusted to 10 with a food-grade acidic pH regulator, and then carbon dioxide gas is introduced to reprecipitate the hesperidin to obtain a hesperidin extract; the hesperidin extract is dehydrated by filtering with a filter press, and then dried with hot air at a temperature of 70° C. to 80° C. until the water content is less than 5%, and the hesperidin product is obtained after crushing;

[0082] E. Extracting pectin: adding 2-3 times (by weight) softened water of the peel pulp to the three extraction tanks after the hesperidin extraction in step D, respectively, adjusting the pH value to 2 with a food-grade acidic pH regulator, heating to 95-98° C., extracting for 60 minutes, separating the extract to obtain a pectin extract solution; washing the peel pulp in the three extraction tanks with softened water in turn, and mixing the recovered washing liquid with the pectin extract solution; outputting the peel pulp in the three extraction tanks to a filter press by a screw pump for squeezing and dehydration, and recovering the squeezed separation liquid of the peel pulp, and mixing it with the pulp extract solution; after the above three liquids are mixed, filtering through a 120-160 mesh filter screen to obtain a pectin extract solution;

[0083] The pectin extract is filtered through a diatomaceous earth filter to remove insoluble impurities; 0.1% to 0.3% (by weight) of activated carbon is added and stirred evenly; the temperature is controlled at 60°C to 65°C and allowed to stand for 60 to 90 minutes for adsorption and decolorization;

[0084] The pectin extract is concentrated by an ultrafiltration device, the water in the pectin extract is separated through the ultrafiltration membrane, and the pectin and activated carbon are retained by the ultrafiltration membrane to become a pectin concentrate containing activated carbon; the pectin concentrate is filtered again by a diatomaceous earth filter to remove the activated carbon therein, and liquid pectin is obtained;

[0085] Slowly add 90% to 95% food-grade ethanol to the liquid pectin while stirring until the ethanol concentration reaches 50%, and let it stand for 30 minutes to allow the pectin to fully precipitate; take out the precipitated pectin and crush it, and add 2 to 3 times (by weight) of 95% food-grade ethanol again to fully wash and remove residual moisture in the pectin; vacuum dry at a temperature of 60° C. to 70° C. until the moisture content is less than 10%, crush it with a grinder, and sieve it with an 80-100 mesh sieve to obtain pectin powder.

[0086] Wherein, in the step B, pectinase is used to decompose the pectin in the water washing solution, and the amount of pectinase added is determined by a pectin enzymolysis test, and the test method is as follows:

[0087] Add 10ml of acidified alcohol to a test tube, then take 5ml of the washed sugar solution to which pectinase has been added and enzymatically hydrolyzed for 1h, filter it with filter paper and put it into a test tube, block the mouth of the test tube and gently invert it upside down 3 to 5 times to fully mix the contents. After mixing, judge the degree of pectin degradation based on the size and number of precipitated floccules and the speed of precipitation. A small amount of coagulation after mixing for 30s indicates that the pectin has begun to decompose. Observe after standing for 15min. If no white gel or floccules appear, it can be determined that the pectin decomposition test is negative, that is, the enzymatic reaction has reached the end point.

[0088] The best data obtained from this pectin enzymolysis test is used as the process guidance parameter. If the amount of pectinase added is insufficient, it can be remedied by adding pectinase or extending the enzymolysis time. In subsequent production, the amount of pectinase added is adjusted as the properties of the raw materials change, but other process conditions remain unchanged.

[0089] In the step D, the hesperidin extraction mixed solution is filtered through a diatomaceous earth filter to remove insoluble impurities therein, and then the hesperidin extraction mixed solution is concentrated by a low-temperature vacuum evaporator to evaporate 70% to 80% of water, with a concentration ratio of 3:1 to 5:1. The concentrated solution is cooled to 0 to 3° C. and allowed to stand for 10 hours to allow hesperidin to crystallize and precipitate. After the crystals are recovered, the remaining residual liquid is returned to the extraction tank and reused 2 to 3 times before being discharged, thereby increasing the hesperidin extraction yield.

[0090] In the step E, an ultrafiltration device is used to separate the pectin extract, and the ultrafiltration separation operation process parameters are: ultrafiltration membrane pore size 1-50nm, feed liquid temperature 60°C-65°C, operating pressure 0.50-0.56Mpa, and ultrafiltration feed liquid circulation volume 8-12 times the ultrafiltration separation capacity; water in the pectin extract is separated through the ultrafiltration membrane, and pectin and activated carbon are retained by the ultrafiltration membrane to become a pectin concentrate containing activated carbon, and the pectin concentrate is filtered again by a diatomaceous earth filter to remove the activated carbon therein to obtain liquid pectin; the activated carbon adsorption decolorization combined with ultrafiltration concentration is adopted to greatly improve the quality of pectin products.

[0091] The method of the invention can be used for the progressive extraction of effective components of any one of citrus, orange, grapefruit and lemon; the peel used can be freshly squeezed peel or dried peel.

[0092] Example 2

[0093] Dietary fiber preparation: After completing step E of Example 1, the peel pulp in the three extraction tanks is output to a filter press for dehydration by a screw pump after pectin extraction, and is used for dietary fiber preparation after dehydration. The specific method steps are as follows:

[0094] F. Preparation of dietary fiber: In the step E, the peel pulp from which pectin has been extracted in the three extraction tanks is output to a filter press by a screw pump for squeezing and dehydration. The peel pulp after squeezing and dehydration by the filter press becomes a peel wet cake, which is soaked and washed with softened water at 50°C to 60°C for 2 to 3 times, and then soaked in a 5% hydrogen peroxide solution at room temperature for 20 to 30 minutes for decolorization; then washed with flowing softened water to remove hydrogen peroxide, and the citrus peel is filtered and dehydrated again to obtain a citrus peel wet cake again; the citrus peel wet cake is crushed and dried to a moisture content of 6% to 8%, and then activated by screw extrusion technology to make it biologically active, and the extrusion conditions are: feed moisture 191.0 g / kg, terminal temperature 140°C, screw speed 60 r / min, the activated dietary fiber is dried again to a moisture content of less than 10%, crushed and sieved through a 120-mesh filter screen to obtain dietary fiber.

[0095] Example 3

[0096] Citrus peel pretreatment includes citrus peel essential oil extraction, citrus juice extraction, core separation and peel crushing. The specific steps are as follows:

[0097] A1 Peel essential oil extraction: The citrus fruits are peeled by a peel grinding machine to destroy the tissue cells on the surface of the citrus peel, so that the peel essential oil is fully released from the peel cells, and the emulsion containing the peel essential oil is recovered. The emulsion containing the peel essential oil is centrifuged to obtain the citrus peel cold-pressed essential oil; by separating and recovering the peel essential oil, the citrus peel essential oil can be prevented from entering the extract and causing adverse effects on subsequent product processing and product quality;

[0098] A2 citrus juice extraction: the citrus after the peel essential oil is removed in step A1 is juiced by a juicer, and the obtained citrus juice is used to process citrus juice;

[0099] A3 Fruit core separation: After the citrus juice is squeezed in step A2, the citrus peel is subjected to fruit core separation, and the citrus core is separated from the citrus peel by the stirring and centrifugal effects generated by the rotation of the spiral blade, so that the citrus core in the citrus peel is separated and removed; the separated citrus cores are collected and washed with 5% hydrogen peroxide, and the cores are soaked at room temperature for 5 minutes, and then washed with running softened water for 5 minutes to remove the hydrogen peroxide, and dried to a moisture content of 8% to 10%, to obtain citrus cores; the citrus core separation in this step can avoid adverse effects on subsequent product processing and product quality;

[0100] A4 Peel crushing: The citrus peel separated from the core in step A3 is crushed by a crusher. An equal amount of softened water is sprayed into the crusher while the citrus peel is crushed. The particle size of the crushed citrus peel is between 10 and 18 mm. The crushed citrus peel is converted into peel pulp. Spraying softened water at the same time during crushing is beneficial to the crushing operation of the citrus peel and improves the fluidity of the peel pulp.

[0101] The present invention provides a citrus peel progressive extraction device, such as Figure 1 As shown, it includes a citrus peel pre-treatment system and a citrus peel progressive extraction system;

[0102] The citrus peel pre-treatment system comprises a core separation device 1, a citrus peel grinding machine 2, a juicer 3, a peel crusher 4, a peel pulp tank 5, and a screw pump 6. The peel outlet of the juicer 3 is arranged above the feed inlet of the core separation device 1; the discharge port of the core separation device 1 is arranged above the feed inlet of the peel crusher 4; the discharge port of the peel crusher 4 is arranged above the feed inlet of the peel pulp tank 5; the screw pump 6 is connected to the conveying pipeline of the discharge port at the bottom of the peel pulp tank 5;

[0103] The citrus peel progressive extraction system comprises a first leaching tank 101, a second leaching tank 102, a third leaching tank 103, a storage tank group 111, a plate heat exchanger 21, a pipeline switching plate 22, a diatomaceous earth filter 23, an ultrafiltration device 24, a low-temperature vacuum evaporator 25, a filter press 26, a dryer 27, and a screw extruder 28;

[0104] The discharge port of the peel pulp tank 5 is connected to the top of the first extraction tank 101, the second extraction tank 102, and the third extraction tank 103 respectively through a delivery pipe provided with a screw pump 6;

[0105] The bottoms of the first leaching tank 101, the second leaching tank 102, and the third leaching tank 103 are respectively connected to the storage tank group 111 through a delivery pipeline, and the delivery pipeline is also provided with a three-way valve and a bypass pipe respectively connected to the plate heat exchanger 21 and the pipeline switching plate 22;

[0106] The storage tank group 111 is connected to the ultrafiltration device 24, the low-temperature vacuum evaporator 25, the diatomaceous earth filter 23, and the filter press 26 through a delivery pipeline; the pipeline switching plate 22 is connected to the plate heat exchanger 21 through a delivery pipeline; the delivery pipeline is provided with a centrifugal pump 600.

[0107] The first leaching tank 101, the second leaching tank 102, and the third leaching tank 103 are respectively provided with a water inlet pipe 222 with a nozzle.

[0108] Through the switching of the pipeline connection and the automatic valve switching of the pipeline switching plate 22, the extraction liquid delivery can meet the various process requirements of each step. The combination of the drying machine 27 and the screw extruder 28 constitutes a citrus peel dietary fiber expansion processing system.

[0109] like Figure 2 As shown, the fruit core separation device 1 includes a fruit core separation screen cylinder 11, a spiral blade 12, a rotating shaft 13, a driving motor 14, and a fruit core collecting plate 15; the driving motor 14 is connected to the spiral blade 12 located in the fruit core separation screen cylinder 11 through the rotating shaft 13, and the lower cylinder body of the fruit core separation screen cylinder 11 is provided with a fruit core screen hole 16 for separating fruit cores; an arc-shaped fruit core collecting plate 15 is provided below the fruit core separation screen cylinder 11, a peel feed port 17 is provided at one end of the fruit core separation screen cylinder 11, and a peel discharge port 18 is provided at the other end, a fruit core collecting groove 19 is provided at the left end of the fruit core collecting plate 15, and a spray pipe 20 for flushing is provided between the fruit core separation screen cylinder 11 and the fruit core collecting plate 15.

[0110] During the process of being conveyed by the core separation screen drum 11, the citrus core is gradually separated from the citrus peel by the stirring and centrifugal action generated by the continuous rotation of the spiral blades, and falls onto the core collection plate 15 through the core sieve holes 16 of the core separation screen drum 11, and is collected by the core collection tank 19 to obtain the citrus core. The citrus cores recovered from citrus fruits can be used as raw materials in the food industry or other industrial processing after washing and drying.

[0111] The bottoms of the first leaching tank 101, the second leaching tank 102, and the third leaching tank 103 are conical, and a conical filter screen plate 333 is provided in the bottom of the tank. A spacing is provided between the conical filter screen plate 333 and the conical bottom, and the volume formed between the two is the buffer space for the level of the leaching liquid. When the leaching liquid separated from the bottom of the tank is filtered through the conical filter screen plate 333, the granular peel in the leaching liquid is intercepted and output, which is conducive to controlling the mixing of peel substances in the leaching liquid.

[0112] Filter screen plates 300 are respectively arranged at the upper parts of the first extraction tank 101, the second extraction tank 102 and the third extraction tank 103. The filter screen plates 300 limit the citrus peels from floating up to ensure that the peel pulp is fully and effectively extracted.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for progressive extraction of citrus peel, characterized in that: By progressively extracting citrus peels, citrus infusion syrup, hesperidin, pectin and dietary fiber products are obtained in sequence. The specific process steps of progressive extraction of citrus peels are as follows: A. Pretreatment of citrus peels: Take the citrus peels after juicing, crush them into particles with a size of 10-18 mm, spray softened water into the citrus peels while crushing them, and the crushed citrus peels become peel pulp, which is then transported to three extraction tanks respectively; B. Extracting citrus infusion syrup: adding 2 to 3 times (by weight) of softened water to the first leaching tank, completely immersing the peel pulp in the softened water, and standing for leaching for 20 minutes; transferring the extract in the first leaching tank to the second leaching tank, and standing for leaching the peel pulp in the second leaching tank for 20 minutes; transferring the extract in the second leaching tank to the third leaching tank, and standing for leaching the peel pulp for 20 minutes; collecting the extract in the third leaching tank, filtering with a 120-160 mesh filter screen, removing impurities of the peel and pulp suspended in the extract, and obtaining citrus peel water-washed sugar solution; The citrus peel water-washed sugar liquid is pasteurized by a plate heat exchanger at a sterilization temperature of 90 to 93° C. and a sterilization time of 15 to 20 seconds. The outlet temperature of the citrus peel water-washed sugar liquid is controlled to be between 50° C. and 55° C., 0.03% to 0.06% (by weight) of activated carbon is added to the citrus peel water-washed sugar liquid for decolorization, and pectinase is added at the same time. The pectinase is obtained by pre-dissolving pectinase dry powder with 5 times softened water. The temperature is maintained at 50° C. to 55° C. and the enzymolysis time is 40 to 60 minutes to decompose the pectin in the citrus peel water-washed sugar liquid. When the pectin enzymolysis test is negative, the enzymolysis reaches the end point and the enzymolysis is stopped. When the enzymolysis reaches the end point, the suspended matter in the citrus peel water-washed sugar liquid adsorbs and flocculates to form a precipitate that settles to the bottom, and the citrus peel water-washed sugar liquid is clarified. The supernatant of the citrus peel water-washed sugar solution after enzymatic hydrolysis is taken out, and the suspended pulp and high molecular polymer therein are separated by an ultrafiltration device, the pore size of the ultrafiltration membrane core is 1-50 nm, the temperature is 50° C.-55° C., the operating pressure is 0.50-0.56 MPa, and the ultrafiltration liquid circulation volume is 8-12 times the ultrafiltration separation capacity, wherein water and monosaccharides, disaccharides, and organic acid soluble solids pass through the ultrafiltration membrane, and the transparent ultrafiltration permeate is collected, and then it is concentrated to soluble solids 70.0-70.5 Brix by a low-temperature vacuum evaporator to obtain a clear citrus infusion syrup; C. Extraction of hesperidin by primary enzymatic hydrolysis: After the sugar solution is extracted in step B, softened water of 2 to 3 times (by weight) of the peel pulp is added to the three extraction tanks respectively, and then 0.01% to 0.03% (by weight) of cellulase is added to the peel pulp. Before adding the cellulase, the cellulase is diluted and dissolved into a cellulase solution with softened water of 5 times (by weight) of the cellulase. The extract in the extraction tank is circulated and heated by a plate heat exchanger, and the cellulase solution and the extract are fully mixed at the same time. When the extract reaches 40° C. to 50° C., the circulation is stopped, and the enzymatic hydrolysis is allowed to stand for 3 to 4 hours. The extract is separated from the three extraction tanks to obtain a primary hesperidin extract; D. Secondary hot water continuous extraction of hesperidin: After completing the bioenzymatic extraction of hesperidin in step C, add softened water twice (by weight) of the peel pulp into the first extraction tank, heat to 90° C. using a plate heat exchanger, and extract for 20 min. Transfer the hot water extract in the first extraction tank to the second extraction tank, control the temperature at 85° C. in the second extraction tank, and extract for 20 min. Transfer the extract in the second extraction tank to the third extraction tank, control the temperature at 85° C., and extract for 20 min. Separate the extract to obtain a third hesperidin hot water extract, and mix the third hesperidin hot water extract with the first hesperidin extract extracted by the bioenzymatic method in step C to obtain a hesperidin extraction mixture; The hesperidin extraction mixture is filtered through a diatomaceous earth filter to remove insoluble impurities, and then concentrated using a low-temperature vacuum evaporator to evaporate 70% to 80% of water, and the concentrated solution is cooled to 0 to 3° C. and allowed to stand for 10 hours to allow hesperidin to crystallize; The hesperidin crystals are taken out and washed with water, then dissolved with 20 times (by weight) 1% food-grade sodium hydroxide solution, and filtered with a 200-mesh filter screen; the pH value is adjusted to 10 with a food-grade acidic pH regulator, and then carbon dioxide gas is introduced to reprecipitate the hesperidin to obtain a hesperidin extract; the hesperidin extract is dehydrated by filtering with a filter press, and then dried with hot air at 70° C. to 80° C. until the water content is less than 5%, and the hesperidin product is obtained after crushing; E. Extracting pectin: adding 2-3 times (by weight) softened water of the peel pulp to the three extraction tanks after the hesperidin extraction in step D, respectively, adjusting the pH value to 2 with a food-grade acidic pH regulator, heating to 95-98° C., extracting for 60 minutes, separating the extract to obtain a pectin extract solution; washing the peel pulp in the three extraction tanks with softened water in turn, and mixing the recovered washing liquid with the pectin extract solution; outputting the peel pulp in the three extraction tanks to a filter press by a screw pump for squeezing and dehydration, and recovering the squeezed separation liquid of the peel pulp, and mixing it with the pulp extract solution; filtering the above three liquids through a 120-160 mesh filter screen after mixing to obtain a pectin extract solution; The pectin extract is filtered through a diatomaceous earth filter to remove insoluble impurities; 0.1% to 0.3% (by weight) of activated carbon is added and stirred evenly; the temperature is controlled at 60° C. to 65° C. and allowed to stand for 60 to 90 minutes for adsorption and decolorization; The pectin extract is concentrated by an ultrafiltration device, the water in the pectin extract is separated through the ultrafiltration membrane, and the pectin and activated carbon are retained by the ultrafiltration membrane to become a pectin concentrate containing activated carbon; the pectin concentrate is filtered again by a diatomaceous earth filter to remove the activated carbon therein, and liquid pectin is obtained; Slowly add 90% to 95% food-grade ethanol to the liquid pectin while stirring until the ethanol concentration reaches 50%, and let it stand for 30 minutes to allow the pectin to fully precipitate; take out the precipitated pectin and crush it, and add 2 to 3 times (by weight) of 95% food-grade ethanol again to fully wash and remove residual moisture in the pectin; vacuum dry at 60° C. to 70° C. until the water content is less than 10%, crush it with a grinder, and sieve it with a 80-100 mesh sieve to obtain pectin powder.

2. A citrus peel progressive extraction method according to claim 1, characterized in that: In the step B, pectinase is used to decompose the pectin in the water-washing immersion liquid. The amount of pectinase added is determined by a pectin enzymolysis test, and the test method is as follows: Add 10ml of acidified alcohol to a test tube, then take 5ml of the washed sugar solution to which pectinase has been added and enzymatically hydrolyzed for 1h, filter it with filter paper and put it into a test tube, block the mouth of the test tube and gently invert it upside down 3 to 5 times to fully mix the contents. After mixing, judge the degree of pectin degradation based on the size and number of precipitated floccules and the speed of precipitation. A small amount of coagulation after mixing for 30s indicates that the pectin has begun to decompose. Observe after standing for 15min. If no white gel or floccules appear, it can be determined that the pectin decomposition test is negative, that is, the enzymatic reaction has reached the end point.

3. A citrus peel progressive extraction method according to claim 1, characterized in that: In the step B, the clarified citrus infusion syrup is a concentrated solution containing monosaccharides, disaccharides and organic acid-soluble solids.

4. A citrus peel progressive extraction method according to claim 1, characterized in that: In the step D, the hesperidin extraction mixture is filtered through a diatomaceous earth filter to remove insoluble impurities therein, and then the hesperidin extraction mixture is concentrated by a low-temperature vacuum evaporator to evaporate 70% to 80% of water, and the concentrated solution is cooled to 0 to 3° C. and allowed to stand for 10 hours to allow hesperidin to crystallize and precipitate, and the remaining residual liquid after the crystals are recovered is returned to the extraction tank for repeated use 2 to 3 times.

5. The method for progressive extraction of citrus peel according to claim 1, characterized in that: In the step E, an ultrafiltration device is used to separate the pectin extract, and the ultrafiltration separation operation process parameters are: ultrafiltration membrane pore size 1-50nm, feed liquid temperature 60°C-65°C, operating pressure 0.50-0.56Mpa, and ultrafiltration feed liquid circulation volume 8-12 times the ultrafiltration separation capacity; water in the pectin extract is separated through the ultrafiltration membrane, and pectin and activated carbon are retained by the ultrafiltration membrane to become a pectin concentrate containing activated carbon, and the pectin concentrate is filtered again through a diatomaceous earth filter to remove the activated carbon therein, so as to obtain liquid pectin.

6. A method for progressive extraction of citrus peel according to any one of claims 1 to 5, characterized in that: Before the citrus peels are crushed in step A, citrus peel essential oil is extracted, citrus juice is squeezed, the core is separated and the peels are crushed. The specific method steps are as follows: A1 Peel essential oil extraction: The citrus fruit is peeled by a peel grinding machine to destroy the surface tissue cells of the citrus peel, so that the peel essential oil is fully released from the peel cells, and the emulsion containing the peel essential oil is recovered. The emulsion containing the peel essential oil is centrifuged to obtain the citrus peel cold-pressed essential oil; A2 citrus juice extraction: the citrus after the peel essential oil is removed in step A1 is juiced by a juicer, and the obtained citrus juice is used to process citrus juice; A3 Fruit core separation: After the citrus juice is squeezed in step A2, the citrus peel is subjected to fruit core separation, and the citrus core and the citrus peel are separated by stirring and centrifugal action generated by the rotation of the spiral blade, so that the citrus core in the citrus peel is removed; The separated citrus fruit cores are collected and washed with water, and then soaked in 5% hydrogen peroxide at room temperature for 5 minutes, then washed with running softened water for 5 minutes to remove the hydrogen peroxide, and dried to a moisture content of 8% to 10% to obtain the citrus fruit cores; A4 Peel crushing: The citrus peel separated from the core in step A3 is crushed by a crusher. While the citrus peel is being crushed, an equal amount of softened water is sprayed into the crusher. The particle size of the crushed citrus peel is between 10 and 18 mm. The crushed citrus peel is converted into peel pulp, which is then transported to three extraction tanks.

7. A method for progressive extraction of citrus peel according to any one of claims 1 to 5, characterized in that: In the step E, after the pectin extraction is completed, the peel pulp in the three extraction tanks is output to the filter press by a screw pump for dehydration, and is used for dietary fiber production after dehydration. The specific method steps are as follows: F. Preparation of dietary fiber: In the step E, the peel pulp from which pectin has been extracted in the three extraction tanks is output to a filter press by a screw pump for squeezing and dehydration. The peel pulp after squeezing and dehydration by the filter press becomes a peel wet cake, which is washed with softened water at 50°C to 60°C for 2 to 3 times, and decolorized by soaking in a 5% hydrogen peroxide solution at room temperature for 20 to 30 minutes; then washed with flowing softened water to remove hydrogen peroxide, and the citrus peel is filtered and dehydrated again to obtain a citrus peel wet cake again; the citrus peel wet cake is crushed and dried to a moisture content of 6% to 8%, and then activated by screw extrusion technology to make it biologically active, and the extrusion conditions are: feed moisture 191.0 g / kg, terminal temperature 140°C, screw speed 60 r / min, the activated dietary fiber is dried again to a moisture content of less than 10%, crushed and sieved through a 120-mesh filter screen to obtain dietary fiber.

8. A method for progressive extraction of citrus peel according to any one of claims 1 to 5, characterized in that: The citrus peel is the peel of any one of citrus, orange, grapefruit and lemon; the peel is freshly squeezed peel or dried peel.

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