Method for producing pectin from plant raw materials using loop extractor

Abstract

FIELD: food industry.SUBSTANCE: invention relates to a method for producing pectin from plant raw materials. The method for producing pectin from plant raw materials includes a stage of wet grinding of raw materials to a particle size of not more than 3 mm in the presence of acidified water. Then an extraction stage is carried out at pH 1.8–3.0, temperature 25–90°C, for 5–240 min at a hydromodule of 1:15–1:25. A stage of cooling the suspension to 40–65°C and neutralising it to pH 3.3–4.0 is carried out. A stage of pressing and centrifugation is carried out to separate the liquid phase from the solid raw material particles to obtain a liquid pectin extract. Then a stage of membrane ultrafiltration and diafiltration of the liquid pectin extract and a drying stage are carried out. The extraction is carried out in a loop extractor, in the circulation circuit of which there is a circulation pump, a heat exchange device and a static mixer-swirler.EFFECT: increasing the efficiency of pectin extraction by reducing the temperature-acid load on the raw material, reducing processing time and preserving the native properties of pectin biopolymers, increasing the yield of pectin and its gelling ability while reducing energy consumption and resource consumption of the process.1 cl, 1 dwg, 1 ex

Description

[0001] Technical field

[0002] The invention relates to the food, pharmaceutical and biochemical industries and can be used in the industrial production of pectin from plant raw materials, such as apple and citrus pomace, sugar beet pulp, sunflower baskets, etc., by acid extraction.

[0003] Technology Level

[0004] Pectic substances are found in the tissues of land plants and some algae, where they are present primarily as insoluble protopectin in the middle lamellae and matrix of primary cell walls. Protopectin is converted into soluble pectin by hydrolysis of the cellular structures with water acidified with mineral acids (HCl, H2PO4, H2SO4, HNO3, etc.) or organic acids (oxalic, citric, lactic, etc.). Dried pectin is a powder ranging in color from white to gray-brown (depending on the source and degree of purification). The most important property of pectin, which determines its use in the food industry (food additive E440), is its ability to form gels (gelling). Due to its pronounced complexing properties in relation to heavy and radioactive metal ions, pectin is also widely used in the production of functional foods, including preventative and therapeutic products.

[0005] Problems with existing technologies: High temperatures and acid concentrations, as well as the significant duration of hydrolysis and extraction in traditional methods, lead to pectin depolymerization (breakdown of glycosidic bonds) leading to its breakdown into galacturonic acid. This degrades the native properties of pectin biopolymers—their gelling and complexing properties are reduced, and the yield of the target product decreases. One way to address these shortcomings and eliminate "harsh" hydrolysis regimes is to use equipment that improves mass transfer in the "pectin-containing raw material - extractant" system and, consequently, reduces the time of exposure to acids and temperature.

[0006] To intensify mass transfer and homogenize the medium, a loop extractor is proposed. A pump continuously circulates the plant material suspension in the loop extractor to maintain a homogeneous reaction mixture. To regulate the reaction temperature, the loop extractor is equipped with a heat exchanger, such as a tube-in-tube type, a built-in shell-and-tube heat exchanger, or a heating / cooling jacket. Using a loop extractor intensifies hydrolysis reactions by improving contact between the raw material and the acid and ensuring uniform heating, thereby reducing extraction and hydrolysis times. This, in turn, reduces the degree of acid and thermal exposure (and, consequently, pectin degradation), as well as reduces the volume of extraction equipment, the amount of reagents, and the volume of wastewater generated.

[0007] A known method for producing pectin (patent RU 2339395 C1, published November 27, 2008) involves extracting pectin substances from citrus peels with distilled water under the influence of ultrasound at a frequency of 30 kHz and an intensity of 23-27 W / cm² at a temperature of 29-33°C, followed by drying the pectin extract and isolating the pectin. The main disadvantages of this method are the low pectin yield and the high energy consumption of the process when scaling up to an industrial level, as hydrolysis is carried out without acids (only with water), and significant ultrasonic power is required for effective extraction.

[0008] A known method for producing pectin from sugar production waste (patent RU 2798564 C1, published June 23, 2023) involves obtaining pectin from sugar beet pulp. The method involves drying and grinding the pulp, extracting with a citric acid solution, filtering and pressing the extract, adding 95% ethanol to the filtrate, filtering the resulting mixture, then isolating and precipitating the pectin in a centrifuge, and drying the precipitated pectin. The spent ethanol is sent for recovery by distillation, and the solid extraction waste is sent for torrefaction (thermal drying). A disadvantage of this method is the use of a large volume of ethyl alcohol. On an industrial scale, this leads to increased costs and a higher explosion and fire hazard class due to the flammability of ethanol vapor. In addition, the multi-stage precipitation-washing operation complicates the process flow diagram.

[0009] A known method for producing a pectin preparation from plant raw materials (patent RU 2066962 C1, published on February 23, 1999). This method involves hydrolysis-extraction of pectin-containing raw materials by cavitation treatment in a hydroacoustic extractor-disintegrator at a cavitation index of K = 0.8-1.9. The resulting pulp is separated into liquid and solid phases in a centrifugal force field; the liquid phase is additionally subjected to microfiltration, and the filtrate is concentrated by ultrafiltration (membranes on a solid support). The extract is then concentrated in a vertical double-casing direct-flow-circulation film vacuum evaporator and dried. The main disadvantages of this method are the difficulty in maintaining a stable cavitation regime and the high energy intensity of the process. The cavitation unit requires precise parameter maintenance, and deviations lead to a decrease in extraction efficiency. In addition, despite membrane purification, harsh hydrolysis conditions can cause partial degradation of pectin.

[0010] A known method for producing pectin extract (patent RU 2080081 C1, published on May 27, 1997) involves the use of electroactivated water for the hydrolysis-extraction of pectin substances. After extraction, the pectin extract is spray-dried at a drying agent temperature of 80-180°C. The resulting dry pectin extract (powder) is then treated with a mixture of ethanol and electroactivated water (the first purification stage), and then additionally with 96% ethanol (the second purification stage). The pectin purified in this way is dried and ground. The main disadvantages of this method are the high energy consumption of obtaining electroactivated water and its unstable pH over time, the need for spray drying at high temperatures (which degrades the quality of the pectin and increases energy costs), and the use of large volumes of alcohol. All this increases the cost of the process and reduces its technological effectiveness.

[0011] The closest analogue is the method for obtaining pectin (patent RU 2610312 C1, IPC C08B 37 / 06, published on 09.02.2017). The method involves extracting pectin-containing pomace with a solution of food or mineral acid with a pH of 0.8-3.2 and a hydromodulus of 1: (15-45) for 1-6 hours at a temperature of 70-95°C, filtering the resulting extract and purifying it. Then, the extract is concentrated in a cascade of ion-exchange and adsorption columns (sequentially cation-exchange resin AMBERLITE® FPC23 H, anion-exchange AMBERLITE® FPA90 Cl and non-selective adsorption AMBERLITE® FPX66) to remove ballast substances. Next, ultrafiltration and diafiltration are performed through polymer membranes with a molecular weight cutoff of 20-100 kDa. The purified pectin solution is dried at 45-95°C—either in vacuum belt dryers or by spray drying—to produce pectin powder, which is then ground.Disadvantages of the closest analogue: the need to maintain fairly stringent extraction conditions (high temperatures up to 95°C, a very acidic pH of ~1, and extraction times up to 6 hours) due to the lack of specialized mass transfer intensification devices. This increases the load on the raw material and can partially reduce the quality of the pectin. Furthermore, the numerous additional purification stages—ion exchange and adsorption—complexify the process, require expensive reagents and equipment, and increase its duration and cost. Therefore, even the modern analogue of RU 2610312 C1 retains potential for improvement: reducing the temperature and acid load and extraction time, simplifying the purification process, and saving energy during drying.

[0012] Essence of the invention

[0013] The objective of the invention is to develop an effective method for obtaining pectin that ensures high yield and quality of the product while simultaneously reducing energy consumption and shortening the process time by optimizing the conditions of the hydrolysis-extraction stage and the subsequent stages of purification and drying.

[0014] The technical result achieved by the claimed method: increasing the efficiency of pectin extraction by reducing the temperature-acid load on the raw material, reducing the processing time and preserving the native properties of pectin biopolymers, which is expressed in an increase in the yield of pectin and its gelling ability, while simultaneously reducing energy consumption and resource costs of the process (elimination of organic solvents, reduction of stages).

[0015] The claimed method utilizes a loop extractor, which ensures intensive circulation and mixing of the plant material suspension with the extractant, promoting uniform distribution of the reagents and active mass transfer. The extractor is additionally equipped with a heat exchanger to precisely maintain the temperature within optimal limits and a static mixer-swirler, which increases flow turbulence and intensifies contact between the solid and liquid phases.

[0016] Achieving the specified technical result is ensured by the following combined stages of a method for producing pectin from various plant materials. The original plant material is ground in the presence of acidified water to a particle size of no more than 3 mm. An aqueous suspension of the ground material is fed to a loop extractor, where hydrolysis occurs at a pH of 1.8-3.0 and a temperature of 25-90°C for 5-240 min, with a hydromodulus of 1:15-1:25. This is followed by cooling and neutralization of the suspension to 3.3-4.0, separation of the liquid extract by pressing, clarification, membrane filtration, concentration, and drying of the pectin extract.

[0017] The combination of the specified design and technological solutions ensures accelerated destruction of the cellular structures of the raw materials, improved extraction of pectin from the intercellular matrix, a reduction in the risk of depolymerization and degradation of pectin molecules, improvement of the gelling and sorption characteristics of the resulting product, as well as an increase in the overall energy and resource efficiency of the process.

[0018] Thus, the claimed technical solution allows for a significant improvement in the technical and economic performance of pectin production and ensures the achievement of a new level of technological efficiency.

[0019] Example of a specific implementation of the method

[0020] Example 1. Pectin was extracted from 2,500 g of sugar beet pulp (granules <4 mm, without separation of fine fractions before hydrolysis) under pilot-scale conditions. An aqueous nitric acid solution was used as the extractant: HNO3 concentration, hydromodulus 1:19. This corresponds to 46125 g of water and 1375 g of HNO3 per 2,500 g of raw material. Extraction was carried out in a loop extractor with continuous suspension circulation at 50°C (hot water was supplied to the extractor's built-in heat exchanger) for 30 min. After this time, to stop the hydrolysis reactions and prevent depolymerization of pectin, the wort (reaction mass) was quickly cooled to 40°C by feeding cold water into the extractor heat exchanger, and the pH was brought to 3.0 by adding a 5% NaOH solution with continued stirring.

[0021] After hydrolysis, the pectin concentration in the liquid phase of the wort was 1.0% (by weight). The liquid phase (pectin extract) was separated from the wort using a Bucher HPL207 hydraulic press with a W08-570 filter element. Using filter pressing before centrifugation significantly reduces the load on the subsequent separation process. Pressing yielded 38,500 g of filtrate (pectin extract) and 11,500 g of dehydrated pomace. The total yield of soluble pectin from the raw materials was over 90% (of the estimated pectin content in the original pulp).

[0022] The resulting pectin extract was then collected in a buffer tank and passed through a high-performance disc centrifuge to remove fine suspended particles. The wort turbidity before centrifugation was 190 NTU (nephelometric turbidity units), and after centrifugation it was 78 NTU, indicating effective clarification.

[0023] Pectin purification and concentration were performed on a membrane unit by sequential ultrafiltration and diafiltration. Ceramic UF membranes with a cutoff threshold of 150 kDa were used. The process pressure was maintained at 0.2 MPa and the temperature at 20°C. In ultrafiltration mode, a retentate with a pectin concentration of 1.5% by weight was obtained. Then, during diafiltration, water was continuously added to the retentate recirculation loop as the permeate was withdrawn. A total volume of water equal to the volume of the original extract was added (diafiltration coefficient = 1). After completion of diafiltration, the pectin concentration in the retentate was 3.0% by weight. The mass of the retentate sent for drying was 8850 g.

[0024] The pre-cleaned pectin extract (retentate) was then concentrated in a falling-film tubular evaporator equipped with a mechanical vapor recompressor (MVR). During evaporation, water vapor evaporated from the pectin extract is compressed by the compressor, resulting in an increase in vapor temperature. This heated, compressed vapor is returned to the evaporator's heat exchanger and used to heat the feed solution (from which the vapor was obtained). The use of a MVR significantly reduces the consumption of fresh heating steam and improves the energy efficiency of the evaporation process. At this stage, the pectin extract was concentrated to 8% dry matter by weight and sent to a buffer tank. The mass of the extract after the evaporator was 2950 g.

[0025] In the final stage, the concentrate was dried in a laboratory drum dryer. The drum surface temperature did not exceed 70°C. The pectin was dried to a dry matter content of 90%. The mass of the resulting dry pectin was 221.25 g. Thus, the total pectin yield from 2.5 kg of wet beet pulp (80% moisture content) was approximately 8.8% relative to the absolutely dry weight of the raw material. The resulting pectin is a light-brown powder with no foreign odor and dissolves well in hot water. When tested for gelling ability (with the formation of a sugar-acid gel), the samples showed a result 10% higher than a pectin sample obtained using the traditional acid-alcohol method from the same raw material.

[0026] Technical and economic indicators: The proposed method for pectin production using a specially designed loop extractor demonstrates significant and experimentally confirmed improvements in performance compared to known technologies. Comparative tests conducted in parallel with a standard tank extractor (without circulation, all other conditions being equal) showed:

[0027] - increase in pectin yield by 15%;

[0028] - increasing the gelling capacity of the obtained pectin by 10%;

[0029] - reducing process energy consumption by 20%;

[0030] - Reducing extraction time by 25%.

[0031] Thus, the claimed solution radically improves the technical and economic indicators of pectin production, significantly increases the quality of the target product and ensures the achievement of a fundamentally new level of technological efficiency, surpassing all known analogues.

[0032] Description of drawings

[0033] Figure 1 schematically shows a loop extractor 1 with an integrated shell-and-tube heat exchanger, a circulation pump, and a static mixer-swirler, used in the claimed method. The extractor is a circulation loop comprising a pump 2, a static mixer-swirler 3, and an integrated shell-and-tube heat exchanger 4.

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