RU2055485C1 - Method of preparing low-methoxylated pectin - Google Patents

Abstract

FIELD: food industry. SUBSTANCE: method involves preparing pectin-containing extract from the plant raw, its cooling, alkaline demethoxylation, acidification and isolation of ready product. Pectin-containing extract from the plant raw is prepared by raw washing, its hydrolysis-extraction followed by separation of hydrolyzed mixture for pulp and liquid phase. Additionally, pectin is extracted from pulp for 0.4-0.5 hr at 80-85 C followed by blending liquid phase with pectin extract obtained at the stage of additional extraction. Washing, hydrolysis-extraction and additional extraction were carried out with electroactivated water after electromembrane treatment, total water hardness is 0.005-3.0 mg-eq./l up to 0.8-1.2% pectin substance in ready pectin-containing extract. Cooling is carried out to 15-20 C, alkaline demethoxylation is performed with hydrochloric acid up to pH medium 2.0-3.0. EFFECT: improved method of pectin preparing. 2 tbl

Description

 The invention relates to the production of pectin, used mainly for food, medical and preventive purposes and can be used in the canning, confectionery, bakery industries for the preparation of food products, including medical and preventive and dietary nature, as well as in pharmacology and medicine .

 A known method for producing low methoxylated pectin by treating apple extract with 25% ammonia solution.

The method includes cooling the apple nitrate extract to 15 ^° C, treating it with a 25% ammonia solution in a volume ratio of 20: 1 to provide a pH of 10.3 to 10.5. The demethoxylation reaction proceeds within 0.5 to 4.0 hours. After saponification, the mixture is acidified with nitric acid to pH 1.9 2.0, ethyl alcohol is added in a volume ratio of 1: 1 to precipitate pectin. The obtained pectin is characterized by a degree of methoxylation 62 37
The disadvantage of this method is the length of the demethoxylation process and, therefore, the low productivity of the low methoxylated pectin production line, as well as the need to use aggressive nitric acid both for hydrolysis-extraction of plant materials and for acidification of the extract after demethoxylation and separation of pectin from the concentrate. Nitric acid used in the production and isolation of low methoxylated pectin contributes to the contamination of the target product with nitrate ions in amounts exceeding the maximum allowable concentration. This requires additional expensive pectin purification techniques and complicates the purification process.

The closest in technical essence is a solution process for preparing low methoxyl pectin from plant material by acid extraction last nitric acid, concentrating the extract, cooling it down to 6-8 ^{° C,} the alkali concentrate demethoxylation of NaOH to provide a mixture pH 10,8-11,2 . Upon reaching the desired degree of esterification, the process is stopped by adding nitric acid to a pH of 4.5.

 Pectin is isolated from the concentrate with ethyl alcohol with the addition of nitric acid until a pH of 1.7 to 2.0 is reached.

The disadvantages of this method is the need to use highly concentrated alkali solution, maintaining low temperature extract of 6-8 ^{° C} and aggressive use of nitric acid in step demethoxylation stop process.

The claimed solution differs from the closest analogue in that the pectin-containing extract from plant material is obtained by washing the raw material, hydrolyzing and extracting it, followed by separation of the hydrolyzed mixture into pomace and liquid phase, additional extraction of pectin from pomace for 0.4 0.5 hours at a temperature process 80 85 ^about With and blending the liquid phase with a pectin extract obtained at the stage of additional extraction, while washing, hydrolysis-extraction and additional extraction carry out EAW, about marching electro processing, general rigidity mgekv 0.005 3.0 / l to achieve in the final pectin extract 0.8-1.2% of pectic substances are cooled to 15 ²⁰ ° C, the alkaline demethoxylation is carried out at pH 8.0 10.0 and acidification is carried out with hydrochloric acid until the pH of the medium reaches 2.0 3.0.

 Thus, the claimed method meets the criterion of "novelty."

 However, no known technical solution noted the use of additional extraction of the hydrolyzed feed with electroactivated water and blending of extracts to accelerate the process of alkaline demethoxylation by 3-20 times, using a weaker alkali solution with a pH of 8-10.

 This allows us to conclude that the proposed technical solution meets the criterion of "significant differences".

 Alkaline demethoxylation of pectin in the extract proceeds as follows. The glycosidic bonds of polyuronides are more labile with respect to alkalis, which leads to an increase in the rate of pectin depolymerization and its destruction.

R-[(COOCH₃)_m-p•(COOH)_n+p]+pCH₃OH
Экспериментально установлено, что ускорение процесса щелочного деметоксилирования согласно предложенного способа осуществляется за счет подготовки пектиновой макромолекулы путем введения в процесс получения пектина дополнительной экстракции сежей порции ЭАВ в течение 0,4 0,5 ч.However, at 15 20 ° ^C the amount of energy is insufficient to activate the chain scission macromolecules and pectin is able to provide a de-esterification reaction. The ongoing demethoxylation process is described by the following equation
R - [(COOCH ₃ ) _m • (COOH) _n ] + pH ₂ O

R - [(COOCH ₃ ) _mp • (COOH) _{n + p} ] + pCH ₃ OH
It was experimentally established that the acceleration of the process of alkaline demethoxylation according to the proposed method is carried out by preparing a pectin macromolecule by introducing into the process of producing pectin an additional extraction of a gray portion of EAW for 0.4 0.5 hours.

Based on model ideas about the apple pectin macromolecule, the latter contains ramnogalacturonan chain sections with side branches from the residues of neutral sugars and galacturonan. Lateral branches are connected to the main chain through the remains of ramnose and, in some cases, xylose. Additional acid pectin extraction at a pH of 1.5-2.5 and a temperature of 80 85 ^{° C} leads to considerable destruction of covalent bonds between residues rhamnose and arabinose, which leads to the isolation of pectin linear molecules with a higher content of polygalacturonic acid and enhances steric factors in further deesterification of pectin. In addition, nucleophilic substitution proceeds in an acidic medium through the stage of protonation of oxygen of the ether group (formation of an oxonium salt), leading to a decrease in the energy of the -CH group. As the energy of the leaving group decreases during the substitution reaction, not only should the reaction rate increase, but also the bond breaking process should prevail over the bond formation process. For less than 0.4 h, it is impractical to conduct the process due to the slow diffusion of EAS into the cells of plant tissue.

___→

+ CH₃OH
Снижение энергии группы -СН₃ приводит к увеличению скорости реакции щелочного деметоксилирования, что снижает вероятность протекания сопряженного процесса деполимеризации пектиновых цепочек по гликозидным связям с образованием двойных связей между С₄ и С₅. Этот процесс регулируется температурным режимом процесса и концентраций щелочи.Over 0.5 h, the onset of acid deesterification and depolymerization of pectin is possible

___ →

+ CH ₃ OH
A decrease in the energy of the —CH ₃ group leads to an increase in the rate of the alkaline demethoxylation reaction, which reduces the likelihood of a conjugated process of depolymerization of pectin chains along glycosidic bonds with the formation of double bonds between C ₄ and C ₅ . This process is regulated by the temperature conditions of the process and alkali concentrations.

 It was experimentally established that at pH less than 8.00, the demethoxylation rate is low due to the lack of the number of hydroxo groups in the extract, which does not allow to obtain pectin with a low degree of esterification (Table 1) for a short period of processing the extract for 5-15 minutes at room temperature . Carrying out the demethylation process at a pH above 10 does not significantly reduce the degree of esterification. At the same time, the purity of pectin deteriorates significantly, the uronide component decreases (Table 1), and, as a result, the binding ability of pectin decreases and the yield of the target product decreases.

 An increase in the processing time of the extract over 15 min both at pH 10.0 and at pH below 8.0 leads to a decrease in line productivity. In the first case, the destruction of pectin macromolecules is deepened due to the breakdown of the pectin chain with prolonged exposure to alkali. In the second case, an increase in the duration of alkali treatment does not lead to significant demethoxylation and to obtain the target product with a given degree of esterification.

 Demethoxylation of pectin extract for less than 5 min is technically impossible.

 The lower limit of pH 8.0 is limited by the low reaction rate due to the low concentration of hydroxyl ions in this case, and the upper pH of 10.0 is a significant acceleration of depolymerization. The acceleration of the process due to an increase in pH is limited by a large acid consumption to establish the initial pH of the extract and deterioration in the quality of pectin, since alkaline demethoxylation is a high-speed process, however, at high pH values, displacement of complex methyl groups of esters is accompanied by depolymerization of pectin chains, leading to destruction of pectin macromolecules and lower quality and yield of pectin.

 The alkali-treated extract is acidified with concentrated hydrochloric acid to the initial pH of the untreated extract. The use of this acid is due to its high degree of dissociation compared to nitric acid, therefore, the rapid neutralization of alkali, as well as the lack of oxidizing ability, leading to the destruction of organic compounds in the extract, including pectin.

The specified method allows to obtain pectin with a degree of esterification of 34.3 54.15
The method is as follows: pectin-containing plant materials, for example, dry apple pressed, washed and subjected to swelling in electroactivated water with a pH of 3.5 at 60 80 ^about C for 20 to 40 minutes, carry out hydrolysis-extraction of EAS with a pH of 1.5 to 2 , 5 at a temperature of 80 85 ^about C for 1.5 2.0 hours. The extract I is drained, the remaining solid plant mass is poured with a fresh portion of EAS at the same temperature for 0.4 0.5 hours for additional extraction. Extract II is drained and blended with extract I.

 Examples of additional extraction at various parameters are given in table 1.

 The toughening of the technological regimes of additional extraction, as well as the creation of milder conditions, should be considered impractical, since according to experimental data, the yield of pectin in this case decreases in the first case due to destruction, in the second due to incomplete extraction of the latter.

In the present process the hydrolysis conducted EAS (electroactivated water) with a pH of 1.85 at ⁸⁰ ° C for 1.75 h. The liquid phase was filtered and the solid portion was poured new EAS pH 1.85 at ⁸⁰ ° C for 0, 45 h

The resulting pectin extract is cooled to 15 20 ^about C and treated with 1 N. caustic soda solution with a pH of 8-10 for 5 to 15 minutes The deesterification reaction was stopped by adding concentrated hydrochloric acid to the reaction mixture until the initial pH of the extract was reached. Next, pectin is precipitated from the extract with 96 alcohol in a ratio of 1: 2.5. The implementation of the proposed method is illustrated by the following examples:
EXAMPLES EXAMPLE 1 100 g of dried apple pomace freed of mechanical impurities with water at room temperature, poured EAS pH 3.0 and a temperature of ⁶⁰ ° C, subjecting the raw material to swell for 20 min, hydrolysis is carried out under the above procedure.

Both portions of the extract (I and II) were combined, filtered, cooled ^to 20 ° C, added 1N. sodium hydroxide solution to a pH of 8.0. Demethoxylation is carried out for 15 minutes, after which the extract is adjusted to the initial pH with concentrated hydrochloric acid. The obtained low methoxylated pectin from the extract is isolated with ethyl alcohol in a ratio of 1: 2. The pectin coagulate is washed with alcohol 1: 0.5 and dried. The degree of esterification of isolated pectin (S. E.) is 54.15%; the ability to retain heavy metal ions (lead) K $\genfrac{}{}{0ex}{}{\text{Rv}}{\text{from}}$ is 82 mg / g pectin.

PRI me R 2. It differs from example 1 in that demethoxylation is carried out at pH 10 for 5 min at 15 ^about C. C. E. the resulting pectin is 33.30 K $\genfrac{}{}{0ex}{}{\text{Rv}}{\text{from}}$ 107 mg / g pectin.

PRI me R 3. It differs from example 1 only in that demethoxylation is carried out at pH 9, a temperature of 17 ^about With for 10 minutes The degree of esterification of the obtained pectin is 34.3% K $\genfrac{}{}{0ex}{}{\text{Rv}}{\text{from}}$ 210 mg / g pectin.

PRI me R 4. Differs from example 1 in that demethoxylation is carried out at a pH of 11.0, a temperature of 10 ^about C for 5 minutes S.E. 32.7 K $\genfrac{}{}{0ex}{}{\text{Rv}}{\text{from}}$ 104 mg / g pectin.

PRI me R 5. Differs from example 1 in that demethoxylation is carried out at pH 7.0, a temperature of 25 ^about With for 20 minutes S.E. 56.9 K $\genfrac{}{}{0ex}{}{\text{Rv}}{\text{from}}$ 76 mg / g pectin.

 Examples 1-5 are summarized in table 2. Data are given for the same pH values of the extract after acidification, equal to 2.5.

Using the proposed method for producing low methoxylated pectin provides the following advantages in comparison with existing methods:
acceleration of the demethoxylation process by 3-20 times;
obtaining pectin with a high ability to bind heavy metal ions (P _in );
an increase in the production of low methoxylated pectin by accelerating the demethoxylation process;
obtaining low methoxylated pectin with a given degree of esterification in the range of 34.30 54.15

Claims (1)

A METHOD FOR PRODUCING A LOW-METHOXILIZED PECTIN, which provides for the preparation of a pectin-containing extract from plant materials, its cooling, alkaline demethoxylation, acidification and isolation of the finished product, characterized in that the pectin-containing extract from plant materials is obtained by washing the raw material, hydrolyzing and extracting it with subsequent extraction liquid phase further extracted pectin from the pomace for 0.4 - 0.5 hours at a process temperature of 85 - 85 ^o C and kupazhirova liquid phase with a pectin extract obtained at the stage of additional extraction, while washing, hydrolysis-extraction and additional extraction are carried out by electroactivated water, which has undergone electromembrane treatment, with a total hardness of 0.005 - 3.0 mg eq / l until the finished pectin-containing extract is reached 0.8-1.2% of pectin substances, cooling is carried out to a temperature of 15-20 ^o C, alkaline demethoxylation is carried out at pH 8-10, and acidification is carried out with hydrochloric acid until a pH of 2-3 is reached.

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