CN-117088996-B - Low-ester pectin with high gelation degree and preparation and application thereof in gel

CN117088996BCN 117088996 BCN117088996 BCN 117088996BCN-117088996-B

Abstract

The invention belongs to the technical field of pectin, and discloses low-ester pectin with high gelation degree, and preparation and application thereof in gel. The preparation method of the low-ester pectin with high gelatinization degree comprises the steps of 1) mixing citrus peel residues with water, adjusting the pH to 1.5-2, extracting at 65-75 ℃, centrifuging, collecting supernatant, carrying out alcohol precipitation washing, filtering, drying and crushing to obtain primary pectin, 2) redissolving the primary pectin, adjusting the pH to 0.5-1.1, reacting at 40-60 ℃, carrying out alcohol precipitation washing, drying and crushing to obtain the low-ester pectin. The method is simple and easy to operate, saves cost and is suitable for industrial production, the prepared low-ester pectin keeps a relatively complete pectin original structure, the esterification degree is 25% -35%, the gelatinization degree is 120% -150, and the low-ester pectin is remarkably superior to low-ester pectin prepared by an alkaline method and an enzymatic method. The low-ester pectin is used for preparing gel, and the formed sugarless gel and sugar alcohol gel have higher hardness and water retention rate.

Inventors

QI JUNRU
WU CHUNLIN
LIAO JINSONG

Assignees

华南理工大学

Dates

Publication Date: 20260505
Application Date: 20230811

Claims (4)

1. A preparation method of low-ester pectin with high gelation degree is characterized by comprising the following steps: (1) Mixing citrus peel residues with water, adding acid to adjust the pH to 1.5-2, extracting at 65-75 ℃, centrifuging, taking supernatant, performing alcohol precipitation washing, filtering, drying and crushing the precipitate to obtain primary pectin; (2) Re-dissolving the primary pectin obtained in the step (1), adding acid to adjust the pH value to 0.5-0.9, reacting at 40-60 ℃, precipitating with alcohol, washing, drying and crushing the precipitate to obtain low-ester pectin; The extraction time in the step (1) is 1-2.5 h; The reaction time in the step (2) is 60-72 h; The citrus peel slag in the step (1) is one or more of lemon peel slag, orange peel slag, pomelo peel slag and orange peel slag, wherein the mass ratio of the citrus peel slag to water is 1 (20-30); The extraction in step (1) is carried out under stirring; The centrifugation in the step (1) means centrifugation at 8000-10000 rpm for 10-20 min; the step (2) of re-dissolving refers to adding primary pectin into water to enable the pectin concentration to be 2-3wt%; The precipitating agent for alcohol precipitation in the step (1) is ethanol solution, the volume concentration of the ethanol solution is more than or equal to 95%, the volume ratio of the supernatant to the ethanol solution is 1 (1-3), the precipitating time is 0.5-1.5 h, and the washing times are 1-3 times; the acid in the step (1) and the step (2) is at least one of nitric acid, oxalic acid, hydrochloric acid and citric acid respectively; The drying in the step (1) and the step (2) is respectively blast drying, rake drying or fluidized bed drying, the drying temperature is 50-65 ℃, and the drying time is 1-4 hours; The precipitating agent for alcohol precipitation in the step (2) is ethanol solution, the volume concentration of the ethanol solution is more than or equal to 95%, the volume ratio of the supernatant to the ethanol solution is 1 (1-3), the washing times are 2-3 times, the pH value of a precipitating system is regulated to 3.5-4 by adopting a regulator before washing the 2 nd time or 3 rd time of alcohol, and then the precipitating system is kept stand for 0.5-1.5 hours, wherein the regulator is ammonia water, sodium hydroxide or sodium carbonate solution; The primary pectin has an esterification degree of 55% -65%, a molecular weight of 500-600 kDa and a gelation degree of 200-220; the esterification degree of the low-ester pectin is 25% -35%, and the gelation degree is 120% -150.
2. The method of claim 1, wherein the low-ester pectin is used to prepare a gel.
3. The method of claim 2, wherein the gel is prepared by re-dissolving low-ester pectin, adjusting the pH of the pectin solution with buffer solution, boiling at high temperature, adding sugar alcohol or calcium chloride solution, and standing to obtain sugar alcohol gel or sugarless gel; The esterification degree of the low-ester pectin is 25% -35%, and the mass concentration of the pectin solution after redissolution is 1% -2%; The buffer solution is a mixed solution of 60wt% of citric acid solution and 2.5M of sodium hydroxide solution, and the volume ratio of the 60wt% of citric acid solution to the 2.5M of sodium hydroxide solution is 3:1; the pH is adjusted to 3-3.3; After the calcium chloride solution is added, the content of calcium ions in a final gel system is 50-60 mg/g pectin; the standing step is to cool the thermal gel to room temperature and then place the thermal gel at 20-30 ℃ for 24h.
4. The use of a high-gelling low-ester pectin obtained by the process according to claim 1, characterized in that: the low-ester pectin with high gelatinization degree is applied to jelly, jam and soft sweets.

Description

Low-ester pectin with high gelation degree and preparation and application thereof in gel Technical Field The invention belongs to the technical field of pectin preparation, and particularly relates to a high-gelation low-ester pectin, a preparation method thereof and application thereof in sugarless gel and sugar alcohol gel. Background Pectin is a structurally complex anionic polysaccharide that is widely found in the intercellular layer and primary walls of higher plant cell walls. Pectin consists mainly of three domains, including HG, RG-I, RG-II. Pectin is classified into high-ester pectin (DE. Gtoreq.50%) and low-ester pectin (DE < 50%) based on the number of ester groups on HG main chain. Pectin is widely used as a food additive in the food fields of jam, jelly, candy and the like. In addition, pectin can be used as bioactive substances in the field of pharmacy by reducing blood cholesterol, inhibiting atherosclerosis, etc. The gel ability of pectin is of great significance to the structure adjustment and sensory perception of pectin-added foods such as jams, jellies and candies. Gel strength is therefore a great important criterion for measuring pectin quality. Different types of pectins tend to have different gel behaviour and mechanisms. High ester pectin is required to form a gel under a relatively severe environment (high acid and high sugar) by virtue of hydrophobic forces and hydrogen bonds between methoxy groups in the pectin chain. The low-ester pectin provides more binding sites for calcium ions due to the increase of carboxyl content in the pectin chain, and is more beneficial to forming a stable eggshell structure. Even at a broad acidity range, even under at least sugar or sugarless conditions, low ester pectin forms a gel with calcium alone. And the lower the esterification degree of the low-ester pectin is, the more favorable the formation of a gel permeation network structure is. Therefore, compared with high-ester pectin, the low-ester pectin has greater advantages in the application aspect of gel performance, and accords with the concept of healthy diet of consumers. Pectin obtained by primary extraction of citrus peel residues is mostly high-ester pectin through detection. To expand its application, high ester pectins are usually subjected to transesterification by chemical and biological methods. The chemical method comprises acid treatment and alkali treatment, wherein the alkali treatment has the most remarkable effect of reducing the ester, but the molecular weight of pectin is greatly reduced due to the beta-elimination reaction in the process of reducing the ester, and the pectin structure is destroyed so as not to form gel or the formed gel degree is lower. Biological methods usually use biocatalysts to assist in reducing the ester by using the methylester, however, in the mass industrialized production, the enzyme consumption greatly increases the production cost, so that the application of the enzyme method in the industry is limited. However, these methods of reducing esters focus on the reduction of the degree of esterification alone, and have low interest in the application value of pectin after its ester reduction. The application value of low-ester pectin is closely related to the gel property. The low-ester pectins on the market are generally defined only in terms of the degree of esterification, and their most important application property, gel properties, is often ignored. The gel properties of low-ester pectins are important in different fields of application. The low-ester pectin with good application value has the gelatinization degree of over 110 on the basis of meeting the esterification degree of less than 50 percent. In other words, the gel of the low-ester pectin does not reach a certain gelatinization degree or does not have the gelatinization property, and the application value of the gel is greatly reduced. For example, the dairy industry mainly utilizes the gel properties of low-ester pectins to apply low-ester pectins in stirred yogurt, and is consumed in large quantities. Therefore, the research of low-ester pectin cannot only pay attention to the esterification degree range, and the gel performance is an important standard for measuring the industrial application of the low-ester pectin. The invention is based on the low-ester pectin with the same esterification degree category, ensures that the pectin has good gel performance, and reaches the product application standard. Disclosure of Invention In view of the above drawbacks and deficiencies of the prior art, a primary object of the present invention is to provide a low-ester pectin with a high degree of gelation and a process for preparing the same. It is a further object of the present invention to provide the use of a low ester pectin as described above. The low-ester pectin is used for preparing sugarless gel and/or sugar alcohol gel. The low-ester pectin disclosed by the invention is also app