阅读说明：本技术 一种利用果渣制备低甲氧基果胶的方法 (Method for preparing low-methoxyl pectin by using pomace ) 是由 陈小举 于 2019-11-25 设计创作，主要内容包括：一种利用果渣制备低甲氧基果胶的方法,包括：(1)制备黑曲霉液体种子,(2)黑曲霉固体发酵,(3)制备复合酶,(4)复合酶处理果渣,(5)酸水解与提取,(6)乙醇沉淀与过滤,(7)清洗与烘干。本发明以黄桃、梨、苹果、蓝莓、橙、柚子等榨汁后的果渣为原料,固体发酵黑曲霉制备复合酶,以复合酶处理果渣以实现细胞壁溶解和果胶脱脂；然后通过酸解、醇沉、清洗、烘干等制备得到低甲氧基果胶。(A method for preparing low methoxyl pectin by using pomace comprises the following steps: (1) preparing aspergillus niger liquid seeds, (2) performing aspergillus niger solid fermentation, (3) preparing a complex enzyme, (4) treating pomace by the complex enzyme, (5) performing acid hydrolysis and extraction, (6) performing ethanol precipitation and filtration, and (7) cleaning and drying. The method takes the squeezed pomace of yellow peaches, pears, apples, blueberries, oranges, grapefruits and the like as raw materials, prepares compound enzyme by solid fermentation of aspergillus niger, and treats the pomace with the compound enzyme to realize cell wall dissolution and pectin degreasing; then preparing the low methoxyl pectin through acidolysis, alcohol precipitation, cleaning, drying and the like.)

1. A method for preparing low methoxyl pectin by using pomace is characterized by comprising the following steps: comprises the following steps:

step 1: adding sterile water into the aspergillus niger strain preservation inclined plane, scraping off spores in the inclined plane by using an inoculation shovel to prepare strain suspension; inoculating the strain suspension into the sterilized liquid seed culture medium according to the inoculum size of 2.5-5%, and culturing for 4-6d in a shaking table at the temperature of 30-35 ℃ and the rotation speed of 100-;

step 2: in a purification environment with the air cleaning level of 1 ten thousand, uniformly mixing Aspergillus niger liquid seeds with a solid culture medium subjected to steam sterilization according to the inoculation amount of 1-5% at the temperature of 25-30 ℃, then paving the mixture into a tray with the thickness of 1.5-2.5cm, keeping the relative humidity of the environment at 60-75%, and fermenting for 5-7d to obtain a solid fermentation product;

and step 3: adding distilled water with the mass 9-12 times of that of the solid culture medium into the solid fermentation product, soaking and filtering to obtain a filtrate, namely a crude enzyme solution; adding ammonium sulfate into the crude enzyme solution at the temperature of 25 +/-5 ℃, standing, filtering to obtain a precipitate, and cleaning the precipitate with purified water to obtain a complex enzyme obtained by fermenting aspergillus niger;

and 4, step 4: adding purified water 4-5 times the weight of the pomace, adding the complex enzyme prepared in the step 3 with the pomace weight of 0.5-1.0%, keeping the temperature at 40-45 ℃, and stirring at the rotating speed of 45-60r/min for 60-90min to obtain pomace mixed solution;

and 5: adding hydrochloric acid into the mixed liquid of the pomace, adjusting the pH value to 2.0-2.5, then heating and keeping the temperature at 90-92 ℃, and stirring at the rotating speed of 30-60r/min for 60-90 min; filtering the obtained solution to obtain filtrate as pectin extracting solution;

step 6: adding ethanol into the pectin extractive solution to make the ethanol content of the mixed solution 50-65%, and standing for 60-90 min; filtering the mixed solution by a 60-80 mesh filter screen, and collecting solid retentate;

and 7: repeatedly washing the solid retentate with purified water for 3-5 times, drying the solid retentate under the environment of-0.09 MPa to-0.10 MPa of vacuum gauge pressure and 60-65 ℃ until the water content is less than or equal to 5%, and crushing to obtain the low methoxyl pectin.

2. The method for preparing low methoxyl pectin by using pomace according to claim 1, wherein: the fruit residue is at least one of fresh yellow peach, pear, apple, blueberry, orange and grapefruit, and is residue obtained after fruit juice is squeezed.

3. The method for preparing low methoxyl pectin by using pomace according to claim 1, wherein: the raw material formula of the liquid seed culture medium comprises the following raw materials in percentage by mass: 25-30% of cane sugar, 0.25-0.50% of ammonium sulfate, 0.15-0.25% of dipotassium hydrogen phosphate, 0.15-0.25% of sodium chloride, 0.05-0.10% of ferrous sulfate and the balance of purified water, wherein the total content is 100%.

4. The method for preparing low methoxyl pectin by using pomace according to claim 1, wherein: the raw material formula of the solid culture medium comprises the following raw materials in percentage by mass: 40-50% of pomace, 10-15% of bran, 10-15% of corn flour, 5% of soybean meal, 0.5% of ammonium sulfate and 0.25% of dipotassium hydrogen phosphate, wherein the total content is 100%; the preparation method of the solid culture medium comprises the following steps: weighing the raw materials according to the raw material formula of the solid culture medium, mixing uniformly, filling into a non-woven bag, sterilizing for 25-30min by using 120-grade 125-DEG saturated steam, and naturally cooling to room temperature in a purified environment with the air cleaning level of 1 ten thousand for later use.

Technical Field

The invention belongs to the technical field of deep processing of agricultural products, and relates to a method for preparing low-methoxyl pectin by using pomace.

Background

Pectin is a non-toxic natural food additive and is an important component of plant cell walls. Pectin is a plant polysaccharide polymer consisting essentially of partially methyl-esterified galacturonic acid units, which are generally classified into two main groups according to their methoxy content: high Methoxyl Pectin (HMP), Low Methoxyl Pectin (LMP).

HMP generally refers to pectin having a degree of esterification or methyl esterification greater than 50%, i.e., a methoxyl content greater than 7%, LMP refers to pectin having a degree of methyl esterification between 25-50%, i.e., a methoxyl content less than 7%, HMP gels only when the soluble solids are above 55% and the pH is in the range of 2.0 ~ 3.5.5, and is primarily used in the production of high-sugar foods.

LMP is not completely limited by pH value and sugar degree (eutectic), and has low requirement on gel condition. The rate of gel formation by LMP increases with decreasing degree of methyl esterification of the pectin. The LMP has obvious significance in meeting the requirements of people on low-sugar, low-calorie and low-sweetness foods. In recent years, the demand for low-sugar foods has increased significantly due to the increasing number of obese and diabetic patients. LMP has resulted in a great market demand for LMP due to its unparalleled advantages as an edible gum for low-sugar foods.

Aspergillus niger, Deuteromycotina, class Hyphomycetes, order Hyphomycetales, family Moniliaceae, a common species of fungi of the genus Aspergillus. Widely distributed throughout the world in foodstuffs, vegetable products and soils. Is an important fermentation industrial strain, and can produce amylase, acid protease, cellulase, pectinase, glucose oxidase, citric acid, gluconic acid, gallic acid and the like.

Disclosure of Invention

The invention aims to provide a method for preparing low-methoxyl pectin by using pomace.

In order to achieve the above objects and other related objects, the present invention provides the following technical solutions: a method for preparing low methoxyl pectin by using pomace comprises the following steps:

step 1: adding sterile water into the aspergillus niger strain preservation inclined plane, scraping off spores in the inclined plane by using an inoculation shovel to prepare strain suspension; inoculating the strain suspension into the sterilized liquid seed culture medium according to the inoculum size of 2.5-5%, and culturing for 4-6d in a shaking table at the temperature of 30-35 ℃ and the rotation speed of 100-;

step 2: in a purification environment with the air cleaning level of 1 ten thousand, uniformly mixing Aspergillus niger liquid seeds with a solid culture medium subjected to steam sterilization according to the inoculation amount of 1-5% at the temperature of 25-30 ℃, then paving the mixture into a tray with the thickness of 1.5-2.5cm, keeping the relative humidity of the environment at 60-75%, and fermenting for 5-7d to obtain a solid fermentation product;

and step 3: adding distilled water with the mass 9-12 times of that of the solid culture medium into the solid fermentation product, soaking and filtering to obtain a filtrate, namely a crude enzyme solution; adding ammonium sulfate into the crude enzyme solution at the temperature of 25 +/-5 ℃, standing, filtering to obtain a precipitate, and cleaning the precipitate with purified water to obtain a complex enzyme obtained by fermenting aspergillus niger;

and 4, step 4: adding purified water 4-5 times the weight of the pomace, adding the complex enzyme prepared in the step 3 with the pomace weight of 0.5-1.0%, keeping the temperature at 40-45 ℃, and stirring at the rotating speed of 45-60r/min for 60-90min to obtain pomace mixed solution;

and 5: adding hydrochloric acid into the mixed liquid of the pomace, adjusting the pH value to 2.0-2.5, then heating and keeping the temperature at 90-92 ℃, and stirring at the rotating speed of 30-60r/min for 60-90 min; filtering the obtained solution to obtain filtrate as pectin extracting solution;

step 6: adding ethanol into the pectin extractive solution to make the ethanol content of the mixed solution 50-65%, and standing for 60-90 min; filtering the mixed solution by a 60-80 mesh filter screen, and collecting solid retentate;

and 7: repeatedly washing the solid retentate with purified water for 3-5 times, drying the solid retentate under the environment of-0.09 MPa to-0.10 MPa of vacuum gauge pressure and 60-65 ℃ until the water content is less than or equal to 5%, and crushing to obtain the low methoxyl pectin.

The preferable technical scheme is as follows: the fruit residue is at least one of fresh yellow peach, pear, apple, blueberry, orange and grapefruit, and is residue obtained after fruit juice is squeezed.

The preferable technical scheme is as follows: the raw material formula of the liquid seed culture medium comprises the following raw materials in percentage by mass: 25-30% of cane sugar, 0.25-0.50% of ammonium sulfate, 0.15-0.25% of dipotassium hydrogen phosphate, 0.15-0.25% of sodium chloride, 0.05-0.10% of ferrous sulfate and the balance of purified water, wherein the total content is 100%.

The preferable technical scheme is as follows: the raw material formula of the solid culture medium comprises the following raw materials in percentage by mass: 40-50% of pomace, 10-15% of bran, 10-15% of corn flour, 5% of soybean meal, 0.5% of ammonium sulfate and 0.25% of dipotassium hydrogen phosphate, wherein the total content is 100%; the preparation method of the solid culture medium comprises the following steps: weighing the raw materials according to the raw material formula of the solid culture medium, mixing uniformly, filling into a non-woven bag, sterilizing for 25-30min by using 120-grade 125-DEG saturated steam, and naturally cooling to room temperature in a purified environment with the air cleaning level of 1 ten thousand for later use.

Due to the application of the technical scheme, compared with the prior art, the invention has the advantages that:

the method takes the squeezed pomace of yellow peaches, pears, apples, blueberries, oranges, grapefruits and the like as raw materials, prepares compound enzyme by solid fermentation of aspergillus niger, and treats the pomace with the compound enzyme to realize cell wall dissolution and pectin degreasing; then preparing the low methoxyl pectin through acidolysis, alcohol precipitation, cleaning, drying and the like.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.