阅读说明：本技术 一种湿法浸泡制备油炸型胶原肠衣的方法 (Method for preparing fried type collagen casing by wet soaking ) 是由 刘飞 钟芳 马宇欣 于哲 李强 陈茂深 夏熠珣 徐菲菲 于 2021-07-14 设计创作，主要内容包括：本发明提供一种湿法浸泡制备油炸型胶原肠衣的方法,其包括如下步骤：绞碎牛皮、一次浸酸、均质、固化、交联、水洗、塑化、干燥回湿得到油炸型胶原肠衣,本发明制备的油炸香胶原肠衣有着口感、粘性和油炸特性显著提高的优点。(The invention provides a method for preparing fried type collagen casings by wet soaking, which comprises the following steps: the fried collagen sausage skin prepared by the method has the advantages of obviously improved taste, viscosity and frying property.)

1. A method for preparing fried collagen sausage casing by wet soaking is characterized in that: the method comprises the following steps:

the pretreated cowhide double-layer skin is crushed and then is crushed at high speed to obtain cowhide pulp;

stirring the mixed solution of the cow hide pulp and the acid liquor to form collagen clusters, and standing;

the collagen clusters are extruded after being homogenized and filtered, and are solidified, crosslinked and washed by air and ammonia gas to obtain a semi-finished product of the casing;

and adding the semi-finished product of the casing into mixed plasticizing liquid containing bicarbonate for plasticizing, and drying and rewetting to obtain the fried type collagen casing.

2. A method for preparing casing of fried type collagen by wet dipping according to claim 1, characterized in that: the mass ratio of the acid liquor to the kraft pulp is 1: 1.

3. A method for preparing casing of fried type collagen by wet dipping according to claim 1, characterized in that: the plasticizing liquid used in the plasticizing process is a mixed aqueous solution of bicarbonate, glycerol and hydroxymethyl cellulose.

4. A method for preparing casing of fried type collagen according to claim 3 by wet dipping, characterized in that: the bicarbonate comprises one or more of ammonium bicarbonate and sodium bicarbonate.

5. A method for preparing casing of fried type collagen according to claim 3 by wet dipping, characterized in that: in the plasticizing liquid, the weight ratio of bicarbonate: sodium dihydrogen phosphate: glycerol: 0.1 to 0.5:0.01 to 0.5:3 to 4:0.5 to 2.

6. The method for preparing casing of fried type collagen according to claim 5 by wet dipping, characterized in that: the drying is three-stage drying.

7. The method for preparing casing of fried type collagen according to claim 6 by wet dipping, characterized in that: the temperature of the three-stage drying is set as a first-stage drying temperature of 90 ℃ for 5 min; the second stage drying temperature is 75 ℃, and the time is 5 min; the three-stage drying temperature is 65 ℃ and the time is 3 min.

8. A method for preparing casing of fried type collagen by wet dipping according to claim 1, characterized in that: the humidity in the rewetting is controlled at 15%.

9. A method for preparing casing of fried type collagen by wet dipping according to claim 1, characterized in that: the crosslinking solution used in the crosslinking was 50 ppm.

10. A method for preparing casing of fried type collagen by wet dipping according to claim 1, characterized in that: the acid solution comprises one or more of hydrochloric acid, citric acid and lactic acid.

Technical Field

The invention relates to the technical field of collagen casing processing, in particular to a method for preparing a fried type collagen casing by wet soaking.

Background

Collagen casings have similar properties to natural casings and are less expensive, so artificial collagen casings are often produced to compensate for the deficiencies in the production of natural casings, and the production processes thereof are classified into a dry process and a wet process. Different from the dry method of firstly swelling, then smashing, drying and shaping, the wet method firstly smashes the collagen fibers, then swells and extrudes the collagen fibers, and then the collagen fibers are soaked in the solution for solidification and reinforcement and are shaped in the soaking process, so that the collagen casing prepared by the wet method is softer and finer in taste compared with the dry method casing.

However, the wet-process collagen casing has not yet performed the same mechanical properties, boiling resistance and frying characteristics as the natural casing in practical use. By soaking the solution containing crosslinking agents such as glutaraldehyde, the mechanical property and the cooking property of the sausage casing can be effectively improved, but the deep-fried property of the sausage casing is increasingly unsatisfactory due to the excessively high degree of crosslinking among collagen fibers, the problems of peeling, easy cracking, difficult biting, and the like occur, the taste is poor, and the practical application cannot be met.

US4233329, US3123481 and the like adopt an aluminum tanning mode to soak the semi-finished collagen casing in solutions of aluminum sulfate, aluminum ammonium sulfate and the like to form a loose collagen fiber network structure, so that the frying property of the casing is improved. Although the soaking mode is wide in application range, and the aluminum tanned collagen casing shows ideal frying mouthfeel and performance when the sausage is fried, excessive intake of aluminum has great harm to human health, and the aluminum is determined as a food pollutant and is limited in use. CN201910529320.9 discloses a preparation method of boiled/fried collagen casing, which is to pretreat the cowhide by adding small molecular polyol, strong oxidant and ferric ion, however, the method has potential toxicity and even causes pollution. At present, the preparation method which is suitable for the preparation process of the wet casing and can obviously improve the fried taste and the performance of the collagen casing is rarely reported, and if a simple, safe and economic technology is provided to solve the problem, the requirement of consumers can be met to a great extent, and the economic benefit is improved.

Disclosure of Invention

This section is for the purpose of summarizing some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. In this section, as well as in the abstract and the title of the invention of this application, simplifications or omissions may be made to avoid obscuring the purpose of the section, the abstract and the title, and such simplifications or omissions are not intended to limit the scope of the invention.

The present invention has been made in view of the above and/or other problems associated with prior art fried collagen casing products.

Therefore, one of the objects of the present invention is to overcome the disadvantages of the prior fried type collagen casing and to provide a method for preparing the fried type collagen casing by wet dipping.

In order to solve the above technical problem, according to an aspect of the present invention, the present invention provides the following technical solutions: a method for preparing fried collagen sausage casing by wet soaking comprises the following steps:

the pretreated cowhide double-layer skin is crushed and then is crushed at high speed to obtain cowhide pulp;

stirring the mixed solution of the cow hide pulp and the acid liquor to form collagen clusters, and standing;

the collagen clusters are extruded after being homogenized and filtered, and are solidified, crosslinked and washed by air and ammonia gas to obtain a semi-finished product of the casing;

and adding the semi-finished product of the casing into mixed plasticizing liquid containing bicarbonate for plasticizing, and drying and rewetting to obtain the fried type collagen casing.

As a preferable embodiment of the method for preparing the fried type collagen casing by wet dipping of the invention, wherein: the mass ratio of the acid liquor to the kraft pulp is 1: 1.

As a preferable embodiment of the method for preparing the fried type collagen casing by wet dipping of the invention, wherein: the plasticizing liquid used in the plasticizing process is a mixed aqueous solution of bicarbonate, glycerol and hydroxymethyl cellulose.

As a preferable embodiment of the method for preparing the fried type collagen casing by wet dipping of the invention, wherein: the bicarbonate comprises one or more of ammonium bicarbonate and sodium bicarbonate. A method for preparing casing of fried type collagen according to claim 3 by wet dipping, characterized in that: in the plasticizing liquid, the weight ratio of bicarbonate: sodium dihydrogen phosphate: glycerol: 0.1 to 0.5:0.01 to 0.5:3 to 4:0.5 to 2.

As a preferable embodiment of the method for preparing the fried type collagen casing by wet dipping of the invention, wherein: the drying is three-stage drying.

As a preferable embodiment of the method for preparing the fried type collagen casing by wet dipping of the invention, wherein: setting the temperature of the three-stage drying to be 90 ℃ for 5 min; the second stage drying temperature is 75 ℃, and the time is 5 min; the three-stage drying temperature is 65 ℃ and the time is 3 min.

As a preferable embodiment of the method for preparing the fried type collagen casing by wet dipping of the invention, wherein: the humidity in the rewetting is controlled at 15%.

As a preferable embodiment of the method for preparing the fried type collagen casing by wet dipping of the invention, wherein: the crosslinking solution used for crosslinking was 50 ppm.

As a preferable embodiment of the method for preparing the fried type collagen casing by wet dipping of the invention, wherein: the acid solution comprises one or more of hydrochloric acid, citric acid and lactic acid.

The invention provides a method for preparing fried type collagen casings by wet soaking, which has the following advantages:

(1) the prepared fried type collagen casing has the advantages that the bicarbonate contained in the casing generates gas under the conditions of heating and high temperature, uniform air holes are formed on the surface and inside of the casing, the casing is soft and transparent, and a loose and porous structure and excellent fried mouthfeel are obtained after frying;

(2) the bicarbonate is added into the mixed plasticizing liquid prepared by the invention, and is driven by osmotic pressure to adsorb and enter the inside of the casing in the plasticizing process so as to play a role; in addition, the addition of the acid salt can further adjust the gas production speed of the bicarbonate, eliminate peculiar smell and ensure that the collagen casing can obtain better mouthfeel;

(3) the fried collagen casing prepared by the invention is prepared by a wet process, the casing is soft and delicate in taste, uniform in thickness, soft and strong in plasticity in the frying process, and has high meat viscosity, and the fried casing is not easy to fall off;

(4) the method is established on the basis of the original sausage casing preparation process, only improves the formula of materials in the production process, does not add other steps, aims to improve the frying characteristic of the sausage casing under the condition of not influencing other application properties of the sausage casing prepared by the existing process, is simple and convenient to operate in production, and has stronger applicability.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts. Wherein:

FIG. 1 is a pictorial representation of sausages prepared from collagen casings prepared in example 1 and comparative example 1 after frying for 10 min;

wherein, a is a real object diagram of the roasted sausage prepared by the sausage casing prepared by the prior art after being fried for 10min, and b is a real object diagram of the roasted sausage prepared by the sausage casing prepared by the invention after being fried for 10 min;

FIG. 2 is a schematic view of the collagen casing prepared in example 1 and comparative example 1 after frying for 10 min;

wherein, a is a real object diagram of the prepared sausage casing prepared by the prior art after being fried for 10min, and b is a real object diagram of the prepared sausage casing prepared by the invention after being fried for 10 min;

FIG. 3 is a surface microstructure SEM image of casings prepared in examples 1, 2 and comparative example 1;

FIG. 4 is a cross-sectional microstructure SEM image of casings prepared in examples 1, 2 and comparative example 1;

FIG. 5 is a graph showing the results of measurement of the frying shrinkage of casings obtained in examples 1 to 6 and comparative examples 1 to 4;

FIG. 6 is a graph showing the measurement results of the boiling shrinkage of casings obtained in examples 1 to 6 and comparative examples 1 to 4;

FIGS. 7 and 8 are graphs showing the results of measuring mechanical properties of casings obtained in example 6;

FIG. 9 is a graph showing the results of thickness measurement of casings prepared in example 6;

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, specific embodiments thereof are described in detail below with reference to examples of the specification.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.

Furthermore, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

Example 1

A fried type collagen casing is prepared by wet soaking, which comprises the following steps:

(1) preparing the cow hide pulp: mincing the pretreated bovine second-layer skin, shearing for 7min in a high-speed crusher at a shearing rate of 8000rpm, adding crushed ice, and controlling the temperature at 13 ℃;

(2) preparing mixed acid liquor: preparing 0.36 wt% hydrochloric acid solution, adding 2.3 wt% softwood fiber hydrochloric acid solution, and uniformly stirring to obtain acid mixed solution;

(3) preparing a collagen dough: mixing the acid mixed solution prepared in the step (2) with the cow hide pulp prepared in the step (1) in equal mass to prepare collagen clusters, and storing the collagen clusters for 18 hours at the temperature of 8 ℃;

(4) extrusion curing: homogenizing and filtering the collagen clusters under the pressure of 30MPa, extruding by an extruder with the rotating speed of 20rpm, introducing air and ammonia gas, wherein the pressure is 20psi, the temperature is room temperature during curing, and the curing time is 2 min;

(5) and (3) crosslinking and water washing: the cured casing passes through a crosslinking soaking pool, and the crosslinking time is 30 min; the cross-linking solution is 50ppm glutaraldehyde aqueous solution; washing the sausage casing with water in a washing tank for 25min to remove residual salts;

(6) plasticizing: preparing mixed plasticizing liquid, adding the mixed plasticizing liquid into a plasticizing pool, and enabling the sausage casing to pass through the plasticizing pool for 25 min; the mixing plasticizing pool is an aqueous solution containing 0.2% of sodium bicarbonate, 4.0% of glycerin and 1.0% of carboxymethyl cellulose;

(7) drying and rewetting: three-stage drying is carried out on the casing after washing and plasticizing, wherein the first-stage drying temperature is 90 ℃ and the time is 5 min; the second stage drying temperature is 75 deg.C, and the time is 5 min; the three-section drying temperature is 65 ℃, and the time is 3 min; finally, the casing passes through a humidity returning device, and the humidity is controlled to be 15%, so that the collagen casing is obtained.

The test shows that the wet tensile strength of the sausage casing is 3.33MPa, the breaking elongation is 40.74 percent, and the sausage casing is made of the mixture of the dried sausage casing and the dried sausage casing; the casing has soft and crisp organoleptic characteristics after being fried.

Example 2

A fried type collagen casing is prepared by wet soaking, which comprises the following steps:

(1) preparing the cow hide pulp: mincing the pretreated bovine second-layer skin, shearing for 7min in a high-speed crusher at a shearing rate of 8000rpm, adding crushed ice, and controlling the temperature at 13 ℃;

(2) preparing mixed acid liquor: preparing 0.36 wt% of HCl solution, adding 2.3 wt% of softwood fiber into the HCl solution, and uniformly stirring to obtain acid mixed solution;

(3) preparing a collagen dough: mixing the acid mixed solution prepared in the step (2) with the cow hide pulp prepared in the step (1) in equal mass to prepare collagen clusters, and storing the collagen clusters for 18 hours at the temperature of 8 ℃;

(4) extrusion curing: homogenizing and filtering the collagen clusters under the pressure of 30MPa, extruding by an extruder with the rotating speed of 20rpm, introducing air and ammonia gas, wherein the pressure is 20psi, the temperature is room temperature during curing, and the curing time is 2 min;

(5) and (3) crosslinking and water washing: the cured casing passes through a crosslinking soaking pool, and the crosslinking time is 30 min; the cross-linking solution is 50ppm glutaraldehyde aqueous solution; washing the sausage casing with water in a washing tank for 25min to remove residual salts;

(6) plasticizing: preparing mixed plasticizing liquid, adding the mixed plasticizing liquid into a plasticizing pool, and enabling the sausage casing to pass through the plasticizing pool for 25 min; the mixing plasticizing pool is an aqueous solution containing 0.2% of ammonium bicarbonate, 4.0% of glycerol and 1.0% of carboxymethyl cellulose;

(7) drying and rewetting: three-stage drying is carried out on the casing after washing and plasticizing, wherein the first-stage drying temperature is 90 ℃ and the time is 5 min; the second stage drying temperature is 75 deg.C, and the time is 5 min; the three-section drying temperature is 65 ℃, and the time is 3 min; finally, the casing passes through a humidity returning device, and the humidity is controlled to be 15%, so that the collagen casing is obtained.

The test shows that the wet tensile strength of the sausage casing is 4.11MPa, the elongation at break is 49.52 percent, and the organoleptic characteristics of the fried sausage casing are moderate hardness and crispness.

Example 3

A fried type collagen casing is prepared by wet soaking, which comprises the following steps:

(1) preparing the cow hide pulp: mincing the pretreated bovine second-layer skin, shearing for 7min in a high-speed crusher at a shearing rate of 8000rpm, adding crushed ice, and controlling the temperature at 13 ℃;

(2) preparing mixed acid liquor: preparing 0.36 wt% of HCl solution, adding 2.3 wt% of softwood fiber into the HCl solution, and uniformly stirring to obtain acid mixed solution;

(3) preparing a collagen dough: mixing the acid mixed solution prepared in the step (2) with the cow hide pulp prepared in the step (1) in equal mass to prepare collagen clusters, and storing the collagen clusters for 18 hours at the temperature of 8 ℃;

(4) extrusion curing: homogenizing and filtering the collagen clusters under the pressure of 30MPa, extruding by an extruder with the rotating speed of 20rpm, introducing air and ammonia gas, wherein the pressure is 20psi, the temperature is room temperature during curing, and the curing time is 2 min;

(5) and (3) crosslinking and water washing: the cured casing passes through a crosslinking soaking pool, and the crosslinking time is 30 min; the cross-linking solution is 50ppm glutaraldehyde aqueous solution; washing the sausage casing with water in a washing tank for 25min to remove residual salts;

(6) plasticizing: preparing mixed plasticizing liquid, adding the mixed plasticizing liquid into a plasticizing pool, and enabling the sausage casing to pass through the plasticizing pool for 25 min; the mixing plasticizing pool is an aqueous solution containing 0.2% of sodium bicarbonate, 0.1% of sodium lactate, 4.0% of glycerol and 1.0% of carboxymethyl cellulose;

(7) drying and rewetting: three-stage drying is carried out on the casing after washing and plasticizing, wherein the first-stage drying temperature is 90 ℃ and the time is 5 min; the second stage drying temperature is 75 deg.C, and the time is 5 min; the three-section drying temperature is 65 ℃, and the time is 3 min; finally, the casing passes through a humidity returning device, and the humidity is controlled to be 15%, so that the collagen casing is obtained.

Through measurement, the wet tensile strength of the sausage casing is 4.15MPa, and the elongation at break is 39.31%; the casing has crisp and moderate hardness after frying.

Example 4

A fried type collagen casing is prepared by wet soaking, which comprises the following steps:

(1) preparing the cow hide pulp: mincing the pretreated bovine second-layer skin, shearing for 7min in a high-speed crusher at a shearing rate of 8000rpm, adding crushed ice, and controlling the temperature at 13 ℃;

(2) preparing mixed acid liquor: preparing 0.36 wt% of HCl solution, adding 2.3 wt% of softwood fiber into the HCl solution, and uniformly stirring to obtain acid mixed solution;

(3) preparing a collagen dough: mixing the acid mixed solution prepared in the step (2) with the cow hide pulp prepared in the step (1) in equal mass to prepare collagen clusters, and storing the collagen clusters for 18 hours at the temperature of 8 ℃;

(4) extrusion curing: homogenizing and filtering the collagen clusters under the pressure of 30MPa, extruding by an extruder with the rotating speed of 20rpm, introducing air and ammonia gas, wherein the pressure is 20psi, the temperature is room temperature during curing, and the curing time is 2 min;

(5) and (3) crosslinking and water washing: the cured casing passes through a crosslinking soaking pool, and the crosslinking time is 30 min; the cross-linking solution is 50ppm glutaraldehyde aqueous solution; washing the sausage casing with water in a washing tank for 25min to remove residual salts;

(6) plasticizing: preparing mixed plasticizing liquid, adding the mixed plasticizing liquid into a plasticizing pool, and enabling the sausage casing to pass through the plasticizing pool for 25 min; the mixing plasticizing pool is an aqueous solution containing 0.2% of ammonium bicarbonate, 0.1% of sodium dihydrogen phosphate, 4.0% of glycerol and 1.0% of carboxymethyl cellulose;

(7) drying and rewetting: three-stage drying is carried out on the casing after washing and plasticizing, wherein the first-stage drying temperature is 90 ℃ and the time is 5 min; the second stage drying temperature is 75 deg.C, and the time is 5 min; the three-section drying temperature is 65 ℃, and the time is 3 min; finally, the casing passes through a humidity returning device, and the humidity is controlled to be 15%, so that the collagen casing is obtained.

Through measurement, the wet tensile strength of the sausage casing is 3.79MPa, and the elongation at break is 41.31%; the casing has soft and crisp organoleptic characteristics after being fried, and the brittleness is moderate.

Example 5

A fried type collagen casing is prepared by wet soaking, which comprises the following steps:

(1) preparing the cow hide pulp: mincing the pretreated bovine second-layer skin, shearing for 7min in a high-speed crusher at a shearing rate of 8000rpm, adding crushed ice, and controlling the temperature at 13 ℃;

(2) preparing mixed acid liquor: preparing 0.36 wt% of HCl and 80ppm (w/w) of disodium dihydrogen pyrophosphate acid solution, adding 2.3 wt% of softwood fiber into the acid solution, and uniformly stirring to obtain acid mixed solution;

(3) preparing a collagen dough: mixing the acid mixed solution prepared in the step (2) with the cow hide pulp prepared in the step (1) in equal mass to prepare collagen clusters, and storing the collagen clusters for 18 hours at the temperature of 8 ℃;

(4) extrusion curing: homogenizing and filtering the collagen clusters under the pressure of 30MPa, extruding by an extruder with the rotating speed of 20rpm, introducing air and ammonia gas, wherein the pressure is 20psi, the temperature is room temperature during curing, and the curing time is 2 min;

(5) and (3) crosslinking and water washing: the cured casing passes through a crosslinking soaking pool, and the crosslinking time is 30 min; the cross-linking solution is 50ppm glutaraldehyde aqueous solution; washing the sausage casing with water in a washing tank for 25min to remove residual salts;

(6) plasticizing: preparing mixed plasticizing liquid, adding the mixed plasticizing liquid into a plasticizing pool, and enabling the sausage casing to pass through the plasticizing pool for 25 min; the mixing plasticizing pool is an aqueous solution containing 0.1% of sodium bicarbonate, 4.0% of glycerin and 1.0% of carboxymethyl cellulose;

(7) drying and rewetting: three-stage drying is carried out on the casing after washing and plasticizing, wherein the first-stage drying temperature is 90 ℃ and the time is 5 min; the second stage drying temperature is 75 deg.C, and the time is 5 min; the three-section drying temperature is 65 ℃, and the time is 3 min; finally, the casing passes through a humidity returning device, and the humidity is controlled to be 15%, so that the collagen casing is obtained.

Through measurement, the wet tensile strength of the sausage casing is 3.95MPa, and the elongation at break is 45.81%; the casing has crisp and moderate hardness after frying.

Example 6

In order to study the influence of bicarbonate on the physical and mechanical properties of the collagen casing, the change of the properties of the collagen casing along with the increase of the addition amount of sodium bicarbonate and ammonium bicarbonate is systematically analyzed. In this example, bicarbonate was added in different amounts, and the remaining process conditions were the same as in examples 1 and 2, which are not repeated, except that:

(6) plasticizing: preparing mixed plasticizing liquid, adding the mixed plasticizing liquid into a plasticizing pool, and enabling the sausage casing to pass through the plasticizing pool for 25 min; the solution in the mixing plasticizing pool is a composite aqueous solution of bicarbonate, glycerol and carboxymethyl cellulose; the bicarbonate is sodium bicarbonate or ammonium bicarbonate, and the concentration of the bicarbonate is 0.5%, 0.1%, 0.2% and 0.3% respectively; the concentration of the glycerol is 4.0%; the carboxymethyl cellulose concentration was 1.0%.

The measurement results of the thickness and the wet mechanical property of the casing are shown in figures 4-6, and the results show that the thickness of the collagen casing is reduced by plasticizing and soaking the bicarbonate; ammonium bicarbonate has no obvious influence on the wet mechanical property of the sausage casing, while sodium bicarbonate reduces the tensile strength and the elongation at break of the sausage casing to a certain extent, but keeps stable after reaching the concentration of 0.1 percent.

Comparative example 1

The addition of bicarbonate, added in the corresponding step in example 1, was omitted and the collagen casing was prepared by a conventional wet process, which comprises the following steps:

(1) preparing the cow hide pulp: mincing the pretreated bovine second-layer skin, shearing for 7min in a high-speed crusher at a shearing rate of 8000rpm, adding crushed ice, and controlling the temperature at 13 ℃;

(2) preparing mixed acid liquor: preparing 0.36 wt% of HCl solution, adding 2.3 wt% of softwood fiber into the HCl solution, and uniformly stirring to obtain acid mixed solution;

(3) preparing a collagen dough: mixing the acid mixed solution prepared in the step (2) with the cow hide pulp prepared in the step (1) in equal mass to prepare collagen clusters, and storing the collagen clusters for 18 hours at the temperature of 8 ℃;

(4) extrusion curing: homogenizing and filtering the collagen clusters under the pressure of 30MPa, extruding by an extruder with the rotating speed of 20rpm, introducing air and ammonia gas, wherein the pressure is 20psi, the temperature is room temperature during curing, and the curing time is 2 min;

(5) and (3) crosslinking and water washing: the cured casing passes through a crosslinking soaking pool, and the crosslinking time is 30 min; the cross-linking solution is 50ppm glutaraldehyde aqueous solution; washing the sausage casing with water in a washing tank for 25min to remove residual salts;

(6) plasticizing: preparing mixed plasticizing liquid, adding the mixed plasticizing liquid into a plasticizing pool, and enabling the sausage casing to pass through the plasticizing pool for 25 min; the mixed plasticizing liquid is an aqueous solution containing 4.0% of glycerin and 1.0% of carboxymethyl cellulose;

(7) drying and rewetting: three-stage drying is carried out on the casing after washing and plasticizing, wherein the first-stage drying temperature is 90 ℃ and the time is 5 min; the second stage drying temperature is 75 deg.C, and the time is 5 min; the three-section drying temperature is 65 ℃, and the time is 3 min; finally, the casing passes through a humidity returning device, and the humidity is controlled to be 12%, so that the collagen casing is obtained.

Through measurement, the wet tensile strength of the sausage casing is 4.29MPa, and the elongation at break is 53.23%; after the casing is fried, the sensory characteristics are high hardness, high toughness and difficult biting.

Comparative example 2

The addition of sodium bicarbonate was omitted as per the procedure in example 3 to prepare a collagen casing, which was followed:

(1) preparing the cow hide pulp: mincing the pretreated bovine second-layer skin, shearing for 7min in a high-speed crusher at a shearing rate of 8000rpm, adding crushed ice, and controlling the temperature at 13 ℃;

(2) preparing mixed acid liquor: preparing 0.36 wt% of HCl solution, adding 2.3 wt% of softwood fiber into the HCl solution, and uniformly stirring to obtain acid mixed solution;

(3) preparing a collagen dough: mixing the acid mixed solution prepared in the step (2) with the cow hide pulp prepared in the step (1) in equal mass to prepare collagen clusters, and storing the collagen clusters for 18 hours at the temperature of 8 ℃;

(4) extrusion curing: homogenizing and filtering the collagen clusters under the pressure of 30MPa, extruding by an extruder with the rotating speed of 20rpm, introducing air and ammonia gas, wherein the pressure is 20psi, the temperature is room temperature during curing, and the curing time is 2 min;

(5) and (3) crosslinking and water washing: the cured casing passes through a crosslinking soaking pool, and the crosslinking time is 30 min; the cross-linking solution is 50ppm glutaraldehyde aqueous solution; washing the sausage casing with water in a washing tank for 25min to remove residual salts;

(6) plasticizing: preparing mixed plasticizing liquid, adding the mixed plasticizing liquid into a plasticizing pool, and enabling the sausage casing to pass through the plasticizing pool for 25 min; the mixed plasticizing liquid is an aqueous solution containing 0.1 percent of sodium lactate, 4.0 percent of glycerin and 1.0 percent of carboxymethyl cellulose;

(7) drying and rewetting: three-stage drying is carried out on the casing after washing and plasticizing, wherein the first-stage drying temperature is 90 ℃ and the time is 5 min; the second stage drying temperature is 75 deg.C, and the time is 5 min; the three-section drying temperature is 65 ℃, and the time is 3 min; finally, the casing passes through a humidity returning device, and the humidity is controlled to be 13%, so that the collagen casing is obtained.

Through measurement, the wet tensile strength of the sausage casing is 3.95MPa, and the elongation at break is 52.88%; after the casing is fried, the sensory characteristics of high hardness, high toughness and difficult biting and breaking show that the frying characteristic of the casing cannot be improved only by adding the acid salt into the plasticizing liquid.

Comparative example 3

The collagen casing was prepared by omitting the ammonium bicarbonate added in example 4, and the procedure was as follows:

(1) preparing the cow hide pulp: mincing the pretreated bovine second-layer skin, shearing for 7min in a high-speed crusher at a shearing rate of 8000rpm, adding crushed ice, and controlling the temperature at 13 ℃;

(2) preparing mixed acid liquor: preparing 0.36 wt% of HCl solution, adding 2.3 wt% of softwood fiber into the HCl solution, and uniformly stirring to obtain acid mixed solution;

(3) preparing a collagen dough: mixing the acid mixed solution prepared in the step (2) with the cow hide pulp prepared in the step (1) in equal mass to prepare collagen clusters, and storing the collagen clusters for 18 hours at the temperature of 8 ℃;

(4) extrusion curing: homogenizing and filtering the collagen clusters under the pressure of 30MPa, extruding by an extruder at the rotating speed of 20rpm, and introducing air and ammonia gas at the pressure of 20 psi;

(5) and (3) crosslinking and water washing: the cured casing passes through a crosslinking soaking pool, and the crosslinking time is 30 min; the cross-linking solution is 50ppm glutaraldehyde aqueous solution; washing the sausage casing with water in a washing tank for 25min to remove residual salts;

(6) plasticizing: preparing mixed plasticizing liquid, adding the mixed plasticizing liquid into a plasticizing pool, and enabling the sausage casing to pass through the plasticizing pool for 25 min; the mixed plasticizing liquid is an aqueous solution containing 1.0% of sodium dihydrogen phosphate, 4.0% of glycerol and 1.0% of carboxymethyl cellulose;

(7) drying and rewetting: three-stage drying is carried out on the casing after washing and plasticizing, wherein the first-stage drying temperature is 90 ℃ and the time is 5 min; the second stage drying temperature is 75 deg.C, and the time is 5 min; the three-section drying temperature is 65 ℃, and the time is 3 min; finally, the casing passes through a humidity returning device, and the humidity is controlled to be 13%, so that the collagen casing is obtained.

Through measurement, the wet tensile strength of the sausage casing is 3.05MPa, and the elongation at break is 34.62%; after the casing is fried, the sensory characteristics of high hardness, high toughness and difficult biting and breaking show that the frying characteristic of the casing cannot be improved only by adding the acid salt into the plasticizing liquid.

Comparative example 4

The collagen casing was prepared by omitting the sodium bicarbonate added in example 5, and the procedure was as follows:

(1) preparing the cow hide pulp: mincing the pretreated bovine second-layer skin, shearing for 7min in a high-speed crusher at a shearing rate of 8000rpm, adding crushed ice, and controlling the temperature at 13 ℃;

(2) preparing mixed acid liquor: preparing 0.36 wt% of HCl and 80ppm (w/w) of disodium dihydrogen pyrophosphate acid solution, adding 2.3 wt% of softwood fiber into the acid solution, and uniformly stirring to obtain acid mixed solution;

(3) preparing a collagen dough: mixing the acid mixed solution prepared in the step (2) with the cow hide pulp prepared in the step (1) in equal mass to prepare collagen clusters, and storing the collagen clusters for 18 hours at the temperature of 8 ℃;

(4) extrusion curing: homogenizing and filtering the collagen clusters under the pressure of 30MPa, extruding by an extruder with the rotating speed of 20rpm, introducing air and ammonia gas, wherein the pressure is 20psi, the temperature is room temperature during curing, and the curing time is 2 min;

(5) and (3) crosslinking and water washing: the cured casing passes through a crosslinking soaking pool, and the crosslinking time is 30 min; the cross-linking solution is 50ppm glutaraldehyde aqueous solution; washing the sausage casing with water in a washing tank for 25min to remove residual salts;

(6) plasticizing: preparing mixed plasticizing liquid, adding the mixed plasticizing liquid into a plasticizing pool, and enabling the sausage casing to pass through the plasticizing pool for 25 min; the mixed plasticizing liquid is an aqueous solution containing 4.0% of glycerin and 1.0% of carboxymethyl cellulose;

(7) drying and rewetting: three-stage drying is carried out on the casing after washing and plasticizing, wherein the first-stage drying temperature is 90 ℃ and the time is 5 min; the second stage drying temperature is 75 deg.C, and the time is 5 min; the three-section drying temperature is 65 ℃, and the time is 3 min; finally, the casing passes through a humidity returning device, and the humidity is controlled to be 13%, so that the collagen casing is obtained.

Through measurement, the wet tensile strength of the sausage casing is 4.31MPa, and the elongation at break is 59.31%; after the casing is fried, the sensory characteristics of high hardness, high toughness and difficult biting are shown, and the frying characteristic of the casing cannot be improved only by adding the acid salt into the acid mixed solution.

As can be seen from figures 1 and 2, the sausage casing prepared by the invention keeps good transparent effect after being fried for 10min, does not crack after being fried, and still has good effect of containing contents.

As shown in fig. 3, the microstructure SEM images of the casings prepared in examples 1 and 2 of our invention compared with the casing prepared in comparative document 1 show that the bicarbonate can form cellular pores on the casing surface, thereby improving the permeability and the frying property of the casings.

From fig. 4, SEM images of the interfacial microstructure of the casings prepared in examples 1 and 2 of my invention show that the casings with bicarbonate added delaminate more significantly and the spacing between layers becomes larger.

As can be seen from fig. 5, the sausage casing prepared by the preparation process provided in the present invention is not much inferior to the sausage casing prepared by the prior art in terms of the frying shrinkage, and the sausage casing prepared by the present invention can meet the requirements regarding the frying shrinkage in the current use of the sausage casing.

From fig. 6, it can be seen that the sausage casing prepared by the preparation process provided in the present invention is not much different from the sausage casing prepared by the prior art in terms of cooking shrinkage, and the sausage casing prepared by the preparation process provided in my invention can meet the current requirements on the use of the sausage casing in terms of cooking shrinkage.

From fig. 7 and 8, the collagen casing prepared by the invention has small tendency of change of tensile strength and elongation at break with the addition of sodium bicarbonate and ammonium bicarbonate under wet condition, the addition of sodium bicarbonate can slightly reduce the tensile strength and toughness of the casing, but the reduction range is extremely small, the use of the casing is not influenced, the mechanical strength of the casing is kept stable when the addition concentration reaches 0.1%, and the influence of the addition of sodium bicarbonate on the mechanical strength of the casing can be directly ignored.

As can be seen from fig. 9, the thickness of the casing decreases with increasing bicarbonate concentration.

It should be noted that the above-mentioned embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.