阅读说明：本技术 一种疏水型食品包装膜及其制备方法 (Hydrophobic food packaging film and preparation method thereof ) 是由 费鹏 于 2019-10-16 设计创作，主要内容包括：本发明涉及食品保鲜膜制备技术领域,具体涉及一种疏水型食品包装膜及其制备方法。本发明公开食品保鲜膜由以下重量份数的原料制备而成：低甲氧基果胶15-30份,壳聚糖15-30份,甘油5-15份,乙酸3-5份,荷叶角质10-20份。本以荷叶为主要原料,提取角质,并与果胶、壳聚糖、甘油共混,最终通过流延法制备保鲜膜,使其获得较好的疏水性能,接触角可以达到99.6°,拉伸强度可以达到5.96 MPa,断裂伸长率达到128.0%,且本发明的产品无毒无害,易降解,不会造成环境污染等问题。(The invention relates to the technical field of food preservative film preparation, in particular to a hydrophobic food packaging film and a preparation method thereof. The invention discloses a food preservative film which is prepared from the following raw materials in parts by weight: 15-30 parts of low methoxyl pectin, 15-30 parts of chitosan, 5-15 parts of glycerol, 3-5 parts of acetic acid and 10-20 parts of lotus leaf cutin. The lotus leaf is used as a main raw material, the cutin is extracted, and the lotus leaf, the pectin, the chitosan and the glycerol are blended, and finally the preservative film is prepared by a tape casting method, so that the preservative film has good hydrophobic property, the contact angle can reach 99.6 degrees, the tensile strength can reach 5.96 MPa, the elongation at break can reach 128.0 percent, and the product is non-toxic and harmless, is easy to degrade, and can not cause the problems of environmental pollution and the like.)

1. A hydrophobic food packaging film is characterized in that: the composite material is prepared from the following raw materials in parts by weight: 15-30 parts of low methoxyl pectin, 15-30 parts of chitosan, 5-15 parts of glycerol, 3-5 parts of acetic acid and 10-20 parts of lotus leaf cutin.

2. A hydrophobic food packaging film according to claim 1, wherein the low methoxyl pectin has a degree of methyl esterification of 20% to 30%.

3. The hydrophobic food packaging film of claim 1, wherein 10-20 parts of lotus leaf cutin is added to enhance the hydrophobic property of the packaging film.

4. The method for preparing a hydrophobic food packaging film according to claim 1, wherein: which comprises the following steps:

1) placing fresh lotus leaves in a blast oven, drying, pulverizing the lotus leaves by using a powder grinding machine, and sieving to obtain 80-100 mesh lotus leaf powder;

2) dispersing dried lotus leaf powder in deionized water, adding pectinase and cellulase, ultrasonically oscillating in an ultrasonic disperser for 10-20 min, heating in water bath at 35-40 deg.C for 48 hr, hydrolyzing pectin and cellulase, and promoting dispersion of lotus leaf powder;

3) adding NaOH powder into the suspension, adjusting the pH value of the suspension to 12-14, then placing the suspension in an ultrasonic disperser, ultrasonically vibrating for 10 min to remove air in liquid, pouring the suspension into a polytetrafluoroethylene reaction kettle, purging for 5min by using high-purity nitrogen, and timely covering a reaction kettle cover to prevent the oxidation of cutin in the subsequent reaction; the reaction kettle is placed in an oven to be heated, the cutin is high-polymerized fatty acid, the cutin is completely stored in a high-temperature strong alkali environment, and cellulose, hemicellulose, fat, protein, polysaccharide and the like are promoted to be hydrolyzed under the high-temperature strong alkali environment, so that the cutin is separated;

4) after the reaction is finished, filtering the liquid, collecting filtrate, and removing residues; adding concentrated hydrochloric acid into the filtrate, adjusting pH to 6-7 to precipitate cutin, filtering, and collecting residue;

5) adding filter residue into chloroform: soxhlet extraction is carried out for 24 hours in a methanol solution, and residual wax and pigment are removed; collecting the residual powder after Soxhlet extraction, washing with methanol, and freeze-drying to obtain cutin;

6) adding chitosan into deionized water, adding acetic acid, stirring for 60 min to obtain a clear and light yellow solution, ultrasonic processing for degassing, and stirring at room temperature for 5 min;

7) dispersing cutin in deionized water, adding glycerol, ultrasonic oscillating for 30 min, adding low methoxyl pectin, and stirring for 60 min;

8) mixing the chitosan solution and the cutin/pectin solution, and stirring for 60 min to obtain a mixed membrane solution;

9) and pouring the mixed film solution on a polytetrafluoroethylene flat plate which is inclined at an angle of 15-20 degrees, uniformly coating the film solution on the flat plate, and then placing the flat plate in a blast oven for drying to obtain the hydrophobic food preservative film.

5. The method for preparing a hydrophobic food packaging film according to claim 3, wherein: and 3) heating for 2-3 h under strong alkali (pH 12-14) and high heat (110-.

Technical Field

The invention belongs to the technical field of novel food packaging, and particularly relates to a hydrophobic food preservative film applied to the field of food packaging and a preparation method thereof.

Background

The plastic products produced along with the industrial development are widely applied to the fields of food packaging and fresh keeping due to rich sources, beautiful products, light weight, sanitation, convenient processing, low price and stable property. However, the plastic package is not easy to decompose after use, which can cause white pollution, and some plastic packages can easily generate harmful gas and peculiar smell, which have certain toxic action on human body. The search for materials to replace plastic packaging is therefore an important issue in "packaging and environment". In the face of pollution and safety problems, various countries strive to find a "green packaging" material. Among the numerous "green packaging" materials, the preparation of degradable packaging materials from natural polymeric hosts is becoming a hot spot. The polysaccharide has rich resources, wide sources, safety, no toxicity, good biocompatibility and degradability, gradually becomes an important research object in the field of packaging, and is successfully applied to packaging of dried fruits, sugar tablets, toffee and seasonings and packaging of desserts, fruits and vegetables, dried fruits and the like in food.

In recent years, chitosan has been more and more emphasized by people as an excellent film material, has good film forming property, biocompatibility, biodegradability and low price, has a plurality of active amino groups and hydroxyl groups distributed on a molecular chain, has strong chemical reaction capability and the like, has great advantages in the aspect of packaging materials, and has the film forming property applied to the industrial fields of textile, printing and dyeing, papermaking, medicine, food and the like. Pectin is a water-soluble acidic polysaccharide substance existing in natural plants, has good antibacterial performance, is a novel natural food film preservative, and can generate composite reaction between pectin and chitosan under a proper system to generate pectin/chitosan polyelectrolyte composite gel.

However, both chitosan and pectin are hydrophilic substances, which results in that the film is very sensitive to humidity and moisture after being formed and is very easy to absorb water in a humid environment, and when moisture in the film increases, the intermolecular cohesion and adhesion decrease, and the strength and modulus of the film become very low. Therefore, improving the hydrophobic property of the natural polymer food packaging film is a necessary way for expanding the application of the natural polymer food packaging film.

Disclosure of Invention

The invention aims to provide a hydrophobic food preservative film and a preparation method thereof by utilizing the high hydrophobicity of lotus leaf cutin, aiming at the problems that the existing bio-based food preservative film is easy to absorb water and the mechanical property is rapidly deteriorated after absorbing water.

In order to achieve the purpose, the invention adopts the following technical scheme:

the hydrophobic food preservative film is prepared from the following raw materials in parts by weight:

15-30 parts of low methoxyl pectin (the methyl esterification degree is 20-30%);

15-30 parts of chitosan;

10-15 parts of glycerol;

3-5 parts of acetic acid

10-20 parts of lotus leaf cutin

Further, the extraction of the cutin of the lotus leaf involves the following raw materials:

fresh lotus leaf 200 portions

2-3 parts of pectinase

1-2 parts of cellulase

The invention also provides an extraction method of the lotus leaf cutin and a preparation method of the hydrophobic food preservative film, which comprises the following steps:

1) and (3) placing the fresh lotus leaves in a blast oven, and drying. Pulverizing folium Nelumbinis with a pulverizer, and sieving to obtain 80-100 mesh folium Nelumbinis powder;

2) dispersing dried lotus leaf powder in deionized water, adding pectinase and cellulase, ultrasonically oscillating in an ultrasonic disperser for 10-20 min, heating in water bath at 35-40 deg.C for 48 hr, hydrolyzing pectin and cellulase, and promoting dispersion of lotus leaf powder;

3) adding NaOH powder into the suspension, adjusting the pH value of the suspension to 12-14, then placing the suspension in an ultrasonic disperser, ultrasonically vibrating for 10 min to remove air in liquid, pouring the suspension into a polytetrafluoroethylene reaction kettle, purging for 5min by using high-purity nitrogen, and timely covering a reaction kettle cover to prevent the oxidation of cutin in the subsequent reaction; the reaction kettle is placed in an oven to be heated, the cutin is high-polymerized fatty acid, the cutin is completely stored in a high-temperature strong alkali environment, and cellulose, hemicellulose, fat, protein, polysaccharide and the like are promoted to be hydrolyzed under the high-temperature strong alkali environment, so that the cutin is separated;

4) after the reaction is finished, filtering the liquid, collecting filtrate, and removing residues; adding concentrated hydrochloric acid into the filtrate, adjusting pH to 6-7 to precipitate cutin, filtering, and collecting residue;

5) adding filter residue into chloroform: soxhlet extraction is carried out for 24 hours in a methanol solution, and residual wax and pigment are removed; collecting the residual powder after Soxhlet extraction, washing with methanol, and freeze-drying to obtain cutin;

6) adding chitosan into deionized water, adding acetic acid, stirring for 60 min to obtain a clear and light yellow solution, ultrasonic processing for degassing, and stirring at room temperature for 5 min;

7) dispersing cutin in deionized water, adding glycerol, ultrasonic oscillating for 30 min, adding low methoxyl pectin, and stirring for 60 min;

8) mixing the chitosan solution and the cutin/pectin solution, and stirring for 60 min to obtain a mixed membrane solution;

9) and pouring the mixed film solution on a polytetrafluoroethylene flat plate which is inclined at an angle of 15-20 degrees, uniformly coating the film solution on the flat plate, and then placing the flat plate in a blast oven for drying to obtain the hydrophobic food preservative film.

Step 1), drying the fresh lotus leaves at 70-80 ℃ for 24-30 h;

step 3), the flow rate of the high-purity nitrogen is 300-400 mL/min;

step 3), heating at the temperature of 110-120 ℃ for 2-3 h;

step 4), the concentration of concentrated hydrochloric acid used is 2-3 mol/L;

step 5), chloroform used: the volume ratio of the methanol solution is 1: 1;

and step 9), drying at 40 ℃ for 12-24 h.

According to the technical scheme, the lotus leaves are used as the main raw material, the cutin is extracted, the extracted cutin is mixed with the pectin, the chitosan and the glycerol, and finally the preservative film is prepared through a tape casting method, so that the preservative film has good hydrophobic property.

The invention has the following advantages:

1. pectin is a water-soluble acidic polysaccharide substance existing in natural plants, has good film forming property, and is a novel natural food film-type preservative, and chitosan is chitosan, and has good film forming property, moisture retention property and antibacterial property. The composite film prepared by mixing the two is safe and nontoxic, and has good biocompatibility, degradability and fresh-keeping performance, so that the prepared film is safe and environment-friendly;

2. pectin is a cationic polysaccharide, while chitosan is the only natural anionic polysaccharide in nature. The degree of methyl esterification in natural pectin is generally higher (>50 percent) of the low methoxyl pectin selected by the invention, wherein a large amount of-COOH contained in the low methoxyl pectin is easy to be combined with-NH in chitosan₂The carbonyl ammonia reaction is used for crosslinking to form a composite membrane with higher strength and toughness;

3. the lotus leaf cutin is complex biological polyester, is mainly polymerized by C16 and C18 through ester bonds, has strong hydrophobicity, and can better enhance the hydrophobic property of the composite membrane. Meanwhile, flexible molecular chains are easily dispersed in a network structure with the cross-linking performance of chitosan and pectin, so that the toughness and the strength of the composite membrane are enhanced.

Drawings

FIG. 1 is a graph showing the comparison of contact angle and mechanical properties of a composite film before and after adding lotus leaf cutin in the example of the present invention.

Wherein, FIG. 1A shows the contact angle (61.7 degree) of the composite film before adding lotus leaf cutin, and FIG. 1B shows the contact angle (99.6 degree) of the composite film after adding lotus leaf cutin. It is believed that contact angles greater than 90 ° are predominantly hydrophobic.

FIG. 1C is a graph showing the relationship between the tensile distance of the composite film before and after addition of the lotus leaf cutin and the load applied thereto, under a texture analyzer tensile test; FIG. 1D shows the tensile strength and elongation at break of the composite film before and after addition of the lotus leaf cutin, calculated from FIG. 1C.

Detailed Description

The hydrophobic food preservative film is prepared from the following raw materials in parts by weight:

15-30 parts of low methoxyl pectin (the methyl esterification degree is 20-30%);

15-30 parts of chitosan;

5-15 parts of glycerol;

3-5 parts of acetic acid

10-20 parts of lotus leaf cutin

Further, the extraction of the cutin of the lotus leaf involves the following raw materials:

fresh lotus leaf 200 portions

2-3 parts of pectinase

1-2 parts of cellulase

The invention also provides an extraction method of the lotus leaf cutin and a preparation method of the hydrophobic food preservative film, which comprises the following steps:

1) and (3) placing 200-300 parts of fresh lotus leaves in a blast oven and drying. Pulverizing folium Nelumbinis with a pulverizer, and sieving to obtain 80-100 mesh folium Nelumbinis powder;

2) dispersing 50-60 parts of dried lotus leaf powder in 500 parts of water, adding 2-3 parts of pectinase and 1-2 parts of cellulase, then ultrasonically oscillating in an ultrasonic disperser for 10-20 min, then heating in a water bath at 35-40 ℃ for 48 h, hydrolyzing pectin and cellulase, and promoting the dispersion of the lotus leaf powder;

3) adding NaOH powder into the suspension, adjusting the pH value of the suspension to 12-14, then placing the suspension in an ultrasonic disperser, ultrasonically vibrating for 10 min to remove air in liquid, pouring the suspension into a polytetrafluoroethylene reaction kettle, purging for 5min by using high-purity nitrogen, and timely covering a reaction kettle cover to prevent the oxidation of cutin in the subsequent reaction;

4) the reaction kettle is placed in a drying oven with the temperature of 110-;

5) after the reaction is finished, filtering the liquid, collecting filtrate, and removing residues; adding concentrated hydrochloric acid into the filtrate, adjusting pH to 6-7 to precipitate cutin, filtering, and collecting residue;

7) adding filter residue into 100 parts of chloroform: soxhlet extraction is carried out for 24 hours in a methanol solution (1: 1), and residual wax and pigment are removed; collecting the residual powder after Soxhlet extraction, washing with methanol, and freeze-drying to obtain cutin;

8) adding 15-30 parts of chitosan into 500 parts of deionized water, adding 10-15 parts of acetic acid, mixing, stirring for 60 min to obtain a clear and light yellow solution, performing ultrasonic treatment for 5min to degas, and stirring for 5min at normal temperature;

9) dispersing 10-20 parts of cutin in 200 parts of deionized water, adding 10-20 parts of glycerol, ultrasonically oscillating for 30 min, adding 15-30 parts of low methoxyl pectin, and continuously stirring for 60 min;

10) mixing the chitosan solution and the cutin/pectin solution, and stirring for 60 min to obtain a mixed membrane solution;

11) and pouring the mixed film solution on a polytetrafluoroethylene flat plate which is inclined at an angle of 15-20 degrees, uniformly coating the film solution on the flat plate, and then placing the flat plate in a 40 ℃ blast oven for drying for 12 hours to obtain the hydrophobic food preservative film.