CN114410077A

CN114410077A - Nano composite active packaging preservative film based on esterification modification and preparation method and application thereof

Info

Publication number: CN114410077A
Application number: CN202210091339.1A
Authority: CN
Inventors: 李立; 赵美艳; 陶宁萍; 罗琦钧; 储玉婵
Original assignee: Shanghai Ocean University
Current assignee: Shanghai Ocean University
Priority date: 2022-01-26
Filing date: 2022-01-26
Publication date: 2022-04-29
Anticipated expiration: 2042-01-26
Also published as: CN114410077B

Abstract

The invention provides a nano composite active packaging preservative film based on esterification modification and a preparation method and application thereof, wherein the method comprises the steps of carrying out esterification reaction on organic acid and carboxymethyl nano-cellulose, mixing dry modified carboxymethyl nano-cellulose, dry poly (butylene adipate)/terephthalate and a chain extender, and carrying out extrusion granulation; carrying out tape casting film formation on the modified mixed particles of carboxymethyl nano-cellulose/poly adipic acid/butylene terephthalate resin, and carrying out transverse and longitudinal stretching; according to the invention, the carboxymethyl nanocellulose is modified by an esterification method through ester bond combination by using organic acid, and the modified carboxymethyl nanocellulose has antibacterial and antioxidant properties, and can inhibit the growth of microorganisms in food and the oxidation loss of food nutrition; the poly (butylene adipate)/terephthalate degradable material is used as the base material of the packaging material, so that the film is endowed with antibacterial and antioxidant properties, is a novel, environment-friendly, safe and reliable active packaging material, and can be applied to the field of food preservation.

Description

Nano composite active packaging preservative film based on esterification modification and preparation method and application thereof

Technical Field

The invention belongs to the technical field of preservative film materials, and particularly relates to a nano-composite active packaging preservative film based on esterification modification, and a preparation method and application thereof.

Background

The use of suitable packaging materials and methods to minimize food loss and provide safe and hygienic food has been the focus of food packaging. Compared with the traditional packaging, the active packaging is a brand new packaging technology. The packaging material is used as a conveying carrier, active substances such as natural antibacterial agents, antioxidants, enzymes and the like are released to the surface of food, the internal environment of food packaging is changed through controlled release of functional components, the propagation of microorganisms is effectively inhibited, the food is prevented from being rotted and deteriorated due to oxidation, the nutritional value and the sensory characteristic of the food are guaranteed, and the shelf life of the food is prolonged. Accordingly, various active packaging technologies have been developed to provide better hygiene and safety of food products and to reduce packaging-related environmental contamination issues. Food packaging is typically composed of common petroleum-based plastics such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate. These petroleum-derived plastic packaging materials have good processability, low cost, and excellent mechanical and barrier (gas and liquid) properties. However, petroleum-derived polymeric materials are generally not recyclable and have poor biodegradability, potentially posing a number of waste disposal and environmental pollution problems.

Poly (butylene-co-terephthalate), PBAT, belongs to thermoplastic biodegradable plastics, has good ductility and elongation at break, good heat resistance and impact resistance, and also has excellent biodegradability, and is one of the most active and best degradable materials for market application in the research of biodegradable plastics, furthermore, nanocellulose is increasingly concerned in the field of material science due to the renewable property, excellent mechanical property and good biocompatibility, nanocellulose (CMNC) is widely used as a reinforcing agent of various composite materials, CMNC is a typical spherical particle, the particle size is intensively distributed in 30-50nm, compared with the original nanocellulose, the surface structure is looser, the chemical reaction activity is enhanced, the crystal structure of CMNC is changed, the crystallinity is significantly reduced, but the thermal stability is improved. The mechanical properties of the PBAT can be improved by mixing the nano-cellulose and the PBAT.

With respect to active packaging, there may be a safety risk to human health due to the potential migration of bacteriostatic agents into the food. The study of non-migratory and natural bacteriostatic agents has therefore become a focus. The use principle of the non-migration type antibacterial agent is mainly that a high molecular polymer is modified by means of physical and chemical methods, and groups with the characteristics of oxidation resistance, bacteria resistance and the like are introduced, so that excellent and lasting preservation performance can be obtained on the premise that corresponding additives are not required to be added into food, and the problems of use and safety of the additives are avoided. The natural bacteriostatic agent can reduce the use of chemical additives in food, and has bacteriostatic and body health promoting effects. The organic acid substances in the natural bacteriostatic agent are very effective to the food quality and safety. The organic acid modified nano composite packaging material has great potential in the aspects of improving the food quality, safety and stability as an innovative packaging and processing technology.

Disclosure of Invention

Aiming at the defects in the prior art, the invention mainly aims to provide a preparation method of a nano-composite active packaging preservative film based on esterification modification.

The invention provides a secondary object of the invention to provide the nano composite active packaging preservative film based on esterification modification.

The final purpose of the invention is to provide the application of the nano composite active packaging preservative film based on esterification modification.

In order to achieve the above primary object, the solution of the present invention is:

a preparation method of a nano composite active packaging preservative film based on esterification modification comprises the following steps:

(1) carrying out esterification reaction on the organic acid and the CMNC to obtain modified CMNC; mixing the dried modified CMNC, the dried biodegradable PBAT and the chain extender, and extruding and granulating in a double-screw extruder to obtain modified CMNC/PBAT resin mixed particles;

(2) and casting the modified CMNC/PBAT resin mixed particles into a film by a casting machine.

Preferably, the mass ratio of the organic acid to the CMNC is 1:1 to 1: 5.

Preferably, the organic acid is selected from one or more of tartaric acid, citric acid, gallic acid and caffeic acid.

Preferably, in the step (1), when the organic acid and the CMNC are subjected to esterification reaction, the CMNC is heated and dissolved by using dimethyl sulfoxide, then the organic acid and the catalyst are added, and the heating reaction is continued; and cooling to room temperature after reaction, adding ethanol until the precipitate is completely precipitated, freezing and centrifuging, adding ethanol, repeatedly freezing and centrifuging, finally performing vacuum drying, and grinding to obtain the modified CMNC.

Preferably, the catalyst is p-toluenesulfonic acid and the amount of catalyst added is 4 wt% of the CMNC.

Preferably, the heating reaction is carried out at a temperature of 90-110 ℃ for 6-8 h.

Preferably, the temperature of the freeze centrifugation is 3-5 ℃, the rotation speed is 7000-9000rpm, and the time is 10-30 min.

Preferably, in step (1), the mass ratio of PBAT to modified CMNC is from 9:1 to 7: 3.

Preferably, in step (1), the drying temperature of the modified CMNC and PBAT is 50-70 ℃ and the drying time is 1-5 h.

Preferably, in step (1), the chain extender is a basf chain extender ADR-4388.

Preferably, in the step (1), the temperatures in the zones 1 to 7 in the twin-screw extruder are respectively as follows: 135 ℃ 145 ℃, 155 ℃ 165 ℃, 165 ℃ 175 ℃, 170 ℃ 180 ℃, 165 ℃ 175 ℃ and 165 ℃ 175 ℃, and the screw rotation speed is 30-60rpm, preferably 40-50 rpm.

Preferably, in the step (2), the temperatures of the zones 1 to 7 in the casting machine are respectively as follows: 135 ℃ 145 ℃, 155 ℃ 165 ℃, 165 ℃ 175 ℃, 170 ℃ 180 ℃, 165 ℃ 175 ℃ and 165 ℃ 175 ℃, and the screw rotation speed is 30-60rpm, preferably 40-50 rpm.

To achieve the above secondary object, the solution of the present invention is:

an esterification modification based nano composite active packaging preservative film is prepared by the preparation method.

To achieve the above final object, the solution of the present invention is:

the application of the nano composite active packaging preservative film based on esterification modification in the field of food preservation is disclosed.

Due to the adoption of the scheme, the invention has the beneficial effects that:

according to the invention, the CMNC is modified by an esterification method through ester bond combination by using organic acid, and the modified CMNC has the antibacterial and antioxidant properties of the organic acid, and can inhibit the growth of microorganisms in food and the oxidation loss of food nutrition; in addition, the PBAT degradable material is used as a base material of the packaging material to carry out tape casting film forming, so that the esterification modified nanocomposite active packaging preservative film endows the film with bacteriostasis and oxygen resistance, is a novel, environment-friendly, safe and reliable active packaging material, and can be applied to the field of food preservation.

Drawings

FIG. 1 is a schematic diagram of the organic acid modified CMNC of the present invention.

FIG. 2 is a Fourier infrared spectrum of an organic acid modified CMNC of the invention.

FIG. 3 is an appearance diagram of straw mushroom in different experimental groups.

FIG. 4 is a PPO change diagram of different experimental groups of volvariella volvacea.

FIG. 5 is a TPC variation graph of volvariella volvacea of different experimental groups.

FIG. 6 is a graph showing the MDA variation of straw mushroom in different experimental groups.

FIG. 7 is a graph showing hardness changes of volvariella volvacea in different experimental groups.

Detailed Description

The invention provides a nano-composite active packaging preservative film based on esterification modification and a preparation method and application thereof. Tartaric acid in the organic acid is non-toxic and free from peculiar smell, has antibacterial and antioxidant properties, and is widely applied to the food industry. The method comprises the steps of modifying CMNC by using tartaric acid, mixing the modified CMNC with bacteriostasis and antioxidation with PBAT in different proportions, granulating, forming a film by using an extrusion casting method, and performing experimental analysis on the preservation effect by using a film to preserve fruit and vegetable foods.

< preparation method of nano composite active packaging preservative film based on esterification modification >

The preparation method of the nano composite active packaging preservative film based on esterification modification comprises the following steps:

(1) carrying out esterification reaction on the organic acid and the CMNC to obtain modified CMNC; uniformly mixing dried modified CMNC, dried PBAT (purchased from the chemical company Wantong, Japan, trade name A400) and a chain extender, and extruding and granulating in an LSSHJ-20 twin-screw extruder to obtain modified CMNC/PBAT resin mixed particles;

(2) and casting the modified CMNC/PBAT resin mixed particles into a cast sheet by an LSJ-20 casting machine (Shanghai scientific rubber-plastic mechanical equipment Co., Ltd.), and then stretching transversely and longitudinally to obtain the nano composite active packaging preservative film (namely the modified CMNC/PBAT film) based on esterification modification.

Wherein, in the step (1), the mass ratio of the organic acid to the CMNC may be 1:1 to 1:5, preferably 1: 1.

In the step (1), the organic acid is one or more selected from tartaric acid, citric acid, gallic acid and caffeic acid.

In the step (1), as shown in fig. 1, when the organic acid and CMNC are subjected to esterification reaction, the CMNC is first heated and dissolved by dimethyl sulfoxide, then the organic acid and the catalyst are added, and the heating (heating by using an oil bath) reaction is continued; and after the reaction is finished, standing to room temperature, adding 95% ethanol to ensure that the CMNC after the reaction is completely precipitated, freezing and centrifuging, dissolving with absolute ethanol, repeating twice freezing and centrifuging to remove impurities, finally performing vacuum drying at 50 ℃, and grinding to obtain the modified CMNC (namely the esterification modified CMNC). After the organic acid is combined with the CMNC through ester bonds, the modified CMNC has the bacteriostatic and antioxidant effects of the organic acid, and can inhibit the growth of microorganisms in food and the oxidative loss of food nutrition.

Specifically, the volume of dimethyl sulfoxide was 20 times the mass of CMNC. The catalyst is p-toluenesulfonic acid, and the addition amount of the catalyst is 4 wt% of CMNC. The volume of 95% ethanol used for precipitation was 2 times the volume of dimethyl sulfoxide.

The temperature of the heating reaction can be 90-110 ℃, and is preferably 100 ℃; the time can be 6-8h, preferably 8 h.

The temperature of the refrigerated centrifugation can be 3-5 ℃, and is preferably 4 ℃; the rotation speed can be 7000-9000rpm, preferably 8000 rpm; the time can be 10-30min, preferably 20 min.

In step (1), the mass ratio of PBAT to modified CMNC is from 9:1 to 7: 3.

In the step (1), the drying temperature of the modified CMNC/PBAT is 50-70 ℃ and the drying time is 1-5 h.

In the step (1), the chain extender is a BASF chain extender ADR-4388, and the content of the chain extender is1 wt% of the total weight.

In step (1), the temperature in zones 1 to 7 in the twin-screw extruder may be: 135-145 ℃, 155-165 ℃, 165-175 ℃, 170-180 ℃, 165-175 ℃ and 165-175 ℃, preferably 140 ℃, 160 ℃, 170 ℃, 175 ℃, 170 ℃ and 170 ℃ respectively; the screw speed is 30-60r/min, preferably 40-50rpm, more preferably 50 rpm.

In step (2), the temperature of zone 1 to zone 7 in the casting machine may be: 135-145 ℃, 155-165 ℃, 165-175 ℃, 170-180 ℃, 165-175 ℃ and 165-175 ℃, preferably 140 ℃, 160 ℃, 170 ℃, 175 ℃, 170 ℃ and 170 ℃ respectively; the screw speed is 30-60r/min, preferably 40-50rpm, more preferably 50 rpm.

In the step (2), the average thickness of the nano composite active packaging preservative film based on esterification modification is 40-50 μm.

< nano composite active packaging preservative film based on esterification modification >

The nano composite active packaging preservative film based on esterification modification (namely the esterification modified antibacterial antioxidant degradable preservative film) is prepared by the preparation method.

Application of nano-composite active packaging preservative film based on esterification modification

The nano composite active packaging preservative film based on esterification modification can be applied to the field of food preservation.

The present invention will be further described with reference to the following specific examples.

Example 1:

(1) preparation of modified CMNC: heating and dissolving the CMNC by using dimethyl sulfoxide (the volume of the dimethyl sulfoxide is 20 times of the mass of the CMNC), then adding tartaric acid and p-toluenesulfonic acid (the addition amount of the p-toluenesulfonic acid is 4 wt% of the CMNC), and heating and reacting for 8h at 100 ℃ by using an oil bath; and after the reaction is finished, standing to room temperature, adding 95% ethanol to ensure that the CMNC after the reaction is completely precipitated, carrying out refrigerated centrifugation at the rotation speed of 8000rpm for 20min at 4 ℃, dissolving with absolute ethyl alcohol, repeating the refrigerated centrifugation twice, removing impurities, finally carrying out vacuum drying at 50 ℃, and grinding to obtain the modified CMNC.

(2) And melt blending: uniformly mixing 10 parts by weight of modified CMNC dried in vacuum, 90 parts by weight of PBAT (purchased from Tanhai Wantong chemical Co., Ltd., China) dried by air blast and 1 part by weight of chain extender ADR-4388 (the content is1 wt% of the total weight), adding the mixed material into a feeder of an LSSHJ-20 twin-screw extruder, feeding the material into a twin screw through the feeder, uniformly melting and mixing the material by the screw, extruding, granulating and drying to obtain the modified CMNC/PBAT resin mixed particle. Wherein the processing temperature of the double-screw extruder is 140-: the processing temperatures in zones 1 to 7 are 140 ℃, 160 ℃, 170 ℃, 175 ℃, 170 ℃ and 170 ℃ respectively.

(3) And casting film forming: the modified CMNC/PBAT resin mixed particles are melted and extruded by an LSJ-20 casting machine (Shanghai scientific rubber-plastic machinery equipment Co., Ltd.) to form a casting sheet, and then the casting sheet is transversely and longitudinally stretched to obtain the esterification modification based nano composite active packaging preservative film, wherein the thickness of the film is 40 mu m. Wherein the processing temperatures of the regions 1 to 7 in the casting machine are respectively 140 ℃, 160 ℃, 170 ℃, 175 ℃, 170 ℃ and 170 ℃, and the screw rotation speed is 50 rpm. The performance results are shown in table 1.

Example 2:

(2) And melt blending: uniformly mixing 20 parts by weight of modified CMNC dried in vacuum, 80 parts by weight of PBAT (purchased from Tanhai Wantong chemical Co., Ltd., China) dried by air blast and 1 part by weight of chain extender ADR-4388 (the content is1 wt% of the total weight), adding the mixed material into a feeder of an LSSHJ-20 twin-screw extruder, feeding the material into a twin screw through the feeder, uniformly melting and mixing the material by the screw, extruding, granulating and drying to obtain the modified CMNC/PBAT resin mixed particle. Wherein the processing temperature of the double-screw extruder is 140-: the processing temperatures in zones 1 to 7 are 140 ℃, 160 ℃, 170 ℃, 175 ℃, 170 ℃ and 170 ℃ respectively.

(3) And casting film forming: the modified CMNC/PBAT resin mixed particles are melted and extruded by an LSJ-20 casting machine (Shanghai scientific rubber and plastic machinery Co., Ltd.) to form a casting sheet, and then the casting sheet is transversely and longitudinally stretched to obtain the nano composite active packaging preservative film based on esterification modification, wherein the thickness of the film is 40 mu m. Wherein the processing temperatures of the regions 1 to 7 in the casting machine are respectively 140 ℃, 160 ℃, 170 ℃, 175 ℃, 170 ℃ and 170 ℃, and the screw rotation speed is 50 rpm. The performance results are shown in table 1.

Example 3:

(2) And melt blending: uniformly mixing 30 parts by weight of modified CMNC dried in vacuum, 70 parts by weight of PBAT (purchased from Tanhai Wantong chemical Co., Ltd., China) dried by air blast and 1 part by weight of chain extender ADR-4388 (the content is1 wt% of the total weight), adding the mixed material into a feeder of an LSSHJ-20 twin-screw extruder, feeding the material into a twin screw through the feeder, uniformly melting and mixing the material by the screw, extruding, granulating and drying to obtain the modified CMNC/PBAT resin mixed particle. Wherein the processing temperature of the double-screw extruder is 140-: the processing temperatures in zones 1 to 7 are 140 ℃, 160 ℃, 170 ℃, 175 ℃, 170 ℃ and 170 ℃ respectively.

Comparative example 1:

the blown and dried PBAT (100 parts by weight, purchased from the national institute of chemical technology, Zhuhaiwangtong, China, trade name A400) is cast into a film, and the processing temperatures of the 1 region to the 7 region in the casting machine are respectively 140 ℃, 160 ℃, 170 ℃, 175 ℃, 170 ℃ and the screw rotation speed is 50 rpm. The performance results are shown in table 1.

Comparative example 2:

CMNC was not modified and then 90 parts by weight of PBAT (available from seikaganton chemical limited, china, trade name a400) after air-drying was mixed with 10 parts by weight of unmodified CMNC dried under vacuum, otherwise the same as in example 1 above, wherein the contents of each component are in parts by weight. The performance results are shown in table 1.

Comparative example 3:

CMNC was not modified and then 80 parts by weight of PBAT (available from seikaganton chemical limited, china, trade name a400) after air-drying was mixed with 20 parts by weight of unmodified CMNC dried under vacuum, otherwise the same as in example 1 above, wherein the contents of each component are in parts by weight. The performance results are shown in table 1.

Comparative example 4:

CMNC was not modified and then 70 parts by weight of PBAT (available from seikaganton chemical limited, china, trade name a400) after air-drying was mixed with 30 parts by weight of unmodified CMNC dried under vacuum, otherwise the same as in example 1 above, wherein the contents of each component are in parts by weight. The performance results are shown in table 1.

The film is prepared by an extrusion casting method, and then the prepared film is subjected to mechanical property detection and preservation effect inspection.

<1> Fourier Infrared Spectroscopy (FTIR) of tartaric acid-modified CMNC:

FTIR measurements were performed on the films at room temperature in transmission mode using a FTIR spectrometer (Nicolet iS10, Thermo Fisher, USA). At 4cm^-1The spectral resolution of (a) was performed for 16 scans. Each spectrum is at 4000-400cm^-1Collected in the wavenumber range of (a), with air spectra as background correction.

1755-1670cm^-1The peak of stretching vibration is-C ═ O. As can be seen from FIG. 2, tartaric acidAt 1741cm^-1And 1700cm^-1Has a characteristic peak, and the unmodified CMNC is at 1722cm^-1Has a characteristic peak, and the modified CMNC is at 1722cm^-1Has a characteristic peak at 1700cm^-1New characteristic peaks appear. These results demonstrate that the tartrate-modified CMNC undergoes a chemical bond change, i.e., the formation of an ester bond, during the tartrate-modified CMNC.

<2> measurement of film index:

(1) oxygen Transmission Rate (OTR)

According to the national standard GB/T1038-2000, a sample is cut into a round shape by a special cutter, a G2/132 pressure difference method gas permeameter is selected, the initial temperature of the test is set to be 23 ℃, and the sample OTR is tested.

(2) Mechanical strength

Tensile Strength (TS) and Elongation At Break (EAB) of the biodegradable film were determined by tensile testing using an intelligent electronic tensile tester (JUN XLW (EC)) according to ASTM-D882-12(2012) at 25 ℃ and 90% Relative Humidity (RH). The strip film samples (15 mm. times.100 mm) were placed between the chucks with an initial chuck distance of 60mm and an experimental speed of 50 mm/min.

(3) Water Vapor Transmission Rate (WVTR)

The water vapor transmission rate of the film was measured by a WVTR meter (W-B-31E, Labstone, Guangxi, China) according to the principle of the weighing method and GB/T1037 under the conditions of 38 ℃ and 10% RH by using the weight reduction method.

TABLE 1 film property test results of examples and comparative examples

As can be seen from Table 1, as the amount of tartaric acid-CMNC added was increased, the mechanical strength of the composite film increased first and then decreased, and the PBAT composite film containing 10% tartaric acid-CMNC had the maximum TS (11.25MPa) and the maximum EAB (340.96%). In addition, the PBAT/CMNC nano composite membrane added with unmodified CMNC has lower mechanical strength than the PBAT/tartaric acid-CMNC nano composite membrane containing modified CMNC with the same content. The reason for this phenomenon may be that a smaller amount of CMNC (< 10%) has an enhancing effect on the mechanical strength of PBAT, but as the amount of CMNC increases, the compatibility of CMNC with PBAT decreases, so the mechanical strength of the PBAT/CMNC nanocomposite membrane decreases. However, the esterification modified CMNC can enhance the compatibility of CMNC and PBAT, so that the PBAT/CMNC nano composite membrane added with the modified CMNC has higher mechanical strength than the PBAT/tartaric acid-CMNC nano composite membrane containing unmodified CMNC in the same proportion.

As can be seen from table 1, as the addition amounts of CMNC and tartaric acid-CMNC increase, respectively, the OTR of the nanocomposite film increases, and the PBAT/tartaric acid-CMNC nanocomposite film with the modified CMNC has a smaller OTR than the PBAT/CMNC nanocomposite film with the same amount of unmodified CMNC. With respect to the WVTR of the film, since CMNC has hydrophilicity and PBAT has poor hydrophilicity, the WVTR of the PBAT hybrid film increases as the amount of CMNC added increases. And because the hydroxyl number is reduced and the hydrophilicity is weakened after the CMNC is esterified and modified, the PBAT/tartaric acid-CMNC nano composite membrane with the modified CMNC is smaller than the WVTR of the PBAT/CMNC nano composite membrane with the unmodified CMNC.

<3> application of straw mushroom preservation:

four experimental groups were set up, one with bare groups (no film wrap), one with the PBAT film wrap of comparative example 1, one with the PBAT/tartaric acid-CMNC film of example 3 and the PBAT/CMNC film wrap of comparative example 4, each group being set up in triplicate. The method comprises the steps of uniformly dividing fresh picked straw mushrooms in the market into 4 parts, wherein the weight of each part is 500 +/-2 g, subpackaging the obtained product in film bags, storing the film bags at a constant temperature of 16 ℃, and taking the straw mushrooms in each bag every 0h, 24h, 48h, 72h and 96h for index measurement.

(1) Appearance of straw mushroom

FIG. 3 is an appearance diagram of straw mushroom during preservation. The straw mushroom gradually autolyzes along with the prolonging of the storage time. The naked group of straw mushrooms has brown rot and strong ammonia odor after being stored for 24 hours, and the straw mushrooms shrink on the surface and become sticky after being stored for 48 hours, so that the surface mildews seriously and the edible value is completely lost. The autolysis speed of the straw mushroom in the PBAT/tartaric acid-CMNC packaging group is the slowest. After 96h of storage, the appearance of the straw mushrooms in the PBAT/tartaric acid-CMNC packaged group was the best compared to the other 3 groups of straw mushrooms.

(2) Polyphenol Oxidase (PPO) and Total Phenol Content (TPC)

PPO plays a key role in catalyzing the phenol hydroxylation process. PPO is the main cause of browning of volvariella volvacea. Enzymatic browning is also associated with the structure and integrity of cell membranes. FIG. 4 illustrates that the PPO activity of volvariella volvacea increases and then decreases with increasing storage time. The PPO activity of the naked volvariella volvacea is highest before 96 hours (P is less than 0.05). The PPO activity of the straw mushroom packaged by the PBAT/tartaric acid-CMNC film has no obvious rising trend before being stored for 72 h. All other groups had the highest PPO activity at 24 h. The research result proves that the PBAT/tartaric acid-CMNC film can more effectively inhibit the PPO activity of the straw mushroom. As shown in fig. 5, the TPC for the naked and packaged volvaria volvacea increased first and then gradually decreased. TPC of volvariella volvacea in PBAT/tartaric acid-CMNC film group was highest before 96 h. These results can be explained by the fact that PPO can oxidize phenol. PPO activity was lower in volvariella volvacea in PBAT/tartaric acid-CMNC membrane group (fig. 4). The accumulated phenolics showed antioxidant activity, which may help to reduce browning in mushrooms by maintaining membrane integrity.

(3) Malondialdehyde (malondiadehydee, MDA)

MDA is one of the major products of membrane lipid peroxidation, and its content is generally used as an index of lipid peroxidation, reflecting the degree of lipid peroxidation of cell membranes. As can be seen from FIG. 6, the MDA content of straw mushroom gradually increases with the storage time of straw mushroom. During the storage and preservation period, the MDA content of the straw mushroom in the PBAT/tartaric acid-CMNC film group is minimum, which shows that the membrane lipid peroxidation degree of the straw mushroom cell membrane in the PBAT/tartaric acid-CMNC film group is minimum, and the peroxidation damage to the straw mushroom cell membrane is minimum. This result is consistent with the appearance of the straw mushroom fruiting body shown in FIG. 3. The PBAT/tartaric acid-CMNC film has the strongest inhibition effect on the self-dissolving of the straw mushroom.

(4) Hardness of

Firmness is related to the ripeness of fruits and vegetables. The aging of mushrooms results in a soft texture characterized by a softening of the mushroom tissue. Softening may be due to degradation of the cell wall by bacterial enzymes and increased activity of endogenous autolytic proteins after harvesting. In the present invention, the hardness of volvariella volvacea decreased during storage (fig. 7). The hardness of straw mushrooms film-wrapped with PBAT/tartaric acid-CMNC was higher than the other groups, especially after 48h of storage. After 96h storage, the PBAT/tartaric acid-CMNC group reached 3.93N. The change in hardness is often associated with starch oxidation, which increases sugar content and water loss, and reduces turgor pressure. These results demonstrate that the PBAT/tartaric acid-CMNC film is effective in maintaining the hardness of volvariella volvacea.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. It will be readily apparent to those skilled in the art that various modifications to these embodiments and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments. Those skilled in the art should appreciate that many modifications and variations are possible in light of the above teaching without departing from the scope of the invention.

Claims

1. A preparation method of a nano composite active packaging preservative film based on esterification modification is characterized by comprising the following steps: which comprises the following steps:

(1) carrying out esterification reaction on organic acid and carboxymethyl nano-cellulose to obtain modified carboxymethyl nano-cellulose; mixing the dried modified carboxymethyl nano-cellulose, the dried poly (butylene adipate)/terephthalate and a chain extender, and extruding and granulating in a double-screw extruder to obtain mixed particles of the modified carboxymethyl nano-cellulose, the poly (adipate)/terephthalate resin;

(2) and carrying out tape casting film formation on the modified carboxymethyl nano-cellulose/poly adipic acid/butylene terephthalate resin mixed particles by a tape casting machine.

2. The preparation method of the nano-composite active packaging preservative film based on esterification modification according to claim 1, characterized in that: in the step (1), the mass ratio of the organic acid to the carboxymethyl nanocellulose is 1:1-1: 5.

3. The preparation method of the nano-composite active packaging preservative film based on esterification modification according to claim 1, characterized in that: in the step (1), the organic acid is one or more selected from tartaric acid, citric acid, gallic acid and caffeic acid.

4. The preparation method of the nano-composite active packaging preservative film based on esterification modification according to claim 1, characterized in that: in the step (1), when the organic acid and the carboxymethyl nanocellulose are subjected to esterification reaction, heating and dissolving the carboxymethyl nanocellulose by using dimethyl sulfoxide, then adding the organic acid and a catalyst, and continuing to perform heating reaction; cooling to room temperature after reaction, adding ethanol until the precipitation is complete, freezing and centrifuging, adding ethanol, repeatedly freezing and centrifuging, finally performing vacuum drying, and grinding to obtain modified carboxymethyl nano-cellulose;

preferably, the catalyst is p-toluenesulfonic acid, and the addition amount of the catalyst is 4 wt% of the carboxymethyl nanocellulose;

preferably, the heating reaction temperature is 90-110 ℃, and the time is 6-8 h;

preferably, the temperature of the refrigerated centrifugation is 3-5 ℃, the rotating speed is 7000-9000rpm, and the time is 10-30 min.

5. The preparation method of the nano-composite active packaging preservative film based on esterification modification according to claim 1, characterized in that: in the step (1), the mass ratio of the poly (butylene adipate/terephthalate) to the modified carboxymethyl nanocellulose is 9:1-7: 3;

preferably, in the step (1), the modified carboxymethyl nano-cellulose and the poly (butylene adipate/terephthalate) are dried at the temperature of 50-70 ℃ for 1-5 h.

6. The preparation method of the nano-composite active packaging preservative film based on esterification modification according to claim 1, characterized in that: in the step (1), the chain extender is a BASF chain extender ADR-4388.

7. The preparation method of the nano-composite active packaging preservative film based on esterification modification according to claim 1, characterized in that: in the step (1), the temperatures of the zones 1 to 7 in the double-screw extruder are respectively as follows: 145 ℃ for 135-.

8. The preparation method of the nano-composite active packaging preservative film based on esterification modification according to claim 1, characterized in that: in the step (2), the temperatures of the zone 1 to the zone 7 in the casting machine are respectively as follows: 145 ℃ for 135-.

9. A nanometer composite active packaging preservative film based on esterification modification is characterized in that: which is obtained by the production method according to any one of claims 1 to 8.

10. Use of the nanocomposite packaging cling film based on esterification modification according to claim 9 in food preservation applications.