阅读说明：本技术 一种鲜笋保鲜涂膜剂及其制备方法 (Fresh bamboo shoot preservation coating agent and preparation method thereof ) 是由 童龙 李彬 耿养会 陈丽洁 张磊 李红艳 于 2020-07-20 设计创作，主要内容包括：本发明公开了一种鲜笋保鲜涂膜剂及其制备方法,涉及果蔬保鲜技术领域,包括以下重量份数的原料：壳聚糖10-20份、酒石酸5-8份、大豆分离蛋白5-10份、硬脂酸3-5份、多孔淀粉5-12份、聚赖氨酸3-5份、纳米蒙脱土0.5-1.5份、薄荷精油微胶囊1-5份,纳米蒙脱土上负载有茶多酚,薄荷精油微胶囊以β-环糊精作为囊壁材料。本发明的鲜笋保鲜涂膜剂成本低、使用简便易行、成膜性好、无毒可食,形成的膜层能够持续有效地抑制鲜笋水分蒸发、延缓呼吸代谢以及抵御病原微生物的作用,鲜笋的硬度及木质素增加少,失水率低,能够有效保护鲜笋的色泽和气味,延长鲜笋的保鲜时间。(The invention discloses a fresh bamboo shoot preservation coating agent and a preparation method thereof, relating to the technical field of fruit and vegetable preservation, and comprising the following raw materials in parts by weight: 10-20 parts of chitosan, 5-8 parts of tartaric acid, 5-10 parts of soybean protein isolate, 3-5 parts of stearic acid, 5-12 parts of porous starch, 3-5 parts of polylysine, 0.5-1.5 parts of nano montmorillonite and 1-5 parts of mint essential oil microcapsule, wherein the nano montmorillonite is loaded with tea polyphenol, and the mint essential oil microcapsule takes beta-cyclodextrin as a capsule wall material. The fresh bamboo shoot preservation film coating agent is low in cost, simple and easy to use, good in film forming property, non-toxic and edible, the formed film layer can continuously and effectively inhibit water evaporation of the fresh bamboo shoots, delay respiratory metabolism and resist the action of pathogenic microorganisms, the hardness and lignin of the fresh bamboo shoots are slightly increased, the water loss rate is low, the color and the smell of the fresh bamboo shoots can be effectively protected, and the preservation time of the fresh bamboo shoots is prolonged.)

1. The fresh bamboo shoot preservation coating agent is characterized by comprising the following raw materials in parts by weight: 10-20 parts of chitosan, 5-8 parts of tartaric acid, 5-10 parts of soybean protein isolate, 3-5 parts of stearic acid, 5-12 parts of porous starch, 3-5 parts of polylysine, 0.5-1.5 parts of nano montmorillonite and 1-5 parts of mint essential oil microcapsule, wherein the nano montmorillonite is loaded with tea polyphenol, and the mint essential oil microcapsule takes beta-cyclodextrin as a capsule wall material.

2. The preparation method of the fresh bamboo shoot preservation coating agent as claimed in claim 1, characterized by comprising the following steps:

s1, adding the porous starch into deionized water, magnetically stirring for 20-30min in a constant-temperature water bath at 95 ℃, cooling to 60 ℃, adding stearic acid, continuously stirring for 1h to obtain a starch gelatinization mixed solution, and cooling to room temperature for later use;

s2, adding the soy protein isolate into deionized water, adding polylysine, and magnetically stirring for 20-30min in a constant-temperature water bath at 20 ℃ to obtain a protein mixed solution;

s3, adding tartaric acid into deionized water, stirring uniformly, adding chitosan at 70 ℃ while stirring, and continuously stirring for 60-80min to obtain a chitosan acid solution;

s4, uniformly stirring the starch gelatinization mixed liquor, the protein mixed liquor and the chitosan acid liquor, adding the tea polyphenol-loaded nano montmorillonite and mint essential oil microcapsules, and continuously stirring for 20-30min to obtain the fresh-keeping film coating agent.

3. The method for preparing a fresh bamboo shoot preservation coating agent as claimed in claim 2, wherein the stirring conditions in S4 are as follows: the temperature is 20-40 ℃, the stirring speed is 1200r/min, and the stirring time is 10-15 min.

4. The preparation method of the fresh bamboo shoot preservation coating agent according to claim 3, wherein the method for loading tea polyphenol on the nano montmorillonite is as follows:

taking 10 parts by weight of nano montmorillonite, adding 300 parts by weight of 20 wt% ethanol solution, stirring for 12-24h, then adding 0.3 part by weight of nano montmorillonite and 3 parts by weight of 3 wt% tea polyphenol, dispersing for 30min under 80-100KW ultrasonic wave to obtain suspension, and then distilling the suspension under reduced pressure to remove the solvent to obtain the tea polyphenol-loaded nano montmorillonite.

5. The preparation method of the fresh bamboo shoot preservation coating agent as claimed in claim 4, wherein the preparation method of the porous starch is as follows:

adding 780 parts by weight of buffer solution consisting of disodium hydrogen phosphate and citric acid into 100 parts by weight of wheat starch, and uniformly mixing to obtain starch emulsion; preheating the obtained starch emulsion in a constant-temperature water bath kettle at 50 ℃ for 15min, then respectively taking alpha-amylase and saccharifying enzyme which are equal to the wheat starch, mixing, and adding deionized water for dilution to obtain diluted enzyme solution; adding the diluted enzyme solution into the starch emulsion for enzymolysis for 5 hours, adding 1500 parts by weight of 4 wt% sodium hydroxide solution after the reaction is finished to terminate the reaction, centrifuging, carrying out suction filtration on the precipitate, washing the suction-filtered precipitate for 3-4 times, drying in a 60 ℃ oven, and crushing to obtain the porous starch.

6. The preparation method of the fresh bamboo shoot preservation coating agent according to claim 5, wherein the preparation method of the mint essential oil microcapsule is as follows:

adding 20 parts by weight of beta-cyclodextrin into 60 parts by weight of deionized water, stirring for 30min at the rotating speed of 400r/min to obtain a beta-cyclodextrin aqueous solution, slowly adding 4 parts by weight of peppermint essential oil into the beta-cyclodextrin aqueous solution, reacting for 4h at the water bath temperature of 40 ℃ and the rotating speed of 400r/min after the addition is finished, cooling to room temperature after the reaction is finished, and filtering, washing and freeze-drying precipitated solids to obtain the peppermint essential oil microcapsules.

Technical Field

The invention relates to the technical field of fruit and vegetable preservation, in particular to a fresh bamboo shoot preservation coating agent and a preparation method thereof.

Background

Bamboo shoots are tender plant stems grown from the soil of bamboo at first, are delicious in taste, crisp and tender in meat quality, unique in flavor and rich in nutrition, and have been recorded in literature of Chinese people in the invar period, are traditional food in China and are favorite vegetables of people. Bamboo shoots contain 18 amino acids, some of which are essential for human body, and 100g of bamboo shoots contain about 2g of amino acids in total, and also contain various trace elements necessary for human body, such as Se, Ge, etc. Bamboo shoots are known as "health foods" because bamboo shoots have high protein, low fat, and trace elements such as se, and rich dietary fibers, can effectively improve digestive function, and can prevent hypertension, cardiovascular and cerebrovascular diseases and cancers.

China is a big world for bamboo shoot production, and the yield of bamboo shoots is the first world. However, the production area of bamboo shoots is mainly in mountainous areas, and the harvesting period is often concentrated in high temperature and high humidity in spring and summer. After the bamboo shoots are harvested, because the water content is high, the respiration is vigorous, a large amount of nutrient substances in the bodies are metabolized and consumed by the bamboo shoots, the bamboo shoots are easy to lose water and age, particularly, the lignification process of the bamboo shoots can be accelerated due to the change of the physiological environment after the bamboo shoots are harvested, in addition, phenolic substances (tannin, tyrosine and the like) in the bamboo shoots can be oxidized into quinone substances to cause browning of the bamboo shoots, the commodity value and the edible value are lost at normal temperature for 2-3 days, and the storage and the transportation of the bamboo. In recent years, the demand of people for natural foods is increasing, the awareness of food safety is increasing, and at present, bamboo shoots have high commodity value in markets at home and abroad, so the research on storage and preservation of bamboo shoots is very important.

Disclosure of Invention

In view of the above, the invention aims to provide a fresh bamboo shoot preservation coating agent, wherein a layer of non-toxic edible film is formed on the surface of a bamboo shoot to inhibit the evaporation of water in the fresh bamboo shoot, delay respiratory metabolism and resist pathogenic microorganisms.

The invention solves the technical problems by the following technical means:

a fresh bamboo shoot preservation coating agent comprises the following raw materials in parts by weight: 10-20 parts of chitosan, 5-8 parts of tartaric acid, 5-10 parts of soybean protein isolate, 3-5 parts of stearic acid, 5-12 parts of porous starch, 3-5 parts of polylysine, 0.5-1.5 parts of nano montmorillonite, 1-5 parts of mint essential oil microcapsule and a plurality of parts of deionized water, wherein the nano montmorillonite is loaded with tea polyphenol, and the mint essential oil microcapsule takes beta-cyclodextrin as a capsule wall material.

In addition, the invention also provides a preparation method of the fresh bamboo shoot preservation coating agent, which comprises the following steps:

s1, adding the porous starch into deionized water, magnetically stirring for 20-30min in a constant-temperature water bath at 95 ℃, cooling to 60 ℃, adding stearic acid, continuously stirring for 1h to obtain a starch gelatinization mixed solution, and cooling to room temperature for later use;

s2, adding the soy protein isolate into deionized water, adding polylysine, and magnetically stirring for 20-30min in a constant-temperature water bath at 20 ℃ to obtain a protein mixed solution;

s3, adding tartaric acid into deionized water, stirring uniformly, adding chitosan at 70 ℃ while stirring, and continuously stirring for 60-80min to obtain a chitosan acid solution;

s4, uniformly stirring the starch gelatinization mixed liquor, the protein mixed liquor and the chitosan acid liquor, adding the tea polyphenol-loaded nano montmorillonite and mint essential oil microcapsules, and continuously stirring for 20-30min to obtain the fresh-keeping film coating agent.

Further, the stirring conditions described in S4 are: the temperature is 20-40 ℃, the stirring speed is 1200r/min, and the stirring time is 10-15 min.

Further, the method for loading tea polyphenol on the nano montmorillonite is as follows:

taking 10 parts by weight of nano montmorillonite, adding 300 parts by weight of 20 wt% ethanol solution, stirring for 12-24h, then adding 0.3 part by weight of nano montmorillonite and 3 parts by weight of 3 wt% tea polyphenol, dispersing for 30min under 80-100KW ultrasonic wave to obtain suspension, and then distilling the suspension under reduced pressure to remove the solvent to obtain the tea polyphenol-loaded nano montmorillonite.

The tea polyphenol-loaded nano montmorillonite can improve the mechanical property, the water resistance, the water vapor barrier property and the oxidation resistance of a film layer after the preservative is formed into a film, and can inhibit the gas exchange between bamboo shoots and air, so that the respiration of fresh bamboo shoots is inhibited, the consumption of nutrient substances is further reduced, and the aging of the bamboo shoots is delayed; can also reduce the evaporation and water loss of the bamboo shoots and keep the hardness and freshness of the bamboo shoots.

Further, the preparation method of the porous starch comprises the following steps:

taking 100 parts by weight of wheat starch, and adding 780 parts by weight of buffer solution consisting of disodium hydrogen phosphate and citric acid, wherein the buffer solution is prepared from 0.2mol/L disodium hydrogen phosphate and 0.1mol/L citric acid according to the mass ratio of 1:1.27, and the pH value of the buffer solution is 4.8 to obtain starch emulsion;

preheating the obtained starch emulsion in a constant-temperature water bath kettle at 50 ℃ for 15min, then respectively taking alpha-amylase and saccharifying enzyme which are equal to wheat starch in quantity, mixing, adding deionized water for dilution to obtain diluted enzyme liquid, adding the diluted enzyme liquid into the starch emulsion for enzymolysis reaction for 5h, adding a sodium hydroxide solution which is 4 wt% of 1500 parts by weight after the reaction is finished to terminate the reaction, then centrifuging, carrying out suction filtration on the precipitate, washing the suction-filtered precipitate for 3-4 times, then drying in an oven at 60 ℃, and crushing to obtain the porous starch.

The porous starch is a novel modified starch with a honeycomb structure and a large specific surface area, is used as an economic biodegradable adsorbent, and has a protection effect on substances which are easily oxidized or decomposed in the atmosphere or under illumination, such as vitamins, pigments and the like.

Further, the preparation method of the peppermint essential oil microcapsule comprises the following steps:

adding 20 parts by weight of beta-cyclodextrin into 60 parts by weight of deionized water, stirring for 30min at the rotating speed of 400r/min to fully disperse the beta-cyclodextrin to obtain a beta-cyclodextrin aqueous solution, slowly adding 4 parts by weight of mint essential oil into the beta-cyclodextrin aqueous solution, reacting for 4h at the water bath temperature of 40 ℃ and the rotating speed of 400r/min after the addition is finished, cooling to room temperature after the reaction is finished, and filtering, washing and freeze-drying precipitated solids to obtain the mint essential oil microcapsules.

The mint essential oil microcapsule can continuously and slowly release mint essential oil, continuously inhibit the growth of microorganisms and prevent fresh bamboo shoots from rotting.

The invention has the beneficial effects that: the fresh bamboo shoot preservation film coating agent is low in cost, simple and easy to use, good in film forming property, non-toxic and edible, the formed film layer can continuously and effectively inhibit water evaporation of the fresh bamboo shoots, delay respiratory metabolism and resist the action of pathogenic microorganisms, the hardness and lignin of the fresh bamboo shoots are slightly increased, the water loss rate is low, the color and the smell of the fresh bamboo shoots can be effectively protected, and the preservation time of the fresh bamboo shoots is prolonged.

Detailed Description

The present invention will be described in detail with reference to examples below: