CN115558140B - Method for preparing freshness indicating film based on purple sweet potato powder subjected to different heat treatments - Google Patents
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- C08J2405/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2401/00 or C08J2403/00
- C08J2405/04—Alginic acid; Derivatives thereof
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Abstract
The invention relates to a method for preparing a freshness indicating film based on different heat treatment purple sweet potato powder, which belongs to the field of food packaging and comprises the following steps: (1) Respectively steaming, boiling and baking fresh purple sweet potatoes, peeling, cutting into pieces, freeze-drying, crushing and sieving to obtain heat-treated purple sweet potato powder; (2) Suspending the heat-treated purple sweet potato powder in water, homogenizing by a high-speed disperser, and gelatinizing by a water bath to obtain a purple sweet potato powder suspension; (3) Adding a certain amount of sodium alginate into the purple sweet potato powder suspension obtained in the step (2) to obtain a purple sweet potato powder-sodium alginate mixed solution; (4) Adding glycerol into the mixed solution obtained in the step (3), and mixing by a magnetic stirrer to obtain a film-forming solution; (5) And pouring the obtained film forming solution into an organic glass mold, controlling humidity and air drying to form the film. The freshness indicating film prepared by the invention has the advantages of green preparation process and low production cost, and has application potential in the field of intelligent food packaging.
Description
Technical Field
The invention relates to a method for preparing a freshness indicating film based on purple sweet potato powder subjected to different heat treatments, belonging to the field of food packaging.
Background
In the field of intelligent food packaging, freshness indicating films are receiving a great deal of attention because of their ability to monitor the freshness of food in real time. Freshness indicating films are typically prepared by adding natural pigments (e.g., anthocyanins, betalains, curcumin, etc.) to a polysaccharide or protein matrix. Among them, anthocyanin is the most commonly used natural pigment, which can change molecular structure under different acid-base conditions and exhibits color change. Because food often accompanies changes in ph during spoilage, anthocyanin-containing films can indicate freshness of food by changing color exhibited under different acid-base environments. However, the existing anthocyanin film has high preparation cost and limits industrialization. On the one hand, in the preparation process of the anthocyanin film, organic solvents such as ethanol, methanol and the like are generally required to be used for extracting anthocyanin from the peel, pulp and petals of vegetables, fruits and flowers, and the anthocyanin film has adverse effects on the environment and the food safety; on the other hand, in the preparation process of anthocyanin films, polysaccharides, proteins and the like are usually required to be additionally added as a matrix of the film, so that the production cost is increased. Thus, there is a need to find a green, economical method for preparing anthocyanin films. In addition, anthocyanin is easy to change color under the action of heat, light and oxygen, and has low stability, so that practical application of the anthocyanin film is limited. Notably, the stability of anthocyanins is closely related to its chemical structure, and acylated anthocyanins have higher stability than non-acylated anthocyanins due to their intramolecular co-coloring effect, so naturally occurring acylated anthocyanins are more suitable for use in preparing freshness-indicating films.
The purple sweet potato is rich in acylated anthocyanin and is a proper raw material for preparing the freshness indicating film. Currently, there have been many researchers that extract anthocyanins from purple sweet potatoes and complex them with different polysaccharide matrices to prepare freshness-indicating films. However, a large amount of organic solvent is required in the anthocyanin extraction process, and other purple potato components (such as starch, dietary fiber and the like) except for anthocyanin are not effectively utilized, so that the existing film-forming method is neither economical nor environment-friendly; meanwhile, the existing researches fail to improve the stability of the purple sweet potato anthocyanin.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method for preparing a freshness indicating film based on different heat treatment purple sweet potato powder, which aims to overcome the defects of high production cost, insufficient utilization of raw materials, poor anthocyanin stability and the like in the preparation process of the conventional anthocyanin film.
The purpose of the invention is realized in the following way: the method for preparing the freshness indicating film based on the purple sweet potato powder subjected to different heat treatments is characterized by comprising the following steps of:
(1) Respectively steaming, boiling and baking fresh purple sweet potatoes, peeling, cutting into pieces, freeze-drying, crushing and sieving to obtain heat-treated purple sweet potato powder;
(2) Suspending the heat-treated purple sweet potato powder in water, homogenizing by a high-speed disperser, and gelatinizing by a water bath to obtain a purple sweet potato powder suspension;
(3) Adding a certain amount of sodium alginate into the purple sweet potato powder suspension obtained in the step (2) to obtain a purple sweet potato powder-sodium alginate mixed solution;
(4) Adding a certain amount of glycerol into the mixed solution obtained in the step (3), and mixing by a magnetic stirrer to obtain a film-forming solution;
(5) And pouring the obtained film forming solution into an organic glass mold, controlling humidity and air drying to form the film.
In the step (1), the steamed heat treatment is to put the purple sweet potatoes into a steamer to steam for 20-40 min; the heat treatment of boiling is to put purple sweet potatoes into boiling water to be boiled for 20-40 min; the baking heat treatment is to bake the purple sweet potatoes in an oven at 200-250 ℃ for 20-40 min; the dicing is to dice peeled purple sweet potatoes into blocks of 1 cm multiplied by 1 cm multiplied by 1 cm; the temperature of freeze drying is-45 to-50 ℃, and the freeze drying time is 24-48 hours; the crushing speed is 1500-2000 rpm, and the crushing time is 1-2 min; the mesh number of the sieved sieve is 100-150 meshes.
In the step (2), the speed of the high-speed disperser for homogenizing is 3000-5000 rpm, and the homogenizing time is 2-4 min; the gelatinization temperature of the water bath kettle is 80-100 ℃, and the gelatinization time is 10-20 min.
In the step (3), the mass ratio of the purple sweet potato powder to the sodium alginate in the purple sweet potato powder-sodium alginate mixed solution is 5-9:1, and the concentration of the purple sweet potato powder is 30-50 mg/mL.
In the step (4), the addition amount of the glycerol is 0.5% -0.8% of the total volume of the film forming solution; the rotating speed of the magnetic stirrer is 800-1000 r/min, and the stirring time is 60-90 min.
In the step (5), the size of the organic glass mould is 20-30 cm multiplied by 20-30 cm; when the film forming solution is subjected to humidity control and air drying, the humidity control and air drying conditions are 40% -50% of relative humidity, the temperature is 30% -40 ℃, and the humidity control and air drying time is 24-48 hours.
The purple sweet potato powder freshness indicating film based on different heat treatments is prepared by the method.
The method is advanced and scientific, fresh purple sweet potatoes are respectively subjected to heat treatment of steaming, boiling and baking, peeled, diced, freeze-dried, crushed and sieved to obtain heat-treated purple sweet potato powder, and then the freshness indicating film is prepared based on the heat-treated purple sweet potato powder. According to the invention, the stability of anthocyanin in the purple sweet potato is improved by carrying out heat treatment on fresh purple sweet potato, and simultaneously, starch, dietary fiber and anthocyanin in the purple sweet potato powder are comprehensively utilized to prepare the intelligent packaging film with the food freshness indicating function, so that the intelligent packaging film has the advantages of green preparation process and low production cost, and has application potential in the field of intelligent food packaging.
The invention has the beneficial effects that: the invention maintains the inherent color of the purple sweet potato through heat treatment such as steaming, boiling, baking and the like, and has a stabilizing effect on purple sweet potato anthocyanin; meanwhile, the purple sweet potato is subjected to heat treatment, so that the tissue of the purple sweet potato is softened and the starch is gelatinized, and a good matrix material is provided for the preparation of anthocyanin films; according to the invention, the freshness indicating film is prepared by directly utilizing the heat-treated purple sweet potato powder, so that the complicated anthocyanin extraction and purification process is avoided, the production cost is reduced, and the environment is protected; meanwhile, other components (such as starch and dietary fiber) of the purple sweet potato are comprehensively utilized, so that the production cost of the anthocyanin film is further reduced.
Drawings
FIG. 1 is a graph showing the analysis of total phenol content of different purple sweet potato powders used in example 1, example 2, example 3 and comparative example 1 of the present invention;
FIG. 1B is a graph showing the analysis of total anthocyanin content in various purple sweet potato powders used in example 1, example 2, example 3 and comparative example 1 of the present invention;
FIG. 1C is a graph showing the antioxidant activity analysis of different purple sweet potato powders used in example 1, example 2, example 3 and comparative example 1 of the present invention;
FIG. 1D is a graph showing the color development performance of anthocyanin in various purple sweet potato powders used in example 1, example 2, example 3 and comparative example 1 of the present invention;
FIG. 1E is a graph showing the film forming effect of the different purple sweet potato powders used in example 1, example 2, example 3 and comparative example 1 of the present invention;
FIG. 2A is a surface scanning electron microscope image of example 1, example 2, example 3 and comparative example 1 of the present invention;
FIG. 2B is a cross-sectional scanning electron microscope of example 1, example 2, example 3 and comparative example 1 of the present invention;
FIG. 3A is an infrared spectrum of the present invention of example 1, example 2, example 3 and comparative example 1;
FIG. 3B is an X-ray diffraction pattern of example 1, example 2, example 3 and comparative example 1 of the present invention;
fig. 4A is an ultraviolet-visible light transmittance analysis chart of example 1, example 2, example 3 and comparative example 1 of the present invention;
FIG. 4B is a graph showing the analysis of water vapor transmission rate of examples 1, 2, 3 and 1 of the present invention;
FIG. 4C is an analysis chart of oxygen transmission rate of the present invention in example 1, example 2, example 3 and comparative example 1;
FIG. 5 is a graph showing the mechanical properties of examples 1, 2, 3 and 1 of the present invention; in fig. 5, a is a tensile strength analysis chart, and B is an elongation at break analysis chart;
FIG. 6 is a thermogravimetric analysis of examples 1, 2, 3 and 1 of the present invention; in fig. 6, a is a TGA analysis chart and B is a DTG analysis chart;
FIG. 7 is a graph showing antioxidant activity of examples 1, 2, 3 and 1 of the present invention;
FIG. 8 is a graph showing the sensitivity analysis of the present invention in buffer solutions of different pH (3-12) and ammonia gas in example 1, example 2, example 3 and comparative example 1; a is a sensitivity analysis chart in buffers with different pH values (3-12), and B is a sensitivity analysis chart for ammonia;
fig. 9 is a graph of color stability analysis of inventive example 1, example 2, example 3 and comparative example 1 at different temperatures (4 ℃ and 25 ℃); a is a color stability analysis chart at 4 ℃ and B is a color stability analysis chart at 25 ℃;
FIG. 10 shows the delta at different temperatures (4 ℃ and 25 ℃) for example 1, example 2, example 3 and comparative example 1 of the present inventionEA value change map; in FIG. 10, A is delta at 4 degrees CelsiusEValue change diagram, B is delta at 25 deg.CEA value change map;
FIG. 11 shows application examples of the freshness monitoring of the prawns according to the present invention in example 1, example 2, example 3 and comparative example 1.
Detailed Description
The invention is described in further detail below with reference to the attached drawings and examples:
example 1
Freshness indicating film prepared based on steaming treatment of purple sweet potato powder;
cleaning fresh purple sweet potato, steaming in a steamer containing boiling water for 30 min, peeling, cutting into blocks of 1 cm ×1 cm ×1 cm, freeze drying at-50deg.C, pulverizing at 48 h and 2000 rpm for 1 min, and sieving with 100 mesh sieve to obtain steamed purple sweet potato powder.
Putting 6.8 g steamed purple sweet potato powder into a beaker, adding 170 mL distilled water, homogenizing for 2 min at room temperature by a high-speed disperser at a speed of 5000 rpm, and stirring for 15 min at 90 ℃ in a water bath kettle to completely gelatinize to obtain a purple sweet potato powder suspension; adding 1.36 g sodium alginate into the purple sweet potato powder suspension, and magnetically stirring at room temperature at 800 rpm for 30 min to obtain a purple sweet potato powder-sodium alginate mixed solution; dropwise adding glycerin 1.22 and g into the purple sweet potato powder-sodium alginate mixed solution, and magnetically stirring at room temperature at 800 rpm for 60 min to obtain a film-forming solution; pouring the film-forming solution into a plexiglass plate mold (24×24 cm) 2 ) Wherein the relative humidity is controlled to be 50%, the drying temperature is 30 ℃, the drying time is 48 and h, and the freshness indicating film prepared based on the steamed purple sweet potato powder is obtained and is named as S-PSP film.
Example 2
Freshness indicating film prepared based on hot cooking treatment of purple sweet potato powder;
the heat treatment method of the purple sweet potato in the embodiment 1 is changed into that of cleaning fresh purple sweet potato, putting the fresh purple sweet potato into a pot filled with boiling water, boiling for 30 min, and keeping the other preparation conditions unchanged, so as to obtain a freshness indicating film prepared based on the heat treatment of the purple sweet potato powder, and the freshness indicating film is named as B-PSP film.
Example 3
Freshness indicating film prepared based on baking heat treatment of purple sweet potato powder;
the heat treatment mode of the purple sweet potato in the embodiment 1 is changed into that of cleaning fresh purple sweet potato, and then the fresh purple sweet potato is put into an oven preheated to 230 ℃, baked for 30 minutes at 230 ℃ and the rest of preparation conditions are unchanged, so that the freshness indicating film prepared based on baked heat treated purple sweet potato powder is obtained and is named as R-PSP film.
Comparative example 1
A freshness indicating film prepared based on purple sweet potato powder without heat treatment;
the fresh purple sweet potato in the embodiment 1 is cleaned, peeled directly without heat treatment, cut into blocks of 1 cm multiplied by 1 cm multiplied by 1 cm, freeze-dried at-50 ℃ for 48 h at 2000 rpm, crushed for 1 min, sieved by a 100-mesh sieve to obtain raw purple sweet potato powder, and the rest preparation conditions are unchanged, so that a freshness indicating film prepared based on the purple sweet potato powder without heat treatment is obtained and named as PSP film.
1. The steamed purple sweet potato powder (S-PSP), the boiled and heat treated purple sweet potato powder (B-PSP), the roasted and heat treated purple sweet potato powder (R-PSP), the non-heat treated purple sweet potato powder (PSP) were tested for total phenol content, total anthocyanin content, antioxidant activity, anthocyanin color development performance and film forming effect, respectively, used in example 1, example 2, example 3 and comparative example 1, and the following results were obtained.
Adding 1 g of PSP, S-PSP, B-PSP and R-PSP powder into 40 mL of 75% ethanol solution, and extracting for 60 min under the conditions of ultrasonic power of 200W and frequency of 40 KHz; then 10000gCentrifuging for 15 min; repeating the above steps to extract residue again, and collecting supernatant; the supernatant was then analyzed for total phenol content, total anthocyanin content, antioxidant activity and differential retardationColor change in the wash (pH 3-12). The total phenol content was determined by the Fu Lin Fen method; determining the total anthocyanin content by a pH differential method; taking 1 mL supernatant and 3 mL of 100 mu mol/L DPPH methanol solution for reaction, and measuring the antioxidant activity of the supernatant; the color change of the solution was recorded with a digital camera by mixing 0.5 mL supernatant with 0.5 mL different buffer solutions (pH 3-12) at 20℃for 1 min.
As shown in fig. 1, the two heat treatments of steaming and boiling improved the total phenol content, total anthocyanin content and antioxidant activity in the purple sweet potato. However, the baking heat treatment reduces the total phenol content, total anthocyanin content, and antioxidant activity in the purple sweet potato. The different heat treatments did not significantly affect the color shifting ability of the PSP anthocyanins compared to the PSP. However, the film-forming solutions of PSP and R-PSP were reddish brown after gelatinization, while the film-forming solutions of S-PSP and B-PSP were dark purple after gelatinization. It is shown that both heat treatments of steaming and boiling help to maintain color stability of purple sweet potato anthocyanin during gelatinization film formation. And after film formation, the PSP and R-PSP films were reddish brown and the S-PSP and B-PSP films were dark purple. The S-PSP and B-PSP films are shown to better retain the inherent color of the purple sweet potato, namely the steamed and boiled heat-treated purple sweet potato powder can be directly used for preparing the film without anthocyanin extraction.
2. The microstructures, uv-visible light transmittance, water vapor transmittance, oxygen transmittance, mechanical properties, thermogravimetric properties, antioxidant activity, pH sensitivity, ammonia sensitivity and color stability of example 1, example 2, example 3 and comparative example 1 were tested, and the following results were obtained.
The surface and cross-sectional microstructure of the film was analyzed by scanning electron microscopy.
The surface and cross-sectional microstructures of PSP, S-PSP, B-PSP and R-PSP films are shown in FIGS. 2A and 2B, respectively. The PSP film has a non-uniform surface and cross-section. However, films prepared based on heat-treated purple sweet potato powder, particularly S-PSP and B-PSP films, have relatively uniform surfaces and cross sections. It is shown that both steaming and boiling heat treatments can significantly improve the uniformity of the film.
Fourier transform infrared spectrometer with attenuated total reflection mode was used at 400-4000 cm −1 And measuring infrared spectrograms of the films in a range.
As shown in FIG. 3A, PSP, S-PSP, B-PSP and R-PSP films have similar infrared spectra. It was shown that different heat treatments did not significantly alter the functional groups in the films.
The X-ray diffraction pattern of the film was measured using a polycrystalline X-ray diffractometer and scanned from 5℃to 75℃at a speed of 2℃per minute.
As shown in FIG. 3B, the PSP film is in an amorphous state, and films prepared based on heat-treated purple sweet potato powder, particularly S-PSP and B-PSP films, still partially retain the crystalline peaks of native starch at 15℃and 17-18 ℃. The S-PSP film and the B-PSP film are higher in stability.
The light blocking capacity was determined by scanning the film sample over the range of 200-800 nm using an ultraviolet/visible spectrophotometer.
As shown in FIG. 4A, the transmittance of PSP, S-PSP, B-PSP and R-PSP films in the range of 200-800-nm was less than 20%, indicating that the films have excellent light blocking ability. At 370-600 nm, PSP and R-PSP films have relatively high light blocking capability, while S-PSP and B-PSP films exhibit similar light blocking capability.
The water vapor transmission rate (WVP) of the film was measured using a gravimetric method.
As shown in FIG. 4B, the WVP of the PSP, S-PSP, B-PSP and R-PSP films is 26.9-30.1X10 −11 g m −1 s −1 Pa −1 Indicating that the film has a certain water vapor barrier capability. Meanwhile, S-PSP and B-PSP films have relatively low WVP.
The Oxygen Permeability (OP) of the film was measured by a gas permeability tester.
As shown in FIG. 4C, the OP of the PSP, S-PSP, B-PSP and R-PSP films is in the range of 0.55-0.73 cm 3 mm m −2 day −1 atm −1 Indicating that the film has a certain oxygen barrier capability. Meanwhile, the S-PSP and B-PSP films have relatively low OP.
The Tensile Strength (TS) and Elongation At Break (EAB) of the films were measured by a universal tensile tester.
As shown in fig. 5, the TS of the S-PSP and B-PSP films were significantly higher than the PSP and R-PSP films; the EAB of S-PSP, B-PSP and R-PSP films prepared based on different heat-treated purple sweet potato powders was significantly higher than PSP films. The S-PSP and B-PSP films are shown to have better mechanical properties.
TGA of the film was determined using a thermogravimetric analyzer. TGA and Derivative of TGA (DTG) curves were recorded with a high purity nitrogen blanket at a flow rate of 20 mL/min at a temperature ranging from room temperature to 700 ℃.
As shown in FIG. 6, the TGA and DTG curves of PSP, S-PSP, B-PSP and R-PSP films have 3 characteristic thermal decomposition stages. The second weight loss stage (170-390 ℃) is the main thermal decomposition process. PSP and R-PSP films have maximum decomposition rates at 240℃and 236℃respectively. In contrast, the maximum decomposition rate of S-PSP and B-PSP films was higher in temperature (about 254 ℃). It is shown that S-PSP and B-PSP films have higher thermal stability than PSP and R-PSP films.
The antioxidant activity was calculated by measuring the radical scavenging rate of a 1 mg membrane sample after reaction with 3 mL 100. Mu. Mol/L DPPH methanol solution for 30 min at 20℃in the dark using Trolox as a positive control, and the result was expressed in. Mu. Mol Trolox equivalent/g membrane.
As shown in FIG. 7, the S-PSP and B-PSP films exhibited high antioxidant activity.
Immersing the film in different buffers (pH 3-12) for 1 min, and recording the color change of the film; in addition, the film was placed in an ammonia (1 mol/L ammonia solution) environment for 90 min, and the film color change was recorded.
As shown in FIG. 8, the color change of the S-PSP and B-PSP films was more pronounced in different pH buffers and ammonia environments. The S-PSP film and the B-PSP film have better color-changing capability and have greater application potential in intelligent packaging.
The films were stored for 30 days in environments with 50% relative humidity at different temperatures (4 ℃ and 25 ℃) and delta for film samples were measured every three daysEValues.
As shown in fig. 9A and 9B, no significant color change was observed for all films at different temperatures. As shown in fig. 10A and 10B, all filmsShows only a small delta under different storage conditionsEValue change (delta at 4 ℃ C.)E <Delta at 2, 25 °cE <3) Indicating that all films have good storage stability.
3. The results obtained by using example 1, example 2, example 3 and comparative example 1 for monitoring freshness of shrimps are as follows.
Adhering the film sample to the inner top of a polypropylene container (diameter 12 cm, height 4 cm); then, about 170 g fresh shrimp were placed at the bottom of the container and stored at 4 ℃ for 6 days; the color of the film and the total volatile basic nitrogen (TVB-N) content of the shrimp were measured once every 24 h.
The TVB-N value is a commonly used shrimp freshness evaluation index, and when the TVB-N value is lower than 20 mg/100 g, the shrimp is fresh. During the cold storage of shrimp, its TVB-N value increases from the original 5.10 mg/100 g to the final 45.75 mg/100 g; the shrimp reached a TVB-N value of 23.11 mg/100 g on the third day, indicating that the shrimp was not edible at this time. As shown in FIG. 11, the PSP, S-PSP, B-PSP and R-PSP films all exhibited color changes within 6 days. The reddish brown color of the PSP and R-PSP films became progressively darker with prolonged storage time. On the third day, the S-PSP and B-PSP films changed color from the original purple to blue-purple, and therefore, the color changes of the S-PSP and B-PSP films were more easily perceived by the consumer. The results show that the freshness of the shrimps can be effectively monitored by observing the color change of the S-PSP film and the B-PSP film.
In summary, the film prepared by steaming and boiling heat treatment of the purple sweet potato powder is preferably selected, has a denser microstructure, and has good water vapor and oxygen blocking capability, mechanical property, thermal stability, antioxidation activity, pH sensitivity and ammonia sensitivity. Experimental results of film application show that the film prepared based on the steamed and boiled heat-treated purple sweet potato powder can effectively monitor the freshness of shrimps, and has application potential in the field of intelligent food packaging.
The above is only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited by this, and any modification made on the basis of the technical scheme according to the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (6)
1. The method for preparing the freshness indicating film based on the purple sweet potato powder subjected to different heat treatments is characterized by comprising the following steps of:
(1) Respectively steaming, boiling and baking fresh purple sweet potatoes, peeling, cutting into pieces, freeze-drying, crushing and sieving to obtain heat-treated purple sweet potato powder; the steaming heat treatment is to put the purple sweet potatoes into a steamer to steam for 20-40 min; the heat treatment of boiling is to put purple sweet potatoes into boiling water to be boiled for 20-40 min; the baking heat treatment is to bake the purple sweet potatoes in an oven at 200-250 ℃ for 20-40 min; the dicing is to dice peeled purple sweet potatoes into blocks of 1 cm multiplied by 1 cm multiplied by 1 cm; the temperature of freeze drying is-45 to-50 ℃, and the freeze drying time is 24-48 hours; the crushing speed is 1500-2000 rpm, and the crushing time is 1-2 min; the mesh number of the sieved sieve is 100-150 meshes;
(2) Suspending the heat-treated purple sweet potato powder in water, homogenizing by a high-speed disperser, and gelatinizing by a water bath to obtain a purple sweet potato powder suspension;
(3) Adding a certain amount of sodium alginate into the purple sweet potato powder suspension obtained in the step (2) to obtain a purple sweet potato powder-sodium alginate mixed solution;
(4) Adding a certain amount of glycerol into the mixed solution obtained in the step (3), and mixing by a magnetic stirrer to obtain a film-forming solution;
(5) And pouring the obtained film forming solution into an organic glass mold, controlling humidity and air drying to form the film.
2. The method for preparing the freshness indicating film based on the purple sweet potato powder subjected to different heat treatments according to claim 1, wherein the method comprises the following steps of: in the step (2), the speed of the high-speed disperser for homogenizing is 3000-5000 rpm, and the homogenizing time is 2-4 min; the gelatinization temperature of the water bath kettle is 80-100 ℃, and the gelatinization time is 10-20 min.
3. The method for preparing the freshness indicating film based on the purple sweet potato powder subjected to different heat treatments according to claim 1, wherein the method comprises the following steps of: in the step (3), the mass ratio of the purple sweet potato powder to the sodium alginate in the purple sweet potato powder-sodium alginate mixed solution is 5-9:1, and the concentration of the purple sweet potato powder is 30-50 mg/mL.
4. The method for preparing the freshness indicating film based on the purple sweet potato powder subjected to different heat treatments according to claim 1, wherein the method comprises the following steps of: in the step (4), the addition amount of the glycerol is 0.5% -0.8% of the total volume of the film forming solution; the rotating speed of the magnetic stirrer is 800-1000 rpm, and the stirring time is 60-90 min.
5. The method for preparing the freshness indicating film based on the purple sweet potato powder subjected to different heat treatments according to claim 1, wherein the method comprises the following steps of: in the step (5), the size of the organic glass mould is 20-30 cm multiplied by 20-30 cm; when the film forming solution is subjected to humidity control and air drying, the humidity control and air drying conditions are 40% -50% of relative humidity, the temperature is 30% -40 ℃, and the humidity control and air drying time is 24-48 hours.
6. A film for indicating freshness of purple sweet potato powder based on different heat treatments prepared by the method of any one of claims 1 to 5.
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| CN103739883A (en) * | 2014-01-24 | 2014-04-23 | 福建农林大学 | Purple potato starch edible film and preparation method thereof |
| CN103876073A (en) * | 2014-04-10 | 2014-06-25 | 中国包装和食品机械有限公司 | Preparation technology of potato whole powder |
| CN107082896A (en) * | 2017-05-02 | 2017-08-22 | 上海海洋大学 | A kind of intelligence colour developing antibacterial oxidation resistanct fresh-keeping method for manufacturing thin film |
| CN107686565A (en) * | 2017-08-26 | 2018-02-13 | 安徽巢湖南方膜业有限责任公司 | A kind of prepared food packaging film and preparation method thereof |
| CN114989465A (en) * | 2022-06-09 | 2022-09-02 | 东北农业大学 | Preparation method of sodium alginate-purple sweet potato peel anthocyanin intelligent indicating film for monitoring freshness of chicken |
| CN115165870A (en) * | 2022-08-01 | 2022-10-11 | 浙江海洋大学 | Penaeus vannamei freshness indicating colorimetric film and preparation method and application thereof |
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| CN110078958A (en) * | 2019-04-28 | 2019-08-02 | 齐鲁工业大学 | A kind of preparation method and application of bacteriostatic activity food package film |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103739883A (en) * | 2014-01-24 | 2014-04-23 | 福建农林大学 | Purple potato starch edible film and preparation method thereof |
| CN103876073A (en) * | 2014-04-10 | 2014-06-25 | 中国包装和食品机械有限公司 | Preparation technology of potato whole powder |
| CN107082896A (en) * | 2017-05-02 | 2017-08-22 | 上海海洋大学 | A kind of intelligence colour developing antibacterial oxidation resistanct fresh-keeping method for manufacturing thin film |
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| CN114989465A (en) * | 2022-06-09 | 2022-09-02 | 东北农业大学 | Preparation method of sodium alginate-purple sweet potato peel anthocyanin intelligent indicating film for monitoring freshness of chicken |
| CN115165870A (en) * | 2022-08-01 | 2022-10-11 | 浙江海洋大学 | Penaeus vannamei freshness indicating colorimetric film and preparation method and application thereof |
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