CN101775222A - Whey protein/TiO2 edible composite membrane and preparation method thereof - Google Patents

Abstract

The invention discloses a whey protein/TiO2 edible composite membrane, which belongs to the field of functional dairy products and food packaging. The composite membrane is prepared by mixing whey protein solution with TiO2 in the presence of an added plasticiser, wherein the weight ratio of the nanometer TiO2 and the whey protein is (0.1-2):100, the mass percentage concentration of the whey protein solution is 7-12%, and the thickness of the composite membrane is 90-115um. The invention also discloses a preparation method of the composite membrane. The composite membrane can reduce the food spoilage caused by the ultraviolet irradiation effectively, thereby prolonging the shelf life of the food, further has strong mechanical intensity and decreases the water vapour transmission rate.

Description

A kind of whey-protein/TiO 2Edible composite membrane and preparation method thereof

Technical field

The invention belongs to functional dairy products and food product pack field, be specifically related to a kind of whey-protein/TiO ₂Edible composite membrane and preparation method thereof.This composite membrane has the uvioresistant effect, can add the nano-TiO of different amounts as required ₂And obtain the composite membranes of different whites.

Background technology

Traditional wrapping material are cheap, and are easy to process, but cause environmental pollution because of it can't be degraded by microorganisms, the health of harm humans.Along with the raising day by day of people's living standard, people are the concern for the environment safety problem more and more, therefore " Green Packaging " cause that people more and more pay attention to.Wherein fine quality such as safe, nontoxic, pollution-free and edibility receives increasing concern to edible film with it, and the gesture that replaces the conventional plastic packing is arranged.

Edible film is (as lipid with the edible natural material; polysaccharide; protein etc.) be raw material; add edible softening agent, linking agent etc.; by the differing molecular interphase interaction; and be covered in food surfaces or inner film with forms such as parcel, coating, microcapsule, and can intercept the infiltration of aqueous vapor, oxygen or various solutes, food is shielded.At present more is with lipid, polysaccharide, protein etc. is the edible film that raw material is made.For example, publication number is the novel process that please introduce a kind of preparing esculent film using glutamine transaminage modified protein in the Chinese patent of CN101199314; Publication number is the preparation method that the Chinese patent application of CN101538407 has been introduced a kind of aleuronat/methyl cellulose composite edible film.

Whey-protein is one of byproduct during cheese is produced.Whey-protein is a class key protein that exists in the milk whey, has very high nutritive value and biological value.The Whey protein edible single wrapping material are a kind of resource-type wrapping material that do not have waste, and resource is utilized, and meet the friendly type social requirement of contemporary continuable development principle and built environment.

In recent years, whey-protein is as the edible film base-material and because of its good nutritive property and film forming ability, and becomes the focus of research.For example, publication number is please introduce the preparation method that a kind of whey-protein is the edible film of matrix in 200710190608.5 the Chinese patent; Publication number is that 200910079773.2 Chinese patent application has been introduced lactalbumin membrane and preparation method thereof and application.

Food can be induced putrid and deteriorated at the storage middle-ultraviolet lamp, and at present is that the edible film of base-material is relatively poor to ultraviolet blocking capability with the whey-protein, and the anti-uv-ray that therefore improves food product pack is imperative.Nano-TiO ₂Oxidation activity is higher, chemical stability good, environmentally safe, to the human body toxicological harmless, and low, the applied range of cost is one of nano-photocatalyst material of present widespread use.But, do not see as yet both at home and abroad at present and in lactalbumin membrane, add nano-TiO ₂Relevant report with the shielding of ultraviolet irradiation.

Summary of the invention

The object of the present invention is to provide a kind of whey-protein/TiO ₂Edible composite membrane.

Another object of the present invention is to provide a kind of above-mentioned whey-protein/TiO ₂The preparation method of edible composite membrane.

A kind of whey-protein/TiO ₂Edible composite membrane, this composite membrane are with lactoalbumin soln and nano-TiO under the situation of adding softening agent ₂Mix and make, wherein, nano-TiO ₂With the weight ratio of whey-protein be (0.1-2): 100.

The mass volume ratio concentration of described lactoalbumin soln is 7-12%, and solvent is a water.

Described whey-protein is whey isolate protein (whey protein isolate is called for short WPI).

Used nano-TiO ₂The particle grain size scope is at 20-100nm.

The thickness of described composite membrane is 90-115 μ m, and tensile strength is 5.29-11.15N/mm ², the water vapour transmission coefficient is 1.25-1gmm/hm ²KPa, transmittance is respectively 68.95-1.11% and 79.77-6.23% at visible light 400nm and 800nm place.

A kind of whey-protein/TiO ₂The preparation method of edible composite membrane comprises following operation steps:

(1) be that the lactoalbumin soln of 7-12% continues to stir on magnetic stirring apparatus with mass percent concentration, treat that it fully dissolves after, regulate pH to 7-9;

(2) step (1) gained solution is heated 20-40min in 70-90 ℃ of water-bath, to be cooled to room temperature, add softening agent, wherein, the weight ratio of softening agent and whey-protein is (0.4-0.6): 1;

(3) in step (2) gained solution, add nano-TiO again ₂, be stirred well to nano-TiO ₂Disperse the back ultrasonic degas fully, obtain film forming liquid, wherein, nano-TiO ₂With the weight ratio of whey-protein be (0.1-2): 100;

(4) above-mentioned film forming liquid is joined in the flat synthetic glass vessel, wherein, the consumption of film forming liquid is 0.09-0.1g/cm ², at 20-24 ℃, relative humidity is balance 48h at least under the condition of 54-58%, makes the composite membrane that thickness is 90-115 μ m.

Described softening agent is glycerine or sorbyl alcohol.

Beneficial effect of the present invention: the present invention is with inorganic nano-particle TiO ₂Be incorporated in the organic phase, improved composite property.Compare with existing edible film, composite membrane of the present invention has uvioresistant effect preferably, compare with pure lactalbumin membrane, composite membrane of the present invention removes can effectively reduce the food spoilage that uviolizing causes, thereby prolong outside the shelf-lives of food, also have stronger physical strength, and water vapor transmission rate (WVTR) reduces.

Description of drawings

Fig. 1 is WPI film and WPI/TiO ₂The transmittance change curve of composite membrane;

Fig. 2 is WPI film and WPI/TiO ₂Composite membrane at 200-280nm transmittance change curve;

Fig. 3 is WPI and WPI/TiO ₂The pictorial diagram of composite membrane.

(a) WPI film; (b) WPI/TiO ₂Composite membrane (TiO ₂With the weight ratio of WPI be 2: 100)

Embodiment

Below stop that about film thickness, tensile property, steam permeable coefficient (WVP), transmittance and ultraviolet ray the measuring method of situation is as follows among the preparation embodiment:

(1) composite membrane Determination of thickness method: use digimatic micrometer to measure the thickness of film.

(2) measuring method of tensile strength

With reference to ASTM (1995) method, use TMS-Pro matter structure instrument to measure tensile property, wherein draw speed is 1mm/s.Tensile strength (TS, N/mm ²) calculate by formula (1):

$\mathrm{TS}=\frac{F_t}{L\×W}---\left(1\right)$

In the formula (1), F _t---maximum pull (N);

The thickness of L---membrane sample (mm);

The width of W---membrane sample (mm);

(3) measuring method of steam permeable coefficient (WVP)

With reference to GB 1037-88 method, adopt plan cup method to measure.The water vapour transmission coefficient calculates by formula (2):

$\mathrm{WVP}(g\·\mathrm{mm}/m^2\·h\·\mathrm{kPa})=\frac{W\×x}{A\×T\×\mathrm{\ΔP}}---\left(2\right)$

In the formula (2), the weightening finish of W---moisture vapor transmission cup (g);

The thickness of x---film (mm);

A---film exposed area (cm ²);

T---interval time of measurement (h);

The water vapour pressure reduction (kPa) of Δ P---film both sides;

(4) mensuration of transmittance and ultraviolet ray transmissivity: adopt ultraviolet visible spectrophotometry to measure the transmittance of film at 200-800nm wavelength place.

Embodiment 1

(1) is that 10% the whey isolate protein aqueous solution continues to stir 2h on magnetic stirring apparatus with mass percent concentration, it is fully dissolved, regulate pH to 8;

(2) step (1) gained solution is heated 30min in 70 ℃ of water-baths, to be cooled to room temperature, add glycerine, wherein, the weight ratio of glycerine and whey isolate protein is 0.5: 1;

(3) in step (2) gained solution, add nano-TiO again ₂, be stirred well to nano-TiO ₂Disperse the back ultrasonic degas fully, obtain film forming liquid, wherein, nano-TiO ₂See table 1 for details with the weight ratio of whey-protein;

(4) accurately take by weighing the above-mentioned film forming liquid of 5g and join in the synthetic glass ware of diameter 8cm, place climatic chamber, at 22 ± 2 ℃, relative humidity is that balance 4h makes composite membrane of the present invention under 56 ± 2% the condition.

WPI film in contrast, its preparation method are with the preparation method of composite membrane of the present invention, and only step (3) difference does not promptly add nano-TiO in the solution of step (2) ₂, and, obtain film forming liquid directly with the solution ultrasonic degas.

Table 1 nano-TiO ₂With the weight ratio of whey isolate protein and the parameter of corresponding membrane thereof

Annotate: alphabetical a and b represent work property variance analysis result, and different letter representatives have significant difference (P≤0.05), and same letter is represented there was no significant difference.

By table 1 as seen, the thickness and the WPI film of the prepared composite membrane of the present invention are basic identical.

The tensile strength of composite membrane of the present invention is compared with the WPI film, strengthens to some extent.

TiO in composite membrane ₂: the weight ratio of WPI was compared with the WPI film more than or equal to 1: 100 o'clock, and the water vapor transmission of composite membrane obviously reduces, and promptly composite membrane obviously improves the blocking capability of water vapour.

From table 1, Fig. 1 and Fig. 2 as can be seen, in the 200-800nm scope, the transmittance of WPI film is the highest, along with TiO ₂The increase of addition and reducing gradually, the transmittance of film obviously reduces, and the transparency of film reduces, and nano-TiO is described ₂WPI in dispersion reduced the transparency of composite membrane.Simultaneously, in the 200-400nm ultraviolet range, along with TiO in the WPI composite membrane ₂The increase of addition obviously strengthens ultraviolet barrier effect.In ultraviolet wavelength 200-280nm scope, TiO ₂Concentration was more than or equal to 1% o'clock, and the WPI composite membrane stops ultraviolet ray fully.The result shows, WPI/TiO ₂Composite membrane has good barrier effect to ultraviolet ray.The transmittance that also can see composite membrane of the present invention from Fig. 3 is starkly lower than the WPI film.

Embodiment 2

(1) is that 7% the whey isolate protein aqueous solution continues to stir 2h on magnetic stirring apparatus with mass percent concentration, it is fully dissolved, regulate pH to 7;

(2) step (1) gained solution is heated 30min in 80 ℃ of water-baths, to be cooled to room temperature, add glycerine, wherein, the weight ratio of glycerine and whey isolate protein is 0.4: 1;

(3) in step (2) gained solution, add nano-TiO again ₂, be stirred well to nano-TiO ₂Disperse the back ultrasonic degas fully, obtain film forming liquid, wherein, nano-TiO ₂With the weight ratio of whey-protein 1: 100;

(4) accurately take by weighing the above-mentioned film forming liquid of 5g and join in the synthetic glass ware of diameter 8cm, place climatic chamber, at 22 ± 2 ℃, relative humidity is that balance 48h makes composite membrane of the present invention under 56 ± 2% the condition.

WPI film in contrast, its preparation method are with the preparation method of above-mentioned composite membrane, and only step (3) difference does not promptly add nano-TiO in the solution of step (2) ₂, and, obtain film forming liquid directly with the solution ultrasonic degas.

The composite membrane thickness that utilizes aforesaid method to obtain is 90-115 μ m, and tensile strength is 5.83 ± 0.54N/mm ², water vapor transmission rate (WVTR) is 1.23 ± 0.02gmm/hm ²KPa absorbs ultraviolet ray in ultraviolet wavelength 200-280nm scope fully.And the tensile strength of WPI film is 4.34 ± 0.26N/mm ², water vapor transmission rate (WVTR) is 1.46 ± 0.01gmm/hm ²KPa.Both compare, and the tensile strength of composite membrane increases, and water vapor transmission rate (WVTR) obviously reduces, and the ability of shielding of ultraviolet obviously strengthens.

Embodiment 3

(1) is that 12% the whey isolate protein aqueous solution continues to stir 2h on magnetic stirring apparatus with mass percent concentration, it is fully dissolved, regulate pH to 9;

(2) step (1) gained solution is heated 30min in 90 ℃ of water-baths, to be cooled to room temperature, add glycerine, wherein, the weight ratio of glycerine and whey isolate protein is 0.6: 1;

(3) in step (2) gained solution, add nano-TiO again ₂, be stirred well to nano-TiO ₂Disperse the back ultrasonic degas fully, obtain film forming liquid, wherein, nano-TiO ₂With the weight ratio of whey-protein 1: 100;

(4) accurately take by weighing the above-mentioned film forming liquid of 5g and join in the synthetic glass ware of diameter 8cm, place climatic chamber, at 22 ± 2 ℃, relative humidity is that balance 48h makes composite membrane of the present invention under 56 ± 2% the condition.

WPI film in contrast, its preparation method are with the preparation method of above-mentioned composite membrane, and only step (3) difference does not promptly add nano-TiO in the solution of step (2) ₂, and, obtain film forming liquid directly with the solution ultrasonic degas.

The composite membrane thickness that utilizes aforesaid method to obtain is 90-115 μ m, and tensile strength is 9.48 ± 0.85N/mm ², water vapor transmission rate (WVTR) is 1.01 ± 0.01gmm/hm ²KPa in ultraviolet wavelength 200-280nm scope, stops ultraviolet ray fully.And the tensile strength of WPI film is 7.29 ± 0.72N/mm ², water vapor transmission rate (WVTR) is 1.18 ± 0.03gmm/hm ²KPa.Both compare, and the tensile strength of composite membrane increases, and water vapor transmission rate (WVTR) obviously reduces, and the ability of shielding of ultraviolet obviously strengthens.

Claims (5)

1. whey-protein/TiO ₂Edible composite membrane is characterized in that, described composite membrane is with lactoalbumin soln and nano-TiO under the situation of adding softening agent ₂Mix and make, wherein, nano-TiO ₂With the weight ratio of whey-protein be (0.1-2): 100.

2. whey-protein/TiO according to claim 1 ₂Edible composite membrane is characterized in that, the mass percent concentration of described lactoalbumin soln is 7-12%.

3. whey-protein/TiO according to claim 1 and 2 ₂Edible composite membrane is characterized in that, described whey-protein is a whey isolate protein.

4. described whey-protein/TiO of claim 1 ₂The preparation method of edible composite membrane is characterized in that, comprises following operation steps:

(1) be that the lactoalbumin soln of 7-12% continues to stir on magnetic stirring apparatus with mass percent concentration, treat that it fully dissolves after, regulate pH to 7-9;

(2) step (1) gained solution is heated 20-40min in 70-90 ℃ of water-bath, to be cooled to room temperature, add softening agent, wherein, the weight ratio of softening agent and whey-protein is (0.4-0.6): 1;

(3) in step (2) gained solution, add nano-TiO again ₂, be stirred well to nano-TiO ₂Disperse the back ultrasonic degas fully, obtain film forming liquid, wherein, nano-TiO ₂With the weight ratio of whey-protein be (0.1-2): 100;

(4) above-mentioned film forming liquid is joined in the flat synthetic glass vessel, wherein, the consumption of film forming liquid is 0.09-0.1g/cm ², at 20-24 ℃, relative humidity is balance 48h at least under the condition of 54-58%, makes the composite membrane that thickness is 90-115 μ m.

5. whey-protein/TiO according to claim 4 ₂The preparation method of edible composite membrane is characterized in that, described softening agent is glycerine or sorbyl alcohol.

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