PLANT PROTEIN-STARCH FILMS

Abstract

The present invention relates to a film comprising greater than or equal to 50 wt % of a combination of a plant protein and starch based upon the total weight of the film at 55% relative humidity and 22 C., wherein the weight ratio of starch to plant protein is in the range 0.5:1 to 30:1, and wherein the plant protein has been pre-treated with an organic acid.

Claims

1. A film, preferably an edible film, comprising greater than or equal to 50 wt % of a combination of a plant protein and starch, based upon the total weight of the film at 55% relative humidity and 22 C., wherein the weight ratio of starch to plant protein is in the range 0.5:1 to 30:1, and wherein the plant protein has been pre-treated with an organic acid.

2. A film as claimed in claim 1, comprising: a first layer comprising starch; and a second layer comprising a plant protein, wherein the plant protein has been pre-treated with an organic acid; wherein the second layer is in contact with a first surface of the first layer.

3. A film according to claim 2, wherein the first layer further comprises a plant protein, wherein the plant protein has been pre-treated with an organic acid.

4. A film according to claim 2 or claim 3, wherein the second layer further comprises starch.

5. A film as claimed in any one of claims 1 to 4, wherein the weight ratio of starch to plant protein is in the range 2:1 to 27.5:1, more preferably 3.5:1 to 25:1, even more preferably 7:1 to 25:1.

6. A film as claimed in any one of claims 1 to 4, wherein the weight ratio of starch to plant protein is in the range 1:2 to 3:1, more preferably 1:1 to 2:1.

7. A film as claimed in any one of claims 1 to 6, wherein the plant protein is selected from soybean protein, pea protein, rice protein, potato protein, rapeseed protein, sunflower protein, preferably selected from pea protein, potato protein, rapeseed protein, sunflower protein and/or rice protein, preferably wherein the plant protein is pea protein.

8. A film as claimed in any one of claims 1 to 7, comprising 2.0 to 40 wt % plant protein based upon the total weight of the film at 55% relative humidity and 22 C.

9. A film as claimed in any one of claims 1 to 8, wherein the starch is selected from wheat starch, potato starch, pea starch, waxy potato starch, maize starch, waxy maize starch, high amylose maize starch, tapioca starch, cassava starch, rye starch, sorghum starch, chickpea starch, soy starch, a modified starch, or a mixture thereof, preferably wherein the starch is potato starch.

10. A film as claimed in any one of claims 1 to 9, comprising 30 to 70 wt % starch based upon the total weight of the film at 55% relative humidity and 22 C.

11. A film as claimed in any one of claims 1 to 10, comprising 8 to 20 wt % water based upon the total weight of the film at 55% relative humidity and 22 C.

12. A film as claimed any one of claims 1 to 11, further comprising a plasticiser, preferably wherein the plasticiser is selected from glycerol, polyethylene glycol, propylene glycol, sorbitol, mannitol, xylitol, triethyl citrate, fatty acids, glucose, mannose, fructose, sucrose, urea, lecithin, waxes, amino acids and organic acids, or a mixture thereof, more preferably wherein the plasticiser is glycerol.

13. A film as claimed in claim 12, comprising 5 to 30 wt % plasticiser based upon the total weight of the film at 55% relative humidity and 22 C.

14. A film as claimed in any one of claims 1 to 13, further comprising a pigment or dye, preferably wherein the pigment or dye is a food colourant, preferably a food colourant derived from plant sources, more preferably a food colourant selected from carotenoids, chlorophyllins, anthocyanins and betanin.

15. A film as claimed in any one of claims 1 to 14, further comprising a structural reinforcement agent, preferably wherein the structural reinforcement agent is selected from cellulosic materials, including microcrystalline cellulose, micro-fibrillated celluloses included cellulose fibres extracted from the pulp of citrus fruits, microfibrous cellulose from fermentation, starch microcrystals, clays or a mixture thereof, preferably micro-fibrillated cellulose from citrus pulp.

16. A film as claimed in claim 15, comprising 0.5 to 5 wt % of said structural reinforcement agent based upon the total weight of the film at 55% relative humidity and 22 C.

17. A film as claimed in any one of claims 1 to 16, further comprising a hydrophobic agent, preferably wherein the hydrophobic agent is a plant-based oil or a plant-based fatty acid.

18. A film as claimed in claim 17, comprising 0.3 to 2.5 wt % of a hydrophobic agent based upon the total weight of the film at 55% relative humidity and 22 C.

19. A film as claimed in any one of claims 1 to 18, wherein the organic acid used in the pre-treatment is selected from acetic acid, an -hydroxy acid, and a -hydroxy acid.

20. A film as claimed in any one of claims 2 to 19, wherein the plant protein in the second layer has a protein secondary structure with at least 40% intermolecular -sheet, at least 50% intermolecular -sheet, at least 60% intermolecular -sheet, at least 70% intermolecular -sheet, at least 80% intermolecular -sheet, or at least 90% intermolecular -sheet.

21. A process for preparing a film as claimed in claim 1, comprising the steps of: (i) mixing the starch in water, optionally with sonication, to form a starch mixture; (ii) dissolving the plant protein in water and an organic acid, optionally with sonication, to form a protein solution; (iii) mixing the starch mixture and the protein solution to form a film-forming composition; and (iv) forming the film-forming composition into a film.

22. A process for preparing a film as claimed in claim 2, comprising the steps of: (i) mixing the starch in water, optionally with sonication, to form a starch mixture; (ii) forming the starch mixture into a first layer on a surface; (iii) dissolving the plant protein in water and an organic acid, optionally with sonication, to form a protein solution; and (iv) forming the protein solution into a second layer on a first surface of the first layer.

23. A product, preferably a foodstuff, coated with or enclosed by a film according to any one of claims 1 to 20.

24. A product as claimed in claim 23, which is a stock cube.

25. A product as claimed in claim 23, which is a powdered food.

26. A method of coating or enclosing a product, preferably a foodstuff, comprising the steps of: (i) wrapping the product in a film as claimed in any one of claims 1 to 20; and (ii) sealing the film around the product.

27. Use of a film according to any one of claims 1 to 20 to coat or enclose a product, preferably a foodstuff.

28. A method of releasing a product coated or enclosed with a film as claimed in any one of claims 1 to 20, comprising the steps of: (i) placing the coated or enclosed product in water; and (ii) allowing the film to disperse, thereby releasing the product.

29. A method as claimed in claim 28, wherein the product is released during a cooking process or a washing process.

30. A film-forming composition, preferably an edible film-forming composition, wherein the weight ratio of starch to plant protein is in the range 0.5:1 to 30:1, and wherein the plant protein has been pre-treated with an organic acid.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0158] FIG. 1a is a graphical representation of a monolayer film of the present invention and FIG. 1b is a graphical representation of a multilayer film of the present invention.

[0159] FIG. 2 is a photograph of some of the films of Example 1 laid over printed text, which gives an indication of the transparency of the films.

[0160] FIGS. 3a, 3b and 3c are photographs of products wrapped and sealed in film E4 of Example 1. FIG. 3a shows a stock cube, FIG. 3b shows a bar soap and FIG. 3c shows a dishwasher tablet.

EXAMPLES

Materials

[0161] Pea Protein Isolate (PPI) (80 wt % protein, 4 wt % carbohydrate) (ProEarth P16109) was purchased from Cambridge Commodities Ltd.

[0162] Lactic acid (food-grade, >80%) was purchased from Cambridge Commodities Ltd.

[0163] Acetic acid (glacial, food grade) was purchased from Fisher Scientific.

[0164] Soluble Potato Starch was purchased from APC, East Tame Business Park, Cheshire SK14 4GX, UK.

[0165] Vegetable (rapeseed) oil was purchased from Tesco Ltd, UK.

[0166] Food-grade Glycerol (APC Pure) was purchased from APC East Tame Business Park, Cheshire SK14 4GX, UK.

Measurement Methods

Dispersion Test in Water

[0167] A 0.2 g piece of film was placed in 600 mls of boiling water for 3 minutes with an overhead stirrer at 750 rpm positioned off-centre so that it does not touch the film. Observations were made as to the presence or absence of fragments in the water. After this time, the mixture was passed through a 2 mm mesh sieve. The appearance of the residue collected on the sieve, if any, was observed and noted. The fragments of film were carefully removed from the mesh using tweezers and the mass was measured.

Film Tensile Strength and/or % Elongation Test

[0168] Films were tested according to ASTM D882-18 Tensile Properties of Thin Plastic Sheeting using a Tinius Olsen 5ST tensile tester with a 100N load cell.

[0169] The films to be tested were cut into strips of 8.0 cm by 1.0 cm. The film thicknesses were measured by a micrometer (DML 3701P6 from RDM Test Equipment) at six points (three on each side of the strip being tested) and the results averaged to determine the average cross-sectional thickness. The strips were then conditioned to 76% relative humidity (RH) at 5 C. by leaving the films exposed within a humidity chamber at 76% RH/5 C. for at least 24 hours before testing to ensure they had reached equilibrium. Conditions were measured using commonly available devices such as the Fisherbrand Traceable Thermometer/Clock/Humidity Monitor. Such conditions are typical for a domestic fridge.

[0170] Alternatively, the strips were conditioned to 55% relative humidity at 22 C. using the same method. Such conditions are typical of the humidity encountered in a room temperature packing and storage facility.

[0171] In order to test a film, the strip was removed from the humidity chamber and fixed by the parallel clamps of the 5ST test head with a 5 cm gap between the clamps. The upper clamp attached to the load cell was then moved upwards at a constant speed of 50 mm/minute to stretch the film until failure and the force exerted on the load cell recorded. This procedure happened within 1 minute of the film sample being withdrawn from the humidity chamber to minimise any changes in the condition of the film. The tensile strength is the force at failure divided by the average cross-sectional area of the film before conditioning and testing. The % Break Strain is calculated as (length of the film at failure-length of the initial film)/length of the initial film)100.

Transparency Test

[0172] A 0.09 mm0.01 mm thick strip of film was placed over printed text and the transparency of the film noted.

Example 1: Preparation of Films

[0173] Monolayer films (E1-E3 and E5) and multilayer films (E4, E6-E11) were prepared according to the procedures described below. Five comparative monolayer films (C1-C5) were also prepared according to the procedures described below.

Preparation of Starch-Only Monolayer Film C1

(i) Preparation of Starch Mixture

[0174] 22.50 g of Soluble Potato Starch was dispersed in 150 g of ambient temperature, deionised water in a 250 ml flask by stirring. 5.625 g of glycerol and 0.23 g of vegetable oil were then added and the suspension stirred. The suspension was then sonicated (high intensity ultrasound) using a Bandelin Sonopuls HD4200 with a TS113 probe for 14 minutes and 15 seconds. The sonicator was set to an amplitude of 95%, with a cycle of 1 second on and 0.2 seconds off. The suspension was stirred throughout the sonication to ensure homogeneity. After the sonication, 0.54 g of lactic acid was added with stirring. There was no additional heating but the energy of the sonication raised the temperature of the mix to over 80 C. by the end of the sonication period. The mix was then placed in a heated ultrasound water bath for 30 minutes at 80 C. to allow the escape of trapped air bubbles.

(ii) Film Formation

[0175] 25 ml of the mix produced in step (i) was poured through a tea strainer to remove any remaining large lumps and into a 50 ml Falcon tube. The mix was then further degassed by removing large bubbles with a pipette and placing the Falcon tube in the ultrasound bath at 80 C. for 5 minutes. The mix was removed, allowed to cool to 55 C. and poured onto a flat glass plate with a Mylar surface. The liquid was spread out uniformly over the plate using an RK K control coater model 101 with a knife edge to give a film of uniform thickness of 1000 microns. The glass plate was then placed in an oven at 80 C. for 1 hr. After this time, the film could be peeled off the Mylar surface ready for testing

Preparation of Pea Protein Isolate (PPI) Monolayer Film C4

(i) Preparation of PPI Mixture

[0176] 30 g of water was mixed with 7.5 g Pea Protein Isolate in a tall 250 ml beaker using an overhead stirrer to form a homogenous paste. 70 ml of acetic acid was then added with stirring along with 1.876 g of glycerol. The suspension was then sonicated (high intensity ultrasound) using a Bandelin Sonopuls HD4200 with a TS113 probe for 7 minutes and 30 seconds. The sonicator was set to an amplitude of 50%, with a cycle of 1 second on and 0.2 seconds off. The suspension was stirred intermittently throughout the sonication to ensure homogeneity.

(ii) Film Formation

[0177] 25 mL of the mix produced in step (i) was then cast into a film following the procedure described in step (ii) of the preparation of film C1.

Preparation of Protein-Starch Monolayer Film E1

(i) Preparation of Starch Mixture

[0178] 21.38 g of Soluble Potato Starch was dispersed in 142.5 g of ambient temperature, deionised water in a 250 ml flask by stirring. 5.625 g of glycerol and 0.23 g of vegetable oil were then added and the suspension stirred. The suspension was then sonicated (high intensity ultrasound) according to the procedure described in step (i) of the preparation of film C1.

(ii) Preparation of PPI Mixture

[0179] 30 g of water was mixed with 7.5 g of Pea Protein Isolate (PPI) in a tall 250 ml beaker using an overhead stirrer to form a homogenous paste. 70 ml of acetic acid was then added with stirring. The mix was then sonicated and processed according to the procedure described in step (i) of the preparation of film C4.

(iii) Preparation of a Protein-Starch Mixture

[0180] 15 ml of the PPI mix from step (ii) and 0.54 g lactic acid were added to the total starch mix produced in step (i). The combined mix was sonicated for 1 minute using a Sonopuls HD4200, at an amplitude of 50%, with a cycle of 1 second on, 0.2 seconds off. The combined mix was then placed in an ultrasonic bath at 80 C. for 5 minutes to help remove air bubbles.

(iv) Film Formation

[0181] 25 mL of the mix produced in step (iii) was then cast into a film according to the procedure described in step (ii) of the preparation of film C1.

Preparation of Protein-Starch Monolayer Film C2

(i) Preparation of Starch Mixture

[0182] A starch mix was prepared according to the procedure described in step (i) of the preparation of film E1.

(ii) Preparation of PPI Mixture

[0183] A PPI mix was prepared according to the procedure described in step (ii) of the preparation of film E1.

(iii) Preparation of Protein-Starch Mixture

[0184] 7.5 ml of the PPI mix from step (ii) and 0.54 g lactic acid were then added to the total starch mix from step (i). The combined mix was then sonicated and prepared according to the procedure described in step (iii) of the preparation of film E1.

(iv) Film Formation

[0185] 25 mL of the mix produced in step (iii) was then cast into a film according to the procedure described in step (ii) of the preparation of film C1.

Preparation of Protein-Starch Monolayer Film C3 (without Organic Acid Treatment Step)

(i) Preparation of Starch Mixture

[0186] A starch mix was prepared according to the procedure described in step (i) of the preparation of film E1.

(ii) Preparation of PPI Mix

[0187] 7.5 g of Pea Protein Isolate (PPI) was added to 100 g of water in a tall 250 ml beaker using an overhead stirrer to form a homogenous paste. The PPI mix was then sonicated according to the procedure described in step (i) of the preparation of film C4.

(iii) Preparation of Protein-Starch Mixture

[0188] 15 ml of the PPI mix from step (ii) and 0.54 g lactic acid were added to the starch mix from step (i). The combined mix was sonicated for 1 minute using a Sonopuls HD4200, at an amplitude of 50%, with a cycle of 1 second on, 0.2 seconds off. The combined mix was then placed in an ultrasonic bath at 80 C. for 5 minutes to help remove air bubbles.

(iv) Film Formation

[0189] 25 mL of the combined mix produced in step (iii) was then cast into a film according to the procedure described step (ii) of the preparation of film C1.

Preparation of Protein-Starch Monolayer Film E5

(i) Preparation of Starch Mixture

[0190] A starch mix was prepared according to the procedure in step (i) of the preparation of film C1.

(ii) Preparation of PPI Mixture

[0191] A PPI mixture was prepared according to the procedure described in step (i) of the preparation of film C4.

(iii) Preparation of Protein-Starch Mixture

[0192] 150 ml of the PPI mix from step (ii) and 0.54 g lactic acid were added to the total starch mix from step (i) to form a combined mix. The combined mix was sonicated for 3 minutes using a Bandelin Sonopuls HD4200, at an amplitude of 50% with a cycle of 1 second on, 0.2 seconds off. The combined mix was then placed in an ultrasonic bath at 80 C. for 5 minutes to help remove air bubbles.

(iv) Film Formation

[0193] 25 mL of the combined mix from step (iii) was then cast into a film according to the procedure described in step (ii) of the preparation of film C1.

Preparation of Protein-Starch Monolayer Film E2

(i) Preparation of Starch Mixture

[0194] A starch mix was prepared according to the procedure described in step (i) of the preparation of film C1, except that 19.13 g of starch and 127.50 g of water were used.

(i) Preparation of PPI Mixture

[0195] A PPI mix was prepared according to the procedure described in step (ii) of the preparation of film E1.

(iii) Preparation of Protein-Starch Mixture

[0196] 45 ml of the PPI mix from step (ii) and 0.54 g lactic acid were added to the starch mix from step (i). The combined mix was sonicated for 3 minutes using a Sonoplus 4000, at an amplitude of 50% with a cycle of 1 second on, 0.2 seconds off. The combined mix was then placed in an ultrasonic bath at 80 C. for 5 minutes to help remove air bubbles.

(iv) Film Formation

[0197] 25 mL of the combined mix from step (iii) was then cast into a film according to the procedure described in step (ii) of the preparation of film C1.

Preparation of Protein-Starch Monolayer Film E3

(i) Preparation of Starch Mixture

[0198] A starch mix was prepared according to the procedure described in step (i) of the preparation of film C1, except that 16.88 g of starch and 112.5 g of water were used.

(ii) Preparation of PPI Mixture

[0199] A PPI mix was prepared according to the procedure described in step (ii) of the preparation of film E1.

(iii) Preparation of Protein-Starch Mixture

[0200] 75 ml of the PPI mix from step (ii) and 0.54 g lactic acid were added to the starch mix from step (i). The combined mix was sonicated for 3 minutes using a Bandelin Sonopuls HD4200, at an amplitude of 50% with a cycle of 1 second on, 0.2 seconds off. The combined mix was then placed in an ultrasonic bath at 80 C. for 5 minutes to help remove air bubbles.

(iv) Film Formation

[0201] 25 mL of the combined mix from step (iii) was then cast into a film according to the procedure described in step (ii) of the preparation of film C1.

Preparation of Protein-Starch Multilayer Film E4

(i) Preparation of Starch Mixture

[0202] A starch mix was prepared according to step (i) of the preparation of film E1.

(ii) Preparation of PPI Mixture

[0203] A PPI mix was prepared according to step (ii) of the preparation of film E1.

(iii) Preparation of Protein-Starch Mixture

[0204] A combined PPI and starch mix was prepared according to step (iii) of the preparation of film E1.

(iv) Film FormationFirst Layer

[0205] 25 mL of the combined mix from step (iii) was cast into a film according to step (ii) of the preparation of film C1, except that a wet film thickness of 900 microns was applied to Mylar surface of the glass plate. The film was left to dry at 80 C. for 60 minutes.

(v) Film FormationSecond Layer

[0206] Whilst the film of step (iv) was drying, 1.594 g glycerol and 0.064 g of vegetable oil were added to the remaining 85 ml of the PPI mix from step (ii). The mix was sonicated using a Bandelin Sonopuls HD4200 for 2 minutes at 50% amplitude, with a cycle of 1 second on, 0.2 seconds off. The mix was then degassed and cooled to 55 C.

[0207] 7 ml of the mixture was then spread over the exposed surface (i.e. the surface not in contact with the glass plate) of the dried film prepared in step (iv) using an RK K control coater model 101 with a Tan K-bar of wire diameter 1.52 mm to give a wet film of the PPI mix of approximately 120 microns thickness. The plate was then put back in the oven for 15 minutes at 80 C. to form the multilayer film E4.

Preparation of Protein-Starch Monolayer Film C5 (without Organic Acid Treatment Step)

(i) Preparation of Starch Mixture

[0208] 11.25 g of Soluble Potato Starch was dispersed in 75 g of ambient temperature, deionised water in a 250 ml flask by stirring. 5.625 g of glycerol and 0.23 g of vegetable oil were then added and the suspension stirred. The suspension was then sonicated (high intensity ultrasound) using a Bandelin Sonopuls HD4200 with a TS113 probe for 7 minutes and 30 seconds. The sonicator was set to an amplitude of 95% amplitude, with a cycle of 1 second on and 0.2 seconds off. The suspension was stirred throughout the sonication to ensure homogeneity. There was no additional heating but the energy of the sonication raised the temperature of the mix to over 80 C. by the end of the sonication period. The mix was then placed in a heated ultrasound water bath for 30 minutes at 80 C. to allow the escape of trapped air bubbles.

(ii) Preparation of PPI Mixture

[0209] 7.5 g of Pea Protein Isolate (PPI) was added to 100 g of water in a tall 250 ml beaker using an overhead stirrer to form a homogenous paste. The PPI mix was then sonicated according to the procedure described in step (i) of the preparation of film C4.

(iii) Preparation of Protein-Starch Mixture

[0210] 150 ml of the PPI mix from step (ii) and 0.54 g lactic acid were added to the starch mix from step (i). The combined mix was sonicated for 3 minutes using a Bandelin Sonopuls HD4200, at an amplitude of 50% with a cycle of 1 second on, 0.2 seconds off. The combined mix was then placed in an ultrasonic bath at 80 C. for 5 minutes to help remove air bubbles.

(iv) Film Formation

[0211] 25 mL of the combined mix from step (iii) was then cast into a film according to the procedure described in step (ii) of the preparation of film C1.

Preparation of Protein-Starch Multilayer Film E6

(i) Preparation of Starch Mixture

[0212] 75 g of Soluble Potato Starch was added to 500 g of ambient temperature, deionised water in a Klarstein food processor (Grand Prix Chef Edition). 21.77 g of glycerol was then added whilst starting the program: Temperature 85 C., Speed 4, 45 mins. After 45 min the solution was taken out of the food processor and poured into a suitable container and degassed using a FlackTek Speedmixer from Synergy with the following parameters: 3 min, 2000 rpm, 50 mBars.

(ii) Preparation of PPI Mixture

[0213] 60 g of water was mixed with 15 g of Pea Protein Isolate (PPI) and 3.75 g of glycerol. in a tall 250 ml beaker using an overhead stirrer to form a homogenous paste. 140 ml of acetic acid was then added with stirring. The mix was then sonicated (high intensity ultrasound) using a Bandelin Sonopuls HD4200 with a TS113 probe for 15 minutes. The sonicator was set to an amplitude of 50%, with a cycle of 1 second on and 0.2 seconds off. The suspension was stirred intermittently throughout the sonication to ensure homogeneity. Once sonicated, the slurry was poured into a suitable container and degassed using a FlackTek Speedmixer from Synergy using the following parameters: 2 min, 2000 rpm, 999 mBar.

(iii) Film Formation 1.sup.st Layer

[0214] The starch mixture from (i) was poured onto a flat glass plate with a Mylar surface. The liquid was spread out uniformly over the plate using an RK K303S Multicoater with a knife edge to give a film of uniform thickness of 500 microns. The glass plate was then placed in an oven at 80 C. for 1 hr. After this time, the film could be peeled off the Mylar surface ready for testing.

(iv) Film Formation 2.SUP.nd .Layer

[0215] 7 ml of the mixture (ii) was then spread over the exposed surface (i.e. the surface not in contact with the glass plate) of the dried film prepared in step (iv) using an RK K303S Multicoater with a Black K-bar of wire diameter 0.51 mm to give a wet film of the PPI mix of approximately 40 microns thickness. The plate was then put back in the oven for 15 minutes at 80 C. to form the multilayer film E6.

Preparation of Protein-Starch Multilayer Film E7

(i) Preparation of Starch Mixture

[0216] 128.25 g of Soluble Potato Starch was added to 855 g of ambient temperature, deionised water in a Klarstein food processor (Grand Prix Chef Edition). 39.1 g of glycerol and 1.36 g of vegetable oil was then added whilst starting the program: Temperature 85 C., Speed 4, 45 mins.

(ii) Preparation of PPI Mixture

[0217] 30 g of water was mixed with 7.5 g of Pea Protein Isolate (PPI) in a tall 250 ml beaker using an overhead stirrer to form a homogenous paste. 70 ml of acetic acid was then added with stirring. The mix was then sonicated (high intensity ultrasound) using a Bandelin Sonopuls HD4200 with a TS113 probe for 7 minutes and 30 seconds. The sonicator was set to an amplitude of 50%, with a cycle of 1 second on and 0.2 seconds off. The suspension was stirred intermittently throughout the sonication to ensure homogeneity.

(iii) Preparation of Protein-Starch Mixture

[0218] 90 ml of the PPI mix from step (ii) and 1.60 g lactic acid were added to the total starch mix produced in step (i). The combined mix was stirred for a further 5 minutes. After a total of 50 mins, the combined mix was taken out of the food processor and poured into a suitable container and degassed using a Flacktek Speedmixer from Synergy with the following parameters: 3 min, 2000 rpm; 50 mBars.

(iv) Film FormationFirst Layer

[0219] Once degassed the mix from step (iii) was poured onto a flat glass plate with a Mylar surface. The liquid was spread out uniformly over the plate using an RK K303S Multicoater with a knife edge to give a film of uniform thickness of 900 microns. The glass plate was then placed in an oven at 80 C. for 1 hr.

(v) Film FormationSecond Layer

[0220] Whilst the film of step (iv) was drying, 37.5 g of water was mixed with 9.38 g of Pea Protein Isolate (PPI) and 2.72 g of glycerol in a tall 250 ml beaker using an overhead stirrer to form a homogenous paste. 88 ml of acetic acid was then added with stirring. The mix was then sonicated (high intensity ultrasound) using a Bandelin Sonopuls HD4200 with a TS113 probe for 9 minutes and 22 seconds. The sonicator was set to an amplitude of 50%, with a cycle of 1 second on and 0.2 seconds off. The suspension was stirred intermittently throughout the sonication to ensure homogeneity.

[0221] 7-15 ml of the mixture was then spread over the exposed surface (i.e. the surface not in contact with the glass plate) of the dried film prepared in step (iv) using an RK K303S Multicoater with a Brown K-bar of wire diameter 1.02 mm to give a wet film of the PPI mix of approximately 80 microns thickness. The plate was then put back in the oven for 15 minutes at 80 C. to form the multilayer film E7.

Preparation of Starch-Protein Multilayer Film E8

(i) Preparation of Starch Mixture

[0222] 500 ml of deionised water was mixed with 50 g of potato starch in a 600 ml beaker at ambient temperature using an overhead stirrer. 21.43 g of glycerol was then added and the suspension stirred. The suspension was then sonicated (high intensity ultrasound) using a Bandelin Sonopuls HD4200 with a TS113 probe for 50 minutes at an amplitude of 95%, with a cycle of 1 second on, 0.2 seconds off. The suspension was stirred throughout the sonication to ensure homogeneity. The solution was then placed in a sonicator bath for 30 minutes at 80 C. to remove any bubbles.

(ii) Film FormationStarch Layer

[0223] 25 ml of the mix produced in step (i) was poured into a 50 ml Falcon tube. The mix was then further degassed by removing large bubbles with a pipette and placing the Falcon tube in the ultrasound bath at 80 C. for 5 minutes, before being removed and allowed to cool to 55 C. The liquid was poured onto a flat glass plate having a Mylar surface and was spread out uniformly over the plate using a knife blade to give a wet film thickness of 500 microns. The glass plate was then put in the oven for 60 minutes at 80 C. to form the dried film layer.

(iii) Preparation of Protein Mixture

[0224] 150 g of water was mixed with 37.5 g of Pea Protein Isolate (PPI) at ambient temperature in a 600 ml beaker using an overhead stirrer to form a homogenous paste. 350 ml of acetic acid and 10.89 g of glycerol were then added with stirring. The mix was then sonicated (high intensity ultrasound) using a Bandelin Sonopuls HD4200 with a TS113 probe for 37 minutes and 30 seconds. The sonicator was set to an amplitude of 50%, with a cycle of 1 second on and 0.2 seconds off. The suspension was stirred intermittently throughout the sonication to ensure homogeneity.

(iv) Film FormationProtein Layer

[0225] 25 ml of the mix produced in step (iii) was poured into a 50 ml Falcon tube. The mix was then degassed by removing large bubbles with a pipette, and placing the Falcon tube in the ultrasonic bath at 80 C. for 1 minute before being allowed to cool to 55 C. and then spread over the exposed surface (i.e. the surface not in contact with the glass plate) of the dried film prepared in step (ii) using a knife blade to give a wet film of the PPI mix of approximately 500 microns thickness. The plate was then put in the oven for 30 minutes at 80 C. to form the multilayer film.

Preparation of Starch-Protein Multilayer Film E9

(i) Preparation of Starch Mixture

[0226] 500 ml of deionised water was mixed with 50 g of potato starch in a 600 ml beaker at ambient temperature using an overhead stirrer. 21.43 g of glycerol was then added and the suspension stirred. The suspension was then sonicated (high intensity ultrasound) using a Bandelin Sonopuls HD4200 with a TS113 probe for 50 minutes. The sonicator was set to an amplitude of 95%, with a cycle of 1 second on and 0.2 seconds off. The suspension was stirred throughout the sonication to ensure homogeneity. There was no additional heating but the energy of the sonication raised the temperature of the mix to over 80 C. by the end of the sonication period. The mix was then placed in a heated ultrasound water bath for 30 minutes at 80 C. to allow the escape of trapped air bubbles.

(ii) Film FormationStarch Layer

[0227] 15 mL of the mix from step (i) was poured into a 50 ml Falcon tube. The mix was then further degassed by removing large bubbles with a pipette and placing the Falcon tube in the ultrasound bath at 80 C. for 5 minutes, before being removed and allowed to cool to 55 C. The liquid was poured onto a flat glass plate having a Mylar surface and was spread out uniformly over the plate using an RK K control coater model 101 with a knife blade to give a wet film thickness of 300 microns. The film was left to dry at 80 C. for 30 minutes.

(iii) Preparation of Protein Mixture

[0228] 150 ml of deionised water was mixed with 37.5 g of PPI at ambient temperature in a 600 ml beaker using an overhead stirrer to form a homogenous paste. 350 ml of acetic acid and 10.89 g of glycerol were then added with stirring. The mix was then sonicated (high intensity ultrasound) using a Bandelin Sonopuls HD4200 with a TS113 probe for 37 minutes and 30 seconds. The sonicator was set to an amplitude of 50%, with a cycle of 1 second on and 0.2 seconds off. The suspension was stirred intermittently throughout the sonication to ensure homogeneity.

(iv) Film FormationProtein Layer

[0229] 25 ml of the mix from step (iii) was poured into a 50 ml Falcon tube. The mix was then degassed by removing large bubbles with a pipette, and placing the Falcon tube in the ultrasonic bath at 80 C. for 1 minute before being allowed to cool to 55 C. and then spread over the exposed surface (i.e. the surface not in contact with the glass plate) of the dried film prepared in step (ii) using an RK K control coater model 101 with a knife blade to give a wet film of the PPI mix of approximately 500 microns thickness. The plate was then put in the oven for 30 minutes at 80 C. to form the multilayer film.

Preparation of Starch-Protein Multilayer Film E10

(i) Preparation of Starch Mixture

[0230] 2000 ml of deionised water at ambient temperature was mixed with 85.7 g of glycerol, in a Klarstein food processor (Grand Prix Chef Edition). 200 g of potato starch was then added whilst starting the program: Temperature 85 C., Speed 4, 45 mins. The batch was then moved to a VEVOR vacuum chamber connected to a hp 3 cfm single stage vacuum pump for degassing. The material was poured in the container, which was then sealed, and the vacuum pump operated for 5-10 min until the slurry was free of air bubbles.

(ii) Film FormationStarch Layer

[0231] The casting of the starch layer took place using a standard roll to roll machine including a pressure vessel, a fluid pump, a slot die unit, a feeding roller, a web traversing a series of rollers and load cells that allowed tension control, a drying oven of approximately 2 meters length and a winding roller. The backing used for this casting was a standard 72 m PET roll. The starch mixture prepared in (i) was poured into the pressure vessel and then tightly closed making sure there were no leaks. The vessel was then pressurised to 1-2 bar and the starch mixture was pumped through the progressive cavity pump to feed the slot die. The equipment was set to the following parameters: [0232] Oven temperature: 100-140 C. [0233] Line speed: 0.4-1m/min [0234] Slot die width: 300 mm [0235] Fluid pump flow: 50-120 ml/min [0236] Slot die distance from backing: 0.2-0.4 mm [0237] Shim distance between slot lips: 150-200 m
The wet thickness was varied between 300 and 550 m and was tuned to approximately 350 m by adjusting the parameters. The film came out of the oven dry and the resulting roll was then moved from the collection winder and placed as the feed roll so that a second film could be cast on top of it.
(iii) Preparation of Protein Mixture

[0238] 740 g of water was mixed with 94.4 g of Pea Protein Isolate (PPI) in a tall 1000 ml beaker using an overhead stirrer to form a homogenous slurry. 60 g of acetic acid and 23.6 g of glycerol were then added while stirring. The mix was placed in a 90 C. water bath for 20-30 min with shaking every 10 min. Following this step, the slurry was transferred to a Hielscher 1 KW sonicator (with booster) and an energy total of 200 kJ was applied with shaking every 30 min. Sonication took approximately 30 mins to reach the target energy. The process was repeated 3 times to produce a total of 2400 ml of product which was then degassed using a using a Flacktek Speedmixer from Synergy with the settings of 3-5 min, 2000 rpm; 50 mBars.

(iv) Film FormationProtein Layer

[0239] The coating equipment as described in step (ii) was used for this layer; however, the backing already had the first layer of starch coated on it. The protein mixture prepared in step (iii) was poured in the pressurized vessel and the coater was set to the following parameters: [0240] Oven temperature: 100-130 C. [0241] Line speed: 0.7-1m/min [0242] Slot die width: 300 mm [0243] Fluid pump flow: 40-120 ml/min [0244] Slot die distance from backing: 0.2-0.25 mm [0245] Shim distance between slot lips: 150-200 m
The multilayer film came out of the oven dry and showed minimal bubbles and/or imperfections. Each of the two layers had a thickness of approximately 30 m.

Preparation of Starch-Protein Multilayer Film E11

(i) Preparation of Starch Mixture

[0246] A starch mix was prepared according to the procedure described in step (i) of the preparation of film E10.

(ii) Film FormationStarch Layer

[0247] 2000 ml of the batch described in step (i) was cast into a roll of film according to the procedure described in step (ii) of the preparation of film E10.

(iii) Preparation of Protein Mixture

[0248] 1200 g of deionised water was measured and poured into a large 3 L stainless steel vessel. The vessel was placed in a water bath set at 95 C. and an overhead stirrer with an impeller blade was used to mix the water at 900 rpm. 320 g of pea protein isolate was added to the mixture and left to stir for 3 min until a homogenous mix was formed. 800 g of acetic acid was measured and poured into the mix which was stirred at 700 rpm for 40 min. The temperature of the mix was measured to ensure it had reached 85 C. and if necessary, the stirring continued to ensure that the mix had reached 85 C. for at least 10 min. Following that, the mix was sheared using a Silverson high shear homogeniser at 7000 rpm for 3 min.

[0249] The freshly shear mixed slurry was then poured into plastic flat containers or large petri dishes to an approximate height of 10 mm. The containers were then sealed and stored in a fridge for 16-28 hours.

[0250] After storage, the gel that formed was cut into 1 cm1 cm squares and using a spatula, the gel cubes were transferred in a 75 m filter bag. The bag was then suspended with the gel cubes in a bucket containing 61 of reverse osmosis water. After 1h 30 min, 31 of water were removed and replaced with 31 of fresh reverse osmosis water. The bag and gel cubes were left in the water and swirled every 20 min for 90-150 min. The pH was measured and if below 2.9 then the previous two steps were repeated until the pH reached values above 2.9.

[0251] The filter bag was then raised from the water and squeezed vigorously to remove as much excess water as possible. The slurry was then transferred to a 11 container and using an Ultra-Turrax mixer the gel mush was sheared at 15000 rpm for 15 min with shaking every 5 min. 21.71 g of glycerol was then added to the mixture followed by another 5 min of Ultra-Turrax mixing at 15000 rpm. The container was then placed in an ice bath and the mix was sonicated with a Hielschler sonicator until 0.25 kJ/ml was achieved. The slurry was filtered through a 212 m mesh and stored in plastic buckets.

(iv) Film FormationProtein Layer

[0252] 2000 ml of the mixture prepared in step (iii) was poured in the pressurised vessel of the coater described in step (iv) of film E10. The following parameters were used to set up the equipment: [0253] Oven temperature: 100-115 C. [0254] Line speed: 0.5-0.9 m/min [0255] Slot die width: 300 mm [0256] Fluid pump flow: 50-90 ml/min [0257] Slot die distance from backing: 0.15-0.2 mm [0258] Shim distance between slot lips: 150-200 m
The multilayer film came out of the oven dry and showed minimal bubbles and/or imperfections. Each of the two layers had a thickness of approximately 30 m.

[0259] The compositions of each of the prepared films are shown in Table 1.

TABLE-US-00001 TABLE 1 (misc = insoluble fibres) Starch to Protein Film No. Film type Film composition, % wt weight ratio C1 Monolayer Protein 0.0 N/A Total starch 67.4 Vegetable oil 0.7 Glycerol 16.8 Lactic acid 1.6 Acetic acid 0.0 Water 13.5 Misc 0.0 C2 Monolayer Protein 1.3 49.8:1 Total starch 65.4 Vegetable oil 0.7 Glycerol 16.6 Lactic acid 1.6 Acetic acid 0.2 Water 13.9 Misc 0.3 C3 Monolayer Protein 2.6 23.8:1 Total starch 63.7 Vegetable oil 0.7 Glycerol 16.7 Lactic acid 1.6 Acetic acid 0.0 Water 14.1 Misc 0.5 E1 Monolayer Protein 2.7 23.8:1 Total starch 64.2 Vegetable oil 0.7 Glycerol 16.9 Lactic acid 1.6 Acetic acid 0.2 Water 13.1 Misc 0.5 E2 Monolayer Protein 8.1 7.1:1 Total starch 57.9 Vegetable oil 0.7 Glycerol 16.9 Lactic acid 1.6 Acetic acid 0.5 Water 12.7 Misc 1.6 E3 Monolayer Protein 13.5 3.8:1 Total starch 51.5 Vegetable oil 0.7 Glycerol 16.9 Lactic acid 1.6 Acetic acid 0.8 Water 12.3 Misc 2.7 E4 Multilayer Protein 13.4 3.9:1 Total starch 52.0 Vegetable oil 0.7 Glycerol 17.0 Lactic acid 1.3 Acetic acid 0.8 Water 12.2 Misc 2.7 E5 Monolayer Protein 27.3 1.3:1 Total starch 35.5 Vegetable oil 0.7 Glycerol 17.0 Lactic acid 1.6 Acetic acid 1.6 Water 10.9 Misc 5.5 C4 Monolayer Protein 56.5 0.05:1 Total starch 2.8 Vegetable oil 0.0 Glycerol 17.6 Lactic acid 0.0 Acetic acid 3.3 Water 8.5 Misc 11.3 C5 Monolayer Protein 25.3 1.3:1 Total starch 32.8 Vegetable oil 0.6 Glycerol 15.8 Lactic acid 1.5 Acetic acid 0.0 Water 18.9 Misc 5.1 E6 Multilayer Protein 9.40 6:1 Total starch 56.40 Vegetable oil 0.00 Glycerol 19.20 Lactic acid 0.00 Acetic acid 0.55 Water 12.60 Misc 1.88 E7 Multilayer Protein 6.45 9.1:1 Total starch 58.70 Vegetable oil 0.62 Glycerol 19.29 Lactic acid 0.62 Acetic acid 0.38 Water 12.65 Misc 1.29 E8 Multilayer Protein 27.45 1.1:1 Total starch 30.30 Vegetable oil 0.00 Glycerol 22.36 Lactic acid 0.00 Acetic acid 1.60 Water 12.80 Misc 5.49 Protein 34.32 Total starch 23.41 Vegetable oil 0.00 E9 Multilayer Glycerol 21.75 0.68:1 Lactic acid 0.00 Acetic acid 2.00 Water 11.66 Misc 6.86 E10 Multilayer Protein 26.88 1.1:1 Total starch 30.27 Vegetable oil 0.00 Glycerol 20.80 Lactic acid 0.00 Acetic acid 0.11 Water 16.58 Misc 5.38 E11 Multilayer Protein 32.85 0.88:1 Total starch 28.93 Vegetable oil 0.00 Glycerol 22.21 Lactic acid 0.00 Acetic acid 0.06 Water 15.95 Misc 0.00

Example 2: Properties of Films

[0260] The films prepared in Example 1 were then tested to determine their physical properties. The tests methods used to determine dispersion properties, tensile strength, % break strain and transparency are detailed above in the measurement methods section and the results are shown in Tables 2a, 2b, 3 and 4 or, in the case of the transparency test, in FIG. 2.

TABLE-US-00002 TABLE 2a Tensile Strength and % Break Strain of films conditioned at 5 C. and 76% RH (Film C2 did not form a viable film that could be subjected to the tensile strength or break strain tests) Film Tensile Strength % Break No. (MPa) Strain C1 0.09 202 E1 0.17 73.8 E2 0.26 75.3 E3 0.56 47.5 E5 3.70 120 C4 2.03 23.9 E4 1.41 18.6 E6 1.20 147 E7 0.50 117 E8 1.82 34.5 E9 1.81 34.0

[0261] The results in Table 2a show that a film that contains no plant protein (C1) has a very low tensile strength combined with a very high % break strain making it very difficult to handle and process into the desired form, e.g. under industrial conditions. A film that contains almost no starch (C4) has a good tensile strength but much reduced % break strain, indicating that the film is brittle. Again, this makes the film harder to process, e.g. under industrial conditions.

[0262] The data also demonstrates that addition of plant protein (PPI) to starch (as in E1, E2, E3, E5) increases the film tensile strength and reduces the % break strain to an optimal level such that the films can be used to coat or enclose a product.

[0263] The data also demonstrates that a film prepared as a multilayer (E4) has increased tensile strength versus a film having the same starch:protein weight ratio prepared as a monolayer (E3).

[0264] The data also demonstrates that films prepared as a multilayer with higher ratios of starch to plant protein (PPI) (E6 & E7) have adequate tensile strength and % break strain.

[0265] The data also demonstrates that films prepared as multilayers with lower ratios of starch to plant protein (PPI) (E8 & E9) have good tensile strength and % break strain.

TABLE-US-00003 TABLE 2b Tensile Strength and % Break Strain of films conditioned at 22 C. and 55% RH Tensile Strength % Break Film No. (MPa) Strain E8 12.50 14.3 E9 6.40 90.6 E10 8.30 18.7 E11 8.84 29.6
The results in Table 2b demonstrate that films with a lower ratio of starch:protein and with lower level of acetic acid, such as E10 and E11, still have good tensile strength and elongation at 22 C. and 55% RH when compared to similar films with higher acetic acid, E8 and E9.

TABLE-US-00004 TABLE 3 Tensile Strength and % Break Strain of films with and without protein acid pre-treatment Tensile Tensile Strength % Break Strength % Break Film Appearance (MPa) Strain Appearance (MPa) Strain No. 5 C. 76% RH 22 C. 55% RH E1 Transparent 0.17 73.8 Transparent 2.99 114 C3 Transparent 0.16 36.6 Transparent 2.81 72.5 E5 Transparent 3.70 119.7 Transparent 3.42 129.00 C5 Translucent, N/A N/A Translucent, N/A N/A excessive excessive cracking on cracking on drying drying

[0266] Table 3 shows the effect of protein organic acid pre-treatment. For a low level of protein compared to starch, as in films E1 and C3, at both cold and room temperatures, the % break strain is higher with organic acid pre-treatment of the protein whilst the tensile strength is unchanged. This results in a film that is less brittle and easier to process as a packaging material.

[0267] The data also demonstrates that as the protein level in the film increases it becomes increasingly difficult to prepare a transparent film that does not crack upon drying, as can be seen for C5 which did not produce a viable film that could be tested. However, a film made from the same composition but with organic acid-treated protein, E5, is a transparent film with good tensile strength and % break strain, resulting in a film which is robust and can be easily handled.

TABLE-US-00005 TABLE 4 Dispersion test results Film Dispersion test - No. Dispersion test - appearance mass of residue on sieve C1 Dissolved No residue C2 Dissolved, a few small fragments No measurable residue E1 Dissolved No measurable residue E2 Dispersed - some small fragments 0.05 g residue E3 Dispersed - multiple fragments 0.15 g residue E4 Dispersed - multiple fragments 0.15 g residue C4 No dispersion/film did not break up 0.44 g residue E6 Dissolved, a few small fragments 0.09 g residue E7 Dispersed - Multiple fragments 0.22 g residue

[0268] A comparative film with no plant protein (C1) is highly soluble. A comparative film mainly containing plant protein (C4) is not soluble and does not disperse resulting in a residue of 0.44 g. The presence of low levels of protein in the monolayer film (E1, E2, E3, E4) results in a film that is either water-dissolvable or water-dispersible and leaves not greater than 0.15 g of residue behind on the sieve in a dispersion test.

[0269] Comparison of the data for films E3 and E4 demonstrate that the dispersibilty is equally good whether the film is a homogeneous monolayer film or a multilayer film.

[0270] Multilayer films with higher ratios of starch to plant protein (E6 and E7) also demonstrate good dissolution or dispersibility with a residue of less than 0.22 g, less than that of the comparative protein only film C4. The dispersion test residue for E6 is particularly low because of the low overall film thickness compared to E7.

[0271] FIG. 2 is a photograph of some of the films of Example 1 laid over printed text, which gives an indication of the transparency of the films. The images show that a film that contains no plant protein (C1) is highly transparent. As the level of protein in the film increases (E1, E2, E4, E5), the films still have a good transparency, this being a useful feature of a packaging material.

Example 3: Use of Films to Coat/Enclose a Product

Protocol for Coating/Enclosing Dishwasher Tablets and Stock Cubes:

[0272] A 9060 mm piece of film E4 was cut with a sharp knife. The two long edges were folded such that the starch layer was inside and the edges were then sealed together with a RS PRO Heat Sealer (300 mm) on Setting 2. A dishwasher or stock cube tablet was then placed inside the semi-formed flow wrap. The Tablet was then centred and the film sealed on both edges. Any excess material was cut away. FIG. 3a shows a stock cube enclosed in a sealed sachet of film E4 whilst FIG. 3c shows a dishwasher tablet enclosed in a sealed sachet of film E4.

Protocol for the Sample Making of Soap Bar Tablets:

[0273] A 15080 mm piece of film E4 was cut with a sharp knife. The two long edges were folded such that the starch layer was inside and the edges were sealed together with a RS PRO Heat Sealer (300 mm) on Setting 2. A soap bar was placed inside the semi-formed flow wrap. The tablet was then centred and the film sealed on both edges. Any excess material was cut away. FIG. 3b shows a soap bar enclosed in a sealed sachet of film E4.

[0274] The results show that the films of the present invention can be used to effectively coat/enclose a variety of products and therefore that they have a useful application as packaging materials.