Process of preparation of biodegradable films from semi refined kappa carrageenan

Abstract

The present invention relates to use of inexpensive semi-refined kappa carrageenan as a seaweed polysaccharide in preparation of tough, biodegradable films exhibiting improved performance over films obtained from refined kappa carrageenan. The formulation requires no gelling salt and the only other essential components of the film are glycerol and water, the former being used as plasticizer as reported in the prior art. The films can be recycled and reprocessed if required. The performance of the films can be further enhanced by incorporating polyvinyl alcohol that lends toughness and clarity as also natural rubber latex that imparts greater elasticity and barrier properties. Films of optimum composition can be pulse heat sealed immediately after casting and used for preparation of soft capsules and pouches. It is possible to store solvents and oils in the pouches. In view of the more eco-friendly processing of semi-refined kappa carrageenan compared to refined kappa carrageenan, films made with the former would also effectively be “greener”.

Description

FIELD OF THE INVENTION [0001] The present invention relates to seaweed polysaccharide based films. More specifically, the invention relates to the preparation of heat sealable biodegradable films utilizing semi-refined kappa carrageeenan as the film forming raw material that is inexpensive, eco-friendly, and dispenses with the use of gelling salt. BACKGROUND OF THE INVENTION [0002] In the mid-1990s, the outbreak of Bovine Spongiform Encephalopathy (BSE) or “mad cow” disease in Europe drew global attention. Subsequently, it has brought about a major change in safety perception in the areas of human, cattle and poultry health and welfare. Accordingly, the US Food and Drug Administration (FDA) advisory committee recommended that “gelatin” should no longer be considered generally recognized as safe (GRAS) for either food or pharmaceutical products. Consequently, attempts have been under way to identify alternatives to animal gelatin for use in soft capsules and edible applications. This...

AI Technical Summary

Benefits of technology

[0065] Films were cast at 80-85° C. on a prototype casting machine. The film is peeled and dried in flat condition at room temperature (30° C.) to attain desired moisture level in the range of 65-20%. The films prepared are 100 cm long, 10 cm wide, and 0.18-0.28 mm thick. And exhibit a tensile strength of 45 to 170 kg / cm2 and elongation of 77 to 292% for film containing 8-10% moisture. An important advantage of the invention is that the film obtained has substantially similar tensile strength and % elongation along both the length and breadth.

[0066] The formulated sol is degassed prior to casting to avoid film defects due to trapped air bubbles. The temperature at which films are cast in step (v) is in the range of 50-100° C. and viscosity is in the range of 100-500 cp. The moisture content of the film immediately after casting in step (v) is in the range of 50-90% and more particularly 55-60% for heat sealing immediately after casting. The moisture content of films at the time of heat sealing is 10-60%. The thickness of films obtained is in the range of 50-2000 μm and the tensile strength of films is in the range of 100-1000 kgf / cm2 and % elongation is in the range of 50-350%. The water vapour permeability of the thin films is in the range of 0.01-0.15 kg / m2 / h.bar.

[0067] The film obtained is non-tacky, odorless, and colorless and the % transmittance of light of 610 nm frequency is in the range of 10-99% depending on formulation and thickness. The water vapour permeability of the film was reduced from a range of 0.008-0.009 gcm−2h−1.bar to a range of 0.003-0.005 gcm−2h−1.bar by incorporation of natural rubber latex therein. If desired, one surface of the film is treated with a cross-linking agent to make the surface hydrophobic.

[0068] The film obtained can be converted to a pouch by pulse heat sealing at 100° C. During heat sealing glycerol is applied locally to a sealing area. In another embodiment of the present invention a variety of non aqueous fluids such as vegetable oils, acetone, dichloromethane, and hexane could be stored in the pouches for several days with only marginal loss of weight in case of the volatile solvents. Inventive Steps

[0069] 1. Recognition that inexpensive and eco-friendly semi-refined kappa carrageenan (SRC) can be upgraded by preparing a sol, centrifuging and using the clarified sol directly for further formulation suitable for film formation.

[0070] 2. Recognition that the counter ion in semi refined carrageenan is potassium and that this may allow one to dispense with the requirement of the KCl gelling salt while improving film properties such as color, tensile strength and clarity.

Problems solved by technology

Apart from the fact that the formulation is complex, use is made of KCl as gelling salt which can adversely affect film properties if such salt crystallizes from the solution.

The main limitations of the invention are that the formulation is too complex and a gelling salt is required which makes casting of the film considerably more difficult and can adversely affect the film quality.

The main limitation is the necessity of using alkali and multiple gums in the formulation.

Most importantly, apart from the more complex nature of the formulation, the main drawback of the prior art is that it fails to take advantage of semi-refined kappa carrageenan of the present invention and, instead, uses solid potassium kappa carrageenan which would be both costlier and less environmentally friendly to prepare.

Hence the preparation of such carrageenan is not eco-friendly.

It is known that whereas refined kappa carrageenan as obtained above is suitable for film formation, semi-refined kappa carrageenan, however, contains as much as 20-30% of plant debris which would be deleterious to film properties.

The major drawbacks of the prior art are the complex nature of the formulations and the poor tensile strength of films in several cases.

No application has been reported in the prior art of the use of seaweed polysaccharide films as biodegradable packaging material for storage of non-aqueous fluids.