Films starch

The choice and combinations of different size components must take account of many factors if optimum results are to be obtained. Much has been published regarding the optimisation of size formulations in relation to desizing processes [177-183]. Cotton warp yarns sized with starch are normally woven at high humidity (80% and above) to keep yarn breakages low, as the starch film is brittle at low humidity. It has been shown [183], however, that improved weavability at moderate relative humidity (e.g. 65%) can be obtained using (a) starch/acrylamide or hydroxyethyl starch at not less than 15% add-on or (b) poly(vinyl alcohol), which gave excellent results even at a low add-on of 5-6%. 

Wilhelm, H. M., Sierakowski, M. R., Souza, G. R, Wypych, R (2003). Starch film reinforced with mineral clay. Carbohydrate Polymers, 52,101-110. 

Fig. la-C Scanning electron micrographs showing the surface of LDPE-starch films with 7.7% starch a before ageing b after ageing in sterile mineral medium and c after ageing in biotic mineral medium inoculated with A. paraffineus... 

Samples are optically smooth with 0.5-20 xm thickness. This is the most desirable sample type. The physical properties are uncompromised. In some cases, optically smooth protein and starch films can be prepared (without cryogenic slicing). 

This technique involves a reflectivity measurement, therefore, the Kramers-Kroenig transform is required to convert the resulting reflectance spectrum to a pseud-absorbance spectrum. This is a simple procedure for normal incidence measurements. Optically thick samples are desirable. Additional interfaces, such as air pockets, in the sample can induce reflection absorption bands - resulting in a spectrum of convolved reflection and reflection absorption features. In some cases, optically smooth protein and starch films can be prepared (without cryogenic slicing),... 

Mali, S., Grossmann, M.V.E., Gareia, M.A., Martino, M.N., and Zaritzky, N.E. (2004). Barrier, mechanical and optical properties of plasticized yam starch films. Carbohydrate Polymers. 56, 129-135. 

Cervera ME, Heinamaki J, Krogars K, et al. Solid state and mechanical properties of aqueous chitosan-amylose starch films plasticized with polyols. AAPS Pharm Set Tech 2004 5(1) E15. 

Krogars, K., Heinamaki, J., Karjalainen, M., Niskanen, A., Leskela, M., and Yliruusi, J. Enhanced stability of rubbery amylose-rich maize starch films plasticized with a composition of sorbitol and glycerol, Int. J. Pharm., 251, 205, 2003. 

Coffin, D. R., Fishman, M. L. Cooke, P. H. 1995. Mechanical and Microstructural Properties of pectin/Starch Films. Journal of Agricultural and Food Chemistry, Vol. 57, pp. 663-670. 

Our aim has been to elucidate the behaviour of starch films by investigating the properties of films prepared with pure amylopectin and amylose plasticised by glycerol and water. Even though amylose is known to be a good film former1 both amylose and amylopectin were studied in order to get better understanding of the phenomenon related to plasticisers. 

Starch films were prepared by a water-casting technique, Starch was dissolved in water by heating the starch suspension (1 or 2% starch) at 140°C for 30 minutes, After cooling the system to 100°C, the hot solution was dried on teflon moulds at 70°C. Before measurements, the films were stored at RH 50% and at 20°C for one week. 

Figure 1 Coefficient of viscosity fi/,) as a function of thickness of cassava starch films at different concentrations...

P < 0.05). The cassava starch films are less transparent than the gelatin films, where the opacity tended to zero and did not vary with the films thickness,24 but more transparent than the myofibrillar protein from Tilapia based films where opacity varied from 2 to 8 with the film thickness (0.017-0.088 mm).25... 

---