Blend films from konjac glucomannan and sodium alginate solutions and their preservative effect

In order to enhance the mechanical properties of konjac glucomannan film in the dry state and research the application of konjac glucomannan on food p reservation domain, blend transparent film was prepared by blending 3 wt % sodium alginate aqueous solution with 4.5 wt % konjac glucomannan aqueous s olution and dried at 40 degrees C for 4 h. The structure and properties of the blend films were studied by infrared, wide angle X-ray diffraction, sca nning electron microscopy, and differential thermal analysis. Crystalliniti es of blend films were increased with the increase of sodium alginate. The tensile strength and breaking elongation of the blend films in dry state we re obviously higher than those of both sodium alginate and konjac glucomann an films. Tensile strength of the dry blend film achieved 77.8 MPa when the retention of sodium alginate in the film was 27.9 wt %. The structure anal ysis indicated that there was a strong interaction between konjac glucomann an and sodium alginate, and this is resulted from the intermolecular hydrog en bonds. Moisture content and degree of water swelling of the blend films were increased due to the introduction of sodium alginate. Results from the film coating preservation experiment to litchi and honey peach showed that this blend film had water-holding ability. The fruit weight loss rate and rot rate both decreased by various values. (C) 2000 John Wiley & Sons, Inc.