polymer solutions were prepared for film casting as follows : glyerol or other plasticizers were added to the requisite amount of hot water . while maintaining the solution at an elevated temperature ( 80 - 90 ° c . ), then the dry ingredients were added and the solution vigorously mixed to homogeneity . the polymer solution was then continuously mixed under slow agitation for 1 - 2 hours to remove trapped air bubbles . once the polymer solution appeared to be smooth and free of lumps , it was cast into film , using either a casting box or with a standard draw down bar . care must be taken to ensure that the hot solution is cast in a uniform thin layer . in all of the experimental examples given below , film was formed by drawing the solution down onto a hot ( 90 ° c .) stainless steel belt with a gardener dye . the films were either air dried overnight at room temperature , or dried over a hot water bath and then removed for testing . films produced this way would initially be tested for thickness using a micrometer ( gauge ) and tensile / tear strength . the methods for measuring tear strength and elongation are those specified in astmd638 . normally 5 specimens are tested from each of 5 samples with the following conditions films that met these requirements would then be tested for hot water solubility by placing strips of the film in boiling water and then allowing the water to cool with the film sample in it . after cooling , the water would then be drained off and non - solubilized material would be placed with the drain dish in the drying overn . if the film was reconstituted after drying then the film was deemed to have maintained its structure during exposure to the hot water . if the film was not resistant to the water then it would become soluble and could be poured off . ( hence no film left after drying ) after a particular sample had been characterized as above , it would be subjected to the same process conditions under which commercial meats are produced . in particular the film would be wrapped around a particular meat substrate ( turkey , ham , chicken ) and then the wrapped meat sample dried in a convection oven until a protein skin could be seen forming on the sample . after this the sample was transferred into a steam cooker for the completion of cooking . the internal temperature of the meat sample would have to reach 70 - 80 ° c . after the completion of cooking , the sample was allowed to cool and the final product examined and results recorded . samples were then packed away under vacuum for shelf - life testing . films according to the invention which we tested on meat film wrap were also produced using the following polysaccharides , supplementary to starch and / or alginate , with gellan and / or konjac : agar , modified starches , guar gum , cellulose gum , modified cellulose gum , gum arabic , pullian and xanthate . in some of the formulations , the following proteins were included : gelatin , soya protein concentrate , soya protein isolate , whey protein concentrate , albumin , miscellaneous vegetable proteins , collagen and collagen hydrolysates . ( i ) either gellan and / or konjac is required for synergistic reaction with the carrageenan and other gums or polysaccharide to provide the desired hot water resistance . the proportion of gellan and / or konjac is that amount necessary to modify carrageenan sufficiently to ensure that the film will not disintegrate upon exposure to hot water . films could be made out of konjac or gellan alone , but these would be far less economical than the combination with other polysaccharide and in any event would have inferior physical properties , e . g . poor film strength , susceptibility to hydration , etc . ( ii ) the presence of starch or alginate is essential in these compositions to impart proper adhesion at the final film in its intended use as food film and casing . ( iii ) added protein is highly advantageous , to ensure proper adherence of the film to the meat after completion of cooking and for the aforementioned aesthetic purpose of mimicking the glossy appearance imparted by collagen . the film compositions may also be modified by the addition of compounds for specific purposes , such as 3 . colourants ( i . e . caramels , oleoresins and other synthetic or natural colourants — iron oxide ); with particular application to meat processing , black films can be produced using caramel , so that processors need no longer dip the meat products in a liquid caramel to obtain that colour . this film exhibited very high tensile strength ( 140 kg / cm 2 ) and good elongation ( 30 %). the film showed outstanding resistance to tear and had excellent handling properties . the film could be removed from a meat product after cooking very easily . ( low adhesion ) the film exhibited very high tensile strength ( 135 - 140 kg / cm 2 ) and elongation ( 35 %), and in particular showed excellent wet tensile strength . again this film showed outstanding mechanical handling properties and on a meat product had very good adhesion . this film exhibited good tensile strength ( 110 kg / cm 2 ) and elongation ( 35 %) and because of the addition of caramel powder was black in colour . the film had good adhesion properties as well as excellent mechanical handling properties . this film exhibited moderate tensile strength ( 100 kg / cm 2 ) and good elongation ( 25 %) and utilized collagen to give the film reasonable adhesion to a meat product . this film was completely clear and exhibited a very high tensile strength ( 200 kg / cm 2 ) with and elongation of 40 %. it showed very high adhesion and could not be removed from the meat product after cooking . finally , an unexpected advantageous property which we observed in films made according to the invention was efficient heat sealability at 180 ° c ., suggesting usefulness of these films as a replacement for hydroxypropyl methyl cellulose films in casings and food pouches .
edible films incorporating carrageenan in conjunction with konjac and / or gellan gums have been prepared as substitutes for edible collagen film currently used in meat processing . compositions according to the present invention overcome the inherent thermoreversibility of carrageenan gel and do not disintegrate from exposure to hot or boiling water . the film can readily be processed to form casing , bags or other packaging useful in the food industry .