Study On Preparation And Properties Of Collagen Casing Made Of Fish Skin Collagn

The casing is one of the most important packing materials of meat product. And collagen casing, because of its excellent procession performance, has a large number of consumption in the international trade. The fish skin is rich in collagen, the resource of which is abundant, and with a high security. In a word the fish skin has a potential for developing into collagen casing. This paper intends to research the preparation processes of the collagen casing, and study on the structure change and the property relationships of it. This paper also aims to develop a fish-skin-maked collagen casing and determine its processing technology. And to of collagen casings made of fish skin, provide a reference and selection of comprehensive utilization of fishery resources and enrich the collagen casings market.The technical proposal for obtain depurated collagen matrix from raw fish skin was discussed in this paper. The skin was liming in the 30g/L lime milk for 6 days first, and then washing 2 times in 0.03mol/L HCl (5min/time) and 3 times in 0.115mol/L NH4C1 (30min/time), respectively. After liming and deliming, the contents and purity of collagen increased from 65.99g/100g to 75.85g/100g, and 75% to 87.31%, respectively. And the contents of ash is reduced to 0.673g/100g. The color and flavor are also improved to a certain degree. The structure of collagen fibers became looser, the puncture resistance weakened, the collagen matrix of fish skin prrified by the above operations.The process conditions of prepare and forming collagen dough were discussed too. The fish skin after purify expand by soak acid solution. The comparison of 5 kinds of acid showed that, when the purified fish skin soaked to the expansion rate as 250% in 0.05 mol/L phosphoric acid, the effect of forming collagen dough is under the best condition. The collagen base from the expanded fish skin can remove the color tissue by getting through a 80 or 200 mesh sieve in extrusion or heated respectively, then the collagen base was obtained. And the collagen dough can be prepared after collagen base mixed with the per-mixed ingredientsto became good at plasticity and rolling. The optimal formula was: 100kg collagen base, add 15kg CMC,5kg HPDSP,2kg STPP and 1kg glycerol.Compared several methods and materials, that enhance the casing properties, showed that, using hybrid modification method of add PVA(0.1g/100g collagen) to the collagen dough by blending method first, and then spray GLU(0.08g/100g collagen) to the extrusion casing, the tensile strength of collagen casing reached 36.48MPa, the elongation of break was 3.07%, and the light transmittance was 69.83%. There are no significant difference between the self-made collagen casing and the commercial casing. In addition, comparing the mechanical properties of the self-made casing and casing for commercial after cooking and baking, we found that self-made casing is more suitable for baking or smoked sausage packing.The change of collagen fibers through the preparation of collagen casing was characterized to explore the effects of structure and state of collagen fibers on the. properties of collagen casing in this paper. Observation through microscopic after tissue slice, collagen fibers became evacuate and the fiber gap increased after liming and deliming. DSC test showed that, after purification, the shrinkage temperature(Ts) of collagen fibers decreased, which means that purification only reduce the aggregation and the degree of order of collagen fibers, and the collagen structure remains completeness. The collagen fibers through different modification were characterized by zate potential, TG analyse, gel electrophoresis, scanning electron microscope (SEM) and fourier transformed infrared spectrum (FT-IR). Results showed that:After PVA modification, the hydroxyl on side chain of PVA molecular and the carbonyl structure on the main chain of collagen can be mutual associated to-form hydrogen bonds and so form stable blends, which makes the thermal stability of collagen casing has been greatly improved. On the other hand, the micro structure of collagen fibers became denser, the mesh holes were reduced; After GLU modification, the double aldehyde of GLU can form a covalent bond with collagen,which increased zate potential and molecular mass of the collagen, and the collagen fibers interconnected with each other and the multiple network structure was formed. Changes in the structure of collagen resulted in significantly improving in mechanical properties, heat and water resistance of collagen casings after modification.