Application Of Channel Catfish Skin Extract On Eggs Coating Preservation

Channel Catfish skin, with large amount of collagen and high added value, is a main by-product of Channel Catfish processing. This dissertation studies on the application of Channel Catfish skin to produce coating agent for egg preservation, with the purpose of making the best use offish skin resource, extending the shelf-life of eggs..Fish skin coating solution by enzymatic extraction and water extraction were used for coating processing egg of group A and B. During the storage period under room temperature 30℃, the preservation effect of both groups was significantly better than that of control group, after testing the sensory quality, weight loss ratio, relative density, yolk index and Haugh unit of coating eggs; and eggs of group B better than group A. Compared with control group, the shelf life of eggs in group A and group B was extended by 4 weeks and 6 weeks respectively. The analysis shows that the component of group A coating solution contained complete triple helix configuration that was collagen; triple helix configuration of group B coating solution had been destroyed while the (3-turn structure and β-sheet-collagen hydrolysate were kept.Through spray drying, freeze drying and heated-air drying to process the coating solution from water extraction, this paper studies different effects on usability and storability of the coatings by those three drying methods. The result shows that the yield of heated-air drying, freeze drying and spray drying are 4.13%,2.50%,4.63%; the order of excellence in reconstitution properties, jelly strength and preservation effect is freezing> heating> spraying; the order of excellence in storability is heating> freezing> spraying; the equipment of heated-air drying has a lower requirement that that of freeze drying. All things considered, in actual production, heated-air drying is more appropriate.Taking extraction yield and gel strength as indexes, single factor analysis and orthogonal experimental design were used to explore optimal conditions of water extraction and drying conditions, including extraction time, temperature and skin/water ratio, drying time and temperature. The optimal water extraction conditions were temperature 65℃, time 2.Oh, skin/water ratio 1:25, under which the extraction yield and gel strength of the obtaining coating were 58.9% and 213g. The optimal drying conditions were drying temperature 25℃ and time 3.5h, under which the obtaining coating was 204g.Different eggs coating fresh-keeping solution were prepared with fish skin coating as main material, adding glycerol as plasticiser and calcium chloride as enhancer. The coatings were applied to shell eggs, examining potential effects on eggs quality properties at room temperature 30℃. By single factor analysis and orthogonal experimental design, the best parameter combinations were gelatin 4.0%, glycerol 1.0%, calcium chloride 1.0%; under this condition, the shelf-life of coating eggs was longer than control group eggs.