Preparation Of The Preserved Egg Coatings And Study On The Storage

The preserved egg is one of the most important Chinese traditional egg products. The preservation had restricted the development of the preserved egg industry. The coating technology had shown its advantange in many fileds, such as safety, healthy and simply. The coating materials have extensive sources and they could be cheap. The technology of the preserved eggs coating is easily to use in storage and develops quickly in recent years. Based on this research, the film-forming materials was choosed, different treatments were used in the film-forming properties improvement, the preserved eggs was coated with the coatings and stored at different temperature, the preservation effect was comparative analysed. The study results were following:Nitrocellulose and collodions were used as the main film-forming materials, according their characteristics, different additions were added to the coatings to improve the film-forming properties. Three formulas were gained in the study, they were nitrocellulose based coating, collodion based coating and the composite coating. The tested indexes included the sensory evalution, thickness, time of the film-forming, the water vapor permeability, oxgen permeability, tensile strength and elongation. Nitrocellulose based coating was make up as:nitrocellulose 10%(m/v), each of ethyl acetate and butyl acetate are 45%, glycerol and liquid paraffin were 1.5% of the total. The WVP of the film was 10.86 g.mm/m2d.Kpa, the OP value was 13.96 meq/Kg, TS value was 49.31 MPa, E value was 52.12%。Collodion based coating was made up of 99.0% collodion,1.0% liquid paraffin and 1.0% span 80 of the total. The WVP of the film was 7.44 g.mm/m2d.Kpa, the OP value was 9.76 meq/Kg, the TS value was 37.10 MPa, the E value was 46.35%. The composite coating was made up of 60% nitrocellulose based coating and 40% collodion based coating. The WVP of the film was 7.42 g.mm/m2d.Kpa, the OP value was 9.43 meq/Kg, the TS value was 60.28 MPa, the E value was 32.10%.Processing technic showed significant effect on the film-forming properties of the egg coatings. Thermal treatment, ultrasonic wave treatment and ultrasonic wave treatment combined with thermal treatment were used in the three coatings respectively. The tested indexes included the water vapor permeability, oxgen permeability, tensile strength and elongation. Results showed that:all the treatment could improve the properties of the films, with the treatments, the barrier properties and the mechanical properties were significant improved. The combined treatment was used in nitrocellulose coating, the treating temperature was 60℃and the treating time was 10min. thermal treatment was suitable for the collodion coating and the composite coating, the temperature was set at 60℃, and the treating time was 10min for collodion coatings and 20 min for the composite coating.The formulas were coated on the preserved eggs. The preservation effect was researched in different temperature. The tested indexes include the sensory evaluation, the weight loss rate, pH, the alkalinity, volatile basic nitrogen, physical property indexes, the total bacterial count and the coliform group. Results showed that:the composite film had shown the best preservation effect, it could keep for 105 days in the high temperature and 240 days in the normal temperature; the next one was collodion coating, it could keep the preserved eggs for 91 days in the high temperature and 210 days in the normal temperature; nitrocellulose group could store for 77 days and 195 days respectively; and for control group, it could only keep for 56 days and 120 days for the two temperature. During the room temperature, the composite film coating group, the collodion coating group and the nitrocellulose coating group were kept to deteriorated. Until the eggs got bad, the weight loss of the three groups were 8.93%,9.76%,9.36%; the pH value of the egg white and yolk were all higher than 9.50; the volatile basic nitrogen were 24.28,28.40,28.13mg/100g, the total bacterial count of the three groups were 280,310,330cfu/g. All the three coatings were achieved good effects.Ion chromatography was used to on the detection of the residual of nitrocellulose within the preserved eggs. The optimum chromatographic conditions were installed as: IonPac AS 14,11 mmol/L NaCO3, the flow rate was 1.5 mL/min. the range of linearity, regression equation and coefficient of correlation of NO2- and NO3- were gained: Y=0.0538X-0.0504, r=0.9977; Y=0.0512X-0.0312, r=0.9989。The LOD for NO2- and NO3- were 50μg/L and 100μg/L. There was no nitrocellulose residual between the samples with the method of ion chromatography.