Preparation Of Bacterial Cellulose And Its Application In Chicken Preservation

Bacterial cellulose（BC）is a kind of fibrous material formed by fermentation of some microorganisms.Bacterial cellulose has the characteristics of extremely pure texture,3D network structure,high degree of polymerization,high crystallinity,high biological biocompatibility,good adaptability,so it has been applied in papermaking,medicine,sewage treatment and food industry.Colloidal particles can be irreversibly adsorbed on the oil-water interface to produce oil/water dispersions with very stable kinetics and thermodynamics.Essential oils contain aromatic substances with antibacterial,antioxidant and other functions,but the application of essential oils in food is greatly limited due to their volatile,hydrophobic and strong aromatic smell.In order to retain the antibacterial activity of essential oil and minimize its effect on food sensory properties,it is necessary to prepare a coating system of essential oil.In this paper,bacterial cellulose was obtained by microbial fermentation,and the effect of different ultrasonic time treatment on its properties was studied.Nanoscale bacterial cellulose was used to encapsulate thyme essential oil.The effect of bacterial cellulose/thyme essential oil emulsion on chicken preservation was tested.The following results were obtained:1.Preparation of bacterial cellulose and effect of ultrasound time on its propertiesAcetobacter xylinum ATCC 53524 was used as the fermentation strain,HS medium as the seed medium,SUC medium as the fermentation medium.After standing at 30°C for 5days,a layer of BC film grew on the surface of the medium.The dry weight yield of BC reached 2.03 g/L.BC was extracted,purified and crushed,and then treated with ultrasonic for different time（30 min,60 min,90 min）,the properties were characterized and compared.Electron microscope results showed that BC is a three-dimensional network structure composed of micro fibers entangled with each other,and the size is nanometer;FTIR results show that BC has three typical cellulose vibration bands:O-H vibration band in the range of 3700-3300 cm^-1,CH₂-CH vibration band in the range of 2900 cm^-1,and-CH₂and-CH vibration band in the range of 1700-1000 cm^-1;XRD results show that the three 2θdiffraction peaks of BC are 14.5°,16.4°and 22.5°,indicating that the crystal structure of BC is celluloseΙ_α;DSC results show that BC has an endothermic peak and an exothermic peak at 100～150°C and 300～350°C,respectively.Zeta potential showed that BC suspension was negatively charged.Rheological results show that BC has elastic properties and shear thinning behavior.The microstructure,rheological properties and chemical properties of BC were not changed after ultrasonic treatment,but the size,crystallinity,stability and thermal stability were changed.2.Application of bacterial cellulose/thyme essential oil emulsion（BC/TEO-E）in chicken preservationThe ultrasonic time of BC was determined to be 30 min,thyme essential oil:water=1:9（v/v）,adding BC of 0.05%,0.1%,0.2%,0.3%,0.4%,0.5%（w/v）in the system,and the effect of BC on BC/TEO-E stability and droplet size was explored.The results showed that with the increase of BC content,the stability of emulsion increased and the droplet size decreased.When the BC content was 0.5%（w/v）,the emulsion was no longer stratified and had the best stability.Optical microscope results show that the droplet size was the smallest and the distribution was the most uniform.The 0.5%（w/v）BC stabilized BC/TEO-E was sprayed on the surface of the fresh-keeping film.After air drying,the chilled chicken was wrapped and stored at 4°C for 12 days.The results showed that BC/TEO-E could significantly inhibit the growth of microorganisms in chicken,delay fat and protein oxidation and reduce the loss rate of weight.