Preparation And Characterization Of Oridonin/Chitosan Composite Film And Its Application In Chicken Preservation

Food packaging can maintain food quality and nutritional value for a long time by protecting food by blocking external physical,chemical and biological factors.With the increasing awareness and requirements of food quality and safety,the development of efficient,green,more antibacterial,safe and non-toxic food packaging has become the current research hotspot.In this paper,oridonin and chitosan were used as the raw materials to prepare composite films.The effect of oridonin on the physical properties and antibacterial properties of the composite films was studied.The micro-structure and thermal stability of the composite films were analyzed.The preservation effect of the composite films on chicken was investigated.The main results are as follows:(1)Compared with the chitosan films,the oridonin/chitosan composite films had no significant increase in thickness and decreased in light transmittance,which the difference was not significant(P>0.05).Oridonin can reduce the water vapor permeability of the composite films and significantly improve the water barrier performance.When the amount of oridonin is 50?g/m L,the water vapor permeability of the composite films is 0.236(g·mm)/(m²·kpa·h),which is significantly lower than that of chitosan films(P<0.05).The tensile strength and elongation at break of the composite films decreased with the increase of oridonin addition.When the amount of oridonin was 50?g/m L,compared with chitosan films,the tensile strength and elongation at break of the composite films decreased by 6.91%and 10.50%,respectively.(P<0.05).(2)Using Escherichia coli and Staphylococcus aureus as test bacteria,the antibacterial effect of composite films on two kinds of bacteria were studied.The results showed that oridonin could enhance the antibacterial activity of the composite films.The antibacterial circle diameters of the composite film fluid with oridonin(50?g/m L)to E.coli and S.aureus were 14.12 mm and 14.68 mm,respectively.Compared with chitosan film fluid,the antibacterial activity increased by 28.13%and12.57%,respectively.(P<0.05).(3)After adding oridonin,the pH value of the composite film fluid of oridonin/chitosan has no change,which is a weak acid fluid.It did not affect the antibacterial activity of chitosan and oridonin.The results of the apparent viscosity test showed that the addition of oridonin could reduce the apparent viscosity of the composite film fluid.Therefore,with too much oridonin would affect the physical and mechanical properties of the composite films.(4)The infrared spectrum results of the composite films showed that the wave peak at 3351.56 cm^-1moved to 3430.08 cm^-1after oridonin was added,and the wave peak became sharp,indicating that oridonin and chitosan may form a new hydrogen bond,and they have certain compatibility.The results of SEM showed that oridonin was evenly disperse in chitosan films when the amount was lower than 25?g/m L,and the surface of composite films was smooth and flat.When the addition was less than 50?g/m L,the surface of the composite membrane is slightly rough,but there are no cracks and pores.When the content of oridonin continued to increase,the surface of composite films became more and more rough.The results showed that the compatibility of oridonin and chitosan decreased with the increase of oridonin content.The results of thermal stability showed that oridonin could improve the thermal denaturation temperature of the composite films.When the amount of oridonin was 50?g/m L,the maximum thermal denaturation temperature of the composite films was118.43?.The results showed that oridonin and chitosan had good compatibility,and they formed a stronger structure after blending,which improved the thermal stability of the composite films.(5)The results showed that the pH and the total number of colonies in the control group were 6.63 and 6.02 log cfu/g at the 5th day,which had been putrefaction.The pH and the total number of colonies in the pure chitosan(CS)group had risen to 6.52and 5.75 log cfu/g at the 7th day,which was close to putrefaction.The pH of the oridonin/chitosan composite films(OR-CS)group at the 9th day was 6.51,the total number of colonies reached 5.24 log cfu/g,which belonged to the second fresh meat.According to TVB-N results,TVB-N content of OR-CS group was lower than that of CS group and CK group.This indicated that oridonin and chitosan in the composite films inhibited the growth and reproduction of bacteria on the surface of chicken,slowed down the decomposition of protein,and prolonged the storage period of chicken breast for 4 days.(6)The results of drip loss rate test showed that the composite films could effectively reduce the drip loss rate and improve the water retention of meat.The results of color showed that the rate of L*and a*value reduction in CS group and OR-CS group was lower than that in CK group.The reason was the composite films could block the surface of meat from contacting with oxygen,slow down the oxidation rate of meat,and delay the surface brightness of chicken by inhibiting the growth of microorganism,which can protect the color of meat.(7)Sensory evaluation results showed that the odor of CK group had been sour and smelly on the 5th day,and the color had turned dark red.And it began to produce more mucus on the 3rd day,which was unacceptable on the 5th day.OR-CS group had no obvious odor on the 7th day,and the color was light red.The color,odor,viscosity and flexibility of the meat treated with composite films were greatly improved.In conclusion,the functional groups of oridonin and chitosan form hydrogen bond,which has good compatibility.The composite films with oridonin(50?g/m L)have good performance indexes,the best thermal stability,and good antibacterial activity.The composite films can extend the storage period of chicken breast for 4 days,and improve the quality of chicken breast during storage.This study provides a basis for its application in food preservation.