Preparation Of Corn Starch-based Antimicrobial Films And Release Of Antimicrobial Agents

In recent years,with the increasing awareness of environmental protection,biodegradable food packaging materials have gradually become a research hotspot.Starch-based packaging material had great prospect of application with cheap and abundance rew material.The antimicrobial films were prepared using corn starch,chitosan and konjac glucomannan?KGM?as film forming material,glycerol as plasticizer,Tween-80 as surfactant,and incorporated different concentrations of cinnamon oil.The main results as follows:1.Preparation and physical properties of corn starch-based films.The effects of chitosan to KGM ratio,corn starch,glycerol,Tween-80 concentration and on the physical properties such as tensile strength?TS?,elongation at break?EAB?,water vapor permeability?WVP?and opacity of the composite films were explored.The composite membrane was divided into evaluation indexes by principal component analysis method,and the composite film was optimized by orthogonal test.The results showed that the optimum formula of corn starch-based composite films were chitosan and konjac glucomannan ratio of 1.0?0.6,corn starch concentration of 10%,glycerol concentration of 0.50%,and Tween-80 concentration of 0.30%.The properties of composite films under the optimal conditions revealed tensile strength of?22.53±0.16?MPa,elongation at break of?20.07±1.18?%,water vapor permeability of?1.87±0.01?×10^-12g?cm^-1?s^-1?Pa^-1,opacity of?4.13±0.07?mm^-1,showing a good physical properties.The composite film has the highest comprehensive score?0.76?.2.Preparation and properties of corn starch-based films incorporated with cinnamon essential oil.Four typical essential oils were selected as experimental target,including oregano oil,thymus oil,rosemary oil and cinnamon oil.The antimicrobial films were incorporated different concentrations of cinnamon oil.The antibacterial activity order against Staphylococcus aureus,Escherichia coli and Salmonella enterica of four essential oils was:cinnamon oil>oregano oil>thymus oil>rosemary oil.The TS and WVP decreased but EAB and opacity increased with the increase of cinnamon oil.The addition of cinnamon oil at a level ranging from 1.5%to 2.0%?w/v?decreased L^*value?P<0.05?and increased b^*and?E values?P<0.05?.The antimicrobial properties of the composite films increased significantly with the increasing of cinnamon oil's contents?P<0.05?.Synergistic antimicrobial activity was demonstrated against E.coli with combinations of Tween-80 and cinnamon oil,while the Tween-80 and cinnamon oil combination showed additive antimicrobial activity.Conversely,antagonistic effects were shown for combination against Staphylococcus aureus.The tensile strength and elongation at break of the antibacterial film with 2.0%?w/v?cinnamon oil were?22.53±0.16?MP and?20.07±1.18?%,and the antibacterial effect on the test bacteria exceeded 120 days.The corn starch-based antimicrobial films obtained a relative good physical properties and antimicrobial activity when the content of cinnamon oil was 2%?w/v?.3.The accumulative release of cinnamaldehyde from antimicrobial film was researched.No matter in 10%ethanol and 95%ethanol,The release rate showed a trend of rapid release fist and then to the balance.Accumulative release of cinnamaldehyde in 10%ethanol was affected by swelling and polarity.In this case,the equilibrium time was shorter and the release rate was lower.It is evident that the higher the temperature and the higher initial concentrations,the faster is the accumulative release of cinnamaldehyde in 95%ethanol.For the short-term diffusion M_F,t/MF,?<0.6,the estimated n-values was in the range of 0.1736⁰.3519.It demonstrated that the fickian diffusion was the predominant mechanism with release of cinnamaldehyde in 95%ethanol.At the same initial concentration,D_p values was increased with the increase of temperature,which reached up to 7.3662×10^-10 cm²s^-1.For the long-term diffusion M_F,t/MF,?>0.6,D_p values decreased by10⁵ to 10⁶ times.Partition coefficient K_P,F values was decreased with the increase of temperature.The results show that the antibacterial film could be applied to oils and fats.