Fabrication Of Edible Antibacterial Composite Films Based On Sodium Alginate And Their Properties

In recent years,with the increase awareness of environmental protection,public demands for the environment and food safety have become higher and higher."White pollution" caused by plastic package has received more and more attention from the society.Some countries have invested considerable manpowerand material resources in the study of edible packaging films,making it a new hotspot in the packaging field.In this thesis,sodium alginate and pulullan were used as main film-forming materials,and capsaicin as antibacterial factor was added to the blend film of sodium alginate/pulullan to prepare edible antibacterial cling film.The tensile strength,elongation at break,and water vapor permeability?WVP?coefficient were used as performance indicators.The optimum film formation condition of sodium alginate/pulullan was determined by single-factor experiments and orthogonal experiments,which are 1%sodium alginate and pullulan mixed solution with volume ratio of 3:1,glycerol of 20 wt%,and drying temperature at35°C.Results showed that the tensile strength of optimum composite film was 46.7MPa and the maximum elongation at break of 4.7%with the water solubility of8.4×10^-5g·s^-1,the WVP of 5.73×10^-13g·cm?cm²·s·Pa?^-1and the moisture content?MC?of 22%.The thickness of the composite films was in the range of 30-40?m,which increased slightly with the addition of antibacterial factor capsaicin.WVP,tensile strength and contact angle of the composite films also increased with the increasing contents of capsaicin.In contrast,moisture content?MC?and elongation at break of the blend film decreased gradually as the content of capsaicin increased.From the liquid culture antibacterial experiment,it can be seen that the blend film has a good inhibitory effect on Escherichia coli and Staphylococcus aureus.The sliced fruit fresh preservation experiment revealed that the composite films can prolong the shelf life of the sliced fruit,which indicates the potential of the composite film in the field of food packaging.Light transmission tests,infrared spectroscopy,scanning electron microscopy,and X-ray diffraction pattern were used to investigate the compatibility of the components in the composite films.The results showed that the composite film without capsaicin had good compatibility,because there was a strong hydrogen bond interaction between sodium alginate and pulullan.With the increase of capsaicin content,the hydrogen bond interaction between polysaccharide molecules of the blend film was weakened.When the capsaicin content reached 6%,local phase separation occurred in the blend film.