Study On Preparation And Application Of Natamycin Emulsion And Antibacterial Film

Natamycin is an odorless,low-dose and safe food antiseptic and antifungal agent which could react with sterol compounds in the membrane of fungus and destroy cell membrane structure,thus converting the cell membrane permeability to effectively inhibit and kill mold and yeast.On the other hand,natamycin is prone to decomposition when exposed to light and oxyen because of its cyclic chemical structure,which greatly limits its appliation to food preservation.The construction of active carrier system can effectively solve this problem.In this study,natamycin emulsions were fabricated based on skimmed milk powder,natamycin and sodium carboxymethyl cellulose with pH induction to study the conditions for forming the emulsion with a high encapsulation rate and the effects of embedding technology on the solubility,antibacterial and photosensitivity of natamycin.Meanwhile,atomic force microscopy,infrared spectroscopy and XRD diffraction analysis were used to characterize the structure of the natamycin emulsion.Furthermore,the stability of the emulsion was studied.Next,natamycin antibacterial membrane was prepared and its physical and antibacterial properties were studied.Finally,the natamycin emulsion and antibacterial film were applied to the preservation of baked goods and sweet potatoes,respectively.The main findings are as follows:1.Preparation and properties of natamycin emulsion(1)The conditions for forming a high encapsulation rate and good stability of natamycin emulsion are: skim milk powder solution(10 mg/m L),natamycin solution(6 mg/m L)and sodium carboxymethyl cellulose solution(4 mg/m L),the volume ratio of which was 1 : 1 : 1.The size of the nanoparticles formed was about 238.46 nm,the Zeta potential was about-42.8 m V,and the encapsulation rate was about 92.14 %.After storage at 4 ? for 30 days,the emulsion remained stable and still had good reconstitution.(2)The embedding technology effectively increased the solubility of natamycin in the water,basically having no effect on the bacteriostasis of natamycin,but can improve the photolysis resistance of natamycin.Atomic force microscope results showed that the dispersion of the emulsion was relatively good.Fourier infrared spectroscopy showed that no new characteristic peaks appeared in the natamycin emulsion,but the intermolecular force and hydrogen bonding were weakened.XRD diffraction analysis showed that the crystal form of natamycin changed.(3)Penicillium,aspergillus,rhizopus and yeast were used as the test bacteria to evaluate the antibacterial activity of natamycin emulsion at different pH,temperatures and metal ions.The results showed that the natamycin emulsion has a good inhibitory effect on the growth of mold and yeast and a better stability at pH 5 ~ 7.Natamycin emulsion is suitable for storage and preservation of neutral and weakly acidic foods,but the dosage needs to be increased in alkaline environment.After thermal treatments from 4 ~ 121 ?,the antibacterial activity of natamycin emulsion was not influenced.Different metal ions have distinguished effects on the antibacterial activity of natamycin emulsion.When natamycin emulsion is used for food storage,it should be avoided in foods containing more Ca2+ and Mg2+ in the matrix,while the priority should be given to the foods that rich in Zn2+ and Na+.If necessary,the antibacterial effect of natamycin emulsion can be improved by adding Zn2+.2.Effects of Natamycin on Fresh—keeping of bakeryNatamycin can inhibit efficiently fungal growth and reproduction in bakery products.Natamycin emulsion has better inhibition effect on mold than natamycin suspension and sodium diacetate.Under the same experimental conditions,natamycin emulsion can prolong the shelf life of baked foods for significantly longer time than sodium diacetate.The optimal concentration of the treatment liquid of natamycin applied to the preservation of the surface of baked food is 300 mg / kg and the final concentration of the emulsion is 6 mg / kg.3.Preparation and properties of edible antibacterial film of natamycinNatamycin emulsion has good compatibility with sodium alginate.Due to the interaction among the molecules of the membrane components,the mechanical properties and barrier properties of the composite membrane were enhanced through the addition of the emulsion,and the thermal stability was improved.Natamycin as an antibacterial agent added to the sodium alginate film significantly enhances its antibacterial effect,and the composite film has a significant inhibitory effect on the growth of yeast and mold.4.Effects of Natamycin on Fresh—keeping of Sweet Potato during StorageAfter a storage period of 120 days,the sweet potato of the blank group and the natamycin suspension treatment group had obvious mildew spots,while the sweet potato of the natamycin emulsion and membrane liquid treatment group had no obvious plaques,which indicated that the treatment of sweet potato with natamycin membrane solution had a good preservation effect during the experiment period and could effectively prolong the storage time of sweet potato after picking.During the storage of sweet potatoes,the nutrition content of sweet potatoes such as moisture content,soluble protein,total starch,Vc,brassin content showed a downward trend.The starch content generally showed a downward trend with the extension of storage time,and the fastest decline was from 60 to 120 days of storage.However,the soluble sugar content of sweet potato tubers showed a trend of increase first and then decreased with the extension of storage time,reaching the maximum value on 60 th day during storage.The soluble sugar content increased in the early stage of storage due to the small molecular sugars decomposed from starch,while the late starch decomposition rate was reduced,and the soluble sugar content gradually decreased.The content of flavonoid glycosides in sweet potatoes showed a trend of increase first and then decrease.The peak value appeared at 30 th days of storage,and then decreased with the increase of storage time.During storage,the sweet potato of the natamycin membrane liquid treatment group had the best quality,which could effectively prolong the storage time of sweet potato.In summary,the natamycin emulsion prepared on the principle of pH drive has good storage stability,reconstitution stability,antibacterial stability,and certain thermal stability,which is suitable for storage and preservation of neutral and weakly acidic foods.The natamycin / sodium alginate film prepared with this emulsion will be expected to play a good role in food packaging as an edible composite antibacterial film.