Study On Whey Protein Concentrate-chitosan Antibacterial Composite Edible Films

This paper was financially supported by Grant from Hi-Tech Research andDevelopment Program of China (No.2008AA10Z308).In order to preparing a new high-performance edible film, the edible films were madefrom whey protein concentrate (WPC) and chitosan (CS), and were modified byultrasonic/microwave group, then been added in different volume fractioncinnamonaldehyde. The results showed that the modified film assisted byultrasonic/microwave had antibacterial and high performance. The whey protein concentrate-chitosan antibacterial composite edible films was used for coating preservation on egg. Theresults can provide a reference for the development of a new edible film.(1) The effects of whey protein concentrate-chitosan composite edible films assisted byultrasonic/microwave treatment on barrier propertiesUltrasonic treatment, microwave treatment and ultrasonic/microwave assisted treatmentall can improve the barrier properties of composite edible films, but the effects ofultrasonic/microwave assisted treatment was obviously, the barrier property of the modifiedcomposite edible films was the best.(2) The preparation and study of whey protein concentrate-chitosan composite ediblefilmsThrough the single factor tests and response surface method, the thesis analyzed theeffects of factors on the tensile strength (TS), elongation at break (E), transmittance (T),water vapor permeability (WVP), and oxygen permeability (OP) by single factorexperiments. Those factors included film-forming ratio WPC:CS, adding quantity of sorbitol(as plasticizer), the pH, and the time of ultrasonic/microwave assisting treatment. Theoptimal technology parameters were WPC:CS=5.8:6.2w/w, sorbitol concentration0.021g/mL, pH5.13, and ultrasonic/microwave assisting treatment time5min, the compositeedible films exhibited good physical properties. The SEM and FT-IR were used in order toinvestigate the interaction between two kinds of composition. The results showed that WPCand CS had good compatibility, and did not produce new chemical group.(3) Antibacterial activity of cinnamaldehyde, and whey protein concentrate-chitosancomposite edible filmsFilter paper diffusion method and double dilution method were separately used todetermine inhibitory effect, minimum inhibitory concentration and minimal bacteriocidalconcentration of cinnamaldehyde against Escherichia coli, and the disk inhibition zone assaywas used to qualitatively evaluate the antimicrobial activity of the whey proteinconcentrate–chitosan composite edible films. The results showed that cinnamaldehyde hadobvious inhibition on Escherichia coli, whey protein concentrate–chitosan composite edible films with cinnamaldehyde could inhibit the growth of Escherichia coli. With the increasingof the amount of enhancement, the inhibitory effect was more obvious.(4) The effects of cinnamaldehyde on whey protein concentrate-chitosan compositeedible films’ processing propertiesThe films were prepared by incorporated different volume fraction cinnamonaldehydeinto whey protein concentrate-chitosan film. Microstructures of films were characterized byFT-IR，and the influences of cinnamonaldehyde concentration on thickness, transmittance,tensile strength, elongation at break, water vapour permeability, oxygen permeability andantimicrobial properties were studied. Cinnamicaldehyde and whey proteinconcentrate-chitosan film had good compatibility. When cinnamonaldehyde concentrationincreased, transmittance and tensile strength of the film decreased. When adding0.5%cinnamonaldehyde concentration, film elongation at break reached the maximum57.5%.The film displayed obvious antimicrobial efficiency, when cinnamonaldehyde concentrationincreased.(5) The edible antimicrobial coating used on eggs for coating preservationUse cinnamaldehyde/whey protein concentrate-chitosan antibacterial composite ediblefilms for coating preservation on egg, egg weight, the loss during storage, Haugh unit, yolkindex, protein pH were studied, and compared with uncoating samples.1) During25days, with the increase of storage period, both coating and uncoatinggroups egg weight loss rate increased, the weight loss rate of control group was significantlyhigher than that of the coating group.2) With increasing storage period, both coating and uncoating groups egg Haugh unitdecreased, but the control group was significantly lower than that of the coating group.ofHaugh unit. During the storage, the coating group eggs’ grade always maintained above Blevel,which still belonged to the scope of edible eggs, but the control groups weremetamorphic, could not be edible.3) With increasing storage period, both groups egg yolk index decreased, but the controlgroups decreased significantly higher than that of coating group.4) With increasing storage period, the coating group protein pH value turned bigger, thecontrol group was firstly increased and then decreased and then increased.