Broken Rice Protein Edible Films: Preparation And Property Research

Broken rice is a byproduct of the rice milling industry and edible films arefilms used in packaging industry．This paper discusses how Broken Rice Protein(BRP) was extracted from broken rice and was used to make edible films．The BRPfilms improved the added value of the broken rice， in accordance with thedevelopment trend of green environment practices．This paper researched the effect of different factors (pH，BRP concentration，glycerol addition and temperature)，which influenced the film＇s Tensile Strength(TS)，Elongation at Break(EB)，Water Vapor Permeability(WVP)，Transparency(TP)and Film Solubility(FS)．On the basis of single factor experiments，the TS、EB、WVP、TP and FS of films were used as evaluation indexes．The multi-targetcomprehensive weighted scoring method was adopted to comprehensively evaluatethe performance of films．With response surface analysis，a mathematical model ofBRP films was built：Y=-5410.71+705.38A+16.56B+29.04C-0.20AB+0.24AC-0.10BC-31.48A2-0.14B2-0.17C2． The equation formulated in this paper wassignificant．The lack of fit was not significant，which indicated that the model couldbe used to predict actual results．The optimal process condition of protein filmspreparation was：pH of11.5，BRP concentration of5g/100mL，glycerol addition of2.1g/100mL，reaction temperature of87℃．Under this condition，the TS reached2.47MPa，the EB reached175.68％，the WVP reached4.84g.mm/kPa.d.m2，the TPreached86.1％，the FS reached27.88％and synthesizing evaluation score reached78.44． The experimental values were in close agreement with the predictedvalue(78.63) with a difference of0.24％，which means the model could be used topredict the test results due to the agreement of the model and with the test results．Furthermore more，in order to improve the mechanical properties of BRPedible films，TS and EB of films were used as evaluation indexes．Modificationmethods，including physical method，chemical method and enzymic method wereused to enhance the properties of protein edible films．The results showed that allthe three modification methods could improve the film＇ s property to somedegree．When the treatment condition of untrasonic was60W、40min，TS reached6.43MPa，EB reached63.05％，WVP reached3.95g·mm/kPa.d.m2，TP reached83.3％，and FS reached22.6％．When the addition of sodium sulfite was0.05％，TS reached7.89MPa，EB reached75.92％，WVP reached6.44g·mm/kPa.d.m2，TP reached81.1％，FS reached28.4％．When the addition of TG was0.1％，TSreached5.64MPa，EB reached25.78％，WVP reached7.19g·mm/kPa.d.m2，TPreached72.6％，FS reached25.5％． BRP，Soy Protein Isolate (SPI)，Wheat Gluten (WG) and Whey Protein Isolate(WPI) were used as composite material to prepare edible protein films．The resultsshowed that：the TS and EB of BRP/SPI composite films have no significantchanges when compared with single SPI films．However，the WVP and FS weresignificantly improved and TP was decreased to some extent．The TS and EB ofBRP/WG composite films were significantly improved，but there was a slightdecrease of FS．The TS and EB of BRP/WPI composite films were significantlyimproved at the highest level，but the rest of the indicators showed a downwardtrend．WPI was further selected as raw material to study the performance betweenBRP and BRP/WPI composite films．The results showed that：the films can achievebetter performance when the mass ratio is7:3．Under these conditions，thecomposite film＇s TS reached6.61MPa，EB reached23.84%，WVP reached8.24g·mm/kPa.d.m2，TP reached75.4%，FS reached29.2%．Results of Scanning Electron Micrograph (SEM) showed that，the ultrasonicimproved the surface and the bottom structure of the films，making the films moresmooth，uniformly and thin．The use of reducing agents sodium sulfite and TG canimprove the bottom structure of the films，leading to the reduction of sodiumsulfite-modified film＇s thickness and creat a neat sectional view of TG modifiedfilms．The SEM of single films and composite films revealed that：the difference ofsurface structure for SPI，WG，WPI films was small．There were more pores onthose films，however，the bottom structure of composite films was smoother anddenser． Little change in cross-sectional shape of the composite films wasobserved．The sectional view of a single WPI films were extremely dense．The results of Fourier Transform Infrared Spectroscopy (FTIR) showed thatthe ultrasonic，sodium sulfite，and TG could modify the intensity of the absorptionpeak，which indicates that ultrasonic modification，sodium sulfite modification andTG modification had changed the secondary structure of the protein．Modificationmethods could change the performance of the edible films in various degrees．Theprocessing technique may modify the symmetry, quantity and concentration of theprotein group，which changed the protein molecule of the polypeptide chain．TheFTIR of composite films and single films showed obvious changes to the structure，indicating that there might be a corresponding chemical reaction betweengroups．So，we may draw the conclusion that the properties of composite films andsingle films differ significantly．...