Research Article Physical-Chemical Properties of Edible Film Made from Soybean Residue and Citric Acid Wenjun Ma, 1 Sami Rokayya , 1,2 Liang Xu , 1 Xiaonan Sui , 1 Lianzhou Jiang , 1,3 and Yang Li 1,4 1 Department of Food Science, Northeast Agricultural University, Harbin, Heilongjiang 150030, China 2 Department of Nutrition and Food Science, Taif University, Al-huwayah, Taif 888, Saudi Arabia 3 National Research Center of Soybean Engineering and Technology, Harbin 150030, China 4 Harbin Institute of Food Industry, Harbin 150030, China Correspondence should be addressed to Lianzhou Jiang; jlz_neau@163.com and Yang Li; liyang_neau@163.com Received 27 December 2017; Accepted 19 April 2018; Published 6 June 2018 Academic Editor: Ana Moldes Copyright©2018WenjunMaetal.isisanopenaccessarticledistributedundertheCreativeCommonsAttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e effect of citric acid on the properties of soybean enzyme-assisted aqueous extraction processing (EAEP) residue edible film wasstudied.ewashedsoybeanEAEPresiduewasproducedbytheprocessofEAEP.Itwasdeterminedthatthewashedsoybean EAEPresidueisrichinfibers(76.10 ± 1.03%)andhasloweroilandproteincontents(7.74 ± 0.11%and3.50 ± 0.20%,resp.).Edible films intended for food packaging have been produced from the washed EAEP residue combined with glycerol, different concentrationsofcitricacid(0%,10%,15%,20%,25%,and30%),andsodiumhypophosphite.espectrahaveevidencedthatthe cross-linking reaction of citric acid and fibers has taken place in the residue. 30-CA films showed the highest tensile strength (17.52MPa) and the lowest water vapor permeability (7.21g·cm -1 ·s −1 ·Pa −1 ). Also, it indicated that citric acid can cross-link with the hydroxyls of polysaccharide and improve the compatibilization between the polymeric molecules to improve the in- termolecular interaction between polysaccharide molecules, so that the water uptake is reduced. e smooth surface and better translucencyofthefilmssuggestthattheEAEPresiduefilmstreatedwithcitricacidaresuitableforapplicationinfoodpackaging. 1. Introduction Soybeanisoneofthemostdominantoilseedsintheworld.A large number of soybean residues which contain mostly crude fiber are generated in the process of extracting oil, protein, or other soy products from soybeans. In recent years, some studies have analyzed different sources of fiber to prepare edible films. Pinecone nanocellulose fibers have been produced by using chemical and mechanical treat- ments for making nanocellulose films [1]. With the huge development in film processing, the films made of carrot fiberandcommerciallylowmethoxylpectinweredeveloped, and the effect of different sizes on the performance of composite films was explored [2]. Wheat straw hemi- cellulose films had been mixed with glycerol and different concentrations of citric acid [3]. Due to the large amount of productionandrelativelylowmarketvaluesofsoybeanfiber besides its rich residues, it has a great potential as a raw material for preparing films. For environmental and health considerations, enzyme-assisted aqueous extraction pro- cessing(EAEP)—anenvironmentallyfriendlywaytoextract soybean oil—has been developed [4]. EAEP results in four fractions: free oil, an oil-in-water emulsion, a liquid fraction (skim), and a residual fraction. e surplus amount of residues is the limitation of EAEP as it produces 2.8L of residues when extracting 1L of oil [5]. e insoluble fiber produced by EAEP is a potential material for producing edible films due to the large amount of fiber content. Using the EAEP residue to prepare edible films could improve the values of coproduct of EAEP and reduce its limitation. Films prepared by polysaccharides have good oxygen barrierproperties;ontheotherhand,thewatervaporbarrier property and moisture resistance are poor, due to the hy- drophilic properties of polysaccharides [6]. Water barrier Hindawi Journal of Chemistry Volume 2018, Article ID 4026831, 8 pages https://doi.org/10.1155/2018/4026831