BACKGROUND The development of brewer's spent grain protein films with potential active packaging properties was investigated. Films were prepared by casting protein dispersions at different pHs (2, 8, 11), plasticizers (polyethylene glycol -PEG- or glycerol), and levels (0-0.25 g g-1 ) of PEG. Mechanical, water-barrier and solubility, optical, antioxidant (reducing power, ABTS•+ and lipidic radical scavenging), and antimicrobial properties of films were determined. Also structural characteristic of films were evaluated by ATR-FTIR. RESULTS Only films prepared at pH 2 and plasticized by PEG were homogeneous in appearance and could be manipulated, thus different levels of PEG were studied at this pH. Higher PEG concentrations increased water solubility, water vapor permeability and elongation at break and decreased tensile strength and elastic modulus. PEG increased α-helix structure only when 0.10 g PEG g-1 BSG-PC was used. This could be related with the better mechanical properties of F0.10 films (higher tensile strength, and elastic modulus) respect to the others films. Antioxidant activity depended on PEG concentration, whereas no antimicrobial properties against Bacillus cereus, Salmonella newport and Penicillium corylophylum were detected. CONCLUSION The formulations with 0.10 and 0.15 g PEG g-1 BSG-PC appear to be the most promising, balancing mechanical, water-barrier properties and antioxidant capacity of these films. Moreover, BSG proteins could be a cheap alternative for the preparation of biodegradable films, capable to be used as active food packaging. This article is protected by copyright. All rights reserved.

中文翻译：

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啤酒糟蛋白膜的物理、结构和抗氧化特性

背景研究了具有潜在活性包装特性的啤酒糟蛋白膜的开发。通过在不同的 pH 值（2、8、11）、增塑剂（聚乙二醇 -PEG- 或甘油）和 PEG 水平（0-0.25 g g-1）下浇铸蛋白质分散体来制备薄膜。确定了薄膜的机械、阻水和溶解度、光学、抗氧化剂（还原能力、ABTS•+ 和脂质自由基清除能力）和抗菌性能。薄膜的结构特性也通过 ATR-FTIR 评估。结果 只有在 pH 2 下制备并由 PEG 增塑的薄膜在外观上是均质的并且可以操作，因此在该 pH 下研究了不同水平的 PEG。较高的 PEG 浓度增加了水溶性，水蒸气渗透率和断裂伸长率降低，拉伸强度和弹性模量降低。仅当使用 0.10 g PEG g-1 BSG-PC 时，PEG 才会增加 α-螺旋结构。这可能与 F0.10 薄膜相比其他薄膜具有更好的机械性能（更高的拉伸强度和弹性模量）有关。抗氧化活性取决于 PEG 浓度，而未检测到针对蜡样芽孢杆菌、新港沙门氏菌和青霉菌的抗菌特性。结论 含有 0.10 和 0.15 g PEG g-1 BSG-PC 的配方似乎是最有前途的，平衡了这些薄膜的机械、防水性能和抗氧化能力。此外，BSG 蛋白可能是制备可生物降解薄膜的廉价替代品，能够用作活性食品包装。本文受版权保护。版权所有。