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Zein films with unoxidized or oxidized tannic acid
Author(s) -
Santos Talita M,
Souza Filho Men de Sá M,
Muniz Celli R,
Morais João Paulo S,
Kotzebue Lloyd Ryan Viana,
Pereira André Luís Sousa,
Azeredo Henriette MC
Publication year - 2017
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.8327
Subject(s) - tannic acid , ultimate tensile strength , solubility , chemistry , chemical engineering , water resistance , aqueous solution , coating , materials science , nuclear chemistry , composite material , organic chemistry , engineering
BACKGROUND Corn zein is a predominatly hydrophobic protein, forming films with relatively good water resistance. Tannic acid, especially in its oxidized form, is supposed to cross‐link proteins including zein, which may be explored to further enhance the water resistance of zein films. The effects of different contents (0–8 wt%) of unoxidized and oxidized tannic acid ( uTA and oTA , respectively) on the properties of zein films at different pH values (4–9) were studied, according to central composite designs. RESULTS Increasing tannic acid contents and pH values resulted in decreased water solubility and increased tensile strength and modulus of films. The presence of tannic acid provided the films with a yellowish color and increased opacity. Paired t ‐tests indicated that oTA films presented higher tensile strength, lower water vapor permeability and lower water solubility than uTA films. CONCLUSION Higher tannic acid contents and pH values resulted in films with better overall physical properties, which might be ascribed to cross‐linking, although the films were still not water resistant. The resulting films have potential to be used for food packaging and coating applications. © 2017 Society of Chemical Industry