Stability of zein‐based films and their mechanism of change during storage at different temperatures and relative humidity

Abstract

Mechanical properties are the important parameters of the film which reflected the resistance of the films during their shelf life. In order to evaluate the stability of zein films preserved at different temperature and relative humidity (RH), tensile strength (TS) and elongation at break (EB) of zein films plasticized with glycerol and PEG-400 were observed during storage. Results showed that the EB decreased and TS increased during the first 6 days of storage at different RH and temperatures. RH which brought a maximum change in TS and EB were 43% and 65%, respectively. Films preserved at RH of 80% for 18 days lost its extensibility. Statistical analysis results showed that the correlations between the free sulphydryl content and mechanical properties at RH 43%, and between the moisture content and mechanical properties at RH 80% were more significant. A model was proposed to explain the change in TS and EB during zein film storage. Practical applications Zein is commonly produced from the by-product of bio-ethanol and starch industries and has excellent film-forming properties. Pure zein film is brittle, which has limited their application. Many researches have focused on the improvement of the mechanical properties of zein films. As a packing material, zein film should have excellent stability during the shelf life of the packaged food. So a systematic study about the effect of temperature and relative humidity on the mechanical properties of zein film plasticized with glycerol and PEG-400 during storage is necessary. The results presented in this paper would highlight the suitable applying environment of zein films, either actual or potential.