Biopolymeric materials are becoming attractive in food and pharmaceutical packaging not only for the safety and security of the product but also for preventing aroma scalping, which is the result of chemical reactions of volatile compounds in the food with plastic packaging materials that cause off-flavor in the package. The goal of this study is to modify the structure of soybean protein with an enzyme (transglutaminase) and two types of lignin (alkali lignin (AL) and lignosulphonate (LSS)) and make a bioplastic by a casting method. The modified biopolymeric film was placed inside soybean oil containers to determine the effect of antioxidant activity of lignin on autoxidation and photooxidation of oil samples. Results of film FTIR and XRD spectra confirmed that the addition of lignin resulted in some changes in the secondary structure of soy protein film. Furthermore, lignin improved thermal stability of the film. Both lignin materials showed radical scavenging activity (55% AL and 13% LSS) and films containing AL have a brownish color, and LSS was more compatible in the protein matrix than AL. Results of soybean oil samples in contact with the modified lignin films showed that the modified biopolymeric film reduced volatile compounds that caused off-flavor up to 50% due to the improvement in radical scavenging activity (by 75%), UV-blocking ability in films containing AL (by 100%), water vapor barrier properties by 50%, and the modified films did not have any effect on the color of oil samples. Thus, applying modified biopolymeric film with lignin in the inner layer of food packaging system improved some aspects of their performance during storage, not only by preventing the migration of chemical compounds from the package to the food but also by radical scavenging activity and UV-blocking ability of the packaging system.

Novel protein-based biopolymer for food and pharmaceutical packaging application

ACS Fall 2021

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