Effects of pH modification in proteins from fish (Whitemouth croaker) and their application in food packaging films

- Proteins from fish (Whitemouth croaker) were obtained and modified at different pHs.
- Fish proteins were successfully modified through gelation at pH 2 and pH 10.
- Modification of fish proteins at pH 2 formed stronger gel network.
- Modified fish proteins were used to develop films for food packaging.
- Protein structure modification was responsible for soluble and less permeable films.

The commercial use of biodegradable proteins films is still limited due to their poor mechanical and barrier performance. However, processing of proteins to modify their structure may have a significant impact on films properties. Thus, the effect of thermal or pH-induced denaturation on the gelation behavior of Withemouth Croacker proteins was investigated in the development of films for packaging. Denaturation at pH 2 and pH 10 yielded the toughest protein gels. Gelation through pH modification is related to conformational changes in the structure of fish proteins, especially in secondary structure. Rheology tests demonstrated that a stronger gel was formed at pH 2, which might be due to the positively charged proteins. This behavior is related to the lower mesh size of the gel as demonstrated by small-angle X-ray scattering experiments. Gels prepared at both pH 2 and pH 10 had the ability to form cohesive films; however, no significant differences were observed between these treatments for water vapor permeability and mechanical properties. The modification of protein structure through gelation produced more soluble and less permeable films.

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