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Physical, Chemical and Biochemical Modifications of Protein-Based Films and Coatings: An Extensive Review

View Article: PubMed Central - PubMed

ABSTRACT

Protein-based films and coatings are an interesting alternative to traditional petroleum-based materials. However, their mechanical and barrier properties need to be enhanced in order to match those of the latter. Physical, chemical, and biochemical methods can be used for this purpose. The aim of this article is to provide an overview of the effects of various treatments on whey, soy, and wheat gluten protein-based films and coatings. These three protein sources have been chosen since they are among the most abundantly used and are well described in the literature. Similar behavior might be expected for other protein sources. Most of the modifications are still not fully understood at a fundamental level, but all the methods discussed change the properties of the proteins and resulting products. Mastering these modifications is an important step towards the industrial implementation of protein-based films.

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Reductive methylation, adapted from [207].
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ijms-17-01376-f002: Reductive methylation, adapted from [207].

Mentions: The substitution or addition of alkyl groups in organic compounds is called alkylation [207]. The alkylation of proteins mainly takes place at the amino groups of protein side chains. Therefore lysine is essential for this reaction. For example, the addition of formaldehyde in combination with sodium borohydride to the film building solution leads to reductive methylation (Figure 2). The reaction starts with the condensation of the amino group by a carboxyl group, resulting in the formation of an imine. The imine is subsequently reduced by a mild reducing agent, such as sodium borohydride, which is oxidized itself at the same time. Thereby methylamino groups form. These are immediately transformed into dimethylamino groups by additional formaldehyde and reducing agent, whereby formaldehyde acts as the oxidant. The formation of these dimethylamino groups, which replace the initially amino groups, is responsible for the change in the functional properties of the proteins [32]. The reaction is illustrated below.


Physical, Chemical and Biochemical Modifications of Protein-Based Films and Coatings: An Extensive Review
Reductive methylation, adapted from [207].
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037656&req=5

ijms-17-01376-f002: Reductive methylation, adapted from [207].
Mentions: The substitution or addition of alkyl groups in organic compounds is called alkylation [207]. The alkylation of proteins mainly takes place at the amino groups of protein side chains. Therefore lysine is essential for this reaction. For example, the addition of formaldehyde in combination with sodium borohydride to the film building solution leads to reductive methylation (Figure 2). The reaction starts with the condensation of the amino group by a carboxyl group, resulting in the formation of an imine. The imine is subsequently reduced by a mild reducing agent, such as sodium borohydride, which is oxidized itself at the same time. Thereby methylamino groups form. These are immediately transformed into dimethylamino groups by additional formaldehyde and reducing agent, whereby formaldehyde acts as the oxidant. The formation of these dimethylamino groups, which replace the initially amino groups, is responsible for the change in the functional properties of the proteins [32]. The reaction is illustrated below.

View Article: PubMed Central - PubMed

ABSTRACT

Protein-based films and coatings are an interesting alternative to traditional petroleum-based materials. However, their mechanical and barrier properties need to be enhanced in order to match those of the latter. Physical, chemical, and biochemical methods can be used for this purpose. The aim of this article is to provide an overview of the effects of various treatments on whey, soy, and wheat gluten protein-based films and coatings. These three protein sources have been chosen since they are among the most abundantly used and are well described in the literature. Similar behavior might be expected for other protein sources. Most of the modifications are still not fully understood at a fundamental level, but all the methods discussed change the properties of the proteins and resulting products. Mastering these modifications is an important step towards the industrial implementation of protein-based films.

No MeSH data available.