Synthesis of a novel tannic acid-functionalized polypropylene as antioxidant active-packaging materials

Authors: HAZER, BAKI - Bülent Ecevit University; Ashby, Richard - Rick

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2020
Publication Date: 11/17/2020
Citation: Hazer, B., Ashby, R.D. 2020. Synthesis of a novel tannic acid-functionalized polypropylene as antioxidant active-packaging materials. Food Chemistry. https://doi.org/10.1016/j.foodchem.2020.128644.
DOI: https://doi.org/10.1016/j.foodchem.2020.128644

Interpretive Summary: Certain vegetable oils contain fatty acids that consist of double bonds (unsaturated fatty acids) that can serve as sites for chemical reactions. Some of these fatty acids are composed of multiple double bonds (polyunsaturated fatty acids, PUFA’s). Linoleic acid (a major component of soybean oil, a major cooking oil) and linolenic acid (a major component of linseed oil, a well-known drying oil) are two of the most common PUFA’s. Oxidation is a reaction that can result in the formation of chemical species that can lower the quality of vegetable oil. These chemical species can be naturally induced through the action of light and atmospheric oxygen on the double bonds associated with the specific oil. Typically, cooking oils are stored in transparent plastic bottles. The presence of light and atmospheric oxygen in the bottle headspace can cause autoxidation leading to rancidity and the fomation of off-flavor compounds. Tannic acid is a compound that widely exists in plants and shows antioxidant activity. In this study, tannic acid was chemically grafted onto polypropylene, a widely used plastic typically used as wrapping material for different foods. Since foods naturally contain various fatty acids, the possibility of oxidation is present without the presence of antioxidants. This new tannic acid-functionalized polypropylene can be a promising packaging material especially in food preservative applications.

Technical Abstract: Autoxidation is a common reaction in unsaturated vegetable oils which promotes rancidity. This work focuses on the synthesis of a novel tannin-functionalized polypropylene as packaging material to inhibit the oxidation of vegetable oils. Commercially available chlorinated polypropylene was reacted with tannin in the presence of a base to prepare tannin-grafted polypropylene. An empty glass Petri dish (control), a chlorinated polypropylene-coated glass Petri dish (control) and a tannin-functionalized polypropylene coated glass Petri dish were exposed to linoleic acid and monitored for autoxidation of the linoleic acid samples under visible light at room temperature. Each sample was exposed for given periods of time and was analyzed by size exclusion chromatography to determine the effects of the autoxidation process on the linoleic acid molar mass. The molar mass of the linoleic acid exposed to the tannin-grafted polypropylene film was the lowest among the tested samples after each time period indicating that tannin-grafted polypropylene may be a promising packaging material for vegetable oils.