Synthesis of polyvinyl chloride/chlorinated polypropylene-active natural substance derivatives for potential packaging materials application. Tannic acid, menthol and lipoic acid

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

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2022
Publication Date: N/A
Citation: N/A

Interpretive Summary: Animal fats and vegetable oils are widely used in the food processing industry. Unfortunately, these materials are composed of fatty acids that contain chemical sites where further chemical modification can ultimately result in the initiation of spoilage and rancidity. Autoxidation, in the context of fats and oils, is a reaction between unsaturated fatty acids and oxygen to form lipid intermediates known as hydroperoxides. This reaction is the initiation of rancidity and the spoilage process. In this study we have developed novel packaging materials utilizing polyvinyl chloride (PVC) and chlorinated polypropylene (PP-Cl) and reacted these well-known polymers with known renewable antioxidant materials (menthol, lipoic acid, and tannic acid) to produce active packaging materials with antioxidant properties. We report the synthetic process behind the production of these new materials, their characterization and their effectiveness in reducing autoxidation. Results showed that these newly synthesized materials delay the onset of autoxidation and consequently can prolong freshness in fats, oils, and fat/oil-containing foodstuffs.

Technical Abstract: Novel antioxidant active-packaging materials based on polyvinyl chloride (PVC) and chlorinated polypropylene (PP-Cl) that are designed to reduce the oxidation rate of vegetable oils are described. A novel one step route for the synthesis of tannic acid, lipoic acid and menthol functionalized PVC (PVC-Tann, PVC-Lip, PVC-Mnt) and PP-Cl (PP-Mnt, PP-Lip) was applied imparting antioxidative properties to the newly-formed materials. The halide groups of PVC and PP-Cl were reacted with the hydroxyl/carboxyl groups of tannic acid, lipoic acid, and menthol under mild conditions in the presence of sodium hydride to prepare the modified polymers. The resulting modified polymers were characterized by stress-strain mechanical measurement, 1H NMR, gel permeation chromatography (GPC) and thermogravimetric (TGA) analysis. Linseed oil, owing to its high linolenic acid content, was used to track the autoxidation process. By determining the viscosity of linseed oil after exposure to the functionalized PVC and PP-Cl polymers, the relative antioxidant effectiveness of the substituted polymers was determined. Each of the PVC- and PP-Cl-based polymers were active in delaying autoxidation. The PVC-based series of functionalized polymers showed a comparative efficiency of PVC-Tann (6-14 day delay in the initiation of autoxidation) > PVC-Mnt (5 day delay) > PVC-Lip (3 day delay) over the parental PVC polymer. The PP-Mnt series and PP-Lip polymers all delayed autoxidation by 8 days over the PP-Cl precursor material. The autoxidation process was further confirmed by monitoring peroxide formation in the exposed linseed oil samples through calorimetric analysis. The initiation of peroxide formation among the exposed linseed oil samples was measured at 95.9 +/- 5.3 degrees C, which was 5.6 degrees C higher than the linseed oil exposed to the PVC starting material. The results of this study indicate that these modified polymers may all be promising antioxidant packaging materials for vegetable oils and oil containing foodstuffs.