Modification of low-density polyethylene (LDPE) with vanillin to obtain flavored packaging film with improved gas barrier and flavor-releasing properties has been studied. The modification of LDPE with vanillin was monitored by Fourier transform infrared spectroscopy, wherein the appearance of new peaks at 1704.7, 1673.6, and 1597.2 cm À1 indicates the incorporation of vanillin into LDPE matrix. Films of uniform thickness were obtained by the extrusion of modified LDPE. Modified LDPE was found to have significantly higher gas barrier properties and grease resistance. Sensory quality of food products viz, doodhpeda (milk-based solid soft sweet), biscuit, and skimmed milk powder packed in LDPE-vanillin film showed that the doodhpeda sample had clearly perceptible vanilla aroma, whereas biscuit had marginal aroma and skimmed milk powder did not have noticeable aroma. When viewed in the light of imparting desirable vanilla aroma, results of the study indicated that LDPE-vanillin film has better prospects as a packaging material for solid sweets with considerable fat content when stored under ambient conditions. The release of vanilla aroma was further confirmed by gas chromatography-mass spectrometery analysis.
ABSTRACT:The chemical modification of low-density polyethylene (LDPE) resins with hexamethylene diisocyanate and toluene diisocyanate was achieved. The reaction of LDPE with diisocyanate was monitored by Fourier transform infrared spectroscopy, wherein the appearance of new peaks at 3326, 1620, and 1572 cm Ϫ1 corresponding to ONOH stretching, O(CAO)ONH 2 stretching, and ONOH bending in an amide moiety, respectively, was observed. Modified films of excellent clarity and uniform thickness were obtained by the solution casting of crosslinked polyethylene. The oxygen transmission rate (OTR), water vapor transmission rate (WVTR), grease resistance, and thermal properties of the modified films were studied. The results clearly indicate that the OTR was improved by 35% and that grease resistance was improved by 90 -125% in the crosslinked LDPE films with little change in their strengths. The heat seal characteristics, however, showed that relatively higher temperatures were needed to achieve efficient sealing in these films. Differential scanning calorimetry showed a decrease in the melting temperature from 104°C for LDPE to 101°C for both of the crosslinked LDPE films.
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