RESUMEN
To meet the need for food products to be safe and fresh, smart food packaging that can monitor and give information about the quality of packaged food has been developed. In this study, pH-sensitive films with sago starch and various anthocyanin concentrations of Brassica oleracea also known as red cabbage anthocyanin (RCA) at 8, 10, 12, and 14% (w/v) were manufactured using the solvent casting process. Investigation of the physicochemical, mechanical, thermal, and morphological characteristics of the films was performed and analysed. The response of these materials against pH changes was evaluated with buffers of different pH. When the films were exposed to a series of pH buffers (pH 3, 5, 9, 11, and 13), the RCA-associated films displayed a spectacular colour response. In addition, the ability of the starch matrix to overcome the leaching and release of anthocyanins was investigated. Higher concentrations of RCA can maintain the colour difference of films after being immersed in a series of buffer solutions ranging from acidic to basic conditions. Other than that, incorporating RCA extracts into the starch formulation increased the thickness whereas the water content, swelling degree, tensile strength, and elongation at break decreased as compared to films without RCA. The immobilisation of anthocyanin into the film was confirmed by the FTIR measurements. The surface patterns of films were heterogeneous and irregular due to the presence of RCA extract aggregates, which increased as the extract concentration enhanced. However, this would not affect the properties of films. An increase in thermal stability was noted for the anthocyanin-containing films at the final stage of degradation in TGA analysis. It is concluded that RCA and sago starch formulation has great potential to be explored for food packaging purposes.
RESUMEN
The study was aimed to investigate a color indicator containing dual curing resin composite luting cement and to plot the color change to the time of solidification of the cement. In addition some physical properties were studied. Specimens were made of a dual-cure resin cement (Maxcem Elite™ Chroma, Kerr, Orange, CA, USA) and polymerized by autopolymerization only, or with light initiated polymerization. A spectrophotometer was used to quantify the color change of the cement as plotted with the curing time. The efficacy of the curing process was studied by measuring water sorption and the ultimate flexural properties of the cement. The results showed that the flexural strength of cement after autopolymerization was 27.3â¯MPa and after light initiated polymerization 48.1â¯MPa. Young's modulus of bending was 2089.3â¯MPa and 3781.5â¯MPa respectively for the same cement samples. Water sorption after two weeks for the autopolymerization cement samples was -1.12â¯wt% and for the light initiated polymerization samples 0.56â¯wt%. Non-parametric Spearman's correlation was measured for autopolymerized cement samples between variables for color and solidification load (N), which showed a strong correlation between curing process and color change (pâ¯<â¯0.05). There was a correlation between the color change and degree of monomer conversion of the dual curing resin composite luting cement which contained a color indicator system for polymerization reaction. The study also suggested that autopolymerization only resulted in suboptimal polymerization of the cement. By additional light curing considerably higher flexural properties were obtained.