Fabrication and characterization of a pH-sensitive intelligent film incorporating dragon fruit skin extract

A novel intelligent pH-sensing indicator based on gelatin film and anthocyanin extracted from dragon fruit skin (Hylocereus polyrhizus) (DFSE) as a natural dye was developed to monitor food freshness by the casting method. Anthocyanin content of DFSE was 15.66 ± 1.59 mg/L. Dragon fruit bovine gelatin films were characterized by Fourier transform infrared spectroscopy (FTIR) and observed by a scanning electron microscope (SEM). Moisture content, mechanical properties, water solubility, water vapor permeability (WVP), light transmittance, color, and pH-sensing evaluations were evaluated for potential application. FTIR spectroscopy revealed that the extracted anthocyanin could interact with the other film components through hydrogen bonds. When the extract was added, films showed a smooth and clear surface as observed by SEM. The addition of anthocyanin increased the moisture content, thickness, and water solubility of the films, but decreased the WVP and light transmittance of films. Also, the incorporation of 15% v/v DFSE decreased the tensile strength from 17.04 to 12.91 MPa, increasing the elongation at break from 91.19% to 107.86%. The films showed higher ΔE with increasing DFSE content, which indicated that the film had good color variability. A significant difference in the color of the films was observed with exposure to different pH buffer solutions. The findings demonstrated that gelatin film incorporated with DFSE could be used as a visual indicator of pH variations to monitor the freshness of foods during storage time

Application of Starch Foams Containing Plant Essential Oils to Prevent Mold Growth and Improve Shelf Life of Packaged Bread

In the recent years, considerable attention has been allocated in the area of using natural preservatives in foods, especially vegetable oils.  Starch foams prepared from high amylose starch are useful for encapsulation of substances such as chemicals, liquids or solids, including flavor compounds, pharmaceuticals and essential oils. The foams have the ability to trap the active material and subsequently release the activity. Cinnamon oil is absorbed to foam starch microparticles and acts as an antimicrobial agent. This study was designed and implemented to evaluate the use of starch foam containing vegetable oil to prevent mold growth and improve packaged bread shelf life. For this purpose, first cinnamon essential oil was extracted with water by distillation method then, 250 groups of bread were prepared within polypropylene plastic bags. Various amounts of cinnamon essential oil (500, 750, 1000and1500ppm) with 1 g of starch foam powder inside sterilized filter paper were added to these packages.The obtained results of multi-way and intergroup repeated tests indicated that there was a significant difference (P <0/05) between the control groups and various groups containing cinnamon essential oil in terms of microbial load. In the groups containing essential oils, less increase was showed in microbial load and with increasing concentrations of cinnamon essential oil, mold and yeast growth rate decreased. It concluded that by using starch foam containing cinnamon essential oil in bulky bread packing at ambient temperature (25°C), the spoilage process of bulky bread can be postponed 3 to 6 days, and it can be used as an appropriate natural and antifungal preservative in packaging of bread