Development of a simple and rapid dipstick paper-based test strip for colorimetric determination of nitrate and nitrite in water and foodstuffs.

A rapid user-friendly paper-based test strip using zinc microparticles in conjugation with Griess reagent was developed for nitrite and nitrate detection. Test strips were fabricated using a simple and fast method of step-by-step immersion into reagents so that each strip contained a single detection pad for nitrite detection and another separate pad for nitrate detection. To reduce nitrate to nitrite, zinc microparticles suspended in ethanolic solution of polyvinylpyrrolidone (PVP) were uniformly immobilized on the paper strips that were previously impregnated in the Griess reagent and dried. The Griess reagent components were optimized to reach the highest color intensity. The optimized test strip was able to determine both nitrite and nitrate with respective detection limits of 0.43 and 9.43 mg/kg and a detection time of 60 s. The performance of the new test strips was evaluated for the simultaneous colorimetric detection of nitrite and nitrate in water and different food samples.

Production and characterization of sage seed gum bioactive film containing Zataria multiflora essential oil nanoemulsion.

A bioactive film with two concentrations of sage seed gum (SSG) (1 % and 1.5 %) incorporating 2 % and 4 % Zataria multiflora essential oil (ZMEO) nanoemulsion was developed. Microbiological evaluation, including disc diffusion and time-kill tests, as well as mechanical and chemical characteristics namely film thickness, water-solubility, water vapor permeability, tensile strength and elongation at break, scanning electron microscopy (SEM), Fourier transform-infrared (FT-IR) analysis, antioxidant activity, and color analysis, were examined. Results showed that the antimicrobial properties of SSG films incorporating ZMEO nanoemulsion increased significantly (P < 0.05) by the multiplication of essential oil concentration. The films with 1 % SSG-4 % ZMEO showed acceptable antioxidant properties (∼65 %), and improved physical properties (508 % thickness increase, 56.63 % water solubility decrease, and 36.85 % water vapor permeability decrease), whereas tensile strength decreased only 29.8 %, and elongation increased 115 %. According to the results, SSG-ZMEO film may have positive potential impacts on increasing the shelf-life of foodstuffs.

Development of a natamycin-based non-migratory antimicrobial active packaging for extending shelf-life of yogurt drink (Doogh).

A natamycin-based non-migratory antimicrobial packaging for extending shelf-life of yogurt drink (Doogh) was developed. Firstly, the surface of low-density polyethylene film (LDPE) was modified with acrylic acid at different times of UV exposure (0-10 min) to produce carboxylic functional groups. Then, natamycin was applied to the UV-treated films to bind covalently with the pendent functional groups. The maximum grafting efficiency (81.96%) was obtained for the 6 min treated film. Moreover, surface properties of films were evaluated by Attenuated Total Reflectance/Fourier Transfer Infrared Spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM). Antifungal activity of different treatments of natamycin grafted film was evaluated against two common spoilage yeasts of Doogh including Rhodotorula mucilaginosa and Candida parapsilosis. Results showed that 6 min treated film provides maximum anti-yeast activity and can be applied to control fungal growth in Doogh. Natamycin-grafted film postponed the yeast spoilage in Doogh and prolonged its shelf-life to 23 days.