Effect of PP Nanocomposite Multi-layered Film on Physicochemical Properties of Ready-To-Cook (RTC) Idli Batter and Prepared Idli Cake

Aim: The current study focuses on the effect of PP nanocomposite multi-layered film on physicochemical properties of stored idli batter and prepared idli cakes.

Place and Duration of Study: Department of Food Packaging and System Development at Indian Institute of Food Processing Technology, Thanjavur, Tamil Nadu, India, between Aug 2018 and Dec 2019.

Methodology: The developed PP nanocomposite multi-layered film composed with depositing silicon dioxide (SiO2) on polypropylene (PP) film (0.010 mm) and attached with ethylene-vinyl alcohol (EVOH 32%) film (0.066 mm). The Physico-chemical properties of developed multi-layered and commercial PP film stored idli batter with different blend ratios of rice to black gram (3:1 and 4:1) were evaluated in terms of pH, percent titrable acidity (% TA), colour value (∆E), viscosity (cP) and volume measurement (ml). Idli cake prepared with batter stored in multi-layered film and evaluated in terms of colour, texture and percent pore characteristics. The percent pore presents in per square inches of prepared idli cake with different blend ratios and fermentation time were analysed using the grayscale image in MATLAB.

Results and Discussion: The pH value of stored batter ranges from 6.7 to 4.5 or lower, to reach pH below 4.5 or lower commercially stored batter took 24 h and batter stored in the multi-layered film took 36 h at ambient temperature. The multi-layered stored batter showed better results of physicochemical properties in terms of fermentation time. Idli cake prepared with 3:1 blend ratio showed good results in terms of textural properties with compared to 4:1 blend ratio. Idli cake prepared with 3:1 blend ratio showed more pore percentage (21.88-36.80%) as compared to 4:1 blend ratio (18-32.98%) in per square inch. Due to higher barrier properties of the multi-layered film, the bacterial count increases at a slow rate and help to extend the shelf life of packaged batter more than 30 h at ambient temperature.