Development of Instant Fermented Cereal-Legume Mix Using Pulsed Microwave Vacuum Drying

Abstract

Cereal-legume-based instant fermented food (Dhokla) is one of the most popular, indigenous fermented foods of India. Central composite design (CCD) was used to conduct fermentation experiments and optimization was carried out using response surface methodology (RSM). The effect of fermentation time (5.5–12.5 h), fermentation temperature (26.5–35.5°C), moisture content of batter (55–65% wb), and rice- to- bengal gram ratio (1.2–2.4) was evaluated with respect to total titratable acidity (TTA), total lactic count (TLC), firmness and overall acceptability scores (OAA) of steam-cooked Dhokla. The optimized condition for fermentation process was TTA 0.64 g mL⁻¹, total lactic count 221.62 cfu g⁻¹, firmness 146.35 g, and OAA score 6.82 at 12.5 h fermentation time, 26.5°C temperature, 65% moisture content of batter and 1.2 rice to bengal gram ratio. Further, the optimized fermented batter was dried by microwave vacuum using independent variables like thickness of batter (10–17 mm), microwave power density (3.5–10 W g⁻¹), and pulsating ratio (1.3–2). The responses studied were bulk density, rehydration ratio, color difference (ΔE), and OAA score. The best combination was found with bulk density 1014.22 kg m⁻³, rehydration ratio 4.55, ΔE 9.57 and OAA score 6.88 at 17 mm thickness of batter, 10 W g⁻¹ microwave power density, and 1.3 pulsating ratio.

Keywords:

• Cereal legume mix
• Fermentation
• Pulsed microwave vacuum drying

ACKNOWLEDGMENT

The authors are thankful to the Government of Gujarat, India, for supporting the research work.