Optimization of Intensification of Freeze-Drying Rate of Banana: Combined Applications of IR Radiation and Cryogenic Freezing

Abstract

A programmed experimental study on infrared (IR) aided freeze-drying of cryogenically (LN₂) frozen heat sensitive material viz. banana (Musa acuminata) rendered faster moisture separation rate compared to the conventionally frozen samples. Response surface methodology (RSM) could determine the simultaneous optimal freeze-drying conditions of 59.78°C IR temperature, 10 mm sample thickness, and 5 h drying time corresponding to the minimum moisture content of 4.11%, lowest final product temperature of 22.799°C, and maximum rehydration ratio of 1.72. Color difference, shrinkage, microstructure, pH, wettability, polysaccharide, and mineral contents of the cryogenically frozen freeze-dried banana at the optimal conditions have been determined coupled with Fourier Transform Infrared Spectroscopy (FTIR) and Carbon Hydrogen Nitrogen Sulfur (CHNS) analyses. Freeze-drying kinetics at optimal conditions have been evaluated and compared with literature published models and the “Handerson and Pabis” model was found to characterize the present case most closely among all drying models. A novel method for intensification of moisture separation rate leading to freeze-dried banana with high quality could thus be explored.

Keywords:

• drying kinetics
• food processing
• infrared radiation
• liquid nitrogen freezing
• microstructure
• RSM optimization

ACKNOWLEDGEMENTS

Authors are grateful to the University Grants Commission, New Delhi, India for financial support [(F.No. 36–99/2008 (SR)].

Notes

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Note: Factorial points: −1 (low level value), +1 (high level value); 0 (center point); α = ±1.

Drying models evaluated at optimal freeze-drying conditions.