Osmotic Dehydration of Pink Radish (Raphanus sativus): Effects of NaCl Concentration and Temperature on Mass Transfer
Himadri Shekhar Konar
*
Uttar Banga Krishi Viswavidyalaya, India.
Shrilekha Das
Visva-Bharati, India.
*Author to whom correspondence should be addressed.
Abstract
Aims: This study investigates the osmotic dehydration behaviour of pink radish (Raphanus sativus), an inherently high-moisture root vegetable with a very short ambient shelf life, under varying salt concentrations and temperatures. This research is significant for developing low-cost preservation techniques to reduce post-harvest losses and create value-added radish products.
Study Design: Laboratory-based experimental study.
Place and Duration of Study: Uttar Banga Krishi Viswavidyalaya, Cooch Behar, India, during 2023–2024.
Methodology: Fresh pink radish slices (0.5 cm thickness) were immersed in sodium chloride (NaCl) solutions of 5%, 15% and 25% (w/w). Osmotic dehydration was conducted at temperatures of 40°C, 50°C and 60°C for 4 h, maintaining a radish-to-solution ratio of 1:5. All experiments were carried out in two replications. Samples were withdrawn at 0.5, 1, 2, 3 and 4 h intervals, blotted, weighed, and analyzed for moisture content using an infrared moisture analyzer. Mass transfer parameters—water loss (WL), solid gain (SG), and weight reduction (WR)—were computed using standard equations.
Results: Moisture content reduced from 95.7% w.b. to as low as 66.04% after 4 h in 25% NaCl at 60°C. WL and SG increased with rising temperature and concentration, with most mass exchange occurring during the first 2–2.5 h. Maximum WL values ranged from 0.122–0.349, and SG ranged from 0.027–0.254 across treatments. From the results, it was observed that at 50 °C with 25% concentrated salt solution the water loss, solid gain and weight loss were highest, reaching peak values of 0.349 and 0.254, respectively.
Conclusion: Higher osmotic concentrations and temperatures significantly enhanced WL and SG. Osmotic dehydration is an efficient and gentle moisture reduction technique for pink radish, improving its storability and suitability for further processing.
Keywords: Pink radish, osmotic dehydration, water loss, solid gain, mass transfer, preservation