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Abstract
The osmotic dehydration of carrot slices was carried out by two methods: at atmospheric pressure and under pulsed microwave vacuum conditions. In the first part, 20 experiments were conducted using a central composite design (CCD) with sucrose concentration (23–57% w/w), solution temperature (29–71°C), and time of osmosis (6–74 min). The slice thickness of 3.5 mm and sample-to-solution ratio of 1:10 (w/w) was kept constant throughout all experiments. Numerical optimization was done for higher water loss (WL) and lower solids gain (SG) using developed correlations and optimum experimental conditions were found at 56.82% sucrose concentration, 29°C solution temperature, and 20-min osmosis time with water loss of 27.73% initial weight and 14.41% initial weight solids gain. In the second part of the investigation, osmotic dehydration of carrot samples under pulsed microwave–vacuum conditions was carried out at the optimum sucrose concentration and solution temperature obtained in the first part. The effect of microwave power and time on mass transfer was studied. The experiments were designed by using a CCD with two variables, viz. microwave time per minute (7 to 41 s) during initial 5 min of osmosis and total time of osmotic dehydration (7 to 41 min). During each experiment, vacuum at 6.66 kPa and microwave radiation of 1 W/g of osmotic solution and carrot slices at different pulsating levels were maintained during initial 5 min in the chamber and then osmotic dehydration was continued for different time intervals. Correlations were developed using a regression technique and the optimum conditions were found with 40.46% WL and 11.58% SG at microwave time per minute of 36 s during the initial 5 min and osmosis time of 12.48 min. In comparison to the osmotic dehydration of carrots at atmospheric pressure, the application of combined pulsed microwave vacuum during osmosis was found to increase WL.
ACKNOWLEDGMENT
The authors are thankful to the Ministry of Food Processing Industries, Government of India, and the All India Council of Technical Education (AICTE) for their financial support to this research work.
Notes
Data error: ±0.1 for all variables.
Data error: ±0.1 for all variables.
*Highly significant; ns = nonsignificant.
ns = Nonsignificant.
ns = Nonsignificant.
*significant; **Highly significant.
ns = Nonsignificant.
ns = Non significant.