Ultrasound assisted intensified recovery of lactose from whey based on antisolvent crystallization

Abstract

The current work deals with understanding the fundamental aspects of intensified recovery of lactose from paneer (cottage cheese) whey using the anti-solvent induced sonocrystallization. Ultrasonic horn (22kHz) with varying power levels over the range of 40-120W has been used for initial experiments at 100% duty cycle and two different levels of ultrasonic exposure time as 10min and 20min. Similar experiments were also performed using ultrasonic bath for the same time of exposure but with at two ultrasonic frequencies (22kHz and 33kHz). It was observed that the lactose recovery as well as purity increased with an increase in ultrasonic power at 100% duty cycle for the case of treatment time as 10min whereas the lactose recovery and purity increased only till an optimum power for the 20min treatment. In the case of ultrasonic bath, lactose purity increased with an increase in the ultrasonic frequency from 22kHz to 33kHz though the lactose recovery marginally decreased. Overall, it was observed that the maximum lactose recovery was ∼98% obtained using ultrasonic horn while the maximum lactose purity was ∼97%. It was also observed that maximum lactose recovery was ∼94% for the case of ultrasonic bath while the maximum lactose purity was ∼92%. The work has enabled to understand the optimized application of ultrasound so as to maximize both the lactose yield and purity during the recovery from whey.

Effect of ultrasound on the kinetics of anti-solvent crystallization of sucrose

“…When the ultrasonic power reached 72 W, the nucleation rate reached a maximum, which was 2.897 × 10 11 m −3 ·s −1 , while the growth rate reached a minimum, which was 5.175 × 10 −8 m·s −1 . The observed increase of nucleation rate can be attributed to the cavitation effects including turbulence, higher heat and good mass transfer, leading to an increase in nucleation rate [16] . It was found that when the ultrasonic power exceeded 72 W, the nucleation rate was reduced and the growth rate was increased.…”

“…Compared with thermal and ultrasonic pretreatments, thermosonication pretreatment had the maximum lactose recovery. Gajendragadkar and Gogate [16] found that the purity and recovery of lactose were increased in a relatively short time due to the presence of ultrasound. In the ultrasonic bath, the purity of lactose was increased with the increase of frequency, but the recovery was decreased.…”

Sonocrystallization of Lactose from Whey

“…Regarding the crystal size, all the works agree that ultrasound increases the number of lactose crystals and produces smaller crystals with more homogeneous sizes [6,15,18,20,22,32,56]. Only one study has reported that there is no correlation between ultrasound (10-30 W, 20 kHz) and the size of lactose crystals [9].…”

“…On the other hand, the effect of different ultrasonic frequencies on the size of lactose crystals has been hardly reported, because nearly all the studies have used the similar frequencies (20-22 kHz). So far, only the work of Gajendragadkar and Gogate [6] has explored an ultrasonic frequency of 33 kHz. According to these authors, a frequency increase from 22 to 33 kHz reduced the crystal size and improved the lactose purity but decreased the yield of crystallization.…”

“…The bacterial degradation of whey causes a depletion of oxygen in the water and soil killing aerobic organisms, such as fish, insects, plants, and microorganisms. The high biological and chemical oxygen demand (BOD: 30-50 g L −1 ; COD: 60-80 g L −1 ) of the whey arise from its large content of carbohydrates, chiefly lactose (5-6%) [2,[6][7][8]. In consequence, the removal of lactose reduces more than 80% of the BOD and COD of whey, which minimizes the negative environmental impact of this by-product [9,10].…”