Effect of process parameters on crystal size and morphology of lactose in ultrasound-assisted crystallization

Crystallization of Lactose-Protein Solutions in the Presence of Flavonoids

Lactose is commonly crystallized in the presence of whey proteins, forming co-crystals of lactose and proteins. This work hypothesized that flavonoids such as rutin or epigallocatechin-3-gallate (EGCG) could be incorporated into the lactose and protein co-crystal structure since flavonoids may interact with both lactose and proteins. The interactions between whey proteins and flavonoids were first studied. Then, lactose-protein solutions were crystallized with and without flavonoids, measuring the kinetic parameters of crystallization and characterizing the resulting crystals. The incorporation of flavonoids in lactose-protein co-crystals depended on the hydrophilic nature of flavonoids. The hydrophilic EGCG was scarcely enclosed in the crystal lattice of lactose and avoided the inclusion of whey proteins in the crystals. In contrast, the less water-soluble rutin interacted with whey proteins and lactose, leading to the formation of co-crystals containing lactose, protein, and a large concentration of rutin (3.468 ± 0.392 mg per 100 mg of crystals).

Recovery of lactose from aqueous solution by application of ultrasound through millichannel

Instead of direct disposal of whey, extraction of valuable products from it may reduce the environmental pollution. In the present study, the effect of ultrasound irradiation through millichannel on recovery of lactose was investigated. The ultrasonic baths of varying amplitude (20–40%) and frequency (25–35 kHz), two different configurations of millichannel i.e., coil and serpentine, were used to know their individual and combined effect on the lactose yield. Box-Behnken design was employed to examine the interactive effect of different operating conditions. The recovery of lactose was enhanced approximately by 5–53% and induction time was reduced by 1.79–1.85 times in comparison to the conventional process. The size of the lactose crystals was reduced from 139.5 to 42.486 μm at 40% amplitude and 49.879 μm at 35 kHz frequency. Optimized condition showed 63% yield of lactose at 3.6 supersaturation, 35 kHz frequency, and 45 min of sonication time.

Effect of process parameters on the recovery of lactose in an antisolvent acetone/acetone-ethanol mixture: A comparative study based on sonication medium

Recovery of lactose from the whey using sonocrystallization was studied experimentally. The effect of sonication medium and irradiation power levels was evaluated using three different ultrasonic equipments. Effects of various parameters such as sonication time, pH of the medium, antisolvent (acetone and acetone-ethanol mixture) and concentration of lactose were determined. The optimal parametric conditions were analyzed using differential scanning calorimetry, thermogravimetric analysis, particle size distribution, and zeta potential measurements. Overall, the highest lactose recovery was obtained using a mixture of acetone and ethanol as antisolvent in bath sonication as well as atomization process.

Investigations in physical mechanism of ultrasound-assisted antisolvent batch crystallization of lactose monohydrate from aqueous solutions

Sonication is known to enhance crystallization of lactose from aqueous solutions. This study has attempted to reveal the mechanistic features of antisolvent crystallization of lactose monohydrate from aqueous solutions. Experiments were conducted in three protocols, viz. mechanical stirring, mechanical stirring with sonication and sonication at elevated static pressure. Mechanical stirring provided macroconvection while sonication induced microconvection in the system. Other experimental parameters were initial lactose concentration and rate of antisolvent (ethanol) addition. Kinetic parameters of crystallization were coupled with simulations of bubble dynamics. The growth rate of crystals, rate of nucleation, average size of crystal crop and total lactose yield in different protocols were related to nature of convection in the medium. Macroconvection assisted nucleation but could not give high growth rate. Microconvection comprised of microstreaming due to ultrasound and acoustic (or shock) waves due to transient cavitation. Sonication at atmospheric static pressure enhanced growth rate but reduced nucleation. However, with elimination of cavitation at elevated static pressure, sonication enhanced both nucleation and growth rate resulting in almost complete lactose recovery.

Ultrafast star-shaped acoustic micromixer for high throughput nanoparticle synthesis

We present an acoustically actuated microfluidic mixer, which can operate at flowrates reaching 8 ml min^-1, providing a 50-fold improvement in throughput compared to previously demonstrated acoustofluidic approaches. The device consists of a robust silicon based micro-mechanical oscillator, sandwiched between two polymeric channels which guide the fluids in and out of the system. The chip is actuated by application of an oscillatory electrical signal onto a piezoelectric disk coupled to the substrate by adhesive. At the optimal frequency, this acoustofluidic system can homogenise two fluids with a relative mixing efficiency of 91%, within 4.1 ms from first contact. The micromixer has been used to synthesize two different systems: Budesonide nanodrugs with an average diameter of 80 ± 22 nm, and DNA nanoparticles with an average diameter of 63.3 ± 24.7 nm.

Ultrasound-assisted crystallization of lactose in the presence of whey proteins and κ-carrageenan

The conventional process of lactose crystallization is prolonged, hardly controllable and the crystals have low quality. In this work, the effect of ultrasound on the crystallization of lactose in an aqueous system was assessed. Additionally, it was studied how the presence of whey proteins (which are a common impurity) and κ-carrageenan (that possess high water-binding capacity) could modify the process of lactose crystallization. Lactose solutions at 25% were sonicated in a continuous flow chamber at two different energy densities (9 and 50 J mL^-1) before the start of crystallization. Some of these lactose solutions were previously added with κ-carrageenan (0, 150 and 300 mg L^-1), with whey proteins (0.64%) or with both at the same time. Ultrasound sped up the rate of crystallization, decreased the crystal's size and narrowed the crystal size distribution (CSD). The presence of whey proteins accelerated the process of crystallization but induced the formation of amorphous lactose. Likewise, the rate of lactose crystallization was improved by the addition of 150 mg L^-1 of carrageenan. Whereas, the combination of carrageenan and whey proteins generated the smallest crystals (6 μm), the narrowest CSD and minimized the formation of amorphous lactose.

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

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.

Intensified recovery of valuable products from whey by use of ultrasound in processing steps - A review

The current review focuses on the analysis of different aspects related to intensified recovery of possible valuable products from cheese whey using ultrasound. Ultrasound can be used for process intensification in processing steps such as pre-treatment, ultrafiltration, spray drying and crystallization. The combination of low-frequency, high intensity ultrasound with the pre-heat treatment minimizes the thickening or gelling of protein containing whey solutions. These characteristics of whey after the ultrasound assisted pretreatment helps in improving the efficacy of ultrafiltration used for separation and also helps in preventing the blockage of orifice of spray dryer atomizing device. Further, the heat stability of whey proteins is increased. In the subsequent processing step, use of ultrasound assisted atomization helps to reduce the treatment times as well as yield better quality whey protein concentrate (WPC) powder. After the removal of proteins from the whey, lactose is a major constituent remaining in the solution which can be efficiently recovered by sonocrystallization based on the use of anti-solvent as ethanol. The scale-up parameters to be considered during designing the process for large scale applications are also discussed along with analysis of various reactor designs. Overall, it appears that use of ultrasound can give significant process intensification benefits that can be harnessed even at commercial scale applications.

Sonocrystallization and sonofragmentation

The application of ultrasound to crystallization (i.e., sonocrystallization) can dramatically affect the properties of the crystalline products. Sonocrystallization induces rapid nucleation that generally yields smaller crystals of a more narrow size distribution compared to quiescent crystallizations. The mechanism by which ultrasound induces nucleation remains unclear although reports show the potential contributions of shockwaves and increases in heterogeneous nucleation. In addition, the fragmentation of molecular crystals during ultrasonic irradiation is an emerging aspect of sonocrystallization and nucleation. Decoupling experiments were performed to confirm that interactions between shockwaves and crystals are the main contributors to crystal breakage. In this review, we build upon previous studies and emphasize the effects of ultrasound on the crystallization of organic molecules. Recent work on the applications of sonocrystallized materials in pharmaceutics and materials science are also discussed.