Ultrasonic Lactose Crystallization
In many dairy processes, large volumes of whey — also referred to as milk permeate — are generated as a by-product. This effluent is rich in lactose, but its disposal is both costly and environmentally burdensome. By applying ultrasound to recover the lactose, the volume of waste can be significantly reduced, transforming a problematic effluent into a valuable resource. Ultrasonication facilitates rapid and efficient crystallization, yielding a high quantity of uniform lactose crystals suitable for commercial use.
Lactose Manufacturing
Lactose is produced from a concentrated solution of lactose (gained from whey). The concentrated lactose slurry must be cooled to a low temperature to precipitate crystals. After the precipitation step, the lactose crystals are separated by centrifugation. Afterwards, the crystals are dried to a powder.
Steps of Lactose Crystallization:
- Concentration
- Nucleation
- Crystal growth
- Harvesting/ washing
Improved Lactose Crystallization by Sonication
Ultrasound is well-known for its positive impact on crystallization and precipitation processes (sono-crystallization). Sonication improves the formation and growth of lactose crystals, too.
Sono-crystallization of lactose helps to gain the maximum yield of lactose crystals in a minimum time.
Ultrasonic glass reactor for inline sonication
A good crystal growth is substantial to ensure an efficient harvesting and washing of the lactose (extraction & purification). Sonication causes a supersaturation of lactose and initiates the primary nucleation of lactose crystals. Furthermore, continuous sonication contributes to a secondary nucleation, which ensures ar small crystal size distibution (CSD).
Ultrasonic lactose crystallization: Lactose crystallized under different conditions: ultrasonic energy input, added carrageenan or whey (WPC) influences lactose crystal size
study and picture: ©Sanchez-García et al., 2018.
Benefits of Ultrasound:
- maximum yield
- very short process time
- uniform crystal size
- controllable crystal size
- uniform crystal shape
From Feasibility to Inline Production: Sono-Crystallization of Lactose
Read more about the scale-up of ultrasonic lactose crystallization from bench-top to industrial production!
From Waste Effluent to Lactose
Due to the large dairy production, whey is often a by-product that is treated as waste effluent. The disposal of liquid whey is cost-intensive due to its high biological oxygen demand (BOD) and water content. When the lactose is recovered from the whey, the waste product is utilized in a post-processing step to produce lactose powder. The lactose recovery reduces the BOD of whey by more of 80% making the by-product useful and more environmental-friendly. An ultrasonically assisted crystallization process improves the crystal growth, yield and quality.
Lactose is used widely as ingredient in the food and pharma industry, as raw material for the production of lactitol or as base material for the microbial production of biodegradable polyesters.
UIP2000hdT, a 2000 watts powerful sonicator with flow cell for industrial inline crystallization
Ultrasonic Equipment
Hielscher Ultrasonics offers ultrasonic equipment for sono-crystallization processes – either for batch sonication or for the inline processing in an ultrasonic reactor. All Hielscher sonicators are designed to run continuously (24hrs/ 7d/ 365d) ensuring the maximum equipment utilization. Industrial ultrasonic devices from 0.5kW up to 16kW per unit are suitable for the commercial processing of large volumes of supersaturated suspensions.
Food-Grade Lactose Processing
Hielscher sonicators are highly effective for promoting and controlling lactose crystallization from supersaturated solutions. By applying intense ultrasonic cavitation, these systems enhance nucleation rates, reduce induction times, and enable the formation of uniform, well-defined crystals. This results in faster crystallization kinetics and improved control over crystal size and morphology. Ideal for both batch and continuous inline processes, Hielscher sonicators offer scalable solutions from R&D to industrial production. Their robust German engineering and compatibility with pharmaceutical-grade standards make them particularly well-suited for demanding applications in lactose purification, formulation, and processing.
Hielscher ultrasonicators are suitable for food- and pharma-grade production complying with cGMP standards. Hielscher sonicators are available with sanitary-grade fittings, ensuring full compliance with hygienic processing standards. The ultrasonic sonotrodes (also referred to as probes or horns) and flow-through reactors are designed with streamlined, easy-to-clean geometries, facilitating efficient maintenance and minimizing downtime. Notably, ultrasonic cavitation itself acts as a clean-in-place (CIP) mechanism, supporting internal surface cleaning during operation. For aseptic environments, all sonotrodes and reactors are fully autoclavable. Thanks to their compact footprint, Hielscher systems are easily integrated or retrofitted into existing production lines—making them ideal for upgrades in pharmaceutical and food-grade crystallization facilities.
Contact us today to get more information! Hielscher Ultrasonics offers various standardized as well as customized solutions for ultrasonic dairy and food processing!
Ultrasonicator UIP6000hdT with pressurizable flow cell. A heating-/ cooling-jacket allows to sonicate at elevated or lowered temperatures.
About Sonocrystallization
When power ultrasound is applied to induce and improve crystallization processes, it is known as sonocrystallization. Sonocrystallization is based on the application of “acoustic waves to induce physicochemical changes in the material. Some common applications of power ultrasound include its use to induce chemical reactions (sonochemistry) and to promote crystallization (sonocrystallization). These techniques have received the attention of several industries including pharmaceutical,chemical, and food industries given the advantage they offer. Ultrasound techniques are economically viable and relatively easy to incorporate into industrial operation. These techniques can be used to improve both reproducibility and yield of production; they are non-thermal and environmentally clean”. [Martini 2013, 4]
Nucleation and Crystal Growth
Crystallization is determined as the formation process, where solid crystals precipitate from a oversaturated solution, melt or gas.
The crystallization process consists in two major stages: the nucleation and the crystal growth.
During the nucleation, the dissolved molecules in the solution start to form clusters, which must be large enough to be stable under the operating conditions. Such a stable cluster forms a nucleus. After reaching the critical size to form a stable nucleus, the stage of crystal growth begins.
In the phase of crystal growth, the formed nuclei becomes larger as more molecules are bounded to the cluster. The growth process depends on the saturation grade and other parameters such uniform mixing, temperature etc.
The classical crystallization theory is based on the thermodynamic conception that an isolated system is absolutely stable when its entropy is invariable.
Facts about Lactose
Lactose (milk sugar) is a disaccharide built from glucose and galactose connected by a β(1→4) glycosidic bond.
Because of the presence of a chiral carbon, lactose can occur in the form of the following 2 isomer types: α- or β-lactose. Lactose is most frequently found as hydrated α-lactose monohydrate crystal. The other polymorph, anhydrous β-lactose, is less common and it crystallizes above 93.5°C. The α- and β-anomers have very different properties. The polymorphs can be distinguished by the specific rotation (+89°C and +35°C for α- and β-lactose, respectively) and solubility (70 and 500g/L (at 20°C) for α- and β-lactose, respectively). [McSweeney et al. 2009]
It is the main carbohydrate of milk and is found at concentrations of 2-8 wt%. Lactose is flavorless and has a low sweetness. Lactose acts as a reducing sugar and promotes the Maillard and Stecker reactions. Thereby, lactose is used to enhance color and flavor of food products such as bakery products, pastries and confectionery.
Lactose is a widely used food additive that functions as carrier, filler, stabilizer, and tablet diluent in food and pharmaceutical products.
α-lactose is the purest form, which is used for pharmaceutical products.
Lactose is an important ingredient when it comes to flavour, aroma and browning reactions.
Formula: C12H22O11
IUPAC ID: β-D-galactopyranosyl-(1→4)-D-glucose
Molar mass: 342.3 g/mol
Melting point: 202.8°C
Density: 1.53 g/cm3
Classification: FODMAP
Soluble in: water, ethanol
Literature / References
- Deora, N.S.; Misra, N.N.; Deswal, A.; Mishra, H.N.; Cullen, P.J.; Tiwari, B.K. (2013): Ultrasound for Improved Crystallisation in Food Processing. Food Engineering Reviews 5/1, 2013. 36-44.
- Dincer, T.D.; Zisu, B.; Vallet, C.G.M.R.; Jayasena, V.; Palmer, M.; Weeks, M. (2014): Sonocrystallisation of lactose in an aqueous system. International Dairy Journal 35. 2014. 43-48.
- Zettl, M., Kreimer, M., Aigner, I., Mannschott, T., van der Wel, P., Khinast, J., Krumme, M. (2020): Runtime Maximization of Continuous Precipitation in an Ultrasonic Process Chamber. Organic Process Research & Development, 24(4), 2020. 508–519.
- Kougoulos E, Marziano I, Miller PR. (2010): Lactose particle engineering: influence of ultrasound and anti-solvent on crystal habit and particle size. J Cryst Growth 312(23):3509–20.
- Yanira I. Sánchez-García, Karen S. García-Vega, Martha Y. Leal-Ramos, Ivan Salmeron, Néstor Gutiérrez-Méndez (2018): Ultrasound-assisted crystallization of lactose in the presence of whey proteins and κ-carrageenan. Ultrasonics Sonochemistry, Volume 42, 2018. 714-722.
- Patel, S.R.; Murthy, Z.V.P. (2011): Effect of process parameters on crystal size and morphology of lactose in ultrasound-assisted crystallization. Crystal Research Technology 46/3. 2011. 243-248.
Hielscher Ultrasonics manufactures high-performance ultrasonic homogenizers from lab to industrial size.