Ultrasonically Improved Ice Cream Production

The application of power ultrasound has several beneficial effects on the production of high-quality ice cream. The major advantages of sonication include the reduction of the crystal size and the acceleration of freezing in ice cream. Thereby, ultrasonication improves the quality and consumer sensation whilst simultaneously reducing production costs.

Ultrasonic Effects on Ice Cream Manufacturing

Ice cream production involves a sophisticated processing in order to obtain a high-quality sweet food product that satisfies customer demands. The elaborated processing steps result mainly from the fact that ice cream is one of the most complex foods: ice cream is a foam as well as an emulsion. It contains ice crystals and a non-frozen liquid blend. High power ultrasound applied during ice cream manufacturing can promote ice crystal nucleation to accelerate the heat and mass transfer process accompanying the freezing process. Thereby, sonication reduces the crystal size and shortens the freezing time in ice cream production. Research by Mortazavi and Tabatabaie showed that the freezing time in ice cream processing could be reduces by about 30% by sonication for 20 min.

Ice Cream Production and the Benefits of Ultrasound

For ice cream production, an ice cream mix is required. This ice cream mix consists of milk, milk powder, cream, butter or vegetable fat, sugar, dry mass, emulsifier, stabilizer as well as additives such as fruits, nuts, flavours and colouring. This special mixture has to be homogenized and pasteurized, then it is stirred slowly during the freeze process to prevent the forming of large ice crystal. Thereby, very small air bubbles are mixed in (so-called aerating process) to froth the ice cream achieving a smoothly textured cold dessert. Ultrasonication promotes the uniform distribution of all ingredients of the ice cream mixture and contributes at the same time to the pasteurization. Read more about ultrasonic pasteurization of liquid foods here!
Subsequently, ultrasonication is applied during the freezing stage during ice cream production. Ultrasonication promotes the nucleation and growth of ice crystals, so that the freezing process is significantly accelerated. At the same time, sonication reduces the size of ice crystals so that uniformly small ice crystals are obtained. This gives the ice cream a smooth texture and a pleasant mouth feel – both quality attributes, which are highly valued from the consumers.

Ice Cream Production Steps

The manufacturing of ice cream has five stages:

1. preparation of the ice cream mix
2. homogenization, pasteurization, ageing of the ice cream mix
3. freezing and aeration
4. shaping and moulding
5. hardening and packaging

Steps of Ice Cream Production.
Source:Dairy Processing Handbook. Published by Tetra Pak Processing Systems AB, Lund, Sweden. p.387.

Ultrasonically Promoted Ice Cream Freezing

During the freezing process, crystals are formed fom supercooled water. The morphology of the ice crystals plays an important role regarding the textural and physical properties of frozen and half-frozen food. As size and distribution of the ice crystals are of special importance for the quality of thawed tissue products, for ice cream, smaller ice crystals are preferred because large crystals results in an icy texture. Nucleation is the most important factor to control the crystal size distribution during crystallization. Thereby, the freeze rate is usually the parameter used for controlling size and size distribution of the ice crystals in ice cream. During the whipping and freezing, air is injected to achieve the smooth texture of ice cream. The so-called “over-run”, the amount of air injected, is proportionated – specifically to the particular recipe – proportionally to the combined volume of solids and water. So, the over-run varies due to the different ice cream formulations and the processing streams. Standard ice cream shows an over-run of 100%, which means that the final product consists of an equal volume of ice cream mix and air bubbles.
The use of Hielscher’s high-performance ultrasound processors results in a better quality of ice cream by promoting crystallization, reducing the ice crystal size and avoiding the incrustation of a freezing surface. A better consistency and a more creamy mouth feeling is achieved due to the reduced ice cream crystal size and the enhanced air bubble distribution. Significantly shorter freezing with approx. 30% reduced freezing time leads to a higher process capacity and a more energy-efficient production process.

Scientifically Proven: Improved Ice Cream Quality due to Sonication

Aslan and Dogan (2021) investigated the effects of sonication on ice cream production using the Hielscher probe-type sonicator UP400St (see pic. left). The research results demonstrated that ultrasound promotes the size reduction of particles due to cavitation. It was evident that the sonication improves the quality of ice cream and frozen food products as it produced a smaller crystal ice size. Since ice crystals give a unique mouthfeel to ice cream, it is very important to obtain the smallest crystals in the freezing process for preventing gritty structure, achieving the desired smoothness and softness of the ice cream. This study also concluded that ultrasonic homogenisation provides a well dispersed emulsion. Tested by a consumer panel for food sensory and flavour, it was shown that ultrasonic ice crem homogenization helps to fulfil consumer preferences with smaller ice crystals and the correlating pleasant mouth feel of ice cream.
(cf. Aslan and Dogan, 2021)

High Performance Ultrasonic Food Processors for Ice Cream Production

Hielscher Ultrasonics is long-experienced in the application of power ultrasound in the food & beverage industry as well as many other industrial branches. Our ultrasonic processors are equipped with easy-to-clean (clean-in-place CIP / sterilize-in-place SIP) sonotrodes and flow-cells (the wet parts).
Hielscher Ultrasonics industrial sonicators can deliver very high amplitudes in 24/7 continuous operation. The precise control of the amplitude from mild to high intensities is important to fine-tune the sonication process to the targeted product characteristics of the ice cream formulation.
With ultrasonic food processors at any size, Hielscher offers reliable systems for the batch and continuous treatment of food and beverage products, including ice cream. Whilst for a small artisanal gelatery the sonicator models UP400ST (400 watts) or UIP1000hdT (1000 watts) delivers enough processing capacity, a industrial ice cream manufacturing facility will install the high-throughput sonicator models UIP6000hdT (6000 watts) or UIP16000hdT (16,000 watts).
The table below gives you an indication of the approximate processing capacity of our ultrasonicators:

Literature / References