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I'm stung by the oats

Drastically reducing process time in the production of plant-based milk alternatives

Dispersing and mixing technology specialist ystral has implemented two process plants for a manufacturer of oat drinks. These fully break down plant-based proteins. At the same time, starches are broken down to the required extent and agglomerates and foam are avoided. The process time has been significantly reduced compared to conventional mixing processes.

The Conti-TDS machine directs liquid and powder on separate paths into the wetting zone With the Conti-TDS, even hard-to-wet, dusty or sticky powders containing protein can be dispersed agglomerate-free

Plant-based milk alternatives have long since made it from a niche product in organic food stores to the permanent range of discount stores and the range of vegan substitute products is wide: in addition to oat, soy, rice, coconut or almond drinks, milk alternatives based on peas, lentils, adzuki, fava, cashews or peanuts can also be found on the shelves with increasing frequency. The term "milk" may no longer be officially used for these drinks since 2017. If protein powders from seeds, grains, nuts or pulses are incorporated into water, they tend to gelatinize, stick together and foam. It is crucial that any agglomerates present in the powder are completely broken up as soon as they enter the water and that the formation of new agglomerates is avoided from the outset. Otherwise, these agglomerates have to be broken down later by prolonged stirring and time-consuming post-dispersion - with negative consequences for the product quality, as this destroys protein structures that have already unfolded.

Avoiding agglomerates is also very important with regard to the starch contained in the powder. Starch is usually broken down by enzymes, occasionally also by acids. If the powder particles are already separated before the liquid is introduced and strongly dispersed during the powder application, the enzymatic degradation of the starch is supported and thus accelerated.

With conventional agitators, injectors or inline blenders, however, the particles always come into contact with the liquid as a compact bulk. This leads to stable, partially wetted agglomerates that are difficult to break down. Post-dispersion then not only costs a lot of time and energy, but the air contained in the protein powder is also dispersed to form unwanted microfoam. Foam and agglomerates cause problems in the heat exchanger. A large proportion of the insufficiently digested proteins are ultimately filtered off unused.

Vacuum expansion separates the powder particles

In contrast to these conventional mixing processes, the Conti-TDS inline dispersing machine from ystral uses the principle of vacuum expansion to separate the powder particles: the air contained in the powder is expanded many times over, which greatly increases the distances between the particles. In the Conti-TDS, powder and liquid only come into contact with each other in the wetting chamber - under maximum vacuum and maximum turbulence. In the dispersing zone, the powder particles have the greatest possible distance from each other and can therefore be completely wetted and dispersed individually.

Due to the intensive dispersion, significantly fewer enzymes are required to break down the starch compared to conventional processes. The air previously contained in the powder is separated from the much heavier dispersion by the centrifugal effect of the high-speed rotor and coalesces into large air bubbles that can easily escape in the process vessel. In this way, the foam that normally occurs during protein processing is almost completely avoided.

Highly concentrated premixing shortens the process time

ystral's mixing and dispersing machines offer a wide range of process options for powder processing. For example, allergenic and non-allergenic powders can be sucked in via completely separate routes and processed in separate liquid circuits. A Conti-TDS can be easily integrated into existing process systems and piped with several process containers or storage tanks. The disperser can also be operated either inline or in a circuit on large process vessels. Or it can produce a highly concentrated premix in a small batch, which is then diluted in the main process tanks.

The latter option is used by a manufacturer of oat drinks, for whom ystral has implemented two complete process systems. The powders are fed via a total of three bag feeders and two big bag stations. A highly concentrated powder dispersion is produced in a small process tank with a capacity of 6,500 l using the ystral Conti-TDS connected to the circuit. This takes around 15 minutes. This solution is then pumped into a 60,000 l main process tank while it is still being filled with water.

A YSTRAL Jetstream Mixer is installed in both the small and large process tanks, which permanently mixes the entire contents of the tank homogeneously. This means that the entire mixing process is already complete when the large process tank is completely filled. The user wanted to reduce the process time for powder application and dispersion from two hours to one hour. In fact, the process is now already complete.

Adapting processes specifically

Depending on the powder type, there are some special features to consider. Dispersing with an inline Conti-TDS is sufficient for processing oatmeal - as well as soy or rice. Other protein-containing powders - such as coconut or some pea flours - require additional dispersion under high shear in order to fully break down the product. In these cases, ystral uses a Z-Inline disperser in addition to the Conti-TDS, which post-disperses the protein powder while the Conti-TDS simultaneously adds the entire powder. The Z-Inline disperser can be operated either in parallel in a separate circuit or in series with the Conti-TDS.

The system can easily be expanded, as the concentrate production can be operated with any number of large process containers.

Article preview "Mich sticht der Hafer"

Magazine: Process engineering
Issue: 04/2022
Author: Dr. Hans-Joachim Jacob

About the author

Dr. Jacob is Senior Expert Process and Applications at ystral. Dr. Jacob, who studied mechanical engineering, joined the company in 1990 as a process engineer and has since been responsible for our key accounts worldwide. His professional passion is the mixing and dispersion of powders in liquids. During his long career, he has gained experience in handling thousands of powders from a wide range of industries and is happy to share his expertise in various technical articles, online seminars and lectures.

About ystral

With our vast knowledge and many years of experience in Process- and Application Engineering we offer targeted, customer-oriented solutions across industries - from lab equipment to production machines or plants. Together with you, we develop concepts and implementations for your individual applications, which mean mmediately realisable and quantifiable added value for you.

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