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Non-Dairy: Powder processing during production of plant-based alternatives to milk
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Thursday, 04 August, 2022, 16 : 00 PM [IST]
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Dr Hans-Joachim Jacob
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The market for plant-based lactose-free alternatives to milk is booming. The most important raw material always is a ground seed meal in powder form. However, processing of these powders poses a challenge: In order to ensure optimum product quality, the vegetable proteins contained must be fully unlocked, starches must be degraded to the required degree, and agglomerates and foam must be avoided. For a manufacturer of oat drinks, ystral, the mixing and dispersion technology specialist realised two process systems, which meet all of these requirements, while significantly reducing the process time compared to conventional mixing processes at the same time.
Plant-based alternatives to milk have long ceased to be just a niche product in the health food store, and entered the permanent product range of discount stores – the range of vegan alternative products is huge: In addition to oat, soy, rice, coconut or almond drinks, one can increasingly also find alternatives to milk based on for example peas, lentils, adzuki beans, fava, cashews or peanuts on the shelves. Since 2017, the term “milk” must no longer be used officially for these drinks, however, consumers stick to terms such as “almond milk” or “soy milk”, as their properties and use are similar to that of milk. In addition to milk drinks, plant-based proteins are also used for a large number of other products: From plant-based ice cream and desserts up to whipping cream, coffee whitener or spread.
Prevention of agglomerates is crucial
If protein powders of seeds, grains, nuts and pulses are mixed into water, they are prone to clogging, agglutinating and foaming. What is crucial is that agglomerates that are contained in powders are instantly ground when mixed into water, and the formation of agglomerates is prevented from the outset. Otherwise, these agglomerates must be broken down subsequently through long stirring and time-consuming redispersion – with negative consequences for the product quality, as protein structures that have already developed are being destroyed this way.
Equally, with regard to the starch contained in the powder, the prevention of agglomerates is also very important. The degradation of starch usually occurs through enzymes, occasionally also through acids. If powder particles are already separated before the infeed of liquid, and highly dispersed during powder induction, the enzymatic degradation of the starch is supported and thus accelerated.
In case of conventional agitators, injectors or in-line blenders, however, the particles always come into contact with the liquid as compact discharge. This leads to sturdy, partially wetted agglomerates, which are difficult to break down. Redispersion then not only costs considerable amounts of time and energy, but the air, which is contained in the protein powder, is also dispersed to form undesired micro foam this way. Foam and agglomerates cause problems inside the heat exchanger. A large part of the proteins that were not fully unlocked is filtered out unused at the end.
Separation of powder particles through vacuum expansion
In contrast to these conventional mixing processes, the Conti-TDS inline dispersing machine from ystral uses the principle of vacuum expansion for separation: Here, the air contained in the powder is expanded by a multiple, which significantly enlarges the distance between the particles. Powder and liquid in the Conti-TDS only come into contact with each other in the wetting chamber – under maximum vacuum and maximum turbulence. The powder particles have the largest possible distance to each other in the dispersing zone, and can thus be fully wetted and dispersed individually.
Through this intensive dispersion, significantly less enzymes are needed for the degradation of starch compared to conventional procedures. The air, which was previously contained in the powder, is separated from the significantly heavier dispersion through the centrifugal effect of the fast running rotor and coalesces to large air bubbles, which can easily escape in the process vessel. Foam, which is usually generated through protein processing, is almost completely prevented this way.
Reduction of process time through highly concentrated premixing
The process options for powder processing are highly diverse with the mixing and dispersing machines from ystral. For example, allergenic and non-allergenic powders can be absorbed completely separately and processed in separate liquid circuits. A Conti-TDS can be easily integrated into existing process systems and be piped with several process vessels or storage tanks. Furthermore, the disperser can either be operated inline or in the circuit on large process vessels, or generate a highly concentrated premix in a small batch, which is subsequently diluted in the main process vessels.
The latter option is used by a manufacturer of “oat milk”, for whom ystral has realised two complete process systems. The powder is fed via a total of three bags in feeds and two big bag stations. Highly concentrated powder dispersion is produced in a small process vessel with a capacity of just 6,500 litres with the YSTRAL Conti-TDS connected in the circuit. This takes approx. 15 minutes. This solution is then pumped into a main process vessel holding 60,000 litres, whilst it is still being filled with water. An YSTRAL Jet stream Mixer is installed in the small as well as large process vessel, which homogeneously mixes the entire content in the vessel. This means the entire mixing process is already completed once the large process vessel is completely filled. The user wanted to reduce the process time starting at this point for the powder induction and dispersion from two hours to one hour. In actual fact, the process is now already completed.
Depending on the powder type, some particularities must be observed. For processing oatmeal, just like soy or rice, dispersion with an inline operated Conti-TDS is sufficient. Other protein-rich powders, such as coconut or some pea flour, require additional dispersion under high shearing, in order to fully unlock the product. In these cases, in addition to the Conti-TDS, ystral uses a Z-Inline Disperser, which redisperses the protein powder, while the entire powder is induced at the same time via the Conti-TDS. The Z-Inline Disperser can be operated here either in parallel in a separate circuit, or in series with the Conti-TDS.
The system can be easily extended, as the concentrate can be produced with any number of large process vessels.
(The author belongs to Ystral)
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