Friday, September 22, 2023

High shear mixing in ketchup and mayonnaise production

Manufacturing Tomato Ketchups and Mayonnaises can be challenging, but by using the right mixing equipment the mixing process can be quick and efficient. Here Silverson Machines explains how using high shear mixers in the production line for these applications can help to improve the manufacturing process.

Tomato Ketchups

Using high shear mixing technology to manufacture ketchup can help to eliminate some of the more common problems associated with the mixing process. It can also enable manufacturers to achieve better product quality and maximised yield with shorter mixing times, and in some cases it can eliminate the need for the high pressure homogenisation step.

Diluting the tomato paste is one of the first stages of the process. This can be difficult when using conventional mixing equipment, as the more viscous paste tends to form globules that don’t readily blend with the surrounding liquid. This is known as stratification. Once these globules have formed, agitators and stirrers do not produce the shear necessary to disperse them, leaving them undiluted in the mix.

Another common problem can be encountered when thickening agents such as pectin or starch (including modified starches) are used to obtain the required viscosity in the finished ketchup. These ingredients cause problems for conventional mixers as they cannot easily disperse or hydrate them. This is because the thickening agents tend to form agglomerates when added to liquids; once these have formed the agitator does not produce the necessary shear to ‘break into’ the gelled outer surface of the agglomerate and disperse the dry powder inside. The agglomerated ingredients can remain in the mix, reducing the yield of thickening effect.

So how can using high shear mixing equipment help to solve these problems?

The answer stems from the intense shear energy created by the rotor/stator workhead. The high speed rotor draws materials into the workhead where they are intensively mixed. Centrifugal force then drives the materials to the periphery of the workhead where they are sheared in the gap between the rotor and stator, breaking up any lumps that may have formed and eliminating agglomerates from the mix. The continuous mixing cycle created by the high shear mixer progressively reduces globule or particle size and quickly results in a homogeneous, uniform product. This maximises the yield of the raw ingredients and improves the quality of the finished ketchup.

With some manufacturing processes the premixed raw materials are passed through a high pressure homogeniser. This activates the pectin found naturally in tomatoes, giving the ketchup the desired viscosity, but for it to work effectively the homogeniser must be fed with a uniform pre-mix. If undiluted or incorrectly dispersed ingredients remain in the mix or if the globule size is large or uneven, several passes through the homogeniser may be required and throughput can be low, leading to long and costly processing times.

A pre-mix created with a high shear mixer will be of a uniform, low globule size, allowing faster processing through the homogeniser and fewer passes required, a major saving in processing times.

Some formulations and manufacturing processes do not actually require high pressure homogenisation and the entire process can be completed with a high shear mixer because it is able to blend the tomato paste and hydrate and disperse the thickening ingredients to achieve the desired viscosity.


One of the most popular ‘how to’ videos released on Silverson Machines YouTube channel is on the manufacture of mayonnaise – the video currently has over 78,000 views!

Whether you are making a traditional mayonnaise, a low-fat recipe or a vegan alternative, producing mayonnaise is challenging. The mixing equipment used for the manufacturing process has a significant impact on the quality of the finished product. The challenge comes from needing a mixer that can complete several mixing processes. For example, mayonnaise is an oil-in-water emulsion, so the mixer must be able to form a stable emulsion, but it must also be able to maintain movement in the vessel during oil addition when the viscosity begins to increase. Oil addition must be controlled because if it is added too quickly this can cause the emulsion to break. In low-fat formulations where gums and thickeners such as starches are added to enhance mouthfeel, the mixer needs to incorporate and hydrate these ingredients without forming agglomerates. These tasks are beyond the capabilities of conventional mixing equipment such as agitators or stirrers.

The Silverson Mayonnaise plant can carry out the entire mayonnaise manufacturing process. This includes preparation of premixes, hydration of thickening and stabilising agents and preparation of the final oil-in-water emulsion.

Water is recirculated from the vessel through the system by the In-Line mixer, specially designed to handle high viscosity products without the need for additional pumps. The egg (either powder or liquid) is added to the vessel and is rapidly wetted out and dispersed into the high velocity liquid stream. Recirculation continues as the remaining aqueous phase ingredients are dispersed and hydrated. The Mayonnaise plant uses a separate hopper for oil addition and when the oil feed valve is opened, oil is drawn down from this hopper into the aqueous phase at a controlled rate. The aqueous and oil phase ingredients pass directly into the workhead of the In-Line mixer, where they are subjected to intense high shear. This finely disperses the oil into the aqueous phase, immediately forming an emulsion. The vinegar (and/or lemon juice) is added with the last of the oil. Recirculation of the product continues to ensure a uniform consistency as the viscosity rises. After a short recirculation period the process is completed and the finished product can be discharged.

The Mayonnaise Plant is ideal for batches of up to 100 kilos and allows users to practically eliminate operator error, offering greater batch-to-batch consistency. In addition to this unit, Silverson offers mixers for both full scale production and laboratory and pilot models for batches of up to 12 litres. Thanks to the Silverson rotor/stator mixer design, comparable results can be achieved across the product range, making scale-up a relatively straightforward process.

As well as Ketchups and Mayonnaise, Silverson High Shear mixers can also be used for the production of other sauces and dressings including Hummus, Salad Dressings and Mustards. If you’d like to find out more about any of the above applications, or watch the ‘How to’ videos, please visit:

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