This website uses cookies primarily for visitor analytics. Certain pages will ask you to fill in contact details to receive additional information. On these pages you have the option of having the site log your details for future visits. Indicating you want the site to remember your details will place a cookie on your device. To view our full cookie policy, please click here. You can also view it at any time by going to our Contact Us page.

Close

Ketchup on high shear mixing benefits

22 January 2021

High shear rotor/stator mixers are widely used in the manufacture of sauces such as salad cream and mayonnaise. Eli Gasgil argues that they also have a vital role in the manufacture of 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 result in better product quality and maximised yield with shorter mixing times. Further, in some cases it can eliminate the need for the high pressure homogenisation step.

The first step in the ketchup manufacturing process is to diluting the tomato paste. This can be difficult using conventional mixing equipment because this viscous paste tends to form globules that do not 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 which are used to obtain the required viscosity in the finished ketchup. These ingredients can cause problems for conventional mixers as they cannot be easily dispersed or hydrated. 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 to disperse the dry powder inside. This means that the agglomerated ingredients can remain in the mix, reducing the yield of thickening effect.

Solving problems
So, how can the use of 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 as it is able to blend the tomato paste and hydrate and disperse the thickening ingredients to achieve the desired viscosity.

As high shear mixers are able to produce mixes of homogeneous particle size they can also be used for other applications which rely on stable emulsions in the final product, for example mayonnaise, hummus and salad dressings.

Eli Gasgil is food technology manager at Silverson Machines.


Contact Details and Archive...

Print this page | E-mail this page