Pre-blending

Pre blending and processing

The preprocessing of raw materials serves several functions, namely: weighing, preblending raw materials, premixing types of flour, combining small ingredients, and bringing basic raw materials into a workable form, such as grinding granulated sugar into powder, roasting nuts, crystallizing fat, processing crumbs, etc.

The premixing of types of flour is carried out in many bakeries equipped with silos for basic flour and types of flour. For instance, a bread factory with flour for white bread and whole meal for whole wheat bread can create mixtures, like a 50:50 blend, to bake wheat bread. A pastry or biscuit factory producing multiple types of products can easily start with two basic types of flour: one with higher protein content, or a 'stiffer' flour, and one with lower protein content, or a 'softer' flour.

By blending mixtures of these two extremes, many product requirements can be met. It is also convenient to make minor adjustments by varying with one of them. For pastry products that should not spread or expand much, a higher proportion of 'stiff' flour is needed, e.g., for vanilla batons. At the other specturm we have products that require good spreading, like spiced biscuit, 'stiff' flour is often undesirable. The influence of flour quality also depends on the proportions of other major ingredients such as fat, sugar, and liquid. 

Mixing two types of flour or flour and whole meal can be done in several ways. One way is to weigh both types separately and feed them into the mixing machine, where they need to be mixed and/ or kneaded thoroughly. This is not a problem for bread dough, which uses a lot of water and is mixed and kneaded intensively with the flour, or for most biscuit doughs with a relatively long mixing time. However, for pastry dough and batters with a much shorter mixing time with flour, there are disadvantages to this system because the chance of inhomogeneity is 'high'.

Another method is to pour both types into a premixer after weighing, where they can be mixed with a simple stirrer or another mixing system before being sent to the main mixer.

A third approach involves allowing both types to flow simultaneously into the correct ratio into a small silo above the scale. Afterwards, they are weighed and fed into the mixing machine. The drawback of this system is that it's challenging to precisely regulate the flow rates of both flour streams.

Another option is to use small intermediate silos where a day's supply of blended flour or meal is prepared. If these intermediate silos have self-weighing capabilities, you can introduce the flour types one by one by weight, then mix them, and use this blend for weighing and feeding into the dough machine. Another alternative is to have certain types pre-mixed at the flour mill and delivered as a blend. This system requires multiple silos.

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