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018-Flour Treatment 20.10.2006 13:54 Uhr Seite 243 18.8 Bleaching Agents
tein structure, and this helps to counteract the negative effects of excessive enzyme acti- Arabian-style flat bread and baguettes to sli- vity (e.g. water release). The most suitable ced bread for toast. The flavonoids responsi- preparations are those that stabilize the pH at ble for the colour can be bleached with oxidi- the level to which it has been adjusted, i.e.
so-called buffer substances, mixtures of diffe-rent salts or acids. In most cases the dosage 18.8.1 Benzoyl Peroxide
is in the range of about 50 to 200 g to 100 kg For a long time, benzoyl peroxide was a fami- 81 of flour. Fig. 136 shows the effect of an alkali- liar oxidative bleaching agent and it is still ne buffer agent on the Falling Number and on used to this day in many countries. In addition 82 to its good bleaching effect it has a slight Nevertheless, with the inorganic phosphates influence on the structure of the gluten, but and carbonates care has to be taken not to this is not apparent when other flour impro- exceed the limits of the flour grades, as these substances pass into the ash. With sprouted The dosage for benzoyl peroxide is about 5 - 148 grain it is in any case advisable, whatever the 10 g to 100 kg of flour (50 - 100 ppm) into the treatment, to use a smaller proportion of the flour stream. It is usually sold as a 27 - 32% enzyme-rich outer layers of the grain (reduce product (to enable safe transportation it is the yield) and produce lighter-coloured flours diluted with an inert carrier), and the dose is that then tolerate the addition of flour impro- then correspondingly higher. The effect of benzoyl peroxide on the flour is already visi-ble after 6 hours of storage and complete 18.8 Bleaching Agents
decomposes to benzoic acid (Fig. 132), a sub- Although there is an awareness of the impor- stance found in various fruits and berries and used as a food preservative, e.g. in cream and there is still a demand for a very light-colou- fruit fillings for pastry at dosages of 0.05 - red crumb in many wheat products. This is Fig. 132: Decomposition of benzoyl peroxide 018-Flour Treatment 20.10.2006 13:54 Uhr Seite 244 18.9 Vital Wheat Gluten
18.8.2 Enzyme-Active Bean Flour
18.8.3 Other Agents with a Bleaching Effect
and Soy Flour
The brightening effect noticed when ascorbic Enzyme-active flour made from soy or horse- acid, emulsifiers or some enzymes are used 83 beans can also be used to achieve a light- has a physical cause; the finer texture changes the reflecting properties of the crumb and the used is limited by the formation of an undes- colour appears lighter (smaller holes have irable bitter taste. For this reason the maximum smaller shadows). On the other hand strong quantities used are usually 0.5% for soy flour oxidizing agents such as bromate or chlorine and 2% for horsebean flour. Another legume really do remove the colour from the dark from which flour with a bleaching effect is pro- pigments, although this is only a desirable duced is lupin seed. But again, the efficacy is As already mentioned in the section "steamedbread", lipase also has a bleaching effect The classic application of soy flour is doubtless French baguettes, in which it is increasingly to convert the liberated unsaturated fatty replacing the less effective bean flour. A acids – with the help of flour lipoxygenase – typical dose of 0.3% already has a definite bleaching effect. It is used at about the same concentration in flours for toast and flatbread. Soy, horsebean and lupin seed flour 18.9 Vital Wheat Gluten
only become active after the addition ofwater; they do not bleach the flour in its dry To describe all the aspects of gluten and its production would fill a separate book, so thissection will concentrate on the issues relatingto flour improvement. Information on therheological properties of gluten is also given in chapter 14. But like many other articles,chapter 14 only deals with native gluten, i.e.
as it is extracted from wheat flour. If wheat gluten is to be used commercially as an additive,it first has to be extracted from wheat and converted into powder. This is a multiple-step process (Fig. 133), starting with the milling ofthe wheat grains. Milling is followed by aqueous separation of the starch and solublesubstances from the aggregated gluten, disintegration of the gluten in a pin mill or the like and finally hot air drying, for example in a Only about 82% of the protein of flour is inso- luble in water and contributes to wet glutenformation. Furthermore, some of the water-soluble proteins are trapped by the insoluble proteins. But wet gluten is not just water andprotein; it also contains about 5 - 10% lipids (d.b.) and a significant amount of non-starchcarbohydrates (Pomeranz, 1988).
Fig. 133: Gluten extraction by the Martin process It is clear that the functionality of extracted

Source: http://www.muehlenchemie.de/downloads-future-of-flour/FoF_Kap_18-8.pdf