Posts

Flour Treatment : Emulsifiers

Image
Due to their polar character, emulsifiers have interactions with most ingredients of wheat flour. Fig. 128 summarizes the effects of emulsifiers in baking. It has been shown that the flour's own polar lipids – mainly phospholipids (lecithin) and galactolipids already have a positive effect on the volume yield (MacRitchie and Gras, 1973).

Flour from which all lipids had been extracted only showed an improvement in volume yield when the polar lipids (or all lipids) were readded, but not with non-polar lipids (i.e. oil) alone (Fig. 129).

It is probable that all emulsifiers build complexes with gluten, as shown in Fig. 130 for lecithin. On the one hand they increase the binding forces between the protein chains, but on the other hand they act as a kind of lubricant, improving the gliding of the protein layers over each other.
Some emulsifiers with long non-polar, linear chains, such as monoglycerides, form complexes with starch, preventing the recrystallization of the gelatinized star…

Flour Treatment : Enzymes

Image
5. Transglutaminase
Transglutaminase (TG) is able to crosslink protein chains either with adjacent loops of the same protein or with other proteins of the same or a different type. It requires lysine and glutamine groups as a target. Although lysine is a limited amino acid in wheat flour, there is sufficient lysine for the action of TG to take place. The result is a strengthening effect on the dough, similar to that of AA.
Since it is much more expensive than AA, TG is little-used. Its main use is in prolonged or retarded fermentation, when the enzyme has enough time to achieve its function even at a low dosage. Bauer et al. (2003) provide more detailed information on the function of TG.
6. Other Enzymes Cellulase and β-glucanase are present as natural side activities in many enzyme preparations, e.g. xylanases. They do have some effect on the water-binding behaviour of dough, particularly from whole meal or rye flour containing larger amounts of fibrous components than standard bread …

Flour Treatment : Enzymes

Image
3. Protease Protease (also known as proteinase or peptidase) splits the protein strands of the gluten molecule (Fig. 123) and thus leads first to a softening and then to a complete collapse of the structure. Sometimes a rather surprising initial increase in viscosity or dough stability is observed. Although the causes are not clear, this may be due to improved water solubility at an early stage of hydrolysis when the main structure is still intact.
With short gluten structures a slight softening may well be desirable; in this case it has a similar significance to the use of cysteine. But unlike the amino acid, protease does not stop acting when the additive is used up. As a result, its effects increase with the fermentation time of the dough. That is why there is a considerable demand for enzyme preparations that do not contain even traces of protease. This fear may be exaggerated, at least if purified, single proteases are available: a single protease only acts on a few specific amin…

Flour Treatment : Enzymes

Image
2. Hemicellulase, Pentosanase and Xylanase Wheat flour with an ash content of about 0.5% contains about 2.5% pentosans (typical rye flour about 7%) that can bind up to ten times their weight of water. These pentosans belong to the category of the hemicelluloses, "relatives" of cellulose (Fig. 119), and are made up of different sugar molecules (including glucose, xylose and arabinose). The prevailing polymer consists of a xylose backbone with arabinose side chains (Fig. 120) and is therefore called xylan or arabinoxylan, and the enzymes accordingly xylanases or arabinoxylanases, or – less specifically – pentosanases. Approximately one third of these pentosans are soluble in water, while two thirds are larger molecules that are water-insoluble.

Xylanases break these substances down. This process initially leads to the formation of more soluble molecules from the water-insoluble pentosan, and this increases the binding of water and thus viscosity. These molecules are broken dow…

Flour Treatment : Enzymes

Image
1. Amylases
1.1. Enzyme-Active Malt Flour Like all other living material, grain needs enzymes for its vital functions. As it does not come back to life, so to speak, until germination, this is the phase when enzymes are produced in large quantities. Bakers have long put this characteristic to use by germinating cereals before processing them further.
Malt flour is the dried product made from germinated barley, wheat or rye. The functions of the three of them are largely identical. Malt flour contains primarily α- and β-amylase, but it also contains protease, glucanase and many other enzymes. Some of these may have a positive effect on the baking process (amylases and glucanases), but some can also cause damage (proteases). Like the flour's own amylases, the amylase of the malt flour has a pronounced effect on the Falling Number. If this is very high (i.e., the flour's own enzymatic activity is very low), anything up to 150 g or more of malt flour to 100 kg of flour may be neede…

Flour Treatment : Enzymes

Image
Enzymes have been in common use in the food industry for years. In contrast to most other applications in which enzymes find their way into foods, the enzymes in this case do not react at the place where they are added, namely in the mill; they do not take effect until the baker adds water. This difference in time and place is a great challenge to the flour treatment sector in general, but in the case of enzymes it is an especially complex matter. On the other hand enzymes are highly specific; that is, if they are pure enough they act on selected targets and only have to be added in small quantities. Moreover, they are entirely natural as they can only be obtained from micro-organisms by way of fermentation or from vegetable or animal tissue and fluids by means of extraction (Fig. 116).
Like all highly concentrated natural substances, enzymes have a potential for causing allergies when inhaled by workers; cases have been well documented. For this reason care must be taken during proc…

Reduction and Dough Softening

Image
2. Reducing Yeast Preparations Yeast also produces reducing substances, but these are only released when the cells die. There are now preparations made of inactivated, killed yeast on the market that have a softening effect similar to that of cysteine (Fig. 114). But as the dose required is about 100 times higher (100 - 1,000 g to 100 kg of flour), even the lower price (about 1/10 or even less) cannot make up for it. This is true even of so-called glutathione yeast, a variant with a very high reductive potential. So one might say that the main advantages of inactivated yeast are in the field of labelling.

3. Sodium Metabisulphite and Sulphur Dioxide These powerful reducing agents are especially good at breaking down the gluten fast and reliably (Fig. 115), which greatly simplifies the production of biscuits, crackers and wafers. But as these substances are known to destroy vitamin B1 (thiamine) and to cause health problems in sensitive persons, their use should be avoided. They also im…