1.4. Other ingredients
1.4.1. Salt
Salt's main function is to bring out the flavour of the baked product. Salt tends to bring out the good flavours and mask the off-flavours. Usage levels are normally between 1,8 % and 2,2 %. Legislation may vary from country to country because the intake of too much salt is considered as a health risk. In Belgium for instance the maximum allowed is 1,8 %, while in France 2,0 % is allowed. In Scandinavia one has to pay extra taxes if the salt level in the bread is higher then 1,2 %. Bread made with less then 1,6 % salt will taste insipid and bread made with more then 2,2 % will taste too salty.
In addition to impacting flavour, salt also inhibits fermentation due to the osmotic pressure effect. Yeast cells will partially dehydrate due to the osmotic pressure. This can be illustrated easily by putting some salt on fresh yeast. After a while the yeast will liquefy due to the fact that the salt will attract the water from the yeast cell. As the cell membrane is semi permeable, water will migrate from the cell and the mixture will seem to liquefy. In reality the yeast cell undergoes a change which can be compared with the change that happens to a grape when it becomes a raisin, it just dries out.
The fact that salt influences the fermentation can be used to control the fermentation : salt can be added for instance to sponges to slow down the fermentation rate. Slowing down fermentation rate means that less sugars are metabolised into acids. The result is that the pH of the dough will be higher and the crust colour will be darker. To remember that high pH gives a darker colour, one can think about a chocolate cake. Chocolate is alkaline and to get a darker, deeper colour of a chocolate cake, one must increase the pH.
Salt toughens the gluten. Weaker flours could actually be strengthened by adding salt. Salt lengthens the mixing time so it is common to delay the addition of the salt to the mixer. Faster flour hydration is also seen with delayed salt. The reason why salt toughens the gluten must be sought in the fact that gluten is made of negatively charged proteins. Negatively charged molecules will repel and not attract each other. It is believed that the positive sodium-ions Na+ of the salt play a role in bringing the protein molecules closer to each other.
Lastly, bread with no salt will also has a crust which is lighter in colour (given the same baking time and oven temperature). This can be explained as follows. Salt will slow down fermentation, so when there is no salt, the yeast activity will increase i.e. the yeast will metabolise more sugar in a given period of time. As a result there will be less sugars left in the dough and the pH of the dough will be lower (more acids will be formed). Sugars play (together with proteins, moisture and heat) an important role in the Maillard reaction. But the Maillard reaction is also influenced by the pH : a higher pH will speed up the Maillard reaction. So in this case where the pH is lower and where there are less sugars left, the colour of the crust is lighter.
1.4.2. Sugar
Sugar's main function is to provide food for the yeast. In normal bread production, 3,0 to 3,5 % fermentable solids are required to sustain yeast activity. This food supply can come from added sugar or from the enzymatic conversion of the starch to sugar or from a combination of both. Therefore sugar is not an essential ingredient.
Starch indeed belongs chemically to the group of carbohydrates : it is a long chain of glucose units and according to its structure there are two kinds :
· amylose : linear chain of glucose units
· amylopectin : branched chain of glucose units
Glucose, fructose and galactose are monosaccharides; sucrose, lactose and maltose are disaccharides. Dextrins also contain a large number of glucose units but not as much as starch.
Secondary functions of sugar are related to sugar that is not metabolised by the yeast and which is called residual sugar. As residual sugar levels are higher, crust colour is darker, taste is sweeter, and moisture retention is improved due to the hygroscopic properties of sugar.
There are many kinds of sugar used in the industry. The most common is 42 HFCS (42 high fructose corn syrup). The 42 means that 42 % of the 71 % solids found in the corn syrup is fructose. Higher numbers mean that the fructose content of the syrup is higher and hence the syrup will taste sweeter.
Different sugars also give a different sensation of sweetness. Take for instance glucose and fructose which chemically have exactly the same formula (C6H12O6) but the molecule has a different structure :
It is commonly known that fructose is about twice as sweet as glucose. The following table gives an overview of the relative sweetness of different sugars :
sugar |
sweetness |
| fructose | 140 |
| sucrose | 100 |
| 42 HFCS | 100 |
| glucose | 80 |
| maltose | 40 |
| lactose | 20 |
The main difference is however that lactose is a non-fermentable sugar : it will not be metabolised by the yeast and remain in the dough. In view of it's rather low sweetness, it will not give a sweeter product but it will influence the crust colour (Maillard reaction) and because of its hygroscopic nature delay staling.
Sugar has the same effect as salt : if too much is used, yeast activity will slow down. This effect can be seen from a 5 – 6 % sugar level. In order to compensate one can add more yeast. The sugar/yeast ratio should be 3/1. If you want to make a product that contains 15 % of sugar, the yeast level should be 5 % (baker's percentage).
Finally one should remember there are also "natural" sugars such as honey and fruit juices.
1.4.3. Fat
Fats are used in bread production to provide overall lubrication. It becomes necessary to use a small amount to facilitate slicing : 0,7 – 1,0 % will suffice to facilitate slicing.
Addition of fat helps in the handling of the dough during the make-up process. Besides lubricating the baked crumb, fat also lubricates the dough and this eases dough expansion in the proofer and in the oven. It will also tenderise the crust and improve shelf life by retarding staling.
Fats are constantly in the media with regards to health risks. Presently we have the hype around trans fatty acids. Without going into too much detail, one can divide the fats into a number of categories :
a) according to its physical state : fat or shortening is solid or semi-solid while oils are liquid at room temperature. In this context we talk about the solid fat content (SFC) which refers to the portion of solid fat at a given temperature.
b) according to its origin : vegetable fats are derived from vegetable sources only (soybeans for instance) or from animal sources such as pork (lard) or milk (butter).
c) according to its chemical structure : saturated fats (present in both animal and vegetable fats but higher in tropical oils) and unsaturated fats. In the production of margarines and fat there is a step called the "hydrogenation" and the degree of hydrogenation will affect the stability of fat and also the amount of saturated fats.
Finally cholesterol is only present in animal fats.
1.4.4. Milk solids
They primarily function as nutritional supplements. Milk is high in lysine (an essential amino acid) and calcium and the overall nutritional quality of the milk protein is excellent. European bakers prefer the use of liquid milk above the use of powder milk. Liquid milk may be less user friendly (storage, perishable), however it has the advantage that no dry matter remains in the product. Indeed, milk powder (or rather the denaturated proteins present in the milk powder) will not dissolve completely in the water and remain as dry solids in the crumb. This will give a dryer, less moist crumb. However it should be kept in mind that the milk must have been heat treated because the serum protein in milk has a weakening effect upon the gluten protein in wheat flour.
Besides improving nutritional quality, milk improves the flavour if used in a high enough amount, the dough handling and overall processing tolerance :
· deeper, more consistent crust colour
· more stable pH (milk has a buffer effect)
· strengthening of the gluten (if serum protein has been removed by high heat treatment)
1.4.5. Vital wheat gluten
Vital wheat gluten is the natural wheat protein extracted from flour which still retains all of its gluten forming characteristics. It is added to the dough to help strengthen a weak flour or to obtain additional loaf volume. A 1 % addition of wheat gluten will increase the flour protein content by 0,6 % and increase the absorption by 1,5 %. By adding wheat gluten to the recipe, mixing and fermentation times are generally increased and tolerances improve. They mainly are used in systems where the gluten network is weak or where it has to carry extra ingredients such as raisins, different types of grains, extra fibres etc.
1.4.6. Bread improvers
Bread improvers (or dough conditioners as they are called in the
a) Enzymes
First of all it should be noted that enzymes are proteins and that they are substrate specific. This means that a given enzyme only will work on a certain substrate and only do a very particular job. Secondly it should be remembered that, although they take part in a chemical (enzymatic) reaction, they do not change during that reaction. They are what we call biological catalysts that accelerate or facilitate chemical reactions.
Because they are proteins, they are heat sensitive and all enzymes have an optimum temperature and pH for activity. Within that range, activity increases with temperature until the denaturation point is reached. At that point the enzyme will lose its functionality. Apart from temperature and pH, enzymes are also dependent upon the availability of water, amount of enzyme used, the availability of the substrate and the time allowed for the reaction.
There are 3 main groups of enzymes which are commonly encountered in baking : amylases, proteases and lipoxygenases. Amylases are divided into α-amylase and β-amylase.
Amylases convert starch into sugar : the α-amylase will cleave the starch randomly (the so called 1-4 bonds in the starch) while the β-amylase can only chop off two sugar units at the time at the end of the starch chain. Normally there is enough β-amylase present in the flour but sometimes addition of α-amylase is needed. The α-amylase will cut the starch into smaller units called dextrins and the more α-amylase activity there is, the better for the β-amylase because there are more extremities available. So the substrate for the β-amylase is either starch or dextrins and the product is maltose.
Flour tends to lack α-amylase and the miller will supplement the flour with α-amylase. The diastatic activity of the flour is expressed by the falling number or the Hagberg number. A good flour has a falling number between 200 and 250 seconds. The α-amylase the miller will add can come from three different sources : cereal source (malted barley), fungal source (Aspergillius oryzae) or bacterial source (Bacillus subtilis). Bacterial amylase do denature at relatively high temperatures and some will remain in the bread after baking. The enzyme will continue to chop up starch in the baked bread. As starch is one of the main players in the staling mechanism, bacterial enzymes are used as crumb softeners because they will continue to work while the bread sits on the shelf of the supermarket. However there is a danger to it : the bread becomes softer and softer, it becomes more and more gummy and it is not uncommon that it will flatten, collapse while it sits on the shelf in case there is too much bacterial amylase left in the bread.
Malt is produced by germinating barley. During the germination the kernel will produce a lot of enzymes, mainly amylases and proteases. At a certain moment the germination process will be stopped and the enzymes will be extracted. This will lead to diastatic malt syrup i.e. a syrup which contains active enzymes. This syrup can also be dried under well controlled conditions in order to obtain malt flour. The diastatic malt is used to improve dough handling, provides more food for the yeast (as it will contain maltose), flavour, crust and crumb colour and it is a shelf life extender.
Nondiasatic malt will be treated in such a way that the enzymes will denaturate i.e. the temperatures used will be high enough to deactivate the enzymes. This product is a syrup containing about 60 % of maltose. It will aid in the fermentation of the dough, contribute to crust and crumb colour and improve the flavour of the bread.
Fungal amylases work in exactly the same way bacterial and cereal amylases work. They however are denaturated at lower temperatures.
Protease will react with proteins and weaken them. As a result mixing time will be reduced, machinability will be improved as well as pan flow (the dough will fill more easily the shape of the pan). These effects are accomplished by breaking the long protein chains, cutting peptide bonds, into smaller units.
Finally also lipoxygenase is used in the bakery which is found in soy flour. This enzyme will bleach the flour. Flour contains a yellowish pigment that will be broken down by lipoxygenase. As a result one will obtain a whiter crumb.
b) Oxidising agents
Oxidising agents are used by the baker to improve dough strength. Due to the oxidising action SH-groups in the gluten network will be transformed into –S-S- bonds between the protein chains rendering a stronger gluten network. They will improve dough handling for better machining and contribute to improved gas retention, giving better volume and a more regular grain of the crumb. Some oxidants are fast acting, working in the mixer and early make-up stage. Bromates, which are cancerogenous and which are only allowed in the
One oxidant with which good results were obtained in the
Calcium peroxide is an oxidant but is used for its dough drying capabilities. It tends to take away the stickiness without stiffening the dough. It reacts immediately on contact with water.
The most widely used oxidising agent is ascorbic acid or vitamin C. No need to say it is safe to use. However one needs oxygen to be present because ascorbic acid as such is a reducing agent. In the presence of oxygen however it will become dehydroxyascorbic acid and it is actually the dehydroxyascorbic acid reacting as an oxidising agent.
c) Reducing agents
Reducing agents are used to weaken the protein and have the same effect as proteases. The difference being however that the proteases will be destructed by the high temperatures in the oven while reducing agents will remain in tact of course. Reducing agents will reduce mixing time and improve dough machinability i.e. moulding will be facilitated. Reducing agents break bonds between the proteins during mixing. They have the opposite effect of oxidising agents. The most commonly used reducing agent is L-cysteine.
1.4.7. Emulsifiers
