4 Wheat flour and other cereals White wheat flour is the largest ingredient in nearly all biscuits. It is made from wheat by removing the brown surface coating and the embryo(the bran and the germ) and reducing the particle size to a fine powder. Modern milling methods are very complex involving many stages principally because it is difficult to separate the bran from the white central part (known as the endosperm) of the wheat erdos starchy endosperm 1 Longitudinal section of wheat grain
4 Wheat flour and other cereals 4.1 Introduction White wheat flour is the largest ingredient in nearly all biscuits. It is made from wheat by removing the brown surface coating and the embryo (the bran and the germ) and reducing the particle size to a fine powder. Modern milling methods are very complex involving many stages principally because it is difficult to separate the bran from the white central part (known as the endosperm) of the wheat grain (Fig. 1). endosperm pericarp seed coats W 1 Longitudinal section of wheat grain 15
16 Biscuit, cookie and cracker manufacturing manuals Wheat varies in its quality as a result of variety, farming practice and climatic conditions. To a certain extent the flour miller can select a wheat to make a flour of desired properties but the conditions in the mill also affect the flour produced. It is possible to make satisfactory biscuits from most types of wheat flour but differences in protein content and moisture, in particular, affect the consistency of the dough so variations in flour quality are of great concern to biscuit makers. It is not yet possible to define precisely the quality components of flour required for particular biscuits and it is alse not possible for flour millers to consistently match, exactly, suggested requirements. Thus, our main aim in terms of flour quality is to have flour with consistent character from load to load throughout the year. 4.2 Wheat flour 4.2.1 Types of wheat flour The wheat endosperm is a mass of starch grains in a Upon milling this breaks down into a mixture com protein particles, individual starch grains and conglomerations of In order to achieve efficient milling the wheat moisture content must be controlled carefully. The resulting flour normally has moisture content of between 13% and 15%. An average moisture content for biscuit flour is 14% but it is almost impossible for the flour miller to control the moisture content to better than +0.5%. when a dough is made with water, both the starch and the protein absorb moisture and mechanical action in the mixer on the hydrated protein forms a viscoelastic mass, a rubbery material, known as gluten Gluten is essential for the production of leavened baked goods and this is what sets wheat flour apart from nearly all other flours. Gluten quality varies in different flours from being very extensible(it can be pull out a long way before breaking) to being very inextensible or short and also being more or less elastic(it will return to its original state after being stretched). The protein content and the quality of the gluten in flour is dependent on the type of wheat used Wheat varieties sown in the spring in hotter climates than northern Europe, tend to produce hard grains with high protein contents that give elastic but inextensible gluten. These are known as hard wheats and they produce what is termed strong flour. It is
16 Biscuit, cookie and cracker manufacturing manuals Wheat varies in its quality as a result of variety, farming practice and climatic conditions. To a certain extent the flour miller can select a wheat to make a flour of desired properties but the conditions in the mill also affect the flour produced. It is possible to make satisfactory biscuits from most types of wheat flour but differences in protein content and moisture, in particular, affect the consistency of the dough so variations in flour quality are of great concern to biscuit makers. It is not yet possible to define precisely the quality components of flour required for particular biscuits and it is also not possible for flour millers to consistently match, exactly, suggested requirements. Thus, our main aim in terms of flour quality is to have flour with consistent character from load to load throughout the year. 4.2 Wheat flour 4.2.1 Types of wheat flour The wheat endosperm is a mass of starch grains in a protein matrix. Upon milling this breaks down into a mixture composed of fine protein particles, individual starch grains and conglomerations of both. In order to achieve efficient milling the wheat moisture content must be controlled carefully. The resulting flour normally has a moisture content of between 13% and 15%. An average moisture content for biscuit flour is 14% but it is almost impossible for the flour miller to control the moisture content to better than _+OS%. When a dough is made with water, both the starch and the protein absorb moisture and mechanical action in the mixer on the hydrated protein forms a viscoelastic mass, a rubbery material, known as gluten. Gluten is essential for the production of leavened baked goods and this is what sets wheat flour apart from nearly all other flours. Gluten quality varies in different flours from being very extensible (it can be pull out a long way before breaking) to being very inextensible or short, and also being more or less elastic (it will return to its original state after being stretched). The protein content and the quality of the gluten in flour is dependent on the type of wheat used. Wheat varieties sown in the spring in hotter climates than northern Europe, tend to produce hard grains with high protein contents that give elastic but inextensible gluten. These are known as hard wheats and they produce what is termed strong flour. It is
Wheat flour and other cereals 17 ideal for bread making and is also used, in part, for fermented biscuit doughs such as crackers Conversely, wheat varieties sown in the autumn/winter, the most common varieties grown in northern Europe, tend to produce softer ains with lower protein contents. The wheat is known as soft wheat the resulting flour is much more fluffy and soft and the gluten formed from this flour is more extensible and less elastic. The flour is known as medium or weak flour. These are the flours favoured for most biscuit production. They are also less expensive as the price of flour is related to the protein content. The protein content of strong flours is usually in the range 10.5- 14.5%. Flour from winter wheat is mostly in a medium category of 8.5-10.5% but weak flours with less than 8.5% protein are found. The protein content is determined by a laboratory test that measures the amount of nitrogen present and converts this into an estimation of protein present. Assessing the quantity of pro otein ir gluten'is not a reliable method As mentioned above it is the aim of the miller to remove the bran from the endosperm during milling. There is about 82% endosperm in a wheat berry but in typical milling of a white flour only about 72- 74% of the berry can be taken as flour. Even then there are some minute bran particles in the flour. The amount of flour obtained from the wheat is known as the extraction rate. The higher the extraction rate of the flour the more bran there will be in it Bran has a protein content that cannot be hydrated and turned into gluten. This protein has a much lower value for human nutrition. Bran and the outer layers of the berry also have a mineral and fibre content higher than the main mass of the endosperm. The fibre is indigestible by humans but, particularly in recent years, it has been shown to be useful to our digestive health. The amount of bran in flour is estimated either by a test to neasure the ash (mineral) content (the ash test) or by a test to measure the reflectance of light from a water slurry made from the flour (the colour grade). The latter test is much quicker and is based on the fact that flours with more bran appear greyer. Brown flours have bran deliberately left in the flour, or more usually added back to white flour. wholemeal flour is composed of 99% of the wheat grain. In order to provide bran which is well graded it is common practice to make brown flours by adding back bran of a particular size range. Thus very large pieces or powdery particles of bran are omitted. Brown flours contain bran but no germ
Wheat flour and other cereals 17 ideal for bread making and is also used, in part, for fermented biscuit doughs such as crackers. Conversely, wheat varieties sown in the autumn/winter, the most common varieties grown in northern Europe, tend to produce softer grains with lower protein contents. The wheat is known as soft wheat the resulting flour is much more fluffy and soft and the gluten formed from this flour is more extensible and less elastic. The flour is known as medium or weak flour. These are the flours favoured for most biscuit production. They are also less expensive as the price of flour is related to the protein content. The protein content of strong flours is usually in the range 10.5- 14.5%. Flour from winter wheat is mostly in a medium category of 8.5-10.5% but weak flours with less than 8.5% protein are found. The protein content is determined by a laboratory test that measures the amount of nitrogen present and converts this into an estimation of protein present. Assessing the quantity of protein from ‘wet gluten’ is not a reliable method. As mentioned above, it is the aim of the miller to remove the bran from the endosperm during milling. There is about 82% endosperm in a wheat berry but in typical milling of a white flour only about 72- 74% of the berry can be taken as flour. Even then there are some minute bran particles in the flour. The amount of flour obtained from the wheat is known as the extraction rate. The higher the extraction rate of the flour the more bran there will be in it. Bran has a protein content that cannot be hydrated and turned into gluten. This protein has a much lower value for human nutrition. Bran and the outer layers of the berry also have a mineral and fibre content higher than the main mass of the endospenn.The fibre is indigestible by humans but, particularly in recent years, it has been shown to be useful to our digestive health. The amount of bran in flour is estimated either by a test to measure the ash (mineral) content (the ash test) or by a test to measure the reflectance of light from a water slurry made from the flour (the colour grade). The latter test is much quicker and is based on the fact that flours with more bran appear greyer. Brown flours have bran deliberately left in the flour, or more usually added back to white flour. Wholemeal flour is composed of 99% of the wheat grain. In order to provide bran which is well graded it is common practice to make brown flours by adding back bran of a particular size range. Thus very large pieces or powdery particles of bran are omitted. Brown flours contain bran but no germ
18 Biscuit, cookie and cracker manufacturing manuals There are some flours which have the germ particles returned to The germ is rich in fat and vitamins. The embryo is also rich in lipase, the fat splitting enzyme, so to ensure that the germ does not become rancid too quickly the germ is normally heat treated to destroy the enzyme before it is returned to the flour a typical germ enriched flour is Hovis. It is much more expensive than other flours but is nutritionally superi a character of flour that is of great importance to bakers is the water absorption. This is a measure of the amount of water that is needed to produce a flour and water dough of a given consistency. There are a number of factors that determine the water absorption of a flour. These include Flour moisture content; the damper the flour the less extra water is needed to make a given dough Protein content; the higher the protein the more water is required Damaged starch content. The starch in flour is present mostly as minute oval grains with a structural film around them to maintain their shape and integrity. During milling some of these grains become mechanically damaged and in this state the grains will absorb much more water than the undamaged ones. There typically much more damaged starch in flour milled from hard heat than from soft wheat. It is possible for the miller to change the amount of starch that is damaged by adjusting the ressure of the grinding but it is very difficult for him or her te increase significantly the amount of damaged starch in soft wheat flours Flour particle size distribution. The water absorption is higher in our with a fine particle size than a coarse flour just because of the surface area factor. It should be mentioned, however that it is a complicated procedure for a miller to change the particle size range of the flour he or she makes so it is normal that all the flour from a particular mill has a similar particle size range irrespective of the type of wheat milled. Thus, the mill products with which biscuit makers may be flour 10.5-14.5% protein m flour 8.5-10.5% protein flour less than 8.5% protein, wholemeal flour, 99% extraction
18 Biscuit, cookie and cracker manufacturing manuals There are some flours which have the germ particles returned to it. The germ is rich in fat and vitamins. The embryo is also rich in lipase, the fat splitting enzyme, so to ensure that the germ does not become rancid too quickly the germ is normally heat treated to destroy the enzyme before it is returned to the flour. A typical germenriched flour is ‘Hovis’. It is much more expensive than other flours but is nutritionally superior. A character of flour that is of great importance to bakers is the water absorption. This is a measure of the amount of water that is needed to produce a flour and water dough of a given consistency. There are a number of factors that determine the water absorption of a flour. These include: Flour moisture content; the damper the flour the less extra water is needed to make a given dough. Protein content; the higher the protein the more water is required. Damaged starch content. The starch in flour is present mostly as minute oval grains with a structural film around them to maintain their shape and integrity. During milling some of these grains become mechanically damaged and in this state the grains will absorb much more water than the undamaged ones. There is typically much more damaged starch in flour milled from hard wheat than from soft wheat. It is possible for the miller to change the amount of starch that is damaged by adjusting the pressure of the grinding but it is very difficult for him or her to increase significantly the amount of damaged starch in soft wheat flours. Flour particle size distribution. The water absorption is higher in flour with a fine particle size than a coarse flour just because of the surface area factor. It should be mentioned, however, that it is a complicated procedure for a miller to change the particle size range of the flour he or she makes so it is normal that all the flour from a particular mill has a similar particle size range irrespective of the type of wheat milled. Thus, the mill products with which biscuit makers may be concerned are: strong flour 10514.5% protein, medium flour 8510.5% protein, weak flour less than 8.5% protein, wholemeal flour, 99% extraction
Wheat four and other cereals 19 wheatmeal flour, more than 80% extraction but of any chosen bran, of various particle sizes, known as fine, medium or coarse germ enriched In addition, flours may be treated at the mill for special purposes Heat treated flour. Heating the flour partially or totally destroys the ability of protein to form gluten when it is hydrated and mixed. This treatment is made under controlled conditions at the mill. Use of this flour results in softer eating textures in short dough biscuits and reduces spread during baking. Heat treated flour has no value for crackers or semi-sweet biscuits but may be used, to a limited extent, as a filler in creams for sandwiched biscuits Chlorinated flour. Treatment of flour with gaseous chlorine has a at in that forming property of the protein. It also swells the starch grains and increases the water absorption character of the flour. This flour used to be widely used for cake flours in the UK. In the USa by chlorine treatment of flour the amount of spread produced during the baking of short dough biscuits and cookies is adjusted Chlorinated flour is not now used for biscuits in the uK and it is generally restricted in the EC and some other countries. Air classified flour. By a technique of centrifugal separation it is possible to collect fractions of a flour with different particle size ranges. The principal reason for this is to collect the fine particles which are rich in protein fragments. However it is also of interest to bakers because the coarser fractions have excellent free flowing properties and are good as flour for dusting dough surfaces Flour enrichment. Current UK legislation requires that all flours for human consumption are enriched. The additions are: 24g thiamine, 16g nicotinic acid, 16.5 g iron (as ferric ammonium citrate or ferrous sulphate)and 2.35-3.9 g calcium carbonate per ookg flour.(Calcium carbonate is not added to wholemeal An important aspect of this enrichment is that it is not possible etermine the bran content of uk flour by the ash test mentioned above. Most other countries in the world use this ash test as a means of categorising flour quality because they do not enrich their flour
Wheat flour and other cereals 19 wheatmeal flour, more than 80% extraction but of any chosen value, bran, of various particle sizes, known as fine, medium or coarse bran, germ enriched flours. In addition, flours may be treated at the mill for special purposes. Heat treated flour. Heating the flour partially or totally destroys the ability of protein to form gluten when it is hydrated and mixed. This treatment is made under controlled conditions at the mill. Use of this flour results in softer eating textures in short dough biscuits and reduces spread during baking. Heat treated flour has no value for crackers or semi-sweet biscuits but may be used, to a limited extent, as a filler in creams for sandwiched biscuits. Chlorinated flour. Treatment of flour with gaseous chlorine has a similar effect to heat treatment in that it destroys the gluten forming property of the protein. It also swells the starch grains and increases the water absorption character of the flour. This flour used to be widely used for cake flours in the UK. In the USA by chlorine treatment of flour the amount of spread produced during the baking of short dough biscuits and cookies is adjusted. Chlorinated flour is not now used for biscuits in the UK and it is generally restricted in the EC and some other countries. Air classified flour. By a technique of centrifugal separation it is possible to collect fractions of a flour with different particle size ranges. The principal reason for this is to collect the fine particles which are rich in protein fragments. However it is also of interest to bakers because the coarser fractions have excellent free flowing properties and are good as flour for dusting dough surfaces. Flour enrichment. Current UK legislation requires that all flours for human consumption are enriched. The additions are: 24g thiamine, 16g nicotinic acid, 16.5g iron (as ferric ammonium citrate or ferrous sulphate) and 2.35-3.9 g calcium carbonate per 1OOOkg flour. (Calcium carbonate is not added to wholemeal flour. ) An important aspect of this enrichment is that it is not possible to determine the bran content of UK flour by the ash test mentioned above. Most other countries in the world use this ash test as a means of categorising flour quality because they do not enrich their flour