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
20 Biscuit, cookie and cracker manufacturing manuals 4.2.2 Uses and functions of wheat flours for biscuits Fermented doughs for cream crackers and soda crackers use medium to strong flour to produce a dough capable of producing a good open texture during baking Puff doughs also use medium to strong flour for the same reason Savoury crackers require a medium strength flour for their texture Semi-sweet types require only a medium or weak strength flour referably with an extensible and not very elastic gluten quality lowever, the gluten quality can be modified, to a certain extent, chemically during mixing(see Sections 10 and 12.7). Flour high in protein will tend to give harder eating biscuits and cause difficulties hort doughs are not as specific in their flour requirements There is little water in the dough so only a little gluten development occurs. The mixing technique is designed to ensure that minimum gluten forms as the protein in the flour hydrates Wafers require medium to low protein flours. If the protein is too high or too strong there will be a tendency to bake hard wafers and if too low the wafers may be very fragile. Several types of biscuit require brown flours. The basic strength of the flour is as stated above but there are significant levels of bran in the flour. Biscuits made with brown flours do not develop to the same thickness during baking as do similar recipes with white flour. This is because the bran particles interrupt the structure and impair the formation of fine gas bubbles that are the basis of the structural Brown flours are less satisfactory to handle in bulk, so it is common practice to add an appropriate quantity of bran to white flour as a separate ingredient In this way the majority of the flour can be bulk handled and the bran that is added can be of the desired particle size. 4.2.3 Common dough and baking problems related to flour uality Changes in flour quality will probably first be noticed in the dough consistency. The dough will be tighter or softer than expected due to change in water absorption properties. The main reasons for changes in water absorption are changes in flour moisture or protein content
20 Biscuit, cookie and cracker manufacturing manuals 4.2.2 Fermented doughs for cream crackers and soda crackers use medium to strong flour to produce a dough capable of producing a good open texture during baking. Puff doughs also use medium to strong flour for the same reason. Savoury crackers require a medium strength flour for their texture. Semi-sweet types require only a medium or weak strength flour preferably with an extensible and not very elastic gluten quality. However, the gluten quality can be modified, to a certain extent, chemically during mixing (see Sections 10 and 12.7). Flour high in protein will tend to give harder eating biscuits and cause difficulties in maintaining good biscuit shape. Short doughs are not as specific in their flour requirements. There is little water in the dough so only a little gluten development occurs. The mixing technique is designed to ensure that minimum gluten forms as the protein in the flour hydrates. Wafers require medium to low protein flours. If the protein is too high or too strong there will be a tendency to bake hard wafers and if too low the wafers may be very fragile. Several types of biscuit require brown flours. The basic strength of the flour is as stated above but there are significant levels of bran in the flour. Biscuits made with brown flours do not develop to the same thickness during baking as do similar recipes with white flour. This is because the bran particles interrupt the structure and impair the formation of fine gas bubbles that are the basis of the structural development. Brown flours are less satisfactory to handle in bulk, so it is common practice to add an appropriate quantity of bran to white flour as a separate ingredient. In this way the majority of the flour can be bulk handled and the bran that is added can be of the desired particle size. Uses and functions of wheat flours for biscuits 4.2.3 quality Changes in flour quality will probably first be noticed in the dough consistency. The dough will be tighter or softer than expected due to a change in water absorption properties. The main reasons for changes in water absorption are changes in flour moisture or protein content. Common dough and baking problems related to flour
Wheat flour and other cereals 2 Changes in the shape and hardness of many types of biscuits can be due to variations in the flour protein content and the gluten quality. However, these can also happen as a result of changes in the processing, including the baking To distinguish whether the flour or the processing is responsible the circumstances under which the faul should be reviewed. Flour will normally be used from a large consignment and it is unlikely that it will vary within that consignment. In other words, if the observed fault is transient or regular it is unlikely that flour is the main cause. However, if the fault has coincided with the change to a new consignment of flour and it has been established that the dough consistency is correct, then the problem may lie with the flour. s flour empties from a silo it often cores down the centre, meaning that the flour put in first does not come out of the silo first Flour variation can occur if a new delivery of different quality is placed into a silo that is not empty. The following are some of the principle flour related problems encountered in biscuit making. Some brief suggestions are given to overcome them but the subject is referred to again in Manual 2, biscuit doughs Fermented cracker biscuits- changes in shape, thickness and eating hardness after baking can be caused by changes in the flour protein quantity and quality. The problem may be complex but attempts to remedy it should be made by adjusting the fermentation time or adjusting the blend of flour if more than one type is used in the recipe. Semi-sweet biscuits- dimensional changes related to more or less shrinkage after cutting and during baking may be flour elated. Correction is normally possible in the first instance by attempting adjustment of the dough relaxation before cutting. If this is not enough the level of sodium metabisulphite(SMS)in the formulation should be adjusted. If the flour is still too elastic inclusion of some starch to dilute the flour may be tried a rough dough surface prior to cutting and a thin biscuit after baking suggests that the flour protein is not extensible enough to allow good sheeting. Check the dough temperature and try increasing the dough water content. Failing this, try increasing the level of SMS in the recipe Short dough biscuits- flour quality affects the spread and
Wheat flour and other cereals 21 Changes in the shape and hardness of many types of biscuits can be due to variations in the flour protein content and the gluten quality. However, these can also happen as a result of changes in the processing, including the baking. To distinguish whether the flour or the processing is responsible, the circumstances under which the fault or problem has occurred should be reviewed. Flour will normally be used from a large consignment and it is unlikely that it will vary within that consignment. In other words, if the observed fault is transient or irregular it is unlikely that flour is the main cause. However, if the fault has coincided with the change to a new consignment of flour and it has been established that the dough consistency is correct, then the problem may lie with the flour. As flour empties from a silo it often cores down the centre, meaning that the flour put in first does not come out of the silo first. Flour variation can occur if a new delivery of different quality is placed into a silo that is not empty. The following are some of the principle flour related problems encountered in biscuit making. Some brief suggestions are given to overcome them but the subject is referred to again in Manual 2, Biscuit doughs: Fermented cracker biscuits - changes in shape, thickness and eating hardness after baking can be caused by changes in the flour protein quantity and quality. The problem may be complex but attempts to remedy it should be made by adjusting the fermentation time or adjusting the blend of flour if more than one type is used in the recipe. Semi-sweet biscuits - dimensional changes related to more or less shrinkage after cutting and during baking may be flour related. Correction is normally possible in the first instance by attempting adjustment of the dough relaxation before cutting. If this is not enough the level of sodium metabisulphite (SMS) in the formulation should be adjusted. If the flour is still too elastic inclusion of some starch to dilute the flour may be tried. A rough dough surface prior to cutting and a thin biscuit after baking suggests that the flour protein is not extensible enough to allow good sheeting. Check the dough temperature and try increasing the dough water content. Failing this, try increasing the level of SMS in the recipe. Short dough biscuits - flour quality affects the spread and
22 Biscuit, cookie and cracker manufacturing manuals associated thickness of the dough during baking, particularly on steel oven bands. Flours with higher water absorption characters such as heat treated flour, reduce spread. Other ways of adjusting the spread of short doughs are discussed in Manual 4 Baking and cooling of biscuits Wafers- batter for wafers may become stringy during mixing due to the formation of gluten strands These will block sieves and depositor nozzles if not removed or prevented. Try using very cold water for the batter mix to delay the gluten formation until the flour is completely dispersed in the water. If the flour protein content is high at the desired weight after baking, the wafers will tend to be hard eating and conversely if the protein is very low the wafers will be very soft and fragile 4.2.4 Delivery and quality testing of flour Flour is delivered either in multiwalled paper bags (usually 32 or 50kg gross weight) or in reusable sacks of hessian or plastic weave or in bulk tankers. The tankers are filled by gravity at the mill and are unloaded at the biscuit factory pneumatically. This means that air is blown through a pipe from a pump(either land based at the factory or driven by the tanker motor) to the top of the flour silo. The flour is extracted from the tanker by being dropped into the air stream The flour is separated from the air in the silo by gravity and filtration. The filters are mechanically shaken periodically to let material trapped fall back into the silo The moisture content of the flour will be affected slightly by the pneumatic handling because the blown air from the pump will b warm and there is a large volume of air relative to the mass of the flour being conveyed. Flour should be tested before it is used in the factory to check that it is of the specification required. In the case of bagged flour the test can be made at any time between delivery and use For bulk flour it is best to make the check before the tanker is discharged because it is very difficult to return the flour to the supplier if it is later found to wrong! Therefore, before the tanker discharges, a good sized sample should be taken from the top of the load. Enough flour should be taken for any tests that may be required and some should be kept as a reference in the laboratory until it is certain that all of that delivery has been used in the factory. The principal reason for
22 Biscuit, cookie and cracker manufacturing manuals associated thickness of the dough during baking, particularly on steel oven bands. Flours with higher water absorption characters, such as heat treated flour, reduce spread. Other ways and means of adjusting the spread of short doughs are discussed in Manual 4, Baking and cooling of biscuits. Wafers - batter for wafers may become stringy during mixing due to the formation of gluten strands. These will block sieves and depositor nozzles if not removed or prevented. Try using very cold water for the batter mix to delay the gluten formation until the flour is completely dispersed in the water. If the flour protein content is high at the desired weight after baking, the wafers will tend to be hard eating and conversely if the protein is very low the wafers will be very soft and fragile. 4.2.4 Delivery and quality testing of flour Flour is delivered either in multiwalled paper bags (usually 32 or 50 kg gross weight) or in reusable sacks of hessian or plastic weave or in bulk tankers. The tankers are filled by gravity at the mill and are unloaded at the biscuit factory pneumatically. This means that air is blown through a pipe from a pump (either land based at the factory or driven by the tanker motor) to the top of the flour silo. The flour is extracted from the tanker by being dropped into the air stream. The flour is separated from the air in the silo by gravity and filtration. The filters are mechanically shaken periodically to let material trapped fall back into the silo. The moisture content of the flour will be affected slightly by the pneumatic handling because the blown air from the pump will be warm and there is a large volume of air relative to the mass of the flour being conveyed. Flour should be tested before it is used in the factory to check that it is of the specification required. In the case of bagged flour the test can be made at any time between delivery and use. For bulk flour it is best to make the check before the tanker is discharged because it is very difficult to return the flour to the supplier if it is later found to be wrong! Therefore, before the tanker discharges, a good sized sample should be taken from the top of the load. Enough flour should be taken for any tests that may be required and some should be kept as a reference in the laboratory until it is certain that all of that delivery has been used in the factory. The principal reason for
Wheat flour and other cereals 23 the tests is to see that the flour is as expected and is similar to the last load. a quick and simple test is the Pekar test which shows the general colour of the flour and the amount of bran specks in it. The Pekar test is made against a reference sample and it is recommended that the reference be a previous flour sample that was satisfactorily used in the factory. also check the documentation that accompanies the load. It is just possible that the driver has brought a load of bread flour by mistake The laboratory may also have a rapid test method for protein content. If the quality checks suggest that the flour is apparently satisfactory the discharge of the flour can commence. More detailed and longer tests for flour are outside the scope of this manual Try to put the flour into an empty silo or at least into one that is ery nearly empty. Blending of two flours in an uncontrolled manner may cause difficulties in the baker 4.2.5 Storage of our Flour is normally at about 14%moisture. It is thus prone to mould growth and infestation by insects and larger animals. Flour ag es after milling and the effect of the aging is to make the gluten a little stronger, that is less extensible and more elastic, both conditions that are less desirable for most biscuits. old flour may also become rancid nd therefore taste unpleasant. Flour should be stored in cool dry conditions, used strictly in stock rotation and kept for minimum periods. a careful watch should be made to prevent infestation by insects, rodents or birds. Flour can easily pick up taints so storage of bags and sacks should be well away from strong smelling materials such as spices and detergents efore leaving the mill, most flour is passed through a machine known as an entoleter. This flings the flour vigorously against a hard surface and effectively breaks any insect eggs which may have been picked up from places in the mill. The treatment is good but never 100% successful. There is therefore a potential for the growth of insects from eggs retained in the flour. The most likely insect is the Mediterranean flour moth If this moth or other insects are observe in the flour store a fumigation programme should be used to destroy them and the caterpillars Fortunately, insect infestation is unusual in silos where there is frequently a strong movement of Insect infestation particular problem with brown flours and bran because these
Wheat flour and other cereal8 23 the tests is to see that the flour is as expected and is similar to the last load. A quick and simple test is the Pekar test which shows the general colour of the flour and the amount of bran specks in it. The Pekar test is made against a reference sample and it is recommended that the reference be a previous flour sample that was satisfactorily used in the factory. Also check the documentation that accompanies the load. It is just possible that the driver has brought a load of bread flour by mistake! The laboratory may also have a rapid test method for protein content. If the quality checks suggest that the flour is apparently satisfactory the discharge of the flour can commence. More detailed and longer tests for flour are outside the scope of this manual. Try to put the flour into an empty silo or at least into one that is very nearly empty. Blending of two flours in an uncontrolled manner may cause difficulties in the bakery. 4.2.5 Storage of flour Flour is normally at about 14% moisture. It is thus prone to mould growth and infestation by insects and larger animals. Flour ages after milling and the effect of the aging is to make the gluten a little stronger, that is less extensible and more elastic, both conditions that are less desirable for most biscuits. Old flour may also become rancid and therefore taste unpleasant. Flour should be stored in cool dry conditions, used strictly in stock rotation and kept for minimum periods. A careful watch should be made to prevent infestation by insects, rodents or birds. Flour can easily pick up taints so storage of bags and sacks should be well away from strong smelling materials such as spices and detergents. Before leaving the mill, most flour is passed through a machine known as an entoleter. This flings the flour vigorously against a hard surface and effectively breaks any insect eggs which may have been picked up from places in the mill. The treatment is good but never 100% successful. There is therefore a potential for the growth of insects from eggs retained in the flour. The most likely insect is the Mediterranean flour moth. If this moth or other insects are observed in the flour store a fumigation programme should be used to destroy them and the caterpillars. Fortunately, insect infestation is unusual in silos where there is frequently a strong movement of air. Insect infestation is a particular problem with brown flours and bran because these
24 Biscuit, cookie and cracker manufacturing manuals cannot be treated by the entoleter as the particle sizes would be eriously affected It is therefore important not to store these flour for long before use Flour silos should be insulated to reduce temperature fluctuations due to weather conditions. If the walls are allowed to cycle strongly in temperature, migration of moisture within the flour may cause lumping and adhesion to the silo walls Silos should be emptied completely before refilling occasionally they should be cleaned down to remove all traces of material that hangs in corners or in the top surfaces of the silo. If these are not cleared they will, in time, become hard, rancid and may be infested 4.2.6 Handling of flou Handling of flour requires attention to the health hazards which will affect both factory employees and customers who will eat biscuits made from it First, the health of factory employees is considered. Flour is dusty and it is not desirable to breathe in too much flour dust. Some people are allergic to flour dust and develop respiratory diseases. When handling flour, keep the amount of dust produced to a minimum and make sure it is contained. Mixtures of flour dust and air can, in rare circumstances, form explosive mixtures. A spark or flame in such an area will have disastrous results. Such dust mixtures will only occur if the flour handling area has not been kept clean, especially in terms of flour lodged on overhead beams or shelves, or within pneumatic handling equipment. It is essential that all pneumatic handling pipes, c. are well earthed (grounded) to eliminate the possibility of sparks arising from static electric discharges In case an explosion occurs within a silo, explosion relief doors are designed into the top of the silo. The doors will open and pr event damage to the silo itself. Fortunately such explosions are extremely Hazards can arise from unwanted inclusions in the flour. These may be, pieces of paper, string, hair, metal, etc Flour emptied from bags should be put through a sieve and particular care should be taken to place string and labels, released when the bags are opened, into special waste bins and not on the floor. Material on the floor can easily adhere to the bag surface and fall into the flour as the bag is tipped
24 Biscuit, cookie and cracker manufacturing manuals cannot be treated by the entoleter as the particle sizes would be seriously affected. It is therefore important not to store these flours for long before use. Flour silos should be insulated to reduce temperature fluctuations due to weather conditions. If the walls are allowed to cycle strongly in temperature, migration of moisture within the flour may cause lumping and adhesion to the silo walls. Silos should be emptied completely before refilling and occasionally they should be cleaned down to remove all traces of material that hangs in corners or in the top surfaces of the silo. If these are not cleared they will, in time, become hard, rancid and may be infested. 4.2.6 Handling of flour Handling of flour requires attention to the health hazards which will affect both factory employees and customers who will eat biscuits made from it. First, the health of factory employees is considered. Flour is dusty and it is not desirable to breathe in too much flour dust. Some people are allergic to flour dust and develop respiratory diseases. When handling flour, keep the amount of dust produced to a minimum and make sure it is contained. Mixtures of flour dust and air can, in rare circumstances, form explosive mixtures. A spark or flame in such an area will have disastrous results. Such dust mixtures will only occur if the flour handling area has not been kept clean, especially in terms of flour lodged on overhead beams or shelves, or within pneumatic handling equipment. It is essential that all pneumatic handling pipes, etc. are well earthed (grounded) to eliminate the possibility of sparks arising from static electric discharges. In case an explosion occurs within a silo, explosion relief doors are designed into the top of the silo. The doors will open and prevent damage to the silo itself. Fortunately such explosions are extremely rare. Hazards can arise from unwanted inclusions in the flour. These may be, pieces of paper, string, hair, metal, etc. Flour emptied from bags should be put through a sieve and particular care should be taken to place string and labels, released when the bags are opened, into special waste bins and not on the floor. Material on the floor can easily adhere to the bag surface and fall into the flour as the bag is tipped
