Flour from the viewpoint of the biscuit manufacturer 8.3.1 Function of flour in biscuits Flour is the main ingredient in most biscuits It does not contribute much flavour, except perhaps where bran is included It does contribute strongly to the baked texture, hardness and shape of biscuits The nature of these effects differs for different biscuits related to the enrichment with fat and sugar and to the way in which the dough has been mixed More details will be given where the different types of biscuit are described but theprincipal property of flour of interest to biscuit makers is the quantity and quality of protein and thus of the gluten that is formed when the flour is mixed with water Most biscuits can be made from flour which has a low quantity of protein and has a gluten that is weak and extensible Thus flour with a protein level of less than 9% is best and levels of more than 9.5% often create processing problems The exceptions are fermented cracker doughs and puff doughs where a medium strength of flour is needed, with protein values of 10.5% or more If the ash content of a white flour is too high the function of the gluten during baking is impaired and the structure of the biscuit may look grey To a certain extent the quality of the gluten can be adjusted by additives and processing techniques The problems of specifying flour quality for biscuit making have already been described They rest very much on the recipe of the product and the effect on the baked biscuit These are factors which the miller cannot reasonably be expected to know much Wheat flour and vital wheat gluten 97 about and he is not in a position to make critical baking tests An important aspect to the baker is a consistency in quality of the flour he uses What a baker does not like is varying flour and for this reason it is strongly recommended that a close liaison is maintained between miller/supplier and baker so that each understands and is informed of the other’s problems It is best to keep to one grade from one mill for each biscuit recipe and not to chop and change even for financial reasons Significant difficulties can be expected where deliveries of bagged flour from widely different sources is the norm This happens in many developing countries where flour is imported or governments control the importation of wheat Some dough and baking problems related to flour are considered in the sections on specific biscuit types and also in Manual by Manley [13] 8.3.2 Flour specification The purpose of a specification is to agree with the supplier measurable parameters of a material which are relevant to the use for which the material is to be put In the case of flour this presupposes that critical parameters are known in relation to the function of the flour in different biscuit processing A specification is no use if both the supplier and the user cannot agree measurement techniques or if it is beyond the capability of the supplier consistently to meet the limitations required for each parameter There may be some specific characteristics for a flour for a special purpose but in general a typical specification for a biscuit flour to be used for chemically aerated biscuits, i.e., not fermented doughs, will include some or all of the characteristics and values shown in Table 8.3 In the USA it is common to specify a Spread Factor as determined by the Cookie Spread Test AACC [11] This is a baking test for short dough cookies Results in the order of 55 are the norm and a range of is usual for the range The miller can reduce the Spread Factor of a flour by treatment with chlorine gas Table 8.3 Typical specification of flour used for chemically aerated biscuits Wheat type A maximum content of soft wheat varieties Moisture content 14.0% 0.5% Smell Free from mustiness (moulds), no taints from paint, detergents, hessian bags, etc Protein n 57 9.0% 0.5% Colour grade figure (Kent-Jones) 3.5 1.0 or ash content 0.46–0.55 Particle size range particles greater than 250m less than 1% particles greater than 50m 40% 5% Simon Research values 100E/R 7.5 1.0 or Alveograph values W (baking strength) 140 10 P/L 1.8 0.3 or Brabender Extensograph values Resistance, Brab units 330 50 Extensibility, cm 15.6 1.0 Statutory additives As applicable 8.3.3 Checks and tests on flour deliveries It is advisable to sample flour from each delivery and to retain a good sized quantity (say kg) in a sealed tin until all of that delivery has been used Before the delivery is accepted, an attempt should be made to check that the flour is of the grade required since a gross error as, for example, the acceptance of a bread flour, will give enormous problems in disposal if the flour has been transferred to a silo The best quick check is a colour test This can be made either with a Kent-Jones colour grader, a Pekar test or with a Branscan The Pekar test involves smoothing a small dry sample of the flour adjacent to a reference flour with a polished metal spatula and then carefully dipping the flour into some water A skin forms on the flour surface and observation by eye immediately allows comparison of the colour and size of the bran particles If the new flour and the reference are very different, further investigation should proceed at once Other tests such as moisture and any rheological or baking tests may be made before the consignment is released for use in the factory but it is not normally practical to make such tests before accepting a delivery If possible a new load of bulk flour should be put into an emptied silo This ensures correct rotation of the flour and effective quality control Unfortunately, flour silos are usually larger than the bulk tanker so more than one consignment is placed against another Problems may arise because silos rarely discharge in a systematic first in, first out fashion If this happens, it can mean that old flour will become lodged and may be compacted around the silo sides and bottom corners A procedure of regular emptying must be maintained, even if this involves entry into the silos to knock down the compacted and lodged flour Design of flour silos frequently is poor in this respect Tall narrow circular silos are the best shape if this sort of problem is to be avoided Testing of the flour should be related to the specification and the use to be made of the flour Unfortunately, protein or flour/water rheological tests may be time consuming and provide little relevant information Flour delivered in bags should be marked prior to storage to ensure correct rotation of stocks Any damaged bags should be used early as spillage is both wasteful and a hazard to general infestation Bagged stocks should always be stored on pallets at not more than about 10 bags high The flour store should be cool, well ventilated and rodent, bird and if possible insect proof If the stock is to be kept for prolonged periods, arrangements should be made with the miller supplier to have moisture contents around 13% or below 8.3.4 Conveying, screening and weighing Bulk flour is normally conveyed from the silo by air A rotary seal at the base of the silo delivers flour into an air stream provided by pumps The volume of air to flour is normally considerable and due to the way in which the flour falls into the rotary seal the delivery from the silo is usually somewhat irregular A rotary seal beneath a silo is not a reliable way of metering flour The temperature and humidity of the conveying air may have an effect on the flour moisture It is wise to pass the flour through a screen, either planetary or rotary, prior to metering into a mixer In this way any lumps or unfortunate larger pieces included with the flour are removed It is wise to check daily what tails over these screens as it may indicate problems Flour may be weighed above, or in a mixer, or even remotely and then passed to the mixer The latter system may be more economical on equipment but is likely to result in less accurate metering The biggest variation in mixed dough consistencies is Wheat flour and vital wheat gluten 99 likely to be due to poor metering of ingredients and that of flour is usually the worst The subject of ingredient metering is discussed in more detail in Section 32.5 Flour from bags presents another set of problems In opening bags it is easy for string, labels or paper to fall with the flour Operators should be warned about this and a bin provided nearby for them to use for rubbish If the waste is dropped on the floor it often sticks to the outside of a new bag and drops with the flour as the bag is lifted for emptying Hygiene considerations at the flour bag tipping point are never wasted As for bulk flour, it is wise to include a sieving system between bag tip and mixer/weighing 8.3.5 Overcoming flour variations It is fair to say that we have not reached the stage where the ability to measure meaningful properties of flour quality allows feed-forward for process control It is therefore necessary to all that is possible to reduce variations in supplies of flour The best means is to blend A flour miller reduces the effects of wheat variation by blending loads of wheat and the same can be done in the bakery by blending several different flours Care should be taken that the blending is well planned otherwise even more variation can be experienced because variable quantities of each constituent are arriving at the mixer A problem occurs annually with new crop wheat The freshly harvested wheat always produces a different quality of flour The wheat also changes gradually in store from the time that it is harvested To overcome the effects of this, the baker should insist that the proportion of new crop wheat in the grist at the mill is increased slowly over at least four and ideally more weeks This will ensure that the amount of very fresh wheat is at a minimum and will allow adjustments to be made gradually in the bakery The miller supplier should communicate the percentage of new crop wheat being used so that the baker can at least be prepared Changes in biscuit flour properties can be demonstrated as the flour is stored, even for a few weeks The changes affect the protein and generally the effect is to make the gluten less extensible No way is yet known to overcome this so it is important to store the flour for minimum or uniform periods Flour up in blind spots in silos can be a cause of variation for this reason 8.3.6 Brown flours If brown, wheatmeal or germ enriched types of flours are used, there are other considerations to be made Contamination of white flour with bran at the biscuit factory spoils the efforts of the miller so unless a large amount of brown flour is to be used, it is unwise to put it into a bulk- handling system shared with white flours Usually the bran particles are of significant but uniform size (about to mm in diameter) so sieving will tend to separate the bran from the white flour Screening before use is therefore not desirable Brown flours are usually fed to the mixers from bags or are handled in dedicated bulk systems The other option is to create brown flour in the mixer by using a specific grade and quantity of bran with white flour 8.3.7 Dusting flours These are used in relatively small quantities to aid the passage of dough through the forming machinery or to dry the surface of an oven band The important quality of 100 Technology of biscuits, crackers and cookies dusting flour is excellent flowability so that a thin even coating can be produced from the dusting machine Weak flours or damp flours not flow well so strong bread type flours are often used Air classification (see Section 8.2.8) can result in a coarser flour with the fine fractions removed Passage through the air classifier also tends to reduce the natural moisture content and this improves the flow characteristics Certain domestic flours which are claimed not to require sieving before use have been prepared to improve their flowability and these will be useful to the biscuit maker as dusting flour As a rough guide, if a handful of flour, when squeezed tight, remains in a ball when the hand is opened, it is unlikely to form a good dusting flour 8.3.8 Developments in flour types The development of levels of heat treatment to affect the texture forming properties or the spread during baking has been mentioned above However, the most interesting developments in ‘flours’ are associated with the introduction of pieces and increases in the fibre content The developments have been motivated by the demand for more dietary fibre and hence the use of more bran By heating, steaming, chopping or rolling wheat various flakes and soft pieces of whole wheat can be made Incorporation of these into flour allows biscuits to be made with different eating textures The pieces may also be of rye, oats or barley (see Chapter 9)