Flour water absorption

Type of flour Water absorption (%) Development time (min) Stability ( min) Resistance (BU) Area (cm3)... 

There are three major control parameters dnring the critical step of dough mixing flour water absorption, dough mixing time, and dongh temperature. The dough... 

Oilseed proteins are used as food ingredients at concentrations of 1—2% to nearly 100%. At low concentrations, the proteins are added primarily for their functional properties, eg, emulsification, fat absorption, water absorption, texture, dough formation, adhesion, cohesion, elasticity, film formation, and aeration (86) (see Food processing). Because of high protein contents, textured flours and concentrates are used as the principal ingredients of some meat substitutes. 

Compression and injection molding are used with amino resins to produce articles such as radio cabinets, buttons, and cover plates. Because melamine resins have lower water absorption and better chemical and heat resistance than urea resins, they are used to produce dinnerware and laminates used to cover furniture. Almost ah molded objects use fillers such as cellulose, asbestos, glass, wood flour, glass fiber and paper. The 1997 U.S. production of amino resins was 2.6 billion pounds. 

It is not particularly easy to measure the degree of starch damage present. The usual method involves treating the flour with a-amylase, which can only attack the damaged starch. The procedure requires an a-amylase preparation that has to be standardised. Alternatively, an estimate can be made by optical microscopy or by calculating from the water absorption of the flour and its protein content, assuming that the water absorption that exceeds that to be expected from the protein alone is due to the damaged starch. 

The water absorption measured by the Farinograph is normally reported as a percentage. The barbarous units of gallons per sack is sometimes encountered. A sack of flour contained 20 stones or 280 lbs of flour (approx. 127 kg). This unit was used when mixes were referred to as a certain number of sacks of flour and the water added was measured in gallons. 

Farinograph doughs only contain flour and water, so the water absorption obtained is a theoretical value. The value obtained from the same batch of flour in a bread dough will always be lower. When the Farinograph is used to prepare doughs for the Extensograph, the doughs do contain flour, salt and water. 

In a flour mill the Farinograph is used as a control instrument since the water absorption of flour can be increased or reduced by adjusting the mill, to deliver more or less starch damage. If the water absorption is too low, the pressure on the reduction rollers of the mill will be increased, thereby increasing the starch damage. Similarly, if the water absorption and hence the starch damage is too high the pressure must be... 

In a bakery the Farinograph can be used to test whether the flour is in specification or not. It would be possible to add more or less water, depending on a measured water absorption. 

In general wholemeal bread is made with shorter fermentation times than white bread. As wholemeal flour has a higher water absorption than white a higher water addition can be used. 

Conventional improvers are not used in rye bread but additives are sometimes used to increase the water absorption of the dough. Examples are polysaccharide gums such as guar and locust bean gum as well as pregelatinised potato flour, rice starch or maize starch. 

Commercial cowpea flour available in Nigeria has not been well received by consumers because of its poor water absorption and because akara prepared from the flour is heavy, lacks crispness, and lacks the flavor typical of products made from fresh paste (8). 

The poor performance of finely milled cowpea flours may be due to changes in physical form and structure which occur as a result of milling. Sefa-Dedah and Stanley (10) investigated the relationship of microstructure of cowpeas to water absorption and decortication... 

Field Pea Flour in Other Baked Products. When McWatters (44) substituted 8% field pea flour and 4.6% field pea concentrate for milk protein (6%) in baking powder biscuits, sensory attributes, crumb color, and density of the resulting biscuits were adversely affected. No modifications were made in recipe formulation when pea products were incorporated. The doughs were slightly less sticky than control biscuits that contained whole milk. This might be due to lack of lactose or to the different water absorption properties of pea protein or starch. Panelists described the aroma and flavor of these biscuits as harsh, beany and strong. Steam heating the field pea flour improved the sensory evaluation scores, but they were never equivalent to those for the controls. 

Raidl and Klein (43) substituted 5, 10, and 15% field pea flour in chemically leavened quick bread. The viscosity of the pea flour batters was significantly lower than either the wheat control or soy containing batters. The starch composition of the pea flour and lower water absorption properties of the protein could have affected the viscosity. Volumes of pea flour loaves were lower than the control and soy loaves. Most of the sensory characteristics of the field pea loaves were similar to those of the control quick breads. However, all flavor scores were significantly lower for pea flour products, since they had a recognizably beany or off-flavor. 

For measuring water absorption by the excess water method, the techniques developed by Janicki and Walczak (described by Hamm, 21) for meats and by Sosulski (22) for wheat flour are modified. Lin et al. (17) modified the Sosulski technique for use with sunflower and soy meal products. This modified procedure has been employed for much of the research on water absorption of plant protein additives. Water absorption capacities of a soy flour, two soy concentrates, and two soy isolates were compared by Lin et al. (17) to those of a sunflower flour, three sunflower concentrates, and one sunflower isolate. The percent water absorption of the soy products increased as the total protein content of the samples increased from flour to isolate. The soy flour absorbed 130% water, the soy concentrates absorbed an average of 212% water, and the soy isolates absorbed an average of 432% water. No calculations were made, however, that related the percent water absorbed to protein content of the samples. The sunflower products, though similar in protein content, did not respond in the same magnitude or direction as the soy products. 

As protein content increased from soy flour to soy isolate, water absorption also increased. This was not the case for sunflower products (17). 

Fleming et al. (18) did not examine the effect of pH on water absorption, but these researchers examined the effect of "pH activation" on water absorption of sunflower and soy products. For pH activation, 1.25 N NaOH was added to slurries to achieve pH 12.2 and then 6.0 N HGl was added to return to pH 6.0 in 10 min. The pH activation process improved the water absorption properties for most products but did not increase water absorption of the soy flour. Processes similar to pH activation may be encountered in the processing of vegetable protein additives. 

Water absorption of WPC was little affected by ionic strength. Fleming et al. (18] examined the effect of 5% NaCI on the water absorption of soy and sunflower flours, concentrates, and isolates. The water absorption of the soy and sunflower flours was higher in 5% NaCI than in water. Generally, salt decreased water absorption of the isolates the concentrates of both plant products were little affected by NaCI. Data reported by Fleming et al. reflect a response to NaCI however, the type of ion is known to affect the type of response of other properties (33] and possibly the same is true for water absorption. 

Ghosh et al. (2004) reported the effects of ground flaxseed on wheat flour tortilla quality. Ground flaxseed addition significantly increased water absorption and decreased dough strength. However, the presence of nonstarch... 

Particulate fillers, on the other hand, are believed to extend the pathway along which the water must diffuse, resulting in a reduction in the rate of water absorption. Silica flour (1 to 75 pm) has been reported as improving the boiling water resistance of epoxy films. Figure 9.8 shows the water absorption rate at 40°C of water in DGEBA epoxy filled with various types of materials. 

The protein efficiency ratio (PER) of sesame seed protein is 1.86 (35). The PER value can be raised to 2.9 when sesame seed protein is supplemented with lysine (36). El-Adawy (37) added sesame products including sesame meal, sesame protein isolate, and protein concentrate to red wheat flour to produce flour blends. It was found that water absorption, development time, and dough weakening were increased as the protein level increased in all blends however, dough stability decreased. Sesame products could be added to wheat flour up to 16% protein without any detrimental effect on bread sensory properties. The addition of sesame products to red wheat flour increased the contents of protein, minerals, and total essential amino acids the in vitro protein digestibility also increased significantly. 

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