Flour, measuring

Data from Szabo (1979) in Table 5.10 show that the adsorption of silica flour (measured in static bulk adsorption) is 55 J,g/g, which is higher than that (3.3 (ig/g) of sand pack (dynamic flow test) because the surface area in the silica flour is higher than that in the sand pack. When the adsorption is defined in g/m, which takes into account the surface area, the adsorption data from the two types of measurements are almost the same (28 (ig/m versus 27 iig/rn ). 

Soft-wheat flours are sold for general family use, as biscuit or cake flours, and for the commercial production of crackers, pretzels, cakes, cookies, and pastry. The protein in soft wheat flour mns from 7 to 10%. There are differences in appearance, texture, and absorption capacity between hard- and soft-wheat flour subjected to the same milling procedures. Hard-wheat flour falls into separate particles if shaken in the hand whereas, soft-wheat flour tends to clump and hold its shape if pressed together. Hard-wheat flour feels slightly coarse and granular when mbbed between the fingers soft-wheat flour feels soft and smooth. Hard-wheat flour absorbs more Hquid than does soft-wheat flour. Consequently, many recipes recommend a variable measure of either flour or Hquid to achieve a desired consistency. 

Defatted soy flour was suspended in water to 8% (v/w) protein, pH was adjusted to 6 by HCl before 640 mg/L Novozyme 415 (a-galactosidase), 10 mg/L Phytase L (Novo Nordisk) and 53 mg enzyme protein/L rhamnogalacturonase B were added. After 4 hours at 50 C the pH was adjusted to 8 by NaOH, and the slurry was centrifuged. The supernatant was pasteurized (85°C, 5 minutes) and freezedried. Protein was measured as 6.25 x Kjeldahl N. Phytate was measured as described in [16], and dietary fibres were analysed as described in [17]. 

Bunzl K, Kracke W. 1987. Soil to plant transfer of 239t240Pu, 238Pu,241 Am, 137Cs and 90Sr from global fallout in flour and bran from wheat, rye, barley and oats, as obtained by field measurements. Sci Total Environ 63 111-124. 

The quantity of protein present is normally measured by the Kjeldahl method. As wheat endosperm protein is around 17.5% nitrogen a factor of 5.7 is normally used to convert Kjeldahl nitrogen measurements into protein. Tkachuk suggested that 5.7 should be used for whole wheat but 5.6 should be used for flour.24... 

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. 

L-Cysteine is normally added as L-cysteine hydrochloride or L-cysteine hydrochloride monohydrate. When the ADD process was in use it was incorporated in a compound improver. If L-cysteine is used as a pastry relaxant it is supplied mixed with either soy flour or an inactivated wheat flour. This of course aids dispersion and the measurement of very small quantities. 

The atoms in molecules can be regarded as behaving like two spheres connected by a spring, with a natural vibration frequency. It so happens that the vibrations of atoms tend to correspond to an energy equivalent to a wavelength in the mid-infrared. It would appear that mid-infrared wavelengths would be useful for measuring the quantity of substances in systems like flour. In practice that is not so. Infrared peaks have a lot of... 

These tests measure the way in which flour behaves when it has been made into a dough. They work with a specially made dough and give an indication of how the flour will behave in that situation. This sort of information is inherently more useful than a mere protein content. 

In theory, analytical testing ought to be able to answer all pertinent questions but, unfortunately, it can not. While measuring the protein content will discriminate between a low protein flour and a high protein flour, the protein content will not necessarily guarantee that a given flour will make a satisfactory loaf of bread. The problem is that it is much easier to measure the quantity of protein present rather than its quality. 

Test baking is one answer to this problem some flour samples that had a good measured composition produce a poor loaf of bread. There are also samples that do not have very promising measured properties... 

The situation is worse where the final product is not bread but some other product, e.g. biscuits. Analytical measurements performed on flour are aimed at measuring its suitability for making bread. For biscuits, the protein content is not important except that for most biscuits high protein flour will not give a satisfactory product. 

The Hagberg Falling Number test only just qualifies for this section as it is an effective way of measuring the a-amylase activity of wheat or flour. It has the considerable advantage that it is unaffected by any added fungal a-amylase. In addition, it only requires a supply of distilled water and electricity - there is no need for chemical glassware or any reagents. 

Brabender make a whole range of instruments for testing flour. These instruments are the standard ones in use in the UK, Germany and North America. The company has recently produced new versions of these instruments that use electronic measuring systems rather than the mechanical systems previously employed. The new models use the same name but with the suffix E. Thus, the new model Extensograph is the Extensograph-E. 

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. 

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. 

Unlike the other tests in this section the grade colour is not a performance test but is a test of the whiteness of flour. The Kent-Jones and Martin colour grade is measured by comparing the reflecting power of a dispersion of flour in water with a standard reference surface. A few patent flours give a negative colour grade, which merely indicates that they are whiter than the reference. 

A flour sample is weighed then mixed with water for a standard time and poured into a glass cuvette. The cuvette is inserted into the instrument, which moves into the measurement position and takes the reflectance reading. The results appear on a LED display and are printed out. The instrument is calibrated with an internal ceramic tile and standardised using a national standard flour. The normal range of flour grades is -5 to +18. 

There is an American test for biscuit flour that involves producing standard cookies baked on a standard aluminium plate. The diameter of the finished product is measured. The greater the diameter the higher the score. This test is of course a measure of dough extensibility, which is the crucial property for biscuit flours. 

Measured quantities of the pre-ferment are mixed with flour. The dough is then subjected to the combination of intense mixing and the action of the oxidising agent. It is then extruded and cut into loaf sized portions, proved and baked. Bread made by the Do-Maker process has a very even crumb texture, which is characteristic of the process. 

Bake testing is an important part of any flour testing regime. It remains true that the odd sample of flour that measures well will bake poorly while the converse situation is also true. The reasons for this are usually because there is a problem with the quality of the protein rather than the quantity. It remains much easier to measure the quantity than the quality of proteins present in flour. 

If experiments are to provide a valid source of information care must be taken about weighing and measuring. All ingredients must be from the same batch unless the test is to compare different batches of flour. In any tests there must be a control experiment lest a variation in, e.g. in the freshness of the yeast, masks a smaller change owing to some other factor. Another important point is that all experiments should be recorded. 

In the study by Thompson, et al. (11), the ml of gel released per 100 g emulsion for the reference emuTsion without soy, with soy isolate (SIF), soy concentrate (SCF) or soy flour (SF) was 6.07, 5.83, 5.49 and 3.08, respectively, when the hydration ratios were 1 4 (flourrwater) for SIF, 1 3 for SCF and 1 2 for SF. The ml gel released per 100 g emulsion containing 10, 15, 20, and 25% soy protein was 6.70, 5.01, 3.94 and 3.57, respectively. When soy protein concentrate was incorporated into an emulsion at the 3.5% level, the processing yields, textural profile and sensory textural attributes of frankfurters were not different among the products with and without added soy concentrate (13). An objective measure of compression and shear modulus indicated that soy protein concentrate incorporated into frankfurters at the 3.5% level had no effect on batter strength or texture ( M). The addition of a cottonseed protein to frankfurters to replace 5, 10 or 15% of the meat resulted in higher pH, less cured color, less firmness of skin, softer texture and reduced desirability as judged by a sensory panel (J5J. 

Functional property tests were conducted in duplicate. AACC (21) methods were used for the determination of water hydration capacity (Method 88-04) and nitrogen solubility index (NSI) (Method 46-23). Oil absorption capacity was measured by the procedures of Lin et al. (22) and oil emulsification by a modification (22) of the Inklaar and Fortuin (23) method. Pasting characteristics of 12.0% (w/v, db) slurries of the flours and processed products were determined on a Brabender Visco/Amylograph (Method 22-10). The slurries were heated from 30 to 95°C before cooling to 50°C to obtain the cold paste viscosity value. Gelation experiments were conducted by heating 15% (w/v db) slurries in sealed stainless steel containers to 90°C for 45 min in a water bath C3). 

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