Ash content of flour

A second problem arose when it was found that a close relationship between flour ash and grain ash existed. There could be two possible reasons for this  

Grain with high ash contains a higher proportion of nonendosperm material. 

One or more of the components of the high-ash grain had higher ash values. 

It was found that the second possibility was correct and that the component that varied in ash was the endosperm. The variation in endosperm ash could be up to 50%. The effect of this is that flours with high endosperm ash may be unfairly penalized if grain is milled to a given flour ash content. 

Source Reproduced by permission from Evers, A. D. et al. 1998. Presented at ICC Technical Conference, Valencia, Spain (http //www. satake.co.uk/laboratory/Ash%20Tony%20Evers.htm). 

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There have been a number of reports in the literature of the measurement of ash content of flour by NIR, and most instrument manufacturers offer this application. There is compiete agreement among experts that ash cannot be measured directly by NIR, and therefore indirect measurement has been proposed via cellulose (61) or oil and particle size (25, 66). Experience in commercial mills has shown that ash calibrations are matrix sensitive and frequent recalibration is required as the grist is changed. AACC Method 08-21 is based on the Perten Instruments 86 Ash Series instruments, based on patented wavelengths that measm-e color (50). 

The conventional test for the purity of flour, with respect to bran contamination, is ash content. Ash is defined as the oxidized residue remaining after flour is incinerated at high temperatures. Because the ash content of bran (up to 8%) is considerably higher than that of the endosperm (0.3%), the ash content of flour is a sensitive index of bran contamination. High ash content of white flour adversely affects both its baking performance and the crumb color of bread baked from it. Therefore, flour specifications usually aim for the minimum ash content. 

The mineral or ash content of flour is also used as an index of flour quality or grade the lower the eish, or the less residue, the whiter or more refined the flour. 

TGA has also been used in the analysis of moisture and ash content of flours, and the moisture content of pasta, coffee and powdered milk. 

High-grade patent flour, which is pure endosperm, has an ash content of 0.30 to 0.35 percent, whereas whole wheat meal may have an ash content from 1.35 to 1.80 percent. 

Protein content of field peas is negatively correlated with lipid, cell wall material (CWM), sugar, and ash content and positively correlated with starch separation efficiency and protein separation efficiency in air classification of pea flour. The lower separation efficiency of low protein peas may be due to their high lipid and CWM content which makes disintegration of seeds and separation into protein and starch particles by pin milling difficult. It is suggested that peas with a specific protein content should be used in order to control the protein and starch fraction contents (18). 

Ravindran (1991) estimated the protein content of ragi to be 9.8%, that of calcium, oxalate, and phytic acid to be 0.24%, 0.44 mg%, and 0.48%, respectively. Hadimani and Malleshi (1993) compared the protein, lipid, ash, calcium, phosphorus, and dietary fiber contents of seven native and milled millets. The protein content of ragi milled flour decreased by 61%... 

Wheat starch is low in protein, ash and fiber, and contains no residual sulfites. Sulfur dioxide is detrimental to the viscoelastic character of wheat gluten and is not used in the commercial production of wheat starch.28,323 The protein content of ten samples of unmodified and modified wheat starches ranged from 0.06-0.22%.28 A 0.23% protein (0.0404% nitrogen) level in wheat starch essentially indicates a gluten-free starch, as confirmed by an enzyme immunoassay.324 That purity of wheat starch is important in diets for celiac individuals. Wheat starch-based, gluten-free flour products were not harmful in the treatment of celiac sprue and dermatitis herpetiformis,325 although traces of an immunoreactive gliadin can be found in wheat starch.326... 

The chemical composition of isolated oat starch is given in Table 15.1. When an oat-flour slurry is centrifuged, the bottom layer is the prime starch. This starch can be purified with repeated washings, and a starch with a protein content of 0.44-0.6% and a lipid content of 0.67-1.11% (dry basis) can be obtained.10,27 The moisture, ash and nitrogen contents are similar to those of wheat, whereas the lipid content is higher than that of wheat, and the amylose content is lower.15... 

Use as Human Food. Rapeseed, as a protein source for humans, has many obstacles to overcome. The glucosinolate and fiber contents require application of new processing technology (22, 30) to eliminate antinutritional qualities. Rapeseed flours, protein concentrates, and isolates are lower in protein but higher in crude fiber and ash contents than corresponding soybean products. Rapeseed flours are comparable to soybean flour in water adsorption and give much higher fat adsorption, oil... 

Low moisture content of fillers are typically observed in calcium carbonate and wollastonite (0.01-0.5%), talc and aluminum trihydrate, mica (0.1-0.6%). Medium moisture content can be observed in titanium hydroxide (to 1.5%), clay (to 3%), kaolin (1-2%), and Biodac (2-3%). High moisture content is often seen in cellulose fiber (5-10%), wood flour (to 12%), and fly ash (to 20%). Biodac absorbs 120% of water under direct contact with an excess of water. 

The other fine powder components, added to control the workability of concrete mixture are fly ash, limestone flour and ground granulated blastfurnace slag. The content of these mineral additions can be substantially high when cement type CEM 1 is used they substitute up to 50% cement, particularly that of class 42.5. One can conclude that the Portland cements with mineral additions can be also applied. The effect of limestone flour on the properties of concrete mixture was studied, among the others, by Gizeszczyk [32],... 

Ash content is a measure of total minerals and is a reliable index of nutritional value for many foods (tea, flour, edible gelatin, etc.) and feed (for poultry and cattle) and is recognized as a useful tool in determining the nature and distribution of mineral constituents of food. Ash is the inorganic material left after complete oxidation of organic material at high temperatures (500-600°C). 

M. Iwamoto, N. Kongseree, J. Uozomi, T. Suzuki. Determination of ash content in homegrown wheat flour in Japan by near-infrared diffuse reflectance analysis. Nippon Shokuhin Kogyo Gakkaishi 33 842-847,1986. 

Bread flours are standardized on the basis of their ash content in Europe and, particularly, Germany. The type of flour = ash content (weight %) x 1000 corresponds to the extraction grade. Examples are provided in Table 15.36 for wheat and rye flours and their chemical composition... 

The physical properties of the cellulosic fillers tested are given in Table 1. The three wood based cellulosic fillers had low ash contents which indicates low abrasion potential during processing. The aspect ratios of the fillers varied considerably with the aspect ratio of wood flour being less than either pulp mill residue or thermomechanical fiber as expected. 

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