56 Physicochemical Tests Methods

56-10.02 Alkaline Water Retention Capacity

Alkaline water retention capacity (AWRC) is the amount of alkaline water held by flour at 14% moisture basis after centrifugation. AWRC, expressed as percent of flour weight, is inversely correlated with cookie spread. The method is applicable to predicting flour quality for sugar-snap cookies, which are made slightly alkaline by leavening agents.

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56-11.02 Solvent Retention Capacity Profile

Solvent retention capacity (SRC) is the weight of solvent held by flour after centrifugation. It is expressed as percent of flour weight, on a 14% moisture basis. Four solvents are independently used to produce four SRC values: water SRC, 50% sucrose SRC, 5% sodium carbonate SRC, and 5% lactic acid SRC. The combined pattern of the four SRC values establishes a practical flour quality/functionality profile useful for predicting baking performance and specification conformance. Generally, lactic acid SRC is associated with glutenin characteristics, sodium carbonate SRC with levels of damaged starch, and sucrose SRC with pentosan characteristics. Water SRC is influenced by all of those flour constituents.

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56-15.01 Solvent Retention Capacity Profile – Automated Measurement

Solvent retention capacity (SRC) is the weight of solvent held by flour after centrifugation. It is expressed as percent of flour weight on a 14% moisture basis. Four solvents are independently used to produce four SRC values: water SRC, 50% sucrose SRC, 5% sodium carbonate SRC, and 5% lactic acid SRC. The combined pattern of the four SRC values establishes a practical flour quality/functionality profile useful for predicting baking performance and specification conformance. Generally, lactic acid SRC is associated with glutenin characteristics, sodium carbonate SRC with levels of damaged starch, and sucrose SRC with pentosan characteristics. Water SRC is influenced by all of those flour constituents. Gluten performance index (GPI) is calculated by dividing the lactic acid SRC value (glutenin functionality) by the combined sucrose and sodium carbonate SRC values. The ratio represents a prediction of the detrimental effects of damaged starch and arabinoxylans on gluten performance (e.g., in snack cracker production).

This method is applicable to wheat flour obtained from Triticum aestivum from a laboratory or from industrial milling.

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56-20.01 Hydration Capacity of Pregelatinized Cereal Products

The uptake and retention of water by cereal products is related to functionality parameters such as cooking time and texture following cooking. This method is applicable to pregelatinized starches and to cereal products that contain pregelatinized starches, e.g., roll- and spray-dried cereals, extruded materials, and various products cooked with steam. It is not suitable for products that contain over 25% water-soluble material.

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56-21.01 Flour Swelling Volume

Gelatinization and swelling of wheat starch has an important effect on the quality of end-use products, especially on the quality of white salted noodles. The flour swelling volume (FSV) test measures the cumulative effect of starch quality, specifically the amylose-amylopectin (AM-AP) ratio as reflected by the volume of gel produced when flour is heated with an excess of water. Starch composition (i.e., the AM-AP ratio) has the greatest impact on FSV. FSV is related to the eating quality (texture) of white salted noodles as well as to the gene dosage of granule-bound starch synthase that controls the AM-AP ratio. FSV is not much affected by mild to moderate preharvest sprouting. This method is applicable to wheat meal, flour, or starch. It may be useful in monitoring the impact of starch additives as well.

A video demonstration accompanies this method.

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56-25.01 Oxidative Gelation of Aqueous Wheat Flour Suspensions

Viscosity is a critical parameter in the production of many end-use flour products. This method is applicable for soft wheat products, such as biscuits (cookies) or wafers, where factors other than gluten are considered more important in end-use quality. The method estimates the impact of arabinoxylan polymerization by di-ferulate bonds and ferulic acid-tyrosine cross-linking. Intrinsic viscosity is measured with a flour-water slurry, and the maximum oxidative gelation potential is measured with a flour-water-peroxide system, which creates free radicals that catalyze the reaction.

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56-30.01 Water Hydration Capacity of Protein Materials

Water hydration capacity (water absorption, water uptake, or water holding or binding) is determined as the maximum amount of water that 1 g of material will imbibe and retain under low-speed centrifugation. Since only enough water is added to saturate the sample and not to cause a liquid phase, measurement is not affected by solubility of the material. It thus differs from Method 56-20.01, which uses excess water. This method applies to protein flours, concentrates, and isolates of vegetable or animal origin that consist of native, modified, or denatured protein. It also applies to other materials, such as pregelantinized starch products, in which water uptake is an important characteristic

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56-40.01 Water Hydration (Absorption) of Rolled Oats

Water hydration (or water absorption or water uptake) is the amount of water held by a rolled oats sample when excess distilled water is added and allowed to drain from the sample under a standardized set of conditions. The method establishes a practical procedure to predict functionality in rolled oats ingredient applications.

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56-50.01 Pelshenke Test (Wheat-Meal Fermentation Time Test)

This method is based on the capacity of a ball of yeasted dough to retain the gas produced during fermentation. The method provides an indication of gluten strength in wheat, i.e., the longer the gas retention (time elapsed for ball to disintegrate), the higher the gluten strength. It is used as a screening method in wheat breeding. See Ref. 7.

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56-60.01 Sedimentation Test for Flour

Based on the capacity of gluten proteins to swell under the influence of lactic acid, this method measures the relative gluten strength in wheat flour. Sedimentation volumes (values) reflect differences in both protein quantity and protein quality. There is a positive correlation between sedimentation volume and gluten strength, or loaf volume. The method is used as a screening test in wheat breeding. In commercial or experimental milling, it is used only for comparing lots of the same grade of flour milled by the same mill.

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56-61.02 Sedimentation Test for Wheat

Based on the capacity of gluten proteins to swell under the influence of lactic acid, this method measures the relative gluten strength in wheat flour. Sedimentation volumes (values) reflect differences in both protein quantity and protein quality. There is a positive correlation between sedimentation volume and gluten strength, or loaf volume. The method is used as a screening test in wheat breeding. In commercial or experimental milling, it is used only for comparing lots of the same grade of flour milled by the same mill. This method is especially suitable to wheat meal or to whole meal flour sieved from wheat whole meal.

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56-62.01 Modified Sedimentation Test for Wheat

This method is especially applicable to very strong wheats at high protein levels, since maximum sedimentation value obtainable by Method 56-61.02 is not sufficiently high to reflect their true quality, a condition referred to as "ceiling effect." In its purpose and principle, this method is similar to Method 56-61.02. It differs from Method 56-61.02 in two ways: First, the volume of reagent is doubled to eliminate "ceiling effect," and second, the normality of reagent is reduced proportionately to maintain the same final acidity as in Method 56-61.02.

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56-63.01 Micro Sedimentation Test for Wheat

This method is similar to Method 56-61A in principle, but it uses a 10-fold reduction in sample size. It is based on measuring volume of sediment that results from treating a water-flour mixture with lactic acid. The essential differences are: 1) a larger proportionate amount of reagent to overcome "ceiling effect" (see Note); 2) reduction in mill roll spacing to increase flour yield; and 3) adjustment of wheat moisture content to approximately 13% to avoid variations due to moisture. It is especially used as a screen method in early-generation selections in wheat breeding.

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56-70.01 Sodium Dodecyl Sulfate Sedimentation Test for Durum Wheat

This method measures the relative gluten strength in whole durum wheat meal without a sieving requirement. See Ref. 3. It is useful in screening plant breeder and commercial durum wheat samples. The method is designed to test batch of eight samples of durum wheat and is somewhat similar to Method 56-61A.

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56-81.04 Determination of Falling Number

This method is based on the ability of α-amylase to liquefy a starch gel. The activity of the enzyme is measured by falling number (FN), defined as time in seconds required to stir and allow stirrer to fall a measured distance through a hot aqueous flour or meal gel undergoing liquefaction. α-Amylase activity is associated with kernel sprouting, and both of these are inversely correlated with FN. The method is applicable to both meal and flour of small grains and to malted cereals.

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56-99.01 Glossary—Grain and Flour

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