186 Determination of the Solvent Retention Capacity (SRC) of wheat flour using the CHOPIN-SRC

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Methods Type: Generic Methods
Key data
Number: 186
Status: Draft (2019)
Analyte: Solvent Retention Capacity
Matrix: Wheat Flour
 
 
Scope and field of application:

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

The SRC method was originally developed in the USA and is well known to be particularly adapted to soft wheat flour. There is much evidence for its beneficial application in determining a flour’s functionality for biscuit manufacturing, cracker manufacturing, and sugar-snap and wire-cut cookie laboratory tests.                               

The CHOPIN-SRC method has been proposed and demonstrated to not replace any existing methods, but to add information and help better explain some observed dough rheological or baking behaviors).

Over time, the SRC method has been successfully used to evaluate not only soft wheat flours, but also hard winter wheat flours and hard red spring wheat flours).

Since the SRC test results predict the functionality of the main flour polymers, and because it is known that the proportion and quality of these components are affected by the milling process, it is logical to study the impact of milling on the SRC characteristics of flour. An early approach studied the impact on test milling. Blending wheats is an important step for millers to achieve flour consistency. Tempering modifies wheat kernel texture and thus the amounts, proportions, and functionality of flour polymers. Flour chlorination and particle size have also been shown to impact SRC values and finished-product quality. Heat treatment, which is often used in many mills around the world, also impacts flour polymers.

The widespread interest in the SRC method arises from the fact that a flour’s three main functional components impact dough behavior during processing and baking. Glutenins, damaged starch, and pentosans are the three main network-forming polymers in wheat flour. They are functional polymers, because they greatly influence dough behavior during processing (e.g. machinability) and baking, as well as final product quality. Viscoelastic glutenins influence dough elasticity and extensibility, damaged starch influences dough stickiness, and the highly water-holding pentosans markedly increase dough viscosity. In cookie-making, for example, a flour’s water absorption should be as low as possible, and in particular, with minimized contributions from pentosans and damaged starch. This fact illustrates that a given water requirement for a flour can have different causes, which can help to explain consequent differences in dough behavior during mixing, machining, and baking.

References:

- ICC Standard No 101/2, Sampling of cereal grains

- ICC Standard No. 110/1, Determination of moisture content of cereals and cereal products (practical method)

- ICC Standard No 130, Sampling of milling products (Semolina, flours, agglomerated flours and by-products)

- ICC Standard No 138, Mechanical sampling of milled cereal products

Definitions:

- Solvent retention capacity (SRC) is the weight of solvent retained by a wet, swollen flour pellet after centrifugation, and is expressed as a percentage of the original flour weight (adjusted to 14% moisture basis). In this test, four different aqueous solutions – lactic acid (5 % by weight, then abbreviated 5 w%), sodium carbonate (5 w%), sucrose (50 w%), and water are used to predict the performance of the principal functional components of a wheat flour system.

- Lactic acid SRC (LAC-SRC) is associated with glutenin characteristics (an indicator of gluten quality),

- Sodium carbonate SRC (CAR-SRC) is associated with starch damage (and indirectly, with flour hardness)

- Sucrose SRC (SUC-SRC) is associated with pentosan content and gliadin characteristics.

- Water SRC (WA-SRC) is associated with all four constituents, thus providing an overall picture of water retention capability in a dough/baked product system. The characterization of wheat, based on SRC analysis, highlights wheat flour chemical, rheological, and baking aspects.

Gluten Performance Index (GPI) is calculated by dividing the SRC Lactic Acid value (glutenin functionality) by the combined values of SRC Sucrose plus SRC Sodium Carbonate.  The ratio represents the prediction of the detrimental effects of damaged starch and arabinoxylans on gluten performance.  Typical values for this ratio in flour for optimized cracker processing and product quality have been determined to be greater than 0.60.

 

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