Content area
Full text
Cereal Chem. 88(4):349-351
In the process of milling wheat into flour, a proportion of the starch granules are mechanically damaged, leaving them crushed or fractured. The level of damaged starch affects water absorption during dough mixing and the miller aims for an optimum level of starch damage, resulting in optimum dough handling properties and high-quality end products. Therefore, starch damage content is an important parameter to measure when evaluating flour quality.
A number of methods have been published to measure degree of damaged starch in flour. These include enzymatic methods (Approved Methods 76-30.01 and 76-31.01; AACC International 2010) and amperometric methods such as SDmatic (AACC Approved Method 76-33.01). The SDmatic method is an approved secondary reference method and needs to be calibrated against a suitable primary reference method such as the Megazyme starch damage method (AACC Approved Method 76-3 1.01).
The Megazyme method, while very accurate, is relatively complex and requires a high level of operator skill. Therefore, it has a far greater possibility of error without adequate training. In contrast, the SDmatic is a simpler and cheaper method that can analyze a small sample number faster than the Megazyme method. However, the accuracy of the SDmatic depends on having a reliable calibration for the results to be highly correlated to other reference methods.
The relationship between the two standard AACC methods for determining damaged starch was investigated in a previous study (McAllister et al 2008). An SDmatic (Chopin Technologies, Villeneuve La Garenne, France) was calibrated with 30 samples with a wide range of starch damage values (2.7-8.5%) determined by the Megazyme method. The correlation between results for the two methods was quadratic (r2 = 0.94). However, for some samples, there was a discrepancy of <0.9% (absolute value) between the two methods. Because starch damage values have a range of 5-10% (Bloksma 1988), a 0.9% (absolute value) difference between the SDmatic and Megazyme methods is a large proportion of the error.
The two methods investigated in this study rely on very different approaches to determine starch damage, each utilizing a different chemical interaction with starch granules. Conventional wheat starch consists of both amylose and amylopectin. Among commercial cultivars of wheat, there is a relatively large genetic variation in the proportion of amylose to amylopectin...