Miller Magazine Issue: 122 February 2020

49 COVER STORY MILLER / FEBRUARY 2020 greater. Increased enzyme activity will decrease the falling number. Flour milled from badly sprouted wheat may have falling numbers of 50 to 100 sec. Bread flours are generally adjusted to 250-300 seconds. The procedure is rapid and reasonably reproducible. It can be used for either whole- wheat meal or flour. 2) Amylograph In this procedure, flour and a buffer solution are stirred in a rotating bowl that is heated by an air bath. The sample is heated from room temperature to 95˚C (203˚F) at a rate of 1.5˚C/minute. If one is only interested in the α -amylase activity, the test can be ended when the slurry reaches 95˚C (203˚F). If the flour contains no α -amylase activity the vis- cosity (consistency) of the sample will continue to increase as the temperature rises to 95˚C. Optimally treated bread flours are in the range of 400-600 BU. If there is increased enzyme activity, the curve will peak at a lower viscosity (consistency) and at a lower temperature. The peak height is taken as the measure of enzyme activity. The amylograph procedure is relatively slow The procedure is reproducible and still widely used to control the level of malt addition. 3) Rapid Visco Analyzer (RvA) The RvA was developed as a faster and more rugged ver- sion of the amylograph. Stimulating the amylograph, the temperature control can be programmed to heat at various rates. This viscosity is determined by the load on the stirring motor. As is the case with the amylograph, the height of the viscosity vs. temperature curve is related to the α -amy- lase activity of the sample. Because of the flexibility in con- trolling heating/cooling profile, the RVA has found many uses in cereal laboratories in addition to determining α -am- ylase activity. The RVA can also stimulate the falling number method when samples are heated at 95˚C (203˚F) for three minutes. The stirring number is reported as the viscosity at the test’s end. PROTEOLYTIC ACTIVITY Proteolytic enzymes hydrolyze proteins. Proteolytic ac- tivity can be divided into two basic types. Some enzymes hydrolyze an amino acid from the end of a protein molecule while other proteolytic enzymes attack the protein chain internally. The attack is not random but instead occurs be- tween specific amino acids. The two types of the enzyme are classified as exo- (which releases amino acids from the exterior) and endo- (which breaks the protein chain inter- nally). • Soluble Nitrogen The most popular method is to measure soluble nitrogen produced from a suitable substrate. The buffered enzyme is incubated with hemoglobin (substrate) for a suitable time. The protein is precipitated and the remaining soluble ni- trogen determined. The results are reported as hemoglobin units (H.U.). This is a very popular method to measure pro- teolytic activity but it can be misleading. The test is biased to measure exo-enzyme activity. There can be considerable endo-activity with little or no soluble nitrogen produced. Additionally, flour proteins may be degraded differently than hemoglobin. • Rheological Measurement The chemical determination of endo-proteolytic activity is complicated and difficult. Because the endo-proteolytic enzyme significantly reduces the size of the protein mol- ecule by its activity, it changes the rheological properties (viscosity or consistency) of the system. Thus, the dough becomes more viscous and less elastic as the result of the endo-proteolytic activity. The enzyme activity can then be estimated by following the change in rheological proper- ties as a function of time. One of the advantages of using a rheological test is that it is not affected by the exo-pro- teolytic activity. Reducing the size of the protein by one amino acid is insignificant from a rheological viewpoint. The other advantage is that the substrate used (native gluten) and the conditions of the test (dough) both apply directly to our area of concern. A number of rheological tests have been used to follow endo-proteolytic activity. The most appropriate appears to be the extensograph, al- veograph, and lubricated compression. GLUTEN INDEX Gluten index provides a qualitative measure of the glu- ten forming proteins. Gluten separated from the whole wheat meal or wheat flour by the Glutomatic equipment is centrifuged to force wet gluten through a specially con- structed sieve under standardized conditions. The percent- age of wet gluten remaining on the sieve after centrifu- gation is defined as the Gluten Index. If the gluten is very weak, all of the gluten may pass through the sieve, the gluten index is 0. When nothing passes through the sieve, the index is 100. It is pertinent to point out that all the outlined objectives cannot be achieved without full cooperation from all the stakeholders and most importantly ownership of quality by stakeholders. However, implementation of some of the quality control objective is not always acceptable to the millers because while the quality control ensures that sampled products conform to set standards by subjecting them to tests and if an off-norm situation is detected in some of the samples. Depending on how critical nature of the off-norms, it may require mills being shut down before the exception could be corrected, bagging operations be- ing halted or some bagged products being quarantined for proper checks before their eventual release after passing the quality checks. The ability of quality control in propa- gating the culture of quality as the responsibility of every- one as well as the ability to embark on quality education to make all stakeholders interested in the production of quality products. The importance of quality control cannot be over-em- phasized thereby making it expedient on all flour mills that want to be competitive, remain in business and profitable need to appreciate quality’s contribution and be ready for investment in its personnel and operation.