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Development of a blue starch/agarose gel method for rapid intake and field testing for cereal alpha-amalase activity

HGCA PROJECT REPORT 271

Development of a blue starch/agarose gel method for rapid intake and field testing for cereal alpha-amalase activity

by

D G Bhandari

Campden & Chorleywood Food Research Association, Chipping Campden, Gloucestershire, GL55 6LD

January 2002

Abstract

The aim of this one-year project was to produce a rapid test for assessing levels of alpha-amylase in wheat and barley grains. The principal requirement of such a test is that it would be suitable for use at mill intake, in grain stores and in the field. Ideally, the new diagnostic test would be simple, effective and affordable, and thus provide an alternative to the WheatRiteTM kit that has, so far, not gained widespread acceptance in the UK.

The Strip Test has been developed to address these needs of the home-grown cereals industry. This new test is based on a recent CCFRA innovation, the test displays a blue coloration on the white strip, and the intensity is directly related to the rate ofhydrolysis of the Phadebas substrate by alpha-amylase extracted from wheat flour. The performance of the device was evaluated under laboratory conditions with a total of 125 stored samples of ground wheat from the 1999 and 2000 HGCA Cereal Quality Surveys, and whose HFN (Hagberg Falling Number) values were established. The alpha-amylase activity within these samples was measured by the Ceralpha (Megazyme) test method. The blue coloration produced on the white strips was judged visually by two independent observers, and the intensity noted according to the scoring system:


0 - no colour; 1- very faint blue; 2 - slightly blue; 3 - moderate blue; 4 - dark blue.


The two sets of samples were evaluated on two separate occasions using the Strip Test. Overall, there was good agreement between the two observers and the duplicate evaluations. The results showed that all the samples with HFN value of less than 210 gave a detectable blue colour, i.e. were given a score of 1 or more. The performance of the new test was found to be marginally better when compared with Ceralpha results, than with HFN data. While the test in its present form lacks precision in assessing samples with HFN values between 190 and 250, it is effectively able to indicate whether alpha-amylase activities in wheat samples are either high or low. This would be most useful for screening purposes. The Strip Test is not suitable for assessing barley samples owing to a loss of sensitivity found when dealing with barley extracts. This is probably due to presence of high levels of ß-glucans, which interfere with the assay.

HGCA Project Number: 2349
Price: £5.00

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