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Lookup NU author(s): Dr Gerry O'BrienORCiD
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Effects of repeated freeze-thaw stresses on the activity of cassava linamarase enzyme preparations lyophilized with different protectant compounds Phoebe W.S. Liu[1], Archie McKinley[2], Teresa Sanchez[3], Hernan Ceballos[4] and Gerard M. O’Brien[5] Cassava roots are a major dietary carbohydrate source for many millions of people in Developing Countries. Roots of many so-called “bitter” varieties are of sufficiently high cyanogenic potential (CNP) to pose a threat to human health. Consequently, the routine testing of cassava root CNP is important. The enzymatic colorimetric assay of CNP originally developed by Cooke is a routinely-used accurate and reliable assay method that involves subjecting cassava sample extracts to exogenous partially-purified cassava linamarase enzyme, which must be of at least 3 EU / ml activity. As with other costly reagents, it is common practice for left-over linamarase enzyme to be retained and frozen for future use: a given preparation may be subjected to several freeze-thaw cycles before it is used up. The main aim of this study was to investigate the effects of a series of freeze-thaw cycles on the activity of lyophilized, reconstituted linamarase preparations, and also to compare the effectiveness of three commonly-used protectant sugars (trehalose, sucrose and lactose), at 10% and 20% concentrations, during this freeze-thaw series. Using root peel of cassava cultivar M Per 183, triplicate batches of linamarase containing each protectant / concentration combination, and an unprotected enzyme “control”, were prepared and lyophilized. The preparations were reconstituted and subjected to 10 successive freeze-thaw cycles, with linamarase activity assayed at each cycle. At no stage did the mean activity of the unprotected “control” preparation drop by more than 3% relative to its starting value at cycle no. 1. While most protectant-containing preparations also performed well, none performed significantly better (p < 0.05) than the unprotected “control” in any cycle. On the basis of the evidence, it is concluded that partially-purified linamarase enzyme from cassava cultivar M Per 183 is highly resistant to freeze-thaw stress, and requires no protectant during at least 10 freeze-thaw cycles. [1] (BSc Hons); Swire Coca Cola Hong Kong Ltd., Shatin, N.T., Hong Kong. Tel:+852-2636-8549; e-mail: phoebeliu@swirebev.com [2] (DPhil.); School of Environmental Sciences, University of Ulster, Coleraine, N. Ireland. Tel: +44-28-7012-4570; e-mail: a.mckinley@ulster.ac.uk [3](MSc); Centro Internacional de Agricultura Tropical, A.A.6713 Cali, Colombia. Tel:+57-2-445-0000; e-mail: tsanchez@cgiar.org [4] (PhD); Centro Internacional de Agricultura Tropical, A.A.6713 Cali, Colombia. Tel:+57-2-445-0000; h.ceballos@cgiar.org [5] (PhD); Newcastle University Singapore, 180 Ang Mo Kio Avenue 8, Singapore 569830. Tel: +65-6550-1969; e-mail: gerard.o’brien@ncl.ac.uk
Author(s): Liu PWS, McKinley A, Sanchez T, Ceballos H, O'Brien GM
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: ASEAN Food Conference 2015
Year of Conference: 2015
Acceptance date: 10/05/2015
