91A-11 |
Characterization of a heat stable alpha-amylase from Amazonian variety of cassava roots (Manihot esculenta Crantz) |
E. Matos-Veiga1, T. C. R. Pires2, F. FINARDI-FILHO3, and C. P. Magalhães2. (1) Universidade de Sao Paulo, Sao Paulo, 05508-900, Brazil, (2) Brazil, (3) Alimentos e Nutricao Experimental, Universidade de Sao Paulo, Av. Prof. Lineu Prestes, 580, Sao Paulo, 05508-900, Brazil The roots of cassava are important staple crop as well as a good source of starch for food industries. The cassava plants accumulate starch in the roots for years without apparent damages but has two weeks after harvest as a life time due to the action of endogenous and exogenous enzymes. For instance, amylases have no activity until the root are gathering to start the deteriorative process. The present investigation consists on the characterization of alpha-amylase extracted from the variety Zolhudinha (EMBRAPA - IM 158), cultivated in Amazonian area. This variety distinguishes from others due to its higher amylase activity. Aqueous extracts of cassava were submitted to heat treatment, pH variation, and addition of bivalent cations as well as EDTA to determine changes on the amylase activity. The hydrolysis of potato starch was measured by the reducing sugar formation with 3,5-dinitrosalicilic acid and by the changing the color of iodine complex. Native PAGE with 1% of soluble starch was used to detect the remaining amylase activity. Cassava’s alpha-amylase has a maximum activity at 60ºC, pH 6.0. According to the statistical treatment the optimum activity condition was 55.7ºC at pH 6.2. The enzyme presented also an inactivation at pH bellow 5.0; it was inhibited by Cu2+ and EDTA, and had its activity enhanced by the supplement of Ca+2 and Mg+2. The kinetic values were Km 9.24 mg/mL and Vmax 0.45 mg/mL/min. Thermal stability played a fundamental role in the isolation procedure employed, by heating the extract at 70ºC, for 10 minutes, passing through DEAE-cellulose matrix. The knowledge of the cassava´s endogenous amylase may be possible to prevent the root deterioration as well as to reduce the remaining starch pollution from the flour factories.
Session 91A, Food Chemistry: Enzymes, vitamins and plant pigments
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