Effect of Pretreatment of Fresh Amorphophallus paeoniifolius on Physicocochemical Properties of Scratch

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V.Sunitha Rani, Jancy K.John,
S.N.Moorthy and K.C.M.Raja,
Trivandrum (India)

Notes: Fresh roots of Amorphophallus paeoniifolius were separately pretreated with sodium hexametaphosphate (SHMP), potassium metabisulphite (KMS), sodium chloride (NaCL), and ammonium hydroxide (NH4OH) within a range of 1-5% (w/v) concentration and glyceryl monosterate (GMS) at 0.025-0.125% concentration. The quality of starch extracted from pretreated roots was compared with that obtained from fresh roots by direct aqueous extraction. The starch samples prepared from chemically pretreated roots showed characteristic changes in properties of water soluble amylase content, swelling and solubility and ά-amylase susceptibility. X-ray diffraction of starch samples from chemically pretreated roots although resembled that of control, there was noticeable shift with respect to their’d’ spacing and Io/Imax values.

Introduction

Edible tubers of tropical root crops viz. Dioscorea, Colocassia, Xanthosoma, Amorphophallus sp. etc. form and important food source [1, 2]. Although the major organic constituent of all the above crops is starch, accounting for 10-35% on fresh weight basis [3], extraction of starch does not often bring adequate yield. This is mainly due to the fact that tubers, unlike cassava, often contains constituents other than starch that interferes with the process of starch extraction. Similar problems arise also during extraction of starch from cereals. Hence, subjecting root/cereal crops to physico-chemical pretreatments is often practiced to enhance the starch yield [4]. Jawad and Lorenz [5] reported that steeping wheat of poor baking quality increased the starch yield as well as susceptibility to ά-amylase action. Hoover and Hadzijeve [6] had used sodium bisulphate during homogenization and extraction of starch from potato tubers, Lorenz and Kulp [7] are of the opinion that organization of starch is not fixed and could get altered by the conditions adopted for isolation. Addition of 0.01% sulphite enables release of polysaccharides reflecting on the swelling volume [8] of starch. Amorphophallus paeoniifolius being an important food crop grown in different parts of the country, and its starch having characteristics properties, extraction of starch in good yield without affecting the quality has great potential for better utilization [9,10]. Studies were, therefore, carried out to examine in detail, the effect of pretreating fresh tubers with a few selected chemicals on the yield and physicochemical quality of starch obtained.