Cassava Fermentation and Associated Changes in Physicochemical and Functional Properties

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S.N. Moorthy and George Mathew

Division of Crop Utilization and Biotechnology, Central Tuber Crops Research Institute, Sreekaryam, Trivandrum – 695 017, INDIA.

Referee : Professor Blanshard, Department of Applied Biochemistry and Food Science, University of Nottingham, Loughborogh, LE 12 5RD UK.

Abstract

Fermentation of cassava is an important processing technique followed in different parts of the world. Although fermentation is known to bring about vast changes in the physicochemical and functional properties of the tubers, attempts have seldom been made to consolidate and critically analyze the available information. Glaring inconsistencies and contradictions noticeable in some of the results reflect the differences and variation in the artisanal processes followed in the preparation of these products. It also stresses the need for systematic study of not only the quoted products, but also a number of other fermented cassava products and have not been well documented.

Keywords : Fermented cassava products, physicochemical and functional properties, antinutrients, starch characteristics.

I. Introduction

Cassava is an important tropical crop valued for its tuberous roots. The tubers contain 20 to 25% starch and very minor quantities of proteins, fats, and other biochemical constituents.4-7 The importance of cassava (Manihot esculenta Crantz) to the teeming millions lies on more than one score. On an energy production basis, cassava, providing nourishment to 500 million people, ranks foruth after rice, wheat, and maize. T he crop is relatively efficient producer even under adverse conditions such as erratic low rainfall and low soil fertility. Higher efficiency of energy production, less labour required per calorie harvested, and a great degree of flexibility in the timing of labor inputs are other major facets of convenience in this crop.3 However, quick perishability, low protein content, and the presence of toxic cyanogenic glocosides in the tubers and considered to be unfavorable aspects that demand efficient post-harvest processing for the crop.

Cassava is consumed in a number of ways and the mode of consumption varies from country to country. The normal processing techniques include cooking in boiling water, chipping and drying, parboiling roasting, and conversion to other food forms after extraction of starch or powdering into flour. Another mode of processing is subjecting the tubers to fermentation and subsequent conversion to different products. Gari, Fufu, Placali, Farinha from the African continent, Pande yucca, Pande bono, polvilho azedo from Latin America, and Tape Katella from the Far East countries are some of the fermented cassava products.1,8 In addition, many other minor food products are produced in other parts of the world. Cassava fermentation, as practiced, uses wide range of microbes,10-14 (lactic acid bacteria to yeast and mold); varied conditions14-16 (solid state to submerged anaerobic), and periods17,18 (overnight to weeks and months together) making available innumerable food products and alcoholic beverages.

First of all, fermentation helps to reduce the toxic principle cyanoglucoside present in tubers.19-23 It also improves the flavor and taste and is helpful in increasing the shelf life of cassava products. The functional properties of starch are also modified to suit to different applications. The diverse methods of fermentation practiced in different countries and the multiplicity of products produced make it difficult to generalize the biochemical changes accompanying the fermentations. The effect of fermentation on cyanide detoxification has probably been the major subject of study by most workers so that the other biochemical changes have not been highlighted to a desirable extent. This review focuses on the biochemical changes accompanying the different fermentation techniques and the changes in functional properties of fermented starch and starch extracted from tubers subjected to different types of fermentations.