Summary / Résumé du plan de recherche


Research Background and Justification

General Objectives

Specific Objectives

Experimental design

Optimierung der fermentativen Verarbeitung von Maniok zu Attiéké durch den Einsatz einer Starterkultur in einem standardisierten Herstellungsverfahren

Die Arbeit wurde im März 2004 abgeschlossen. Die Arbeit wird über die elektronische Bibliothek der ETH zur Verfügung gestellt, wo der Abstract bezogen werden kann. Die ganze Dissertation kann über info@cassava.ch bezogen werden.


Cassava (Manihot esculenta Crantz) is a high-biomass, low protein, high-energy producing tuber crop consisting mainly of starch. Africa, one of the largest producer worldwide, produces over 50 million tons annually.Traditionally, cassava roots are processes by a variety of methods. Fermentation is the favourite method for detoxification of Cassava, as well as for improvement and stabilisation of the products. Primarily, understanding of the traditional, established processing technology is required. Secondly, optimisation of the fermentation process and development of novel starter cultures will be attempted. And finally, implementation of the cultures under field conditions is planned.

The aim of this project is the improvement of quality and storage stability of fermented cassava products.

Résumé du plan de recherche

Le manioc (Manihot esculenta Crantz) est une haut-biomasse, basse protéine, collecte productrice de grande énergie de tubercule consistant principalement en amidon. L`Afrique, l`un des plus grand producteurs du monde, produit annuellement plus que 50 millions de tonnes.Traditionnellement, des tubercules de manioc sont traités par des méthodes variées. La fermentation est la méthode favorite pour la désintoxication du manioc, aussi bien que pour l`amélioration et la stabilisation des produits.Principalement, la compréhension de la technologie de transformation établie de manière traditionnelle est exigée. Deuxièmement, l`optimisation du procédé de fermentation et le développement des cultures d`amorV age de ramon seront essayés. Et en conclusion, la mise en place des cultures sur le terrain est projetée.

Le but de ce projet est l`amélioration de la qualité et de la stabilité de stockage des produits fermentés de manioc.


Cassava (Manihot esculenta Crantz) was introduced into Central Afrika from South Amerika in the 16th century by Portugese settlers. It has spread out throughout Sub-Saharan Africa and became one of the dominant starchy staples in the people diet (Nwenke, 1994).

Cassava is a high-biomass, low protein, high-energy producing tuber crop consisting mainly of starch, which belongs to the family of Euphorbiaceae. The plant is extremely tolerant to climatic stress, is mainly cultivated in the humid tropics and is available throughout the year. Africa as one of the largest producer worldwide produces over 50 million tons of cassava annually (FAO, 1999).

Traditionally, cassava roots are processed by a variety of methods into different products, depending on local customs and preferences. The roots are usually fermented during preparation, spontaneously or with starter cultures. Fermentation is the favourite method for detoxification of cassava since the plant naturally contains cyanogenic glycosides, as well as for improvement and stabilisation of nutritional and organoleptic quality of the products.

Research Background and Justification

Cassava plays an important role because drought, war, political instability, rural – urban migration and falling per capita food production have contributed to growing food import dependency scenarios. Internal financial liquidity, stagnating production and population growth are obvious consequences. On the other hand famine rarely occurs in areas where cassava is widely grown, since it provides a stable base to the food production system. This indicates that cassava has the potential for eliminating food crises and famine.

A large project focussing on cassava was started in 1989, when the Organisation of Collaborative Study of Cassava in Africa (COSCA) was funded by the Rockefeller Foundation. The study, which is still under way, aims to collect authoritative information over a wide area on cassava production systems, processing methods, marketing prospects and impact of agricultural research on the crop in order to realise the potential of cassava in increasing food production and incomes of the people of Africa.

Cassava is consumed mainly in fermented forms. Gari and Attiéké are the main fermentation products produces in cassava growing countries in Africa. Gari is produced an widely consumed in Nigeria and Attiéké in Côte d’ Ivoire. Attiéké, steamed cassava granules, is a traditional dish, which has been adapted and verified by numerous ethnical groups in Côte d’ Ivoire. Amelioration of this product is a novel approach in optimisation food safety in Africa and therefore in accordance to guidelines for developmental collaboration of the ETH Zurich.

In the past, several studies were published concerning the identification of microorganisms associated with cassava lactic fermentation. Lactic fermentation is a rapid acidification in absence of oxygen associated with the production of organic acids (lactate and acetate) by lactic acid bacteria (Agbor, 1995). Two different types of cassava fermentation are common, submerged and mash fermentation. In submerged fermentation roots are steeped in water for a period of 3 or 5 days and further prepared for consumption (Bokanga, 1989; Nwankwo et al., 1989; Okafor et al., 1984). In mash fermentation, the mash is obtained by grating fresh roots and is left to ferment for several days (Okafor and Uzuegbu, 1987; Abe and Lindsay, 1978). Fufu (Foufou) and Placali were used for study of submerged fermentation and gari and Attiéké for study of mash fermentation (Bokanga, 1992).

In the fermentation homofermentative organisms occurred most frequently in early stages and heterofermentative in the later ones (Westby and Twiddy, 1992). Predominant organisms isolated were bacteria, mainly Lactobacillus, Leuconostoc, Alcaligenes and Corynebacterium and to a lesser extent yeasts, mainly Candida spp. (Okafor, 1977).

The microflora of the inocula contained a high counts of lactic acid bacteria. Lactobacillus plantarum was the dominant species of lactic acid bacteria. McDonald (1990) and Giraud (1993) suggested that Lactobacillus plantarum could be used as a suitable starter for cassava fermentation due to high biomass yield, strong linamarase and amylase activities, low growth limiting internal pH and ability to maintain a pH gradient at high organic acid concentration.

The main emphasis of the present study is understanding and improving of fermentation process of Attiéké in Côte d’Ivoire where most of cassava is consumed in this form.

The processing of Attiéké includes peeling the roots, washing and grinding them to a mash. Cooked and fermented cassava pulp is added before grinding as a starter culture for the fermentation The product is fermented for 3 days and as much water as possible is squeezed out. The dewatered mash is granulated, sun dried and steam–cooked until the moisture is about 30 – 40 %.

Due to its high water content Attiéké is a perishable product and moulds, yeasts and bacteria are growing readily after 3 – 4 days at room temperature. This is a serious problem for producers and consumers as the demand of Attiéké is increasing due to growing urban population.

General Objectives

Improve the quality and shelf–life of the traditional fermented Cassava products in West Africa on the basis of existing knowledge in collaboration with local producers.

Specific Objectives

  • Collection of scientific data on existing Attiéké production and processing methods in Côte d’Ivoire.
  • Study the microflora of Attiéké and development of standard starter cultures which can be used for manufacturing of fermented products of high hygienic quality and long shelf–life.
  • In collaboration with local partners, the improved Attiéké techniques will be tested under field conditions and introduced in Côte d’Ivoire.

Experimental design

The main analytical laboratory work will be carried out in the Institute of Food Science at the ETH Zürich. A first field mission to Côte d’ Ivoire will be take place in September 2000. The aim will be to obtain first information about processing technology and to collect samples.

The experimental steps will be as following

  • Obtain a general idea how the cassava transformation into fermented products is working at traditional and medium size levels in terms of processing, techniques, market, storage, etc.
  • Decide whether the study should focus on one ethnical group or whether different groups are selected for samples collection
  • Compare different ways of product processing by interviewing of house wives who are responsible for preparation of food using traditional processing methods
  • Collect samples from different production steps for analysis
  • Carry out first product analyses in terms of pH, temperature, moisture, microbiological and other factors like taste and rheological properties
  • Develop standard starter cultures
  • Implement new cultures under field conditions in Côte d’Ivoire
  • Examine new products qualitatively and adapted processing in terms of sensory quality, chemical analysis and usefulness
  • Improve storage stability