Modern Industrial Microbiology and Biotechnology

Production of Fermented Foods 35119.5.1 GarriGarri is a popular food for about 100 miilion people in West Africa; in Cote d’Ivoire, atieke,a food very similar to garri, produced from cassava but is is not fried like garri. A similarfood known as farinha de manioc or farinha de mega is consumed in parts of Brazil.Preparation of Garri: Garri is currently prepared mostly on small, house-hold scales. Thefirst stage is the peeling to remove the brownish thin outer covering (Fig. 19.2) to reveal thewhite fleshy inner portion which is grated on a hand-held rasper or crushed in a gratingmachine. The central pith and primary xylem provide some fibers in the grated materialsome of which is removed by sieving, but which is appreciated by some garri consumers.Peeling ofCassava rootsGratingPalmAdded -oilOptionalBagging,Dewatering,Fermentation24–96 hoursSievingFryingSievingGARRIFig. 19.3Flow Chart of Garri ProductionThe mash resulting from the grating is placed in cloth bags for between 18 and48 hours and fermented. During the period of fermentation, the mash is dewatered byplacing heavy objects on the cloth bags. At the end of the fermentation period, the mash issieved through a coarse sieve and heated, sometimes with a little palm oil, in a flat ironpot with stirring.Microbiology of the fermentation of Garri: In 1959 Collard and Levi published their studyon the two-stage fermentation of cassava pulp. In the first stage which lasted for the first48 hours a yellow-pigmented bacterium, Corynebacterium manihot, proliferated. Thisorganism broke down starch eventually to organic acids including lactic acid. Theresulting drop in pH led to the spontaneous breakdown of the linamarin and theproliferation of the fungus Geotrichum candidum which produced the flavoringaldehydes, ketones and other compounds. In 1977 Okafor re-examined fermenting pulpand while there he found some Corynebacterium, the bulk of the organisms were lacticacid bacteria, especially Lactobacillus, Leuconostoc and and yeasts. He suggested theabsence of lactic acid bacteria in the work of Collard and Levi was probably because theyused nutrient agar, a medium lacking sugars in which lactic acid bacteria grow better.Furthermore, linamarin is fairly stable and the glucoside is probably broken down moreby the indigenous linamarase of the enlarged roots, which is released when the roots arecrushed than by a change of pH. Other workers have since confirmed the importance oflactic acid bacteria and yeasts in the fermentation of cassava during garri production.The current thinking on the microbiological processes of cassava fermentation forgarri production is that when cassava roots are grated to produce the mash which isbagged and fried to produce garri, the indigenous linamarase present in the roots isreleased and makes contact with the cyanogenic glucosides in the roots. The glucosides,