Abstract

---

Garri is a granular pre-gelatinized cassava starch with slightly fermented flavour and slightly sour taste made from grated, fermented fresh cassava tubers. It serves as staple food in many parts of Nigeria. This work studied the effect of fermentation and palm oil on the nutritional compositions of garri produced by traditional fermentation Method (TFM) and Instant Mechanical Method (IMM). Cassava tubers of TME 419 variety were used to produce garri using the two methods and with addition of palm oil to the bag before dewatering and the pot during toasting. For garri processed by TFM, the cassava tubers were peeled with knife, washed with tap water and grated. The cassava mash produced was allowed to stay for 24 hours in a bag before it was dewatered using heavy woods. It was allowed to ferment in the bag for 96 hrs and then toasted. For the garri produced by IMM, the cassava tubers were peeled with knife, washed with tap water and grated. The cassava mash produced was not allowed to ferment but was dewatered using heavy woods after grating and then toasted. The microbial load of the garri mash from both the TFM and IMM was determined by inoculating 0.1 ml aliquots of serially diluted cassava mash in triplicate to appropriate media. For the isolation of bacteria, 0.1 ml aliquots was inoculated by spread plate method on sterile Nutrient, MacConkey, Salmonella-Shigella, Mannitol Salt and and De Mann Rogosa Sharpe Agar plates and incubated for 48 hrs at 35oC. For isolation of fungi, 0.1 ml aliquots were inoculated on Sabouraud Dextrose Agar (SDA) and incubated for 5 days at 22oC. The colonies formed from both groups of isolates were sub-cultured on the same media and characterized through biochemical and sugar fermentation tests. The nutritional composition of the garri sample was determined using standard procedures. Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, Salmonella typhimuriun, Shigella dysentriae, Lactobacillus fermentum and Leuconostoc mesenteriodes were the bacteria isolated from the grated cassava mash during fermentation while the fungal isolates are Aspergillus niger, Fusarium solani, Penicillium notatum and Saccharomyce cerevisiae. The highest bacterial load from the IMM (3.50 x 105 cfu/g) was from cassava mash without palm oil while the least (1.87 x 105 105 cfu/g) was from the mash mixed with palm oil before toasting. The highest bacterial load (2.60 x 105 CFU/g) from mashes produced using TFM was from the mash produced without palm oil while the lowest value (1.80 x 105 CFU/g) was from the mash to which palm oil was added during toasting. After fermentation, only Bacillus, Lactobacillus and Leuconostoc species were isolated while S. cerevisiae was the only fungus isolated. The garri produced from cassava that was fermented had a significantly higher carbohydrate and fats contents (87.29 and 3.07 respectively) than that produced by IMM. Addition of palm oil and the time of addition had no significant effect (P<0.05) on the protein, fibre and ash contents of the garri produced through fermentation. There was a significant reduction in hydrogen cyanide content of the garri samples produced through fermentation compared with the garri produced by IMM. In conclusion, the garri produced through fermentation has no pathogen/food spoilage organism in it. The hydrogen cyanide content was found to be reduced to tolerable limit and it has higher carbohydrate content.

Keywords: Cassava tubers, food safety, garri, microorganisms, nutritional composition, traditional fermentation