Effect of Wood Ash in the Preparation of “Soumbala” from Parkia biglobosa Seeds

Aims: Evaluation of the biochemical and microbiological characterization of Parkia biglobosa seeds added with wood ash during the fermentation for the preparation of "soumbala" (traditional condiment used across West Africa).

Study Design: Food safety

Methodology: 32 soumbala samples due to eight samples per commune were collected in the markets of Dimbokro (city in the center of Côte d'Ivoire) and three communes from Abidjan district, namely Adjamé, Abobo and Cocody. Also, 5 kg of Parkia biglobosa seeds divided into 14 samples were collected on Adjamé’s market. The loads of microorganisms (mesophilic aerobic germs, lactic acid bacteria, Bacillus, yeasts and moulds) were determined by counting after culture in agar medium. The physico-chemical composition (pH, titratable acidity and soluble sugars) of Soumbala and Parkia bigloboda seeds has been determined according to standard methods.

Results: The results of physico-chemical analyses showed that the pH varied from 5.53 to 7.95 for the control and from 8.2 to 8.6 for the "soumbala" produced in the presence of ash during 72 hours of fermentation, while that of the commercial "soumbala" was between 6.4 and 7.7. The protein, reducing sugar and fat contents increase while the dry matter and total carbohydrate contents of the seeds decrease during the fermentation process. Microbiological analyzes showed that the Bacillus loads varied from 5.2 to 9.9 log (CFU/g) for the control and 4.2 to 10.9 log (CFU/g) with the addition of wood ash with a respective optimum of 60 hours, those of lactic acid bacteria varied respectively by 2.3 log (UFC/g) and 3.1 log (UFC/g) in the control and supplemented with wood ash to reach an optimal load similar of 5.5 log (CFU/g). Yeast and mold loads varied from 2 to 5.2 log (CFU/g) for the control and from 3 to 4.5 and 5.6 log (CFU/g) respectively with the addition of wood ash. Bacillus was the only microorganism with the highest load both in commercial soumbala [10.2 log (CFU/g)] and in laboratory-produced soumbala [9.7 log (CFU/g)].

Conclusion: Wood ash had a enhancing effect on the fermentation of Parkia biglobosa seeds where Bacillus are in the majority. "Soumbala" produced in the laboratory were free of lactic acid bacteria and fungi at the end of fermentation.