Charles Parkouda

The microbiology of alkaline-fermentation of indigenous seeds used as food condiments in Africa and Asia

Alkaline-fermented food condiments play an important role in the diets of many people in developing and a few developed countries. The rise in pH during production of these foods is due to the ability of the dominant microorganisms, Bacillus spp., to hydrolyze proteins into amino acids and ammonia. Studies have been undertaken which have investigated a number of these products like dawadawa, ugba, bikalga, kinema, natto, and thua-nao. In this review, current knowledge about the principal microbiological activities and biochemical modifications which occur during the processing of the alkaline condiments including nutritional, antimicrobial, and probiotic aspects are discussed. The current use of molecular biology methods in microbiological research has allowed unambiguous and more reliable identification of microorganisms involved in these fermentations generating sufficient knowledge for the selection of potential starter cultures for controlled and better production procedures for alkaline-fermented seeds condiments.

Microorganisms associated with Maari, a Baobab seed fermented product

A microbiological study was carried out on Baobab fermented seeds (Maari) obtained from 4 different production sites in Burkina Faso (Mansila, Toulfé, Ouagadougou and Gorgadji). A total of 390 representative isolates comprising 251 aerobic mesophilic bacteria (AMB) and 139 lactic acid bacteria (LAB) were isolated and identified to species level using a combination of pheno- and genotypic methods including conventional morphological analysis, carbohydrate fermentation profiling, rep-PCR ((GTG)(5)-fingerprinting) and 16S rRNA gene sequencing. The fermentation of Baobab seeds was initiated by the AMB identified as Bacillus subtilis (82% of AMB isolates) and Staphylococcus sciuri (18% of AMB isolates). No lactic acid bacteria were isolated at the beginning of the process. After 24h fermentation time, Enterococcus faecium appeared in the fermenting seeds and remained until the end of the fermentation, as the predominant LAB. In Maari collected from retail outlets the AMB count ranged from 6.7log10CFU/g to 10log10CFU/g while the LAB load ranged from 4.4log10CFU/g to 9.9log10CFU/g. The AMB were identified as belonging to genus Bacillus (12 species), Staphylococcus (3 species) and one species of Aerococcus, Macrococcus, Leifsonia, Kurthia, Proteus, Acinetobacter and Globicatella, respectively. A putatively novel, previously undescribed Corynebacterium sp. was also found. E. faecium was the dominant LAB in all investigated retail samples except one sample dominated by Pediococcus acidilactici.

A research approach supporting domestication of Baobab (Adansonia digitata L.) in West Africa

The Baobab tree (Adansonia digitata L.) is a key multipurpose species for the African region. In the recent years there has been an extended commercial interest for different A. digitata products. As a spectacular African key species there has been a growing interest from NGO′s and various research groups. A research group, focussing on the following countries Burkina Faso, Mali and Niger, has participated in a concerted research action with cross counter disciplinary cooperation between plant physiology, population genetics, tree breeding, food science, and socioeconomics. This paper presents a review and the way knowledge gaps are being addressed using the above mentioned approach. The overall work was initiated in 2005–2006 when a large collection of A. digitata seeds was carried out in 15 African countries. Fourteen populations were selected in Burkina Faso, Mali, and Niger including more than 400 superior trees, and many of the trees have been selected along with farmers in a participatory process. Studies have been initiated in all countries on geographic variation of growth, adaptive and phenological traits. This includes studies in the nursery, establishment of international provenance series, seed orchards and studies of gene flow and phylogeographic variation with various markers. Specific nursery trials have been established in order to study provenance and progeny performance related to drought stress. Several stress related characteristics are being measured. Preliminary observations showed large morphological variation between African provenances of A. digitata. Food properties of plant parts have been studied within and between populations. This includes studies of total biomass production, vitamin A, B1, B2, and various minerals. The influence of stress will be related to these parameters. Fruits, which are rich in sugar and vitamin C, are used as an ingredient in juice and other foods. Seeds can be used directly as food ingredient or in fermented condition (Maari). The fermentation process was previously poorly described. Therefore, the microorganisms associated with Baobab seeds fermentation have been identified and a starter cultures for control production has been proposed. The efficiency of dissemination of superior A. digitata trees depends on vegetative propagation. Various grafting methods are currently being tested in cooperation with farmers. Micropropagation is tested as well as a method for clone propagation. The accumulated knowledge will be applied for a domestication strategy of A. digitata in Burkina Faso, Mali and Niger. The outcome from this study will be guidelines for protection and management of the germplasm of A. digitata resources.

The Use of Lactic Acid Bacteria Starter Culture in the Production of Nunu, a Spontaneously Fermented Milk Product in Ghana

Nunu, a spontaneously fermented yoghurt-like product, is produced and consumed in parts of West Africa. A total of 373 predominant lactic acid bacteria (LAB) previously isolated and identified from Nunu product were assessed in vitro for their technological properties (acidification, exopolysaccharides production, lipolysis, proteolysis and antimicrobial activities). Following the determination of technological properties, Lactobacillus fermentum 22-16, Lactobacillus plantarum 8-2, Lactobacillus helveticus 22-7, and Leuconostoc mesenteroides 14-11 were used as single and combined starter cultures for Nunu fermentation. Starter culture fermented Nunu samples were assessed for amino acids profile and rate of acidification and were subsequently evaluated for consumer acceptability. For acidification properties, 82%, 59%, 34%, and 20% of strains belonging to Lactobacillus helveticus, L. plantarum, L. fermentum, and Leu. mesenteriodes, respectively, demonstrated fast acidification properties. High proteolytic activity (>100 to 150 μg/mL) was observed for 50% Leu. mesenteroides, 40% L. fermentum, 41% L. helveticus, 27% L. plantarum, and 10% Ent. faecium species. In starter culture fermented Nunu samples, all amino acids determined were detected in Nunu fermented with single starters of L. plantarum and L. helveticus and combined starter of L. fermntum and L. helveticus. Consumer sensory analysis showed varying degrees of acceptability for Nunu fermented with the different starter cultures.