Browsing by Author "Thorsen, L."
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Item The microbiology of alkaline-fermentation of indigenous seeds used as food condiments in Africa and Asia(Critical Reviews in Microbiology, 2009-02) Parkouda, C.; Nielsen, D.S.; Azokpota, P.; Ivette Iréne Ouoba, L.; Amoa-Awua, W.K.; Thorsen, L.; Hounhouigan, J.D.; Jensen, J.S.; Tano-Debrah, K.; Diawara, B.; Jakobsen, M.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.Item Microorganisms associated with Maari, a Baobab seed fermented product(International Journal of Food Microbiology, 2010-09) Parkouda, C.; Thorsen, L.; Compaoré, C.S.; Nielsen, D.S.; Tano-Debrah, K.; Jensen, J.S.; Diawara, B.; Jakobsen, M.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 24. h 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 6.7. log10. CFU/g to 10. log10. CFU/g while the LAB load ranged from 4.4. log10. CFU/g to 9.9. log10. CFU/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. © 2010 Elsevier B.V.Item Reducing the atypical odour of dawadawa: Effect of modification of fermentation conditions and post-fermentation treatment on the development of the atypical odour of dawadawa(Food Control, 2014-08) Amoa-Awua, W.K.; Awusi, B.; Owusu, M.; Appiah, V.; Ofori, H.; Thorsen, L.; Jespersen, L.Dawadawa, an indigenous African alkaline fermented condiment has a distinct atypical odour which is often described as strong, pungent, and ammoniacal, but sometimes also as unpleasant, undesirable, objectionable, offensive. To improve the marketability of dawadawa, procedures capable of reducing the atypical odour were assessed. These were addition of humectants, NaCl (1.5mol/kg) and glycerol (1.7mol/kg), or irradiation by gamma radiation (2.5kGy) partway through fermentation, and also steaming of the fermented product. The sensory profiles of the products were determined by Quantitative Descriptive Analysis (QDA). Changes in microbiological and chemical characteristics were monitored on Nutrient Agar, and by measurement of pH, titratable acidity, proximate composition, and elemental analysis by atomic absorption spectrophotometry. All treatments applied significantly reduced the population of Bacillus species and also pH during fermentation. The pH at end of fermentation for the control was 8.9, NaCl-treated sample 7.6, glycerol-treated sample 7.5, and irradiated-sample 7.3 indicating suppression of ammonia formation which is responsible for the rise in pH and pungent odour in dawadawa. Steaming for 25min also resulted in loss of ammonia as indicated by slight reduction in pH from 8.8 to 8.3. Apart from the ash content, significant differences were observed in the concentration of protein, fat, carbohydrate, Fe, Mn, Zn, Na, K and Cu in most of the treated samples in comparison to the control. Odour descriptors generated by the semi-trained panel for dawadawa were ammoniacal, stink fish, faecal, urine, old smoked fish, marmite, shea butter, rancid palm kernel oil, corned beef, beany, and damp cocoa beans. In two sets of QDA, the control scored higher intensities for the undesirable descriptors, ammoniacal, faecal, stink fish and urine than the treated samples. In a difference from-control-test based on intensity of undesirable descriptors a semi-trained panel scored 5.61 for steamed-sample, 6.11 for irradiated-sample, 7.17 for NaCI-treated sample, and 7.5 for glycerol-treated sample on a scale of zero (no difference) to ten (extreme difference). © 2014 Elsevier Ltd.