Browsing by Author "Jespersen, L."
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Item Identification of lactic acid bacteria isolated during traditional fura processing in Ghana(Food Microbiology, 2012-10) Owusu-Kwarteng, J.; Akabanda, F.; Nielsen, D.S.; Tano-Debrah, K.; Glover, R.L.K.; Jespersen, L.Fura is a millet-based spontaneously fermented dumpling produced and consumed in parts of West Africa, particularly Nigeria, Burkina Faso and Ghana. From eight traditional fura production sites in northern Ghana, 862 lactic acid bacteria were isolated and identified to species level using a combination of genotypic and phenotypic methods including (GTG)5-based PCR fingerprinting and 16S rRNA gene sequencing, multiplex PCR by means of recA gene sequence comparison, conventional morphological characteristics and carbohydrate fermentation profiling. During millet dough fermentation, pH decreased from 5.6-6.4 to 4.1-3.7 and total lactic acid bacteria (LAB) counts increased from 4.4-5.3 to 7.9-9.2 log10 (cfu/g). The initial stages of the fermentation were characterized by co-dominance of homo- and heterofermentative species of Pediococcus acidilactici, Weisella confusa, Lactobacillus fermentum, Lactobacillus reuteri, Lactobacillus salivarius, and Lactobacillus paraplantarum whereas L. fermentum was dominating at the end of the fermentation. L. fermentum was predominant in all fermentations (p < 0.05) and a high uniformity was observed among production sites regarding the dominance of L. fermentum. L. fermentum and W. confusa were isolated in all production sites and almost at all fermentation stages indicating that they are indigenous to traditional fura processing. The other LAB bacteria species which comprised a minor proportion of the total LAB occurred occasionally and in an irregular pattern among the production sites. © 2012 Elsevier Ltd.Item Lactic acid tolerance determined by measurement of intracellular pH of single cells of Candida krusei and Saccharomyces cerevisiae isolated from fermented maize dough(International Journal of Food Microbiology, 2004-07) Halm, M.; Hornbæk, T.; Arneborg, N.; Sefa-Dedeh, S.; Jespersen, L.Strains of Candida krusei and Saccharomyces cerevisiae were grown together at 30°C in MYGP broth, pH 2.5, in the presence of 106.4 mM undissociated lactic acid. The two C. krusei strains investigated grew within 48 h from initial counts of 2×104 to approximately 107 cells/ml whereas the two S. cerevisiae strains investigated survived but did not grow in the presence of 106.4 mM undissociated lactic acid at pH 2.5. To explain the differences in lactic acid tolerance of the two yeast species, we used fluorescence-ratio-imaging microscopy and a perfusion system to determine the short-term intracellular pH (pHi) changes in single cells of C. krusei and S. cerevisiae. The changes were investigated both in the presence of low (20.7 mM) and high (106.4 mM) concentrations of undissociated lactic acid. For both the investigated species 20.7 mM undissociated lactic acid did not seem to influence the initial pHi which for C. krusei was found to be approximately 8.0 and for S. cerevisiae 6.9-7.5. For both C. krusei strains, perfusion with 106.4 mM undissociated lactic acid induced only weak short-term pHi responses with a decrease in pHi of less than one pH unit. Contrary, for both strains of S. cerevisiae perfusion with 106.4 mM undissociated lactic acid resulted in a significant decrease in pHi from initially 6.9-7.5 to 6.2-6.4 after 1 min and further to a pHi of ≤5.5 after 3 min after which it remained constant. The results obtained show that C. krusei is more resistant to short-term pHi changes caused by lactic acid than S. cerevisiae, and this, in turn, may be part of the explanation why C. krusei is more tolerant to lactic acid than S. cerevisiae. © 2004 Elsevier B.V. All rights reserved.Item Molecular Diversity and Technological Properties of Predominant Microorganisms Associated with the Processing of Millet into Fura, A Fermented Food in Ghana(University of Ghana, 2013-12) Owusu-Kwarteng, J.; Tano-Debrah, K.; Jespersen, L.Fura is a millet-based spontaneously fermented dumpling produced and consumed in parts of West Africa, particularly Nigeria, Burkina Faso and Ghana. From eight (8) traditional fura production sites in northern Ghana, lactic acid bacteria (LAB) and yeasts were isolated, characterized and identified using genotypic methods. These included (GTG) 5 -based rep-PCR fingerprinting, sequencing of the 16S rRNA gene, multiplex PCR by means of recA gene sequence comparison and sequencing of D1/D2 region of 26S rRNA genes. Following identification, the predominant LAB were assessed for some technological properties including rates of acidification, exopolysaccharide production, amylase production and bacteriocin activities. The identified yeasts were also assessed for their probiotic potential by measuring tolerance to low pH (2.5), bile salt (0.3% oxgall) and temperature (37°C). Based on the genotypes, the LAB species associated with fura processing include L. fermentum (40.8%), W. confusa (19.0%), L. reuteri (13.9%), P. acidilactici (11.8%), L. salivarius (8.1%) and L. paraplantarum (6.3%). L. fermentum predominated in all fermentations (p< 0.05) and uniformity was observed among production sites regarding the dominance of L. fermentum. L. fermentum and W. confusa were isolated in all production sites and almost at all fermentation stages indicating that they are indigenous to traditional fura processing. The yeast species identified include Candida krusei (60%), Kluyveromyces marxianus (38%), Candida tropicalis (0.6%), Candida rugosa (0.2%), Candida fabianii (0.4%), Candida norvegensis (0.6%) and Trichosporon asahii (0.4%). C. krusei and K. marxianus were found to be the dominant species throughout the fermentation and were isolated from all production sites. Generally, majority of predominant LAB strains showed faster acidification rates, high exopolysaccharides production and the ability to inhibit pathogens through the production of bacteriocins. Yeasts isolated from fura survived and grew at human gastrointestinal conditions of pH 2.5 and 0.3% (w/v) oxgall at 37°C over 4 h duration. Additionally, strains of C. krusei, K. marxianus, C. rugosa and T. asahii were able to increase the relative TEER of Caco-2 monolayers after 48 h, making them possible candidates for the development of starter/co-cultures with probiotic potentials. The study has shown the diversity of microorganisms associated with fura processing. It has also revealed the technological properties of the microorganisms that impact on the product and therefore provided the basis for development of starter cultures.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.Item Taxonomic and molecular characterization of lactic acid bacteria and yeasts in nunu, a Ghanaian fermented milk product(Food Microbiology, 2013-06) Akabanda, F.; Owusu-Kwarteng, J.; Tano-Debrah, K.; Glover, R.L.K.; Nielsen, D.S.; Jespersen, L.Produced from raw unpasteurized milk, nunu is a spontaneously fermented yoghurt-like product made in Ghana and other parts of West Africa. Despite the importance of nunu in the diet of many Africans, there is currently only limited information available on the microorganisms associated with nunu processing. With the aim of obtaining a deeper understanding of the process and as a first step towards developing starter cultures with desired technological properties for nunu production, a microbiological characterization of nunu processing in three different towns in the Upper East region of Ghana, namely Bolgatanga, Paga and Navrongo, was carried out. Lactic acid bacteria (LAB) and yeasts associated with nunu processing were isolated and identified using a combination of pheno- and genotypic methods including morphological and carbohydrate fermentation tests, (GTG)5-based rep-PCR, multiplex PCR, and 16S and 26S rRNA gene sequencing. The LAB counts during nunu processing increased from 4.5 ± 0.4 log cfu/ml at 0 h to 8.7 ± 1.8 log cfu/ml at 24 h of fermentation while yeasts counts increased from 2.8 ± 1.2 log cfu/ml at 0 h to 5.8 ± 0.5 log cfu/ml by the end of fermentation. Lactobacillus fermentum was the dominant LAB throughout the fermentations with Lactobacillus plantarum and Leuconostoc mesenteroides playing prominent roles during the first 6-8 h of fermentation as well. Less frequently isolated LAB included Lactobacillus helveticus, Enterococcus faecium, Enterococcus italicus, Weissella confusa and a putatively novel Lactococcus spp. The yeasts involved were identified as Candida parapsilosis, Candida rugosa, Candida tropicalis, Galactomyces geotrichum, Pichia kudriavzevii and Saccharomyces cerevisiae with P. kudriavzevii and S. cerevisiae being the dominant yeast species. © 2012 Elsevier Ltd.Item Technological properties and probiotic potential of Lactobacillus fermentum strains isolated from West African fermented millet dough(2015-11-11) Owusu-Kwarteng, J.; Tano-Debrah, K.; Akabanda, F.; Jespersen, L.Abstract Background Throughout Africa, food fermentations are still driven by indigenous microorganisms which influence the nutritional, organoleptic and safety of the final products. However, for improved safety, consistent quality and beneficial health effects, a trend has emerged which involves the isolation of indigenous strains from traditional fermented products to be used as functional starter cultures. These functional starter cultures possess inherent functional characteristics and can contribute to food quality and safety by offering one or more organoleptic, nutritional, technological or health advantage (probiotics). With the aim of selecting potential probiotic starter cultures, Lactobacillus fermentum strains isolated from fermented millet dough were investigated for technological properties and probiotic traits in-vitro. Results A total of 176 L. fermentum strains were assessed for technological properties including rate of acidification, exopolysaccharide production and amylase activity. Following this, 48 strains showing desirable technological properties were first screened for acid resistance. Sixteen acid resistant strains were assessed for additional probiotic properties including resistance to bile salts, bile salt hydrolysis, antimicrobial property, haemolysis and antibiotics resistance. L. fermentum strains clustered into 3 groups represented by 36 %, 47 % and 17 % as fast, medium and slow acidifiers respectively. About 8 %, 78 % and 14 % of the strains showed strong, weak and no exopolysaccharides production respectively. Amylase activity was generally weak or not detected. After exposure of 48 L. fermentum strains to pH 2.5 for 4 h, 16 strains were considered to be acid resistant. All 16 strains were resistant to bile salt. Four strains demonstrated bile salt hydrolysis. Antimicrobial activity was observed towards Listeria monocytogenes and Staphylococcus aureus but not E. coli and Salmonella enteritidis. Lactobacillus fermentum strains were generally susceptible to antibiotics except 6 strains which showed resistance towards streptomycin, gentamicin and kanamycin. Conclusion In vitro determination of technological and probiotic properties have shown strain specific difference among L. fermentum strains isolated from fermented millet dough. Sixteen (16) L. fermentum strains have been shown to possess desirable technological and probiotic characteristics in vitro. These strains are therefore good candidates for further studies to elucidate their full potential and possible application as novel probiotic starter cultures.Item Technological properties and probiotic potential of Lactobacillus fermentum strains isolated from West African fermented millet dough(BMC Microbiology, 2015-11) Owusu-Kwarteng, J.; Tano-Debrah, K.; Akabanda, F.; Jespersen, L.Background Throughout Africa, food fermentations are still driven by indigenous microorganisms which influence the nutritional, organoleptic and safety of the final products. However, for improved safety, consistent quality and beneficial health effects, a trend has emerged which involves the isolation of indigenous strains from traditional fermented products to be used as functional starter cultures. These functional starter cultures possess inherent functional characteristics and can contribute to food quality and safety by offering one or more organoleptic, nutritional, technological or health advantage (probiotics). With the aim of selecting potential probiotic starter cultures, Lactobacillus fermentum strains isolated from fermented millet dough were investigated for technological properties and probiotic traits in-vitro. Results A total of 176 L. fermentum strains were assessed for technological properties including rate of acidification, exopolysaccharide production and amylase activity. Following this, 48 strains showing desirable technological properties were first screened for acid resistance. Sixteen acid resistant strains were assessed for additional probiotic properties including resistance to bile salts, bile salt hydrolysis, antimicrobial property, haemolysis and antibiotics resistance. L. fermentum strains clustered into 3 groups represented by 36 %, 47 % and 17 % as fast, medium and slow acidifiers respectively. About 8 %, 78 % and 14 % of the strains showed strong, weak and no exopolysaccharides production respectively. Amylase activity was generally weak or not detected. After exposure of 48 L. fermentum strains to pH 2.5 for 4 h, 16 strains were considered to be acid resistant. All 16 strains were resistant to bile salt. Four strains demonstrated bile salt hydrolysis. Antimicrobial activity was observed towards Listeria monocytogenes and Staphylococcus aureus but not E. coli and Salmonella enteritidis. Lactobacillus fermentum strains were generally susceptible to antibiotics except 6 strains which showed resistance towards streptomycin, gentamicin and kanamycin. Conclusion In vitro determination of technological and probiotic properties have shown strain specific difference among L. fermentum strains isolated from fermented millet dough. Sixteen (16) L. fermentum strains have been shown to possess desirable technological and probiotic characteristics in vitro. These strains are therefore good candidates for further studies to elucidate their full potential and possible application as novel probiotic starter cultures.Item The use of lactic acid bacteria starter culture in the production of Nunu, a spontaneously fermented milk product in Ghana(International Journal of Food Science, 2014-12) Akabanda, F.; Owusu-Kwarteng, J.; Tano-Debrah, K.; Parkouda, C.; Jespersen, L.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. © 2014 Fortune Akabanda et al.Item Yeast populations associated with Ghanaian cocoa fermentations analysed using denaturing gradient gel electrophoresis (DGGE)(Yeast, 2005-03) Nielsen, D.S.; Hønholt, S.; Tano-Debrah, K.; Jespersen, L.The yeast populations associated with the fermentation of Ghanaian cocoa were investigated using denaturing gradient gel electrophoresis (DGGE). Samples were collected at 12-24 h intervals from heap and tray fermentations, at three different fermentation sites and different periods during the season. Eukaryotic universal primers were used to amplify a fragment of the 26S rRNA gene. The DGGE profiles were relatively complex, underlining that the fermentation of cocoa is a complex microbial process. The identities of selected fragments in the denaturing gels were revealed by sequencing. Hanseniaspora guilliermondii, Candida krusei and Pichia membranifaciens were detected from most fermentations, indicating their possible important role in the fermentation of Ghanaian cocoa. Saccharomyces cerevisiae and Candida zemplinina were almost exclusively detected during tray fermentations. The developed DGGE protocol was compared with traditional culture-based isolations. The results were comparable but slightly different, as one yeast species (C. zemplinina) was only detected using DGGE. On the other hand, Trichosporon asahii yielded only faint bands in the denaturing gels, despite the fact that it was detected using culture-based methods. Analysis of pure cultures showed that the targeted region of the 26S rRNA gene was poorly amplified in T. asahii, whereas all other investigated isolates were amplified efficiently using the chosen PCR approach. Cluster analysis revealed that the DGGE profiles clustered according to fermentation method and fermentation site. Furthermore, clustering according to progress in the fermentation was observed. The DGGE technique therefore seems to offer a relatively fast and reliable method for studying yeast population dynamics during cocoa fermentations. The nucleotide sequences determined in this study have been assigned Genbank Accession Nos AY762330-AY762349. Copyright © 2005 John Wiley & Sons, Ltd.