James Owusu-Kwarteng

Biodiversity and probiotic potential of yeasts isolated from Fura, a West African spontaneously fermented cereal

Fura is a spontaneously fermented pearl millet product consumed in West Africa. The yeast species involved in the fermentation were identified by pheno- and genotypic methods to be Candida krusei, Kluyveromyces marxianus, Candida tropicalis, Candida rugosa, Candida fabianii, Candida norvegensis and Trichosporon asahii. C. krusei and K. marxianus were found to be the dominant species. Survival in pH 2.5 or in the presence of bile salts (0.3% (w/v) oxgall) and growth at 37°C were independently determined as indicators of the survival potential of the isolates during passage through the human gastrointestinal tract. Selected yeast species isolates were assessed for their probiotic potential. All of the examined yeast isolates survived and grew at human gastrointestinal conditions in pH 2.5, 0.3% (w/v) oxgall at 37°C. The effect on the transepithelial electrical resistance (TEER) across polarized monolayers of intestinal epithelial cells of human (Caco-2) and porcine (IPEC-J2) origin, were determined. The Caco-2 cells and IPEC-J2 cells displayed clearly different relative TEER results. The strains of C. krusei, K. marxianus, C. rugosa and T. asahii were able to increase the relative TEER of Caco-2 monolayers after 48h. In comparison, the relative TEER of IPEC-J2 monolayers decreased when exposed to the same yeasts, even though T. asahii did not differ significantly from Saccharomyces cerevisiae var. boulardii which is used as a human probiotic. C. tropicalis resulted in the largest relative TEER decrease for both the human and the porcine cell model assays. Hyphal growth was observed for C. albicans and C. tropicalis after 48h of incubation with polarized Caco-2 monolayers, whereas this was not the case for the remaining yeast species. In the present study new yeast strains with potential probiotic properties have been isolated to be used potentially as starter cultures for fura production.

Prevalence, virulence factor genes and antibiotic resistance of Bacillus cereus sensu lato isolated from dairy farms and traditional dairy products

BackgroundB. cereus are of particular interest in food safety and public health because of their capacity to cause food spoilage and disease through the production of various toxins. The aim of this study was to determine the prevalence, virulence factor genes and antibiotic resistance profile of B. cereus sensu lato isolated from cattle grazing soils and dairy products in Ghana. A total of 114 samples made up of 25 soil collected from cattle grazing farm land, 30 raw milk, 28 nunu (yoghurt-like product) and 31 woagashie (West African soft cheese). Ninety-six B. cereus sensu lato isolates from 54 positive samples were screened by PCR for the presence of 8 enterotoxigenic genes (hblA, hblC, hblD, nheA, nheB, nheC, cytK and entFM), and one emetic gene (ces). Phenotypic resistance to 15 antibiotics were also determined for 96 B. cereus sensu lato isolates.ResultsAbout 72% (18 of 25 soil), 47% (14 of 30 raw milk), 35% (10 of 28 nunu) and 39% (12 of 31 woagashi) were positive for B. cereus sensu lato with mean counts (log10 cfu/g) of 4.2 ± 1.8, 3.3 ± 2.0, 1.8 ± 1.4 and 2.6 ± 1.8 respectively. The distribution of enterotoxigenic genes revealed that 13% (12/96 isolates) harboured all three gene encoding for haemolytic enterotoxin HBL complex genes (hblA, hblC and hblD), 25% (24/96 isolates) possessed no HBL gene, whereas 63% (60/96 isolates) possessed at least one of the three HBL genes. All three genes encoding for non-haemolytic enterotoxin (nheA, nheB and nheC) were detected in 60% (57/96) isolates, 14% (13/96) harboured only one gene, 19% (18/96) whereas 8% possessed none of the NHE genes. The detection rates of cytk, entFM, and ces genes were 75, 67 and 9% respectively. Bacillus cereus s. l. isolates were generally resistant to β-lactam antibiotics such as ampicillin (98%), oxacillin (92%), penicillin (100%), amoxicillin (100%), and cefepime (100%) but susceptible to other antibiotics tested.ConclusionsBacillus cereus s. l. is prevalent in soil, raw milk and dairy products in Ghana. However, loads are at levels considered to be safe for consumption. Various enterotoxin genes associated with virulence of B. cereus are widespread among the isolates.

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.

Food safety knowledge, attitudes and practices of institutional food-handlers in Ghana

BackgroundIn large scale cooking, food is handled by many individuals, thereby increasing the chances of food contamination due to improper handling. Deliberate or accidental contamination of food during large scale production might endanger the health of consumers, and have very expensive repercussions on a country. The purpose of this study was to evaluate the food safety knowledge, attitudes, and practices among institutional food- handlers in Ghana.MethodsThe study was conducted using a descriptive, cross-sectional survey of 29 institutions by conducting face to face interview and administration of questionnaire to two hundred and thirty-five (235) institutional food-handlers. The questionnaire was peer-reviewed and pilot tested in three institutions in the Upper East Region of Ghana, before the final version was distributed to food-handlers. The questionnaire was structured into five distinctive parts to collect information on (i) demographic characteristics, (ii) employees’ work satisfaction, (iii) knowledge on food safety, (iv) attitudes towards food safety and (v) food hygiene practices.ResultsMajority of the food-handlers were between 41–50 years (39.1%). Female respondents were (76.6%). In our study, the food-handlers were knowledgeable about hygienic practices, cleaning and sanitation procedures. Almost all of the food-handlers were aware of the critical role of general sanitary practices in the work place, such as hand washing (98.7% correct answers), using gloves (77.9%), proper cleaning of the instruments/utensils (86.4%) and detergent use (72.8%). On disease transmission, the results indicates that 76.2% of the food- handlers did not know that Salmonella is a food borne pathogens and 70.6% did not know that hepatitis A is a food borne pathogen. However, 81.7% handlers agreed that typhoid fever is transmitted by food and 87.7% agreed that bloody diarrhea is transmitted by food. Logistic regression analysis testing four models showed statistically significant differences (p < 0.05), for models in which the explanatory variable was the level of education.ConclusionsIn generally, the institutional food-handlers have satisfactory knowledge in food safety but this does not translate into strict hygienic practices during processing and handling food products.

Nunu, A West African Fermented Yogurt-Like Milk Product

In the context of the current trend toward natural products, there seems to be an increasing preference for consuming yogurts and fermented yogurt-like products, because these products are associated with several proven and perceived health benefits. Nunu is one of such fermented yogurt-like milk product consumed in West Africa. Nunu can be produced from either pasteurized or unpasteurized cows milk by spontaneous fermentation. Here we present the available scientific information on the production processes, microbiological and nutritional or health aspects of nunu. Undoubtedly, nunu has received very little scientific attention. However, there is enough demonstrated evidence that nunu can contribute significantly to improving the nutritional status of consumers. The fermenting microbiota may also provide several beneficial health effects for consumers. The contribution of West African yogurt-like milk products to a healthy lifestyle can be realized by orientating research to produce nutrient-rich and healthy dairy products, and supporting the science that will fill the existing knowledge gaps.

Effects of Blanching and Natural Convection Solar Drying on Quality Characteristics of Red Pepper (Capsicum annuum L.)

The objective of this work was to determine the effects of blanching and two drying methods, open-sun drying and natural convection solar drying, on the quality characteristics of red pepper. A 2 × 3 factorial design with experimental factors as 2 drying methods (open-sun drying and use of solar dryer) and 3 levels of pepper blanching (unblanched, blanched in plain water, and blanched in 2% NaCl) was conducted. Dried pepper samples were analysed for chemical composition, microbial load, and consumer sensory acceptability. Blanching of pepper in 2% NaCl solution followed by drying in a natural convection solar dryer reduced drying time by 15 hours. Similarly, a combination of blanching and drying in the solar dryer improved microbial quality of dried pepper. However, blanching and drying processes resulted in reduction in nutrients such as vitamin C and minerals content of pepper. Blanching followed by drying in natural convection solar dryer had the highest consumer acceptability scores for colour and overall acceptability, while texture and aroma were not significantly (p > 0.05) affected by the different treatments. Therefore, natural convection solar dryer can be used to dry pepper with acceptable microbial and sensory qualities, as an alternative to open-sun drying.