The Occurrence, Growth And Control Of Pathogens In African Fermented Foods

Fermented foods have many advantageous attributes such as improved nutritional value and safety against bacterial pathogens. These foods are also important for weaning purposes and hence play a role in protecting infants against foodborne diseases. However, pathogens have been isolated from some fermented foods and challenge tests have shown the possibility of pathogens to survive and grow in some fermented foods. Post processing contamination is often cited as the major cause of food poisoning. Fermented foods with a pH value below 4 are usually safe as most pathogens are unable to survive under these conditions. However, some pathogens such as Escherichia coli O157:H7 are reported to develop acid tolerance. This is a particular problem for fermented sausages. However, there is very little information on the occurrence and growth of pathogens in African fermented foods. Most work on African fermented foods has focused on the isolation and identification of the desirable microorganisms involved in the fermentation process. Some authors have now started focusing on the possibility of some pathogens to survive and grow in some of the fermented foods. This review highlights some of the cases where pathogens have been detected in fermented foods, or have been shown to survive and grow in such foods. The most commonly encountered pathogens in African fermented foods include Bacillus cereus , E. coli, Salmonella sp., Staphylococcus aureus , Vibrio cholerae , Aeromonas , Klebsiella , Campylobacter and Shigella sp. The approaches that can be used to minimise the risk of foodborne diseases through consumption of fermented foods include improved hygiene, use of starter cultures, use of protective cultures and the use of a combination of factors that inhibit the growth of microorganisms (multiple hurdles). The use of concepts such as Hazard Analysis Critical Control (HACCP) system is still problematic at household level. However, this approach has been suggested for some African fermented foods such as kenkey (Ghana). This is thought to help in channelling resources to steps that provide effective protection

THE OCCURRENCE, GROWTH AND CONTROL OF PATHOGENS IN AFRICAN FERMENTED FOODS

Fermented foods have many advantageous attributes such as improved nutritional value and safety against bacterial pathogens. These foods are also important for weaning purposes and hence play a role in protecting infants against foodborne diseases. However, pathogens have been isolated from some fermented foods and challenge tests have shown the possibility of pathogens to survive and grow in some fermented foods. Post processing contamination is often cited as the major cause of food poisoning. Fermented foods with a pH value below 4 are usually safe as most pathogens are unable to survive under these conditions. However, some pathogens such as Escherichia coli O157:H7 are reported to develop acid tolerance. This is a particular problem for fermented sausages. However, there is very little information on the occurrence and growth of pathogens in African fermented foods. Most work on African fermented foods has focused on the isolation and identification of the desirable microorganisms involved in the fermentation process. Some authors have now started focusing on the possibility of some pathogens to survive and grow in some of the fermented foods. This review highlights some of the cases where pathogens have been detected in fermented foods, or have been shown to survive and grow in such foods. The most commonly encountered pathogens in African fermented foods include Bacillus cereus, E. coli, Salmonella sp., Staphylococcus aureus, Vibrio cholerae, Aeromonas, Klebsiella, Campylobacter and Shigella sp. The approaches that can be used to minimise the risk of foodborne diseases through consumption of fermented foods include improved hygiene, use of starter cultures, use of protective cultures and the use of a combination of factors that inhibit the growth of microorganisms (multiple hurdles). The use of concepts such as Hazard Analysis Critical Control (HACCP) system is still problematic at household level. However, this approach has been suggested for some African fermented foods such as kenkey (Ghana). This is thought to help in channelling resources to steps that provide effective protection. Key Words: fermented foods, pathogens, weaning foods, bacteriocins AJFAND Vol.4(1) 2004

Effect of agronomic practices and weather conditions on mycotoxins in maize : a case study of subsistence farming households in Zimbabwe

Maize is susceptible to many mycotoxigenic fungi and mycotoxins, being prone to Fusarium spp. infection and subsequent mycotoxin contamination. Fumonisin B-1 (FB1) is the predominant mycotoxin in Zimbabwean subsistence-grown maize and results of mycotoxin analyses indicated FB1 to be significantly higher compared to other mycotoxins. To fully elucidate maize agronomic practices influencing FB1 contamination of maize produced by Zimbabwean subsistence farming populations, an investigative field survey was conducted in the selected provinces of Mashonaland West and Manicaland. Agronomic data and associated climatic data were collected during the 2014/2015 agricultural season. A total of 158 maize samples were collected from households' harvest, three months and six months post-harvest. Analysis and quantification of mycotoxin contamination in the maize samples was performed using a validated multi-mycotoxin analysis method with a scope of 23 mycotoxins. Maize was mainly contaminated by FB1. There was low mycotoxin co-occurrence in Zimbabwean maize, which was typically of Fusarium toxins. FB1 occurred in 23, 47 and 47% of samples at harvest, three and six months post-harvest, respectively. The corresponding means of positive samples were 609, 597 and 289 pg/kg, respectively. Regarding fumonisins, the choice of seed and fertiliser application were significant in modulating FB1 contamination. There was no significant difference in mean FB1 contamination during post-harvest maize storage. Daily temperatures were key factors influencing FB1 incidence and levels. High temperatures were associated with high FB1 contamination particularly at the flowering stage of maize. Rainfall was positively correlated with FB1 contamination. Good agricultural practices attributed to low FB1 contamination in maize pre-harvest. Post-harvest practices such as preserving seed integrity by preventing pest infestation using grain protection chemicals are important in achieving lower mycotoxin contamination and in particular, FB1, in maize grain

EFFECT OF GERMINATION AND ROASTING ON THE PROXIMATE, MINERAL AND ANTI-NUTRITIONAL FACTORS IN FINGER MILLET (Eleucine coracana), COWPEAS (Vigna unguiculata) AND ORANGE MAIZE (Zea mays)

Finger millet (Eleucine coracana), cowpea (Vigna unguiculata), and bio-fortified vitamin A “orange” maize (Zea mays) are three nutrient dense crops currently being promoted in Zimbabwe. The effect on nutrient content of processing these specific crop varieties has not been investigated. Therefore, this study was designed to determine the effects of germination and roasting on the proximate, mineral, and antinutritional factors in finger millet, cowpeas and orange maize. Finger millet grains were germinated for 48hrs, cowpeas and orange maize for 24hrs, at room temperature (20-23oC). Both raw and processed samples were dried and milled into flour for the determination of proximate and mineral and anti-nutritional composition. Protein content of finger millet increased significantly after processing from 6.53±0.25 mg/100 g to 11.27±0.15 mg/100 g in germinated finger millet flour (P<0.05). Germination of finger millet resulted in significantly increased minerals (mg/100 g); calcium from 345.53±0.55 to 352.63±0.21, zinc from 3.59±0.15 to 8.71±0.01, sodium from 49.89±0.16 to 57.78±1.20 and iron content from 3.75±0.05 to 4.52±0.01 whilst magnesium and potassium decreased significantly from 198.09±0.07 to 69.08±0.06 and 487.08±0.03 to 144.78±0.27 respectively. Processing of cowpeas resulted in slight but significant increase in protein content (20.47±0.21 to 28.50±0.10), increased calcium (138.18±0.12 to 148.18±0.12 mg/100 g), magnesium (14.23±2.00 to 19.18±0.31 mg/100 g), potassium (232±4.00 to 443.41±0.02 mg/100 g) and iron (4.85±0.03 to 4.86±0.04 mg/100 g). Conversely zinc and sodium decreased from 4.5±0.30 to 2.9±0.10 mg/100 g and 31.85±0.03 to 11.64±0.02 mg/100 g, respectively. Notably for orange maize, protein content did not change from 10.06±0.04 to 10.04±0.04 g/100 g before and after processing. Calcium increased from 47.02±2.82 to 57.99±8.85 (mg/100 g), magnesium from 90.91±0.11 to 108.30±0.53 (mg/100 g), potassium from 2.13±0.04 to 4.33±0.25 (mg/100 g), sodium from 0.50±0.02 to 0.70±0.02 (mg/100 g) and iron from 0.50±0.02 to 1.25±0.05 (mg/100 g). Zinc decreased from 6.2±0.2 to 3.53±0.55 (mg/100 g). Tannins, oxalates and phytates decreased significantly after processing of all three crops. Results showed that germination and roasting increased the nutritional profile and decreased anti-nutrient content in finger millet, cowpeas and orange maize. Therefore, it is important to consider germinating and roasting these grains during processing to increase the nutritional potential of the end food product. Further studies are required to investigate the decrease in some nutrients after germination and roasting and possibly establish optimum processing parameters for improved nutrient profile of these food crops

EFFECT OF GERMINATION AND ROASTING ON THE PROXIMATE, MINERAL AND ANTI-NUTRITIONAL FACTORS IN FINGER MILLET (Eleucine coracana), COWPEAS (Vigna unguiculata) AND ORANGE MAIZE (Zea mays)

Finger millet (Eleucine coracana), cowpea (Vigna unguiculata), and bio-fortified vitamin A “orange” maize (Zea mays) are three nutrient dense crops currently being promoted in Zimbabwe. The effect on nutrient content of processing these specific crop varieties has not been investigated. Therefore, this study was designed to determine the effects of germination and roasting on the proximate, mineral, and antinutritional factors in finger millet, cowpeas and orange maize. Finger millet grains were germinated for 48hrs, cowpeas and orange maize for 24hrs, at room temperature (20-23oC). Both raw and processed samples were dried and milled into flour for the determination of proximate and mineral and anti-nutritional composition. Protein content of finger millet increased significantly after processing from 6.53±0.25 mg/100 g to 11.27±0.15 mg/100 g in germinated finger millet flour (P<0.05). Germination of finger millet resulted in significantly increased minerals (mg/100 g); calcium from 345.53±0.55 to 352.63±0.21, zinc from 3.59±0.15 to 8.71±0.01, sodium from 49.89±0.16 to 57.78±1.20 and iron content from 3.75±0.05 to 4.52±0.01 whilst magnesium and potassium decreased significantly from 198.09±0.07 to 69.08±0.06 and 487.08±0.03 to 144.78±0.27 respectively. Processing of cowpeas resulted in slight but significant increase in protein content (20.47±0.21 to 28.50±0.10), increased calcium (138.18±0.12 to 148.18±0.12 mg/100 g), magnesium (14.23±2.00 to 19.18±0.31 mg/100 g), potassium (232±4.00 to 443.41±0.02 mg/100 g) and iron (4.85±0.03 to 4.86±0.04 mg/100 g). Conversely zinc and sodium decreased from 4.5±0.30 to 2.9±0.10 mg/100 g and 31.85±0.03 to 11.64±0.02 mg/100 g, respectively. Notably for orange maize, protein content did not change from 10.06±0.04 to 10.04±0.04 g/100 g before and after processing. Calcium increased from 47.02±2.82 to 57.99±8.85 (mg/100 g), magnesium from 90.91±0.11 to 108.30±0.53 (mg/100 g), potassium from 2.13±0.04 to 4.33±0.25 (mg/100 g), sodium from 0.50±0.02 to 0.70±0.02 (mg/100 g) and iron from 0.50±0.02 to 1.25±0.05 (mg/100 g). Zinc decreased from 6.2±0.2 to 3.53±0.55 (mg/100 g). Tannins, oxalates and phytates decreased significantly after processing of all three crops. Results showed that germination and roasting increased the nutritional profile and decreased anti-nutrient content in finger millet, cowpeas and orange maize. Therefore, it is important to consider germinating and roasting these grains during processing to increase the nutritional potential of the end food product. Further studies are required to investigate the decrease in some nutrients after germination and roasting and possibly establish optimum processing parameters for improved nutrient profile of these food crops