Traditionally Processed Beverages in Africa: A Review of the Mycotoxin Occurrence Patterns and Exposure Assessment

African traditional beverages are widely consumed food‐grade liquids processed from single or mixed grains (mostly cereals) by simple food processing techniques, of which fermentation tops the list. These beverages are very diverse in composition and nutritional value and are specific to different cultures and countries. The grains from which home‐processed traditional beverages are made across Africa are often heavily contaminated with multiple mycotoxins due to poor agricultural, handling, and storage practices that characterize the region. In the literature, there are many reports on the spectrum and quantities of mycotoxins in crops utilized in traditional beverage processing, however, few studies have analyzed mycotoxins in the beverages themselves. The available reports on mycotoxins in African traditional beverages are mainly centered on the finished products with little information on the process chain (raw material to final product), fate of the different mycotoxins during processing, and exposure estimates for consumers. Regulations targeting these local beverages are not in place despite the heavy occurrence of mycotoxins in their raw materials and the high consumption levels of the products in many homes. This paper therefore comprehensively discusses for the 1st time the available data on the wide variety of African traditional beverages, the mycotoxins that contaminate the beverages and their raw materials, exposure estimates, and possible consequent effects. Mycotoxin control options and future directions for mycotoxin research in beverage production are also highlighted.     

Numerical study of hydrogen‐enriched methane–air combustion under ultra‐lean conditions

The demand for gas turbines that accept a variety of fuels has continuously increased over the last decade. Understanding the effects of varying fuel compositions on combustion characteristics and emissions is critical to designing fuel‐flexible combustors. In this study, the combustion characteristics and emissions of methane and hydrogen‐enriched methane were both experimentally and numerically investigated under ultra‐lean conditions (Ø ≤ 0.5). This study was performed using global mechanisms with a one‐step mechanism by Westbrook and Dryer and a two‐step mechanism with an irreversible and reversible CO/CO₂ step (2sCM1 and 2sCM2). Results show that the 2sCM2 mechanism under‐predicted the temperature, major species, and NO_x by more than 100% under ultra‐lean conditions; thus, we proposed a modified‐2sCM2 mechanism to better simulate the combustion characteristics. The mechanisms of Westbrook, 2sCM1, and modified 2sCM2 predicted the temperature and the CO₂ emission with an average deviation of about 5% from the experimental values. Westbrook and 2sCM1, however, over‐predicted the NO_x emission by approximately 81% and 152%, respectively, as compared with an average under‐prediction of 11% by the modified‐2sCM2 mechanism. The numerical results using the proposed modified‐2sCM2 mechanism shows that the presence of hydrogen in the fuel mixture inhibits the oxidation of methane that led to the formation of unburned hydrocarbons in the flame. We also showed that for any given fuel compositions of H₂/CH₄, there is an optimum equivalence ratio at which the pollutant emissions (CO and NO_x) from the combustor are minimal. Zero CO and 5 ppm NO_x emissions were observed at the optimal equivalence ratio of 0.45 for a fuel mixture containing 30% H₂. The present study provides a basis for ultra‐lean combustion toward achieving zero emissions from a fuel‐flexible combustor. Copyright © 2016 John Wiley & Sons, Ltd.     

Aflatoxin and fumonisin contamination of yam flour from markets in Nigeria

The natural occurrence of aflatoxins (AFs) and fumonisins (FBs) in yam flour samples (n = 100) obtained in south-western Nigeria was evaluated. AFs were determined by HPLC with fluorescence detection and FBs by HPLC coupled with mass spectrometry. Aflatoxin B₁ (AFB₁) and aflatoxin G₁ (AFG₁) were found in 57% and 21% of flours from white yam with concentrations ranging from <0.02 (limit of detection, LOD) to 3.2 μg kg⁻¹ (mean = 0.4 μg kg⁻¹) and from <0.05 to 3.5 μg kg⁻¹, respectively. AFB₁ was the only aflatoxin detected in samples from water yam, contaminating 32% of the samples with values ranging from <LOD to 0.6 μg kg⁻¹ (mean = 0.1 μg kg⁻¹). Fumonisin B₁ was found in 32% of the white yam samples (<0.5 (LOD) to 91 μg kg⁻¹; mean = 5 μg kg⁻¹) and in 5% of water yam samples (<LOD to 2 μg kg⁻¹). AFs and FBs were significantly higher (P < 0.05) in white yam flours compared to water yam flours. Preparation of amala from naturally-contaminated yam flour resulted in reduction of AFB₁ and AFG₁ by 44% and 51% respectively. From this study, only 7% of the samples contained AFs above the European standard limits for cereals intended for direct human consumption, while all the FBs-positive samples were well below the limits. The occurrence of ochratoxin A, zearalenone and deoxynivalenol was also evaluated in 20 samples; these mycotoxins were never detected.     

Isolation and selection of technologically important lactic acid bacteria and yeast from fermented potato

This study focused on the isolation, identification and selection of lactic acid bacteria (LAB) and yeasts with important technological properties from fermented potato. A total of three LAB and two yeasts (Weissella sp. strain IMAU50209, Pediococcus pentosaceus strain W2SR04, Pediococcus sp. NBRC 107186 strain, Pichia sp. strain AQGWD7 and Saccharomyces cerevisiae strain YJM1592) were isolated and identified by molecular methods. Weissella sp. strain IMAU50209 showed good acidification and proteolytic ability. More so, it generated more volatile compounds and recorded the highest exopolysaccharide content (824.44 ± 4.19 mg L⁻¹). Saccharomyces cerevisiae strain YJM1592 recorded high gas retention value (V_R) 1740.00 ± 86.27 mL and produced beneficial volatile compounds, as compared to Pichia sp. strain AQGWD7. Therefore, Weissella sp. strain IMAU50209 and Saccharomyces cerevisiae strain YJM1592 could enhance gluten-free potato bread quality.     

Non-isothermal drying kinetics of human feces

Abstract

The non-isothermal drying behavior and kinetics of human feces (HF) were investigated by means of thermogravimetric analysis to provide data for designing a drying unit operation. The effect of heating rate and blending with woody biomass were also evaluated on drying pattern and kinetics. At low heating rate (1?K/min), there is effective transport of moisture, but a higher heating rate would be necessary at low moisture levels to reduce drying time. Blending with wood biomass improves drying characteristics of HF. The results presented in this study are relevant for designing non-sewered sanitary systems with in-situ thermal treatment.     

Performance analysis of a membrane‐based reformer‐combustor reactor for hydrogen generation

Hydrogen is mostly produced in conventional steam methane reforming plants. In this work, we proposed a membrane‐based reformer‐combustor reactor (MRCR) for hydrogen generation in order to improve heat recovery and overall thermal efficiency. The proposed configuration will also reduce the complexity in existing steam methane reforming (SMR) plants. The proposed MRCR comprises combustion zone, hydrogen permeate zone, and SMR zone. A computational fluid dynamics model was developed using ANSYS‐Fluent software to simulate and analyze the performance of the proposed MRCR. Results show that high hydrogen yields were observed at high reformer pressures (RPs) and low gas hourly space velocities (GHSVs). Furthermore, by increasing the steam to methane ratio and addition of excess air in the combustion side, the hydrogen yield from the MRCR decreases. This is attributed to the reduction in the effective temperature of the hydrogen membrane. High RP, low GHSV, and low steam to methane ratio that increased the hydrogen yield also decreased carbon monoxide (CO) emissions. For an increased RP from 1 to 10 bar, the CO emission decreased by about 99%. The reduction in CO emission at high RP would be attributed to the effect of water gas shift reaction in the MRCR. Results of the extensive parametric study presented in this work can be used to determine the operating conditions based on tradeoffs between hydrogen yield (mole H₂/mole CH₄), hydrogen production rate (kg of H₂/h), allowable CO emissions, and exhaust gas temperature for other applications such as gas turbine.     

Co-occurrence of aflatoxins,ochratoxin A and citrinin in “egusi” melon (Colocynthis citrullus L.) seeds consumed in Ireland and the United Kingdom

The natural co-occurrence of aflatoxins (AFs), ochratoxin A (OTA) and citrinin (CIT) in melon seed samples obtained from retailers and households in Ireland and the United Kingdom (UK) was evaluated. AFs and OTA were determined by HPLC with fluorescence detection while CIT was analysed by HPLC-MS/MS. AFB₁ was detected in all (100%) samples (mean = 9.7 μg kg^?1; range = 0.2–66.5 μg kg^?1). Mean total AFs was 12.0 μg kg^?1 (range = 0.3–82 μg kg^?1). Commercially retailed samples showed a significantly higher AFB₁ contamination (p < 0.05) than the household samples. OTA occurred in 3 (13.6%) samples, while 4 (18.2%) were contaminated with CIT at very low levels. In this study, 68% of the melon seed samples were contaminated above the 2 μg kg^?1 EU limit for AFB₁ in oilseeds. These results highlight the need for the development of strategies to reduce AF contamination in “egusi” for human consumption.     

Thermo-economic comparative analysis of solar-assisted and carbon capture integrated conventional cogeneration plant of power and process steam

A thermo-economic comparative analysis of steam production using a solar-assisted cogeneration (SACG) and a conventional cogeneration plant (CCG) with and without carbon capture systems has been conducted. The plants considered to produce electricity and process steam of 500 ton/h. Several parametric studies were carried out on the effect of natural gas price, steam quality, gas turbine capacity and solar multiples (SMs) on the Levelized cost of steam (LCS). Results show that in a CCG plant that comprises a 20 MWe gas turbine, the LCS is $8.11/ton of steam and $3.61/ton of steam from a plant with 100 MWe gas turbine capacity for a natural gas price of $3/GJ. The cost analysis of SACG plant with SM of 0.1 shows that 28% of the total annualized costs are solar system related while it contributed only about 9.17% of the annual steam generation. An increase in SM from 0.1 to 0.9 increases the CO₂ avoidance from 61 to 262 ktons/annum for the SACG plant with 20 MWe gas turbine. CCG plants with CO₂ capture technologies were found to have lower LCS in comparison with that of SACG plant. The impact of carbon credit implementation on the LCS has been also investigated and reported in this article.