Aflatoxins are toxic carcinogenic secondary metabolites produced predominantly by two fungal species: Aspergillus flavus and Aspergillus parasiticus. These fungal species are contaminants of foodstuff as well as feeds and are responsible for aflatoxin contamination of these agro products. The toxicity and potency of aflatoxins make them the primary health hazard as well as responsible for losses associated with contaminations of processed foods and feeds. Determination of aflatoxins concentration in food stuff and feeds is thus very important. However, due to their low concentration in foods and feedstuff, analytical methods for detection and quantification of aflatoxins have to be specific, sensitive, and simple to carry out. Several methods including thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), mass spectroscopy, enzyme-linked immune-sorbent assay (ELISA), and electrochemical immunosensor, among others, have been described for detecting and quantifying aflatoxins in foods. Each of these methods has advantages and limitations in aflatoxins analysis. This review critically examines each of the methods used for detection of aflatoxins in foodstuff, highlighting the advantages and limitations of each method. Finally, a way forward for overcoming such obstacles is suggested.
Fermentation of food products can be used for the delivery of probiotic bacteria and means of food detoxification, provided that probiotics are able to grow, and toxins are reduced in raw materials with minimal effects on consumer acceptability. This study evaluated probiotic enrichment and detoxification of kwete, a commonly consumed traditional fermented cereal beverage in Uganda, by the use of starter culture with the probiotic Lactobacillus rhamnosus yoba 2012 and Streptococcus thermophilus C106. Probiotic kwete was produced by fermenting a suspension of ground maize grain at 30 °C for a period of 24 h, leading to a decrease of the pH value to ≤ 4.0 and increase in titratable acidity of at least 0.2% (w/v). Probiotic kwete was acceptable to the consumers with a score of ≥6 on a 9-point hedonic scale. The products were stable over a month’s study period with a mean pH of 3.9, titratable acidity of 0.6% (w/v), and Lactobacillus rhamnosus counts >108 cfu g−1. HPLC analysis of aflatoxins of the water-soluble fraction of kwete indicated that fermentation led to an over 1000-fold reduction of aflatoxins B1, B2, G1, and G2 spiked in the raw ingredients. In vitro fluorescence spectroscopy confirmed binding of aflatoxin B1 to Lactobacillus rhamnosus with an efficiency of 83.5%. This study shows that fermentation is a means to enrich with probiotics and reduce widely occurring aflatoxin contamination of maize products that are consumed as staple foods in sub-Saharan Africa.
BackgroundDue to increasing pressure on natural resources, subsistence agriculture communities in Uganda and Sub-Saharan Africa are experiencing increasingly restricted access to diminishing natural resources that are a critical requirement of their livelihoods. Previously, common-pool resources like forests and grasslands have been either gazetted for conservation or leased for agriculture, the latter in particular for large-scale sugarcane production. Satisfying the increasing consumer demand for grassland or forestry products like wild mushrooms as food or medicine, requires innovative ethno-biological and industry development strategies to improve production capacity, while easing the pressure on diminishing natural resources and averting ecosystems degradation.MethodsThis case study addresses traditional knowledge systems for artisanal mycoculture to identify cultivation practices that enhance sustainable utilization of natural resources. Multi-scalar stakeholder engagement across government and community sectors identified artisanal mushroom producers across five districts in Uganda. Focus groups and semi-structured interviews characterized artisanal production methods and identified locally used substrates for cultivation of different mushroom species.ResultsArtisanal practices were characterized for the cultivation of six wild saprophytic mushroom species including Volvariella speciosa (akasukusuku), two Termitomyces sp. (obunegyere and another locally unnamed species), Agaricus sp. (ensyabire) and Agrocybe sp. (emponzira), and one exotic Pleurotus sp. (oyster) that are used as food or medicine. The substrates used for each species differed according to the mushroom’s mode of decomposition, those being the following: tertiary decomposers such as those growing under rotting tree stumps or logs from forestry activity like the Agrocybe sp. known as emponzira which grows in forests, thickets, or near homesteads where big logs of hardwood have been left to rot. Also pieces of firewood are chipped off whenever need arises thus providing fuel; secondary decomposers growing on naturally composted grass associated with termites like the Termitomyces sp. known as obunegyere growing in protected sites in gardens, composted cattle manure for Agaricus sp. known as ensyabire in the kraal area where cattle manure is plenty, composted maize cobs for a locally unnamed Agaricus sp. on heaped cobs placed near homesteads; and primary decomposers growing on waste sorghum from brewing the traditional alcoholic drink, muramba for Pleurotus sp. (oyster), and banana and spear grass residue from banana juice processing like the Volvariella speciosa known as akasukusuku because it is associated with the banana plantation locally known in the Luganda language as olusuku and is usually heaped under ficus trees. Management practices also varied based on mode of decomposition and other ecological requirements such as the following: zero tillage and minimal disturbance in areas where obunegyere grow, heaping banana and spear grass residu...
The study characterized heterogeneous biocatalyst synthesized from sucrose, saw dust, and chicken egg shells using Fourier Transform Infrared (FTIR) spectroscopy coupled with Attenuated Total Reflectance (ATR) technique. Acidic sulphonate (–SO3H) groups were more visible in the spectrum generated for carbonized and sulphonated sucrose than in carbonized and sulphonated saw dust. This was highlighted further by the significantly higher conversion percentage achieved for sulphonated sucrose (62.5%) than sulphonated saw dust (46.6%) during esterification of expired sunflower oil (p=0.05). The spectra for calcinated egg shells also showed that the most active form of calcium oxide was produced at calcination temperature of 1000°C. This was confirmed in the single-step transesterification reaction in which calcium oxide generated at 1000°C yielded the highest biodiesel (87.8%) from expired sunflower oil. The study further demonstrated the versatility of the FTIR technique in qualitative analysis of biodiesel and regular diesel by confirming the presence of specific characteristic peaks of diagnostic importance. These findings therefore highlight the potential of FTIR-ATR as an inexpensive, fast, and accurate diagnostic means for easy identification and characterization of different materials and products.
An electroless plated silver/cysteine sensor platform [Glass|silver|cysteine|aflatoxin B 1 |horseradish peroxidase] for the Electrochemical detection of aflatoxin B 1 was developed and characterized. This involved four major steps: (1) an electroless deposition of silver (plating) onto a glass slide, (2) immobilization of cysteine; (3) conjugation of aflatoxin B 1 to cysteine groups; and (4) blocking of free cysteine groups with horseradish peroxidase (HRP). The binding of cysteine to the silver was demonstrated by the disappearance of thiol (S-H) groups at 2500 cm −1 using Fourier transmittance infrared spectra (FT-IR), while the subsequent steps in the assembly of sensor platform were monitored using both FT-IR and cyclic voltammetry, respectively. The sensor platform exhibited a broadened nonsymmetrical redox couple as indicated by cyclic voltammetry. The platform was further characterized for sensitivity and limit of detection. The indirect competitive immunoassay format, whereby free and immobilized aflatoxin B 1 on the sensor competed for the binding site of free anti-aflatoxin B 1 antibody, was used at various concentrations of aflatoxin B 1 . The sensor generated differential staircase voltammogram that was inversely proportional to the concentration of aflatoxin B 1 and aflatoxin B 1 in the range of 0.06-1.1 ng/mL with a detection limit of 0.08 ng/mL could be detected.
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