Ygc agar

For a general microbiological analysis, 25 nono samples were bought from Fulani processors and local markets in Kano, Katsina, Jigawa, and Bauchi states in northern Nigeria. The samples were transported under cooled conditions to the laboratory, and the pH of the nono samples was measured using a pH electrode (Mettler Tuledo Inlab Expert Pt 1000, Gießen, Germany). Samples were then diluted in a serial tenfold-dilution series using quarter-strength Ringers solution (Merck, Darmstadt, Germany). After this, 100 µL aliquots of appropriate dilutions were plated out in duplicate onto different selective culture media in order to determine the total amount of aerobic, mesophilic bacteria on plate count agar (VWR Chemicals, Leuven, Belgium); LAB on de Man, Rogosa, and Sharpe agar (MRS agar, Merck, Darmstadt, Germany); and Gram-negative bacteria on violet red bile dextrose agar (VRBD agar, Merck, Darmstadt, Germany) incubated at 30 °C and streptococci on M17 medium incubated at 45 °C. In addition to selective enumeration of bacteria, the numbers of yeasts in the samples were determined using yeast extract–glucose–chloramphenicol agar (YGC agar, Merck, Darmstadt, Germany).

The dough was created with contaminated flour (25 g), water (17 ml), and Saccharomyces cerevisiae (commonly known as baker's yeast). To investigate the effects of fermentation on AFB₁ contamination, the samples were prepared with two levels of baker's yeast (1%, 2% w/w). The yeast survivability was evaluated by microbial examination as CFU per gram of dry matter. The yeast was mixed with water and the yeast cell suspension was counted by the plate counting method on the yeast extract‐glucose‐chloramphenicol (YGC) agar (Merck, Germany). The average number of viable yeast cells was 12 × 10¹⁰ (CFU/g) in triplicate after 5 days of incubation at 25°C (Rad & Kasaie, 2017). The dough samples (5 and 10 µg/kg) were physically mixed until they shaped an elastic and nonsticky structure. The prepared samples were fermented in the oven at 35°C for 30, 60, and 90 min. After extraction and purification, the remaining levels of AFB₁ were detected. According to the results, the optimum yeast concentration and fermentation time were determined.