Detection of spoilage-causing yeasts and bacteria in tchapalo, the Ivorian traditional sorghum beer.

In this study, we aimed to analyse the spoilage potential of the isolated yeast, LAB and AAB species. Thus, 11 strains were inoculated at 0·3% (v/v) into a sterile filtered tchapalo and stored for 3 days at ambient temperature (27-30°C). All the tested strains grew well or remained stable except for Limosilactobacillus fermentum and Pediococcus acidilactici, which decreased throughout the storage time. A significant decrease of total soluble solids was observed only for Saccharomyces cerevisiae (from 7·8 to 5·8 °Brix) and Meyerozyma guilliermondii (from 7·8 to 5·5 °Brix). The tchapalo samples inoculated with the LAB strains Weissella paramesenteroides, P. acidilactici, L. fermentum and the yeast strain Candida tropicalis were judged similar to the control by the panellists. However, the strains of Lacticaseibacillus paracasei and Latilactobacillus curvatus (LAB), S. cerevisiae, M. guilliermondii and Kluyveromyces marxianus (yeasts) and Acetobacter pasteurianus and A. cerevisiae (AAB) induced the spoilage of the tchapalo appearance, smell and/or taste. In the spoiled tchapalo quantitative and qualitative modification of some volatile compounds (VOCs), such as lilac aldehyde, ethyl acetate, ethyl hexanoate, ethyl octanoate and phenethyl acetate, were observed. These results provide information about the microorganisms that need to be removed to extend the shelf life of tchapalo.

Development and implementation of an analytical procedure for the quantification of natural and synthetic steroid hormones in whole surface waters.

Natural and synthetic steroid hormones are chronically released into aquatic spheres. Whereas knowledge on their combined mode of action and the cocktail effect are needed, only few multi-class methods address the challenge of their trace quantification in surface waters. The current study describes a sensitive multi-residue analytical strategy aiming to quantify 23 steroid hormones belonging to androgens, estrogens, glucocorticoids and progestogens in whole surface waters. The procedure relies on a two-step solid-phase extraction followed by an ultra-performance liquid chromatography separation coupled to tandem mass spectrometry detection (UPLC-MS/MS). Isotope dilution was implemented when possible in order to ensure the reliability of the measurement. The procedure was optimized toward the reliable quantification of the 23 target compounds at the predicted no-effect concentrations when existing or below the ng L-1 level. Satisfactory absolute global recoveries ≥ 77% were obtained for almost all compounds (21 out of 23) in intermediate precision conditions. Measurement errors were comprised between -27% and +17% for the great majority of compounds (21 out of 23) with standard deviations < 20% in intermediate precision conditions. Despite signal suppression was observed in water samples, satisfactory limits of quantification were achieved, ranging from 0.035 ng L-1 for 17alpha-ethinylestradiol to 1 ng L-1 for 6beta-hydroxycortisol and 6beta-hydroxydexamethasone. Abiotic stability was demonstrated for the great majority of target compounds (22 out of 23) in reference water samples stored at 4 ± 3 °C during 48 h, driving our sampling strategy. To demonstrate its fitness for purpose, the procedure was implemented in a preliminary monitoring survey of Belgian surface waters. As a result, 6 out of 23 target compounds were detected or quantified, showing a contamination by some estrogens and glucocorticoids at levels ranging from 0.1 to 0.9 ng L-1.