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This study aimed to assess the microbiological quality of natural mineral waters commercialized in 20 L returnable packs in Brazil by investigating the presence of bacteria and viruses in packs with different manufacturing times (Tm). With this purpose, 99 water samples from 33 lots (n  = 3/batch) of 15 brands, obtained from packs with three intervals of Tm, were analyzed. Total coliforms (16.2%), Pseudomonas aeruginosa (9.9%), sulphite-reducing Clostridium (5.0%) and Escherichia coli (2.0%) were detected but enterococci and norovirus GII not. Regarding brands, 11 (73.3%) presented unsatisfactory results for at least one of the lots analyzed. Pseudomonas aeruginosa analysis revealed six sequence types and strains were susceptible to all antibiotics tested and were able to produce biofilms. Human adenovirus (4) and norovirus GI (9) were also identified in nine samples randomly selected. Natural mineral waters commercialized in 20 L packs with Tm ≥ 2 years presented more microbiological contamination (P  ≤ 0.012) than ones with a Tm of 0–1 year or a Tm of 1–2 years. These results suggest that the validity period of reusable 20 L packs should be reduced or that they can no longer be reused. [ABSTRACT FROM AUTHOR]

Highlights • The present work involves a study to develop a metabolite-incurred reference material. • Water content and mass fraction of nitrofuran metabolites in chicken were evaluated. • An irradiation step was optimized to reduce the initial microbiological contamination. • The method can be applied to produce a homogeneous and stable reference material. • The uncertainty contributions reached fit for purpose levels. Abstract Certified reference materials (CRM) provide measurements of quality and metrological traceability relative to the International System of Units (SI). The results of a feasibility study for the development of an incurred CRM for the mass fraction of nitrofuran metabolites in chicken muscles are presented in this work. A small-scale batch of material was produced from freeze-dried chicken breast muscles containing residues of 3-amino-2-oxazolidinone (AOZ) and 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ) metabolites after the controlled in vivo administration of furazolidone and furaltadone antibiotics. A small-scale batch from a blank matrix, without the metabolites, was also produced. The granulometry, stability of residual moisture content, effect of the treatment by irradiation at 3 kGy, 5 kGy and 7 kGy, and degree of inhomogeneity of the property values and residual moisture were evaluated. All statistical approaches for homogeneity and stability assessments were performed based on the principles of ISO Guide 35:2006. [ABSTRACT FROM AUTHOR]