Potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) frequently coexist in soils near industrial areas and sometimes in environmental compartments directly linked to feed (forage) and food (milk) production. However, the distribution of these pollutants along the dairy farm production chain is unclear. Here, we analyzed soil, forage, and milk samples from 16 livestock farms in Spain: several PTEs and PAHs were quantified. Farms were compared in terms of whether they were close to (5 km) industrial areas. The results showed that PTEs and PAHs were enriched in the soils and forages from farms close to industrial areas, but not in the milk. In the soil, the maximum concentrations of PTEs reached 141, 46.1, 3.67, 6.11, and 138 mg kg⁻¹ for chromium, arsenic, cadmium, mercury, and lead, respectively, while fluoranthene (172.8 µg kg⁻¹) and benzo(b)fluoranthene (177.4 µg kg⁻¹) were the most abundant PAHs. Principal component analysis of the soil PTEs suggested common pollution sources for iron, arsenic, and lead. In the forage, the maximum contents of chromium, arsenic, cadmium, mercury, and lead were 32.8, 7.87, 1.31, 0.47, and 7.85 mg kg⁻¹, respectively. The PAH found in the highest concentration in the feed forage was pyrene (120 µg kg⁻¹). In the milk, the maximum PTE levels were much lower than in the soil or the feed forages: 74.1, 16.1, 0.12, 0.28, and 2.7 µg kg⁻¹ for chromium, arsenic, cadmium, mercury, and lead, respectively. Neither of the two milk samples exceeded the 20 µg kg⁻¹ limit for lead set in EU 1881/2006. Pyrene was the most abundant PAH found in the milk (39.4 µg kg⁻¹), while high molecular weight PAHs were not detected. For PTEs, the results showed that soil–forage transfer factors were higher than forage–milk ratios. Our results suggest that soils and forages around farms near industries, as well as the milk produced from those farms, have generally low levels of PTE and PAH contaminants.

Breast milk is an optimal food that covers all the nutritional needs of the newborn. It is a dynamic fluid whose composition varies with lactation period. The neonatal units of hospitals have human milk banks, a service that analyzes, stores, and distributes donated human milk. This milk is used to feed premature infants (born before 32 weeks of gestation or weighing less than 1500 g) whose mothers, for some reason, cannot feed them with their own milk. Here, we aimed to develop near-infrared spectroscopy (NIRS) measures for the analysis of breast milk. For this purpose, we used a portable NIRS instrument scanning in the range of 1396–2396 nm to collect the spectra of milk samples. Then, different chemometrics were calculated to develop 18 calibration models with and without using derivatives and the standard normal variate. Once the calibration models were developed, the best treatments were selected according to the correlation coefficients (r²) and prediction errors (SECVs). The best results for the assayed macronutrients were obtained when no pre-treatment was applied to the NIR spectra of fat (r² = 0.841, SECV = 0.51), raw protein (r² = 0.512, SECV = 0.21), and carbohydrates (r² = 0.741, SECV = 1.35). SNV plus the first derivative was applied to obtain satisfactory results for energy (r² = 0.830, SECV = 9.60) quantification. The interpretation of the obtained results showed the richness of the NIRS spectra; moreover, the presence of specific bands for fat provided excellent statistics in quantitative models. These results demonstrated the ability of portable NIRS sensors in a methodology developed for the quality control of macronutrients in breast milk.

Sustainable dairy farms are characterised by the self-production of forage for animal feed. These farms are sometimes located near industrial areas, entailing a risk of food chain contamination with hazardous metals and polycyclic aromatic hydrocarbons (PAHs). Accordingly, evaluating the impact of pollution on forage and milk is of great interest. In this study, the effects of industrial factors on sustainable forage from 43 dairy farms and possible correlations between inorganic elements and PAHs were studied. Spearman's correlation and principal component analysis (PCA) were performed for the forage and milk. Most of the inorganic elements in the forage were below the maximum residual limits for cadmium (Cd) and lead (Pb), established in EU 2013/1275 and EU 2019/1869, respectively. However, arsenic (As) and mercury (Hg) levels were above their respective limits in the forage (EU 2019/1869). No milk samples exceeded the maximum residual limits for Pb (EU 488/2014) or Cd (EU 1881/2006) in dairy products. Heavy-weight PAHs (HW-PAHs, four or more aromatic rings) were detected in forage but not in milk. In the forage samples, HW-PAHs were positively correlated with Zn and Cd. In addition, some hazardous metals (chromium (Cr), iron (Fe), As, Hg, and Pb) also were positively correlated with Zn and Cd. Interestingly, no correlations were found between forage pollutants and milk, suggesting that these pollutants have a low transfer rate to milk. The PCA results highlighted the predominant contribution of PAHs to the global variance in forage samples collected at different distances from industrial areas. In milk, the contributions of hazardous metals and PAHs were more balanced than in forages. Finally, when distances to potential pollution sources were included in the PCA of forage samples, a negative correlation was observed between the former and the concentrations of HW-PAHs, Cd, and Zn, suggesting that thermal power plants and steel factory emissions were the main sources of polluting forage in this area.

Aflatoxin M1 (AFM1) is one of the most widespread aflatoxins that can be present in the milk of lactating mammals. It can cause carcinogenicity, mutagenesis, teratogenesis, genotoxicity and immunosuppression. The WHO recommends reducing the AFM1 concentration in food products, so the European Commission has set a maximum allowable limit of 0.05 µg L⁻¹ in milk and its products. Thus, there is a need to develop new methodologies to satisfy the demand for reliable, cost-effective, robust and sensitive AFM1 routine controls. In the present work, a competitive phosphorescent immunosensor for AFM1 quantification in milk, based on antibody–antigen recognition and Mn:ZnS quantum dots (d-QDs) as photoluminescent labels, has been developed. Two different assay strategies based on the use of d-QDs as labels of secondary antibodies (direct assay), or of a derivative species of the antigen AFM1-Bovine Serum Albumin (indirect assay) were compared in terms of analytical performance for AFM1 quantification. The best analytical results were obtained with the immunoassay format that uses d-QDs as tags of secondary antibodies (direct assay), and said design was finally selected. The selected immunosensor provided a detection limit for AFM1 quantification of only 0.002 µg L⁻¹, which greatly satisfied the maximum tolerable limit of AFM1 in milk of 0.05 µg L⁻¹. The accuracy, calculated as recovery of AFM1 in fortified skimmed milk samples, ranged from 81 to 90%, with relative standard deviations from 3% to 14%. These results bring to light the good performance of such phosphorescent biosensors as simple and fast alternatives to conventional chromatographic analytical methods.