Colorants

(Zn_1−xCo_x)₃Mo₂O₉ (0 ≤ x ≤ 0.15) samples were synthesized as novel inorganic violet pigments by a conventional solid-state reaction method, and the obtained powders were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), ultraviolet and visible (UV-Vis) diffuse reflectance spectroscopy, and L*a*b*Ch° chromatic coordinates. The Co²⁺-doped samples showed optical absorption at wavelengths of 500−560 and 680 nm, which were attributed to the d–d transitions of Co²⁺, resulting in a violet color. The absorption intensity increased with increasing the Co²⁺ concentration. The most vibrant violet color was obtained with a composition of (Zn_0.90Co_0.10)₃Mo₂O₉.

Regulatory alerts regarding unauthorized use of colorants in food are frequently issued, often involving excessive concentration, improper declaration, or prohibited dyes. The illegal use of reactive textile dyes in food-related coloring preparations remains largely unrecognized, but confirmed cases have been reported in 2016 and 2020 and most recently in May 2025. This work presents the qualitative analyses’ results of a blue coloring powder for food use with regard to reactive dyes. The sample was labeled as a natural product, although it exhibited the color stability typical of artificial dyes. Prompting further investigation, combined spectroscopic, chromatographic and mass spectrometric methods were applied for the characterization and comparison with reference samples. In agreement with all analyses performed, strong evidence was found that the blue coloring powder contained several identical constituents with a reference sample of Reactive Blue 21. The overall composition suggests that both are complex mixtures of different phthalocyanines, suspected byproducts of synthesis, and various unknown compounds, rendering the powder unsuitable for human consumption. These findings emphasize the importance of tightened analytical controls regarding the unauthorized addition of textile dyes to food in order to maintain consumer safety.

This research investigates the biosynthesis optimization of the red pigment prodigiosin produced by Serratia marcescens 11E through submerged fermentation utilizing an alternative cheese whey-based medium, focusing on process parameters and antimicrobial properties. Four types of whey sourced from a local dairy industry were characterized, and the fermentation conditions were optimized using Plackett–Burman and central composite design methodologies, yielding up to 1.43 g/L of prodigiosin under optimal conditions, 25 °C, 200 rpm, pH 7, and 48 h of dark incubation, with whey serving as the sole carbon source. Normalization to biomass yielded 110 mg of prodigiosin per gram of dried cell weight (post-optimization), enabling meaningful comparison with prior studies. Pigment extraction was performed with acidic methanol, and identity was confirmed by UV–Vis spectrophotometry and Fourier transform infrared spectroscopy (FTIR). The antimicrobial activity of the purified pigment was also evaluated. Although cheese whey has significant nutritional value, nearly half of the global production is discarded due to high treatment costs. This study demonstrates that whey can be repurposed as a sustainable and economical fermentation medium for pigment production, which is compatible with dairy plants. This makes it a promising solution to address the underutilization of whey by cheese local producers in Mexico. Prodigiosin has diverse industrial applications, including antimicrobial, insecticidal, and antioxidant properties. These findings highlight the potential for dairy waste valorization in a circular bioeconomy, reducing environmental impacts and promoting the creation of valuable bioproducts.