Pigments are compounds of importance to several industries, for instance, the food industry, where they can be used as additives, color intensifiers, and antioxidants. As the current trend around the world is shifting to the use of eco-friendly commodities, demand for natural dyes is increasing. Melanins are pigments that are produced by several microorganisms. Pseudomonas putida ESACB 191, isolated from goat cheese rind, was described as a brown pigment producer. This strain produces a brown pigment via the synthetic Müeller-Hinton Broth. This brown compound was extracted, purified, analyzed by FTIR and mass spectrometry, and identified as eumelanin. The maximum productivity was 1.57 mg/L/h. The bioactivity of eumelanin was evaluated as the capacity for scavenging free radicals (antioxidant activity), EC50 74.0 ± 0.2 μg/mL, and as an acetylcholinesterase inhibitor, with IC50 575 ± 4 μg/mL. This bacterial eumelanin did not show cytotoxicity towards A375, HeLa Kyoto, HepG2, or Caco2 cell lines. The effect of melanin on cholesterol absorption and drug interaction was evaluated in order to understand the interaction of melanin present in the cheese rind when ingested by consumers. However, it had no effect either on cholesterol absorption through an intestinal simulated barrier formed by the Caco2 cell line or with the drug ezetimibe.

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The cheese rind is the natural food packaging of cheese and is subject to a wide range of external factors that compromise the appearance of the cheese, including color defects caused by spoilage microorganisms. First, eight films based on whey protein isolate (WPI) coatings were studied, of which IS3CA (WPI 5% + sorbitol 3% + citric acid 3%) was selected for presenting better properties. From the IS3CA film, novel films containing melanin M1 (74 µg/mL) and M2 (500 µg/mL) were developed and applied to cheese under proof-of-concept and industrial conditions. After 40 days of maturation, M2 presented the lowest microorganism count for all the microbial parameters analyzed. The cheese with M2 showed the lowest lightness, which indicates that it is the darkest cheese due to the melanin concentration. It was found that the mechanical and colorimetric properties are the ones that contribute the most to the distinction of the M2 film in cheese from the others. Using FTIR-ATR, it was possible to distinguish the rinds of M2 cheeses because they contained the highest concentrations of melanin. Thus, this study shows that the film with M2 showed the best mechanical, chemical and antimicrobial properties for application in cheese.

Cynara cardunculus L. inflorescence infusion has been used for several centuries as curd in traditional cheese making, such as some highly prized Portuguese cheeses. To promote the sustainable use of all C. cardunculus plants, C. cardunculus extract leaves decoction (CL), inflorescence decoction (CI), chlorogenic acid (CA) (a compound in the plant leaves), and rosmarinic acid (RA) (a similar phenolic compound) solutions were tested for antimicrobial activity against bacteria that may appear on the cheese rind. The antimicrobial activity was evaluated by 15 bacterial strains using two different methodologies: solid and liquid. The influence of these extracts and the phenolic compounds on melanin bioproduction by Pseudomonas putida ESACB 191 was also studied. CA and RA (1 mg/mL) showed antimicrobial activity. CL and CA reduced P. putida ESACB 191 growth in the liquid assay and melanin bioproduction by 6.20 Log CFU/mL and 50%, respectively. Cynarin, CA, and its derivates were identified as the main phenolic compounds (52%) of CL, which may justify its inhibitory action on bacterial growth and melanin bioproduction. Thus, future perspectives include the application of CL extracts with antimicrobial activity in edible films and/or coatings to applied in cheese rind to increase the shelf time.