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Novel, edible melanin-protein-based bioactive films for cheeses: antimicrobial, mechanical and chemical characteristics
Publication . Ferraz, Ana Rita; Goulão, Manuela; Santo, Christophe E.; Anjos, Ofélia; Serralheiro, Maria Luísa; Pintado, Cristina M. B. S.
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 g/mL) and M2 (500 g/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.
The cheese rind brownish pigmentation : source, chemical characterization, bioactivities, and new cheese active packing
Publication . Ferraz, Ana Rita; Serralheiro, Maria Luísa Mourato de Oliveira Marques; Pintado, Cristina Maria Baptista Santos
Cheese is a type of food that has been used over time as a way of preserving milk. It is a very consumed food due to its flavor and versatility. For some years, popular cases of color defects in cheeses surfaces have been reported in the literature. Sporadic inconsistencies in cheese appearance may result in a downgrading of cheese and a consequential economic loss to producers. The dairy industry may be a good source of bacteria strains producing natural pigments.
Pigments are compounds of importance to various industries, for example the food industry, where they can be used as additives, colour enhancers and antioxidants. As the current trend around the world is shifting towards the use of environmentally friendly products, the demand for natural dyes is increasing. Melanins are pigments produced by various microorganisms. Pseudomonas putida ESACB 191, isolated from goat cheese rind, has been described as a brown pigment producer. This strain produces a brown pigment in synthetic Müeller-Hinton broth. This brown compound was extracted, purified, analysed by FTIR and mass spectrometry, and identified as eumelanin. The maximum volumetric productivity obtained was 1.57 mg/L/h. The bioactivity of eumelanin was evaluated as the free radical scavenging capacity (antioxidant activity), EC50 of 74.0 ± 0.2 µg/mL, when determined using DPPH test and as an acetylcholinesterase inhibitor, with IC50 575 ± 4 µg/mL. This bacterial eumelanin showed no 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 on cholesterol absorption across a simulated intestinal barrier formed by the Caco2 cell line or with the drug ezetimibe.
Cynara cardunculus L. inflorescence infusion has been used for several centuries as coagulating agent to obtain curd in traditional cheese making, in 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 present in the plant leaves), and rosmarinic acid (RA) (a similar phenolic compound) aqueous solutions were tested for antimicrobial activity against bacteria that may appear on the cheese rind. The antimicrobial activity was evaluated using 15 bacterial strains utilizing 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 growths 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.
The cheese rind is the natural active packaging of cheese and is subject to a wide range of external factors that compromise the appearance of the cheese, namely, color defects caused by spoilage microorganisms. To avoid the formation of brown rind due to microorganism spoilage eight films based on whey protein isolate (WPI) coatings were studied, of which IS3CA (WPI 5%+sorbitol 3%+citric acid 3%) was selected due to 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 in 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. The novel melanin edible films also give the cheese a brown, uniform coating that contributes to improving the appearance of the cheese making it more attractive to the consumer.
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Fundação para a Ciência e a Tecnologia
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SFRH/BD/135692/2018