Percorrer por autor "Machado, Joana Filipa Horta"
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- Bioactivity of highly hydrolytic bacteria isolated from Chiapas Cheese : MéxicoPublication . Machado, Joana Filipa Horta; Jauregi, Paula; Pintado, ManuelaLactic acid bacteria (LAB) are widely used in food industry. This group of microorganisms not only have the ability to produce lactic acid, which contributes to the taste and texture of fermented products but also show the capability to produce, during milk fermentation, bioactive peptides that can be important in human health by having antihypertensive, antimicrobial, antioxidative, antithrombotic and mineral-binding activities. Chiapas cream cheese, a traditional type of Mexican cheese, is obtained through a prolonged acid-enzymatic coagulation of cow raw milk and has unique sensory characteristics due to the endogenous LAB in milk from this region. Thus, the aim of this project was to select and study the bioactivity of high hydrolytic isolates from Chiapas cheese. An initial selection from 84 isolates was made for production of diacetyl and a negative production of catalase. Further analysis to measure the degree of hydrolysis and to obtain the peptide profile was carried out. Selected isolates were compared to Lactobacillus helveticus DSM 13137 and used to study the potential activity of peptides released through lactic fermentation. The antioxidant properties of whey fractions, after 24h and 48h of fermentation in reconstituted skimmed milk (RSM), were evaluated by two spectrophotometric methods. Scavenging of the cation radical of 2, 2’-Azino-Bis (3– Ethylbenzthiazoline–6-Sulfonic Acid) (ABTS) ranged from 50%-86% while ferric reducing antioxidant power assay presented variable FRAP values among the selected strains. An angiotensin-converting enzyme (ACE) inhibitory assay by HPLC was performed showing inhibitions by average mean of 75% in the isolates compared to 96% in DSM 13137. The potential inhibitory effects of the bioactive peptides produced by the selected isolates were also tested against some food-poisoning pathogenic organisms: Escherichia coli, Salmonella Typhi, Salmonella Enteritidis and Listeria monocytogenes, using the paper disc method, showing cases with inhibitory zones by average mean of 12 mm diameter zone. The results indicated suggest that these strains could have applications as starters in dairy industry and as a source of new bioactive peptides with different modes of action.