Advisor(s)
Abstract(s)
Winery by-products are a rich source of polyphenols, which have proven to have several beneficial biological
properties, such as, antioxidant and antimicrobial activities. Therefore, this study aimed the extraction of
polyphenols from winery by-products of two Portuguese red grape varieties, Touriga Nacional and Preto
Martinho, and evaluate their phenolic profile, antioxidant properties and antimicrobial activity against antibiotic
resistant bacteria. The polyphenols were extracted from the grapes' skins, seeds and stems. Extracts were
analysed for total phenolic, anthocyanin and tannin contents, and the polyphenol profile was determined by
High Performance Liquid Chromatography. The antioxidant activity of the extracts was determined by ABTS+
and DPPH methods. Antimicrobial susceptibility assay was performed using Kirby-Bauer disc diffusion method.
Preto Martinho variety presented a higher polyphenolic content than Touriga Nacional. Malvidin 3-O-glucoside
was the most abundant compound found in the skins extracts in both varieties. The main phenolic compound
found in the seeds and stems extracts was catechin. From the several flavonols quantified, rutin was the most
abundant. For both varieties, the seeds extracts showed the highest antioxidant and antimicrobial properties,
followed by the stems extracts. The extracts showed antibacterial activity against all tested strains except on
gram-negative bacteria Salmonella enteritidis, Escherichia coli and Pseudomonas aeruginosa. These results show
that, natural products, such as polyphenols, may represent a source for the development of novel antimicrobials
to combat gram-positive resistant bacteria and possibly be used as natural food preservatives. However, they
were not effective against gram-negative resistant bacteria which shows that polyphenols, alone, might not
substitute antibiotics.
Description
Keywords
Antibacterial activity Antioxidant activity Polyphenols Resistant bacteria Winery by-products
Pedagogical Context
Citation
Silva, Vanessa; Igrejas, Gilberto; Falco, Virgilio; Santos, Teresa P.; Torres, Carmen; Oliveira, Ana M.P.; Pereira, JosĂ© Eduardo; Amaral, Joana S.; Poeta, PatrĂcia (2018). Chemical composition, antioxidant and antimicrobial activity of phenolic compounds extracted from wine industry by-products. Food Control. ISSN 0956-7135. 92, p. 516-522