Extension of shelf-life of Brassica oleracea using ethanol extracts of Citrus aurantifolia

Abstract

Many studies have been conducted on the use of plant extracts to control microbial surface contamination of foods, enhance product microbial safety and extend its shelf life. The study was designed to extend the shelf- life of Brassica oleracea using ethanol extract of Citrus aurantifolia. The phytochemical analysis of the Citrus aurantifolia leaf extract was carried out using gas chromatography–mass spectrophotometry. The chromatogram result revealed the presence of seventy-four (74) bioactive compounds in Citrus aurantafolia. The bioactive compounds present includes alkaloid, phenols, alkenes, alkanes, sesquisterpernoid, alcohol, benzamides, terpenes and phthalic acid. Agar –well diffusion method was used to determine the antimicrobial activities of the plant extract against gram positive bacteria (Staphylococcus aureus, Micrococcus roseus and Bacillus subtillis) and gram-negative bacteria (Pseudomonas aeruginosa, Citrobacter multilinea, Salmonella enterica, Bacillus lichenformis). The extract exhibited both antibacterial and antifungal activities against tested microorganisms. Ethanolic extract of Citrus aurantafolia showed significant antibacterial effect while no inhibitory effect on the antifungal. Staphylococcus appears to be a sensitive strain to the extract. Further studies of the antimicrobial studies were carried using inhibition of total dehydrogenase activity as measure of toxicity C. aurantifolia. The toxicity of the C.aurantifolia leaf extract and Ciprofloxacin on the microbial isolate reveals that Bacillus subtilis was more susceptible to the plant extract than the other microbial isolates. Total microbial counts of the cabbage after 12 days incubation period was used to assess the shelf-life of Brassica oleracea using two samples of the cabbage, identified as Sample A and sample B respectively. The citrus aurantifolia extract has significant effect on the cabbage. The results suggest that the ethanoic extracts of Citrus aurantifolia exhibit a considerable number of phytochemicals and antimicrobials activities. Hence, plant extracts have demonstrated potential as natural antimicrobials and can be used safely as food preservatives.