Enhancement of antimicrobial activities of whole and sub-fractionated white tea by addition of copper (II) sulphate and vitamin C against 'Staphylococcus aureus'; a mechanistic approach.

WT showed no efficacy in the combinations tested. WTF was enhanced with copper (II) sulphate and further with vitamin C. WT and WTF increased acidity of copper (II) sulphate possibly via the formation of chemical complexes. The difference in WT/WTF absorbance possibly represented substances less concentrated or absent in WTF. Investigations to establish which WTF component/s and in what proportions additives are most effective against target organisms are warranted

Inhibition of <it>Listeria monocytogenes</it> ATCC 19115 on ham steak by tea bioactive compounds incorporated into chitosan-coated plastic films

<p>Abstract</p> <p>Background</p> <p>The consumer demands for better quality and safety of food products have given rise to the development and implementation of edible films. The use of antimicrobial films can be a promising tool for controlling <it>L. monocytogenes</it> on ready to eat products. The aim of this study was to develop effective antimicrobial films incorporating bioactive compounds from green and black teas into chitosan, for controlling <it>L. monocytogenes</it> ATCC 19115 on vacuum-packaged ham steak. The effectiveness of these antimicrobial films was evaluated at room temperature (20°C) for 10 days and at refrigerated temperature (4°C) for 8 weeks.</p> <p>Results</p> <p>The HPLC results clearly show that relative concentrations of catechins and caffeine in green tea ranked EGCG>EGC>CAF>ECG>EC>C while in black tea extracts ranked CAF>EGCG>ECG>EGC>EC>C. The chitosan-coated plastic films incorporating green tea and black tea extracts shows specific markers identified by FTIR. Incorporating natural extracts into chitosan showed that the growth of <it>L monocytogenes</it> ATCC 19115 was inhibited. The efficacy of antimicrobial effect of tea extracts incorporated into chitosan-coated plastic film was dose dependent. However, chitosan-coated films without addition of tea extracts did not inhibit the growth of <it>L. monocytogenes</it> ATCC 19115<it>.</it> Chitosan-coated plastic films incorporating 4% Green tea extract was the most effective antimicrobial, reducing the initial counts from 3.2 to 2.65 log CFU/cm² during room temperature storage and from 3.2 to 1–1.5 log CFU/cm² during refrigerated storage.</p> <p>Conclusions</p> <p>Incorporation of tea extracts into the chitosan-coated films considerably enhanced their effectiveness against <it>L. monocytogenes</it> ATCC 19115. 4% Green tea incorporated into chitosan-coated plastic film had a better antilisterial effect than 2% green tea or 2% and 4% black tea. Data from this study would provide new formulation options for developing antimicrobial packaging films using tea extracts to improve the microbiological safety and quality of ham steak during room and refrigerated storage.</p