A study of the antimicrobial activity of combined black pepper and cinnamon essential oils against Escherichia fergusonii in traditional African yoghurt
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AbstractThe antimicrobial activity of the essential oils of black pepper (BPE) and cinnamon bark (CE) extracts against E. fergusonii was assessed in pasteurized full cream milk during and post-fermentation. The milk was fermented with 1% (v/v) of Lactobacillus delbrueckii subspecies bulgaricus (NCIMB 11778) and Streptococcus thermophilus (NCIMB 10387) (approx. 106 cfu/mL each) and incubated and stored at 25 °C for 5 days (144 h) or at 43 °C for 24 h and then stored at 25 °C for 120 h. The milk was spiked with E. fergusonii at the start of fermentation by the lactic acid bacteria (pre-fermentation contamination) for after fermentation (post fermentation contamination). BPE and CE were applied at concentrations based on their minimum inhibitory concentration of 0.5% and 0.25% respectively as follows: 0.5% BPE alone; 0.125% BPE with 0.1875% CE; 0.25% BPE with 0.125% CE; 0.375% BPE with 0.0625% CE; 0.25% CE alone. Results showed that during fermentation at 25 °C, E. fergusonii grew to a similar level (approx. 109 CFU/mL) in control samples and 108 CFU/mL when BPE or CE were added alone. Whereas, in the samples with the combined essential oils, the bacterium grew to 106–107 CFU/mL only. During the milk fermentation at 43 °C, E. fergusonii grew to approx. 109 CFU/mL in samples without treatment. However, it was not detected in samples containing mixed BPE with CE after 8, 10 and 12 h of fermentation. Subsequent storage at 25 °C resulted in undetectable levels of the bacterium in all the samples treated with BPE or CE after 24 h of storage. These results indicated that BPE in combination with CE reduced growth during fermentation and was bactericidal during storage.
CitationOgwaro, B.A., O’Gara, E.A., Hill, D.J., Gibson, H. (2021) A Study of the Antimicrobial Activity of Combined Black Pepper and Cinnamon Essential Oils against Escherichia fergusonii in Traditional African Yoghurt. Foods. 2021; 10(11):2847. https://doi.org/10.3390/foods10112847
Description© 2021 The Authors. Published by MDPI. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3390/foods10112847
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