Effectiveness of Irradiation Treatment in Eliminating E. coli O157:H7 and Salmonella in Dried Organic Herb Samples Intended for Use in Blended Tea

Abstract

Abstract:Blended tea with different herbs, seeds and dehydrated vegetable substances bring a world of flavours, aromas and colours to tea. Tea is usually made with dried tea leaves, or blended with other dried herbs and pouring boiling water over the leaves and letting them stay for a few minutes and then sip. This study was done to evaluate the microbial contamination of dried organic lemongrass, mint and jasmine samples intended to prepare flavoured tea and also to see the effect of gamma irradiation in inactivating microorganisms in dried organic herbs (lemongrass, mint and jasmine) samples intended to prepare flavoured tea. Presence of higher number of generic E. coli and pathogenic E. coli O157:H7 in dried organic lemongrass, mint, and jasmine samples, and blended tea samples were observed. No Salmonella was detected in dried lemongrass sample; however, presence of Salmonella was evident in mint and jasmine samples. Application of 2.0 kGy irradiation dose was able to successfully eliminate the pathogenic E. coli O157:H7 and Salmonella in lemongrass, mint and jasmine samples. In addition, the aerobic bacterial count was also reduced to <100 CFU/g in dried lemongrass or other tea samples. This finding suggested that application of 2.0 kGy dose of irradiation could successfully eliminate the pathogens and provide safe food with lower bacterial content compared to non-irradiated herbs for human consumption.

Microbiological quality of different tea grades produced in diverse agro-climatic regions in Sri Lanka

“…Coliform bacteria were detected in 20 % of samples [ 9 ]. However, generic E. coli and pathogenic E.coli 0157:H7 were detected in dried tea samples [ 31 ]. Anosike and Oranusi (2018) [ 32 ] also reported that bacterial counts ranged from 1.7 × 10 2 to 4.5 × 10 2 cfu/g in tea samples collected from the Nigerian retail market.…”

Microbial decontamination of gamma irradiated black tea and determination of major minerals in black tea, fresh tea leaves and tea garden soil

“…The total fecal coliform levels present in each sample were determined based on the method described by Zaman, Alam, Mortuza, and Bari (2015). Briefly, approximately 1 g of each sample was homogenized in 225 mL of an enterobacteria enriched broth-Mossel pre-enrichment medium (Oxoid Ltd, Hampshire, England) followed by incubation at 35 C for 24 h. Then, 1 mL of pre-enriched cultures were mixed with 9 mL of 2X Escherichia coli (E. coli) medium (Nissui Co. Ltd., Tokyo, Japan) followed by incubation at 35 C for 24 h. To confirm the presence of fecal coliform, one loop of the culture was inoculated in 10 mL of 1X (E. coli) medium with a Durham fermentation tube followed by incubation for 20 h at 42 C. The production of gas in the tube confirms the presence of fecal coliform.…”