Survival of Salmonella on Chamomile, Peppermint, and Green Tea during Storage and Subsequent Survival or Growth following Tea Brewing

Author： Keller Susanne E. Stam Christina N. Gradl Dana R. Chen Zhengzai Larkin Emily L. Pickens Shannon R. Chirtel Stuart J.

Publisher： International Association for Food Protection

E-ISSN： 1944-9097|78|4|661-667

ISSN： 0362-028X

Source： Journal of Food Protection, Vol.78, Iss.4, 2015-04, pp. : 661-667

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Abstract

The survival of Salmonella on dried chamomile flowers, peppermint leaves, and green tea leaves stored under different conditions was examined. Survival and growth of Salmonella was also assessed after subsequent brewing using dried inoculated teas. A Salmonella enterica serovar cocktail was inoculated onto different dried tea leaves or flowers to give starting populations of approximately 10 log CFU/g. The inoculum was allowed to dry (at ambient temperature for 24 h) onto the dried leaves or flowers prior to storage under 25 and 35°C at low (<30% relative humidity [RH]) and high (>90% RH) humidity levels. Under the four storage conditions tested, survival followed the order 25°C with low RH > 35°C with low RH > 25°C with high RH > 35°C with high RH. Salmonella losses at 25°C with low RH occurred primarily during drying, after which populations showed little decline over 6 months. In contrast, Salmonella decreased below detection after 45 days at 35°C and high RH in all teas tested. The thermal resistance of Salmonella was assessed at 55°C immediately after inoculation of tea leaves or flowers, after drying (24 h) onto tea leaves or flowers, and after 28 days of storage at 25°C with low RH. All conditions resulted in similar D-values (2.78 ± 0.12, 3.04 ± 0.07, and 2.78 ± 0.56, at 0 h, 24 h, and 28 days, respectively), indicating thermal resistance of Salmonella in brewed tea did not change after desiccation and 28 days of storage. In addition, all brewed teas tested supported the growth of Salmonella. If Salmonella survives after storage, it may also survive and grow after a home brewing process.