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GROWTH AND SURVIVAL OF SALMONELLA IN PARTIALLY SPROUTED PUMPKIN, SUNFLOWER, AND CHIA SEEDS SUBSEQUENTLY DRIED FOR DIRECT CONSUMPTION
Title
GROWTH AND SURVIVAL OF SALMONELLA IN PARTIALLY SPROUTED PUMPKIN, SUNFLOWER, AND CHIA SEEDS SUBSEQUENTLY DRIED FOR DIRECT CONSUMPTION
Creator
Wang, Can
Date
2017, 2017-05
Description
Products based on dried, partially sprouted seeds have been associated with foodborne salmonellosis. Typically, sprouted seeds have been a...
Show moreProducts based on dried, partially sprouted seeds have been associated with foodborne salmonellosis. Typically, sprouted seeds have been a major concern with respect to foodborne illness, but little is known about the risks associated with dried partial sprouted seed products. Previous studies suggest that low-temperature, highhumidity storage conditions may provide an alternative means to inactivate Salmonella for those processors opposed to traditional thermal processing. The objective of this study was to determine the growth of Salmonella during germination of pumpkin, sunflower, and chia seeds, and the survival of Salmonella during drying and storage under variable temperature and relative humidity (RH) conditions. Pumpkin, sunflower, and chia seeds were dry inoculated at 5 log CFU/g with 4 serotype mixture of Salmonella using a dry transfer method, and then soaked in sterile water at 25 and 37°C for 24 h. Salmonella and total aerobic mesophilic plate counts (APC) were determined on xylose lysine deoxycholate (XLD) and tryptic soy agar supplemented with 0.6% yeast extract (TSAYE), respectively. Seeds using this procedure were drained and dried at 25, 51 and 60°C. The water activity (aw) and microbial population of seeds were monitored during drying. Seeds soaked and dried at 25oC were utilized for subsequently storage studies. Portions of dried chia seeds were ground into powder, then pumpkin, sunflower and chia seeds and chia seeds powder were stored at either 37 or 45oC at three different RH levels. The aw and microbial population of seed samples were monitored during storage. During the seed soaking, Salmonella and APC increased approximately 3 log CFU/g. Some decreases were observed at the end of the growth period, as may be expected after stationary phase. Drying at 60oC to a aw of 0.1 resulted in over 6-log CFU/g loss in bacterial population in partially sprouted pumpkin and sunflower seeds, and 5-log CFU/g loss in partially sprouted chia seeds. However, seeds dried at 25oC bring the aw to 0.5 had only approximately a 1-log CFU/g loss in bacterial population. The highest temperature (45oC) and RH (76%) storage condition had the greatest inactivation effect. At 45oC and 76%RH, Salmonella in pumpkin and sunflower seeds were below detection limit after 4 d and 7 d respectively. Salmonella populations in chia seeds and chia seeds powder were still detectable after 7 d regardless of the treatment condition. Salmonella is capable of survival during the manufacture of partially sprouted seeds including both drying and storage steps. Mild thermal treatment coupled with high RH storage condition holds promise for Salmonella inactivation in pumpkin and sunflower seeds but is less effective for chia seeds and chia seeds powder. Dried, partially sprouted seeds that are used as ingredients or consumed directly without further processing are a high-risk food product. Such products must be treated to eliminate foodborne pathogens that may cause foodborne illness.
M.S. in Food Science, May 2017
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