Zhang Yangjunna, Keller Susanne E, Grasso-Kelley Elizabeth M
1 Illinois Institute of Technology, Institute for Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501.
2 U.S. Food and Drug Administration, 6502 South Archer Road, Bedford Park, Illinois 60501, USA.
J Food Prot. 2017 Jun;80(6):940-946. doi: 10.4315/0362-028X.JFP-16-507.
Tahini, a low-moisture food that is made from sesame seeds, has been implicated in outbreaks of salmonellosis. In this study, the fate of Salmonella was determined through an entire process for the manufacture of tahini, including a 24-h seed soaking period before roasting, subsequent grinding, and storage at refrigeration temperature. Salmonella populations increased by more than 3 log CFU/g during a 24-h soaking period, reaching more than 7 log CFU/g. Survival of Salmonella during roasting at three temperatures, 95, 110, and 130°C, was assessed using seeds on which Salmonella was grown. Salmonella survival was impacted both by temperature and the water activity (a) at the beginning of the roasting period. When roasted at 130°C with a high initial a (≥0.90) and starting Salmonella populations of ∼8.5 log CFU/g, populations quickly decreased below detection limits within the first 10 min. However, when the seeds were reduced to an a of 0.45 before roasting at the same temperature, 3.5 log CFU/g remained on the seeds after 60 min. In subsequent storage studies, seeds were roasted at 130°C for 15 min before processing into tahini. For the storage studies, tahini was inoculated using two methods. The first method used seeds on which Salmonella was first grown before roasting. In the second method, Salmonella was inoculated into the tahini after manufacture. All tahini was stored for 119 days at 4°C. No change in Salmonella populations was recorded for tahini throughout the entire 119 days regardless of the inoculation method used. These combined results indicate the critical importance of a during a roasting step during tahini manufacture. Salmonella that survive roasting will likely remain viable throughout the normal shelf life of tahini.
芝麻酱是一种由芝麻制成的低水分食品，曾与沙门氏菌病的暴发有关。在本研究中，通过芝麻酱制造的整个过程来确定沙门氏菌的去向，包括烘烤前24小时的种子浸泡期、随后的研磨以及在冷藏温度下储存。在24小时的浸泡期内，沙门氏菌数量增加了超过3个对数CFU/克，达到超过7个对数CFU/克。使用接种了沙门氏菌的种子评估了在95、110和130°C三个温度下烘烤期间沙门氏菌的存活情况。烘烤开始时的温度和水分活度（a）均会影响沙门氏菌的存活。当在初始a较高（≥0.90）且起始沙门氏菌数量约为8.5个对数CFU/克的情况下于130°C烘烤时，在最初10分钟内菌数迅速降至检测限以下。然而，当种子在相同温度下烘烤前水分活度降至0.45时，60分钟后种子上仍残留3.5个对数CFU/克。在随后的储存研究中，种子在加工成芝麻酱之前于130°C烘烤15分钟。对于储存研究，芝麻酱采用两种方法接种。第一种方法是使用在烘烤前先接种沙门氏菌的种子。第二种方法是在制造后将沙门氏菌接种到芝麻酱中。所有芝麻酱在4°C下储存119天。无论采用何种接种方法，在整个119天中，芝麻酱中的沙门氏菌数量均未记录到变化。这些综合结果表明了在芝麻酱制造过程中烘烤步骤期间水分活度的至关重要性。在烘烤中存活下来的沙门氏菌很可能在芝麻酱的正常保质期内一直保持存活。
