| Autor: |
Enache, Elena, Kataoka, Ai, Glenn Black, D., Napier, Carla D., Podolak, Richard, Hayman, Melinda M. |
| Zdroj: |
Journal of Food Protection; June 2015, Vol. 78 Issue: 6 p1106-1112, 7p |
| Abstrakt: |
The objective of this study was to obtain dry inocula of SalmonellaTennessee and Enterococcus faecium,a surrogate for thermal inactivation of Salmonellain low-moisture foods, and to compare their thermal resistance and stability over time in terms of survival. Two methods of cell growth were compared: cells harvested from a lawn on tryptic soy agar (TSA-cells) and from tryptic soy broth (TSB-cells). Concentrated cultures of each organism were inoculated onto talc powder, incubated at 35°C for 24 h, and dried for additional 24 h at room temperature (23 ± 2°C) to achieve a final water activity of #0.55 before sieving. Cell reductions of Salmonellaand E. faeciumduring the drying process were between 0.14 and 0.96 log CFU/g, depending on growth method used. There was no difference between microbial counts at days 1 and 30. Heat resistance of the dry inoculum on talc inoculated into a model peanut paste (50% fat and 0.6 water activity) was determined after 1 and 30 days of preparation, using thermal death time tests conducted at 85°C. For Salmonella,there was no significant difference between the thermal resistance (D85°c) for the TSB-cells and TSA-cells (e.g. day 1 cells D85°C= 1.05 and 1.07 min, respectively), and there was no significant difference in D85°Cbetween dry inocula on talc used either 1 or 30 days after preparation (P >0.05). However, the use the dry inocula of E. faeciumyielded different results: the TSB-grown cells had a significantly (P< 0.05) greater heat resistance than TSA-grown cells (e.g. D85°Cfor TSB-cells = 3.42 min versus 2.60 min for TSA-cells). E. faeciumhad significantly (P< 0.05) greater heat resistance than SalmonellaTennessee regardless what cell type was used for dry inoculum preparation; therefore, it proved to be a conservative but appropriate surrogate for thermal inactivation of Salmonellain low-moisture food matrices under the tested conditions. |
| Databáze: |
Supplemental Index |
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