1998 Volume 15 Issue 1 Pages 41-46
Normal acidity (pH: 4.11, acetic acid: 0.64%), low acidity (pH: 4.75, acetic acid: 0 .10%) and very low acidity (pH: 5.82, acetic acid: 0.01%) mayonnaises were inoculated with Salmomella Enteritidis (SE) (1.5×107 cfu/g), and stored at 25°C, 2°C and -20°C for 14 days. Normal pH (4.95) and low pH (4.39) cucumber salads were inoculated with SE (1.5×106cfu/g) and stored at 25°C, 2°C and -20°C. The number of SE and the presence of SE in 25g samples were determined periodically.
In the normal acidity mayonnaise, SE decreased rapidly at 25°C and became negative in a 25g sample after 3 days, and at 2°C and -20° decreased gradually but was positive in a 25g sample after 14 days.
In the low acidity mayonnaise, SE decreased more slowly, compared with that in the normal acidity mayonnaise. SE was<10cfu/g at 25°C after 14 days, but positive in a 25g sample. It was 102cfu/g at 2°C after 14 days, and it was 103cfu/g at -20°C after 14 days . In the very low acidity mayonnaise, at 25°C SE increased rapidly (1010cfu/g after 3 days) and maintained high numbers for 14days. At 2° and -20°C the number of SE remained constant for 14 days.
In the normal pH salad, at 25°C, SE increased rapidly (109cfu/g after 1 day) and maintained high numbers for 14 days. At 2°C and -20°C, SE numbers remained constant for 14 days. In the low pH salad, at 25°C, SE decreased gradually and became negative in a 25g sample after 14 days. At -20° C, the decrease of SE was slower (<10cfu/g, positive in 25g sample) and at 2°C the decrease of SE was the slowest (103cfu/g after 14 days).
It was noted that, in storage at -20°C, SE in some low pH (high acidity) foods decreased and sometimes became negative in using a 25g enrichment method.