A total of forty-five samples of three most commonly consumed unsweetened evaporated milk brands purchased from retail outlets in South-western Nigeria were examined for occurrence of spore-forming bacteria. All the samples had high numbers of spore-forming bacteria of the genera
Bacillus spp and
Clostridium spp. with mean total aerobic viable counts of 2.15x10
5cfuml
-1 for brand A, 0.95x10
5cfuml
-1 for brand B and 0.69x10
5cfuml
-1 for brand C. Total anaerobic plate counts ranged from 0.13x10
5 for brand C, to 0.54x10
5 for brand B and 1.67x10
5 for brand A. The organisms isolated from the three brands were identified as
Bacillus cereus
,
Bacillus licheniformis
,
Bacillus coagulans
,
Bacillus stearothermophilus
,
Bacillus subtilis
and
Clostridium perfringens
, with
B. subtilis having the highest frequency of occurrence (93.33%). Samples were subjected to four different pasteurization treatments: 55°C for 30 min, 80°C for 15 min, 90°C for 10 min and 120°C for 30 sec, to determine a more efficient process. No growth was observed on culture plates of samples pasteurized at 120°C for 30 sec, except on aerobic plates of brand A. However the milk samples treated under this regime curdled. Samples pasteurized at 80°C for 15 min recorded the least counts next to samples treated at 120°C for 30 sec, without causing the samples to curdle.
