Lactic acid and pH as indicators of spoilage for vacuum-packed cooked ring sausages.
Lactic acid production and pH changes of 206 vacuum-packed cooked ring sausages stored at 2, 4 and 12 degrees C from 21 different production runs were monitored as a function of time and of microbial growth. The total lactic acid concentrations and pH values were first at a constant level, starting to increase sharply after the lactobacilli count reached about 5 x 10(7) or 6 x 10(7) cfu/g, respectively. The lactic acid and pH changes as a function of the lactobacilli count were similar at 4 and 12 degrees C. The sharp increase at high lactobacilli counts was observed in both L-lactic acid and D-lactic acid. The variation was lesser and the increase greater in D-lactic acid formation than in L-lactic acid. Above a level of 3-4 mg lactic acid/g most of the samples were deemed unfit. The pH started to decrease from a level of approx. 6.3; below 5.8-5.9 the samples were deemed unfit. The lowest pH value observed was 4.58. Both a high lactic acid content and a low pH indicated that the sausage was spoiled. These changes, however, took place at later stages of storage, and do not give information about the early phase of spoilage.
Korkeala
H
H
Department of Food and Environmental Hygiene, College of Veterinary Medicine, Helsinki, Finland.
Alanko
T
T
Mäkelä
P
P
Lindroth
S
S
D000818:Animals; D015169:Colony Count, Microbial; D003470:Culture Media; D005516:Food Microbiology; D005519:Food Preservation; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000032:analysis*; D019344:Lactic Acid; D007777:Lactobacillaceae / Q000254:growth & development*; D008460:Meat / Q000032:analysis*; D008461:Meat Products / Q000032:analysis*
D003470:Culture Media; D007773:Lactates; D019344:Lactic Acid