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.
Department of Food and Environmental Hygiene, College of Veterinary Medicine, Helsinki, Finland.
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H
Korkeala
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Alanko
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P
Mäkelä
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S
Lindroth
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