The yeasts and their chemical changes in the British fresh sausage.

  • Hilary Karen Dalton

Student thesis: Doctoral ThesisPhD

Abstract

Seven hundred and seventeen yeasts isolated from samples of sulphited and unsulphited sausage, skinless sausage, minced beef, and ingredients intended for sausage manufacture, as well as air and equipment in a sausage factory were characterised in detail. Debaryomyces hansenii was the most commonly occurring yeast in the majority of samples of sausage and minced beef, followed by Candida zeylainoides and Pichia membranaefaciens. The presence of sulphite did not appear to influence the overall numbers or range of yeasts in sausage but did affect their relative proportions such that the incidence of D. hansenii was higher and that of certain Cryptoccoccus and Rhodotorula spp. was lower in samples containing the preservative. The heat treatment of skinless sausages during processing appeared to reduce the incidence of D. hansenii. The factory survey showed that the meat intended for sausage manufacture and also other ingredients as well as equipment harboured the same range of yeasts as were found in the finished product. A yeast flora dominated by Trichosporon cutaneum was isolated from pig carcasses immediately following slaughter. This flora was found to be confined largely to the equipment and air of the slaughter area and lairage. In general, the yeast flora of sausage was non-fermentative but could assimilate a wide range of carbohydrates. Selected strains of C. curvata, C. lipolytica var. lipolytica, C. zeylanoides, Cr. albidus, D. hansenii, P. membranaefaciens and Torulopsis candia were shown to synthesise either extra cellular lipases and/or amylases but not proteases in broth culture. Sulphite binding compounds, principally acetaldehyde, were produced in lab lemco broth (pH 7.0) containing sulphite (500 mug g-1) during the exponential phase of growth of representative strains of D. hansenii, C. zeylanoides, P. membranaefaciens and T. candida but not Cr. albidus var. albidus and Rh. rubra. The extent of sulphite binding in minced pork- belly supplemented with sulphite (500 mug g-1) was appreciably greater in samples inoculated with D. hansenii than in those inoculated with representatives of the other members of the microbial association, Brochothrix thermosphacta, Lactobacillus sp. and a pseudomonad. The content of sulphite binding agents in minced pork was found to be positively related (r = 0.98, 0.92 at 1 and 15°C respectively) to the size of the yeast population. The concentration of acetaldehyde in stored sausages obtained from a factory and also those obtained from retail outlets was correlated with the concentration of bound sulphite (r = 0.89). The rate and extent of sulphite binding and acetaldehyde production was fastest during the exponential phase of yeast growth in sausages.
Date of Award1985
LanguageEnglish
Awarding Institution
  • University of Bath

Cite this

The yeasts and their chemical changes in the British fresh sausage.
Dalton, H. K. (Author). 1985

Student thesis: Doctoral ThesisPhD