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Characterization of yeasts associated with Portuguese pork-based products
A Saldanha-da-Gama1, M Malfeito-Ferreira, V Loureiro
1Departamento de Botânica e Engenharia Biológica, Instituto Superior de Agronomia, Tapada da Ajuda, Lisboa, Portugal.
Abstract:
Yeasts from pork-based products, such as country-cured hams and several types of bacon, were studied. Contamination levels ranged from 10(3)-10(9) CFU/g of fat. Identification using a simplified method (SIM) showed that the predominant species were Debaryomyces hansenii, Cryptococcus laurentii, Cryptococcus humicolus, Debaryomyces polymorphus and Pichia guilliermondii. Lipolytic activity was observed in 24 out of 29 of the isolated strains and was not a determinant for attaining high levels of contamination. The analysis of yeast long-chain fatty acid composition for most isolated strains showed a predominance of the acid C18:1 followed by decreasing proportions of the acids C16:0, C18:2, C18:3, C18:0 and C16:1. The fatty acid profiles were roughly similar for all yeasts analyzed suggesting that in these types of pork-based products the yeast lipid composition may have an ecological significance.
Insights
This study identified yeasts in pork products like bacon and ham, finding Debaryomyces hansenii as a dominant species. Yeast fatty acid profiles in these products may hold ecological significance.
Area of Science:
- Food microbiology
- Yeast ecology
- Lipid biochemistry
Background:
- Pork products like country-cured hams and bacon can harbor yeast populations.
- Understanding yeast contamination is crucial for food safety and quality.
- Previous research has not extensively detailed yeast species and their lipid profiles in these specific products.
Purpose of the Study:
- To identify predominant yeast species contaminating pork-based products.
- To investigate the lipolytic activity of isolated yeast strains.
- To analyze the long-chain fatty acid composition of these yeasts and explore its ecological relevance.
Main Methods:
- Isolation and identification of yeasts from various pork products.
- Quantification of yeast contamination levels (CFU/g of fat).
- Simplified Identification Method (SIM) for species determination.
- Gas chromatography analysis of yeast fatty acid profiles.
- Assessment of lipolytic activity in isolated yeast strains.
Main Results:
- Yeast contamination levels in pork products ranged from 10^3 to 10^9 CFU/g of fat.
- Predominant yeast species identified include Debaryomyces hansenii, Cryptococcus laurentii, Cryptococcus humicolus, Debaryomyces polymorphus, and Pichia guilliermondii.
- Lipolytic activity was present in 24 out of 29 isolated strains, but not directly correlated with high contamination levels.
- The dominant fatty acid in yeast isolates was C18:1, followed by C16:0, C18:2, C18:3, C18:0, and C16:1.
- Fatty acid profiles showed similarities across analyzed yeast strains.
Conclusions:
- Debaryomyces hansenii is a significant yeast species found in pork products.
- Lipolytic activity is common but not the sole factor driving high yeast contamination.
- Consistent yeast fatty acid profiles suggest potential ecological roles in pork-based food matrices.
- Further research into yeast lipid composition can elucidate their function in food environments.