ABSTRACT
AIMS: To evaluate the potential for developing a quality index for a Danish modified atmosphere packaged (MAP) heat-processed and naturally contaminated pork meat product stored at 5 degrees C. METHODS AND RESULTS: The composition of the predominating microflora and changes in contents of tyramine, arginine, organic acids and sensory characteristics were analysed. The microflora was predominated by Lactobacillus sakei, Leuconostoc carnosum and Carnobacterium divergens. The presence of each species varied between products and batches resulting in limited usefulness of the concentrations of these bacteria or their metabolites as indices of quality. Furthermore, the three species differed in their metabolic activities as shown by use of a model meat extract. However, when MAP storage of the processed pork product was followed by aerobic storage then acetic acid showed some potential as a chemical indicator of sensory quality. CONCLUSION: Variation in processing parameters and spoilage microbiota limited the usefulness of concentrations of micro-organisms and their metabolites as indices of spoilage for the studied processed MAP pork product. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study contributes to an understanding of the difficulties experienced in developing quality indices to be used in the control of microbial spoilage of processed MAP meat products.
Subject(s)
Food Contamination , Food Microbiology , Lactobacillaceae/isolation & purification , Meat Products/microbiology , Animals , Colony Count, Microbial , Consumer Product Safety , Food Handling/methods , Meat Products/analysis , Pilot Projects , Swine , TemperatureABSTRACT
Three lactic acid bacterial (LAB) strains obtained from a Malaysian acid-fermented condiment, tempoyak (made from pulp of the durian fruit), showed analogous but distinct patterns after screening by SDS-PAGE of whole-cell proteins and comparison with profiles of all recognized LAB species. 16S rRNA gene sequencing of one representative strain showed that the taxon belongs phylogenetically to the genus Leuconostoc, with its nearest neighbour being Leuconostoc fructosum (98 % sequence similarity). Biochemical characteristics and DNA-DNA hybridization experiments demonstrated that the strains differ from Leuconostoc fructosum and represent a single, novel Leuconostoc species for which the name Leuconostoc durionis sp. nov. is proposed. The type strain is LMG 22556(T) (= LAB 1679(T) = D-24(T) = CCUG 49949(T)).
Subject(s)
Condiments/microbiology , Food Microbiology , Glucose/metabolism , Leuconostoc/classification , Leuconostoc/isolation & purification , Bacterial Proteins/analysis , Bacterial Proteins/isolation & purification , DNA, Bacterial/chemistry , DNA, Bacterial/isolation & purification , DNA, Ribosomal/chemistry , DNA, Ribosomal/isolation & purification , Electrophoresis, Polyacrylamide Gel , Genes, Bacterial , Genes, rRNA , Leuconostoc/chemistry , Leuconostoc/metabolism , Molecular Sequence Data , Nucleic Acid Hybridization , Phylogeny , Proteome , RNA, Bacterial/genetics , RNA, Ribosomal, 16S/genetics , Sequence Analysis, DNAABSTRACT
AIMS: To evaluate the microbial spoilage, formation of biogenic amines and shelf life of chilled fresh and frozen/thawed salmon packed in a modified atmosphere and stored at 2 degrees C. METHODS AND RESULTS: The dominating microflora, formation of biogenic amines and shelf life were studied in two series of storage trials with naturally contaminated fresh and thawed modified atmosphere-packed (MAP) salmon at 2 degrees C. Photobacterium phosphoreum dominated the spoilage microflora of fresh MAP salmon at more than 10(6) cfu g(-1) and the activity of this specific spoilage organism (SSO) limited the shelf life of the product to ca 14 and 21 d in the two experiments. Despite the high levels of P. phosphoreum, less than 20 mg kg(-1) histamine was observed in fresh MAP salmon prior to sensory spoilage. Freezing eliminated P. phosphoreum and extended the shelf life of MAP salmon at 2 degrees C by 1-2 weeks. Carnobacterium piscicola dominated the spoilage microflora of thawed MAP salmon and probably produced the ca 40 mg kg(-1) tyramine detected in this product at the end of its shelf life. CONCLUSIONS: Photobacterium phosphoreum dominated the spoilage microflora of fresh MAP salmon but produced only small amounts of biogenic amines in this product. The elimination of P. phosphoreum by freezing allowed this bacteria to be identified as the SSO in fresh MAP salmon. SIGNIFICANCE AND IMPACT OF THE STUDY: The identification of P. phosphoreum as the SSO in fresh MAP salmon facilitates the development of methods to determine and predict the shelf life of this product, as previously shown with fresh MAP cod.
