Chrysoula C. Tassou

Meat spoilage during distribution

Meat spoilage during distribution can be considered as an ecological phenomenon that encompasses the changes of the available substrata (e.g., low molecular compounds), during the prevailing of a particular microbial association, the so-called specific spoilage organisms (SSO). In fact, spoilage of meat depends on an even smaller fraction of SSO, called ephemeral spoilage organisms (ESO). These ESO are the consequence of factors that dynamically persist or imposed during, e.g., processing, transportation and storage in the market. Meanwhile spoilage is a subjective judgment by the consumer, which may be influenced by cultural and economic considerations and background as well as by the sensory acuity of the individual and the intensity of the change. Indeed, when spoilage progresses, most consumers would agree that gross discoloration, strong off-odors, and the development of slime would constitute the main qualitative criteria for meat rejection. On the other hand, meat industry needs rapid analytical methods or tools for quantification of these indicators to determine the type of processing needed for their raw material and to predict remaining shelf life of their products. The need of an objective evaluation of meat spoilage is of great importance. The use of metabolomics as a potential tool for the evaluation of meat spoilage can be of great importance. The microbial association of meat should be monitored in parallel with the estimation of changes occurring in the production and/or assimilation of certain compounds would allow us to evaluate spoilage found or produced during the storage of meat under different temperatures as well as packaging conditions.

Inhibition of Salmonella enteritidis and Staphylococcus aureus in nutrient broth by mint essential oil

Abstract The effect of different concentrations (0–1.2% v/v) of mint (Mentha piperita) essential oil on the growth/survival of Salmonella enteritidis and Staphylococcus aureus was studied in nutrient broth, using the viable count method and conductance measurements. In particular the addition of mint essential oil reduced the total viable counts of St. aureus about 6–7 logs while this of S. enteritidis only ca. 3 logs. The detection time measurements showed also that the inhibitory effect of mint essential oil was affected by the incubation temperature as well as by the concentration of essential oil added in the growth medium. At low concentration of essential oil (

Microbial colonization of naturally black olives during fermentation and associated biochemical activities in the cover brine.

Aims: To establish the site of microbial growth on naturally black fermented table olives, and to monitor the population dynamics of yeasts and selected micro‐organisms together with the changes in organic acid profile and pH in the cover brine during fermentation.

Inhibition of resident microbial flora and pathogen inocula on cold fresh fish fillets in olive oil, oregano, and lemon juice under modified atmosphere or air

The development of a microbial population was studied in Mediterranean gilt-head seabream ( Sparus aurata , tsipoura in Hellenic) dressed with olive oil, lemon juice, and oregano, inoculated with Staphylococcus aureus and Salmonella enteritidis , and stored under a modified atmosphere (MA) of 40% CO2, 30% O2, and 30% N2 or air at 0 ± 1°C. The treatment had bacteriostatic and bactericidal effects on both inoculated pathogens as well as on the autochthonous flora. Brochothrix thermosphacta and pseudomonads dominated the spoilage flora under MA and under air respectively. Shewanella putrefaciens was clearly inhibited.

Antimicrobial activity of the essential oil of mastic gum (Pistacia lentiscus var. chia) on Gram positive and Gram negative bacteria in broth and in Model Food System

The addition of mastic gum in broth culture inoculated with Staphylococcus aureus, Lactobacillus plantarum, Pseudomonas fragi and Salmonella enteritidis inhibited the growth of these organisms as monitored with the Malthus Instrument (in microsiemens). The rate of inhibition was greater on Gram positive bacteria than that observed on Gram negative bacteria. In most cases the size of inoculum and the concentration of mastic gum affected the growth/survival of the organisms. The addition of EDTA in coliform broth increased the inhibitory activity of mastic gum against Salmonella enteritidis, but did not affect significantly the inhibition of this organism in Model Food System (skim milk) at 37°C.

Inhibition of Salmonella enteritidis by oleuropein in broth and in a model food system

The inhibitory effect of commercial ‘pure’ oleuropein was tested against Salmonella enteritidis in a coliform broth and in reconstituted milk (model food system). It was found that the inhibition of this organism in the broth was influenced by the initial inoculum size, the pH of the medium and the concentration of additive. The inhibition was more pronounced in samples with low pH and low inoculum size. No such inhibition was evident in the model food system.

Spoilage processes and proteolysis in chicken as detected by HPLC

Fresh poultry fillets inoculated or not with Pseudomonas fragi stored under aerobic, vacuum and 100% CO2 packaging conditions to study the microbiological as well as the changes occurring in the concentration of glucose, lactate and water-soluble proteins, during the storage at 3 and 10°C. It was found that lactic acid bacteria were the dominant organisms in inoculated or uninoculated poultry fillets stored under these conditions. The low-molecular-weight compounds such as glucose and L-lactate were found to decrease always in these fillets during storage and the profile of water-soluble proteins as detected by HPLC differed among the different samples treated differently.

The yeast Starmerella bacillaris (synonym Candida zemplinina) shows high genetic diversity in winemaking environments

The yeast Candida zemplinina (Starmerella bacillaris) is frequently isolated from grape and wine environments. Its enological use in mixed fermentation with Saccharomyces cerevisiae has been extensively investigated these last few years, and several interesting features including low ethanol production, fructophily, glycerol and other metabolites production, have been described. In addition, molecular tools allowing the characterization of yeast populations have been developed, both at the inter- and intraspecific levels. However, most of these fingerprinting methods are not compatible with population genetics or ecological studies. In this work, we developed 10 microsatellite markers for the C. zemplinina species that were used for the genotyping of 163 strains from nature or various enological regions (28 vineyards/wineries from seven countries). We show that the genetic diversity of C. zemplinina is shaped by geographical localization. Populations isolated from winemaking environments are quite diverse at the genetic level: neither clonal-like behaviour nor specific genetic signature were associated with the different vineyards/wineries. Altogether, these results suggest that C. zemplinina is not under selective pressure in winemaking environments.

Survival of Salmonella enteritidis and Listeria monocytogenes on salad vegetables

The influence of initial head-spaces of air – 4.9% CO2/2.1% O2/93% N2 and 5% CO2/5.2% O2/89.8% N2 – on Salmonella enteritidis and Listeria monocytogenes, and on microbial association with shredded carrots and lettuce was studied at 4 °C. Both these pathogens survived but did not grow in any vegetable regardless of the packaging system used. Total viable count, lactic acid bacteria and pseudomonads were also monitored. Lactic acid bacteria were the predominant organisms in all samples. The pH dropped significantly during the storage of vegetables.

PRESERVATIVES | Traditional Preservatives – Oils and Spices

This article is a revision of the previous edition article by George-John E. Nychas, Chrysoula C. Tassou, volume 3, pp 1717–1722,