Kamuran Ayhan

Biogenic amines produced by Enterobacteriaceae isolated from meat products

Biogenic amines in ground meat and processed meat products are one of the indicators to determine the poor quality raw material. Major histamine forming bacterium was Escherichia coli (strain EC04 with 65.88 mg/100 ml in Brain Heart Infusion medium), followed by the microorganisms Morganella morganii (strain MM4 with 8.40 mg/100 ml and strain MM7 with 8.28 mg/100 ml) and Proteus mirabilis (strain PM02 with 8.76 mg/100 ml), respectively. The highest putrescine production level was found in Citrobacter freundii and Enterobacter spp. strains, followed by Serratia grimesii, Proteus alcalifaciens, E. coli, Escherichia fergusonii, Morganella morganii, Proteus mirabilis, Proteus penneri and Hafnia alvei, respectively. The most important cadaverine producer was E. coli EC03 with a production level of 45.48 mg/100 ml, and of the strains Escherichia vulnaris EV01, Escherichia fergusonii EF06 produced 37.92 mg/100ml and 35.40 mg/100 ml, respectively. On the basis of our results, it can be concluded that the major biogenic amines produced by Enterobacteriaceae are putrescine, cadaverine, tyramine and histamine, both in culture medium and meat products.

The effects of a starter culture on the formation of biogenic amines in Turkish soudjoucks

The effects of starter culture containing Lactobacillus sake, Pediococcus pentosaceus, Staphylococcus carnosus plus Staphylococcus xylosus on the formation of biogenic amines during ripening of Turkish soudjoucks were investigated. Determination of eight different biogenic amines was carried out by reverse-phase high performance liquid chromatography (HPLC) using diode array detection. It was found that aerobic plate counts (APC) decreased in the samples with added starter culture. Lactic acid bacteria counts increased in both the controls and samples with added starter during ripening. Total Enterobacteriaceae (ENT) counts decreased on the 30th day for vacuum packed and starter added samples. Yeast counts decreased only in vacuum packed and starter added samples on the 30th day. No biogenic amines were found in ground meat samples. Putrescine (PU) and tyramine (TYR) were determined in all control samples during the storage at 4°C. Starter addition inhibited formation of PU but not TYR.

Some growth parameters and antimicrobial activity of a bacteriocin-producing strain Pediococcus acidilactici 13

Some growth parameters and bacteriocin production by the strain Pediococcus acidilactici 13, were screened in this study. The inhibitor substance produced by this strain showed strong antimicrobial activity at 204,800 AU/mL (Activity Units/mL) against the gram positive food borne pathogen, Listeria monocytogenes, when the incubation temperature was 37 degrees C and the initial pH of the medium, TGE (Trypton Glucose Yeast Extract), was 6.0. The bacteriocin-producing strain had considerable resistance NaCl, since the strain maintained to growth up to 10% NaCl concentrations at TGE broth and was able to grow in a wide temperature range (25-50 degrees C). The strain was identified as P. acidilactici with API 50 CHL, as well as with 16S rRNA gene sequencing.

Predictive model for the reduction of heat resistance of Listeria monocytogenes in ground beef by the combined effect of sodium chloride and apple polyphenols

We investigated the combined effect of three internal temperatures (57.5, 60, and 62.5°C) and different concentrations (0 to 3.0 wt/wt.%) of sodium chloride (NaCl) and apple polyphenols (APP), individually and in combination, on the heat-resistance of a five-strain cocktail of Listeria monocytogenes in ground beef. A complete factorial design (3×4×4) was used to assess the effects and interactions of heating temperature, NaCl, and APP. All 48 combinations were tested twice, to yield 96 survival curves. Mathematical models were then used to quantitate the combined effect of these parameters on heat resistance of the pathogen. The theoretical analysis shows that compared with heat alone, the addition of NaCl enhanced and that of APP reduced the heat resistance of L. monocytogenes measured as D-values. By contrast, the protective effect of NaCl against thermal inactivation of the pathogen was reduced when both additives were present in combination, as evidenced by reduction of up to ~68% in D-values at 57.5°C; 65% at 60°C; and 25% at 62.5°C. The observed high antimicrobial activity of the combination of APP and low salt levels (e.g., 2.5% APP and 0.5% salt) suggests that commercial and home processors of meat could reduce the salt concentration by adding APP to the ground meat. The influence of the combined effect allows a reduction of the temperature of heat treatments as well as the salt content of the meat. Meat processors can use the predictive model to design processing times and temperatures that can protect against adverse effects of contaminated meat products. Additional benefits include reduced energy use in cooking, and the addition of antioxidative apple polyphenols may provide beneficial health affects to consumers.

Amino acid decarboxylase activities and biogenic amine formation abilities of lactic acid bacteria isolated from shalgam

ABSTRACT 56 lactic acid bacteria were isolated during shalgam fermentation and identified as Lactobacillus spp. (51 isolates), Lactococcus spp. (3 isolates), Streptococcus sp. (one isolate), and Leuconostoc sp. (one isolate). 53 of all isolates decarboxylated both arginine and tyrosine, while others decarboxylated one of arginine or tyrosine. None of the isolates could decarboxylate histidine, ornithine, lysine, phenylalanine, or tryptophan. All isolates produced both agmatine (105.8–867.5 mg L–1) and tyramine (24.5–649.7 mg L–1). Although none of the isolates displayed ornithine decarboxylase activity, putrescine was produced (2.1–33.3 mg L–1) by all isolates, except one Lactobacillus strain. Therefore, lactic acid bacteria seem to be responsible mainly for tyramine and agmatine formation during shalgam fermentation, as well as a small amount of putrescine.