Aktuelle Themen

Aktuelle Themen

Aktuelle Themen

Jens Pfannebecker, Barbara Becker
Nachweis humaner Noroviren in Tiefkühl-­Erdbeeren: Vergleichsstudie 2017 der Arbeits­gruppe Lebensmittelassoziierte Viren (ALV)
Detection of human noroviruses in frozen strawberries: Comparative study of the working group for food associated viruses (Arbeitsgruppe Lebensmittelassoziierte Viren – ALV) 2017

Kontaminiertes Beerenobst gilt als eine der Ursachen Norovirus-bedingter Gastro­enteritiden. Zum qualitativen Nachweis von Norovirus und Hepatitis A-Virus in ­weichem Obst steht seit Ende 2013 ein Protokoll (Teil des Standardverfahrens DIN EN ISO 15216-2) zur Verfügung. In einer laborübergreifenden Vergleichsstudie der Arbeitsgruppe Lebensmittelassoziierte Viren (ALV) wurde der Nachweis humaner Noroviren (GGII) in Tiefkühl (TK)-Erdbeeren untersucht. Ziel der Studie war es zu ­zeigen, inwiefern die Anwendung des Standardverfahrens in der Routineanalytik zu zuverlässigen Ergebnissen führt. Das Testpaket umfasste je 2 x 25 g TK-Erdbeeren mit 5,7 x 107 Noroviren, 2 x 25 g TK-Erdbeeren mit 5,7 x 105 Noroviren sowie 2 x 25 g TK-Erdbeeren ohne Norovirus-Inokulat. Die 18 teilnehmenden Labore setzten ihre etablierten Materialien und Geräte zur Virus-Extraktion und -Detektion nach DIN EN ISO 15216-2 ein. Neun Labore konnten alle Norovirus-kontaminierten Proben qualitativ nachweisen, sowie die nicht-kontaminierten Proben korrekt bestimmen. Acht Labore konnten die mit 5,7 x 105 Noroviren kontaminierten Proben nicht detektieren. Zwei Labore konnten die Proben, die mit einem Titer von 5,7 x 107 Noroviren kontaminiert waren, nicht nachweisen. Insgesamt zeigt das Ergebnis, dass nur sehr hohe Norovirustiter (5,7 x 107 in 25 g Probe) zuverlässig detektiert wurden.

Marc Zulauf, Claudio Zweifel, Roger Stephan
Microbiological quality of raw milk sold directly from farms to consumers in Switzerland
Mikrobiologische Qualität von direkt ab Hof an den Konsumenten verkaufter Rohmilch in der Schweiz

Seventy-three samples of raw cow milk marketed at farm level (12 pre-filled bottles, 61 from vending machines) were investigated for their microbiological quality and the occurrence of bacterial foodborne pathogens. Total viable counts (TVC) were mainly (67.1 %) in the range from 103 to 105 CFU/ml, while Escherichia coli and coagulase-positive staphylococci were each detected in 30.1 % of the samples. TVC results for raw milk from vending machines (34.4 % above 105 CFU/ml) were clearly higher than those from pre-filled bottles, emphasizing the importance of ensuring correct cleaning and disinfection procedures of vending machines. Moreover, regular monitoring of the microbiological quality of raw milk from vending machines should be considered. With regard to foodborne pathogens in raw milk marketed at farm level, 24.7 % of all samples were positive for Staphylococcus aureus harboring staphylococcal ­enterotoxin (SE) genes. Genes for SEA, SEC, and SED were thereby also detected. On the other hand, Campylobacter spp., Listeria monocytogenes, and Shiga toxin-producing Escherichia coli were not detected. But because the occurrence of foodborne pathogens can never be ruled out, raw milk should always be properly heated before consumption.

Christiane Pietschmann, Martina Ludewig, Peggy G. Braun
Microbiological quality and chemical ­composition of goat milk
Mikrobiologische Qualität und chemische Zusammensetzung von Ziegenmilch

The interest in goat milk and goat milk products is increasing worldwide. Therefore, this study considers the chemical composition and microbiological quality of bulk goat milk of a medium-sized German cheese factory over a period of 15 months. Total solids, protein, fat and lactose contents of 24 samples were examined. 27 ­samples were analysed for the total bacterial count as well as the counts of pseudomonads, enterobacteria, lactic acid bacteria, yeasts, moulds and coagulase-positive staphylococci. Furthermore, examinations for Bacillus cereus, Salmonella spp. and ­Listeria monocytogenes were performed. The mean value of protein was 3.0 %, fat 3.6 %, lactose 3.7 % and total solids 10.9 %, whereby data were influenced by ­seasonal factors. The average total bacterial count was 6.1 lg cfu/ml, mainly formed by psychrotrophic, potentially spoilage inducing pseudomonads, but also by lactic acid bacteria, yeasts and moulds. A seasonal influence on the microbiological quality was not detectable. Chemical results show that goat milk with its high levels of ­lactose and protein is a valuable foodstuff. However, strict production hygiene and, with regard to psychrotrophic bacteria, the avoidance of prolonged cooled storage are necessary to guarantee an acceptable microbiological quality and stability.

Meghdad Pirsaheb, Farhad Amirian, Nazir Fattahi, Yadolah Fakhri, Rokhsareh Akbarzadeh, Anvar Asadi
Quantification of the pesticide residues in market pasteurized milk samples using UA-DLLME-SFO method in Kermanshah city, Iran
Quantifizierung von Pestizidrückständen in pasteurisierten Milchproben unter Verwendung der UA-DLLME-SFO-Methode in der Stadt Kermanshah, Iran

The widespread application of pesticides by human can result in the accumulation of pesticides in the food and environment which has a serious effect of human and ­environmental health. This study was conducted to measure residues of 3 widely used pesticides namely diazinon, phosalone and endosulfan in pasteurized milk ­samples which were collected from different brands in Kermanshah city, Iran. Three milk brands with high distribution were collected from local supermarkets during study period. The selected pesticides were detected in milk samples using HPLC-UV with ultrasound-assisted dispersive liquid-liquid microextraction and solidification of floating organic drop (UA-DLLME-SFO) method. The method detection limit (MDL) was estimated on the basis of the results of 6 replicate analyses of a milk sample spiked with each pesticide standard and was at the range of 1–3 µg/L. Under the ­optimum conditions, recoveries in milk samples were in the range of 64–72 %. The calibration graphs were linear in the range of 10–800 µg/L and limit of detections (LODs) were in the range of 1–3 µg/L. The mean concentration in the pasteurized milk samples (n = 27) were: 19.43, 3.51 and 3.16 µg/L and the frequency of detection of pesticides in the milk samples were 44.4 %, 11.1 % and 11.1 % for diazinon, phosalone and endo­sulfan, respectively. Approximately 22.2 % of the samples contained at least one pesticide at detectable level. In conclusion the residues of the detected pesticides were lower than the residue limits set by the FAO/WHO, however, bio­accumulation of these residues is likely to pose health risk to the consumers of milk in Kermanshah city.