"Out of all the dairy products we analysed, 35% of the samples exceeded the maximum contamination levels established by EU law for enterobacteriaceae, and 31% exceeded the limits set for mesophilic aerobic microorganisms (which grow at an optimum temperature of between 30 and 45ºC)", Isabel Sospedra, a researcher at the Department of Preventive Medicine and Public Health of the UV and one of the authors of the study, tells SINC.
The scientists examined 265 batches of milk and ready-to-use milk derivatives in a range of bars and restaurants in Valencia, and checked whether their microbial quality fell into line with European Union regulations. The results, which have been published recently in the journal Foodborne Pathogens and Disease, show that one-third of the samples had some kind of microorganism contamination and were not fit for human consumption.
"Luckily none of the batches we analysed tested positive for Staphylococcus aureus, Listeria monocytogenes or Salmonella spp., which are pathogenic microorganisms that cause both food poisoning and toxoinfections", the study's authors says.
The researchers found differences according to the source of the sample (hot milk, products at room temperature or homemade dairy products). According to the study, 2% of the samples of hot milk (kept in jugs or stainless steel thermos flasks) tested positive for the bacteria Escherichia coli.
The team detected unsuitable practices, such as reheating milk over and over again, even in a microwave, and then pouring it back into the thermos, which increases the risk of microbial contamination. The study shows that there is a greater contamination risk from milk kept in jugs, meaning this type of container is not suitable for storing milk.
Focus more on cleaning utensils
The experts advise that, when using milk in any way, it is important to clean jugs, thermos flasks and the steamers of coffee machines thoroughly and frequently, using the right kind of hygienic sponges or cloths, which is not always the case. "Kitchen cloths are not suitable for disinfecting because of their microstructure, which means they transfer even greater levels of contamination", the scientists explain.
In terms of milk that is cold or at room temperature, this is usually kept in its original container in restaurants and bars – a plastic bottle or tetrabrick. The study shows that containers with a lid are better, since tetrabricks opened with scissors are more exposed to microbial proliferation, and are especially vulnerable to enterobacteriaceae.
In terms of dairy products prepared in the restaurants themselves (custards, mousses, puddings and crème caramels), custards (natillas) had the highest levels of contamination with microorganisms. This may be due to the fact this was the only foodstuff analysed that is further processed after being heated, say the scientists. Cross contamination could come from the hands of the person preparing the product, particularly when he or she places the biscuit on top of the dish.
In line with previous studies, the researchers also showed that adding cinnamon to dairy products led to reduced microorganism contamination, since this substance helps to eliminate microorganisms such as Escherichia coli, Listeria monocytogenes and bacteria from the Salmonella family.
Isabel Sospedra, Josep V. Rubert, Carla Soler, Jose M. Soriano, Jordi Mañes. "Microbial Contamination of Milk and Dairy Products from Restaurants in Spain". Foodborne Pathogens and Disease 6(10): 1269-1272, diciembre de 2009.
SINC | EurekAlert!
Rutgers-led innovation could spur faster, cheaper, nano-based manufacturing
14.02.2018 | Rutgers University
New study from the University of Halle: How climate change alters plant growth
12.01.2018 | Martin-Luther-Universität Halle-Wittenberg
A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.
In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...
A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.
By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...
Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
23.02.2018 | Physics and Astronomy
23.02.2018 | Health and Medicine
23.02.2018 | Physics and Astronomy