István Dalmadi

Effects of pressure- and thermal-pasteurization on volatiles of some berry fruits

In principle, high hydrostatic pressure (HHP) processing offers the possibility to preserve berry products while affecting their volatile components less than heat pasteurization. Therefore, we performed preliminary investigations to compare effects of HHP treatment (600 MPa, 5 min, at ambient temperature) and heat pasteurization (80 °C, 5 min) on volatile composition of raspberry, strawberry and blackcurrant purees measured by ‘electronic nose’ at 25 °C. Changes in the head space volatiles could be monitored by this method. Taking into account the confusion matrix of the discriminant analysis, heat-treatment had a more significant effect on volatile compounds than HHP. So, application of HHP treatment can retain volatiles of berry products.

Effect of high pressure treatment on liquid whole egg

In our tests, we artificially infected liquid whole egg samples with Salmonella enteritidis, Listeria monocytogenes, and Staphylococcus aureus bacteria, and then treated the samples in “Food Lab900” high hydrostatic pressure (HHP) instrument for 3–17 min at 200–400 MPa. Subsequently, the change of the viable cell count of the specific bacteria has been tested. In addition to the samples infected with various bacteria, non-infected samples were also treated in each test and the change in viable cell count, colour and viscosity of the samples upon the effect of the treatment. In summary, it can be concluded that in each test of our investigations, the viable cell count of S. enteritidis critical for egg products is reduced significantly, while the reduction of the total viable cell count was around two magnitudes. Additionally, based on our results, microbial destruction, reduction of enthalpy (denaturation of egg white) caused by the treatment at HPP, and colour change are primarily affected by the pressure level, while the changes in rheological properties are also significantly affected by the duration of high pressure treatment (p<0.05).

Study of Long Term Post-Treatment of Whole Egg Powder at 50-55°C

Study of Long Term Post-Treatment of Whole Egg Powder at 50-55°C In our experiment whole egg powder samples (infected with Salmonella Enteritidis for microbiological tests) were treated at 50.38-54.62°C for 6.41-24.09 h and tested for decrease in Salmonella count or changes in their solubility and colour. Central Composite Rotational Design (CCRD) was used in our tests. In all tests performed within the testing range we achieved a decrease in Salmonella count of at least 5 magnitudes and in cases when the samples were treated at min. 52.5°C for at least 9 h no viable Salmonella could be detected in the whole egg samples at the end of treatments. Our measurements have shown that deterioration of solubility and discolouration was significantly affected only by the temperature change (p<0.05).

The effect of the high hydrostatic pressure technology on livestock products monitored by NIR spectroscopy and chemosensor array

Experiments were performed to study the effects of high hydrostatic pressure (HHP) and gamma irradiation, respectively, from two aspects. The effects of HHP treatments on minced pork meat exposed to 50–800 MPa for 20 min and stored at 4 °C for a period of 1 week were examined. The immediate effects of HHP on egg white samples were compared to that of irradiation. Egg white samples were subjected to irradiation (3 kGy) and HHP treatment (400 MPa, 5 min) and measured immediately after treatments. The recorded electronic nose data and near infrared spectra were evaluated using different methods of multivariate qualitative analyses.