Maciej Oziembłowski, Łukasz Bobak,Tomasz Dróżdż, Igor P. Kurytnik Wrocław University of Environmental and Life Sciences University of Agriculture in Kraków.

Prezentacja na temat: "Maciej Oziembłowski, Łukasz Bobak,Tomasz Dróżdż, Igor P. Kurytnik Wrocław University of Environmental and Life Sciences University of Agriculture in Kraków."— Zapis prezentacji:

1 Maciej Oziembłowski, Łukasz Bobak,Tomasz Dróżdż, Igor P. Kurytnik Wrocław University of Environmental and Life Sciences University of Agriculture in Kraków University of Bielsko-Biala Effect of Pulsed Electric Field strength and number of pulses on fatty acid profile of liquid whole egg

2 Classical methods of food preservation such as thermal, drying, salt, or chemical preservatives are recently being augmented with new technologies: - Packing in modified atmosphere and aseptic processing - Microvawe radiation - Oscillating magnetic fields - High hydrostatic pressure (HHP) - Pulsating electrical fields (PEF) - Ultrasound - Ultraviolet light - Heating with radio-frequency waves - Ohmic heating or resistance heating - Pulsed X-rays - Others

3 Consumer Concerns with New Food Processing Technologies Cardello A.V.: Consumer concerns and expectations about novel food processing technologies: effects on product liking. Appetite, 2003, 40, 217-233.

4 Pulse Electric Fields Preservation with Pulse Electric Fields is a method for processing food by means of brief pulses of a strong electric field between two electrodes. The technique applies very short pulses of high voltage with durations measured in micro- or nano- seconds. In PEF, the electric field destroys the bacteria, which helps with food preservation.

5 Impact of PEF on the Bacterial Cell Membrane The mechanism of microorganism destruction with PEF is not yet fully understood. There are many theories attempting to describe this phenomenon. One postulates that applying electric field to a cell of at least 1 Volt causes permanent or temporary damage to the cell membrane, depending on the strength of the electric field and impulse duration. Damaged cell membrane is more permeable, which causes equalization of the osmotic pressure between the cell and its surrounding environment. This leads to a swelling of the cell and consequently the cell dies. This mechanism is often called “electroporation”.

6 Krytyczne natężenie pola elektrycznego (Ec) Critical electric field strength (Ec) Ec = Vc / f * a gdzie: Vc - napięcie krytyczne f - współczynnik kształtu komórki a - promień komórki where: Vc - critical voltage f - form factor of the cell a - radius of the cell Dla komórek o kształcie zbliżonym do kulistego f = 1,5 For spherical cells f = 1,5 Dla komórek o kształcie cylindrycznym współczynnik f wyznacza się z równania: For cylindrical cells form factor f is given by: f = L / (L - D/3) gdzie: L - długość, D - średnica komórki where: L - length, D - diameter of cell

7 Grupy czynników, od których zależy skuteczność inaktywacji drobnoustrojów z wykorzystaniem PEF Microbial inactivation for a PEF treatment depends on several factors, which are: - Czynniki zależne od parametrów pola elektrycznego - Czynniki zależne od produktu - Czynniki zależne od drobnoustrojów - Factors dependent on the electrical treatment - Factors dependent on the product (suspending medium) - Factors dependent on the microorganism

8 Czynniki zależne od parametrów pola elektrycznego Factors dependent on the electrical treatment - kształt impulsu - natężenie pola elektrycznego - czas oddziaływania PEF (liczba i szerokość impulsów) (liczba i szerokość impulsów) - pulse waveshape - electric field strength - treatment time (number of impulses and the pulse width) (number of impulses and the pulse width)

9 Generowanie impulsów o kształcie „wykładniczym” Generating of exponential-decay pulses Schemat układu elektrycznego do generowania impulsów PEF o kształcie „wykładniczym” Circuit for genarating exponential-decay pulses Kształt bipolarnego impulsu typu „wykładniczego” Exponential decay bipolar pulse

10 Czynniki zależne od produktu Factors dependent on the product (suspending medium) (suspending medium) - temperatura - pH, siła jonowa, przewodność właściwa - skład chemiczny - temperature - pH, ionic strength and conductivity - medium composition

11 Czynniki zależne od drobnoustrojów Factors dependent on the microorganism - wielkość komórki - faza wzrostu - liczba drobnoustrojów w jednostce objętości - obecność zarodników - cell size - growth stage - microbial concentration - spores

12 Parametry oddziaływań PEF a inaktywacja drobnoustrojów Parameters of PEF treatment and inactivation of microorganisms Inaktywacja L. monocytogenes jest tym skuteczniejsza im stosuje się wyższe natężenie pola elektrycznego, dłuższy czas oddziaływań czyli im więcej dostarcza się energii do układu Listeria monocytogenes inactivation increases with the field strength, treatment time and specific energy. Największa inaktywacja (4,77 cykli log.) ma miejsce po zastosowaniu następujących parametrów PEF: A maximum inactivation of 4,77 log cycles was observed after a treatment of: E=28 kV/cm, t=2000  s, W=3490 J/g (Alvarez et al., 2003) Listeria monocytogenes E – natężenie pola eletrycznego t – czas oddziaływań PEF W – gęstość energii w próbie E – electric field strength t – treatment time of PEF W – energy expenditure

13 PEF i trwałość produktu PEF and shelf-life of product Produkt: masa jajowa Product: liquid whole egg Dodatek kw. cytrynowego 0,15% Additive of citric acid 0,15% Dodatek kw. cytrynowego 0,5% Additive of citric acid 0,5% Oddziaływanie PEF PEF treatment Oddziaływanie PEF PEF treatment E=30 kV/cm t=489  s (266 imp.) W=6331 J/ml E=30 kV/cm t=55  s (30 imp.) W=357 J/ml Trwałość / Shelf-life: 20 d (4 o C) Trwałość / Shelf-life: 30 d (4 o C) E – natężenie pola eletrycznego t – czas oddziaływań PEF W – gęstość energii w próbie E – electric field strength t – treatment time of PEF W – energy expenditure

14 Parametry PEF a redukcja mikroflory w różnych płynnych produktach spożywczych Parameters of PEF and inactivation of microorganisms in different liquid food products ProduktE [kV/cm] t  s] [  s] n [-] T [ o C] Mikroflora Microflora D (log red.) Jogurt Yoghurt 23-381002063Lactobacillus bulgaricus Streptococcus thermophilus 2 D Masa jajowa Liquid whole egg 25,8410037Escherichia coli6 D Mleko odtł. Skim milk 451,8-66435Escherichia coli2 D Płynne produkty Fluid foods 12-251-1002545-55Naturalna Natural * *Wydłużona trwałość z 3 do 7 dni / Shelf-life extended from 3 to 7 days

15 Prototypowe urządzenie do generowania PEF Prototype equipment for PEF generating Model ERTEC-SU1

16 Celki / Cells Celkastacjonarna (V=20 ml) Static cell (V=20 ml) Celkaprzepływowa (V=5 ml) Continous cell (V=5 ml)

17 Prototypowe urządzenie do generowania PEF Prototype equipment for PEF generation Celka stacjonarna wypełniona próbą przed oddziaływaniami PEF Static cell with liquid product before PEF treatment

18 Figure 1. Contour plot showing the influence of pulsed electric fields parameters (i.e. electric field strength - E and amount of electric pulses - n) on percentage of saturated fatty acids in liquid whole eggs.

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20 Figure 2. Contour plot showing the influence of pulsed electric fields parameters (i.e. electric field strength - E and amount of electric pulses - n) on percentage of monounsaturated fatty acids in liquid whole eggs.

21 Figure 3. Contour plot showing the influence of pulsed electric fields parameters (i.e. electric field strength - E and amount of electric pulses - n) on percentage of polyunsaturated fatty acids in liquid whole eggs.

22 Figure 4. Contour plot showing the influence of pulsed electric fields parameters (i.e. electric field strength - E and amount of electric pulses - n) on percentage of ω6 polyunsaturated fatty acids in liquid whole eggs.

23 Figure 5. Contour plot showing the influence of pulsed electric fields parameters (i.e. electric field strength - E and amount of electric pulses - n) on percentage of ω3 polyunsaturated fatty acids in liquid whole eggs

24 Figure 6. Contour plot showing the influence of pulsed electric fields parameters (i.e. electric field strength - E and amount of electric pulses - n) on ratio of ω6/ω3 fatty acids in liquid whole eggs.

25 PEF Summary 1.Pulsating Electrical Fields significantly reduce the micro flora in food products. 2. The main difficulty in successful application of this method is the selection of proper PEF parameters to take into account the type of microorganisms being targeted as well as physical and chemical properties of the product. 3. Functional, rheologic and sensory properties of products preserved using the PEF method usually exceed those preserved using traditional methods. 4. The effectivity of PEF on spores has not been confirmed. 5. In practical applications, PEF will likely be used in conjunction with other food preservation methods in accordance with the “gatekeeper theory”.

26 It can be concluded that pulsed electric field treatment had significant influence on the most of investigated parameters. There was not statistically difference for monounsaturated fatty acids amount before and after PEF treatment. Nevertheless all fatty acids parameters were influenced by PEF within variant groups according to Response Surface Methodology results. Our studies proved that investigated parameters of PEF treatment are very important not only in micro flora reduction context, but also for chemical composition changes of final product.

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