applications of radiofrequency treatment for …...applications of radiofrequency treatment for food...

APPLICATIONS OF RADIOFREQUENCY TREATMENT FOR FOOD SAFETY AND PRESERVATION

Georgiana-Aurora ŞTEFÃNOIU*, Elisabeta Elena TÃNASE*, Paul Alexandru POPESCU*, Amalia Carmen MITELUŢ*, Mona Elena POPA*, Radu CRAMARIUC**, Ana Maria BALAUREA- CHIRILOV***, Gabriela

MOHAN****

*University of Agronomic Sciences and Veterinary Medicine of Bucharest, 59 MărăştiBlvd, District 1, 011464, Bucharest, Romania**Competence Center of Electrostatic and Electrotechnologies***S.C. Vel Pitar S.A.****Institute of Food Bioresources Bucharest (INCDBA-IBA)

This paper was realised under the frame of Partnerships in priority areas Programme, PCCA Contract no. 164 / 2014, RAFSIG.

WE: Bioeconomie: producție, procesare și consum sustenabile

26-28 aprilie 2016, Timisoara




TABLE OF CONTENTS

1.INTRODUCTION

2.MECHANISM OF RF HEATING

3.INACTIVATION MECHANISM OF MICROORGANISMS BY

RF

4.APPLICATIONS OF RADIOFREQUENCY TREATMENT IN

FOOD INDUSTRY

5.CONCLUSIONS




OBJECTIVE

This paper presents further the mechanism of action and the

applications of radiofrequency treatment with special emphasis on

the effect on the microorganisms involved in food spoilage.

INTRODUCTION




Research in novel heating of foods, for applications such as cooking,

pasteurisation/sterilisation, defrosting, thawing and drying, often focuses on

areas such as the assessment of processing time, the evaluation of heating

uniformity, the appraisal of the impact on quality attributes of the final product

as well as the prediction of the energy efficiency of these heating processes.

Research on electroheating accounts for a considerable portion of both the

scientific literature and commercial novel heating applications (Marra et al.,

2008).




INTRODUCTION

RF

13.56 MHz (+/- 0.05%)

27.12 MHz (+/- 0.06%)

40.68 MHz (+/- 0.05%)



INTRODUCTION


Radiofrequency

heating

offers alternatives to produce safe and wholesome foods

uses electromagnetic energy of a longer wavelength than

microwaves (MWs), which is of greater industrial

interest.

targets the product, not the air surrounding it.

many applications using RF heating as supplemental heat

have been developed successfully in the food-drying

industry for pasta, crackers, and snacks




MECHANISM OF RF HEATING

A schematic sketch of

the 2-kW, 27.12 MHz

radio frequency unit

(Awuah, 2005)

Radio frequency heating is

accomplished through a combination of

dipole heating and electric resistance

heating resulting from the movement of

dissolved ions present in the food.




For RF heating, penetration depth is generally greater than 1 m, and can be

determined from a relationship that embodies the dielectric constant, the

loss factor, the speed of wave propagation in vacuum and, operating

frequency (Awuah et al., 2005).

Temperature, frequency, concentration and their interactions had different

levels of significance on the dielectric properties of starch solutions

(Piyasena et al., 2003).

MECHANISM OF RF HEATING




ELECTROPORATION

When a cell is exposed to an external electric field, charge is accumulated on the

cell membrane resulting in an artificial increase of the transmembrane potential

(TMP).

If such TMP increase is large enough, and sustained for long enough, cell

membrane permeability to ions and macromolecules will increase very

significantly. The increase in permeability is, presumably, related to the

formation of nano-scale defects or pores in the cell membrane; from which the

term electro- “poration” stems. If the induced permeabilization is moderate, cell

membranes will reseal and the cell will be fully viable in few minutes after field

delivery.

On the other hand, if the permeabilization is made excessive by delivering very

high or prolonged fields, cells will end up dying.

INACTIVATION MECHANISM OF

MICROOGANISMS BY RF




INACTIVATION MECHANISM OF

MICROORGANISMS BY RF




RADIOFREQUENCY

TREATMENT

APPLICATIONS OF RADIOFREQUENCY TREATMENT

IN FOOD INDUSTRY





IN FOOD INDUSTRY

Microbial and pest reduction by dielectric heating has been studied in many

experiments, including meat and meat products; poultry; eggs and egg

products; fish and shellfish; fruit and vegetable products such as canned fruit,

fruit juice, and jam; soy milk; sugar beet molasses; pea protein concentrates;

ready-cooked meals; milk and its products; puddings; cereals; breads; cakes;

pasta; starch; and spices (Mitelut and colab., 2011; Orsat and Raghavan,

2014).

Exposure of liposomes to frequencies of 27 and 100 MHz resulted in

increased lysis of vesicles (Trujillo and Geveke, 2014).




Radio frequency dielectric heating is now widely used in industrial

applications such as drying textile products (spools, rovings, and skeins), final

drying of paper, final dehydration of biscuits at outlets of baking ovens, and

melting honey.

Bottled juices including peach, quince and orange moving through an RF

applicator offered better bacteriological and organoleptic qualities than juices

treated by conventional thermal processing methods (Wang et al., 2003) .

RF heating can be applied to control pathogens in peanut butter products

without affecting quality (Guo et al., 2006).


IN FOOD INDUSTRY




RF heating for 50 s resulted in 2.80 to 4.29 log CFU/g reductions of S.

typhimurium and E. coli O157:H7 in black peppers and RF heating of red

peppers for 40 s reduced pathogens by 3.38 log CFU/g to more than 5 log

CFU/g (below the detection limit) without affecting the color quality change

(Kim et al., 2011).

Tofu was produced experimentally using RF-FH processed soybean milk

and conventionally heated soybean milk. Comparative studies revealed that

the tofu made by RF-FH processing had higher gel strength than the tofu

made by conventional heating (Uemura et al., 2010) .


IN FOOD INDUSTRY




Radio-frequency heating, coupled with appropriate packaging, can improve

the storability of repacked hams by reducing the bacterial load, reducing

moisture loss and maintaining an overall greater product sensory quality

and acceptance (Orsat et al., 2004).

RF treatment was also investigated in naturally infected fruit where the

Monilinia spp. development was completely inhibited in both ‘Summer

Rich’ and ‘Placido’ peaches. No brown rot control was observed in

nectarine fruit artificially inoculated or with natural inoculum (Casals et al.,

2010).


IN FOOD INDUSTRY

The non-thermal process of radio frequency electric fields (RFEF) has been

shown to inactivate bacteria in apple juice at moderately low temperatures,

but has yet to be extended to inactivate bacteria in orange juice. No loss in

ascorbic acid or enzymatic browning was observed due to RFEF processing

(Geveke et al., 2007).

Heating bread to 58°C or higher resulted in 4-log reduction of P. citrinum

spores isolated from moldy bread. The storage life at room temperature

(23°C) was extended by 28 ± 2 days for the treated white bread (Liu et al,.

2010).





IN FOOD INDUSTRY





IN FOOD INDUSTRY

It was determined the number of germs accoring to the standard SR ISO

4833-94.

It has been observed a

decrease of CFU with 2-3

log, which is directly

proportional with the increase

of temperature during the RF

treatment.

Grafic representation of CFU values





IN FOOD INDUSTRY

1 day after the RF treatment

2 days after the RF treatment





IN FOOD INDUSTRY

7 days after the RF treatment




The advantages of RF compared to another volumetric technologies are:

there is no need for electrodes contacting the food (in contrast with ohmic

heating), the RF treatment can be easily applied to both solid and liquid foods;

due to the longer wavelength of RF, its power will penetrate more deeply in the

foods as compared to microwave power;

the construction of large RF heating systems is simpler than their microwave

counterparts, and their application to continuous processes is straightforward;

it is a technology particularly suited to large industrial applications.

CONCLUSIONS




CONCLUSIONS

The reality today is that these novel processing technologies are being

tested for use in the food industry to improve the foods we eat, as they are

capable of inactivating microorganisms, changing cell permeability,

promoting chemical reactions, and even inactivating enzymes.

In fact, RF heating has been successfully applied in the food industry for

drying, baking and thawing, but controversial data are present on the effect

of RF on biological systems




Awuah G.B., Ramaswamy H.S., Economides A., Mallikarjunan K., (2005). Inactivation of Escherichia coli K-12 and

Listeria innocua in milk using radio frequency (RF) heating. Innovative Food Science and Emerging Technologies,

6, 396 – 402.

Casals C., Viñas I., Landl A., Picouet P., Torresa R., Usalla J., (2010). Application of radio frequency heating to control

brown rot on peaches and nectarines. Postharvest Biology and Technology, 58, 218–224.

Geveke D. J., Kozempela M., Scullena O. J., Brunkhorst C., (2002). Radio frequency energy effects on

microorganisms in foods. Innovative Food Science and Emerging Technologies, 3 (2), 133–138.

Liu Y., Tang J., Mao Z., Mah J.H., Jiao S., Wang S., (2010). Quality and mold control of enriched white bread by

combined radio frequency and hot air treatment. Journal of Food Engineering, 104, 492–498.

Marra F., Zhang L., Lyng J.G., 2008. Radio frequency treatment of foods: Review of recent advances. Journal of Food

Engineering 91, 497–508.

Mitelut A., Popa M., Geicu M., Niculita P., Vatuiu D., Vatuiu I., Gilea B., Balint R., Cramariuc R., (2011). Ohmic

treatment for microbial inhibition in meat and meat products. Romanian Biotechnological Letters, 16 (1), 149-152.

Orsat V., Raghavan G.S.V., (2014). Radio-Frequency Processing. Emerging Technologies for Food Processing (Second

Edition), 385–398.

Trujillo F. J., Geveke D. J., (2014). Nonthermal Processing By Radio Frequency Electric Fields. Emerging

Technologies for Food Processing (Second Edition), 259–269.

Uemura K., Takahashi C., Kobayashi I., (2010). Inactivation of Bacillus subtilis spores in soybean milk by radio-

frequency flash heating. Journal of Food Engineering, 100, 622–626.

SELECTIVE REFERENCES




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