INTRODUCTION
Fresh foods have a limited shelf life and spoil very
quickly due to a high water content and easy availability
of nutrients for microorganisms. Mechanical, physical,
chemical, and microbial processes are the main causes
of food spoilage. Therefore, processing of foods is very
important in order to maintain their health benefits and
quality.
Conventional thermal processing is widely used for
microbiological safety and food preservation [1]. This
technique effectively inactivates pathogens and spoilage
microorganisms. However, the application of high
temperatures has a negative effect on the food quality,
namely color, texture, flavor, as well as nutritional
and bioactive compounds [2, 3]. Heat transfer in traditional
thermal processing includes three mechanisms,
namely convection, conduction, and radiation [4]. The
heterogeneous distribution of heat in different parts of
food, which occurs because of internal resistance, adds
to the negative impact on the food quality.
Therefore, alternative technologies should be used to
solve these problems. Ohmic heating, or Joule heating,
is an emerging technique for food processing that
seems to be a suitable alternative to conventional heat
treatment. It generates heat by the passage of alternating
current through food and the resistance of food particles
to electrical current. In fact, food forms part of an
electrical circuit in ohmic heating [5, 6].
Since ohmic heating converts electrical energy to
thermal energy, the temperature inside the food rises
uniformly and rapidly [7, 8]. As a result, there are fewer
sensory changes, less off-flavor, fewer nutritional losses,
and less bioactive degradation.
217
Jafarpour D. et al. Foods and Raw Materials. 2022;10(2):216–226
In addition, this new technology ensures the
microbiological safety of the final product [9]. Other
advantages of ohmic heating include shorter processing
time, higher efficiency, and lower maintenance cost.
Ohmic heating has a variety of uses in food processing,
namely in pasteurization, peeling, blanching, drying,
and concentration [4]. Thus, we aimed to review the
latest studies on the application of ohmic heating in food
processing.
RESULTS AND DISCUSSION
Ohmic heating application in dairy industry.
Ohmic heating technology appeared at the end of the
19th century. Although it was first utilized to pasteurize
milk, ohmic heating was not commercialized due to the
process control problems, high cost of electricity, and
the lack of suitable materials for electrode production.
Today, it is applied in dairy processing to produce
safe, healthy, and high quality dairy products [10].
Particularly, it is used to pasteurize lactose-free milk
since this product has good electrical conductivity.
The material of electrodes used in ohmic heating is an
important issue in dairy production [11]. Less fouling
has been observed in titanium electrodes than in
stainless steel electrodes. This phenomenon can be
explained by the lower chemical reactivity of titanium
compared to stainless steel. Also, milk pasteurized
by ohmic heating with titanium electrodes had a
safe content of chromium and no iron, while milk
pasteurized by ohmic heating with stainless steel
electrodes had more iron and chromium [12]. This is an
important hygienic aspect for designers of food industry
equipment.
The conditions of ohmic heating (variations of
frequencies and voltages) are another factor which
affects the final product. Costa et al. used ohmic
heating with different voltages (2, 4, 5, 7, and 9 V cm−1
at 60 Hz) to process sweet whey and compared the
results with conventional heating [9]. The authors
reported that a higher electric field intensity resulted
in lower luminosity (L*) and lower color variation
(ΔE*). However, a lower electric field intensity led to
better retention of bioactive compounds. This might
be due to the relationship between the duration of heat
exposure, whey protein denaturation, and the production
of bioactive peptides. Besides, the authors recommended
the 4 and 5 V ohmic heating for sweet whey, since these
conditions ensured suitable sensory and rheological
properties with higher bioactive compounds.
In the study of Silva et al., ohmic heating was used
for Dulce de leche treatment for the first time [13].
Dulce de leche is a dairy product which is made by
evaporation and sugar addition. The authors indicated
that the low and intermediate electric field strength
gave the product weaker aroma, more bitter taste, and
a higher sandiness score. At higher intensity, Dulce de
leche was heated for a shorter time, which resulted in a
weaker Maillard reaction and fewer Maillard reaction
products (such as lactones and furans). Lactones and
furans are compounds which affect the aroma and flavor
of sterilized products and may also have a negative
impact on the quality of Dulce de leche. Furthermore,
the ohmic-heated Dulce de leche had a homogeneous
accumulation of whey proteins on a smaller scale. This
prevented the contact of lactose molecules, as well
as inhibited the growth of lactose crystals in size and
sandiness in the final product [14].
Ferreira et al. processed raspberry-flavored whey
beverage under different voltages and frequencies of
ohmic heating [15]. The authors reported that certain
parameters of this process (10, 100, 1000 Hz at 25 V
and 45, 60, 80 V at 60 Hz) had a notable effect on the
particle size, rheological properties, and the color of
the whey beverage. Overall, ohmic-treated beverages
showed higher viscosity than conventionally treated
samples. Among ohmic-heated samples, 10 and 1000 Hz
exhibited the highest viscosity due to the larger
particle size and cell aggregation, while voltage-treated
beverages had lower viscosity. In addition, 10 Hz-treated
samples exhibited more color changes because of the
electrochemical reaction. The authors proposed 10 and
1000 Hz at 25 V as an optimal treatment to achieve the
desired color, physical, and rheological attributes.
In another study, Ferreira et al. revealed that under
extreme conditions of ohmic heating (80 V at 60 Hz and
1000 Hz at 25 V), raspberry-flavored whey beverage
had the lowest antioxidant activity, compared to mild
and intermediate conditions (45 and 60 V at 60 Hz
and 10 and 100 Hz at 25 V) [16]. Furthermore, the
ohmic-heated samples showed higher α-glucosidase
and α-amylase inhibition in comparison with the
conventionally treated beverages. This could be
related to the tendency of bioactive compounds in
whey proteins to bind to the active sites of enzymes.
Reducing the activity of these enzymes can result in
lower hydrolysis of disaccharides and polysaccharides,
as well as glucose uptake, with blood sugar levels maintained
[17].
In a study of whey acerola-flavored beverage,
Cappato et al. stated that ohmic heating decreased the
relaxation period leading to small changes in fatty
acid profiles, as well as preserving the nutritional
properties of processed drink, compared to conventional
heating [18].
Rocha et al. examined the quality parameters of
Minas Frescal cheese produced from milk pasteurized
by using ohmic heating [7]. This technique enhanced
protein hydrolysis, resulting in a lower content of protein
and a higher content of small peptides, compared to the
cheeses made from conventionally treated milk. Cheeses
manufactured from milk subjected to ohmic heating
at the highest voltage showed the lowest proteolytic
activity and the highest protein levels, similarly to the
conventional method. Generally, ohmic heating notably
decreased the hardness, elasticity, and firmness of the
cheeses, yet improving their general acceptability. Low
and intermediate electric field intensity (4 and 8 V/cm)
increased the production of bioactive compounds and
218
Jafarpour D. et al. Foods and Raw Materials. 2022;10(2):216–226
antioxidant activity. Yet, these voltages altered the fatty
acid profile and produced more saturated fatty acids.
Therefore, ohmic heating at 8 V/cm was suggested
for Minas Frescal cheese due to the shorter period of
processing.
It was evidenced that ohmic heating resulted in
lower hydroxymethylfurfural production and higher
overall acceptability of whey dairy drinks, compared to
conventional heating at the same temperatures. This was
due to the shorter time to reach the process temperature,
uniform heat, and lack of hot spots formation [19].
Thus, ohmic heating could be an innovative method for
processing whey dairy drinks with improved sensory
properties [20]. Table 1 summarizes recent applications
of ohmic heating in food processing.
Ohmic heating application in fruit and vegetable
processing. Fresh fruits and vegetables spoil rapidly
after harvesting due to their nature (Aw, nutrients, etc.).
Thus, it is essential to process and convert them into
products which have a longer shelf life [42]. The
traditional way is to concentrate fruit juices by
conventional heating. However, this method impairs the
quality of food due to a low coefficient of heat transfer
and a long processing time [4]. An alternative method
for concentrating fruit juices is ohmic heating [43].
Fruit juices have high electrical conductivity, which
makes them suitable for the ohmic heating technology.
Darvishi et al. reported that the content of total phenols
in ohmic-treated black mulberry juice was 3.0–4.5 times
higher than in the samples treated conventionally [3].
The performance of concentration in ohmic heating was
by about 38–46% greater than in conventional heating.
In addition, the authors stated that as the voltage
increased, the process time decreased, resulting in fewer
changes in total phenols and pH.
Similarly, high voltages (45 and 50 V) were
suggested by Norouzi et al. for concentration of
sour cherry juice [30]. Although ohmic heating
increased the turbidity of sour cherry juice compared
to the conventional method, it was still less than the
initial turbidity. This might be due to an increase in
total phenols with enhanced voltage gradient [44].
The authors also stated that the application of
different voltages did not have a significant effect
on color changes (ΔE) and color parameters such as
“L” (lightness) and “b” (blueness/yellowness).
Minimal alterations in terms of color have also
been detected in ohmic-treated sugarcane juice [25, 45].
Fadavi et al. evaluated the impact of ohmic heating
and conventional heating on tomato juice [4]. They
found that ohmic heating caused little changes in
the properties of tomato juice (acidity, turbidity, and
lycopene) and that these changes would be even less
significant in ohmic heating under vacuum.
Conventional and ohmic dewatering of grapefruit
and orange pulps were investigated by Stojceska
et al. [21]. The authors indicated that the moisture
content decreased markedly during conventional and
ohmic drying, while the amount of vitamin C and pH
did not differ significantly.
Another study found that the application of ohmic
heating for concentration of orange juice under vacuum
significantly reduced the concentration time and led to
the production of fruit juice with higher viscosity, better
color retention, and less decomposition of vitamin C,
compared to processing under atmospheric conditions
[46].
Sabanci and Icier added that the changes in the
temperature of evaporation during the concentration of
orange juice had a notable impact on the time to reach
Figure 1 The effects of ohmic and microwave treatments on vitamin C content in cantaloupe juice. With the permission of the
publisher, Hashemi et al. [22]
Time, s
Vitamin C, mg/kg 0 10 20 30 40 50 60 70 80 90 100 110
850
950
10500
11500
12500
13500
1450
15500
16500
750
219
Jafarpour D. et al. Foods and Raw Materials. 2022;10(2):216–226
Table 1 Ohmic heating applications in food processing
Product Process
purpose
Ohmic heating
conditions
Main findings References
Whey dairy
beverages
Thermal
processing
6, 9, 12, and
15 V/cm – 500,
1000, 1500, and
2000 Hz
Samples processed by increased voltage gradient and frequencies
presented higher overall liking
[20]
Dulce de leche Thermal
processing
0, 2, 4, 6, 8, and
10 V/cm –
60 Hz
Low and intermediate electric field strength resulted in more
bitter taste, weaker aroma, and higher sandiness; higher intensity
reduced the heating time and weakened the Maillard reaction
[13]
Whey dairy
beverage
Thermal
processing
6 V/cm – 60 Hz Ohmic heating led to less hydroxymethylfurfural production and
increased overall liking, compared to conventional heating at the
same temperatures
[19]
Sweet whey Thermal
processing
2, 4, 5, 7, and 9
V/cm – 60 Hz
Higher electric field intensity resulted in lower luminosity and
lower color variation; lower intensity led to better retention of
bioactive compounds
[9]
Wheyraspberry
flavored
beverage
Thermal
processing
10, 100, and
1000 Hz – 25 V
and 45, 60, and
80 V – 60Hz
Extreme ohmic heating conditions led to the lowest antioxidant
activity, compared to mild and intermediate conditions;
ohmic heating-treated samples showed higher α-glucosidase
and α-amylase inhibition, as well as higher viscosity, than
the conventionally treated beverages; 10 Hz-treated samples
exhibited more color changes
[15]
Whey acerolaflavored
drink
Pasteurization 45, 60, and
80 V –
60 Hz and 10,
100, and
1000 Hz – 25 V
Ohmic heating led to small changes in fatty acids profiles or
preservation of nutritional properties, compared to conventional
heating; electric field effects caused small modifications of
nutritional aspects, while frequency had a stronger influence on
the quality of the product; high frequenЦcies (1000 and 100 Hz)
resulted in better bioactive compounds and antioxidant capacity
[18]
Lactose-free
milk
Pasteurization 8.25 V/cm –
50 Hz
This product can be subjected to ohmic heating due to its
good electrical conductivity; less fouling observed in titanium
electrodes than in stainless steel electrodes
[11]
Minas Frescal
cheese (MFC)
Pasteurization
of milk
intended
for MFC
manufacture
4, 8, and
12 V/cm
Cheeses manufactured from milk subjected to ohmic heating
at the highest voltage showed the lowest proteolytic activity
and highest protein levels, similar to conventional heating;
ohmic heating decreased hardness, elasticity, and firmness, but
improved general acceptance of cheeses; production of bioactive
compounds and antioxidant activity increased at low and
intermediate electric field intensity (4 and 8 V/cm)
[7]
Grapefruit and
orange pulps
Drying 30 V/cm Vitamin C and pH did not differ significantly between ohmic
heating and thermal dehydration
[21]
Cantaloupe
juice
Pasteurization 100 and 200 V Higher voltage resulted in a reduced number of pathogens and
lower contents of vitamin C, carotene, and phenolic compounds
[22]
Pulque Pasteurization 60, 80, 100, and
120 V – 60 Hz
Ohmic heating improved the physicochemical and sensory properties,
compared to conventional heating
[23]
Tomato juice Concentration 10.5, 13.2, and
15.8 V/cm –
50 Hz
Ohmic heating caused slight changes in the properties of tomato
juice (acidity, turbidity, and lycopene) which were even less pronounced
when using vacuum
[4]
Orange juice Concentration 13 V/cm –
50 Hz
Ohmic heating treatment under vacuum resulted in better retention
of vitamin C and fewer color changes, compared to treatment
under atmospheric conditions
[24]
Sugarcane
juice
Pasteurization 60 Hz Ohmic heating and ultrasound did not affect phenolic compounds,
whose content was similar to fresh juice; only slight color
changes were caused by ohmic heating
[25]
Pineapple
cubes
Thermal
processing
Electrical power
was calculated
based on the
electrical
conductivity of
pineapple cubes
Lightness and antioxidant properties of the pineapples did not
differ significantly between ohmic heating and conventional
heating; ohmic heating increased the hardness of the pineapples
compared to the conventional method
[26]
Blanching 25, 30, and
35 V/cm
The highest textural degradation was observed at all electric field
strengths at 90 s process time; higher strength (35 V/cm) resulted
in a higher drying rate
[27]
220
Jafarpour D. et al. Foods and Raw Materials. 2022;10(2):216–226
Continuation of Table 1
Product Process
purpose
Ohmic heating
conditions
Main findings References
Pear Assisting in
lye peeling
426, 479, 532,
585, and
638 V/m
Ohmic heating enhanced the product yield, efficacy of peeling, as
well as the quality of the final product; peel quality was best at
much lower concentrations of lye (2% NaOH at 532 V/m and 3%
NaOH at 426 and 479 V/m)
[28]
Mulberry juice Concentration 15, 20, 25, and
30 V/cm –
50 Hz
Ohmic heating provided greater concentration than the conventional
method (about 38–46%); higher voltage reduced the process time,
resulting in fewer changes in total phenols and pH
[3]
Pekmez Evaporation 17.5, 20.0,
22.5, and
25.0 V/cm
Energy consumption was higher in conventional heating than ohmic
heating for all voltage gradients; energy efficiency increased with
higher voltage gradient
[29]
Sour cherry
juice
Concentration 8.3, 9.7, 122.0,
11.1, 12.5, and
13.9 V/cm –
50 Hz
Although ohmic heating increased the turbidity of sour cherry juice
compared to the conventional method, it was still lower than the
initial turbidity; different voltages did not have a significant effect
on color parameters such as “L” (lightness) and “b” (blueness/
yellowness)
[30]
Coconut water Pasteurization 10 and
20 V/cm –
50 Hz
Ohmic heating could completely inactivate peroxidase but not
polyphenol oxidase; no pink color found in ohmic heating-treated
samples during cold storage, unlike conventionally pasteurized
samples
[31]
Short grain
rice
Cooking 60 Hz Ohmic heating adversely affected color parameters (color intensity
and lightness), resulting in softer texture compared to the hotplate
cooking system
[32]
Noodle Cooking 10.0, 12.5,
15.0, and
17.5 V/cm –
60 Hz
Temperature come-up time decreased significantly with an increase
in electric field; 15 V/cm electric field strength with the holding
time of 90 s was suggested as the best treatment in terms of
desirable texture and energy efficiency
[33]
Whole and
decorticated
pearl millet
grain
Cooking 60 Hz Grain pericarp considered the principal factor influencing the
cooking process rather than the method of heating; no significant
differences observed between conventional open-pan and ohmic
heating methods in terms of texture and color
[34]
Pork Cooking 21 ± 1 V/cm –
60 Hz
Shorter cooking time; such important factors as cooking loss,
color, and water holding capacity were not significantly affected,
compared to pan cooking
[35]
Vacuum
packaged
sausage
Postpasteurization
230 V – 50 Hz Ohmic heating only slightly changed the texture and color of
vacuum packaged sausages, while having no notable impact on pH,
water holding capacity, lipid oxidation, or cooking loss
[36]
Beef Cooking 50 V –
20 kHz
Electrical conductivity is affected by the amount of fat in the
muscle tissue; series electric current reduces electrical conductivity,
compared to parallel current
[37]
Whole egg Pasteurization 20 kHz Ohmic heating improved the hardness and foaming capacity
compared to conventional pasteurization and caused slight changes
in color; although ohmic heating increased viscosity, its detrimental
impact could be reduced by adjusting the process conditions; low
temperature pasteurization was proposed due to its low impact on
protein denaturation
[38]
Egg white Pasteurization 20 kHz Fewer proteins denatured during thermally-induced gelation of egg
white protein under ohmic heating
[39]
Starch Gelation 7 to 27 V/cm –
60 Hz
The stability of starch gels strongly depended on the type of starch
and was not affected by the type of heat treatment
[40]
Surimicanned
corn
mixed gels
Thermal
processing
250 V –
10 kHz
Ohmic heating effectively reduced moisture loss in corn and preserved
the texture of corn and surimi gel better than the water-bath
heating method
[41]
221
Jafarpour D. et al. Foods and Raw Materials. 2022;10(2):216–226
the target values of total soluble solids, performance,
and electrical conductivity [24]. They explained that
various values of absolute pressure and, consequently,
boiling temperatures applied in ohmic heating affected
energy efficiency, according to the second law of
thermodynamics. Higher boiling temperature decreased
the process time and had a positive effect on energy
efficiency.
In some studies, ohmic heating has been used to
pasteurize fruit juices. Particularly, Hashemi et al.
compared the efficiency of ohmic and microwave
processes for treatment of cantaloupe juice [22].
They indicated that higher voltage of ohmic
heating and microwave power markedly decreased
phenolic compounds, vitamin C, and the number
of pathogens. In fact, at high voltages compounds
are produced that catalyze the decomposition
pathways of ascorbic acid in the presence of oxygen
due to thermal effects, electrode reactions, and
the electrolysis of the solution. Hashemi et al.
observed the highest degradation of vitamin C in the
ohmic treatment at 200 V and the lowest in the microwave
treatment at 400 W (Fig. 1).
In another study [47], they found electric current and
temperature to be the major variables which affected the
pasteurization of sour orange juice. The authors showed
that heat transfer in orange juice was accelerated by the
application of a higher electric field (Fig. 2)
Alcántara-Zavala et al. reported that ohmic heating
improved the physicochemical and sensory properties
of fermented beverage obtained from the agave plant
(known as pulque) [23]. Pulque is an alcoholic beverage
with acidic taste. Ohmic heating improved its flavor
(alcoholic perception and acidity) and made it more
palatable for consumption, compared to conventional
heating. Due to its mineral content, pulque showed good
electrical conductivity. Its pasteurization with 120 V at
65°C for 5 min was reported as the best treatment.
Rinaldi et al. evaluated the physical and chemical
impacts of ohmic heating and conventional heating
on cubes of pineapple in syrup [26]. They observed
insignificant differences in the lightness (L*) and
antioxidant properties between the two methods, while
the hardness of the ohmic-treated pineapples was higher
than that of those treated conventionally. In addition,
Kumar et al. observed the highest textural degradation
of pineapple cubes at all electric field strengths at 90 s
process time [27]. They also found that higher electric
field strength resulted in a higher drying rate.
Ohmic heating can be used as an alternative to
conventional blanching prior to drying and storage
of vegetables and fruits. Kanjanapongkul and Baibua
applied ohmic heating to pasteurize coconut water and
found that it could completely inactivate peroxidase,
but not polyphenol oxidase [31]. In addition, no pink
discoloration was reported in the ohmic-heated samples,
while the conventionally pasteurized samples featured a
pink color during cold storage.
Another application of ohmic heating is in the
peeling process. Removing the skin of fruits and
vegetables is one of the most common treatments in
food processing. The conventional peeling methods (lye,
steam, and mechanical method) have several drawbacks,
including high peeling losses, high consumption of
energy, and environmental issues. Therefore, there is a
growing demand for alternative methods [48]. Gupta and
Sastry employed ohmic heating to remove the skin of
pear [28]. Furthermore, a combination of ohmic heating
and CO2 laser drilling has been used to remove tomato
skins [49]. These studies have shown that ohmic heating
enhances the product yield, efficacy of peeling, as
well as the quality of the final product. However, some
parameters should be considered to optimize the peeling
process, such as temperature, composition of peeling
medium, and electric field strength [28, 50].
Ohmic heating application in grain processing.
The boiling of food products, such as rice and noodles,
is a time-consuming process. Today, as the people’s
lifestyles have altered, there is a growing demand for
rapid cooking methods and alternatives to traditional
methods. Gavahian et al. investigated the impact of
ohmic heating and traditional cooking on the textural
and physical attributes of short grain rice [32]. They
reported that although ohmic heating adversely affected
the color parameters (color intensity and lightness),
it resulted in softer texture in comparison with the
hotplate cooking system. In this regard, the corrosion
of electrodes and electrochemical reactions have been
expressed as factors affecting the color of ohmic-heated
foods [32].
Ohmic heating has also been found to markedly
reduce the cooking time, fouling, and consumption
of energy, compared to the traditional method [51].
Similarly, Jo and Park utilized different electric fields
(10.0, 12.5, 15.0, and 17.5 V/cm) for cooking instant
noodles [33]. They observed that heat transfer between
noodles and soup was expedited at higher electric fields.
Therefore, the authors suggested 15 V/cm with the
Figure 2 Temperature profile of sour orange juice during
ohmic heating for 120 s and three different voltages
(100, 150, and 200 V). With the permission of the publisher,
Hashemi et al. [47]
Time, s
Temperature, °C
0 20 40 60 80 100 120
25
35
45
55
75
85
95
105
65
100 V 150 V 200 V
222
Jafarpour D. et al. Foods and Raw Materials. 2022;10(2):216–226
reduces the electrical conductivity during ohmic heating,
as well as uniform heating. The authors also found that
series electric current reduced electrical conductivity,
compared to parallel current. Reduction of shrinkage
and drip loss were observed in both types of meat
during ohmic cooking at 50 V and 20 kHz [37].
Additionally, ohmic heating can be applied to cook
pork since it shortens the cooking time without having
a significant impact on the water holding capacity,
color, and cooking loss, compared to the traditional pan
cooking [35]. Similarly, ohmic heating has no significant
effect on the properties of scallops (texture, shrinkage,
and water release) and reduces the denaturation of actin
by shortening the heating time [53].
Inmanee et al. investigated the impacts of ohmic
heating on Listeria monocytogenes contamination and
the quality of sausages during post-pasteurization [36].
They showed that the ohmic process effectively
inactivated L. monocytogenes (≥ 5-log reduction). The
authors compared the electrical conductivity of sausage,
salt solution, and collagen casing. They found that the
collagen casing had a higher electrical conductivity than
the sausage and attributed it to the presence of fat, which
made up to 20% of the sausage. The salt solution acted
as a conductor, with lower conductivity than the sausage
and casing.
The study also showed that the ohmic process only
slightly changed the texture and color of the vacuumpackaged
sausages. At the same time, it had no notable
impact on pH, water holding capacity, lipid oxidation,
and cooking loss. However, these slight changes in
texture and color were not detectable by sensory
evaluators. Therefore, ohmic heating has the potential to
be applied in the meat and meat products industry with
the least impact on their quality.
Other food products. Several studies have
investigated the technological attributes of eggs under
ohmic heating. Since fresh-laid eggs can be a cause of
salmonella infection, manufacturers prefer pasteurized
egg for both its safety and ease of handling [54].
holding time of 90 s as the best treatment in terms of
desirable texture and energy efficiency.
Dias-Martins et al. compared the impact of
conventional open-pan and ohmic heating on whole
and decorticated pearl millet grains [34]. They found
the grain pericarp to be the principal factor influencing
the cooking process, rather than the method of heating.
Regarding pearl millet grain, no significant differences
were observed between the two cooking methods in
terms of texture and color. However, the ohmic-heated
decorticated grains exhibited greater lightness and
harder texture, compared to the conventionally cooked
grains.
Waziiroh et al. examined the basic aspects of using
ohmic heating for baking gluten-free bread [52]. They
stated that the changes in the physical properties of
gluten-free bread during heating depended on the
ingredients and their interaction in the dough. They
believed that two major factors affected the porosity
and viscosity of dough during baking by ohmic
heating, namely dough ingredients and their properties
(e.g., non-ionic and ionic compounds, particle size,
surface hydrophobicity, emulsification ability, etc.) and
dough structural properties (foam formation, protein
denaturation, and starch gelatinization).
Ohmic heating application in meat industry.
It has been investigated that ohmic heating can be
used for processing meat and meat products. Several
factors affect the electrical conductivity and therefore
the efficiency of the ohmic process, including meat
structure (type of meat, amount of fat and moisture),
lean-to-fat ratio, and electric current direction [35].
Llave et al. studied the impact of meat type (Japanese
beef and Australian beef) and the direction of
electric current (series and parallel) on the electrical
conductivity during ohmic cooking [37]. They reported
that Japanese meat had lower electrical conductivity
than Australian meat due to its higher fat content.
Having low electrical conductivity, fat prevents the
passage of current by covering lean particles, which
Figure 3 Various applications of ohmic heating in food processing
223
Jafarpour D. et al. Foods and Raw Materials. 2022;10(2):216–226
Eggs are a rich source of protein and due
to their sensitivity to high temperature, great
care must be taken during egg pasteurization to
prevent proteins denaturation and coagulation.
Alamprese et al. reported that ohmic heating
improved the hardness and foaming capacity of the
whole egg, compared to conventional pasteurization,
and caused slight changes in its color [38].
The authors stated that although ohmic heating
increased viscosity, its detrimental impact could be
reduced by adjusting the process conditions. In general,
they proved that ohmic treatment could be used as a
desirable method for whole egg treatment and proposed
low temperature pasteurization due to its low impact on
protein denaturation.
Similarly, Llave et al. examined color alterations
of egg yolk under ohmic treatment and evaluated the
correlation between color changes and the degree of
protein denaturation [54]. They found that increasing
temperatures caused the egg yolk color to gradually turn
from plain orange to vivid yellow, while the egg white
gradually changed from transparent to cloudy.
In addition, the egg color changes were correlated
with the non-denaturation ratio of the second peak
temperature. In this regard, Joeres et al. indicated that
egg white protein did not fully denature during ohmic
heating [39]. They believed that this could be related to
the oscillatory electric field which partially interfered
with the complete denaturation and development of
intermolecular beta-sheet structures during thermal
gelation of ovalbumin. Also, according to the results
of scanning electron microscopy, the ohmic-heated
gels had a more open and porous network structure,
compared to conventional treatment which exhibited
denser gels.
In another study, da Silva et al. investigated the
impact of ohmic heating on the rheological attributes
and stability of gels produced from starch [40].
Particularly, they examined the effect of starch source
(cassava and maize) and type of treatment. They found
that the stability of starch gels strongly depended on the
type of starch and was not affected by the type of heat
treatment. The researchers revealed that ohmic heating
had several advantages over conventional heating. In
particular, it reduced energy and water consumption, as
well as wastewater production, and did not affect the
properties of the final product.
In a study by Jung et al., ohmic heating was used
to process surimi-corn mixture [41]. The authors
reported that this technique effectively reduced the
amount of moisture loss in corn and preserved the
texture of corn and surimi gel better than the water-bath
heating method.
Limitations and advantages. Ohmic heating has
revealed its potential for processing various foods in
industrial applications. Apart from heat treatment, it
can also be used as an assisted treatment for other
processes like peeling, concentration, and drying
(Fig. 3). Although recent studies have indicated that
ohmic heating can improve the physical and chemical
properties of foods, compared to conventional heating,
there are some limitations regarding its application.
Operator safety, high capital cost, and corrosion of
electrodes are major concerns of food manufacturers to
commercialize this novel technology.
Studies have shown that ohmic-treated foods have
better texture, better aroma, lower color variation,
higher bioactive compounds, and better sensory
properties, compared to conventionally treated foods [3,
7, 9, 13, 16, 18, 20, 23, 26, 30, 33, 36, 49]. However, for
some foods, there are no significant differences between
the two methods in terms of quality [21, 26, 40].
In contrast, some studies have revealed that ohmic
heating can adversely affect some physical properties
of food such as color [32]. Electrode corrosion and some
electrochemical reactions are among its limitations that
can affect the food quality. Besides, ohmic heating is
not a suitable method for processing foods with a high
fat content since fat has low electrical conductivity.
Therefore, the ohmic process conditions must be
optimized according to the food properties in order to
achieve the best result.
Other advantages of ohmic heating are a shorter time
to reach the process temperature, lower consumption
of energy, uniform distribution of heat, and a shorter
total heating period [7, 10, 29, 40, 43]. Although this
novel technology has some limitations and drawbacks,
its advantages make it a suitable alternative to the
traditional heating process.
CONCLUSION
Ohmic heating follows the Joule’s law to heat foods
quickly and evenly, effectively and volumetrically. This
method is markedly influenced by different properties of
foods, including the amount of fat, type of food material,
particle size, pH, viscosity, the content of charged
ions, etc. In addition, variations of frequencies and
voltages also play an important role in the performance
of ohmic heating during food processing. Our review
concludes that the processing of food materials by ohmic
heating can be carried out in a shorter time, compared
to conventional heating. In addition, the quality of
foods can be effectively affected by ohmic treatment
through both thermal and non-thermal impacts. While
its thermal impacts on the food quality have been
extensively studied, there is limited information on the
non-thermal impacts of this technology on various food
properties, such as texture, color, taste, etc. Therefore,
a more detailed study is needed to fully realize the
thermal and non-thermal impacts of ohmic heating for
different foods and under various operating conditions.
The ohmic process has many benefits for food industry,
including process energy and time savings. Furthermore,
this technology provides more reliable process control,
compared to the traditional technique. These benefits
suggest that ohmic heating can be a superior alternative
224
Jafarpour D. et al. Foods and Raw Materials. 2022;10(2):216–226
CONTRIBUTION
The authors were equally involved in writing the
manuscript and are equally responsible for plagiarism.
CONFLICT OF INTEREST
The authors have declared no conflict of interest.

1. Gavahian M, Chu Y-H, Farahnaky A. Effects of ohmic and microwave cooking on textural softening and physical properties of rice. Journal of Food Engineering. 2019;243:114-124. https://doi.org/10.1016/j.jfoodeng.2018.09.010

2. Hashemi SMB, Roohi R. Ohmic heating of blended citrus juice: Numerical modeling of process and bacterial inactivation kinetics. Innovative Food Science and Emerging Technologies. 2019;52:313-324. https://doi.org/10.1016/j.ifset.2019.01.012

3. Darvishi H, Salami P, Fadavi A, Saba MK. Processing kinetics, quality and thermodynamic evaluation of mulberry juice concentration process using Ohmic heating. Food and Bioproducts Processing. 2020;123:102-110. https://doi.org/10.1016/j.fbp.2020.06.003

4. Fadavi A, Yousefi S, Darvishi H, Mirsaeedghazi H. Comparative study of ohmic vacuum, ohmic, and conventional-vacuum heating methods on the quality of tomato concentrate. Innovative Food Science and Emerging Technologies. 2018;47:225-230. https://doi.org/10.1016/j.ifset.2018.03.004

5. Müller WA, Ferreira Marczak LD, Sarkis JR. Microbial inactivation by ohmic heating: Literature review and influence of different process variables. Trends in Food Science and Technology. 2020;99:650-659. https://doi.org/10.1016/j.tifs.2020.03.021

6. Wu S, Yang N, Jin Y, Li D, Xu Y, Xu X, et al. Development of an innovative induction heating technique for the treatment of liquid food: Principle, experimental validation and application. Journal of Food Engineering. 2020;271. https://doi.org/10.1016/j.jfoodeng.2019.109780

7. Rocha RS, Silva R, Guimarães JT, Balthazar CF, Pimentel TC, Neto RPC, et al. Possibilities for using ohmic heating in Minas Frescal cheese production. Food Research International. 2020;131. https://doi.org/10.1016/j.foodres.2020.109027

8. Leong SY, Oey I. Application of novel thermal technology in foods processing. Foods. 2022;11(1). https://doi.org/10.3390/foods11010125

9. Costa NR, Cappato LP, Pereira MVS, Pires RPS, Moraes J, Esmerino EA, et al. Ohmic Heating: A potential technology for sweet whey processing. Food Research International. 2018;106:771-779. https://doi.org/10.1016/j.foodres.2018.01.046

10. Pereira RN, Teixeira JA, Vicente AA, Cappato LP, da Silva Ferreira MV, da Silva Rocha R, et al. Ohmic heating for the dairy industry: a potential technology to develop probiotic dairy foods in association with modifications of whey protein structure. Current Opinion in Food Science. 2018;22:95-101. https://doi.org/10.1016/j.cofs.2018.01.014

11. Suebsiri N, Kokilakanistha P, Laojaruwat T, Tumpanuvat T, Jittanit W. The pasteurization of milk applying ohmic heating in comparison with conventional method and the quality attributes of lactose-free milk. Phranakhon Rajabhat Research Journal: Science and Technology. 2019;14(1):25-35.

12. Tian X, Yu Q, Wu W, Dai R. Inactivation of microorganisms in foods by ohmic heating: A review. Journal of Food Protection. 2018;81(7):1093-1107. https://doi.org/10.4315/0362-028X.JFP-17-343

13. Silva R, Rocha RS, Guimarães JT, Balthazar CF, Scudino H, Ramos GLPA, et al. Dulce de leche submitted to ohmic heating treatment: Consumer sensory profile using preferred attribute elicitation (PAE) and temporal check-all-that-apply (TCATA). Food Research International. 2020;134. https://doi.org/10.1016/j.foodres.2020.109217

14. Rodrigues RM, Fasolin LH, Avelar Z, Petersen SB, Vicente AA, Pereira RN. Effects of moderate electric fields on cold-set gelation of whey proteins - From molecular interactions to functional properties. Food Hydrocolloids. 2020;101. https://doi.org/10.1016/j.foodhyd.2019.105505

15. Ferreira MVS, Cappato LP, Silva R, Rocha RS, Neto RPC, Tavares MIB, et al. Processing raspberry-flavored whey drink using ohmic heating: Physical, thermal and microstructural considerations. Food Research International. 2019;123:20-26. https://doi.org/10.1016/j.foodres.2019.04.045

16. Ferreira MVS, Cappato LP, Silva R, Rocha RS, Guimarães JT, Balthazar CF, et al. Ohmic heating for processing of whey-raspberry flavored beverage. Food Chemistry. 2019;297. https://doi.org/10.1016/j.foodchem.2019.125018

17. Martinez-Gonzalez AI, Díaz-Sánchez ÁG, de la Rosa LA, Bustos-Jaimes I, Alvarez-Parrilla E. Inhibition of α-amylase by flavonoids: Structure activity relationship (SAR). Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy. 2019;206:437-447. https://doi.org/10.1016/j.saa.2018.08.057

18. Cappato LP, Ferreira MVS, Moraes J, Pires RPS, Rocha RS, Silva R, et al. Whey acerola-flavoured drink submitted Ohmic Heating: Bioactive compounds, antioxidant capacity, thermal behavior, water mobility, fatty acid profile and volatile compounds. Food Chemistry. 2018;263:81-88. https://doi.org/10.1016/j.foodchem.2018.04.115

19. Pereira MO, Guimarães GT, Ramos GLPA, do Prado-Silvac L, Nascimento JS, Sant’Ana AS, et al. Inactivation kinetics of Listeria monocytogenes in whey dairy beverage processed with ohmic heating. LWT. 2020;127. https://doi.org/10.1016/j.lwt.2020.109420

20. Coimbra LO, Vidal VAS, Silva R, Rocha RS, Guimarães JT, Balthazar CF, et al. Are ohmic heating-treated whey dairy beverages an innovation? Insights of the Q methodology. LWT. 2020;134. https://doi.org/10.1016/j.lwt.2020.110052

21. Stojceska V, Atuonwu J, Tassou SA. Ohmic and conventional drying of citrus products: energy efficiency, greenhouse gas emissions and nutritional properties. Energy Procedia. 2019;161:165-173. https://doi.org/10.1016/j.egypro.2019.02.076

22. Hashemi SMB, Gholamhosseinpour A, Niakousari M. Application of microwave and ohmic heating for pasteurization of cantaloupe juice: microbial inactivation and chemical properties. Journal of the Science of Food and Agriculture. 2019;99(9):4276-4286. https://doi.org/10.1002/jsfa.9660

23. Alcántara-Zavala AE, Figueroa-Cárdenas JD, Morales-Sánchez E, Aldrete-Tapia JA, Arvizu-Medrano SM, Martínez-Flores HE. Application of ohmic heating to extend shelf life and retain the physicochemical, microbiological, and sensory properties of pulque. Food and Bioproducts Processing. 2019;118:139-148. https://doi.org/10.1016/j.fbp.2019.09.007

24. Sabanci S, Icier F, Evaluation of an ohmic assisted vacuum evaporation process for orange juice pulp. Food and Bioproducts Processing. 2022;131:156-163. https://doi.org/10.1016/j.fbp.2021.09.009

25. Rodrigues NP, Brochier B, de Medeiros JK, Marczak LDF, Mercali GD. Phenolic profile of sugarcane juice: Effects of harvest season and processing by ohmic heating and ultrasound. Food Chemistry. 2021;347. https://doi.org/10.1016/j.foodchem.2021.129058

26. Rinaldi M, Littardi P, Ganino T, Aldini A, Rodolf M, Barbanti D, et al. Comparison of physical, microstructural, antioxidant and enzymatic properties of pineapple cubes treated with conventional heating, ohmic heating and high-pressure processing. LWT. 2020;134. https://doi.org/10.1016/j.lwt.2020.110207

27. Kumar A, Begum A, Hoque M, Hussain S, Srivastava B. Textural degradation, drying and rehydration behaviour of ohmically treated pineapple cubes. LWT. 2021;142. https://doi.org/10.1016/j.lwt.2021.110988

28. Gupta S, Sastry SK. Ohmic heating assisted lye peeling of pears. Journal of Food Science. 2018;83(5):1292-1298. https://doi.org/10.1111/1750-3841.14116

29. Tunç MT, Akdoğan A, Baltacı C, Kaya Z, Odabaş HI. Production of grape pekmez by Ohmic heating-assisted vacuum evaporation. Food Science and Technology International. 2022;28(1):72-84. https://doi.org/10.1177/1082013221991616

30. Norouzi S, Fadavi A, Darvishi H. The ohmic and conventional heating methods in concentration of sour cherry juice: Quality and engineering factors. Journal of Food Engineering. 2021;291. https://doi.org/10.1016/j.jfoodeng.2020.110242

31. Kanjanapongkul K, Baibua V. Effects of ohmic pasteurization of coconut water on polyphenol oxidase and peroxidase inactivation and pink discoloration prevention. Journal of Food Engineering. 2021;292. https://doi.org/10.1016/j.jfoodeng.2020.110268

32. Gavahian M, Tiwari BK, Chu Y-H, Ting Y-W, Farahnaky A. Food texture as affected by ohmic heating: Mechanisms involved, recent findings, benefits, and limitations. Trends in Food Science and Technology. 2019;86:328-339. https://doi.org/10.1016/j.tifs.2019.02.022

33. Jo YJ, Park SH. Evaluation of energy efficacy and texture of ohmically cooked noodles. Journal of Food Engineering. 2019;248:71-79. https://doi.org/10.1016/j.jfoodeng.2019.01.002

34. Dias-Martins AM, Cappato LP, da Costa Mattos M, Rodrigues FN, Pacheco S, Carvalho CWP. Impacts of ohmic heating on decorticated and whole pearl millet grains compared to open-pan cooking. Journal of Cereal Science. 2019;85:120-129. https://doi.org/10.1016/j.jcs.2018.11.007

35. Ángel-Rendón SV, Filomena-Ambrosio A, Cordon-Díaz S, Benítez-Sastoque ER, Sotelo-Díaz LI. Ohmic cooking: Application of a novel technology in pork and influences on water holding capacity, cooking loss and colour. International Journal of Gastronomy and Food Science. 2019;17. https://doi.org/10.1016/j.ijgfs.2019.100164

36. Inmanee P, Kamonpatana P, Pirak T. Ohmic heating effects on Listeria monocytogenes inactivation, and chemical, physical, and sensory characteristic alterations for vacuum packaged sausage during post pasteurization. LWT. 2019;108:183-189. https://doi.org/10.1016/j.lwt.2019.03.027

37. Llave Y, Udo T, Fukuoka M, Sakai N. Ohmic heating of beef at 20 kHz and analysis of electrical conductivity at low and high frequencies. Journal of Food Engineering. 2018;228:91-101. https://doi.org/10.1016/j.jfoodeng.2018.02.019

38. Alampresea C, Cigarinib M, Brutti A. Effects of ohmic heating on technological properties of whole egg. Innovative Food Science and Emerging Technologies. 2019;58. https://doi.org/10.1016/j.ifset.2019.102244

39. Joeres E, Schölzel H, Drusch S, Töpfl S, Heinz V, Terjung N. Ohmic vs. conventional heating: Influence of moderate electric fields on properties of egg white protein gels. Food Hydrocolloids. 2022;127. https://doi.org/10.1016/j.foodhyd.2022.107519

40. da Silva AM, Scherer LG, Daudt RM, Spada JC, Cardozo NSM, Marczak LDF. Effects of starch source and treatment type - Conventional and ohmic heating - On stability and rheological properties of gels. LWT. 2019;109:7-12. https://doi.org/10.1016/j.lwt.2019.04.006

41. Jung H, Moon JH, Park JW, Yoon WB. Texture of surimi-canned corn mixed gels with conventional water bath cooking and ohmic heating. Food Bioscience. 2020;35. https://doi.org/10.1016/j.fbio.2020.100580

42. Bhattacharjee C, Saxena VK, Dutta S. Novel thermal and non-thermal processing of watermelon juice. Trends in Food Science and Technology. 2019;93:234-243. https://doi.org/10.1016/j.tifs.2019.09.015

43. Fadavi A, Salari S. Ohmic heating of lemon and grapefruit juices under vacuum pressure - comparison of electrical conductivity and heating rate. Journal of Food Science. 2019;84(10):2868-2875. https://doi.org/10.1111/1750-3841.14802

44. Sabancı S, Icier F. Effects of vacuum ohmic evaporation on some quality properties of sour cherry juice concentrates. International Journal of Food Engineering. 2019;15(9). https://doi.org/10.1515/ijfe-2019-0055

45. Brochier B, Mercali GD, Marczak LDF. Effect of ohmic heating parameters on peroxidase inactivation, phenolic compounds degradation and color changes of sugarcane juice. Food and Bioproducts Processing. 2018;111:62-71. https://doi.org/10.1016/j.fbp.2018.07.003

46. Hwang JH, Jung AH, Park SH. Efficacy of Ohmic Vacuum Concentration for orange juice concentrates and their physicochemical properties under different voltage gradients. LWT. 2022;154. https://doi.org/10.1016/j.lwt.2021.112750

47. Hashemi SMB, Mahmoudi MR, Roohi R, Torres I, Saraiva JA. Statistical modeling of the inactivation of spoilage microorganisms during ohmic heating of sour orange juice. LWT. 2019;111:821-828. https://doi.org/10.1016/j.lwt.2019.04.077

48. Gavahian M, Sastry SK. Ohmic-assisted peeling of fruits: Understanding the mechanisms involved, effective parameters, and prospective applications in the food industry. Trends in Food Science and Technology. 2020;106:345-354. https://doi.org/10.1016/j.tifs.2020.10.027

49. Silva-Vera W, Avendano-Munoz N, Nunez H, Ramírez C, Almonacid S, Simpson R. CO2 laser drilling coupled with moderate electric fields for enhancement of the mass transfer phenomenon in a tomato (Lycopersicon esculentum) peeling process. Journal of Food Engineering. 2020;276. https://doi.org/10.1016/j.jfoodeng.2019.109870

50. Sawant SR, Pandey JP, Singh A, Prakash O. Performance and evaluation of ohmic heating assisted lye and salt concentration on peeling quality of tomato. International Journal of Current Microbiology and Applied Sciences. 2018;7(9):3515-3524. https://doi.org/10.20546/ijcmas.2018.709.436

51. Zhu F. Modifications of starch by electric field based techniques. Trends in Food Science and Technology. 2018;75:158-169. https://doi.org/10.1016/j.tifs.2018.03.011

52. Waziiroh E, Schoenlechner R, Jaeger H, Brusadelli G, Bender D. Understanding gluten-free bread ingredients during ohmic heating: function, effect and potential application for breadmaking. European Food Research and Technology. 2022;248(4):1021-1034. https://doi.org/10.1007/s00217-021-03942-4

53. Llave Y, Morinaga K, Fukuoka M, Sakai N. Characterization of ohmic heating and sous-vide treatment of scallops: Analysis of electrical conductivity and the effect of thermal protein denaturation on quality attribute changes. Innovative Food Science and Emerging Technologies. 2018;50:112-123. https://doi.org/10.1016/j.ifset.2018.09.007

54. Llave Y, Fukuda S, Fukuoka M, Shibata-Ishiwatari N, Sakai N. Analysis of color changes in chicken egg yolks and whites based on degree of thermal protein denaturation during ohmic heating and water bath treatment. Journal of Food Engineering. 2018;222:151-161. https://doi.org/10.1016/j.jfoodeng.2017.11.024