novel non thermal technique for food preservation

1. Dense Phase Carbon Dioxide Technology- A Non-thermal Food Preservation
Technique
Rohit K. Varma
M.Tech.(Food Process Engineering)
AGRICULTURAL AND FOOD ENGINEERING DEPARTMENT
INDIAN INSTITUTE OF TECHNOLOGY
KHARAGPUR
18AG63R19
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2. CONTENT
Introduction
Types of DPCD TREATMENT SYSTEM
Mechanism of Microbial and Enzymatic Inactivation
Factors affecting microbial inactivation
Application
Advantages and limitation
Case study
Result and discussion
Conclusion
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3.  The need for a food preservation method is to make safe,
inexpensive foods with preservation of heat sensitive compounds.
 CO2 is used because of its safety, low cost, and high purity.
 Dense-phase carbon dioxide (DPCD) treatment is a non-thermal
treatment of liquid foods or solid food which inactivates micro-
organisms without the loss of nutrients or quality changes that may
occur due to thermal effects.
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INTODUCTION

4. In the DPCD process, food is contacted with pressurized sub- or
supercritical CO2 for a period of time in a batch, semi-batch or
continuous manner.
It is mainly used for liquid food
Liquid food product are pasteurized in order to eliminate risk of
food poissoning and to increase their shelf life.
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5. Introduction
“Non-Thermal” food processing technique
“Cold Pasteurization”
In Contact with FoodsDense Phase CO2
Food
material
Dense Phase
Co2
Sub-Critical or Supercritical CO2
Microbial Inactivation due to Chemical Action of
CO2
< 40 MPa
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6.  CO2 pressures : < 40 MPA (7.0 - 40.0 MPa)
 Process temperatures: 20 - 60C.
 Treatment times:
3 to 9 min (continuous)
40 to 120 min (semi-continuous or batch processes)
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OPERATING CONDITIONS

7. Why dense phase?
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Gases
High diffusivity
Less solvating power
Dense phase
(sub or super-critical phase)
High diffusivity (gas –like)
and high solvating power(liquid –like)
Liquids
High solvating power
Less diffusivity
Combined
properties

8.  3 types of treatment systems are used:
 Batch type:- Both CO2 and treatment solution are stationary in a
container during treatment.
 Semi-continuous type:- continuous flow of CO2 through the
chamber while liquid food is stationary.
 Continuous type:- Flow of both CO2 and the liquid food.
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DPCD TREATMENT SYSTEM

9. 9

10.  A typical batch system mainly has a CO2 gas cylinder, a pressure
regulator, a pressure vessel, a water bath or heater, and a CO2
release valve.
The sample is placed into the pressure vessel and temperature is set
to the desired value.
Then, CO2 is introduced into the vessel until the sample is saturated
with CO2 at the desired pressure and temperature.
 The sample is left in the vessel for a period of time and then CO2
outlet valve is opened to release the gas.
Some systems contain an agitator to decrease the time to saturate the
sample with CO2.
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11. 11

12.  A continuous micro-bubble system, very effective in inactivating
microorganisms.
 In this system, liquid CO2 and a saline solution were pumped through a
vessel.
 Liquid CO2 was changed to gas using an evaporator and then dispersed
into the saline solution from a stainless steel mesh filter with 10 m pore
size.
 The micro-bubbles of CO2 moved upward while dissolving into the
solution.
 Then, the solution saturated with CO2 was passed through a heater to
reach the desired temperature.
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13. SEMICONTINOUS TEATMENT SYSTEM
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14.  semi-continuous system using a cylindrical filter to micro-bubble
CO2 entering into the pressure vessel.
 The inactivation of enzymes using a micro pore filter was 3 times
more than without using it.
 CO2 is increased from 0.4 to 0.92 mol/L in the sample at 25 MPa
and 35 °C.
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15. Lowering of pH
Cell membrane modification
 Intracellular pH decrease
Enzyme inactivation
Inhibition of metabolism
Removal of cell constituents
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Mechanism of Microbial and Enzymatic Inactivation

16. Step 1: Lowering of pH
CO2 in the water forms carbonic acid (H2CO3) which
dissociates into bicarbonate, carbonate and hydrogen
ionic species
This lowered extracellular pH may inhibit microbial
growth
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17. Step 2: Cell membrane modification
CO2 diffuses into the cellular membrane
CO2 Accumulates into its phospholipid inner layer
Accumulated CO2 may structurally and functionally
disorders the cell membrane due to an order loss of the
lipid chain which may increase fluidity and then
increases permeability of the membrane.
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18. Step 3: Intracellular pH decrease :
CO2, may easily penetrate through the bacterial cell
membrane and accumulate in the cytoplasmic interior
of bacterial cells
unbalance pH gradient
 So that microbial cells are unable to maintain a
favourable cytoplasmic pH homeostasis and many
aspects of cell structure and function are influenced
by internal pH .
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19. Step 4: Enzyme inactivation
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 Enzymes, which make up most of the proteins have
maximal activity at the optimum pH, and their activity
declines sharply on either side of the optimum.
 Lowering of internal pH might cause inhibition or
inactivation of key enzymes essential for metabolic and
regulatory processes so that affects on metabolism and
cellular function

20. Step 5: Inhibition of metabolism :
The rate of enzymatic reaction is not only a function of the
pH but also of the intracellular concentrations of its
substrate(s), product(s), and cofactor, which are primary
elements in the regulation of enzymatic activity.
The concentration of HCO3- is main element regulation of
enzymatic activity (and hence cellular metabolism).
Dissolved CO2 can inhibit decarboxylation reactions.
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21. Step 6: Removal of cell constituents
The pressurized CO2 first penetrates into the cells to build
up the density to a critical level within the cells. Then there
is a sudden release of the applied pressure which disturbs
the structure of the bio-membrane, leading to removal of
the intracellular constituents, (such as phospholipids and
hydrophobic compounds) out of the biological system into
the extracellular environment.
This extraction disturbs the balance of the biological
system and thus promoting inactivation.
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22. Factors Effecting Microbial Inactivation
Pressure
Temperature
Initial pH
Physical state of CO2
Moisture content
Nature of microorganisms
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23. Pressure
Increase in the pressure increase in the microbial inactivation.
At higher pressures, a shorter exposure is needed to inactivate the
same level of microbial cells.
Higher the pressure more is the CO2 solubilisation rate and this
facilitates acidifications.
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24. Temperature
Inactivation rate increases with increasing temperature
Higher temperatures stimulate the diffusivity of CO2
Also increase the fluidity of the cell membrane to make penetration
of CO2 easier
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25. Water activity, aw :
Microbial inactivation strongly depends on water activity, aw
Kamihira and others (1987) compared inactivation of:
wet cell (70% - 90% water) and
dry cell (2% - 10% water) of Baker’s yeast
Dry cells: inactivated by < less than 1 log
Wet cells: inactivated by 5 to 7 logs
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26. Effect of initial pH of medium
Enhanced microbial inactivation with a lower initial pH of the cell
suspension.
The lowered pH apparently contributed to an increase in cell
permeability to facilitate the penetration of CO2 into cells.
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27. Nature of microorganism
 Microbial sensitivity to DPCD treatment varies greatly among species
 In general, Gram +ve bacteria are more resistant than Gram –ve due
to the composition of their thicker cell wall
 Spore forming bacteria are more resistant require higher
temperatures
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28. Physical state of CO2
Supercritical CO2 is more effective than CO2 under sub-critical
conditions
Could be attributed to its interesting physic-chemical properties,
which are in between those of liquids and gases
Supercritical CO2 has liquid-like density while mass transport
properties are gas-like
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29. 29

30. Food Target micro-
organism
Microbial
inactivation
Pressure/temp. - time
Flour Mold 99.8% 6.2MPa/23°C- 2hr
Strawberries Bacteria 99.6% 6.2MPa/22°C- 2hr
Onion Bacteria 99%
5.5MPa/23°C- 2hr
Chicken meat Salmonella
typhimurium
94-98% 13.7MPa/35°C- 2hr
Kimchi vegetables Lactic acid bacteria 4 log 6.9MPa/10°C- 24hr
Leafstalks Natural micro-
organisms
4 log 6.9MPa/31.4°C- 1 hr
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31. DPCD treatments on solid of foods
Longer treatment time is needed limited diffusion of CO2
into the solid matrices
Sensory properties could be adversely affected
Possibly extract essential food compounds
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32. ADVANTAGES OF DPCD
 Gives fresh like food also after the treatment.
 Improve the overall qualities of food materials.
 Low capital and operational cost.
 Waste free, environment friendly and energy
efficient technology.
 Lower pressure and temperature required as
compare to HPP.
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33. 33
 Low flow rate.
 Not possible at atmospheric conditions.
 Does not give complete inactivation of spoiled food
product.
LIMITATION
LIMITATION OVER HPP
 Lower cost than HPP
 Lower operating pressure than HPP
 Spores can also be inactivated

34. Pasteurization of apples juice with dense phase carbon
dioxide
OBJECTIVE: Microbial inactivation and increasing shelf life
of apple juice treated with high pressure carbon dioxide.
Material required:
- Batch type DPCD
- Apple juice
- Growth media (PCA plate count agar).
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35. EXPERIMENT
 THERMAL INACTIVATION :
50 mL of apple juice placed in vessel and heated at temp 35,60 & 85°C for
time 120,80,60 min. After treatment sample collected in bottle and kept for ice
bath at 4°C for 10 min. and then analysed.
 DPCD INACTIVATION :
For experiment, 50 mL of apple juice was placed in the vessel, heated to
the experimental temperature and then pressurized by CO2. After treatment
sample collected in bottle and kept for ice bath at 4°C for 10 min. and then
microbial load, °Brix, pH and color were measured when complete inactivation
was achieved
Temp: 35,50,60°C
Pressure: 7,13,16 MPa 35

36. pH determination:
The pH of HPCD treated, untreated and thermally treated apple juice
samples was measured using a digital pH meter
°Brix determination:
A digital refractometer was used. A representative sample from juices was
taken by a disposable plastic pipette and °Brix values were determined.
Color analysis:
Color was measured using a Chroma Meter
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37. 1 2
RESULTS

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40. Results
No microbial growth for 56 days after treatment
No significant differences in sensory attributes between SC-CO2
treated juice and freshly extracted juice
Colour of the juice was retained (delta E = 0.63 – 1.15)
88% of its vitamin C was preserved
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41. 41
Pateurised Juice SC-CO2-treated Juice Freshly extracted Juice

42. CONCLUSION
 The total aerobic bacterial growth of the apple juice was inactivated by a
HPCD treatment
 Various log reduction were observed depending on the pressure,
temperature and treatment time conditions.
In some years, HPCD treatment could become one of the most
available emergent technologies
Further research is essential to demonstrate and explain the effect of
HPCD preservation on the shelf life and safety of food products
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43. Joyner J. & DhineshKumar V2 (2016). Cold Pasteurisation of Liquid
Foods using Dense Phase Carbon Dioxide. Food and Dairy Technology,
4:2347-2359
Murat O Balaban (2014). Microbial inactivation and shelf life of apple
juice treated with high pressure carbon dioxide. Biological Engineering,
14: 269-275
Shafat Khan, Amaresh, Keshavalu & S. Ghosh (2017). Dense Phase
Carbon Dioxide: An Emerging Non Thermal Technology in Food
Processing. Physical Science International Journal 16(1): 1-7
S. Spilimbergo & A. Bertucco (2003). Non-Thermal Bacteria Inactivation
With Dense CO2. Wiley InterScience, 19(8): 2033-2045
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REFERENCES

44. Thank You
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