Ozone as a Microbial Sanitizer For Fruits and Vegetables

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GAJANAN .A.G ID.NO- 20594M.SC (PHT)

Division of Post Harvest Technology

Spoilage of fruits & vegetables

• Soil (Bacillus, Clostridium fungi)

• Wide distribution in nature (Lactobacillus, Leuconostoc, Streptococcu

• Water (irigation, solvent, washing)

• Dust (air)

• Animals, insects, humans

• Harvesting equipment and utensils

• Packing equipment

• Transporting vehicles

• Cross contamination.

Techniques Used for Microbial Disinfection

• Irradiation • Hot water treatment • Chemicals• Chlorine • Ozone • Biological agents etc.

Ozone as an effective tool

Process of ozone generation

Mode of action

Safety aspects of ozone

Case study

Inference

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Ozone is an Effective Tool

• Christian Friedrich Schönbein (Discoverer, 1839)

• USFDA granted as GRAS status in 2001

• Maximum 8-hour average personal exposure limit at 0.1 ppm

• Toxicity symptoms such as Headache, Dizziness, eye & throat infection etc.)

• Ozone is a strong oxidant & Disinfecting agent.

• Eco-friendly - Does not leave residues .

• Rapid auto-decomposition to diatomic O2 .

• Ozone is a powerful antimicrobial agent.

• Good component in hurdle technology

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Process of ozone generation

• Involves passage of oxygen containing gas through either a source of

UV radiation or a high energy electrical field.

3O2↔2O3

• Various methods of generation include

Photochemical (UV) method

Corona Discharge technique

Electrolysis method

Radiochemical method

Reaction of elemental Phosphorus with water etc.

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Indian Agricultural Research Institute, New Delhi

Corona Discharge Method

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Mode of action • Acts on the cell membrane - glycoprotein / glycolipids (guzel-seydim et al.,

2004) & Cell constituents (unsaturated fatty acids, enzymes, nucleic acids)

Mechanism of ozone destruction • (1) ozone oxidizes sulfhydryl groups and amino acids of enzymes, peptides

and proteins to smaller peptides• (2) ozone oxidizes Polyunsaturated Fatty Acids to acid peroxides

• Microorganisms are inactivated by disruption of the cell envelope or disintegration leading to cell lysis.

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Product Ozone treatment Target microorganism Salient findings

Carrot Ozone concentration of 50 ± 10 μl/L

Sclerotinia sclerotiorumBotrytis cinerea

Reduced lesion size and aerial mycelium of both pathogens

BlackberryStored for 12 days at 2 °C in 0.1 and 0.3 ppm ozone.

Fungal decay control (Botrytis cinerea)

suppressed fungaldevelopment for 12 days.

Strawberry cv. Camarosa

Stored at 2 °C in an atmospherecontaining ozone (0.35 ppm)

Fungal decay control (Botrytis. cinerea)

Preventingfungal decay

PeachContinuous ozone exposure at 0.3 ppm for 4 wks at 5 °C and 90% RH.

Monilinia fructicola

control of brown rot

Tomato 5.0 μmol/mol up to 13 days at 13 °C.

Alternaria alternata orColletotrichum coccode

Significant reduction in fungal lesion developmnt.

Use of ozone in fruits and vegetables

Source : Ozone in Food Processing , (2012 )Wiley Blackwell Publishing Ltd.

Ozone video

Effects of ozone on major antioxidants and microbialpopulation of fresh-cut papaya

Yeoh et al., 2014

Indian Agricultural Research Institute, New Delhi

Postharvest Biology and Technology, 89: 56-58

Objective- • To determine the effect of ozone at different exposure times on the

phytochemicals and microbial loads in fresh-cut papaya .

Treatments-• Ozone 9.2 ± 0.2 ul/L • Treatment duration (10, 20 and 30 min.)

Materials & Methods:• ‘Foot Long’ papaya at yellow maturity • Data analyzed by using Duncan’s multiple range test with significance level

of (p<0.05)

Ozone exposer

time (min )

Total phenolic content (ug GAE/g FW)

FRAP (u mol of Fe (II)/g FW)

(Anti-oxidant )

Ascorbic acid content

(mg/100g FW)

Total microbial population (log10 CFU/g)

Mesophilic bacteria

Coliforms

Control 229.91±3.19 b 304.07±3.56 b 85.25±1.71 b 2.67 1.81

10 248.97±6.15 a 325.38±8.21 a 92.50±1.29 a 2.45 a1.42 b

20 253.67±4.82 a

330.38±6.75 a 87.25±0.50 b2.37 a 1.42 b

30 227.22±3.78 b 306.81±4.67 b 78.38±2.56 c2.34 a 0.69 a

The effect of different exposer time of 9.2±0.2 ul/L ozone on the antioxidants and population of Mesophilic and coliform bacteria on fresh-cut papaya.

8.3 %

1.2

7.0

8.7 10.3 2

6.7

7.25

4 times

Inference

• The sample exposure to 9.2±0.2 ul/L ozone, the TPC of the samples increased significantly by 8.3 % & 10.3 % for 10, 20 min respectively but prolonged exposure to 30 min leads to the decrease of TPC to 1.2 % .

• Increase in anti-oxidant content when sample exposure to 10 , 20 min .

• Exposure of cut-papaya to 10 min increase the Ascorbic acid content to 7.25 mg/100 gm while subsequent decrease in Ascorbic acid content with exposure of 20 & 30 min.

• In this experiment reduction of coliforms was approximately four times higher than that of mesophiles.

Effect of ozone treatment on microflora of dried figs

Indian Agricultural Research Institute, New Delhi

O-ztekin et al., 2006

Journal of Food Engineering, 75 : 396-399

Case Study- 2

Objective- To determine the influence of ozone treatment in gas form on microbial flora, aflatoxin B1 in dried figs.

Treatments- Ozone concentration is 1 , 5 , 10 ppm Treatment duration 3 , 5 hours .

Materials & Method Dried Sarıop–Calimyrna–figs Fruits were stored in a cold room at 4oC .

Effect of exposure time and ozone concentration on microorganism count on dried fig (log cfu/g)

Indian Agricultural Research Institute, New Delhi

Microflora Exposure time (hours)

Ozone concentration ( ppm )

1 5 10

Total aerobic mesophyllic microorganisms

0 2.57 a (a) 2.57 a (a) 2.57 a (a)3 2.51 a (a) 2.07 b (b) 2.00 b (b)5 2.11 a (a) 1.97 b (a) 1.59 b (a)

Coliform 0 1.46 a (a) 1.46 a (a) 1.46 a (a)3 0.39 b (a) 0.00 b (a) 0.00 b (a)5 0.23 b (a) 0.00 b (a) 0.00 b (a)

Yeast / Mould 0 1.46 a (a) 1.46 a (a) 1.46 a (a)3 1.30 ab (a) 0.73 a (a) 0.57 ab (a)5 1.00 b (a) 0.57 a (a) 0.40 b (a)

Inference• Statistical analyses show that both of the concentration levels and exposure times can

be considered significantly different at the 0.05 confidence level.

• At the 5 and 10 ppm level no coliform bacteria were found.

• To reduce yeast/mould activity, ozone could be applied either for longer periods at low concentration, or conversely for short period with higher concentrations.

• No significant difference between two exposure times, namely three and five hours has been found except for the total aerobic mesophyllic microorganisms.

• It can be concluded that a minimum of three hours ozone treatment at 5 ppm could be successfully used for reducing the microbial count of dried figs.

• The destroying yeast and molds just after harvesting will certainly reduce the possibility of aflatoxin formation before the next processing steps.

CASE STUDY-3

Objective-

(i) The effect of continuous kiwifruit exposure to ozone on disease development. (ii) The effect of pre- and post-inoculation ozone exposure on disease development. Treatments- ozone at a concentration of 0.3 µL L−1

Materials & Method ‘Hayward’ kiwifruit, In vitro and In vivo studies were carried out in cold storage rooms (0 ◦C, RH 95%)

56%

Stem-end rot caused by Botrytis cinerea on artificially infected ·Hayward ‘ kiwifruit during a 4 months cold storage period (0 °c ,RH 95 %) in a storage room with control or continuous supply of ozone 0.3 µL/L

Spore germination (%) of Botrytis cinerea during cold storage (0 °c , RH 95 %) under control or continuous exposure to ozone (0.3 µL/L) for 0,2,8,24 and 72 h , followed by 24 h incubation at 22 ° c in the dark.

Inference • Ozone applied in gaseous form at a concentration of 0.3 µL L−1 during long

term storage delayed the appearance of stem-end rot and also it reduces 56 % disease incidence compared to that of control kiwifruit.

• Pre-inoculation exposure to ozone may stimulate host resistance.

• Exposure of fungal spores to gaseous ozone for more than 8 h resulted in a significant reduction of spore viability.

Future Trust………….

• Since the ozone dosage, treatment time and temperature

could impact the efficiency in microbial disinfection, these

parameters should be optimized for different fruits and

vegetables in continuous and pulsed wave form.

• Research should be focused on development of improved

devices for O3 gas production and application.

• Should investigate the feasibility of direct production of O3

containing water without prior production of O3 gas.