Seminar onShelf-life extension of minimally processed

carrots by gaseous chlorine dioxide

Submitted by –Sthitaprajna Moharana.Adm. No. – 59E/10.CAET,BBSR.

1. Introduction2. Objective3. Material & methods4. Result & discussion5. Conclusion

Contents -

peeling husking slicing chopping

blanching dipping Hurdle techrefrigeration

1.Introduction -What is Minimal processing?‘Minimal processing’ describes non thermal technologies to process food in a manner to guarantee the food safety and preservation as well as to maintain as much as possible the fresh-like characteristics of fruits and vegetables.

A flow diagram of typical minimal processing operations for vegetables-

• Prolong the self-life of minimally processed carrots.• Why opted for ClO₂?1. Chlorine dioxide (ClO₂) is a decontaminant for vegetables,

as its efficacy is less affected by pH and organic matter .2. It does not react with ammonia to form chloramines, as do

liquid chlorine and hypochlorites.3. It is a strong oxidizing and sanitizing agent that has a broad

and high biocidal effectiveness. Because gas has greater penetration ability than liquid.

2.Objective -

3.Material & methods -

1. Carrot processing2. ClO₂ gas treatment3. Respiration rate measurements 4. Packaging of the MP carrots5. Shelf-life study

Stored over night before use(at 4°C)

Immersed in tap water (at ambient temp. for 1 min & dried for 1 min by manual kitchen centrifuge)

Converted in to 0.3*0.3*4 cm sticks

Sorted

4kg of carrot cubes were prepared

The Bulk is divided in to 2 parts

Carrots purchased from local market

2kg treated with ClO₂2kg not treated with ClO₂

3.1.Carrot processing -

3.2.ClO₂ gas treatment -

cabinet

Specification – 48L capacity with glass window (covered by aluminium foil). RH is maintained 91% by a flow of hot wet air (4 l/h).

2kg of grated carrots

A 1000 mg/l solution of ClO₂ was prepared & warmed up to 48 °C, by air bubbling (4 l/h), and ClO₂ stripped out. ClO₂ is then led by the same air stream to the cabinet through perforated plastic pipes. Treatment was performed at 28 °C and took 6 min & 30 s of stripping.

used to measure R.H. & temperature.

thermohygrometer

3.3.Respiration rate measurements -

Air-tight glass jar (635±11 ml)

Stored at 7ͦ C

Injection of initial gas mix.(13% O₂ ,1% CO₂ ,86% N₂)

5 replicas were made

Gas sample was taken periodically through an airtight septum and analysed by gas chromatography.

100 gm MP carrot

3.4.Packaging of the MP carrots -

Bags i.e. experimental films with O₂ permeability at 7°C & 90% RH

Injection of Initial gas mixture (4.5% O₂ ,8.9% CO₂ ,86.6% N₂)

100 gm MP carrots

10.5 cm

20 cm

Samples were packed under EMAP with a constant gas composition inside it for better shelf-life.

Untreated and treated MP carrots were packed in the designed bags and stored at 7 °C.

The samples were analysed for :-1. Headspace O2 and CO2 monitoring2. Microbiological analysis of spoilage microorganisms3. Evaluation of sensory quality4. pH measurement The end of the shelf-life arrived when the population of a group of microorganisms reached

an unacceptable level when the sensory panel rejected the samples.

3.5. Shelf-life study-

1. Respiration rates 2. ClO2 degradation3. Headspace O₂ and ClO₂concentrations4. Microbial analysis during shelf-life5. Sensory analysis during self-life

4.Results and discussion -

Since ClO₂ is an oxidant, the metabolism of the carrot tissue of treated sample differs from the untreated one.

Respiration rates of untreated samples =10.69±3.63 ml O2/kg h

treated samples = 9.98±3.47 ml O2/kg h. The average of both was taken to calculate the

packaging configuration with regard to the shelf-life study.

4.1. Respiration rates -

4.2. ClO2 degradation -

Fig. 1. Concentration of ClO₂ gas during the treatment of MP carrots

From the fig. It is observed that

The highest ClO2 concentration was 1.33 mg/l, measured after finishing the stripping.

The concentration of this gas increased during the stripping time and then fell to nil before 6 min.

Complete consumption of ClO2 is desirable, otherwise it is necessary to evacuate and destroy it. It is known that ClO2 is unstable and is also absorbed by plastic and glass.

Tests ran with empty treatment cabinet showed that these effects were negligible for up to 10 min.

4.3. Headspace O₂ and CO₂ concentrations -

The desired O₂ concentration is 3%, in both treated & untreated samples it was 4%.

The CO₂ concentration was 6%.

Therefore, for ClO₂ treated samples, the designed EMAP was able to keep O₂ and CO₂ concentrations at the desired levels enough to retard respiration without causing fermentation.

4.4. Microbial analysis during shelf-life -

Fig.2. Mesophilic aerobic bacteria counts of untreated (—○—) and ClO₂ gas treated (—●—) minimally processed carrots stored at 7 °C under MAP. Horizontal line indicates the limit for shelf-life. Error bars are mean±standard deviation

Fig. 3. Psychrotrophs count of untreated (—○—) and ClO₂ gas treated (—●—) minimally processed carrots stored at 7 °C under MAP. Horizontal line indicates the limit for shelf-life. Error bars are mean±standard deviation.

Fig. 4. Lactic acid bacteria count of untreated (—○—) and ClO₂ gas treated (—●—) minimally processed carrots stored at 7 °C under MAP. Error bars are mean±standard deviation.

Fig. 5. Yeasts count of untreated (—○—) and ClO2 gas treated (—●—) minimally processed carrots stored at 7 °C under MAP.Horizontal line indicates the limit for shelf-life.Error bars are mean±standard deviation.

Fig. 6. Changes in pH of untreated (—○—) and ClO₂ gas treated (—●—) minimally processed carrots stored at 7 °C under MAP. Error bars are mean±standard deviation

4.5.Sensory analysis during self-life-

Gaseous ClO₂ is a promising alternative to prolong the shelf-life of MP carrots.

Under the conditions used in this work, a treatment with gaseous ClO₂ does not affect the respiration rate nor the sensory attributes of MP carrots.

It decontaminate them and prolong their shelf-life for 1 day.

Yeast growth limited the shelf-life of treated samples.

Conclusion -