Shelf-life extension of minimally processed carrots by gaseous chlorine dioxide

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Chlorine dioxide (ClO2) gas is a strong oxidizing and sanitizing agent that has a broad and high biocidal effectiveness and big penetration ability; its efficacy to prolong the shelf-life of a minimally processed (MP) vegetable, grated carrots (Daucus carota L.), was tested in this study. Carrots were sorted, their ends removed, hand peeled, cut, washed, spin dried and separated in 2 portions, one to be treated with ClO2 gas and the other to remain untreated for comparisons. MP carrots were decontaminated in a cabinet at 91% relative humidity and 28 °C for up to 6 min, including 30 s of ClO2 injection to the cabinet, then stored under equilibrium modified atmosphere (4.5% O2, 8.9% CO2, 86.6% N2) at 7 °C for shelf-life studies. ClO2 concentration in the cabinet rose to 1.33 mg/l after 30 s of treatment, and then fell to nil before 6 min. The shelf-life study included: O2 and CO2 headspace concentrations, microbiological quality (mesophilic aerobic bacteria, psychrotrophs, lactic acid bacteria, and
yeasts), sensory quality (odour, flavour, texture, overall visual quality, and white blushing), and pH. ClO2 did not affect respiration rate of MP carrots significantly (α≤0.05), and lowered the pH significantly (α≤0.05). The applied packaging configuration kept O2 headspace concentrations in treated samples in equilibrium and prevented CO2 accumulation. After ClO2 treatment, the decontamination levels (log CFU/g) achieved were 1.88, 1.71, 2.60, and 0.66 for mesophilic aerobic bacteria, psychrotrophs, and yeasts respectively. The initial sensory quality of MP carrots was not impaired significantly (α≤0.05). A lag phase of at least 2 days was observed for mesophilic aerobic bacteria, psychrotrophs, and lactic acid bacteria in treated samples, while mesophilic aerobic bacteria and psychrotrophs increased parallelly. Odour was the only important attribute in sensory deterioration, but it reached an unacceptable score when samples were already rejected from the microbiological point of view. The shelf-life extension was limited to one day due to the restricted effect of the ClO2 treatment on yeast counts. Nevertheless, ClO2 seems to be a promising alternative to prolong the shelf-life of grated carrots.

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Shelf-life extension of minimally processed carrots by gaseous chlorine dioxide

  1. 1. Seminar on Shelf-life extension of minimally processed carrots by gaseous chlorine dioxide Seminar on Shelf-life extension of minimally processed carrots by gaseous chlorine dioxide Submitted by – Sthitaprajna Moharana. Adm. No. – 59E/10. CAET,BBSR. Submitted by – Sthitaprajna Moharana. Adm. No. – 59E/10. CAET,BBSR.
  2. 2. 1. Introduction 2. Objective 3. Material & methods 4. Result & discussion 5. Conclusion Contents -Contents -
  3. 3. peelingpeeling huskinghusking slicingslicing choppingchopping blanchingblanching dippingdipping Hurdle techHurdle tech refrigerationrefrigeration 1.Introduction -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. 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.
  4. 4. A flow diagram of typical minimal processing operations for vegetables-
  5. 5. • Prolong the self-life of minimally processed carrots. • Why opted for ClO ?₂ 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 -2.Objective -
  6. 6. 3.Material & methods -3.Material & methods - 1. Carrot processing 2. ClO gas treatment₂ 3. Respiration rate measurements 4. Packaging of the MP carrots 5. Shelf-life study
  7. 7. Stored over night before use(at 4°C)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) 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 sticksConverted in to 0.3*0.3*4 cm sticks SortedSorted 4kg of carrot cubes were prepared4kg of carrot cubes were prepared The Bulk is divided in to 2 partsThe Bulk is divided in to 2 parts Carrots purchased from local marketCarrots purchased from local market 2kg treated with ClO₂2kg treated with ClO₂2kg not treated with ClO₂2kg not treated with ClO₂ 3.1.Carrot processing -3.1.Carrot processing -
  8. 8. 3.2.ClO gas treatment -₂3.2.ClO gas treatment -₂ 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. ClO is then₂ 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
  9. 9. 3.3.Respiration rate measurements -3.3.Respiration rate measurements - Air-tight glass jar (635±11 ml)Air-tight glass jar (635±11 ml) Stored atStored at Injection of initial gas mix.(13% O₂ ,1% CO ,86% N₂ ₂) Injection of initial gas mix.(13% O₂ ,1% CO ,86% N₂ ₂) 5 replicas were made5 replicas were made Gas sample was taken periodically through an airtight septum and analysed by gas chromatography. Gas sample was taken periodically through an airtight septum and analysed by gas chromatography. 100 gm MP carrot100 gm MP carrot
  10. 10. 3.4.Packaging of the MP carrots -3.4.Packaging of the MP carrots - Bags i.e. experimental films with O₂ permeability at 7°C & 90% RH Bags i.e. experimental films with O₂ permeability at 7°C & 90% RH Injection of Initial gas mixture (4.5% O ,₂ 8.9% CO ,86.6% N₂ ₂) Injection of Initial gas mixture (4.5% O ,₂ 8.9% CO ,86.6% N₂ ₂) 100 gm MP carrots100 gm MP carrots 10.5 cm 20 cm Samples were packed under EMAP with a constant gas composition inside it for better shelf-life.
  11. 11.  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 monitoring 2. Microbiological analysis of spoilage microorganisms 3. Evaluation of sensory quality 4. 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-3.5. Shelf-life study-
  12. 12. 1. Respiration rates 2. ClO2 degradation 3. Headspace O₂ and ClO₂concentrations 4. Microbial analysis during shelf-life 5. Sensory analysis during self-life 4.Results and discussion -4.Results and discussion -
  13. 13.  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 -4.1. Respiration rates -
  14. 14. 4.2. ClO2 degradation -4.2. ClO2 degradation - Fig. 1. Concentration of ClO₂ gas during the treatment of MP carrots
  15. 15. 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.
  16. 16. 4.3. Headspace O₂ and CO₂ concentrations -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.
  17. 17. 4.4. Microbial analysis during shelf-life -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
  18. 18. 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.
  19. 19. 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.
  20. 20. 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.
  21. 21. 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
  22. 22. 4.5.Sensory analysis during self-life-4.5.Sensory analysis during self-life-
  23. 23.  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 -Conclusion -

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