*5.1.4 Ozone*

Fresh cut fruits and vegetables are treated with ozone in gaseous or aqueous form to extend their shelf life. Ozone came under the category of generally regarded as safe and has been approved by US FDA as direct contact food sanitizers [41]. Ozone reacts with the intracellular enzymes, nucleic acids, spore coat, components of envelop or viral capsid of microorganism. Gaseous treatment of ozone (950 μl/20 min) on sliced lettuce and spinach results in 1.0–1.5 log reduction in *E. coli* and *Listeria innocua* [42]. 9 ppm exposure of gaseous ozone results in the reduction of 2.89, 3.06 and 2.56 log in *E. coli* O157, *Listeria monocytogenes, Salmonella Typhimurium*in fresh cut bell pepper. Fresh cut melon [43], apple, papaya [44] were treated with aqueous ozone (1.4 mg/5–10 min) shows significant reduction in the bacterial count while certain biochemical properties such as total phenols, PPO and POD activites, ethylene production and MDA content were reduced. Although ozone is being used in the preservation of fresh cut fruits and vegetables, special care must be given to the after effects caused by the long exposure and high concentration of it. Long exposure and increase concentration causes various health related problems so in this regard federal occupational safety and health administration in united states specified the limits on working environment (0.1 ppm for long term exposure and 0.3 ppm for short term exposure) [45]. All chemical approached for fresh cut fruits and vegetables are presented alongwith their advantages and disadvantages in **Table 1**.


#### **Table 1.**

*Latest chemical technologies to ensure safety and to increase shelf life of the fresh cut fruits and vegetables.*

*Fresh Cut Fruits and Vegetables Disinfection Pretreatment: A Novel Approach to Extend Fresh… DOI: http://dx.doi.org/10.5772/intechopen.107525*

### **5.2 Physical treatment**

#### *5.2.1 Modified atmosphere packaging*

MAP is the effective technique used for the preservation and extending shelf life of the fresh cut produce. In this technique, gas composition around the product is replaced with the inert gases like CO2, O2 and N2. MAP inhibits the growth of microorganisms by creating unfavorable conditions. Higher O2 concentration is used for the preservation of aroma producing volatile substances in fresh cut honeydew melon and cantaloupe stored for 12 days at 5°C. Meng et al. [47] reported that the concentration of O2 greater than 70% is proved to effective against the microbial growth and enzymatic browning in mushroom slices, shredded chicory endives and grated celeriac. The color evaluation under high O2 concentration of these three fresh cut produce donot exceed through 6–7 days while the control sample (5% O2 compensated with N2) was rejected after 3–4 days. Higher O2 concentration 50 or above 90% is effective in inhibiting the microbial growth, enzymatic browning in fresh cut lettuce stored for 6 days at 7°C [48]. Monnin et al. [49] through research concluded that the combination of high O2 and ascorbic acid are highly conducive to the inhibition of peroxidase and polyphenol oxidase activites and maintenance of biochemical properties of fresh cut eggplant result in extended in shelf life for 12 days at 4°C.The sample taken as control was also microbiologically accepted but the sensory score was less than the treated sample. 50% O2 and 50% CO2 shows the strong inhibition on the growth of yeast and the production of volatile compounds in fresh cut pineapple. This method was also reported to be responsible for the extension of shelf life. Apart from above mentioned gases, CO at low levels was also approved as GRAS as a gas used in MAP. CO is generally used in preservation of meat through MAP as it reduces the metmyoglobin and maintaining the cherry red color of meat. Very less literature is present which confirm the use of CO in fresh cut produce. Niemira [50] studied the use of CO (<175 ml/l) treatment for 20 min in fresh cut lotus root slices. This reduces the activites of PPO and POD. They also reported that the phenylalaineammonialyase (PAL) and malonaldehyde (MDA) content of treated sample were 17% lower and 40% higher than the non treated sample stored at 5°C for 8 days respectively but the controversy regarding the use of CO is still there. There are many other gases which are recently being used in MAP such as argon, helium and nitrous oxide. These noble gases indirectly affect the metabolism of the plant tissue. These gases increase the diffusivity of the O2 from the plant tissue there by affecting certain biochemical pathways and making unfavorable conditions for the growth of microorganisms. Study was done by [51] on browning in sliced apples. N2O and Ar (90% N2O, 5% O2, 5% CO2 and 5% CO2, 5%, 25% Ar) was used under high pressure in MAP. Results shows 15% and 25% browning in N2O and Ar treated respectively whereas 60% in control sample stored at 5°C for 12 days. On the other hand there is increase in firmness and total soluble solid content in the treated sample. The effect of noble gases (89.3% N2O, 89.9% Ar, 90.1% He) was compared with the air packaging in fresh cut watercress. Result shows that the C2H4 emission and the rate of respiration were low as compared to control but there was no effect on the growth of psychotropic and *Enterobactericeae* was observed. They suggest that the combination of other technologies with MAP to ensure the microbial safety in case of watercress [52].

#### *5.2.2 Electron beam irradiation*

Food irradiation is done for the preservation of fresh cut fruits and vegetable. Irradiation results in the negligible modification in the nutrients, taste, flavor, color and other qualities. Cobalt-60 is most frequently used radioisotope for the purpose of quality and safety of fresh produce. Lower doses of are proved to be effective in the preservation of food [46]. However these radiationshave the potential to cause cancer if used above permissible limits. EBI donot require any radioactive isotope for ionization. Electron beams are generated with the help of the machine capable of accelerating the electron close to the speed of light at high energy level in the range of 0.15–10 MeV in a vacuum environment [53]. Energy source is the commercial electricity and generator can be easily switched off and on. This technique helps to eliminate the micro flora present over the food by the destructing their DNA structure, membrane proteins and enzymes resulting in death of the organism. The effectiveness of the EBI depends the dosage of irradiation and type of food. Irradiation of blueberries with 2.3 and 3.13 kGy results in the 8.9–28 log CFU/g and 6 CFU/g decrease in the *E. coli* population. Fresh cut cabbage was treated with 2.3 and 4.0 kGy resulting in 4.0 and 7.0 log reduction in *E. coli* respectively. A research was conducted to study the correlation between the shelf life and irradiation dosage on blueberries. The result shows that the untreated blueberries decay to 39% while those treated with 2 and 3 kGy reports 8% and 3% decay respectively [38]. Mushrooms generally have shorter shelf life due to weight loss, enzymatic browning and texture changes. To overcome this mushrooms were treated with EBI at 2 kGy and then they result in the highest total antioxidant capacity, higher whiteness and lowest electrolyte leakage in mushroom. With increase in certain biochemical properties, there is decrease in vitamin C content. Despite of the successful applications discussed above, irradiation level is restricted by Food and Drug Administration (FDA) on fruits and vegetables. The maximum level at which is recommended is 1.0 kGy with the two exceptions, i.e., fresh lettuce and spinach which can be irriatedupto 4.5 kGy. Many trials of irradiation using EBI technique on fresh cut fruits is under progress, promising and encouraging results can be the hope for future research.

### *5.2.3 Pressurized inert gases*

Inert gases such as neon, argon, nitrogen, krypton, xenon are used in the preservation of fresh cut fruits and vegetables as these gases form the ice-like crystal structure called clathrate hydrate. The gas molecules get intraped into the cage like structure by water with the help of vander Waals forces and are stable at lower temperature [54]. Various studies have been done to study the role of inert gases in the preservation of fresh cut fruits and vegetables. Shelf life of fresh cut asparagus spears was extended from 3 to 5 days to 12 days by treating them with argo (Ar), xenon (Xe) under 1.1 MPa (Ar and Xe at 2.9(v:v) in partial pressure) for 24 h at 4°C. Ramos-Villarroel et al. [55] used the pressurized Argon (4 MPa) for 1 h on green peppers which results in decreased water mobility as well as loss of water, ascorbic acid growth of yeast and mold and maintaining the cell integrity by inhibiting the production of MDA and activites of POD and CAT (catalase). Use of argon on green peppers also results in the extension of shelf life to 12 days stored at 4°C as compared to the untreated ones having shelf life of 8 days. Shelf life of the fresh cut apples and pineapples can be extended from 9–7 to 15–12 days by the application of high pressure treatment of Ar at 150 MPa for 10 min and 1.8 MPa for 60 min respectively. However these treated samples possess lower scores in firmness than that of the untreated [56]. Further study was conducted by modifying this experiment by using combination of gases. Combination of argon and xenon as well as argon and nitrogen give promising results [57]. Lower growth of *Saccharomyces cerevisiae* and *E. coli* was observed in fresh cut apple and pineapple when treated with the mixture of xenone and argon under

**50**

### *Fresh Cut Fruits and Vegetables Disinfection Pretreatment: A Novel Approach to Extend Fresh… DOI: http://dx.doi.org/10.5772/intechopen.107525*

1.8 MPa (Xe and Ar at 2:9(v:v) in partial pressure as compared to the untreated sample. On the other hand loss of ascorbic acid and total phenols, lower browning were reported under high pressure (10 MPa) nitrogen and argon on fresh cut pineapples.

### *5.2.4 Ultraviolent light (UV)*

UV radiations are the non ionizing radiations having the wavelength in the range of 100 nm to 400 nm. These rays are classified into three different types: UV-A (315–400), UV-B (280–305), UV-C (100–280) [25]. UV-C at 254 nm is most prominently used due to its germicidal properties. UV rays causes the DNA damage in the living organism by inducing the formation of DNA photoproducts such as purimidine 6–4 pyrimidone and cyclobutane pyrimidine dimers which hinders replication and transcription and eventually leading to mutations and cell death [58]. The major advantage of UV rays is its broad spectrum action over microorganism, convenient manipulation and lower cost. Poor penetration of UV rays limits its use in food field. However, UV-C is frequently being used for the surface decontamination of fresh cut fruits and vegetables as enzymatic deterioration and surface spoilage mainly occur on surface [59]. Many studies on the use of UV on fresh cut produce gave the satisfying results. Salvia-Trujillo et al. [60] reports that by treating the fresh cut apples with 1.2 kJ/m2 UV-C lowers the microbial population to 2 log units as compared to the untreated ones stored at 6°C for 8 days. 12.5 kJ/m2 of UV-C shows the significant results in inhibiting PPO activity and browning in fresh cut carambola which remain fresh even after 21 days of storage. Similarly, significant results were observed in case of fresh cut apples [61]. Fresh cut peppers were treated with UV-C which eventually leads to 50% higher firmness as compared to the control sample stored at 12 day. Similarly, maintenance of antioxidant activity (DPPH activity), vitamin C content and total phenolic compounds of fresh cut paprika [62] and mandarin.

Unfortunately, due to the negative effects of UV-C on nutritional and sensory characteristic, it is in limited in use. Extended exposure of UV-C on fresh cut pineapples accelerates browning and significant decrease in Vitamin C content. High doses of UV-C causes weight loss and excess electrolyte leakage in fresh cut green onion [63]. Shelf life of watermelon is increased to 11 days at 5°C by treating it with low UV-C (1.6 and 2.8 kJ/m2 ) but when treated it with high UV-C (4.8 and 702 kJ/m<sup>2</sup> ), shelf life of 8 days. Therefore the use of combination of UV-C with citric acid [64], malic acid, electrolyzed water, modified atmosphere packaging [65], gaseous ozone [66] have been developed. Recently, UV- light emitting diodes are being used due to their long life expectancy, energy efficient, low cost, convenient manipulation, no harm to human eyes and skin and no liberation of mercury waste. UVA-LED shows significant results in disinfecting food by reduction of *E. coli* on fresh cut cabbage and lettuce whilemaking no loss of vitamin C. Although, antibrowning effect is associated with irradiance, the fruit cultivar and exposure time, effective in inhibiting browning in fresh cut pear and apple [67].

#### *5.2.5 Pulsed light (PL)*

PL is thenother technique used for decontamination of packaging material and food by inactivating the microorganisms. Short duration and high power pulses are generated with inert gas (generally xenon) lamp and involve broad spectrum white light. PL results in photochemical effect and results in structural changes in DNA of viruses, bacteria and other pathogen and interferes in replication and transcription resulting mutation and eventually death of the organism. The main advantages of

this technique areits low energy cost, its great flexibility, and significant reduction in very short time and lack of residual compounds. PL is recently being used for treating fresh cut fruits and vegetables. Treating fruits and vegetables with PL not only reduces the microflora, but also in the maintaience of sensory and nutritional properties of fresh cut produce. The efficiency of PL depends upon the number of pulses and intensity of the pulses. Low intensity may be ineffective while higher intensity may be toxic and cause undesirable damages. Various studies have been done on the preservation of fresh cut with the help of PL technique. Fresh cut mangoes was treated with pulsed light reports the conducive effect on the firmness, carotenoid and color of the fruit stored at 6°C for 7 days where as loss of color, firmnesswas observed in the control sample after 3 days of storage [68]. Carotenoid content oftreated sample was 9 mg/g dry matter as compared to 2 mg/g dry matter of untreated ones. Reduction in yeast and mold and maintenance of chlorophyll a and b in fresh cut avocado has been reported [69]. Exposure to high pulses (12 J/cm) results in significant reduction in *E. coli* and *Listeria innocua* in fresh cut mushroom [70]. Significant reduction was seen in *L. innocua*, *Escherichia coli, S. cerevisiae* in fresh cut apples when exposed to high pulses. However, browning action on the cut surfaces was promoted. It occurs mainly due to increase in temperature or thermal damage during the treatment which accelerates non- enzymatic and enzymatic browning. Moreover some negative effects on color, texture and sensory attributes have been reported [71]. To overcome this disadvantage combined technique was employed by [72]. PL treatment was combined with anti- browning pretreatment by dipping into mixed solution of 1%(w/v) ascorbic acid and 0.1%(w/v) calcium chloride with 71.6 J/cm2 PL dose shows the effective results in minimizing browning on fresh cut apples. Further research must be done to find improved application of PL combine with other techniques.

## *5.2.6 Cold plasma (CP)*

Cold plasma is anothernon-thermal technique used nowadays for the food decontamination and preservation. Plasma is defined as the fourth state of matter after solid, liquid, gas. It is the quasi neutral ionized gas which consists of photons, negative ions, free electrons, excites or non excited atoms and molecules. Various techniques are being employed for the production of plasma such as lasers, microwaves, magnetic field, electricity, direct and alternating current. Mixture of nitrogen, oxygen or mixture of other nobel gases are used in CP. Recombination process takes place between the active particles with the release of energy as visible and UV light. These active particles in the plasma react with the food substrate releasing the energy into the viruses and bacteria. Although, the exact mechanism of the inactivation is still not known but the primary mechanism of inactivation attributes to direct chemical interaction with the charged species, destruction of cellular components by UV and denaturation of DNA strand [73]. The proportion of the gas mixture and the specific energy source depend upon the chemical composition, temperature and density of the plasma. Apart from these protein, fat content, texture, pH and texture of the food also depends. This treatment is successfully applied for microbial decontamination on strawberry, potato, cherry, cabbage and milk representing significant results. Yeoh et al. [74] reported 1.76, 2.72, 0.94 log reduction of *Salmonella typhimurium* on strawberry, lettuce and potato by the use of CP technique. Another study was done on strawberries by [75] which reports 44–95% reduction of yeast and mold count and 12–85% reduction of mesophilic count. Beside this no significant change occur in color, texture and firmness of the treated product. CP treatment was given for 10,

*Fresh Cut Fruits and Vegetables Disinfection Pretreatment: A Novel Approach to Extend Fresh… DOI: http://dx.doi.org/10.5772/intechopen.107525*

60 and 120 s to tomato resulted in 3.1, 6.3 and 6.7 log 10 CFU/sample reductions of *Salmonella, E.coli and L.monocytogenes* from the initial sample. Similar but extended treatment was given to strawberries due to its complicated surface [76] reports that 0, 15, 30, 45, 60, 90 and 120 s treatment with CP to blueberries result in the reduction of yeast/molds and total aerobic plate count to 1.5–2.0 CFU/g and 0.8–1.6 log CFU/g as compared to the controlled sample after 1 and 7 days respectively. Above mentioned studies was mainly concentrated on the fresh produce. Very few literatures is present on the application of CP on fresh cut produce due to its early stage of development. Browning area and PPO activity in fresh cut apples is reduced to 65% and 12–58% respectively by treating it with CP for 30 min compared to control after 4 h of storage. In fresh cut melon 17% POD and 7% PME activity inhibition of fresh cut melon is achieved by treating them with CP. Study done by few scientists claimed that the treatment with CP results in improved color retention and reduced browning in fresh cut kiwi fruit during storage. In addition no significant change occur in antioxidant content and antioxidant activity but slight change(up to 10%) was seen in fresh cut apples after treatment [77]. CP has gained much attention during last decade due to its promising results. However, much information about its effects on food quality and mechanism involved is unknown [78]. Further study is needed regarding physiochemical reaction kinetics, sensorial and nutritional properties of foods. Safety issued are also not verified in case of CP. Therefore integrated risk assessment is required for its application at its commercial use.
