**3.4. Pulsed light (PL)**

Pulsed light (PL) involves the use of intense, short duration pulses of light over a broad spectrum of wavelengths ranging from UV (180–380 nm), visible light (380–700 nm) to nearinfrared (700–1100 nm); mainly used for decontamination of surface microorganisms on food and packaging [50, 51]. The basic components of a PL system incorporates three main parts: a lamp (xenon gas lamp), a power supply and a pulse configuration device (controller); configured in either batch or continuous flow design depending on the food material to process (see **Figure 4**) [52]. The mechanism of PL on microbial inactivation is attributed to both photochemical and photothermal effects. UV radiation is absorbed by carbon–carbon double bonds in An Evaluation of the Impact of Novel Processing Technologies on the Phytochemical… http://dx.doi.org/10.5772/intechopen.77730 199

**Figure 4.** Schematic diagram of a high intensity pulsed-light system. Adapted from Abida et al. [52].

compounds might be attributed to the breakdown of cell walls and disruption of chromoplasts created by cavitation pressures allowing for release of membrane bound carotenoids. These results were similar to Abid et al. and Zou and Hou, when investigating US on different quality parameters of apple and blue berry juice respectively [46, 47]. Sonication showed increased levels of ascorbic acid, total phenolics, flavanols and flavonoids, and increased antioxidant activity due to the extraction and availability of these compounds. In a contrasting study by Dias et al. soursop juice subjected to varying levels of sonication energy, showed that increasing US intensity resulted in lower levels of phenols, ascorbic acid and higher levels of total color difference between sonicated and untreated samples [48]. The apparent decreases in overall phytonutrient content was attributed to increasing temperature and free radical formation that produced strong oxidizing effects during cavitation. Yao et al. investigating the effects of US on cyanidin-3-glucoside in blueberries, demonstrated that the pathway for degradation was the pyrolysis of water molecules creating –OH radicals involved in the opening of anthocyanin ring formation [49]. US-assisted extraction of various phytochemicals has grown in interest because of the potential industrial application to provide an efficient and energy saving extractive method.

**Figure 3.** Schematic of a probe-type sonication system. Adapted from Jabbar et al. [45].

198 Phytochemicals - Source of Antioxidants and Role in Disease Prevention

Pulsed light (PL) involves the use of intense, short duration pulses of light over a broad spectrum of wavelengths ranging from UV (180–380 nm), visible light (380–700 nm) to nearinfrared (700–1100 nm); mainly used for decontamination of surface microorganisms on food and packaging [50, 51]. The basic components of a PL system incorporates three main parts: a lamp (xenon gas lamp), a power supply and a pulse configuration device (controller); configured in either batch or continuous flow design depending on the food material to process (see **Figure 4**) [52]. The mechanism of PL on microbial inactivation is attributed to both photochemical and photothermal effects. UV radiation is absorbed by carbon–carbon double bonds in

**3.4. Pulsed light (PL)**

nucleic acids and proteins disrupting DNA and RNA structures, as well as rupturing bacterial cells due to localized overheating from absorption [50–52]. Similarly, the nonionizing effects of UV-C radiation at low doses has been the subject of numerous studies and documented by Maharaj et al. as having positive impacts on phytochemicals and sensory properties, either by preserving its content in fruits and vegetables or increasing it following treatment [53].

Manzocco et al. on studying the effect of PL on fresh-cut apple of increasing fluence ranges of 0, 8.8 and 17.5 J/cm2 showed a significant decrease in browning of PL treated samples attributed to the modification of metabolic respiration and controlling the formation of brown polyphenols [54]. Similar studies on the effects of PL support this theory as observed by Lopes et al. On the effects of the exposure mode of light treatment on fresh-cut mangoes. PL treatments of 1 pulse (0.7 J/ cm<sup>2</sup> ), 4 pulses (2.8 J/cm2 ) and 1 pulse for 4 days (2.8 J/cm2 ) reduced the respiration rate with positive impacts on maintenance of yellow color and lower mass loss during storage [55]. Significant improvements in firmness were most likely associated with higher levels of UV-C, which either directly suppress cell wall hydrolase activity or indirectly via increase polyamine content that inhibit the enzyme. In the same study, there were marked increases in carotenoid and ascorbic acid content at the higher fluence intensity treatments. The authors noted the increase in the biosynthesis of these compounds with antioxidant activity could be an adapted photo-protective response to increasing oxidative stresses caused by UV-radiation. Koh et al. demonstrated that PL treatment on fresh-cut cantaloupe, a nonacidic fruit, resulted in the retention of phenolic and ascorbic acid content, albeit at much lower levels when compared to other studies on acidic types [56]. The study also highlighted that at much higher fluence treatments of 11.7 and 15.6 J/cm2 there was a significant reduction in ascorbic acid content attributed to photothermal degradation of heat labile ascorbic acid at the higher intensities. At low PL dosage rates of 2 and 4 J/ cm<sup>2</sup> , Pataro et al. recorded significant increases in total carotenoids, lycopene and phenolics in whole, uncut tomatoes and Annurca apples [57]. Investigations on raspberries known to be high in antioxidant compounds showed that PL in combination with sanitizer washing was able to significantly increase the total phenolic and anthocyanin content both directly after treatment, and retain higher levels after 3 months of frozen storage compared to untreated samples [58]. Both UV light and thermal stress created by PL induce the production of phenolic compounds through increased activity of phenylalanine ammonia lyase (PAL). However, increasing the duration of treatment (20–30 s) leads to over dosage of thermal stress producing severe damages to plant tissue, discoloration of the fruit skin and loss in bioactive content.

common to both cut apples and melons, was significant improvement in a reduction in brown color formed from enzymatic degradation products. By increasing CP treatment time, an observed linear reduction was noted for PPO and POD activity. The inhibitory effect of CP on enzyme activity was attributed to chemically reactive oxygen and nitrogen species modifying

An Evaluation of the Impact of Novel Processing Technologies on the Phytochemical…

http://dx.doi.org/10.5772/intechopen.77730

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While the effects of CP on phytochemical composition is in its infant stage, Ramazzina et al. attempted to evaluate the effects of CP on bioactive compounds in minimally processed kiwifruit [67]. In the study, a significant reduction in chlorophyll and carotenoid content was observed in CP treated samples followed by better retention in these pigments during storage. This was attributed to the breakdown and oxidation of chlorophyll and carotenoids mediated by reactive species during the initial stage of treatment, followed by a slower rate of deterioration during storage due to partial protein denaturation and reduction in enzyme activity as previously described [65]. Analysis of health promoting ascorbic acid and phenolic compounds in the same study showed no significant changes in their content in the kiwifruit. While the investigators did note a slight initial decrease in total phenolic content, it did not significantly affect the overall antioxidant activity between CP and control treatments. It was noted that plasma induced oxidation of phenols at the initial stage of treatment, could be counteracted by tissue response/defense mechanisms that synthesize new phenolic compounds through increased activity of the enzyme (PAL) [67].

The recent global rise in consumer health awareness has prompted some food producers to utilize nonchemical preservation treatments to maintain and enhance the integrity of food products. Enhancing the competitiveness of the food industry requires technological innovation for improving quality, nutritious and safe ready to eat foods. Some studies have shown that unlike traditional thermal processing, nonthermal alternatives such as pulsed electric field (PEF), pulsed light (PL), ultra sound (US), high pressure processing (HPP) and cold plasma (CP) techniques have the ability to preserve and in some cases elicit increased phytochemical content of some fruits and vegetables. Such novel food preservation technologies have shown promising evidence in producing foods capable of reducing noncommunicable diseases with benefits to both domestic and export markets. In summary, the review has focused on both the application and impact of nonthermal technologies on the bioavailability of phytochemicals in fruits and vegetables which can positively impact the Food and Beverage industry.

Biosciences, Agriculture and Food Technologies (BAFT), ECIAF Campus, The University of

amino acids within the 3-D structure of proteins resulting in loss in enzyme function.

**4. Conclusion**

**Author details**

Vishal Ganessingh, Raeesah Sahibdeen and Rohanie Maharaj\*

\*Address all correspondence to: rohanie.maharaj@utt.edu.tt

Trinidad and Tobago, Trinidad & Tobago

#### **3.5. Cold plasma (CP)**

Plasma is a quasi-neutral gas state, considered the *"fourth"* state of matter, and composed of a mixture of partially ionized gas molecules, ions, atoms and free electrons in their fundamental or excited state with an overall net neutral charge [59]. Plasma can be generated by using several types of energies to excite molecules. In the food industry, the general approach of producing plasma is to subject atmospheric air to an electric or electromagnetic field of constant or alternating amplitude, to induce electron collisions and generation of the ionized species [60]. The dielectric barrier discharge (DBD) and the plasma jet (see **Figure 5**) [59] are two common design types used to breakdown gas in a stationary electric field between electrodes to create the ionizing effect. The term cold plasma (CP) is considered a nonthermal technique from the fact that the temperature of electrons (*Te* ) is much higher than the temperature of the ions, neutrals and global gas (*Tg* ) in the plasma (*Te > > Tg* ) [61]. Thus the overall temperature of CP is at ambient temperature without raising the temperature of the surrounding medium. Under Atmospheric cold plasma (ACP), several reactive oxygen species (ROS); as well as reactive nitrogen species (RNS) are formed with high lethal effects, capable of inactivating a wide range of microorganisms [62]. The nonthermal nature of CP technology, coupled with its high antimicrobial effects, has provided an alternative treatment for the decontamination of fruits and vegetables whilst minimizing deleterious quality impacts.

Misra et al. studied the effects of ACP on fresh strawberries and demonstrated significant reductions of 2.4 and 3.3 log cycles for mesophiles and surface yeast and mold respectively, with minimal impact to color and firmness between treated and control samples [63]. This is in agreement with other studies conducted on whole cherry tomatoes where CP did not induce metabolic changes that adversely affect critical quality parameters of color, firmness, pH and weight loss [61, 64]. Studies conducted by Tappi et al. on the effect of CP on fresh-cut apples and melon had variable changes on texture. Whilst apples showed a significant loss in *"crunchiness"* in texture, melons exhibited no significant differences in the cut fruit [65, 66]. However,

**Figure 5.** Schematic diagram of (A) dielectric barrier discharge; and (B) plasma jet system. Adapted from Pankaj et al. [59].

common to both cut apples and melons, was significant improvement in a reduction in brown color formed from enzymatic degradation products. By increasing CP treatment time, an observed linear reduction was noted for PPO and POD activity. The inhibitory effect of CP on enzyme activity was attributed to chemically reactive oxygen and nitrogen species modifying amino acids within the 3-D structure of proteins resulting in loss in enzyme function.

While the effects of CP on phytochemical composition is in its infant stage, Ramazzina et al. attempted to evaluate the effects of CP on bioactive compounds in minimally processed kiwifruit [67]. In the study, a significant reduction in chlorophyll and carotenoid content was observed in CP treated samples followed by better retention in these pigments during storage. This was attributed to the breakdown and oxidation of chlorophyll and carotenoids mediated by reactive species during the initial stage of treatment, followed by a slower rate of deterioration during storage due to partial protein denaturation and reduction in enzyme activity as previously described [65]. Analysis of health promoting ascorbic acid and phenolic compounds in the same study showed no significant changes in their content in the kiwifruit. While the investigators did note a slight initial decrease in total phenolic content, it did not significantly affect the overall antioxidant activity between CP and control treatments. It was noted that plasma induced oxidation of phenols at the initial stage of treatment, could be counteracted by tissue response/defense mechanisms that synthesize new phenolic compounds through increased activity of the enzyme (PAL) [67].
