Atmospheric cold plasma process for vegetable leaf decontamination: A feasibility study on radicchio (red chicory, Cichorium intybus L.)

TLDR: In this article, the effect of an atmospheric cold plasma apparatus (air DBD, 15kV) on the safety, antioxidant activity and quality of radicchio (red chicory, Cichorium intybus L) was investigated after 15 and 30min of treatment (in afterglow at 70mm from the discharge, at 22 °C and 60% of RH) and during storage Escherichia coli O157:H7 inoculated on radicichio leaves was significantly reduced after 15min cold plasma treatment (−135 log MPN/cm 2 )

About: This article is published in Food Control.The article was published on 2016-02-01 and is currently open access. It has received 107 citations till now. The article focuses on the topics: Cichorium.

Figures

Figure 3. Irradiance values of the emission acquired at about 20 mm from the discharge (input voltage: 19 V). Values in brackets refer to vibrational transition (vˈ→ vˈˈ).

Figure 4. Images of radicchio leaves treated for 30 min and relative control during 1 day of storage at 4°C and 90% of R.H.

Table 5. L. monocytogenes survival on the cold plasma treated radicchio leaves.

Table 3. Sensory analysis of cold plasma treated radicchio leaves stored for 3 days.

Table 2. Instrumental colour (C*) values of cold plasma treated radicchio leaves.

Table 1. Mean values of the dark red area of the radiccio.

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Atmospheric cold plasma process for vegetable leaf decontamination: a feasibility study on radicchio (red chicory, cichorium intybus l.)" ?

In this paper, the authors investigated the effects of cold plasma on quality associated characteristics of fresh vegetables and found that the reduction of the antioxidant potential of the tested food sample has to be monitored, and that the decontamination efficiency of non-thermal gas plasma treatments has been evaluated against Gramnegative bacteria, Grampositive bacteria, spores, yeasts, moulds and viruses. 

Q2. What is the way to decontaminate leafy vegetables?

Atmospheric cold plasma appears to be a promising technology for the decontamination of leafy vegetables when applied under the optimised conditions. 

Q3. What is the effect of low pressure O2 plasma on the antioxidant activity of radicchi?

In lettuce, for example, low pressure O2 plasma treatment resulted in two-fold increase in the protocatechuic acid, luteolin, and disometin (Grzegorzewski et al., 2010) as determined by HPLC where Ar plasma treatment resulted in decrease in phenolic acids such as protocatechuic acid and chlorogenic acid. 

Q4. What are the other technologies available for decontamination of radicchio leaves?

Other chemical technologies including washing with organic acids (e.g. citric and ascorbic), hydrogen peroxide and application of ozone are also available. 

Q5. What was used to acquire digitalized images of radicchio leaves?

AF-S micro, Nikkor (Nikon, Shinjuku, Japan) was used to acquire digitalized images of radicchio leaves (exposition time ½ sec; F-stop f/16) placed inside a black box under controlled lighting condition. 

Q6. What are the alternatives to heat therapy?

On the other hand, physical non thermal technologies such as irradiation, ultraviolet light, pulsed light, high pressure processing, and ultrasound are considered more promising alternatives. 

Q7. How many microliters of a cellular suspension of an OD 0.08-0.1?

One hundred microliters of a cellular suspension of an OD 0.08-0.1 at 625 nm of the L. monocytogenes cocktail in physiological saline (NaCl 0.9%) were spotted on the surface of the radicchio samples (4 x 4 cm). 

Q8. What are the main factors that affect the efficiency of cold plasma?

cold plasma efficiency also depends on biological parameters such as the type of substrate and microorganism characteristics (type, load, physiological state) (Moreau et al., 2008; Misra et al., 2011; Stratakos & Koidis, 2015). 

Q9. How many different radicchio samples were presented to assessors?

A total of 6 different samples were presented to assessors (four cold plasma treated samples for both treatment times and two respective controls) at 0, 1 and 3 days of storage. 

Q10. How long did the radicchio leaf stay in the water?

After each treatment (15 and 30 min) and after 3 days of storage at 4°C and 90% RH, each radicchio leaf was transferred into 160 mL of Buffer Peptone Water (BPW; Thermo Fisher, Milan, Italy) and homogenised by a Stomacher® (Seward, UK) for 2 min at normal speed. 

Q11. How many surviving cells were observed after treatment?

a significant reduction in the number of E. coli surviving cells was observed (-1.35 log MPN /cm2, passing from 6.32 (CI95% 5.35-4.64) to 4.97 (CI95% 4.25-5.62) log MPN /cm 2), for the 15 min treatment. 

Q12. What was the effect of cold plasma on radicchio leaves?

The treatment applied was able to significantly reduce but not eliminate the bacterial pathogens inoculated on the surface of radicchio leaves. 

Q13. What is the effect of the treatment on the quality of the leaves?

In relation to the possible effects caused by the interaction of reactive species with the product, the treatments appeared to negatively affect the quality of the leaves during storage. 

Q14. What is the effect of cold plasma on antioxidant activity of radicchio leaves?

Although in this study plasma treatment did not appear to negatively affect the antioxidant activity of the radicchio leaves, further mechanistic studies need to be conducted in order to understand the interactions between plasma and the antioxidant components.