## 4 Current Analytical Techniques
Finally, in terms of inoculating strawberry fruit with _E. coli_ O157-H7 did not detect amounts of indole in headspace vapor samples, showing that strawberries absorbed relatively large quantities of indole and other bacterial volatile compounds from the vapor phase. The behavior observed in the strawberry showed that the absorbed VOCs contribute to controlling microbial growth and consequently act as a technological alternative to antagonist microorganisms. Another technology is e-nose sensors, which mimic human olfactory perception. These electronic sensors can detect the VOCs in a sample. They incorporate an information-processing unit, pattern recognition software, and reference library databases. The resultant electronic fingerprints express a unique aroma that helps detect odor profiles without separating the mixture into its components [52]. [PERSON] et al. [53] used the e-nose technique (EOS507C equipment) to distinguish between in vitro apple plants infected by bacteria (_Erwinia amylorona_, _Pseudomonas syringae_ pv. syringae, and mock) after 0, 2, and 8 days of storage. Only the samples infected by _P. syringae_ on day 8 differed from the remaining samples in terms of odor profiling, even on dormant, asymptomatic material in real \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Analytical Technique** & **Microorganism** & **Result** & **Reference** \\ \hline \multirow{6}{*}{Selected ion flow tube mass spectrometry (SIFT-MS).} & \multirow{6}{*}{_Botrytis cinerea_} & SIFT-MS was used to detect 1-octen-3-ol in strawberries, which was reported as a biomarker of fungi growth. Mainly alcohols, aldehydes, and terpenes associated with the ions H3O\({}^{+}\) 071, H3O\({}^{+}\) 111, H3O\({}^{+}\) 113, NO\({}^{+}\) 063, NO\({}^{+}\) 111, NO\({}^{+}\) 127, NO\({}^{+}\) 141, O2\({}^{+}\) 057, O2\({}^{+}\) 084, and O2\({}^{+}\) 093 were identified. & Ethyl btanoate, ethyl hexanoate, isobutyl butyrate, benzyl benzoate, ethyl benzoate, phenyl ethyl alcohol, and styrene accounted for 93\% of the total VOCs when the fruit was severely affected by soft rot disease in kiwifruit. [48] \\ \cline{1-1}  & E-nose and HS-SPME/GC-MS. & _Botryosphaeria dothidea_ and _Dothorella gregaria_. & \\ \cline{1-1}  & & DVB/CAR/PDMS fiber was used for extracting, and the combination of e-nose and GC-MS was feasible for the discrimination of intact and diseased kivirus. & \\ \cline{1-1}  & & Ethyl acetate, 2,3-butanediol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, phenol, 6-methyl-5-hepten-2-one, benzyl alcohol, p-cresol, 2-nonanone, and phenyl ethyl alcohol were detected in watermelon & [49] \\ \cline{1-1} GC-MS & _Acidovorax citruli_ & & \\ \cline{1-1}  & & fruit. The sample was recovered after 10 d of inoculation with _A. citruli_ bacteria. VOCs were extracted by headspace-solid phase microextraction (HS-SPME) & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._conditions. In addition, postharvest sapota contamination by foodborne pathogens has been evaluated by [PERSON] et al. [PERSON] et al. (2018). After analyzing the data, the authors found that the e-nose can separate fresh sapota from contaminated samples and determine the levels of deterioration. It showed that fruits stored on days 1 and 2 displayed fresh sapota, while days 3, 4, and 5 showed half-contaminated sapota, with completely contaminated sapota on day 6. Finally, proton transfer reaction mass spectrometry (PTR-MS) is an alternative method to GC-MS. It is based on soft chemical ionization through proton transfer reactions. Protonated water generation occurs from pure water's ion source (a hollow cathode). The reactions are observed in a drift tube operated at low pressure (c.a. 2 mbar) between H\({}_{3}\)O\({}^{+}\) primary ion and VOCs fed directly and continuously into the drift tube from the gas sample. The VOCs with proton affinity higher than water (691 kJ/mol) are protonated, while the components of air (N\({}_{2}\), O\({}_{2}\), and CO\({}_{2}\)) are not because of their lower proton affinity, thus allowing the use of air as a carrier gas [PERSON] et al.