# Freshness Monitoring of Packaged Vegetables
## 3 Factors Indicating the Freshness of Packaged Vegetables
### Pathogens  
Post-harvest handling of leafy greens such as lettuce and spinach has been of concern due to the possibility of contamination with different pathogens. Their presence usually indicates the contamination of vegetables with fecal material and poor sanitation. Many illnesses and deaths reported over the years were related to food contamination [31; 32; 33]. Thus, legal limits were set for the allowed count of these microorganisms inside a food packaged to ensure its safety. A summary of the most common pathogens in vegetables with their unsatisfactory limits are shown in Table 1.  
One of the most common microorganisms found in vegetables is _Escherichia coli (E. coli)_. Most _E. coli_ strains are usually harmless if within the acceptable limits that differs between countries. One study was done in 2007 on 100 samples of bags with tag \"ready to eat\" of spinach and lettuce from around the world that tested for _E. coli_ presence using the FDA Bacteriological Analytical Manual methods. The number of these bacteria were then counted with the use of Coli Complete disc which is the association of official analytical chemists (AOAC) official method [35; 36; 37]. The results showed that bagged leafy greens have generic _E. coli_ in the range of 4 to 7 log\({}_{10}\) CFU/g, which is considered a controversial limit in many countries, and satisfactory in others as not all countries have a limit set for generic _E. coli_ count. However, there is a specific strain of _E. coli_ that should not be detected in any raw vegetables or ready to eat food, known as _E. coli (O157:H7)_ that was identified as the reason for dangerous illness and led, in severe cases, to 33 deaths in USA only between 2003 and 2012 [38]. Several outbreaks linked to it were reported over the years. In 2019, the FDA and CDA announced \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Pathogen** & **Unsatisfactory Limits (CFU/g)** & **Incubation Period** & **Symptons** & **Illness** & **Ref.** \\ \hline _Escherichia coli_ & \(\geq\)100 & 2–4 days & Stomach pain, diarrhea, nausea, chills, fever, and headache & Hemorrhagic colitis & [31; 32; 33] \\ _Escherichia Coli_ & \(>\) 0 & 3–4 days & Severe stomach ramps, diarrhea, vomit, fever & Hemorrhagic colitis & [31; 32; 33] \\ _O157:H7_ & \(>\) 0 & 12 to 24 h & Stomach pain, diarrhea, nausea, chills, fever, and headache & Salmonellosis & [31; 32] \\ \multirow{2}{*}{_Salmonella spp._} & \(>\) 10\({}^{8}\) or 10\({}^{2}\)–10\({}^{3}\) & 2 days to 3 & Fever, chills, headache, backache, sometimes abdominal pain and diarrhea & Listeriosi & [31; 32; 34] \\  & for susceptible people & & & & \\ \multirow{2}{*}{_L. mono-cytogenes_} & \multirow{2}{*}{\(>\) 0} & \multirow{2}{*}{12–50 h} & Abdominal pain, cramps, fever, vomiting, and diarrhea containing blood and mucus & Shigellosi & [31; 32] \\  & & & & & \\ \multirow{2}{*}{_Shigella spp._} & \multirow{2}{*}{\(>\) 0} & \multirow{2}{*}{12–50 h} & Diarrhea, abdominal camps, nausea, and vomiting & _Bacillus cereus_ & [31; 32; 33] \\ \multirow{2}{*}{_Bacillus cereus_} & \multirow{2}{*}{\(\geq\)10\({}^{4}\)} & \multirow{2}{*}{30 min to 15 h} & \multirow{2}{*}{30 min to 15 h} & \multirow{2}{*}{_Bacillus cereus_} & [31; 32; 33] \\  & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Pathogens in vegetables responsible for foodborne illness. the outbreak of _E. coli_ related to Romaine lettuce consumption [39; 40]. Thus, the presence of _E. coli (O157:H7)_ should be absent from any ready to eat food. In addition to _E. coli_, other pathogens such as _Listeria_, _Salmonella_ spp., and _Shigella_ spp. that are found in fresh-cut vegetables and salad bags can cause illness and may also lead to death. For example, _Salmonella_ accounts to 47% of foodborne diseases in Brazil in 2010 [41]. Between 1988 and 2007, the contribution of these pathogens in the foodborne outbreaks related to vegetables and fruits was reported internationally as follows: _E. coli_ 19.5%, _L. monocytogenes_ 1.9%, _Salmonella_ spp. 7.2%, _Shigella_ spp.