Application of Modified Atmosphere Packaging on Quality of Selected Vegetables: A Review - Application of Modified Atmosphere Packaging on Quality of Selected Vegetables - page 36

Romaine lettuce was stored either under AMAP or under PMAP (a fi lm with
507 mL 25 m/m 2 day atm. was used) and at dark, light and a photoperiod consist-

ing of 12 h of light and 12 h of darkness for 3 days at 4 °C plus 7 days at 7 °C. A
steady-state atmosphere of low pO 2 (0.2-0.5) led to better overall quality, preven-
tion of browning, off-colors and off-odors. All sensory attributes were negatively
affected by light exposure compared to darkness, mainly because of excessive
browning effect, due to increased headspace pO 2 (Martinez-Sanchez et al. 2011 ).
Romaine lettuce samples were inoculated with strains of E. coli O157 : H7 , L.
monocytogenes and Salmonella choleraesuis and subsequently stored under passive
MAP (PMAP) [fi lms with 3,500 (fi lm 1) and 1,100 (fi lm 2) mL/m 2 day atm. OTR
were used] at 5 and 25 °C for 10 and 3 days, respectively. The storage at 5 °C led to
a 1 log decrease of both Salmonella and E. coli populations while Listeria increased
by 1 log. The increase of pathogens at higher temperatures varied between 2.44 and
4.19 log CFU/g (Oliveira et al. 2010 ).
MAs passively developed in the selected packages [mono-oriented PP fi lm
(MOPP), PE trays overwrapped with a multilayer PO or PVC fi lm] and dipping in
an ascorbic acid (0.3 %) and citric acid (0.3 %) solution at the storage temperature
of 4 °C, were studied by Pirovani et al ( 1998 ). No substantial changes in psychro-
trophic and mesophilic aerobic microbial populations were reported. Lettuce stored
in OPP retained better sensory characteristics than products stored in other fi lms.
Inoculation of E. coli O157: H7 strains and subsequent storage under MAP A
(2 % O 2 -98 % N 2 and a fi lm with OTR 110 mL/m 2 cm 3 day), MAP B (the same fi lm
with 40 microperforations) at 4 and 15 °C (for the lettuce inoculated with 5.58 and
3.98 log CFU/g E. coli O157 : H7 respectively) for 10 days resulted in decrease of E.
coli populations on lettuce at 4 °C under all treatments, but especially under MAP
B. Temperature elevation led to a considerable increase in E. coli numbers with
MAP B displaying the smallest increase (2.5 log CFU/g) (Sharma et al. 2011 ).
Low storage atmospheres tend to affect L. monocytogenes with a descending
growth rate as the temperature reduced. Listeria strains are prohibited from growing
by low oxygen and high carbon dioxide conditions. Since L. Innocua and
L. Monocytogenes have the same growth patterns, their co-existence may have
affected both their growth rate negatively (Fig. 1.3 ).

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1.7.3.2 Rocket

Rocket leaves were stored either alone or with the addition of lettuce ' Lollo verde '
leaves under MAP (5 % O 2 /10 % CO 2 for MAP A and 2 % O 2 /5 % CO 2 for MAP B)
at 5 ± 1 °C for 10 days. Mesophiles were signifi cantly reduced by both atmosphere
modifi cations 0.7 to 1 log CFU/g reduction, while psychrotrophs were also affected
by the initial CO 2 (0.7 log CFU reduction at the end of storage). The use of MAP A
led to a shelf life extension of 4 days for mixed rocket and lettuce samples remain-
ing acceptable for the whole 10-day period (Arvanitoyannis et al. 2011a , b ).
Addition of “ Aceto balsamico di Modena ” wine vinegar and extra virgin olive