Agriculture Reference
In-Depth Information
Table 14.6.
Iceberg lettuce testing confi gurations
*
Iceberg Lettuce
Weight
14.35 lb
Recommended atmosphere
1 - 3% O
2
, minimize CO
2
to prevent browning
Respiration rate (RR) (mg CO
2
/kg · hr)
10.8 - 18.0
Storage temperature
5 ° C
Package hole size
A = 0.11 in
2
(1 × 0.375 ˝ diameter)
B = 0.20 in
2
(1 × 0.500 ˝ diameter)
*
Data provided courtesy of Apio, Inc. 2005.
and freshness for 6 weeks of storage at 2.2 °C. Control iceberg lettuce in a standard
24 head case made of corrugated cardboard (approximately 40-45 lb per box) was
stored exposed to air at 2.2 °C. Two different MAP membrane designs were evaluated
for iceberg lettuce. Design A used a polyethylene membrane with an uncovered 0.375-
in diameter hole, and design B used polyethylene with a 0.500-in diameter hole (Table
14.6 ).
The %O
2
and %CO
2
were measured in the internal atmospheres created by each
membrane using a Bridge Analyzer, Model 9001-2 or a Mocon PAC Series 360 gas
analyzer (Fig. 14.7 ).
The %O
2
in designs A and B were comparable, with design A generating a slightly
lower average %O
2
over the 6-week storage period. The control samples were exposed
to higher levels of %O
2
in the ambient atmosphere. The %CO
2
in each membrane
design was comparable.
At the end of the 6-week trial, the heads of lettuce were visually inspected by
trained quality assurance personnel for browning and spoilage as indicators of suit-
ability for consumption. Individual heads of lettuce were deemed “spoiled” if
15%
of the sample surface showed extensive browning and decay. All heads of iceberg
lettuce stored in the MAP systems retained freshness and edibility until week 6, when
some samples showed indications of decay (Fig. 14.8). In contradistinction, control
samples began showing extensive decay by Week 4, and 100% of the control samples
were “ spoiled ” and inedible by Week 5.
Results from the iceberg lettuce trial demonstrate that the shelf life is directly
related to the ambient gaseous environment in the package. An appropriate MAP
design technology lowered the %O
2
in the atmosphere and helped retain the fresh and
salubrious nature of iceberg lettuce for the extended shelf life of up to 6 weeks. Control
lettuce was exposed to considerably higher levels of O
2
in the ambient atmosphere
and decayed more readily.
≥
Bananas
A polyethylene membrane was investigated as a candidate for maintaining the quality
and freshness of bananas stored in 40-pound containers at room temperature for
15
days (Table 14.7). Control samples used no membrane. The %O
2
and %CO
2
in each
confi guration were measured as described above.
The MAP membrane produced an average of 6-7 %O
2
and of 6-10 %CO
2
. Control
banana samples were exposed to a higher %O
2
atmosphere exhibited some browning
≥
