Leaves were surface-sterilized in 2% sodium
hypochlorite for 1 min and then air-dried at 10 ◦C
for up to 30 min. Pak choy leaves were randomly
distributed into the required number of treatment
units. All treatments were stored in the dark at 2 ◦C,
10 ◦C or 20◦C in lots of 10 in 2 L containers for pak
choy. The containers were flushed with humidified air
at a flow rate of 15 L h−1. Excess ethylene (produced
by the plant material) in controls was absorbed using
Purafil®.
2.2. Quality assessment and color measurements
Material was monitored daily during storage at
20 ◦C, every 2–3 days at 10 ◦C and every 3 days to
weekly at 2 ◦C. Subjective assessment of quality was
determined using a general appearance (GA) scale
where 9 was the best condition and 1 was the worst
condition. When plant material reached a GA of 5.5,
it was considered to have reached the end of its shelf
life. In order to determine the reason for changes in
GA, the degree of yellowing was monitored using a
scale from 1 (no yellowing evident) to 6 (all yellow).
Rots and physiological damage were also noted using a
scale from 0 (none) to 4 (extreme). Color of leaves was
objectively measured at three points over the surface
with a chromameter (Minolta CR-300, Osaka, Japan)
concurrently with subjective assessment. Color was reported
as hue angle (H◦ = tan−1 (b/a)).
2.3. Ethylene determination
Ethylene production from individual leaves
was monitored by incubating them in heat-sealed
plastic-foil bags for up to 1 h, 3 h or 8 h at their
treatment temperature of 2 ◦C, 10 ◦C or 20◦C, respectively.
The headspace was then fully extracted
from bags using a syringe (allowing measurement
of the headspace volume) and 1mL injected into a
Shimadzu GC-8AIT gas chromatograph equipped
with a flame ionisation detector with ethylene being
detected at 120 ◦C. Ethylene was separated at 90 ◦C
in a 0.9m long by 3.5mm internal diameter glass
column packed with activated alumina mesh range
80–100. The 1mL measurement was triplicated for
each headspace sample to ensure accuracy. Results
were expressed as nanolitres ethylene per gram FW
per hour.
Leaves were surface-sterilized in 2% sodiumhypochlorite for 1 min and then air-dried at 10 ◦Cfor up to 30 min. Pak choy leaves were randomlydistributed into the required number of treatmentunits. All treatments were stored in the dark at 2 ◦C,10 ◦C or 20◦C in lots of 10 in 2 L containers for pakchoy. The containers were flushed with humidified airat a flow rate of 15 L h−1. Excess ethylene (producedby the plant material) in controls was absorbed usingPurafil®.2.2. Quality assessment and color measurementsMaterial was monitored daily during storage at20 ◦C, every 2–3 days at 10 ◦C and every 3 days toweekly at 2 ◦C. Subjective assessment of quality wasdetermined using a general appearance (GA) scalewhere 9 was the best condition and 1 was the worstcondition. When plant material reached a GA of 5.5,it was considered to have reached the end of its shelflife. In order to determine the reason for changes inGA, the degree of yellowing was monitored using ascale from 1 (no yellowing evident) to 6 (all yellow).Rots and physiological damage were also noted using ascale from 0 (none) to 4 (extreme). Color of leaves wasobjectively measured at three points over the surfacewith a chromameter (Minolta CR-300, Osaka, Japan)concurrently with subjective assessment. Color was reportedas hue angle (H◦ = tan−1 (b/a)).2.3. Ethylene determinationEthylene production from individual leaveswas monitored by incubating them in heat-sealedplastic-foil bags for up to 1 h, 3 h or 8 h at theirtreatment temperature of 2 ◦C, 10 ◦C or 20◦C, respectively.The headspace was then fully extractedfrom bags using a syringe (allowing measurementof the headspace volume) and 1mL injected into aShimadzu GC-8AIT gas chromatograph equippedwith a flame ionisation detector with ethylene beingdetected at 120 ◦C. Ethylene was separated at 90 ◦Cin a 0.9m long by 3.5mm internal diameter glasscolumn packed with activated alumina mesh range80–100. The 1mL measurement was triplicated foreach headspace sample to ensure accuracy. Resultswere expressed as nanolitres ethylene per gram FWper hour.
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