2.8. Headspace gas composition
Gaseous composition in package headspacewas measured using
gas chromatograph (GC-2010 plus, Shimadzu Corporation, Japan)
equipped with split/splitless injector, molecular sieve column
(30 m length, 0.35 I.D., RT-Msieve 5A, Restek Corporation, U.S.A.)
and a TCD detector. Temperature of injection port was kept at 35 C.
Initial column temperature was kept at 30 C for 5 min, then raised
at the rate of 10 C min1 to 100 C and held at 100 C for 5 min.
Sampling was made by piercing a hypodermic needle into package
through an adhesive septum, previously stuck to the package.
0.1 ml of sample headspace was taken and injected under a split
ratio of 5. From the column used in present study concentrations of
only O2 and N2 can be evaluated. Based on observed pO2 and pN2 in
package headspace actual concentrations of O2 and CO2 (pO2 and
pCO2) were calculated using following equations:
pO2 ¼ ðObserved pO2=Observed pN2Þ 78:084 (1)
pCO2 ¼100 ½ðObserved pO2=Observed pN2Þ 78:084
þ 78:084 (2)
Analysis was done in triplicates and concentrations of gases are
expressed as their partial pressures.