Treatments or storage conditions that improve
gas exchange in fruits and vegetables would reduce
the gradient in gas concentration between
internal tissue and the ambient atmosphere and
would improve the overall storage life of the
commodity under CA because more of the tissue
would be exposed to the optimal concentration of
gases (Burg and Burg, 1965). Low O2 storage
atmospheres made with a preponderance of Ar,
He, or N2 have different diffusive characteristics.
Both Ar and He are monatomic gases and are
smaller in size than the diatomic gas N2. The
small 5.9% increase in the diffusivity of O2 in Ar
over N2 atmospheres (Hodgman, 1961), and the
small size of lettuce leaf pieces and broccoli florets
probably precluded any beneficial effect that
would be associated with diffusivity differences.
At high concentrations and/or under pressure, He
and N2 have an anesthetic effect in mammals and
reduce the chilling injury of sensitive plants
(Saltveit, 1993). They may be chemically inert, but
they have some physiological effects, although it
does not appear to be through modification of
enzyme activity (Gorny and Agar, 1998).