Respiration rate and ethylene production are important fundamental
processes in plant tissues. Clearly, the rates of O2 consumption and CO2
production are important in packaged products (such as most HPP
products) since, for example, excessively low O2 concentrations will
lead to anaerobic responses and off-flavours. Thus, to select appropriate
packaging and to understand the basic mechanisms of HPP treatment
on intact plant tissues, it is important to understand the effects of HPP
on the respiration rate of the fruit. Ethylene is also important because
of its control of ripening and senescent responses in fruit tissues and
in fresh-cut products. Despite this, there is a dearth of research into
the effects of HPP treatment on respiration and ethylene production
rates of plant materials. Preliminary work by Eggleston and Tanner
(2005) showed a reduction in respiration rate of carrot sticks treated
with HPP at 600 MPa for 2 min, with a 10-fold drop in CO2 production.
The only published study on fruit responses to HPP was by Baba, Como,
Ohtsubo, Ikeda, and Lizada (1999), who showed that in whole mume
fruit, HPP could reduce both CO2 and ethylene production (reductions
by ≅2-fold and 5-fold, respectively). However, they used a maximum
pressure of only 200 MPa.