NAMS 2002 Workshop - ICOM 2008

NAMS Alan S. Michaels Award – 1b
Tuesday July 15, 8:50 AM-9:15 AM, Kaua’i
A Versatile Membrane System for Bulk Storage and Shipping of Produce in
a Modified Atmosphere
S. Kirkland, University of Texas at Austin, Austin, TX, USA
R. Clarke, Landec Corporation, Menlo Park, CA, USA
D. Paul (Speaker), University of Texas at Austin, Austin, TX, USA, drp@che.utexas.edu
After harvesting, fruits and vegetables continue to respire, i.e., consuming
oxygen and giving off carbon dioxide. Such produce will retain freshness and
market value much longer if the respiration process is slowed down, e.g., by
refrigeration. Produce shelf life can be extended further by storage in an
appropriate gaseous atmosphere, e.g., oxygen and carbon dioxide composition,
within an optimal range specific to each type of produce. Modified atmosphere
packing, MAP, employs membranes to achieve the specific atmosphere needed;
commercial application of this concept is growing rapidly for small, disposable
retail packages. Membrane technology can also be used to create appropriate
atmospheres in reusable large-scale bulk containers for storage and shipping of
produce. However, this approach would be even more widely used if a versatile
system could be designed to accommodate the requirements of different types of
produce without altering the hardware, i.e., one membrane system could be used
to create different compositions of oxygen and carbon dioxide, depending on
what produce is being shipped or stored at a given time. A scheme is proposed
here that uses a selective membrane and a non-selective membrane acting in
parallel. The relative amount of gas exchange through the non-selective
membrane can be adjusted by varying the volumetric air feed rate to its upstream
surface; this will, in turn, adjust the steady state composition of the gas around
the produce. A quantitative model for this scheme and sample calculations are
presented to illustrate the concept and how to design such a system where the
atmosphere created can be set to the desired range by adjusting the air feed
rate.