Chapter 15 - Conclusions

Abstract

A leak-free, flow-through hypobaric apparatus operating at a low pressure provides a longer storage life and less commodity water loss compared to other storage systems. LP preserves plant matter that other methods do not benefit, and prevents C2H4-induced responses, low-[O2], and high-[CO2] injury, it directly inhibits bacterial and fungal growth, can vacuum-fumigate the commodity with HOCl vapor to kill molds and bacteria, and may kill surface insects. Power consumption is lower in LP intermodal containers than in CA containers, and similar to the energy utilization in the best conventional refrigerated intermodal containers. LP consumes no chemicals, leaves no residue, is environmentally safe, and the cost to ship in an LP intermodal containers is much less than by air transport. LP is a logical choice to transport any type of plant matter that is presently exported with a loss of quality by air. The discovery of unanticipated processes operating during hypobaric storage has resulted in important patentable improvements to the LP method. The minimum [O2] concentration which does not cause low-[O2] injury in LP occurs at the RQ inversion point (IP) just as it does in CA, but pervaporation and enhanced gas and vapor diffusion displace the IP to a much lower [O2] concentration at the optimal hypobaric storage pressure. Water condensation in hypobaric warehouses can be eliminated and commodity weight loss reduced to a minimum by controlling the pressure with a vacuum regulator operating at 25°C, instead of a vacuum breaker. A vacuum regulator modulates flow between the chamber and vacuum pump and reduces commodity water loss in a VacuFresh intermodal container by taking advantage of the progressive reduction in metabolic heat generation that occurs during storage. Capillary condensation in conventional nonwaxed cardboard boxes is accelerated up to 100-fold at a low pressure, releasing latent heat that increases weight loss from stored plant matter. Waterproof plastic, or recyclable Solidboard, Climaseries or GreencoatTM storage boxes prevent water condensation from occurring. If necessary a Mylar® radiation reflecting liner can be installed between a box’s inner surface and the stored commodity to reduce commodity water loss. Humidity in the redesigned VacuFresh container is computer controlled at close to saturation in response to a thermal mass flow controller and wet- and dry-bulb±0.05°C glass-tipped thermistors shielded from radiation with Mylar®.