An inexpensive, low maintenance, multiple controlled atmosphere system for research on perishable products

Abstract

A simple and relatively inexpensive laboratory-scale method for simultaneously producing 36 different atmospheres for controlled atmosphere experiments is described. Capillary bore glass tubing (15–50 mm long, 0.1–0.8 mm I.D.) is used to regulate gas flows, while gas compositions are varied by altering the length and I.D. of the capillaries. Improved approaches to head pressure maintenance and calculation of capillary bore and length have provided a reliable and robust system which is easy to construct and maintain. The standard system uses N2 from a membrane separator unit (typically producing 98% N2), air, and CO2 to generate a matrix of 36 atmospheres (any six O2 by six CO2 concentrations, in N2) at flow rates of up to 300 ml min−1 per channel. Humidity is controlled through selective passage of the gases through water. Pure O2 is used only when high CO2 or O2 concentrations (greater than 15%) are desired. No adjustments to the system are required during operation, and fluctuations in composition are within experimental tolerance. Running costs are low when used with an N2 separator, as only bottled CO2 is required.