Masters Theses

Date of Award

8-1991

Degree Type

Thesis

Degree Name

Master of Science

Major

Biosystems Engineering Technology

Major Professor

Fred D. Tompkins

Committee Members

R.N. Biswal, Luther R. Wilhelm

Abstract

As the demand for quality goods increases in new world markets, more work is being put into development of machines that yield higher quality production at increased efficiencies. Controlled or modified atmospheric packaging (CAP/MAP) is frequently used to provide an environment more suitable to retaining freshness while a food product is moving through the marketing chain. With the recent introduction of multiple gas technology into CAP/MAP. greater emphasis is being placed on the production of precise gas mixtures for placement inside the food package. While use of this technology is rapidly growing, research in equipment to proportion the gas has not kept pace. Therefore, the purpose of this study was to design an economical and efficient means for on-site custom mixing of three gasses.

To formulate the gas mixtures, which may be suitable for use in CAP/MAP, flows of oxygen, carbon dioxide, and nitrogen from three tanks into a mixing chamber were regulated by time sequencing and cycling solenoid-actuated valves. The on-off valves were driven by an industrial programmable controller. A program was developed to allow the percentages of the various gasses in the mixture to be changed on-line. Time values were set for each valve, and the controller subsequently actuated each valve accordingly.

A series of experiments were conducted to verify the percentages of the various gasses present over time in a specified mixture. Gas samples were withdrawn using a 5-ml syringe. Gas concentrations were measured using gas chromatography. The mixer achieved a consistent target mixture of 74 percent nitrogen, 14 percent carbon dioxide, and 12 percent oxygen within 5 percent accuracy, on average. The mixer was also capable of returning to production of this mixture after being set to generate a different gas mixture.

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