Design, fabrication, and testing of a returnable, insulated, nitrogen-refrigerated, controlled-atmosphere, shipping container for distribution of fresh red meat

Thumbnail Image
Bailey, Christopher Glen
Journal Title
Journal ISSN
Volume Title
In today's market, packaging and cutting of fresh red meat occurs at both the wholesale and retail level. Greater economies could result if the wholesaler prepared all consumer cuts centrally. Despite advantages, meat storage life is inadequate for extensive centralized distribution, however, master packaging in combination with strict temperature control ($\rm {-}1.5 \pm 0.5\sp\circ C)$ increases storage life. Although master packaging technology exists, mechanical refrigerators usually fail to maintain this temperature range. An insulated shipping and storage container was researched, designed, and tested for its suitability to distribute master packaged meat. A stainless steel rack was fitted in the container to support 36 master packages (508 x 381 x 60 mm) which were refrigerated by time-pulsed injections of liquid nitrogen (N$\sb2).$ Electric fans provided uniformity of temperature within the container. Thirty-six, saline water bags were used to simulate meat thermally and the temperatures of 20 bags were recorded. The container was tested at outside temperatures of 15, 0, and ${-}15\sp\circ$C with four fans and at 30$\sp\circ$C with two, four, and six fans. In all instances, bags cooled from an initial 10$\sp\circ$C to an equilibrium temperature within 5.5 h. Minimum equilibrium temperatures during any 8 h trial were $-$2.6, $-$2.0, and ${-}2.0\sp\circ$C for two, four, and six fans, respectively. Correspondingly, maximum temperatures were $-$0.2, $-$0.7, and ${-}0.3\sp\circ$C. Initial chilling of the product required, on average, 19 kg of N$\sb2$, while equilibrium was maintained at a N$\sb2$ consumption rate of 5.5, 4.0, 2.6, and 0.93 kg/h at outside temperatures of 30, 15, 0, and ${-}15\sp\circ$C, respectively with four fans. Usage for two and six fans was 5 and 6.3 kg/h, respectively at 30$\sp\circ$C outside temperature. For simulated power failure or the N$\sb2$-tank running dry, temperatures in the container rose 0.9 and 2.0$\sp\circ$C/h, respectively. When the door to the container was opened long enough to remove three trays, temperature was restored within 5 min. Convective heat transfer coefficients between saline water bags and circulating N$\sb2$ were in the range of 80 to 100, 115 to 135, and 140 to 155 W/(m$\sp2{\cdot}$K) for two, four, and six fans, respectively. Heat transfer to meat will be limited by conduction in master packaged meat if similar convection coefficients prevail.