This thesis focuses on diffusion channel design for broccoli storage, an important cash crop and consumer commodity in Canada. Experiments were first conducted to determine the respiration rate of broccoli in modified atmosphere conditions created by the produce metabolic activity inside closed chambers, at four different temperatures in the cold room of 3, 7, 13, and 24$ sp circ$C. The respiration rate decreased with a reduction of O$ sb2$ concentration inside the chamber. A model to predict the respiration rate of broccoli as a function of O$ sb2$ concentration at different temperatures was developed. Experiments were then carried out to determine the cross sectional area and length of diffusion channel leading to various final O$ sb2$ (steady-state) concentrations during the storage of broccoli. Combinations of cross sectional area of 0.04, 0.18, and 1.15 cm$ sp2$ and length of 0.6, 3, 7, 12, 18, and 25 cm were tested. The carbon dioxide produced through respiratory process was absorbed by placing hydrated lime inside the chambers such that the two-component molecular diffusion model by Ratti et al. (1993) could be evaluated. The length and cross sectional area of diffusion channel have a significant effect on the final level of O$ sb2$ (steady-state) concentration. The Ratti model then served as a basis for a modified model for predicting the length of diffusion channel required to obtain a given O$ sb2$ concentration as a function of the mass of stored broccoli and the cross sectional area of the diffusion channel. (Abstract shortened by UMI.)

Graduation date: 1989

No description available.

Graduation date: 2002

Advanced research in Controlled/Modified Atmosphere storage systems has shown that open channels of different lengths and cross sectional areas, connected to an air tight storage chamber, are able to maintain variable stable gas concentrations which could be near optimal concentrations for CA/MA storage of various commodities. / This study was geared towards assessing the suitability of the diffusion channels in maintaining a desired gas concentration for CA storage of spinach. Initially, the respiratory behaviour of spinach was studied in gas sealed chambers (replicated four times) stored at four different temperatures, 2$ sp circ$C, 8$ sp circ$C, 15$ sp circ$C and 23$ sp circ$C. The respiration rate of spinach was 20 mgCO$ sb2$/kg.h, 66 mgCO$ sb2$/kg.h, 163 mgCO$ sb2$/kg.h and 271 mgCO$ sb2$/kg.h for 2$ sp circ$C, 8$ sp circ$C, 15$ sp circ$C and 23$ sp circ$C, respectively. A model was developed based on principles of enzymatic kinetics which could reliably predict the respiration rate of spinach at any given storage temperature. / Two other sets of experiments were carried in a cold room set at 2$ sp circ$C. (Abstract shortened by UMI.)

The combined effect of films of various gas barrier properties, various gas packaging atmospheres (air, vacuum and gas packaging, oxygen absorbents) and storage temperatures (4 and 12$ sp circ$C) were investigated on the color stability and shelf-life of fresh beef. Meat color was described by reflectance measurements and by reading the color coordinates L* (lightness), a* (redness), b* (yellowness), C* (chroma) and h (hue angle) in the CIE-LAB system. All packaged beef was regarded as unacceptable when reflectance differences values at 630 and 580 nm i.e., due to oxymyoglobin (MbO$ sb2)$ were $ sim$30-35. Based on these standards, aerobic packaging of beef in polyvinylchloride (PVC) film had a shelf-life of $ sim$5 d and 1 d at 4 and 12$ sp circ$C respectively. Beef packaged in both low gas-moisture barrier films resulted in black discoloration after only 2 d at 4$ sp circ$C due to increased moisture loss. Longer extensions in both color and microbial shelf-life of fresh beef were possible by packaging products under modified atmospheres using high gas barrier Cryovac$ sp circler$ bags. Both vacuum packaging (VP) and vacuum skin packaging (VSP) resulted in a shelf-life of $ sim$35 d at 4$ sp circ$C. Gas packaging using high levels of CO$ sb2$ (100%) in conjunction with Ageless-SS$ sp circler$ oxygen absorbent, delayed discoloration for $ sim$42 d at 4$ sp circ$C. (Abstract shortened by UMI.)

No description available.

Black spot development or "melanosis" is a common defect in fresh shrimp which results in product being devalued and rejected by consumers. Currently, sulfiting agents are used to control melanosis in shrimp. However, with increasing regulatory and consumer concerns about the safety of sulphites as a method of melanosis control, the shrimp processing industry is actively seeking alternative methods to control melanosis on, and extend the shelf life of, fresh shrimp. One method which has the potential to fulfill both objectives is glucose oxidase (GOX)/glucose dipping solutions in conjunction with Modified Atmosphere Packaging (MAP). / Preliminary studies have shown that black spot development can be controlled for 14 days at 4$ sp circ$C in white shrimp (Pandalus occidentalis) and pink shrimp (Pandalus borealis) using GOX/glucose or GOX/glucose/ascorbic acid in conjunction with gas packaging (60% CO$ sb2$: 40% N$ sb2$). This dipping/packaging treatment also improves the physical, chemical and microbiological changes in white shrimp compared to samples dipped only in water and air packaged. This study has shown that the combined use of two or more "barriers" can be used to extend the shelf life of, and control melanosis on, fresh shrimp. This novel process of "dipping" shrimp in GOX/glucose solutions in conjunction with MAP will have a significant effect in the area of shrimp hygiene and will have the potential to minimize shrimp spoilage incurred through melanosis.

No description available.

No description available.