36E-61 |
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L. GIL1, L. M. Cunha2, F. A. R. Oliveira3, S. Azevedo1, and M. C. Manso4. (1) Post-Harvest Research Sub-Unit, CECA-ICETA, UP, Portugal, (2) Post-Harvest Research Sub-Unit, CECA-ICETA, UP, Univ. Fernando Pessoa, Praça 9 de Abril, 349, 4249-004 Porto, Portugal, (3) Dept. of Process Engineering, Univ. College Cork, Western Rd., Cork, Ireland, (4) Post-Harvest Research Sub-Unit, CECA-ICETA, UP, University Fernando Pessoa For fresh-cut fruits and vegetables respiration plays a major role in their post-harvest life. While maintaining the quality and assuring the safety of fresh produce, temperature is the key element, as low temperatures decrease respiration rate, enzymatic and microbial activity. Therefore, a good knowledge of the effect of temperature on respiration is required. The aim of this study was to investigate the effect of temperature on the respiration rate of sliced onions exposed to ambient air, which may be useful for MAP design. The closed system methodology was applied to measure respiration rate under ambient air at 4º C, 8º C, 12º C and 16º C. Four replicates were performed for each temperature tested. 300g of sliced onions (Allium cepa L.) were stored in airtight glass containers (1.9 L) and the gas composition (%O2, %CO2) was monitored over time through a septum with a gas analyzer (Checkmate-9900, PBI Dansensor, Denmark). At the time of measurements, the jars were closed and sealed to ensure air-tightness. Experiments were continued up to 150 hours. RR (ml/kg/h) was calculated from a mass balance. The RR showed a lag phase that decreased significantly with temperature, ranging from approximately 40 hours at 16º C up to 140 hours at 4º C. An exponential increase of the RR after this period was accompanied by visual quality attributes deterioration as color alteration, exudate accumulation, weight loss and off-odor development. Average RR values for the lag phase showed an Arrhenius-like increase with temperature for both O2 and CO2. Results confirmed the importance of temperature on the product quality and shelf life.
Session 36E, Fruit & Vegetable Products: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |