Feasibility of closed ventilation and automatic ventilation for sea freight of Proteaceae cut flower stems
Proteaceae切花莖在海運過程封閉通風和自動通風的可行性研究
Dr E.W. Hoffman
SUMMARY
Global trends aimed at advancing sea freight technology and reducing carbon emissions have led to the invention of automated reefer technologies. This development brings the challenge of having to determine product physiological limits that are vital for the implementation of automatic ventilation technology on South African produced Proteaceae cut flower stems.
A study was conducted to determine the respiration rates, lower O2 limits and CO2 toxicity tolerance limits of Proteaceae cut stems in order to assess the feasibility of using automatic ventilation (AV+) vs. conventional fixed open-air exchange (AirEx) ventilation shipping of Proteaceae cut stems. In a closed ventilation system (representing unvented conditions as is possible with AV+ technology) which contained a mixed load of Proteaceae products in 45-55 % free air, it was observed that the O2 level fell to approximay 8.5 % whilst the CO2 level rose to about 10 %, when a HarvestWatch™ dynamic controlled atmosphere (DCA) system was used for gas sampling. Using a handheld gas analyser as an alternative sampling method revealed that under these conditions O2 levels fell below 2 %, and CO2 levels rose to above 17 %. Although the O2 dropped considerably, it was still above the Lower Oxygen Limit (LOL), which ranged from 0.09-0.33 % O2, 0.08-0.41 % O2 and 0.08-0.48 % O2 for Leucadendron, Leucospermum and Protea products respectively.
At 5 ℃, the respiration rates were between 15.11-48.07 mL CO2.kg-1.h-1 for Leucadendron, 19.06-45.44 mL CO2.kg-1.h-1 for Leucospermum and 10.76-27.24 mL CO2.kg-1.h-1 for Protea. Closed ventilation, low O2 and high CO2 atmospheres generally resulted in mass loss that was lower than or comparable to AirEx. The inflorescence and leaf colour changes in Proteaceae products stored in closed ventilation, low O2 and high CO2 treatments were commercially not significant. There were no signs of low O2 and/or high CO2 damage on the stems stored under closed ventilation. The inflorescence and leaf visual quality of Proteaceae products stored in closed ventilation was generally better than that of stems stored in AirEx. Leucadendron, Leucospermum and Protea stems stored in high CO2 treatments had comparable or better quality than stems stored in AirEx. However, exposure to 15 % CO2 for 21 d reduced longevity of some products. In Leucadendron, the response to AirEx, DCA and 2 % O2 on flower head visual quality was variable and the treatments were equally effective in maintaining leaf visual quality. Flower and leaf visual quality and longevity was comparable between the AirEx and low O2 treatments in Leucospermum and Protea.
Monosaccharides plus oligosaccharides were the most abundant sugars, followed by polysaccharides, and starch was the least abundant in Leucadendron, Leucospermum and Protea stems. Differences in polysaccharide and starch content were minor, between AirEx and low O2 treatments, also between AirEx and high CO2 treatments. Lipid peroxidation was comparable between AirEx and high CO2 atmospheres. The AirEx, DCA and 2 % O2 treatments had an insignificant effect on total phenolic content of products.
Further research is recommended under commercial conditions in AV+ type reefers, where automatic ventilation should be set to maintain a minimum of 2 % O2 and maximum of 15 % CO2 concentration during long-term sea freight shipping of Proteaceae cut flowers to ensure optimum product quality throughout the cold chain for an extended vase life.
旨在推進海運技術和減少碳排放的趨勢導致了自動冷藏技術的發明。這一發展帶來了一個挑戰，即必須確定產品生理極限，這對在南非生產的Proteaceae切花莖上實施自動通風技術至關重要。
進行了一項研究，以確定 Proteaceae 切莖的呼吸速率、降低 O2 限值和 CO2 毒性耐受性限值，以評估使用自動通風 (AV+) 與 Proteaceae 切莖的常規固定露天交換 (AirEx) 通風運輸的可行性。在一個封閉的通風系統中(表示AV+技術可能采用的無通風條件)，在45-55%的游空中含有混合負載的Proteaceae產品中，觀察到O2水平下降到約8.5%，而當使用"HarvestWatc™動態受控大氣(DCA)系統進行氣體取樣時，CO2水平上升到約10%。使用手持式氣體分析儀作為替代取樣方法表明，在這些條件下，O2水平下降到2%以下，二氧化碳水平上升到17%以上。雖然O2大幅下跌，但仍高于低氧限值(LOL)，O2為0.09-0.33%，O2為0.08-0.41%，Leucadendron, Leucospermum和Protea產品分別為0.08-0.48%O2。
在5°C時，呼吸速率在15.11-48.07 mL CO2.kg-1.h-1對Leucadendron，19.06-45.44 mL CO2.kg-1.h-1為Leucospermum，10.76-27.24 mL CO2.kg-1.h-1為Protea。封閉通風、低 O2 和高 CO2 大氣通常會導致質量損失低于或與 AirEx 相當。在封閉通風、低O2和高CO2處理中儲存的Proteaceae產品中的花序和葉片顏色變化在商業上并不顯著。在封閉通風下儲存的莖上沒有低 O2 和/或高 CO2 損壞的跡象。在封閉通風中儲存的Proteaceae產品的花序和葉片視覺質量一般優于AirEx中儲存的莖。Leucadendron, Leucospermum和Protea儲存在高CO2處理中，其質量與AirEx中儲存的莖相當或更好。然而，21 d 的 15% CO2 暴露會降低某些產品的壽命。在Leucadendron中，對AirEx、DCA和2%O2對花頭視覺質量的反應是可變的，治療同樣有效地保持了葉子的視覺質量。花和葉的視覺質量和壽命是可比的AirEx和低O2處理在白細胞和普羅蒂亞。
單糖加寡糖是的糖，其次是多糖，淀粉是Leucadendron, Leucospermum 和 Protea中不豐富的。AirEx 和低 O2 處理(AirEx 和高 CO2 處理)之間的多糖和淀粉含量差異很小。脂質過氧化在AirEx和高CO2大氣之間具有可比性。AirEx、DCA 和 2% O2 處理對產品的總酚類含量影響微不足道。
建議在 AV+ 型冷藏箱的商業條件下進行進一步的研究，在 Proteaceae 切花的長期海運運輸期間，應設置自動通風，以保持至少 2% O2 和多 15% 的 CO2 濃度，以確保在整個冷鏈中實現的產品質量，延長花瓶使用壽命。
