Ethylene as a contaminant in the industrial horticultural distribution chain : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Horticulture at Massey University, Palmerston North, New Zealand
Ethylene is a hormone, which participates in the maturation of horticultural products. High ethylene concentrations can cause the senescence of products, so ethylene management is important in the supply chain to extend postharvest shelf life. In this study, the ethylene concentration in 6 different locations was monitored in Manawatu, New Zealand. A distribution centre was found to have a higher environmental ethylene concentration than supermarkets, possibly due to the combustion engine exhausts. A room with high ethylene production products, such as apples and avocado, also had the highest ethylene concentration (3670 nL L⁻¹). For the supermarkets, 80% of the time ethylene concentrations in the chiller room was below 100 nL L⁻¹. However, more ethylene producing products were stored in the chiller room of one supermarket (B), and its 80th percentile ethylene concentration was 207 nL L⁻¹. Contrastingly, ethylene concentrations within a flower store were measured to be as low as the ambient environment. Broccoli (Brassica oleracea var. italica) is a popular vegetable with short shelf life. Ethylene can induce changes in quality of broccoli, such as yellowing. After being informed of potential ethylene concentrations in the supply chain, five continuous ethylene contamination treatments (0, 50, 100, 500, 1000 nL L⁻¹) were applied to broccoli for two weeks, in order to quantify consequent quality effects. Broccoli exposed to > 500 nL L⁻¹ was yellower than other treatments. The increase of chroma (C) and decrease of hue angle (h) and lightness (L) were faster than low ethylene concentrations (0 and 50 nL L⁻¹). However, there were no significant differences in colour degradation between 50 nL L⁻¹ and the control. The effects to broccoli exposed to 100 nL L⁻¹ ethylene treatment was intermediate between 50 and 500 nL L⁻¹. The broccoli was sensitive to > 100 nL L⁻¹ ethylene. The 80th percentile of ethylene concentration in distribution centre was greater than 100 nL L⁻¹, with the peaked measured being more than 1000 nL L⁻¹. For supermarkets, although the ethylene concentration was below 100 nL L⁻¹ in most supermarkets, the peak measurement can be higher than 100 nL L⁻¹ (even more than 300 nL L⁻¹). It took around 12 days to make difference. There is potential for broccoli to be affected by the current ethylene environment in the supply chain. Therefore, in these scenarios, there is a potential justification for ethylene management to result in improve quality delivery and extension of product storage life.