Ethylene related ripening of 'SunGold™' kiwifruit : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand. EMBARGOED until 31 January 2026.

Embargoed until 31 January 2026A key component of the success of the New Zealand kiwifruit industry is the consistent provision of high-quality produce. The projected increase in kiwifruit volumes necessitates the widening of harvest and marketing windows. Two different kiwifruit export marketing strategies are currently deployed: i) Early season fruit are delivered for immediate sale (‘KiwiStart’), ii) later season fruit have a maturity that enables extended postharvest cool storage (‘MainPack’). These marketing strategies determine harvest criteria and subsequent postharvest management practices employed in the supply cool chain. The introduction of new cultivars, e.g. ‘SunGold™’, necessitates a re-evaluation of the postharvest ripening and storage practices, tuning the requirements to the specific responses of each cultivar. Since there is minimal information on ethylene related responses for ‘SunGold™’, research to develop a fundamental understanding of these responses is crucial for optimal management and performance of the product in the market. The purpose of this PhD is to determine the effect of industry-relevant ethylene concentrations on ‘SunGold™’ quality progression (firmness and soluble solids content (SSC)). With that understanding, a semi-mechanistic model for the simultaneous description of firmness decline and soluble solids increase under dynamic temperature conditions and ethylene concentrations was developed.--Shortened abstrac

Measuring ethylene in postharvest biology research using the laser-based ETD-300 ethylene detector

Abstract Background Ability to measure ethylene is an important aspect of postharvest management, as knowledge of endogenous ethylene production is used in assessing physiological status, while response of crops to exogenous ethylene informs efforts needed to control unwanted ripening. An ethylene monitoring device with a laser-based photoacoustic detector, ETD-300, was recently developed by Sensor Sense B.V., Nijmegen, The Netherlands. In terms of performance, the ETD-300 is superior to all other current ethylene measurement devices, with a sensitivity of 0.3 nL L−1, a response time of 5 s, and an ability to monitor ethylene in real time. Although the ETD-300 is relatively easy to operate, the performance and correctness of the data obtained depends on the choice of settings, which depends on the application. Results This article provides a description of different ways in which the ETD-300 can be used in postharvest research for monitoring ethylene production and ethylene presence in an environment. We provided guidelines on selecting the appropriate method (Continuous Flow, Stop and Flow, and Sample methods), and operational curves for deciding on suitable combination of free volume, flow rates, and period for the different measurement methods. Conclusions Using these guidelines and operational curves, ETD-300 users can considerably reduce the measurement effort by limiting trial and error in establishing appropriate methodologies for their application. The guidelines also comment on accurate use of the ETD-300, as using the inappropriate settings could lead to erroneous measurements. Although these methodologies were developed primarily for postharvest application, they can be applied in other plant science research

Carotenoid stability and lipid oxidation during storage of low-fat carrot and tomato based systems

Thermally processed (F0 = 5min, process temperature 117 °C) tomato and carrot purees containing 5% olive oil were stored in the dark at 20, 30 and 40 °C for 6 months and investigated for carotenoids and lipid stability. Lipid oxidation (peroxide value and hexanal) and carotenoids (lycopene, α- and β-carotene) were analyzed and monitored during storage. Carotenoid bioaccessibility of the samples during storage was also studied. Under the storage conditions studied, the samples did not undergo significant lipid oxidation. Moreover, carotenoid bioaccessibility remained (P > 0.05) unaffected by storage. Regardless of storage temperature, carotenoids were stable with a retention of ≥98% and color (L*, a*, b* and ΔE) changes were imperceptible after 6 months. The results suggests that through formulation and careful selection of processing and storage conditions, carotenoid stability in lipid-containing fruit- and vegetable-based foods can potentially be guaranteed. This can be important to define optimal control measures to favor carotenoid stability and acceptable organoleptic properties during the storage of similar foods.publisher: Elsevier articletitle: Carotenoid stability and lipid oxidation during storage of low-fat carrot and tomato based systems journaltitle: LWT - Food Science and Technology articlelink: http://dx.doi.org/10.1016/j.lwt.2017.03.021 content_type: article copyright: © 2017 Elsevier Ltd. All rights reserved.status: publishe