A.R. East

Intermittent Warming in Alleviating Chilling Injury—a Potential Technique with Commercial Constraint

Chilling injury (CI) limits the advantage of using low temperature to maintain quality of fresh produce. Interrupting low-temperature storage with one or more short warming periods is a potential strategy to prevent this problem. While in theory the intermittent warming (IW) is an ideal technique to reduce CI, optimising and applying an IW regime commercially is challenging, and therefore, research effort in the new millennium on IW has decreased. Generally, a successful IW regime is arrived at empirically, by trial and error, and what works on one cultivar or growing condition may not be as successful on another. The review reports some of the time-temperature combinations employed to reduce CI in horticultural crops and attempts to elucidate possible mechanisms by which IW reduces CI. Understanding the mechanisms involved in CI reduction may allow identification of alternative novel techniques to harness the benefits of IW without the associated industrial issues or could provide information about the physiological and biochemical basis of the CI disorder.

Combining a hybrid genetic algorithm and a heat transfer model to optimise an insulated box for use in the transport of perishables

Temperature sensitive products are often transported in non-refrigerated systems, protected from environmental temperatures by thermal insulation and the provision of a source of cold inside the package. This work presents a method for optimising the design of thermally insulated boxes for lowest cost (while ensuring that product temperatures are maintained within set limits) by combining a heat transfer model with genetic algorithm optimisation. An example optimisation problem is presented in which a temperature sensitive product is transported across the US and must be maintained between -1 and 8 degrees C. Independent optimisation operations successfully identified solutions that were very similar, though not identical, thereby providing confidence in the approach to determine optimal solutions to complex problems. The system developed provides a rapid method to optimise the design of an insulated box for minimum cost while maintaining the product in the appropriate temperature range.

Ripening delay caused by 1-MCP may increase tomato chilling sensitivity

The export of New Zealand tomatoes is restricted to Australia and Pacific Island nations and constrained by the cost and shortage of airfreight space. The industry does not have a consistent commercial solution to enable sea freight to the Asian market. A potent inhibitor of ethylene response, 1-methylcyclopropene (1-MCP) has emerged as a tool for controlling ripening and extending the shelf life of many fresh products. Knowledge of 1-MCP effects on cool-stored fresh tomatoes is limited. In the present study, mature-green and breaker tomatoes treated with 1-MCP were stored at 2.5 °C for 5 weeks. At this temperature, 1-MCP treatment enhanced Alternaria decay severity (from latent infections) and resulted in softer fruit than non-treated controls, whereas 1-MCP reduced decay from ‘ripe rots’ when fruit were ripened at 20 °C. These results suggest that the ripening delay induced by 1-MCP may increase tomato chilling sensitivity during cool storage. While 1-MCP shows promising results in extending postharvest storage life in many crops, including tomatoes, these results indicated that application of 1-MCP before cool storage is not appropriate for assisting commercial sea freight of tomatoes. Nonetheless, it may be possible to apply 1-MCP and then store tomatoes above the temperatures that cause chilling injury in order to extend storage life.

Combined effects of pre-storage 1-methylcyclopropene application and controlled atmosphere storage on ‘Unique’ feijoa quality

Extending the storage potential of feijoa would enable export to new markets. This work investigates the effect of combinations of 1-methylcyclopropene (1-MCP) and reduced oxygen atmospheres at 4 °C on feijoa quality. After harvest, feijoa were treated at 20 °C with 500 nL L−1 for 3 h or 1000 nL L−1 for 12 h of 1-MCP and air (as a control). Subsequent storage conditions at 4 °C were either: 2 kPa O2 and 0 kPa CO2; 5 kPa O2 and 0 kPa CO2; or air (as a control). Fruit were subsequently assessed fortnightly for up to 10 weeks. 1-MCP treatment was found to have no impact on delaying deterioration during storage. Reduced oxygen atmospheres delayed loss of firmness and titratable acidity during storage. However, after 4 weeks of storage, surface injury was most severe in the 2 kPa O2 treatment. Further research on extending storage life of feijoa is required.

Effects of preharvest application of aminoethoxyvinylglycine (AVG) on harvest maturity and storage life of ‘Unique’ feijoa

ABSTRACT In a previous study, feijoa harvested earlier than ‘touch-picked’ maturity appeared visually acceptable after 6 weeks of storage but had low soluble solids content (SSC) and high titratable acidity (TA). Given that feijoa display climacteric-like behaviour, manipulation of ethylene physiology prior to harvest may have the potential to alter this outcome. Subsequently, the aim of this work was to investigate the impact of preharvest aminoethoxyvinylglycine (AVG) application on feijoa quality at harvest and during subsequent storage. The experiment comprised of three preharvest AVG treatments and two harvest occasions. AVG treatment dramatically reduced preharvest fruit drop. AVG treatment at 4 weeks before current commercial harvest timing was effective in delaying maturity. AVG treatment suppressed ethylene production rates during storage. However, AVG treatment did not alter quality (firmness, SSC, TA and flesh colour) after storage. This result adds to the evidence that postharvest ripening in feijoa may be regulated independent of ethylene despite the typical climacteric increase in ethylene observed. The results also confirmed that fruit harvested early were storable for 6 weeks without exhibiting internal browning, but having a high TA and low SSC that may affect their taste acceptability.

Product allocation of greenhouse gases produced by coolstorage facilities.

This paper introduces some methodological issues that arise when assessing greenhouse gas (GHG) emissions associated with a refrigerated product where several products are stored in one refrigeration facility. These products may be in the same room, or alternatively products in different rooms (at different temperatures) may use a common refrigeration plant. Assessment of the GHG emissions associated with any one product is complicated by differences in heat load (as influenced by initial product cooling, product respiration, room insulation quality, room door usage, seasonal weather conditions and storage temperature), refrigeration system effectiveness (Coefficient of Performance) and facility usage (space utilisation) on a daily basis. A simple hypothetical example is used to compare the results obtained from three alternative allocation methods for allocating GHG emissions between different stored products: allocation by mass (tonnes), storage time (tonne.day), and on the basis of heat load calculation and refrigeration effectiveness estimation (kWh).