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After harvest, fresh blueberries deteriorate rapidly due to decay, softening and shrivelling. The evolution of their quality from harvest to market is determined by diverse physiological, physical and pathological processes. Although blueberries are classified as climacteric fruit, ethylene related ripening changes have a minor influence on their postharvest deterioration since they are fully ripe at the moment of harvest. On the other hand, pathogenic fungi associated to blueberry are able to grow across the entire postharvest chain, constituting the main factor of blueberry quality loss. Furthermore, moisture loss has an important impact on the postharvest of this commodity by causing fruit shrivel and also reducing the total saleable weight.

Postharvest softening in blueberries is a major problem for the export industry. The mechanisms for this observed softening are not completely understood. With most of the cell wall modifications occurring before harvest during the ripening process, fruit moisture loss seems to have an important role in defining the firmness changes of blueberries at postharvest. Previous experiments have reported interesting correlations between these two parameters, though no studies have been conducted to investigate this relationship. Improving the current understanding of moisture loss influences on blueberry firmness could provide useful information for the postharvest management of this product.

Temperature is the most important environmental factor affecting blueberry quality. Fresh blueberries must be stored at temperatures close to 0°C and 90-95% RH for maximum postharvest life (2 and 4 weeks for highbush and rabbiteye cultivars,

respectively). Higher temperatures accelerate blueberry and pathogen metabolism and increase the moisture loss gradient between the fruit and the ambient, leading to higher decay, softening and moisture loss at storage. However, temperatures in the range of 0-5°C have not resulted in consistent differences on blueberry quality attributes. Moreover, the range of temperature heterogeneity within refrigerated containers has been reported to be 4°C during fresh fruit shipping. As containerised sea freight is being increasingly used for blueberry exports, the question remains, if temperature heterogeneity during shipping could constitute an important variability factor affecting blueberry final quality at the market place.

Storage delays at temperatures higher than the optimum range have shown to decrease the postharvest life of blueberries during subsequent storage. The residual effect of cooling delay at storage has shown to be function of the holding period and the temperature, though its effects considering blueberry packing conditions (i.e. 10°C) have not been fully tested on decay and weight loss, nor for more than 3 weeks storage. As blueberries are pre stored at packing temperature until they reach the process line, to evaluate the incidence of this period on blueberry final quality should provide relevant information for the packing logistics.

Controlled atmosphere with 8-15% CO2 and O2 concentration above 1% is widely

used in marine exports to extend the postharvest life of fresh blueberries. The success of CA in increasing blueberry storability relies mainly on the effect of CO2 delaying

pathogen development, although some studies have reported a further decay reduction when O2 is maintained below 10%. On the other hand, either increased

CO2 concentrations or lower O2 can trigger physiological damage in blueberries

which leads to softening, off-flavours and decolouration, constituting an important risk for the export industry. However, elevated O2 concentrations (i.e. 17-18%) have

been suggested to reduce softening damage induced by high CO2. Therefore, further

evaluations of O2 influence on blueberry quality are still required to improve the use

of CA in blueberries.

Temperature management deficiencies during the postharvest chain (i.e. cooling delays, container temperature variability) could also interact with the shipping atmosphere, altering quality responses of blueberries. It has been reported that

storage temperature affects gas concentrations within blueberry tissues in modified atmosphere systems. Increased temperatures decrease CO2 and O2 solubility in

aqueous solutions, as well as accelerate the CO2 production and O2 uptake by

increasing the respiration rate. Consequently, whether temperature heterogeneity during the shipping period could alter CA effects on blueberry quality attributes remains an open question. Furthermore, that CA might modify the effects of temperature variations or cooling delays on quality responses is also a possibility which needs to be explored.

The following objectives have been defined for this study in order to address the exposed research questions:

 To investigate the relationship between moisture loss and postharvest firmness for blueberries

 To evaluate the impact of potential temperature variability within shipping containers on blueberry quality outputs

 To assess the impact of potential cooling delays at blueberry packing temperature on the quality attributes of this fruit

 To compare the effects of different O2 concentrations on main blueberry

quality indicators

 To investigate possible interactions between temperature management

deficiencies during blueberry postharvest and the storage atmosphere, in terms of blueberry final quality

These questions were investigated over a single season by using one cultivar of both highbush and rabbiteye blueberries. A single large experiment considering a full matrix of delay times, temperatures and storage atmospheres was setup, in order to address the questions related to storage condition effects on blueberry quality and their possible interactions during the postharvest chain. A second small experiment

was conducted specifically to investigate the influence of weight loss on blueberry firmness at postharvest and the possible mechanisms involved in this relationship. It is expected that the outputs of this research will contribute with useful and applicable information to improve the quality of fresh blueberries at the market place and to the further development of the blueberry export industry of the southern hemisphere.