Otro inmovilizado intangible

Cooling delays at 10°C simulating packing temperature increased the total weight loss of blueberries over the subsequent storage period. Regardless of the delay duration (i.e. 12 or 24 h), cooling delay led to 0.4% and 0.6% more total weight loss at storage than no delay in ‘Brigitta’ and ‘Maru’, respectively (Table 3-1). On the other hand, the rate of weight loss during the subsequent storage was not affected by the cooling delay times, in either cultivar (Table 3-1).

The observed residual effect of delayed cooling on the total weight loss at storage is an expected consequence of the increased moisture loss during the delay period. As moisture loss from fresh produce depends on the absolute humidity gradient between the product and the environment (Talbot and Baird, 1991), higher temperatures and longer times during the delay increase the produce weight loss during this period. Total weight loss after subsequent storage is therefore a direct consequence of the weight loss during the delay, which is simply amplified by the storage conditions. This has been previously confirmed for blueberries, where different temperature/time delay combinations have modified the total weight loss after subsequent storage, but not the weight loss rate during storage (Tetteh et al., 2004). As such, the results obtained in this study are in agreement in that total weight loss of blueberries after storage increased as delay duration increased from 0 to 12 h, without altering the rate of weight loss. However, it was also expected that 24 h delay would lead to higher weight loss than 12 h delay, although this was not observed for either cultivar. A possible explanation for this could be a progressive drying and suberisation of the stem scar as delay period was extended beyond 12 h. The stem scar is known to be one of the primary pathways for weight loss in blueberries (Perkins-Veazie et al., 1995a), and periods of 8 h at 18°C have been reported to stimulate the drying of the stem scar in blueberries (Mainland, 1995). Consequently, the rate of weight loss

during the delay period would have been reduced, resulting in non-significant differences between 12 and 24 h delay at the subsequent storage.

The results of the experiment agree with previous research evaluating the influence of cooling delays on blueberry quality, which have consistently reported increased total weight loss after subsequent storage. For example, increasing delay periods within 0-24 h range at high temperatures (30-32°C) have resulted in progressive increases of total weight loss of up to 2% after subsequent cold storage (Ferraz et al., 2001; Tetteh et al., 2004). Likewise, when delays have included intermediate temperatures, such as packing conditions (10°C), they have also led to increased total weight loss after storage (Jackson et al., 1999; Paniagua et al., 2012). However, the residual effect of delay at these temperatures has not been clear for periods shorter than 20 h. Paniagua et al. (2012) suggested higher total weight loss after storage of ‘Maru’ blueberries due to increased cooling delay times at 10°C from 4 to 20 h, although this was not confirmed. Accordingly, the weight loss data in this study confirms the residual effect of cooling delays shorter than 20 h at packing temperatures on total weight loss of blueberries after subsequent storage.

When applying these results to the blueberry industry context, the effect of cooling delay at 10°C on weight loss obtained in this experiment could imply a relevant impact of extended packing periods on blueberry quality. The difference of average weight loss between no delay and 12-24 h delay was 0.4% and 0.6% for ‘Brigitta’ and ‘Maru’, respectively. This approximately 0.5% increase in weight loss could constitute a serious risk of reaching shrivelling threshold levels (5-8%) during the export period (2-3 weeks), assuming that the additional factors along the commercial chain of blueberries which lead to increased weight loss remain. Similarly, since total weight loss higher than 2% have been correlated to blueberry softening, this potential increase of weight loss due to cooling delays could also lead to further quality reduction expressed as softening. Furthermore, a weight loss increase of 0.4-0.6% during the supply chain should mean a relevant loss of saleable weight for blueberry exporters. On the other hand, it should be considered that the particular conditions of this experiment for the delay simulation led to similar total storage weight loss between 12 h and 24 h delay, although a further increase of this parameter should be expected under commercial conditions as delay duration increases. In fact, different

studies conducted on blueberries have reported a progressive increase of total weight loss after storage when delay times have been increased (Ferraz et al., 2001; Tetteh et al., 2004). This could mean that the potential impact of delays at packing conditions on blueberry weight loss outputs could be greater than the values obtained in this experiment, especially when delay times exceed 12 h. Nevertheless, the effect of this factor could be partially minimised at the end of the packing process, where all the clamshells are normally checked and adjusted for weight. Consequently, improving packhouse logistics in order to reduce delay times at packing temperature below 12 h should effectively reduce the weight loss of blueberries, decreasing the risk of fruit shrivelling and the loss of saleable weight during the postharvest chain.