Background: Strawberries are perishable fruits that decay quickly after harvest, but are valued for their distinctive taste and aroma. Melatonin is involved in plant resistance against stress, plant senescence and fruit ripening, and was shown to delay post-harvest spoilage of strawberries. Objective: The effects of melatonin postharvest treatment on shelf-life and volatile organic compound profile were assessed in strawberry fruits cv "Luca". Methods: Strawberry fruit were treated with 100 µM melatonin and stored at 4 °C for 12 days to assess whether melatonin treatment could delay spoilage without adversely affecting aroma. Results: Melatonin treatment delayed fruit deterioration by reducing weight loss and incidence of decay as well as maintaining total soluble solids, titratable acidity, anthocyanin, and taste. Melatonin treatment also significantly reduced CO2 production compared to control fruits. The relative abundance of the majority of volatile organic compounds (VOCs) was not affected, however abundance of two VOCs that are important components of strawberry aroma were affected by melatonin treatment. Conclusions: Post-harvest treatment of strawberries with 100 µM melatonin improved strawberry quality and conserved bioactive compounds after d of storage. However, components of the aroma profile were altered in a way which may affect consumer perception of quality.

Strawberries are valued for their aroma and phytochemical content. However, they have a short shelf life and storage at low temperatures to prolong shelf life affects physiological and biochemical processes in the fruit. This impacts on their use in fresh cut ready-to-eat fruit salads. To assess changes in aroma and how these are related to phytochemical content and gene expression, Fragaria x ananassa cv. Elsanta strawberries were halved and stored at either 4 °C or 8 °C for a period of 12 days. Phytochemical content was relatively unaffected whereas volatile organic compound profiles were distinct at different time points of storage. Gene expression changed significantly with storage over a 5 day period: a total of 1135 gene targets changed in expression (p < 0.05; log2 fold change >1.5) with most changes between days 0 and 5 of storage. These included genes related to stress responses, and secondary metabolism. Real time PCR was used to verify expression profiles of two genes related to VOC classes represented in the aroma, showing changes in pattern of expression during storage.

IntroductionStrawberry fruit are highly valued for their aroma which develops during ripening. However, they have a short shelf-life. Low temperature storage is routinely used to extend shelf-life for transport and storage in the supply chain, however cold storage can also affect fruit aroma. Some fruit continue to ripen during chilled storage; however, strawberries are a non-climacteric fruit and hence ripening postharvest is limited. Although most strawberry fruit is sold whole, halved fruit is also used in ready to eat fresh fruit salads which are of increasing consumer demand and pose additional challenges to fresh fruit storage.MethodsTo better understand the effects of cold storage, volatilomic and transcriptomic analyses were applied to halved Fragaria x ananassa cv. Elsanta fruit stored at 4 or 8°C for up to 12 days over two growing seasons.Results and discussionThe volatile organic compound (VOC) profile differed between 4 or 8°C on most days of storage. Major differences were detected between the two different years of harvest indicating that aroma change at harvest and during storage is highly dependent on environmental factors during growth. The major component of the aroma profile in both years was esters. Over 3000 genes changed in expression over 5 days of storage at 8°C in transcriptome analysis. Overall, phenylpropanoid metabolism, which may also affect VOCs, and starch metabolism were the most significantly affected pathways. Genes involved in autophagy were also differentially expressed. Expression of genes from 43 different transcription factor (TF) families changed in expression: mostly they were down-regulated but NAC and WRKY family genes were mainly up-regulated. Given the high ester representation amongst VOCs, the down-regulation of an alcohol acyl transferase (AAT) during storage is significant. A total of 113 differentially expressed genes were co-regulated with the AAT gene, including seven TFs. These may be potential AAT regulators.