Plant metabolomics for increased knowledge on the behaviour of phytochemicals in fruits and vegetables (209755)

The main objective of the project was to establish and use a analytical platform based on liquid chromatography with mass spectrometry for metabolomics studies with focus on health-related compounds in vegetables, fruits and berries (F&V). This is technology increasingly established and used by international research groups to study different issues involving metabolic changes in food plants. The subgoals were to: 1. Establish exact mass Quadrupole Time-of-Flight (Q-TOF) LC/MS -based metabolomics methodology, 2. Investigate the effects of preharvest and postharvest conditions (light and temperature) on phytochemicals in F&V using a metabolomics approach, 3. Investigate the effects of processing on phytochemicals in F&V using a metabolomics approach The main focus has been on the establishment of a UHPLC-MS based metabolomics platform for primary and secondary plant metabolites, and the data analysis methodology for the enormous amounts of data generated from metabolomics analysis. Our aim to acquire skills, expertise and establish liquid chromatography / mass spectrometry (LC-MS) based metabolomics methodology is achieved in the project. Metabolomics methodology was further applied to problems where plant materials were collected from already conducted studies, or studies ongoing in other projects. It has been conducted both "Metabolomic fingerprinting" (comparative analyzes without quantification and identification) and "Metabolomic profiling" (quantification and identification of all or a selection of metabolites), where identification of metabolites which have the greatest significance for differences between samples have been an extensive part in order to interpret and gain new knowledge. The results of the various applications that were conducted showed that metabolomics methodology was well suited to the study preharvest-, postharvest- and processing effects. The samples were from the collaborative projects "Effect of northern climate and post-harvest conditions on health-related properties of selected Brassica vegetables in Norway" (Pr.nr 185017) and strategic program "Phytochemicals" (Pr no. 224892). Results from metabolomics analyses of the preharvest study showed differences between four different European growing locations based on the variation in the type and quantity of plant metabolites. Broccoli grown at two different warm climates had distinctly different metabolite profile and these were in turn different from broccoli grown at three cold growing conditions. Of approximately 40,000 compounds detected in the samples, about 400 different plant compounds contributed strongest to the grouping of broccoli, i.e. these compounds changed concentration by a factor of 2 or more, from different growing conditions. About 130 of these have been identified so far and the plant compounds groups include hydroxycinnamic acid- glycosides, flavonoid-glycosides and tripeptides, compounds that are both health-related and could be related to taste. Metabolomics were used on samples from a postharvest study on storage of broccoli under different light and temperature conditions. It was found that about 850 unique compounds contributed to separate broccoli into different groups according to their storage conditions. Broccoli showed a clear change in phytochemical content with prolonged storage in the dark. A prominent change in phytochemicals occurred also with elevated temperature. Visible light affected the quality somewhat, but the temperature had a greater effect on the content of plant substances. A supplementation with UVB light increased the content of several health-related metabolites, such as hydroxycinnamic acids and flavonol glucosides. By using metabolomics we could reveal that hundreds of plant substances in broccoli were affected by storage conditions. This clearly shows that vegetables have an ongoing metabolism that affect both primary and secondary plant substances, many of them linked to their health-related quality. The content of plant compounds will be affected by different processing conditions, and metabolomics methodology was used to determine which metabolites that were affected by various treatments such as blanching, freezing, thawing, sous-vide heat treatment in steam, cooking in water, storage and re-heating combined with warm-holding, compared with raw materials, where curly kale was used as a model vegetable. A clear difference between sous-vide heat treatment and traditional cooking methods was found. Re-heating changed the plant metabolite profiles further, and warm-holding, which is common in the catering, influenced the content even more. The applications of the metabolomics showed that this methodology is promising and will be useful as a generic analysis tools to study complex metabolic relationships to gain new knowledge about plant food ingredients that could be influenced through the value chain.

Health and sensory related quality of vegetables and fruits, including berries (F&V) is mainly determined by the phytochemicals, including both nutrients and secondary plant metabolites, present in the plant food. The content of these metabolites is, in a ddition to genetic background, greatly influenced by growth conditions, postharvest factors and processing, and their concentration and composition may be decisive for several food plant quality traits, such as flavour, odour, colour, shelf life and healt h value. Up to now, the main focus has usually been to study selected phytochemicals identified as important for sensory and health related quality of F&V. However, in the last few years, development of novel analytical technology combined with available plant metabolite data bases and advanced data analysis has made high-throughput metabolomics analysis for simultaneous measurement of a wide range of phytochemicals in F&V feasible. Metabolomics aim to measure all metabolites or as many compounds as possi ble in a sample, and is now accepted internationally as a useful means both in plant science as well in medical and nutritional sciences. The establishment of metabolomics at Nofima Mat AS is strategically important for future research in the area of F&V. This project will focus on the metabolomics establishment, but will also, with the use of plant materials from on-going funded projects, investigate the effects of preharvest and postharvest conditions (light and temperature) and processing on the behavi our of phytochemicals in Brassica vegetables and different cultivars of strawberry and raspberry using a metabolomics approach.