Linking biochemistry and genetics in celery to taste and flavour perceived by consumers: developing a more acceptable product
Lead Research Organisation:
University of Reading
Department Name: Food and Nutritional Sciences
Abstract
Celery characteristics
Celery Apium graveolens var. secalinum is popular as a fresh product due to its characteristic flavour and texture. It was originally adapted to marshy conditions, hence its tendency to produce hollow stems and petioles. Domestication of the crop has resulted in the selection of more edible varieties with reduced bitter and strong flavours. Celery is a good source of Vitamins C, K, sodium, and potassium in the diet (USDA, 2012) and has a strong protective effect against colorectal cancer (Jinfu et al., 1991). It is rich in flavonoids and phenolics (Lin et al., 2007); oxidation of the latter causes postharvest browning of cut surfaces. Key flavour compounds in celery are phthalides, and to a lesser degree the terpenes. Van Wassenhove et al (1990) found 33 compounds using GCMS that were present in all four varieties of blanching celery tested.
The aim of the project is to develop breeding lines and associated molecular markers that can give rise to a celery variety with improved postharvest performance and flavour attributes.
Project plan.
A L Tozer Ltd have 52 lines in total available to the project. We will select 30 lines that cover the diversity and grow them in controlled environment at Reading. We will determine flavour profiles of volatile compounds e.g. terpenes and phthalides using GCMS and non-volatile compounds such as phenolics and sugars using LCMS. From these data we will select 6 extreme lines = Milestone 1 (month 9).
We will conduct sensory panels to evaluate the selected extreme lines, thus validating the biochemistry against human perception = Milestone 2 (month 12).
We will start to generate mapping populations based on linked parents that represent the breadth of biochemistry and flavour perceptions. If the first crosses are made in year 1 we should be at F2 generation by year 3 = Milestone 3 (month 30).
The six extreme lines will be grown in Spain and the UK in year 2, thus testing the impact of different environments, soil types and seasons on the biochemical and sensory properties of the selections. This work will enable evaluation of the environmental impact on celery flavour = Milestone 3 (month 24).
In year three the project will examine changes in flavour and biochemistry at different plant development/field holding times, thus providing information on which lines are likely to impart seasonal and sensory stability = Milestone 4 (month 36). Consumer panels will be used to assess liking (or otherwise) of the parental celery lines.
Transcriptome sequencing of the parental generations will be used to assemble a celery genome. SNPs will be scored in the F2 population and a working map will be produced = Milestone 5 (month 40)
In year 4 the project will collaborate with G's to process celery from the parental lines and in the F2 generation of the mapping population through their commercial processing line. Postharvest quality (firmness, weight loss, browning, stem hollowing) and flavour biochemistry will be analysed and used as traits that can be mapped = Milestone 6 (month 45). These traits will give broad QTL, and possible association with transcriptome based markers that Tozer can refine and take forward beyond the life of this PhD. Even if transcriptome based markers cannot be found the project will still provide strong associations between biochemistry and desirable flavour profile, such that development of new lines based on metabolite profile will be possible.
Celery Apium graveolens var. secalinum is popular as a fresh product due to its characteristic flavour and texture. It was originally adapted to marshy conditions, hence its tendency to produce hollow stems and petioles. Domestication of the crop has resulted in the selection of more edible varieties with reduced bitter and strong flavours. Celery is a good source of Vitamins C, K, sodium, and potassium in the diet (USDA, 2012) and has a strong protective effect against colorectal cancer (Jinfu et al., 1991). It is rich in flavonoids and phenolics (Lin et al., 2007); oxidation of the latter causes postharvest browning of cut surfaces. Key flavour compounds in celery are phthalides, and to a lesser degree the terpenes. Van Wassenhove et al (1990) found 33 compounds using GCMS that were present in all four varieties of blanching celery tested.
The aim of the project is to develop breeding lines and associated molecular markers that can give rise to a celery variety with improved postharvest performance and flavour attributes.
Project plan.
A L Tozer Ltd have 52 lines in total available to the project. We will select 30 lines that cover the diversity and grow them in controlled environment at Reading. We will determine flavour profiles of volatile compounds e.g. terpenes and phthalides using GCMS and non-volatile compounds such as phenolics and sugars using LCMS. From these data we will select 6 extreme lines = Milestone 1 (month 9).
We will conduct sensory panels to evaluate the selected extreme lines, thus validating the biochemistry against human perception = Milestone 2 (month 12).
We will start to generate mapping populations based on linked parents that represent the breadth of biochemistry and flavour perceptions. If the first crosses are made in year 1 we should be at F2 generation by year 3 = Milestone 3 (month 30).
The six extreme lines will be grown in Spain and the UK in year 2, thus testing the impact of different environments, soil types and seasons on the biochemical and sensory properties of the selections. This work will enable evaluation of the environmental impact on celery flavour = Milestone 3 (month 24).
In year three the project will examine changes in flavour and biochemistry at different plant development/field holding times, thus providing information on which lines are likely to impart seasonal and sensory stability = Milestone 4 (month 36). Consumer panels will be used to assess liking (or otherwise) of the parental celery lines.
Transcriptome sequencing of the parental generations will be used to assemble a celery genome. SNPs will be scored in the F2 population and a working map will be produced = Milestone 5 (month 40)
In year 4 the project will collaborate with G's to process celery from the parental lines and in the F2 generation of the mapping population through their commercial processing line. Postharvest quality (firmness, weight loss, browning, stem hollowing) and flavour biochemistry will be analysed and used as traits that can be mapped = Milestone 6 (month 45). These traits will give broad QTL, and possible association with transcriptome based markers that Tozer can refine and take forward beyond the life of this PhD. Even if transcriptome based markers cannot be found the project will still provide strong associations between biochemistry and desirable flavour profile, such that development of new lines based on metabolite profile will be possible.
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| BB/M016579/1 | 01/10/2015 | 31/07/2021 | |||
| 1938090 | Studentship | BB/M016579/1 | 01/09/2017 | 31/07/2021 |
| Description | Although the aroma of celery has been deeply investigated, there are many gaps in the research in terms of missing information leading to huge variation in the data when collated together. Missing information in terms of cultivar used, geographical location, storage and harvest methods. Therefore, I have suggested a minimum standards for a plant aroma experiment where researchers carrying out similar investigations include these information to ensure work is repeatable and interpreted correctly. Following these standards, I have shown the impact of genotype on the influence of the aroma profile by growing the same eight genotypes across two different years. Combining data from sensory panels and aroma analysis, the genotype shows to have a significant influence on the flavour outcome. Further analysis will be completed using the same celery varieties but grown in Spain to show the influence of geographical location over the aroma profile. The key aroma compounds and how they develop across maturity have also been identified through using a combination of analytical techniques. This was completed by taking samples two weeks before maturity, at maturity and two weeks after maturity. The data shows that there is a huge shift in the aroma profile from fresh and green, to herbal and floral and then to woody with many off-odours. This data could help growers develop new variety "flavours" by proving them to aroma targets. |
| Exploitation Route | The data from this award could firstly help researchers who are looking at the aroma of plants, produce results that are repeatable and understandable for the scientific community. Providing information such as environmental information (growing, harvest and experimental), biological data (cultivar name, origin) and experimental data (extraction, quantification methods and statistical analysis) will allow for correct replication and interpretation. This could help build a repository of good quality and repeatable aroma data. Furthermore, this has provided more information about the influencers of the crop and aid in the production of more flavour stable and therefore, quality stable products. |
| Sectors | Agriculture, Food and Drink |
| URL | https://www.sciencedirect.com/science/article/abs/pii/S0308814620325358?via%3Dihub |
| Description | With the work that has been completed on sensory and flavour on celery, I have shown to fresh produce growers the importance of sensory testing and how the environment impacts the finished product. A consistent product is important to this company and the project has opened their eyes to the importance of quality checks not just in terms of appearance but on taste and flavour, through the use of inhouse and sensory panels. Regular panels are being held to check the flavour and taste quality of their product. |
| First Year Of Impact | 2019 |
| Sector | Agriculture, Food and Drink |
| Title | Investigating the impact maturation has upon flavour development of celery using GC-O and SPME GCMS |
| Description | The aim of this project is to analyse the aroma compounds of celery stalks harvested at three different maturities, with one of the harvest point being a standard commercial harvest point and other two a fortnight before and after this stage. The samples that were collected are from the same block in the field to be able to carry out technical replicates through gas chromatography olfactory (GC-O), as the extreme celery samples are genetically different. The celery has already been freeze-dried to use in this experiment. Aroma compounds will be collected from the headspace above the various celery samples using solid-phase microextraction (SPME) and desorbed into the GC injection port for either GCMS or GC-O analysis. The next step is for 3 assessors to record describe all odours detected and their retention time throughout each GC-O run, providing information on the individual compounds that make up the aroma profile for each sample. To make the analysis of the aroma profile as accurate as possible, variables that can be controlled; the assessors will assess in the same order and at the same time of day. There will be 4 extreme samples and 2 replicates of each. ANOVA followed by Tukey's HSD will be used to identify any significant differences between maturities as well as extreme lines. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2020 |
| Provided To Others? | No |
| Impact | Pre mature shows more floral and fruity smells, especially at the start of the GC-O run, compared to mature which still shows fruity floral smells but less frequent than earthy, soily odours and citrus, green, herbal smells. Post mature has more green, fruity smells at the start of the GC-O run but then we start to see more cheesy and cardboard smells as well as the green odours. Mushroom smells are present in all maturities. Volatile organic compounds will be released due to abiotic or biotic stress such as high temperature, osmotic stress, and the most common is terpenoids which are produced due to abiotic stress, and help tor educe the reactive oxygen species in the plants. VOCs can stabilise the membranes, defend against insects as well as control senescence. As expected, harvest maturity does have an impact on the flavour profile of celery, however, a line such as the extreme line 12, has good field holding capacity compared to line 22, showing a relatively stable flavour profile |