The doctoral dissertation in the field of Chemistry will be examined at the Faculty of Science, Forestry and Technology, Joensuu campus.
What is the topic of your doctoral research? Why is it important to study the topic?
This doctoral research focuses on the valorization of agricultural waste, specifically citrus fruit peels, and berry pomaces. The study involved producing essential oils or solvent extracts from these abundant agricultural residues and comprehensively profiling their chemical compositions using advanced ultrahigh-resolution mass spectrometry.
Identifying bioactive compounds such as polyphenols and terpenes in waste materials enables their use in high-value products. This approach supports sustainable development and circular bioeconomy goals by reducing environmental impact while recovering functional ingredients for the food, cosmetic, and pharmaceutical industries.
What are the key findings or observations of your doctoral research?
Over 200 distinct compounds were identified in citrus peel oils, including over 100 that have not been previously reported. In the second part, polyphenol extractions from black currant pomace were optimized: 50% aqueous ethanol provided the highest extraction efficiency. Also, more than 100 individual compounds were identified. The third part focused on Finnish wild and cultivated berry pomaces. A key finding was that bilberry and lingonberry pomaces contain significantly higher levels of phenolic compounds than cultivated varieties. More than 300 individual compounds were identified. The results also showed that berry pomaces exhibit distinct metabolic profiles.
This study represents the first application of ultrahigh-resolution mass spectrometry for the systematic metabolomic profiling of pomace extracts from wild and cultivated Finnish berries. This approach generated a large volume of molecular-level data, providing essential insights for the further valorization of berry pomaces.
How can the results of your doctoral research be utilised in practice?
The comprehensive chemical profiles of natural extracts enable industries to incorporate them into functional foods, nutraceuticals, and cosmetic products. For example, citrus peel essential oils, rich in limonene and other monoterpenes, can be used in eco-friendly cleaning agents, fragrances, and cosmetic formulations due to their aromatic and antibacterial properties. The high levels of anthocyanins and flavonols identified in blackcurrant pomace highlight its potential as a natural colorant and antioxidant ingredient for the food industry.
Likewise, the hydroxycinnamic acids found in lingonberry and bilberry pomaces support their use as natural preservatives. In addition, the optimized green extraction protocols developed in this study provide scalable strategies for maximizing bioactive compound yields in industrial applications.
What are the key research methods and materials used in your doctoral research?
This research examined two types of agricultural waste streams: citrus peels from five different fruit varieties and pomaces from twelve cultivated and wild berry species, obtained from a berry farm, a local marketplace, or directly from the forest. Hydrodistillation was used to recover essential oils from citrus peels, while conventional solvent extraction (maceration) was applied to process the berry pomaces. The core analytical technique was direct-infusion ultrahigh-resolution mass spectrometry, which enabled rapid chemical fingerprinting of all samples.
In addition, gas chromatography–mass spectrometry was used to characterize the volatile constituents of the citrus peel essential oils. Multivariate statistical tools, including principal component analysis and hierarchical clustering, were employed to visualize and differentiate the chemical diversity among the analyzed samples.
The doctoral dissertation of Jie Guo, MSc, entitled Production and ultrahigh-resolution mass spectrometric profiling of essential oils and solvent extracts from agricultural waste: Valorization of fruit peels and berry pomaces will be examined at the Faculty of Science, Forestry and Technology, Joensuu campus. The opponent will be Professor Petr Novák, Charles University, Czech Republic, and the custos will be Professor Janne Jänis, University of Eastern Finland. Language of the public defence is English.
For more information, please contact:
Jie Guo, [email protected], tel. 041 368 5215
