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Value Added Utilization of Black Tea By-products using Pressurized Low Polarity Water Extraction for the Development of Bioactive Extracts

Final Report Summary - PLPWETEA (Value Added Utilization of Black Tea By-products using Pressurized Low Polarity Water Extraction for the Development of Bioactive Extracts)

The main objectives of this project were to develop a sustainable extraction process using pressurized low polarity water (PLPW, also known as subcritical, hot and superheated water) for the recovery of bioactive extracts from tea by-products and waste, focusing on tea phenolics and saponins. The specific objectives included design and construction of a PLPW extractor, development of a methodology for the characterization of tea by-products and waste, and their PLPW extracts in relation to their biological activity, optimization of the PLPW extraction conditions, and study of mass transfer during PLPW extraction to determine the mechanism that controls the extraction rate. Another main objective of this project was to facilitate integration of Dr. Özlem Güçlü Üstündag into the ERA by enabling her to build an independent research program.

A state of the art research infrastructure (the PLPW system) and the methodological foundation developed during the project have formed the cornerstones of an independent, productive and sustainable research program focusing on processing of bioactive compounds for value added utilization of food and agricultural waste using sustainable technologies, supported by national and international collaborations. A PLPW extractor was designed and built in the first phase of this project. The system design was later modified in the second phase to increase its capabilities and efficiency, based on the expertise of the research group and practical experience gained during the research work. The modified system, which is currently under construction, can be operated both in the static and dynamic mode, as an extractor or reactor, expanding the capabilities of the research group considerably.

Phenolic extracts with antioxidant and antibacterial activity were obtained using PLPW extraction of tea processing waste. Optimization of PLPW extraction of tea phenolics was instrumental in identifying the effect of process parameters (such as temperature (90-180 °C), time (10 min-120 min), flow rate (2 ml/min-8 ml/min), and sample size on extraction efficiency and performance, and bioactivity of extracts. The optimization results provided the basis for the design modifications that were carried out. The potential of by-products of tea processing as a saponin source in addition to a phenolic source, was also investigated. PLPW extraction of green tea processing waste at 90-130 °C demonstrated the selective solvent power of PLPW for catechins. While PLPW extracts contained antioxidant catechins, no saponins were extracted. This finding has important process design implications. The differences between the solvent power of PLPW water for catechins and saponins can be exploited for fractionation purposes eliminating the need for a further separation step. After the removal of catechins using PLPW extraction, remaining saponins can be extracted either by increasing the temperature of saponins (using fractional extraction) or using an alternative solvent such as 50% ethanol. The ability to obtain multiple bioactive products, catechins and saponins, will improve the feasibility of the process considerably and its commercial potential. Mass transfer modeling of PLPW fractional extraction data for EGCG (at 110-130 °C, 2-8 ml/min, 10-120 min) was carried out using a thermodynamic model, and kinetic desorption model. Both models provided a good fit for experimental data at 90-110 °C, however none of the models were adequate in describing the extraction process at 130 °C. The dominant mass transfer mechanism was further investigated by evaluating the effect of flow rate on extraction rate. The mass transfer mechanism was observed to be dependent both on flow rate and temperature. The results of mass transfer modeling together with the optimization studies will provide direction for further studies on the scale-up of the extraction process for industrial scale processing.

This project has enabled Dr. Güçlü Üstündag to develop a research framework for value added utilization of agricultural and food processing waste, which is being successfully applied by her research group (consisting of two PhD students, and a master's student) to other important products in Turkey, olive oil and pistachio, in addition to tea. Dr. Güçlü Üstündag formed a productive research collaboration with Assoc. Prof. Yesim Ekinci at Yeditepe University, which resulted in an interdisplinary research cluster on bioactive compounds, including their analysis, processing, stability and metabolism. This project has been instrumental in enabling Dr. Güçlü Üstündag to form national and international collaborations, which resulted in grant proposals, research and knowledge transfer opportunities. As a part of a national research consortium including leading institutes in the area of tea research in Turkey, Dr. Güçlü Üstündag submitted a successful grant proposal titled “Development of New Value Added Products From Tea” to the Scientific and Technological Research Council of Turkey (TÜBITAK). She also joined an interdisciplinary research consortium including partners from academia and industry in ERA to submit a COST Proposal. Further collaborations are being actively explored in Turkey, Europe and Canada to further extend research capacity of her group.

Dr. Güçlü Üstündag’s research throughout this project was presented at fifteen international conferences resulting in four oral and thirteen poster presentations, and the publication of seven proceeding papers. Two manuscripts have been submitted to peer reviewed journals, and three more are in preparation. In addition to scientific conferences and presentations, a number of strategies such as course development, teaching, industry contacts, public websites ( and social media (an instagram account, and a twitter account, and a project logo has been used to disseminate information on the research group, research infrastructure, publications, activities and news related to the project.