マイクロウエットミリングと凍結噴霧乾燥による緑茶の新しい加工技術の開発

2018 Fiscal Year Annual Research Report

• Project/Area Number: 18F18087
• Research Institution: University of Tsukuba
• Principal Investigator: 北村 豊 筑波大学, 生命環境系, 教授 (20246672)
• Co-Investigator(Kenkyū-buntansha): ISLAM MD. ZOHURUL 筑波大学, 生命環境科学研究科(系), 外国人特別研究員
• Project Period (FY): 2018-10-12 – 2021-03-31
• Keywords: micro wet milling / spray dry / green tea

Outline of Annual Research Achievements

The outcome so far of the present study is that we have successfully developed a new Micro Wet Milling (MWM) system to produce green tea paste where the recycling and continuous operation can be applied. We have collected three varieties of green tea samples (Yabukita, Sayamedori, and Okumedori) from Nagasaki, Japan. The optimum milling conditions were determined based on achieving minimum particle sizes. The best wet milling conditions was set by varying the green tea to water ratio (10:90; 15:85; and 20:80 w/w), feeding rate (15 mL/min to 25 mL/min) and rotational speed (40 rpm to 50 rpm) for the preparation of Yabukita green tea paste. Feeding rate 25 mL/min, green tea to water ratio of 20:80 w/w, and rotational speed 50 rpm can able to produce paste with smaller particle sizes (58.64±2.31 µm), better color (in terms of greenness and chroma value) and nutrition properties (i.e. ascorbic acid, polyphenol, and antioxidants) than the commercial green tea powder.

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

We are proceeding the same as the plan that we proposed. As we know recent year increasing interest in its health benefits has led to the inclusion of green tea in the processing of value-added products with functional properties. But there is challenges to add green teas into the process product due to the higher particle sizes and insolubility in cold water. That’s why our plan is to develop improved MWM system for producing green tea paste with minimum particle sizes, soluble in cold water and without wastes and introduce a new product in addition to the traditional use. We have already developed a MWM system and the experiment is going on. Another plan was to design an improved and universal spray freeze-drying process to produce food powders with enriched functional compounds. But we are a little delay for executing all specific objects in the last fiscal year proposal. We will be able to carry out all the objectives during the tenure of our project.

Strategy for Future Research Activity

Continuation of the previous work will be carried out for the other green tea varieties (Sayamedori, and Okumedori). Improved MWM will also be applied to develop green tea paste and comparative study will be done. The physicochemical, nutritional and antioxidant properties of the MWM product will be assessed. Another goal is to develop a spray free-drying technique (SFD), to do this we will modify the existing commercial spray drying system. Performance of the SFD will be determined based on the product recovery, drying time and cost-benefit analysis. The effect of SFD on functional, color, nutritional, antioxidants and sensory quality of the dried product will be analyzed. The shelf life and microbial study of the green tea paste and powder from MWM and SFD will be carried out. Analysis of the data will be done by statistical software. Prepare the final report for publications and dissemination via the website, professional journals and presented in the international; conferences both in Japan and overseas.