Guidelines for Preparing Tea Samples for Evaluation – Oolong Tea

This guidance outlines the process for preparing Oolong tea samples for sensory evaluation using the traditional Min-Nan (Southern Fujian) Oolong tea production method. Adherence to these steps ensures sample consistency and quality.

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1. Raw Material Requirements

• Harvesting Time: Collect during the spring season on sunny days between 10:00 AM and 4:00 PM.
• Leaf Standards: Pick tender shoots consisting of small to medium-sized, slightly open leaves, with one bud and 3–4 leaves.
• Control Sample: Use another Oolong tea cultivar, such as Huangdan, as a control for comparison.

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2. Processing Techniques

Follow these steps to process the samples:

2.1 Withering

Withering includes cooling, sun-drying, and a second cooling stage:

1. Cooling (First Stage):
   • Spread freshly plucked leaves thinly (10–20 cm thick) on bamboo trays or similar equipment.
2. Sun-Drying:
   • Spread the leaves 2–4 cm thick under moderate to weak sunlight (after 3:00 PM).
   • Duration: 15–30 minutes, depending on sunlight intensity.
   • Turn leaves 2–3 times to ensure even drying.
   • Indicators: Leaves lose 6–15% of their weight, the second leaf droops, the color darkens, and the gloss diminishes.
3. Cooling (Second Stage):
   • Repeat the cooling process from step 1.
   Alternative Hot-Air Withering:
   • Spread leaves 10 cm thick on bamboo trays placed over hot-air withering troughs.
   • Temperature: 35°C–40°C, turning leaves 2–3 times during the process.

2.2 Bruising and Resting (Making Green)

This stage alternates between shaking and cooling the leaves to achieve partial oxidation.

1. Conditions:
   • Conduct the process in a relatively closed room at a temperature of 22°C ± 2°C and relative humidity of 65–75%.
2. Steps:
   • Shake and cool the leaves alternately for 4–5 cycles over approximately 12 hours.
   • Use either a manual shaking method or a shaking machine.
   Shaking Duration:
   • 1st Shake: 1–2 minutes
   • 2nd Shake: 3–4 minutes
   • 3rd Shake: 7–8 minutes
   • 4th Shake: 8–10 minutes
   • 5th Shake: 5–10 minutes, depending on the degree of bruising required.
   Cooling Duration:
   • Spread leaves 2–15 cm thick on bamboo trays after each shake. Increase the thickness gradually over the cycles.
   Completion Indicators:
   • Leaves turn yellow-green with reddish spots at the edges and tips.
   • Leaves curl slightly like a spoon.
   • Grassy aroma disappears, and floral and fruity fragrances develop.

2.3 Fixation (De-enzyming)

• Leaf Quantity: 0.5 kg of bruised leaves.
• Temperature: Pan temperature of 200°C–220°C.
• Duration: Stir-fry for 3–5 minutes.
• Completion Indicators: Leaves become pliable, and stems do not break when bent.

2.4 Rolling

• While leaves are hot, roll them by hand on a bamboo mat, 20 rolls at a time, interspersed with shaking to loosen.
• Indicators: Tea juice is lightly exuded, and leaves form tight strips.

2.5 Drying and Shaping

This stage involves initial drying, shaping (bag rolling), and final drying.

1. Initial Drying:
   • Temperature: 100°C–110°C.
   • Duration: 5–8 minutes.
   • Spread leaves 2 cm thick.
2. Initial Bag Rolling:
   • Wrap the leaves in a cloth bag and knead them until tightly shaped.
3. Intermediate Drying:
   • Temperature: 80°C–90°C.
   • Duration: 5–8 minutes.
4. Final Bag Rolling:
   • Repeat bag rolling and kneading multiple times until the leaves form tight, pellet-like shapes.
   • Leave shaped leaves for 1 hour to set before loosening.
5. Final Drying:
   • Temperature: 50°C–60°C.
   • Duration: 3–4 hours.
   • Endpoint: Moisture content is reduced to 5–6%.

2.6 Cooling and Packaging

• Cool the tea to room temperature.
• Package in airtight, dry, light-proof containers.