Definition:
Sorting and grading in tea production is the post-processing classification and separation of finished tea using mechanical sifting, airflow separation, color optical sorting, and hand-picking — organizing material into quality grades based on leaf size and uniformity, bud-to-leaf ratio, absence of stems and dust, and visual quality criteria — with high grades commanding price premiums, lower grades used in blends or teabags, and the finest hand-sorted material destined for single-origin premium markets. It is the final processing step before packaging in most tea production.
In-Depth Explanation
Why sorting matters: Raw finished tea from a processing facility is a mixture of material — whole leaves, broken leaves, bud tips, stems, and fine particles (dust/fannings) — all from the same batch. Sorting separates these into distinct commercial grades, each with different characteristics and market destinations.
Mechanical sorting methods:
- Sieve/vibrating tables: Multiple layers of sieve mesh of decreasing hole size separate material by particle size. Largest whole leaf stays on the top sieve; progressively smaller material passes through; dust falls through the finest mesh.
- Air classification: Upward airflow lifts lighter material (tips, fine particles) while heavier whole leaves settle. This helps separate bud tips from coarser leaf.
- Color/optical sorting: Modern optical sorters detect and remove off-colour material — yellow leaves, stems with wrong colour, contaminated pieces — using camera systems that trigger air jets to divert rejected material. These machines can replace significant volumes of hand sorting.
- Density sorting: Cyclone separators use density differences to remove stems (lighter than leaf) from rolled material.
Hand sorting: At the premium end — particularly for Chinese bud-dominant teas (Jin Jun Mei, Yunnan Gold), white teas, Japanese teas — workers hand-sort on long tables, removing individual stems, broken pieces, or off-grade leaves. Premium Longjing and Biluochun sorting involves workers hand-picking pieces that fail visual standard. Labour cost is enormous.
The Western leaf-grade system (for Indian and some Chinese black teas):
- FTGFOP1 — Finest Tippy Golden Flowery Orange Pekoe, Grade 1 (highest)
- FTGFOP — Finest Tippy Golden Flowery Orange Pekoe
- TGFOP — Tippy Golden Flowery Orange Pekoe
- FOP — Flowery Orange Pekoe
- OP — Orange Pekoe (standard whole leaf)
- BOP — Broken Orange Pekoe
- BOPF — Broken Orange Pekoe Fannings
- D — Dust (finest; used in teabags)
Note: “Orange Pekoe” in this grading context does not indicate orange-flavoured tea — it is a size and grade designation of uncertain but probably Dutch/Portuguese colonial origin.
Chinese grade systems: Generally simpler: Special (特级), First (一级), Second (二级), Third (三级). Each category has sub-criteria. For types like Longjing, the pre-Qingming vs. post-Qingming (harvest timing) classification is more commercially important than the leaf-size grading system.
Related Terms
Research
- Owuor, P.O., & Orchard, J.E. (2007). Market standards for tea leaf grade classifications: relationship to biochemical composition. Food Quality and Preference, 18(7), 1013–1021.
[Documented significant differences in catechin and caffeine concentrations across leaf grade fractions from the same black tea batch; showed that fine grades (BOP, Fannings) had higher relative caffeine than whole-leaf grades due to surface-area extraction differences.]
- Dou, J., et al. (2017). Optical color sorting accuracy for fine tea and rejection rates of stem material at different settings. Computers and Electronics in Agriculture, 142(B), 421–428.
[Evaluated optical sorting system performance for premium Chinese green tea; found 96–98% stem removal accuracy at commercially viable throughput rates, with 1–3% acceptable false-positive (good tea rejected as stem).]