Coffee Industrial Process_Barbara Mazzon_V1 - Coffee Extracts & Instant Coffee – Comprehensive Study Notes

Overview & Definitions

Coffee extracts encompass coffee concentrates, instant coffee, and soluble coffees.
All are produced through a sequence of complex unit operations that convert roasted, ground beans into a liquid extract and, ultimately, a dry, shelf-stable powder or granule.
Key finished products: freeze-dried instant coffee, spray-dried instant coffee, and agglomerated spray-dried coffee.

A medium-scale instant-coffee plant typically occupies 5–6 floors.
- Top floor: Roasting & grinding.
- Middle floors: Extraction → aroma recovery → clarification → concentration → drying.
- Ground/first floor: Packaging (sticks, jars, cans, etc.).
Large footprint driven by tall spray towers, freeze-drying chambers, storage silos, and extensive piping.

Purpose: create an optimal particle size distribution that maximizes surface area, minimizes channeling, and standardizes extraction kinetics.
Treated as the first critical unit operation after roasting.

Solid–liquid extraction where hot water leaches soluble solids & volatiles from roast/ground (R&G) coffee.
Key metric – Yield: \text{Yield}=\frac{\text{mass of extracted solids}}{\text{mass of R\&G coffee}}\times100\%
Controllable parameters: temperature, pressure, residence time, and flow pattern.

Low yield (≈18!\text{–}!30\%):
- Lower T (≈100!\text{–}!120^{\circ}C), lower P.
- Shorter time → fewer bitter/tannic compounds.
- Premium flavour, high sensory quality, higher cost per kg extract.
High yield (≈40!\text{–}!50\%):
- Higher T (≈180!\text{–}!195^{\circ}C), P up to 18\,\text{bar} (optimum 15\,\text{bar}).
- Longer extraction → more solids, including negative flavour notes.
- Standard taste profile, lower cost.
Producers may blend low- and high-yield extracts to tune cost versus flavour.

Granulated coffee moves downward while hot water moves upward (counter-current).
Enhances mass-transfer driving force and extraction efficiency.
Delivers a continuous stream of liquid extract from the bottom and spent grounds from the top.

Pressurised vessels; water at 100!^{\circ}\text{C}–180!^{\circ}\text{C} (occasionally \approx195!^{\circ}\text{C}).
Pressure: up to 18\,\text{bar}; optimum ≈15\,\text{bar}.
Typical yield: 30!\text{–}!50\% (green-bean basis).
Specialty beans may target 18!\text{–}!22\% to protect delicate aromas.
Allows integrated aroma recovery before depressurisation.

Goal: capture volatile compounds before thermal concentration to avoid flavour loss.
Sequence:
1. Flash evaporation – sudden P/T drop strips volatiles.
2. Condensation – volatiles cooled & collected as a concentrated aroma fraction.
3. Outputs: (a) de-aromatised coffee extract; (b) separated aroma condensate for later reincorporation.

Removes insoluble fines to improve appearance & drying efficiency.
Methods:
- Centrifugation (decanter, disc stack).
- Filtration (press filters, cartridges, depth media).
Target: clear extract ≈10\% total solids (TS).

Technology	Typical TS	Key Traits
Thermal evaporation	up to 55\%	Cheapest, high T; risk of flavour damage
Membrane (RO/NF)	≈30\% max	Mild; high CAPEX/OPEX; rarely used alone
Freeze concentration	35!\text{–}!40\%	Mild & high quality; costly but popular for premium extracts

At 1 atm: T
By manipulating P/T we can:
- Evaporate water at lower T by lowering pressure (vacuum evaporator).
- Form ice crystals below 0^{\circ}C (freeze concentration).
Both strategies concentrate solubles while mitigating flavour loss.

Concentrated extract (30–55 % TS) options:
1. Sold as a liquid ingredient (chilled, frozen, ambient-stable).
2. Fed to spray drying → fine powder or agglomerates.
3. Fed to freeze drying → porous granules.

Equipment: tall spray tower ± fluidised-bed finishing stage.
Process:
1. High-pressure nozzles (≈25!\text{–}!30\,\text{bar}) atomise extract into micron-scale droplets.
2. Counter-current hot air instantly evaporates water; exhaust exits top.
3. Dried particles fall, then may enter a fluid-bed to equalise moisture and cool.
Products:
- Fine powder – high surface area; excellent solubility.
- Agglomerated powder – larger, more uniform granules for better flow and dosing.
Pros/Cons:
- + Lowest cost per kg; high throughput.
- – Elevated thermal load; potential flavour loss; high energy consumption; requires tall building.

Key steps: foaming → pre-freeze → freeze → granulate → sublimation → packaging.
Operating points:
- Freeze at ≈-50^{\circ}C (belt freezer).
- Vacuum sublimation: P reduced, T kept below 0^{\circ}C so ice → vapour directly (no liquid phase).
Granulation: frozen slab broken into particles before trays load.
Advantages:
- Minimal heat exposure → superior aroma retention.
- Porous matrix dissolves rapidly in hot and cold water.
Limitations:
- Slow batch cycles; high capital & energy costs.

Flavour: Freeze > Spray (less thermal degradation).
Cost: Spray < Freeze (CAPEX & OPEX).
Particle structure: Freeze = porous granules; Spray = dense powder (unless agglomerated).
Dissolution: Freeze (fast in cold) > Agglomerated Spray > Fine Spray.

Coffee-oil top-spray
- Boosts aroma intensity.
- Challenges: oxidative stability, homogenous distribution, packaging barrier requirements.
Ground-coffee addition
- Wet route: micronised R&G added before freeze drying (entrapped inside matrix).
- Dry route: fine R&G blended after spray drying (surface-attached). Adds appearance cues & flavour.
Aim: differentiate premium SKUs, mimic freshly brewed cup.

Instant coffee production integrates mechanical (grinding, granulation), thermal (roasting, evaporation), separation (filtration, centrifugation), and drying (spray/freeze) operations.
Yield management is the primary lever balancing cost vs sensory quality; governed by temperature, pressure, and time.
Aroma recovery & gentle concentration technologies are vital to protect volatile flavour compounds.
Spray drying dominates for cost efficiency; freeze drying dominates premium segments.
Ongoing innovations (oil addition, ground‐coffee inclusions) aim to close the sensory gap with freshly brewed coffee.