Coffee mechanical separator
The following section provides a hazard analysis of coffee processing. It describes the effects of each hazard on product quality and suggests remedial actions. In all cases, keeping processing hatches segregated ensures that any quality problems are contained within affected batches. If possible, keep fermentation and drying batches separate as well. You need to monitor the quality of all grades produced in the factory on a daily basis. By analysing batches as soon as practicable you can identify and remedy processing problems early in the season or as soon as they become apparent. By mixing contaminated and uncontaminated batches, faults in liquor quality can potentially downgrade the quality of large amounts of product. Respective grades from different processing batches should be combined only when the quality of each has been assured. This is particularly important for prime grades.
You can do your own quality assessments as long as you have developed basic sensory analysis skills. You should be able to identify acceptable batches readily. Have suspect batches re-evaluated by an objective assessor if you have any doubt about the nature or severity of the fault. In addition to commercial evaluation services, grower organisations in New South Wales and Queensland are forming taste panels to establish and maintain domestic quality standards.
Immature contamination
Immature contamination downgrades liquor quality, giving bitter, grassy, green, sour and flattened flavours and downgrades green bean appearance due to the presence of blacks and pulper-damaged bean. It also reduces capacity of conventional pulping equipment, increasing risk of damage to prime bean and increases the risk of bacterial and/or fungal attack from damaged parchment during fermentation, drying and storage.
Green coffee in stacked bags
Action for dealing with immature contamination
- Aim for less than 2.5% immature bean in the final product.
- Improve selectivity of harvesting.
- Set pulpers so that immature cherry can pass undamaged.
- Upgrade the processing system to accommodate more immature cherry.
- Extract whole immature cherry during grading operations (if possible).
Overmature contamination
Over mature contamination downgrades liquor quality, giving dirty, earthy, medicinal flavours. It also downgrades green bean appearance due to the presence of unhulled cherry and brown/stained bean. Over mature contamination increases the risk of chloroanisole contamination and the risk of drying hazards due to less uniform product.
The sorting of dry processed (overmature) mbuni cherry in Kenya
- Aim for less than 2.5% bean from overmature cherry in the final product.
- Improve the effectiveness of flotation separation in conventional systems.
- Implement size grading and aspiration.
- Extract whole overmature (mbuni) cherry during grading operations (if possible).
Underfermentation
Underfermentation prevents mucilage degrading completely so mucilage will not be completely removed during washing; washed parchment will still feel slippery. It downgrades liquor quality, giving green, fruity flavours while browning and discolouring parchment during drying. Underfermentation may result in overfermentation problems during drying if the coffee continues to ferment. It also makes dry parchment more water absorbent.
Action for dealing with underfermentation
- Use only enough water to cover parchment during wet fermentation.
- Add enzyme at recommended rates (e.g. Ultrazyme ® 100G @ five to ten grams per tonne of wet parchment).
- Agitate periodically during fermentation to ensure a good start and even fermentation.
- Speed commencement of fermentation by using warm water (avoid using cold water).
- Avoid changing water during fermentation.
- Ensure that fermentation is fully completed. (Fully fermented coffee beans feel ‘gravelly’ when clenched in the hand.)
- Use mechanical demucilaging equipment.
Overfermentation
Overfermentation downgrades liquor quality, giving foul-fruity flavours and, in extreme cases, sweaty-onion flavours. It stains parchment and can give off offensive odours during and after fermentation.
Action in dealing with overfermentation
- Reduce fermentation time.
- Monitor fermentation progress more closely.
- Add enzyme at recommended rates to enable greater control of fermentation.
- Ensure that washing is effective.
- Ensure that drying capacity is sufficient.
- Ensure that fermentation is fully completed since overfermentation (during drying) may be a symptom of underfermentation.
Parchment damage
Parchment damage predisposes product to moisture uptake and bacterial and fungal attack during storage. It also increases the number of green bean defects and downgrades appearance of green bean.
Coffee cherry pulper
Action for dealing with parchment damage
- Set pulpers so that prime bean is not nipped or cracked (by mechanical damage).
- Upgrade processing system to accommodate more immature cherry.
Pulp contamination
Pulp contamination increases risk of off-flavours during fermentation. discolours and stains parchment. makes washing after fermentation more difficult. increases the drying requirement (in extreme cases), especially when sun-drying. downgrades parchment appearance even if no quality problems are evident.
Action for dealing with pulp contamination
- Set pulpers more aggressively.
- Check that the system is not being overloaded.
- Upgrade processing equipment to improve pulp removal.
- If pulp contamination has occurred, ferment as quickly as possible to avoid quality hazards.
- Remove pulp during milling operations.
Source
Craig Lemin
