This takes place in the withering troughs. Ngorongo Tea Factory has a Total of 64 troughs. During spreading, care is taken to ensure that the leaf from the two sources does not mix. To ensure this, Directors green leaf and other out grower green leaf are separately spread in their respective troughs for product traceability purposes.
Spreading of the leaf in the individual troughs is done so as to ensure the least resistance to air flow during withering. As such, the leaf should be unmated. During withering, air is blown through the leaf to take out any surface moisture and also the inherent moisture of the leaf. The target is to reduce the moisture content of the leaf from around 80% to around 70-71%.
The main reason for doing this is to make the leaf easier to handle in subsequent processes and also to give the product some desired chemical changes that enhance the quality of the finished product. Fans are fitted onto the troughs to supply the required air for withering, and heating coils/ exchangers are added for use during cold and wet weather conditions. The leaf takes between 16 – 20 Hours in this section.
Green Leaf Reception +
In this section, leaf from the Directors farms and other out growers is received. The quality of the leaf first is checked through a visual inspection. This physical quality check involves looking at its appearance, checking for foreign materials, looking at how it was handled during transportation and also how it is loaded into the sacks and transportation vehicles. During the inspection, any foreign material found in the leaf is collected, weighed and recorded in the Green Leaf Foreign Material Monitoring Log Book with proper descriptions.
A sample is then drawn from the received consignment for a thorough leaf quality analysis. In this analysis, the leaf is broken down into its constituent components namely; 2Leaves and a bud, Soft banjhi, soft Loose Leaf, hard banjhis, hard loose leaf and stalks and pins. The first 3 categories should exceed 75% % of the total composition, for the leaf to be accepted into the factory.
The leaf that passes the quality check is then weighed and recorded in the green leaf receipt books. The leaf is then transferred to the respective withering troughs.
Rolling Section +
In the rolling section, the withered leaf is cut into smaller particles, hence referred to as dhool. Cutting up the leaf enables the juices inside the leaf to mix up and sets in motion chemical reactions which are ultimately responsible for the ‘special’ characteristics of Black Tea.
The rolling section comprises of two main types of machinery namely the rotor vane, which crushes and squeezes the leaf, expressing the juices out and preconditioning it for the next machines( Cell disruption/ Leaf maceration), the CTC machines are named after their function of ‘cutting’ tearing, and curling the leaf and they do exactly that to the leaf. These machines are responsible for the final shape and size of the product and also influence greatly the grade distribution (in particle sizes).
The leaf takes less than 5 minutes in this section.
At the end of fermentation, the product is still at around 70% moisture content. The product is sticky, difficult to handle and the enzymatic reactions mentioned earlier, are still going on.
Drying drops the moisture content of the product from 70% to around 3.0-3.2 %. The Ex-dryer product is free flowing, easy to handle and has a long keeping duration. During drying, the chemical compounds responsible for the fermentation are denatured/killed by the high temperatures and the product is effectively preserved at that state.
During drying, the dry air is supplied into the dryers through forced draught fans, the air fluidizes the dhool coming from the fermentation section and the moisture from the dhool is transferred to the air steam, which is then sucked out of the dryer by induction draught fans.
The dryers at Ngorongo have 3 stages with the following average temperatures. Zone one inlet ranges between 150 – 165 0C exhausts around 60-700 C, Zone two inlets ranges between 120 - 1400C exhaust around 75 0C. Zone three inlets between 90 - 100 0C, the exhaust is around 90 0C. These temperatures are enough to kill all the pathogenic microbes in the tea.
Cleaning & Fibre Separation +
As the name suggested, in this stage, the dried teas are separated between the fibrous teas and non fibrous teas and non fibrous tea. This separation is done in a fibre extractor locally referred to as pre-sorter. In this machine unit, poly vinyl chloride (PVC) rollers rub against a felt material. This creates electrostatic charges on the rollers. The dried tea is then passed under these charged rollers, which pick up the fibre and leave out the fibre free product.
From this stage onwards, the fibrous grades are referred to as off-grade or secondary grades, and the cleaned fibre-free product is referred to as Main Grades or primary grades.From this stage, the two distinct products are kept separate and through different processes.
Main Grades Sorting +
Main grades from the presorters are sorted into different sizes main grades. In the sorting process, the machine used to sort is locally referred to as Vibro screen (Rotex). This unit has 3 screens of different sizes. The tea is conveyed to the Vibro screen from the presorting via conveyor belt. The tea once presented into the Rotex is swirled around centrifugally and particles of different sizes are discharged from the top of the screen that they cannot go through.
Off Grade Sorting +
Like the main grades, the off-grades are sorted through the off-grade Rotex that has 4 screens. From this Rotex, we get the following two grades; BMF, FNGs, FNGS1, PF, Dust and D2
Pre-Packging Storage +
Every single grade produced by Ngorongo Factory has a dedicated storage ‘grade bin’. Transferring of the sorted grades into the grade bins is done via a system of conveyors. The system has been designed that there is no mixing of the grades whatsoever. With the intention to introduce the rain forest alliance teas, we will designate specific grade bins for the certified teas (RFA).
During packing, the grade to be packed is predetermined depending on the volume held in individual grade bins and market demand. The bin is then selected and the packing process commences.
Once the grade to be packed is determined, the bin holding the grade is selected at the control panel (all labeled). The tea is then transferred to the packing hoper via elevators which transfer the tea into the packing bags. The packing hoper is fitted with dust extractors and bar magnets to ensure a dust and iron fillings free product every time.
A packing sequence has been developed to minimize grades cross contamination. It is; D1, PD, PF1, BP1, BP, FNGs or BP, BP1, PF1, PD, D1 but in this sequence the packing system must be cleaned with compressed air thoroughly to prevent grade mixing/ contamination.
The current packing weights per bag are; BP (50Kgs), BP1 (58Kgs), PF1 (63Kgs), PD (68Kgs), D1 (72Kgs), FNG1 (54 Kgs), FNG (50Kgs) and D2 (65Kgs).
Main grades are packed in T-Paks (Paper sacks with an aluminum lining) and off grade are packed in polybags (Nylon sacks with a polythene bag on the inside).
The different grades are packed into differently numbered invoices for control purposes. A single invoice can have between 20 and 40 bags, depending on the grade and the Market. Factory door sales are sold in bulk bearing invoice numbers but Ngorongo packers uses special packages of different sizes based on the weights and both tagged and untagged tea bags.
All the packed teas are temporarily stored in the warehouse to wait for dispatch. Once we have packed a full container load, we request for transport of the teas to be taken to the auction. A container load is approximately 22,000 Kgs. Ngorongo packers’ dispatches the packed teas of various sizes in cartons to various markets daily.
Ngorongo Factory sell ≈ 80% of its tea through the Mombasa auction, ≈ 20% is sold through Ngorongo Tea Packers including teas sold locally to our staff and neighbors as factory door sales.