Harvest & Drying

Harvest and drying: where the value of a batch is decided

Harvest and drying equipment weighs more on final quality than any stage of growing: between cutting and filling the container, a batch loses water, volatile compounds and material.

This section covers the four post-cultivation operations — harvest, trimming, drying and curing — for hops, perfume, aromatic and medicinal plants, hemp of approved varieties and ornamental dried flowers.

An hourly throughput means nothing without the material state

A capacity in kg/h means nothing until you know whether it refers to fresh or dried material: on the same harvest, the mass ratio between the two states is of the order of 4 or 5 to 1. A machine quoted at 20 kg/h wet and another at 5 kg/h dry may absorb the same area in a day. Insist on the words “fresh” or “dry”, and on the finish at which that throughput was measured.

Drying is a water balance, not a thermostat setting

Drying means removing a known mass of water in a chosen time. A 100 kg batch taken from 80% to 12% moisture content (wet basis) releases in the order of 77 kg of water. That mass must be removed by the room's dehumidification, otherwise the dryer re-wets what it has just dried.

The kinetics count as much as the target: a slow, controlled descent — moderate temperature, decreasing relative humidity, gentle air movement — preserves volatile compounds better than accelerated drying. In post-harvest, “fast” is a defect, not a selling point.

Water activity, the only measurement that attests stability

Moisture content (as a percentage) and water activity (aW, from 0 to 1) are two distinct quantities. It is aW that governs microbiological stability: two batches at identical moisture content can have different aW and opposite fates. A measurement on leaving the dryer, recorded in the batch log, is worth more than an assessment by touch.

The real cost item is still labour

Equipment weighs little against hours worked. Investment is reasoned from your real rate — kilograms per person per hour at the expected finish, days the workshop is tied up, fully loaded hourly cost — and judged on the hours taken out of the schedule at constant quality, never on the quoted throughput. Three criteria govern that outcome: cleanability (stainless steel, tool-free dismantling, real time between batches), safety (rotating parts, inhalable plant dust in dry processing, capture at source) and traceability, one batch per container with its log.

Where to go next

Mechanical trimming opens this chain: it is covered in detail in the section on trimming machines. Drying and then curing are explained in our article drying and curing, the stage that decides quality. For non-professional use, nets and small containers appear in the after-harvest section.