Tropical Fruit Drying Systems | 1,500 kg per Batch

Case hardening is the failure mode to design against

Case hardening happens when the surface dries faster than moisture can migrate out of the centre. The result looks dry, weighs wrong, and holds moisture inside that shortens shelf life and shows up as mould weeks later at a buyer’s warehouse. It is the single most common and most expensive drying failure on high-sugar fruit.

It is avoided by staging temperature rather than driving it, and by holding air velocity in the 2.5–3.0 m/s band so surface moisture is carried away at the same rate it arrives. Slice thickness matters too: 5–8 mm is the working range on mango, and thicker slices widen the gradient the whole cycle has to manage.

What the moisture load costs

Tropical fruit arrives wet. Pineapple in particular combines very high initial moisture with high sugar and high acidity, which makes the cycle energy-intensive as well as delicate. This is precisely where a biomass burner firing local residue changes the economics: the fuel cost of removing that much water is the dominant running cost, and it is the cost that moves most when residue replaces diesel.

Crops in this family

Crop	Drying temperature	Target moisture	Slice / yield note
Mango	65–70 °C	12–14 %	5–8 mm slices, ~85 % process yield, ~10 : 1 whole fruit to dried
Pineapple	40–100 °C chamber range	Product specific	Very high initial moisture; staged profile against browning
Banana	40–100 °C chamber range	Product specific	Enzymatic browning control is the quality driver
Dates	40–100 °C chamber range	Product specific	Very high sugar; late-cycle behaviour changes sharply
Fig	40–100 °C chamber range	Product specific	Skin texture determines perceived quality
Baobab	40–100 °C chamber range	Product specific	Powder-bound; drying precedes milling
Bush mango	40–100 °C chamber range	Product specific	Kernel drying rather than flesh drying
Mixed dried fruit	40–100 °C chamber range	Product specific	Recipe per fruit; segregate by aroma and allergen

The equipment behind these crops

Frequently asked questions

How much fresh fruit do I need per tonne of dried?

For mango, about ten tonnes of whole fresh fruit per tonne of dried, measured at intake before peel and stone removal, at roughly 85 % process yield after trimming and grading. Other tropical fruit vary with initial moisture and how much is discarded as peel, core or stone, so the ratio is calculated per crop rather than carried across.

Do I need sulphite to keep the colour?

No, but pre-treatment affects colour and shelf life. Citric or ascorbic dips are common; sulphite must be declared for the EU market. Pre-treatment is part of your process specification rather than part of the dryer. What the dryer contributes to colour is holding the lower part of the 40 to 100 °C range steadily, on an even 5 to 8 mm slice.

Can one line run several fruits in a season?

Yes, and it is usually what makes the investment work. A mango line idle outside a six-week harvest is a poor asset; the same chambers running pineapple, banana and vegetables the rest of the year is a good one. The same 1,500 kg chambers hold each fruit on its own PLC recipe, and the constraint is cleaning between allergens and strong aromas rather than capacity.

Drying systems for tropical fruit