📖 How to study this course (Hybrid)
💻 Online
Work through the modules below on any phone. Use the built-in self-check quiz, log your sessions in the Study Diary, and ask the rAs AI assistant (💬 button on the homepage) whenever you're stuck.
📴 Offline
Low data? Open this page once, then use your browser's Download page or Print → Save as PDF to keep a full offline copy. Every module includes a hands-on practical you do away from the screen — that is where the real learning happens.
🎯 What you will be able to do
- Build a low-cost solar dryer from local materials
- Dry fruits and vegetables to safe moisture levels
- Test dryness correctly and store dried produce
- Cost and sell dried products profitably
📚 Course Modules
Module 1: Why solar drying beats open sun drying▾
- A solar dryer traps heat under clear plastic/glass, reaching 45–65°C vs ~30°C in open sun — drying in 1–2 days instead of 3–5
- The enclosure keeps out flies, dust, rain and animals — the main causes of contaminated dried food
- Faster drying means less time in the spoilage zone and better colour and vitamins
🛠️ Practical task: Dry two identical batches of sliced tomato: one open-sun, one under a clear plastic sheet raised on a frame. Compare speed and cleanliness.
Module 2: Building a direct solar dryer▾
- Basic cabinet dryer: black-painted box, clear cover at ~20–30° tilt toward the sun, mesh trays, vent holes low (air in) and high (moist air out)
- Materials: timber or brick frame, clear UV plastic or old window glass, mosquito mesh trays, black paint
- Size guide: 1 m² of tray area dries roughly 4–8 kg of fresh produce per load
🛠️ Practical task: Build a 1 m² cabinet dryer using the design above. Total materials should cost under $30 — apply the Iron-Clad Price Check on the plastic and mesh.
Module 3: Preparing produce▾
- Wash, then slice evenly: tomatoes 5–8 mm, mango 5 mm, leafy greens whole
- Blanch vegetables 1–3 minutes in boiling water to keep colour and stop enzymes
- Dip fruit in lemon juice solution to reduce browning
- Load trays in a single layer, pieces not touching
🛠️ Practical task: Prepare and load one full tray each of a fruit and a vegetable, recording weights before drying.
Module 4: Managing the drying process▾
- Target temperature 50–60°C; above 65°C food case-hardens (dry outside, wet inside)
- Turn pieces every few hours; bring trays in at night or cover against dew
- Vegetables are done when brittle; fruit when leathery and no juice when squeezed
- Final moisture targets: vegetables ~10%, fruit 15–20%
🛠️ Practical task: Dry your loaded trays to completion, weighing every few hours and plotting weight loss.
Module 5: Packaging and storage▾
- Cool completely before packing — warm food sweats and moulds in the bag
- 'Condition' fruit: put in a jar for 4–7 days, shake daily; any condensation means dry further
- Pack in airtight bags/jars, store dark and cool; well-dried produce keeps 6–12 months
🛠️ Practical task: Condition, pack and label one batch with product name, date and weight.
Module 6: The solar drying business▾
- Weight loss is 80–90% for tomatoes — 10 kg fresh becomes about 1 kg dried, so dried products command premium prices
- Best sellers across Africa: dried tomatoes, mango, kale/ulimi, chillies, okra, fish
- Sell to shops, schools, and city markets in the off-season for 2–4× fresh-season prices
🛠️ Practical task: Calculate: if fresh tomatoes cost $0.50/kg and dried tomatoes sell at $6/kg, what is your gross profit per 10 kg fresh batch after $1 of packaging?
⚠️ Safety & legal essentials
- Use food-grade or well-washed plastic; never dry on bare ground or old fertilizer sacks
- Dry fish and meat require salting first — a solar dryer alone may not be fast enough to beat spoilage in humid weather
- Check for mould before packing; one mouldy piece spoils the bag
💰 Typical startup budget
Costs vary widely by country — treat these as a planning guide, in USD, for a small starter operation:
| Item | Typical range |
|---|---|
| Clear UV plastic / glass | $8–15 |
| Timber & nails | $8–12 |
| Mosquito mesh trays | $4–8 |
| Black paint | $3–5 |
| Packaging bags/jars | $5–10 |
✅ Iron-Clad Price Check: before buying ANY item above, call at least 3 suppliers and compare prices. This single habit typically saves 30–50% on startup costs.
📈 Turning it into a business
- A $30 dryer paying back in 2–3 batches of dried tomato is common
- Contract with farmers for gluts (harvest surplus) at low prices
- Offer drying-as-a-service: farmers pay per kg to use your dryer
🧠 Self-check quiz
Q1. What temperature range should the dryer run at?
Show answer
50–60°C; above ~65°C causes case-hardening.
Q2. Why blanch vegetables before drying?
Show answer
It stops enzymes that cause browning and flavour loss, and speeds drying.
Q3. How do you test if fruit is dry enough?
Show answer
Leathery texture, no juice when squeezed, and no condensation during 4–7 days of conditioning in a jar.
Q4. Roughly how much dried product comes from 10 kg fresh tomatoes?
Show answer
About 1 kg — 80–90% is water.
🎓 Get your Business Seed Record — enroll on the rAs homepage
Certificate option ($10) includes a verified digital certificate with a unique ID.