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For years, SKF Elixer has engineered paddy processing plants that treat moisture not as an afterthought but as the central variable in rice parboiling process. Our stainless-steel parboiling plant, installed in over 7,000 locations worldwide.
This blog explores the science behind Paddy Moisture Content, revealing how precise control transforms raw harvest into export-grade grain ready for global tables.
The Impact of Over-Drying and Under-Drying In Parboiling Process
Over-drying triggers micro-fractures in the endosperm. These hairline cracks, invisible to the naked eye, explode during milling, converting whole grains into brokens worth only ₹22–25 per kilogram.
A 2023 study by the Central Rice Research Institute (CRRI) found that paddy dried to 11% in direct sunlight suffered 18% breakage versus 4% for controlled drying at 14%. The financial sting? A 100-tonne lot loses ₹2.5 lakh in value from brokens alone.
Under-drying invites fungal attack. Aspergillus species colonize kernels within 48 hours at 18% moisture and 28°C, producing aflatoxins that render grain unfit for export.
Over-dried rice cooks up fluffy but lacks the creamy mouthfeel of properly hydrated grains. Under-dried kernels absorb excess water during parboiling, swelling unevenly and splitting during steaming. SKF Elixer’s paddy dryers, equipped with online moisture sensors, adjust dwell time in 30-second increments—ensuring 100% gelatinization without stress cracks that plague traditional open-vat systems.
Techniques to Accurately Measure and Control Paddy Moisture
Precision begins with measurement. Capacitance meters read moisture to ±0.2% by detecting dielectric changes in grain samples. Installed inline after each dryer section, they trigger PLC valves to modulate airflow—dropping temperature if readings fall below 13.8% or increasing fan speed above 14.5%. A 2025 trial reduced variance from ±2% (manual sampling) to ±0.3%, boosting yield by 1.8%.
Near-infrared (NIR) spectroscopy offers non-contact monitoring. Sensors mounted over conveyor belts scan 100 kilograms per second, mapping moisture gradients across batches. When paired with AI algorithms, they predict drying endpoints 30 minutes early—saving 15% energy. SKF Elixer integrates NIR with its SCADA systems, allowing mill managers to view real-time heat maps and adjust zones remotely.
Control extends to the Paddy Drying Process itself. Batch dryers with 20-tonne capacity cycle air at 1,200 m³/minute, while continuous columns handle 10 tonnes/hour. Both use PID controllers to maintain 0.5% tolerance. Tempering bins hold grain at 50°C for 2 hours post-drying, equalizing core and surface moisture to prevent stress. In certain installations, this step alone raised head rice from 62% to 67%.
Role of Proper Storage in Maintaining Optimal Moisture Levels
Drying is only half the battle—storage determines whether paddy maintains its quality for parboiling. Even perfectly dried grain can deteriorate rapidly if kept under improper conditions.
After drying, parboiling-grade paddy must ideally be stored at 13–14% moisture. At this level, respiration is minimal and grain can remain stable for 8–12 months in well-designed storage. However, when moisture rises to 15%, the respiration rate nearly doubles. This causes heat pockets and localized condensation, pushing micro-zones to 17–18% moisture—the ideal breeding ground for insects, fungi, and discoloration, all of which directly affect parboiled rice colour and head rice yield.
In large godowns, poor ventilation can lead to 1–2% dry matter loss, translating to lakhs in losses for medium-scale mills. For example, a 5,000-tonne annual storage facility losing even 1.5% to insects and mould suffers nearly ₹2.6 lakh in damage at ₹35/kg value.
Modern infrastructure drastically reduces these risks.
Aerated silos maintain uniform internal temperatures around 25–28°C, even when outside temperatures cross 40°C. Automated ventilation systems activate when internal RH crosses 65–70%, ensuring fresh airflow and preventing moisture migration.
Phosphine fumigation, used as per IS 16501 norms, eliminates insects without impacting rice quality—critical for mills supplying premium parboiled varieties.
For smaller parboiling units, jute bags stored on bamboo or plastic pallets with 50–60 cm spacing can be sufficient, provided RH remains near 60–65%. Moisture-proof covers, dehumidifiers, and regular aeration keep the grain safe until it enters the soaking tank.
Transport is the final link. During monsoon months, even a short exposure to rain can push paddy back to 16% moisture, leading to drying deductions or discolouration during steaming. GPS-tracked, sealed truck tarpaulins and container liners help ensure grain arrives at the mill at the correct moisture, ready for uniform soaking and steaming.
Invest in a High-Performance Paddy Dryer Today
From drying to storage to transport, moisture management decides the colour, yield, and market rate of parboiled rice. Every percentage point of excess moisture increases spoilage risk and reduces head rice recovery—directly affecting profits.
If you want consistent steaming, uniform gelatinisation, and premium-grade parboiled rice, it all starts with precise moisture control.
SKF Elixer’s engineered paddy dryers deliver fast, uniform, and energy-efficient drying—ensuring your paddy enters soaking at the exact moisture level needed for top-quality parboiling.
Upgrade to smarter drying technology and turn every harvest into profit.
FAQs
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1. What is the ideal moisture content for paddy before milling?
13.5% to 14.5% ensures maximum head rice recovery (65–70%) and minimum breakage. Every 1% deviation reduces yield by 0.8–1.2%, costing ₹1.5–2 lakh daily in a 500-tonne mill.
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2. How does over-drying affect rice quality and revenue?
Below 12% moisture, kernels develop micro-cracks, increasing brokens by 15–18%. A 100-tonne lot loses ₹2.5 lakh in value as head rice drops from ₹40,000/tonne to ₹22,000/tonne for brokens.
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3. What happens if paddy is milled at 16% moisture or higher?
High moisture causes gumminess in polishers, fungal growth (aflatoxins >30 ppb), and 8–10% rejection in export markets. Monsoon paddy at 20–24% requires immediate drying to avoid ₹35 lakh losses per 1,000 tonnes.
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4. Which instruments accurately measure paddy moisture in modern mills?
Inline capacitance meters (±0.2%) and NIR spectroscopy (100 kg/second) feed data to PLC systems. SKF Elixer plants achieve ±0.3% variance versus ±2% in manual operations, boosting yield by 1.8%.
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5. How should paddy be stored to maintain 14% moisture long-term?
Use aerated silos with 65% RH control, 10 air changes/hour, and phosphine fumigation. Concrete plinths and insulation prevent re-wetting; proper storage extends shelf life to 12–14 months, saving ₹3 crore annually for 50,000 tonnes.
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