Cold Storage for Potato in India: Seed, Table and Processing Rooms

Potatoes are stored at 90–95% relative humidity whatever their end use, because tubers lose weight and shrivel in drier air. Temperature is what changes, and it must follow each lot's end use.

Two opposing effects set these bands. Below about 4 °C sprout growth is minimal, so seed is held at 2–4 °C without any chemical. But colder tubers convert more starch to sugar; this cold-induced sweetening spoils table potatoes and makes chips and fries brown and bitter, so processing stock is kept warmer and relies on sprout control instead.

Published values vary by variety and source. The HyperCold cold storage temperature chart lists 4–5 °C for long-held table potatoes; warmer table setpoints are used only where sprouting is controlled by other means. Processors usually issue their own specification (8–10 °C is common), and it overrides any general table.

Freshly dug tubers have thin, easily skinned surfaces and fresh wounds from digging. Curing lets the skin set and wounds heal (suberisation) before chilling, because wound healing almost stops at storage temperature. Widely published curing conditions are about 15–20 °C and 90–95% RH for one to two weeks.

In the Indo-Gangetic plains the main crop is dug in late winter, and growers usually let tubers skin-set in shaded heaps before bagging. Whatever the method, these checks protect the whole chamber:

• Sort out cut, bruised, greened and diseased tubers; one soft-rot pocket can spread through a stack.
• Do not load wet or mud-caked potatoes: surface water feeds rot, and soil blocks air paths.
• Record variety and harvest date for every lot to track sweetening and sprouting.
• Keep seed lots separate from table and processing lots from the day they arrive.

Temperature is the first and safest sprout control: seed held at 2–4 °C stays largely dormant on its own, which is also why seed chambers should never share air with chemically treated stock.

Warmer table and processing stock needs an additional control. CIPC (chlorpropham) has long been used, but it is a regulated chemical whose rules keep changing: it is no longer approved in the European Union, and in India its registration, permitted uses and residue limits are set by the Central Insecticides Board and Registration Committee (CIB&RC) and FSSAI. Use only a currently registered product, applied by a trained applicator exactly as the label states, never in or near seed stock, and check buyer and export-market residue requirements first. No dosage is given here: the label and the current notification are the only valid source. Ethylene and plant-oil suppressants exist in some markets but need their own approvals.

Whatever the method, keep a fresh-air exchange schedule, because carbon dioxide from respiring tubers builds up in a closed chamber and affects sprouting and fry colour. Sweetened table potatoes can be partly reconditioned at about 15–20 °C for one to three weeks before sale, but recovery varies by variety and is often incomplete: a rescue step, not a storage plan.

Most Indian potato stores hold tubers in 50 kg jute or leno (mesh) bags on multi-tier racks; seed and processing lots increasingly move in plastic crates on pallets. Either way, air must reach every bag:

• Stack in rows parallel to the airflow, with gaps between rows so air moves through the stock and not only around it.
• Keep the evaporator throw and return-air path clear; never stack against the coil face.
• Keep bags off the floor on pallets or racks so air also passes underneath.
• Stack lot by lot, so any lot can be inspected or removed without unstacking its neighbours.

HyperCold's configurator estimates capacity as gross volume (m³) × usable fraction × as-stacked bulk density (kg/m³) ÷ 1,000. Potato is counted at 650 kg/m³ as stacked (tubers plus bag or crate) and a palletised produce room at a 0.62 usable fraction, which already allows for aisles, 100–150 mm wall clearance, a 300–450 mm ceiling air gap and the evaporator air path. That works out to about 403 kg per m³, or 11.4 kg per cubic foot, of gross room volume.

Tightly racked bag stores can beat 0.62 and hand-stacked rooms with wide aisles fall below it; the ±12% band covers normal variation in bags, grade and stacking.

In a potato store the heaviest product load arrives in the loading season, not in the hottest week of storage. Three loads add up:

1. 1Field heat — potatoes hold about 3.4–3.6 kJ per kg per °C, so cooling 10 MT a day from 30 °C to 4 °C within 24 hours needs roughly 10–11 kW, or about 3 TR, for the tubers alone.
2. 2Heat of respiration — modest in mature, cured tubers at storage temperature, but it roughly doubles to triples with every 10 °C rise and is higher in immature, bruised or freshly dug tubers, so it peaks in the first days after loading.
3. 3Envelope, infiltration and door loads — heat through panels and floor, plus warm air entering while doors stay open during loading.

The envelope load peaks later, when north Indian summers reach 45 °C. The plant must cover the worse combination, which is why HyperCold adds a 15–20% safety factor to the calculated heat load for north Indian sites. Size it on the daily loading rate (MT per day and arrival temperature), not on chamber volume alone, and check it in the heat load calculator.

Lower the setpoint in steps over several days after filling instead of dropping straight to the final temperature: this limits condensation on the tubers and keeps the plant from being swamped while stock is still arriving. Once at temperature, the stock's thermal mass rides through short power cuts, but loading-season outages hit when the load is highest, so plan DG backup with auto-changeover.

Uttar Pradesh and West Bengal are India's two largest potato-growing states, and Punjab is a major source of seed potato for other states. In the plains, the main crop is harvested in late winter, just before a long summer that rules out ambient storage. Seed must be held until autumn planting, and table potatoes are released through the summer and monsoon. That concentrated harvest, hot holding season and long storage period are why so much of India's bulk cold storage was built for potato.

HyperCold is headquartered in Sirsaganj, Firozabad, in the Agra region, a major potato-growing belt. Mature belts like this already have dense storage capacity, so a new project there needs an edge beyond space: separate seed, table and processing chambers, reliable temperature records, or other commodities in the months when potato chambers stand empty.

A single hall forces one setpoint on seed, table and processing stock, and one fault or rot outbreak puts every bag at risk. Separate chambers give:

• Different setpoints — seed at 2–4 °C, table at 4–8 °C and processing at 8–12 °C side by side.
• Staged loading — field heat hits one room at a time while full chambers stay stable.
• Staged unloading — seed chambers empty together at planting time, and no half-empty hall has to be kept cold.
• Risk isolation — a refrigeration fault, sprout-suppressant treatment or soft-rot outbreak stays in one chamber.
• Shared walls — rooms built in series share common walls, and HyperCold's configurator deducts the saved panel area once for the whole group.

Panel and machine selection follow each setpoint. On HyperCold's rate card the 100 mm PPGL PUF panel covers 0 to +8 °C and the 80 mm panel +8 to +15 °C; the Daikin range splits the same way, with MT (medium-temperature) units for 2–8 °C and HMT (high-medium temperature) units for 8–15 °C. So a 2–4 °C seed chamber takes 100 mm panels and MT units, and an 8–12 °C processing chamber can use 80 mm panels and HMT units. When pricing a seed chamber online, pick the Chiller Room (0 to +8 °C) application; the Fruits & Vegetables Cold Room is priced on the 80 mm and HMT basis. Above about 1,500 MT, compare ammonia and Freon systems too.

Add an ante room or covered loading bay so dispatch lots can be warmed gradually before they leave.

Setpoint, number of chambers and daily loading rate move the cost more than tonnage does. Main BOQ lines on the HyperCold FY2026-27 rate card:

Outside the rate card, budget for civil work and floor insulation, racks, the electrical connection and transformer, DG backup and, where rural voltage swings, a servo stabiliser. Final pricing depends on the site survey. Build a line-item BOQ in the quotation configurator, compare indicative bands on the cold room cost page, and check the cold storage subsidy page: horticulture cold storage, including potato, may qualify for credit-linked, back-ended MIDH or NHB assistance or AIF interest subvention, subject to current scheme guidelines.