Potato, Onion & Apple Cold Storage Monitoring (Temperature, Humidity, CO2)

The figures below are typical guidance used by storage operators, not a prescription. Growers and store owners should follow the recommendation for their variety and end use from their seed supplier, processor or state horticulture department, and adjust after watching how the stock behaves.

Most storage losses come from three things: sprouting, rot and weight loss. Sprouting starts when a chamber runs warmer than planned for long enough. Rot spreads from wet, stagnant pockets in the stack, especially after condensation on cold surfaces. Weight loss comes from dry air, which draws moisture out of the produce and is paid for directly in lower sale weight.

Onions are the opposite of potatoes on humidity: too damp and they develop neck rot and mould, which is why an onion storage structure is designed around airflow and a lower RH. Apples soften quickly if the chamber runs a degree or two warm. In all three crops the damage is slow and silent, so a store that only checks the controller display once a day finds the problem weeks later.

Most cold stores watch temperature and ignore humidity and CO2. Yet relative humidity decides weight loss and rot, and CO2 rises steadily in a closed potato chamber as the tubers respire. Ventilation cycles are often skipped at night or in hot weather to save power, and nobody can tell afterwards whether they happened.

Ideabytes IoT loggers such as the IBI-MTH120 and IBI-WTH120 measure temperature and humidity across 0 to 100 % RH in condensing conditions, which suits high-humidity potato and apple chambers. The IBI-A-C485 is an NDIR CO2 sensor with a 0 to 10,000 ppm range on RS485 MODBUS, rated for 0 to 50 °C, suitable for tracking ventilation in potato and onion stores. CA rooms that run CO2 above 1 % need the CA system's own gas analyser; our loggers then track the temperature and humidity of those rooms.

A single probe near the door tells you little about a chamber stacked several metres high. Place one temperature and humidity point at the top of the stack, where warm air collects, one in the middle and one near the floor, plus a point in the return air of the cooling unit. Keep sensors out of the direct cold blast from the evaporator and protect them from water and dust.

For large multi-floor stores, the IBI-A-TH485 RS485 temperature and humidity sensor can be run to several positions and read through one IBI-CSC50R Wi-Fi or IBI-CSC50RM 4G MODBUS gateway, which handles up to 15 RS485 devices and up to 30 parameters. The IBI-MTR4 4-channel PT100 logger suits sites that want several temperature points in one chamber over a single 4G connection.

India's potato storage is concentrated in a few belts: Hooghly, Bardhaman and the rest of south Bengal, western and central Uttar Pradesh around Agra and Farrukhabad, Punjab's seed potato districts and Gujarat's Banaskantha region, which supplies processors. Stores in these areas are often large, multi-chamber buildings on the edge of villages, with unreliable Wi-Fi and frequent power cuts during the long storage season.

That is why most of these sites use 4G loggers with a built-in M2M SIM. They keep sending readings and alerts when the local internet or the site router is down, and the owner can watch every chamber from a phone without travelling to the store.

Each chamber gets its own high and low limits for temperature, humidity and, where fitted, CO2. Alerts go by SMS and app notification to the store manager first, then the mechanic and the owner. Every alert and acknowledgement is logged, so there is a record of what went wrong and what was done.

Daily and weekly PDF reports and trend graphs replace the handwritten register. They give traders, banks lending against stored produce, insurers and buyers a clear cold storage temperature chart for each lot. Food businesses licensed by FSSAI also use these records within their food safety management system. For set points across other chilled and frozen products, see our cold storage monitoring page.

Cold storage projects built with assistance under NHB or MIDH schemes often require temperature and humidity monitoring and record keeping as part of their technical standards; check the current conditions with your state horticulture department. Ideabytes IoT is registered on GeM, manufactures in India and provides 21 CFR Part 11 compliant reports.

The cost of a monitoring system depends on the number of chambers, how many points per chamber, whether CO2 is measured, 4G or Wi-Fi connectivity, the software plan and calibration requirements. Share your chamber list and crops for a quotation.