United Snacks, Lahore — two-phase potato cold store with humidifiers, low-TD evaporators, and CO₂ purge control

Chips seem simple — sliced potato, hot oil, salt. But between the farm and the fryer, the potato is a biochemically active tuber that will betray you if the cold chain is wrong. United Snacks, the Lahore-based company behind Oye Hoye, one of Pakistan's most recognised chip brands, operates a manufacturing complex that processes hundreds of tonnes of potatoes per year. The quality of that product — its colour, texture, and shelf life — is set largely in two rooms before frying starts: the raw-potato cold store and the finished-goods chill store. Izhar Foster built both.

The single biggest quality risk in chip manufacturing

Raw potato starch begins converting to reducing sugars — primarily glucose and fructose — when the tuber is held below +5°C. This is a well-documented biochemical pathway called low-temperature sweetening. When those reducing sugars hit 180°C frying oil, they react with free amino acids through the Maillard reaction at an accelerated rate, producing dark, bitter chips that fail colour-grading at the line and are pulled before packaging.

The industry target is +6 to +8°C for raw potato storage: warm enough to suppress starch-to-sugar conversion, cool enough to suppress respiration, sprouting, and pathogen growth. This 2°C control band — maintained 24 hours a day across a Lahore summer that reaches 47°C ambient — requires refrigeration engineering designed for the purpose, not adapted from general-purpose cold storage.

Holding +6 to +8°C in Lahore is achievable. Holding it with ±0.5°C stability, under a variable load from store filling and seasonal swing, requires a well-sized plant with capacity modulation and good defrost logic. That is what Izhar Foster sized and installed.

Low-TD evaporators and the humidity engineering challenge

The second parameter in a potato cold store is relative humidity: 85 to 90% RH. This matters for a direct economic reason — a raw potato loses 1 to 2% of its fresh weight per month in a standard low-humidity chill store through transpiration. At manufacturing scale, weight loss is a PKR write-off every single month on product you paid for at the farm gate.

The engineering problem is that refrigeration equipment naturally dries air. An evaporator coil colder than the dew point of room air will condense moisture out of the room — exactly what a dehumidifier does. The colder the coil surface relative to the room, the more moisture it strips. Standard evaporators, sized for efficient heat transfer with a large temperature difference (ΔT) between coil and room, run a coil surface well below the dew point and strip aggressively.

The solution is a low-TD evaporator design: a larger coil surface area — typically 30 to 50% more coil than a standard unit — so the required cooling capacity is achieved with a much smaller temperature difference between coil surface and room air. A low-TD unit in a +7°C room might run a coil surface at +3 to +4°C rather than the −2 to −4°C of a standard unit. At +3 to +4°C surface temperature and +7°C room, the coil is barely below the dew point at 85% RH, so it is cooling the room without stripping humidity aggressively.

Even with low-TD evaporators, some moisture is removed during operation. Humidifiers — either ultrasonic disc type or wetted-pad evaporative type — run continuously to compensate. The BMS manages the humidity setpoint by modulating humidifier output against the humidity sensor reading, with an interlock to the evaporator fan speed so the two systems are not fighting each other.

CO₂ control — the often-overlooked third variable

A stored potato is not inert. It is a living tuber respiring continuously — consuming oxygen and exhaling CO₂ and water vapour. In a sealed cold store, CO₂ accumulates. Above roughly 3,000 to 5,000 ppm, elevated CO₂ begins to create off-flavours in potatoes and can inhibit normal respiration in ways that produce fermentation-adjacent compounds. Below 1,000 ppm, the CO₂ advantage in suppressing sprouting is lost.

This is not a controlled atmosphere (CA) store — no CO₂ is injected. The management task is the opposite: ventilate and purge the naturally accumulated CO₂ to keep levels in a safe band. The Izhar Foster installation includes a BMS-managed vent-and-purge loop: CO₂ sensors sample air in the upper zone of the store continuously, and when the reading exceeds the setpoint, motorised dampers open on the pre-conditioned fresh-air supply. The loop flushes accumulated CO₂ out of the store and brings in cooled, filtered outdoor air through a preconditioned duct that prevents temperature or humidity shock to the product.

Seasonal swing — the hardest engineering challenge on this site

Lahore's climate creates a refrigeration design problem that no UK or European cold-store guideline anticipates properly. Summer ambient peaks at 45 to 47°C. The raw-potato store must hold +7°C with maximum product loading. The refrigeration plant is sized for this peak condition. But Lahore winters see ambient dropping to +5°C or below — and at that point, the refrigeration load in the store approaches zero and may reverse: the outside is colder than the room, and heat is leaking into the store from the product (which is still respiring) rather than from the ambient through the walls.

If the system runs at low load in winter without correction, short-cycling of the compressors damages the plant and destabilises the room temperature. If the ambient falls below +5°C, the room itself may cool below the +6°C threshold and trigger low-temperature sweetening — the very defect the store exists to prevent.

The Izhar Foster design addresses this with two mechanisms:

• Capacity modulation on the refrigeration plant — variable-speed compressors or multi-stage scroll staging so the plant can run at 20 to 25% of design capacity in winter without short-cycling.
• Supplementary heating elements — thermostatically controlled electric heaters integrated into the air-distribution plenum, activated by the BMS when room temperature approaches the +6°C lower limit. These run briefly and efficiently given Lahore's mild winters, but they are essential for a 24/7 year-round operation.

This dual-mode design — cooling in summer, heating in winter — is standard Izhar Foster practice for produce cold stores in Punjab, and it is embedded in the load calculator sizing methodology.

The finished-goods store — the opposite problem

Once Oye Hoye chips are fried, seasoned, and packed, they face a different threat: moisture. A chip is a desiccated, oil-fried snack with roughly 2% moisture content by weight. Exposed to a humid atmosphere, the crisp absorbs water vapour through the bag seal zone, softening rapidly and developing rancidity as moisture catalyses fat oxidation. The shelf life degrades from months to weeks.

The finished-goods chill store runs at +7 to +10°C with low relative humidity — below 50% RH. Standard evaporators are appropriate here because the dehumidification effect of a colder coil is actually desirable. The room is sealed from the raw-potato store via a double-door airlock: the two rooms must never share air because the high-humidity environment of the raw-potato store would devastate finished-goods quality if the doors were left open.

The BMS manages both rooms from a single panel, with independent control loops, independent alarms, and a door-open interlock that alerts operations if either insulated door is left ajar beyond a set time threshold.

Why the building envelope matters as much as the refrigeration plant

A raw-potato store that holds ±0.5°C under full loading depends on a low-conductance envelope that minimises heat ingress from outside. Every watt of heat that enters through the walls, roof, or floor is a watt the refrigeration plant must reject — and in a Lahore summer, the gradient from +47°C ambient to +7°C inside is 40 K.

Izhar Foster's FireSafe PIR sandwich panels at 100 to 150 mm thickness achieve a U-value of 0.14 to 0.19 W/m²K with a measured λ of 0.022 W/m·K (BS EN 14509, aged value). Compared to a traditional EPS-insulated cold room, the PIR envelope reduces conduction heat gain by roughly 35% for the same nominal thickness — which translates directly into a smaller refrigeration plant, lower running cost, and less stress on the capacity-modulation system during seasonal swing.

The floor is on-grade insulated slab with PIR board below the concrete, continuous vapour barrier, and reinforced-screed finish compatible with forklift point loads. The insulated sliding doors between the raw-potato store, the finished-goods store, and the ambient loading bay are Izhar Foster's own manufacture — multi-stage gasket seals, electric door heaters at the frame where condensation risk is highest, and a door-status microswitch wired to the BMS alarm panel.

Parameter	Raw potato store	Finished goods store
Operating temperature	+6 to +8 °C	+7 to +10 °C
Relative humidity	85–90 %	<50 %
Evaporator type	Low-TD, large coil	Standard DX ceiling unit
Humidification	Ultrasonic / wetted-pad	None (desiccant environment)
CO₂ management	Vent-purge BMS loop	None required
Seasonal heating	Electric element, BMS-controlled	Not required
Panel thickness	150 mm PIR (U 0.14 W/m²K)	100 mm PIR (U 0.19 W/m²K)
Floor insulation	75 mm PIR below slab	50 mm PIR below slab
Ambient design DB (Lahore)	47 °C (ASHRAE 0.4% + 2K)	47 °C (ASHRAE 0.4% + 2K)

Izhar Foster's role — and the wider chip cold-chain picture

United Snacks joined a group of food manufacturers — including beverages, dairy, and agriculture — that have standardised on Izhar Foster for their cold-chain infrastructure. The common thread is a demand for engineering that goes beyond the room and into the process: understanding what the product needs at every stage, sizing the refrigeration to that process requirement, and building an envelope that holds the specification for 20 years.

For a chip manufacturer, getting the raw-potato cold store right is the single highest-leverage capital investment in product quality. The low-TD evaporator, the humidifier, the CO₂ purge system, and the supplementary heating element are not optional add-ons — they are the core engineering of a cold store designed for the actual use case rather than a generic temperature hold.

If you are scoping a raw-material cold store for food manufacturing — whether for potatoes, flour, dairy ingredients, or any other humidity-sensitive product — use our cold room heat load calculator to establish the refrigeration requirement, or go directly to the rough cost estimator for a budgetary range. For a site-specific assessment, request a quote — engineers reply within 24 hours.