Produce and fish display humidification

How shrinkage falls

A harvested fruit or vegetable goes on living; it respires and it transpires. When the air around it is dry that transpiration speeds up, the product loses weight, leaves wilt and skins wrinkle. Every hour on the display adds to that loss.

A misting system builds a thin layer of humid air immediately around the produce. Because that air is already close to saturation, it draws water out of the product more slowly. The result is that the same product looks fresh on the display for longer, and the quantity thrown away at the end of the day drops.

The visual effect matters commercially too: produce that looks moist and bright reads as fresh to a customer. That is one of the main reasons the system spread so quickly through greengrocers.

How the system is set up on a display

On a display we use the same high pressure system as on a cafe terrace; what changes is the set-up, not the equipment. In a cafe the aim is for the fog never to touch anyone. Here, the aim is a thin layer of humidity around the product.

We build that difference with three adjustments: nozzles are angled rather than placed directly above the produce, the line runs closer to the product than it would in a cafe, and the system is programmed to run in short, frequent bursts rather than long ones. The same hardware gives a completely different result.

On displays very close to a customer walkway, or in stores where the floor absolutely must not get wet, the set-up is tightened further; there the system protects the product and contributes to in-store comfort at the same time.

Layout over the display

• Nozzle height: just above the product surface. Mounted too high, the humidity disperses before it reaches the produce.
• Angle: slightly angled, not straight down. This builds a humid layer without wetting the product.
• Spacing: evenly along the display. On deep displays one line is not enough and two parallel runs are used.
• Duty cycle: short and frequent. Long runs wet the product instead of forming a humid layer.
• Floor drainage: draining water that collects under the display has to be planned from the start; slip risk is the single biggest source of complaints in food retail.

Fish and meat counters

On fish counters, misting slows the rate at which the ice melts and stops the product surface drying out. Here the nozzles usually go along the front edge of the counter rather than above it, facing inwards rather than towards the customer.

On any system in contact with food, water hygiene is a subject of its own: the line is protected with a one-way valve, no storage tank is used, and it is disinfected at the start of the season. More detail is on the water quality page.

Pre-cooling: before the display

Step back from the display and the real loss happens between harvest and entry into the cold chain. Produce comes in from the field carrying field heat, and until that heat is shed, deterioration accelerates.

Pre-cooling aims to drop that field heat quickly by passing the product through a fog environment before it goes into storage. Systems installed in post-harvest holding areas, on grading lines and at loading bays also reduce the load on the cold store, which shows up as a saving on the energy side. More on the pre-cooling page.