Automated food sterilization tunnel for sealed trays and pouches of chilled foods

01

Set the time and temperature from the chilled shelf life you need

Campden BRI describes industry heat processes for pasteurised chilled foods such as soups, sauces, ready meals and cooked meats in two groups by shelf life. Short shelf-life products are pasteurised at 70 °C for 2 minutes and long shelf-life products, over 10 days, at 90 °C for 10 minutes, each aimed at a 6-log reduction of Listeria monocytogenes or Clostridium botulinum respectively. [1]

Campden BRI states that 70 °C for 2 minutes, or a time and temperature with equivalent lethality, is the minimum process recommended against Listeria monocytogenes in pasteurised chilled foods with a shelf life of more than 5 days. [1]

The UK Food Standards Agency explains that non-proteolytic Clostridium botulinum can grow and produce toxin at 3 °C and above in vacuum and modified-atmosphere packed chilled foods, and that a shelf life of more than 10 days needs additional controlling factors, set out in its guidance and decision tree. [2] Campden BRI lists 90 °C for 10 minutes as the heat treatment used for products sold beyond 10 days. [1]

Editorial note: the tunnel's job is to bring the slowest-heating point of the densest pack on the belt to the chosen target; ask the supplier for heat-penetration data on your own pack, filling and orientation rather than an air or water set-point.

Give the supplier the product and its pieces, pack type and material, pack dimensions and fill weight, target time and temperature at the coldest point, shelf life and storage temperature, packs per minute, steam, water and power available, and the records you need for each batch.

02

Lay out the zones, belt and dwell time

Wanying, a Chinese maker listing a spray tunnel pasteurizer for glass, PET, cans and stand-up pouches, publishes a standard 5-zone model (two preheat, one pasteurization, two cooling) with a temperature range from ambient +5 °C to 98 °C, belt widths of 1,000 to 2,400 mm, belt speed of 0.5 to 5.0 m/min, dwell time of 5 to 40 minutes, steam or thermal-oil heating and machine lengths of 8,000 to 18,000 mm. [3]

For pouches, Wanying writes that it adds a support platform and reduces conveyor speed to prevent the packs shifting, and that changeover between container families takes about 30 to 45 minutes. [3] Editorial calculation: at 0.5 m/min, a 40-minute dwell needs 20 m of belt travel, more than the 18 m maximum machine length listed, so ask which belt speed and tunnel length together deliver your dwell.

Marlen, a US maker, describes two continuous post-package routes: a water pasteurizer that carries packs on a flighted conveyor through a recipe-driven heating and chilling process using steam injection, water agitation and recirculation, and a spiral pasteurizer that distributes steam, dry heat or superheated vapour with a forward-reversing fan for products in trays and pouches where orientation must be kept. [4]

Marlen contrasts these with surface pasteurizers used before packing, which hold product for 30 to 90 seconds in flame at over 400 °C, or 60 seconds in infrared, while the core stays at 4 °C. [4] Editorial note: those surface systems treat the outside of unpacked product; a sealed-pack tunnel has to heat through the pack to the centre.

03

Water spray, steam or immersion, and has it run your pouch?

The supplier linked to this page lists a spray tunnel pasteurizer that it says handles pouches as well as bottles and cans; the card links to the page reviewed.

Ask each supplier whether the tunnel has run your pack format, which heating medium it uses (water spray, steam or hot water immersion), the maximum water or steam temperature, and heat-penetration results at the coldest point of a full belt.

04

From infeed belt through heating, holding and cooling zones of a sterilization tunnel

05

Pack rate at your dwell sets belt width and tunnel length

06

Send the pack, target and line data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Product: [type; pieces; viscosity]
Pack: [tray or pouch; material; dimensions; fill weight]
Target: [time and temperature at coldest point; shelf life; storage temperature]
Output: [packs per hour]
Utilities: [steam pressure; cooling water; power]
Records: [temperature logs; heat-penetration report]

See manufacturer records Send an enquiry through CNFX