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Download Area

Contact us

MM2100 Industrial Town

Jl. Bali I Blok T-3

Cikarang Barat - Bekasi

Jawa Barat - Indonesia 17520

 

P. +62-21 898 03 18 (Hunting)
F. +62-21 898 03 19
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Retort Food E-mail

APPLICATION AND STRUCTURE

1. Retort Food
1-1) What is retort food?
Retort food is cooked food to filled in pouches or containers made of plastic film, metallic foil, or these materials in multi layer form, then sealed by heat sealing followed by sterilisation using heat and pressure (define by JAS)
1-2) Production process of retort food
There are various kind of production process for retort food. Following is the production and distribution process of retort curry.

  • Roast : Curry powder, Flour, Edible oil
  • Boiling : Curry roux, meat, vegetable, etc.
  • Filling : Automatic filling into retort pouch
  • Sterilisation : Retort treatment (120 oC, 30 min)
  • Packing : Carton box
  • Distribution : Cardboard box, assembly packaging
  • Consumption : It can be boiling into hot water without opening the pouch
1-3) Packaging style for retort food
Generally, the construction for retort pouch is PET/ON/Al/CPP or PET/Al/ON/CPP which make good use of heat resistance and high barrier performance of aluminium foil. Usually, retort pouch is located in carton box, but recently we can see retort pouch itself without carton box.
2. Required Quality for Retort Pouch
1) Heat resistance
No deterioration in quality of pouch (transformation, discoloration) by pressure- heat sterilisation under high temperature.
2) Barrier performance
No deterioration in the quality of content by moisture, oxygen, ultraviolet, light, etc.
3) Aroma preservation
4) Bag fall resistance, pin-hole resistance
5) High seal strength
It required more than 2,3 kg/15 mm seal strength after retort treatment
6) Automatic filling property
7) Hygienic
Material for retort pouch should be approved by public institution
8) Others
Convenience, easy tearing
3. Retort Pouch, Lidding
3-1) Non transparent type
About non transparent type, aluminium foil which can be cut off water, oxygen, aroma, light, perfectly is used as middle layer material. Therefore, this type of pouch can be maintain the quality of content for long time same as can and bottle under the normal temperature condition. Also it can get print effect using aluminium foil’s luster. Three or four layers which using aluminium foil is representative construction for retort pouch. In case of four layers construction, ON and aluminium foils are located side by side in order to up the pin-hole strength and protect aluminium foils from the corrosion which cause by alkali etc. of the contents. Now, four layers construction is becoming popular.
3-2) Transparent type
About transparent type, content can be seen from the outside of the pouch. But it has apprehension that the deterioration in the quality of flavour, color and aroma because of the barrier performance against O2 gas, water vapor, ultraviolet and light is not perfect compare with the pouch using aluminium foil.
Main application of transparent type pouch is for low oil content food and comparatively rare deteriorate food such as rice, rice cake, also for the chilled food such as hamburg, meat ball, and for business use which distribution term is short. In this case, ON/CPP (sometimes LLDPE) is most popular construction for transparent type of retort pouch because this construction has good pin-hole resistance, impact resistance and barrier performance. The temperature of retort treatment is 100-120 oC.

If high barrier performance is required like application for sweetcorn, three layers construction such as ON/PVDC/CPP is used. It should be pay attention to the deterioration of barrier performance and white coloration by the retort treatment when KON or EVOH is used. And recently transparent metallized PET film such as silica (SiOX)-deposited PET film and oxidised aluminium (Al2OX)-deposited PET film have entered commercial use.
3-3) Container and lidding
There are transparent type and non transparent type for container like cup and tray. For lidding, transparent type (ON/CPP) and non transparent type (PET/ON/Al/CPP) are very popular. Materials which use for these kind of transparent type and non transparent type should be fit for retort (100-120 oC), high retort (120-135 oC) and ultra retort (135-145 oC) sterilisation. The shelf life of retort pouch which using transparent type of pouch is 1-6 months and non transparent type which construction has aluminium foil is 1-2 years.
4. Materials for Retort Pouch
1) Surface materials : PET, ON
2) Barrier materials : Al, PVDC, SiOX deposited PET
3) Reinforce material : ON
4) Sealant : CPP, LLDPE, HDPE
5) Adhesive : Retort grade (two component liquid type of polyester)
4-1) Oriented PET film
It requires for the materials of retort pouch that the heat resistance, strength, seal strength, no blocking, printability, and dimensional stability. PET film has characteristics of printability, machinability, heat resistance, transparency, gloss and it prevents aluminium foils from the corrosion, also pin-hole break out. Melting point of PET is high (260 oC) so it is very little that the dimensional change when PET is sealed by seal bar.
4-2) Oriented Nylon Film
1) Non transparent type
Nylon film is used for reinforce material (pin-hole resistance, bag-fall resistance). Nylon has the characteristic of the moisture absorption so water easily go into the area between ON and Al which does not have water vapor permeability. Shrinkage is larger under retort treatment conditions. Shrinkage sometimes lowers lamination strength causing delamination between ON and Al. So it is better to avoid the construction (ON/ad/Al/ad/CPP), to set retort treatment lower than 120 oC and select the suitable adhesive. In case of dry lamination, whether corona treatment is or isn’t and some type of adhesive sometimes make parse strip. Corona treatment of ON should be put on sealant side, also CPP should have corona treatment.
PET corona/ ad / AL / ad / ON corona / ad / corona CPP
PET corona/ ad / ON corona / ad / Al / ad / corona CPP

2) Transparent type
ON/CPP (or LLDPE) construction is popular. In case of KON/CPP construction, retort treatment sometimes make deterioration of barrier performance and white coloration. So ON/PVDC/CPP construction is used instead of KON/CPP. Sometimes deterioration and white coloration are caused by hot shower type or steam type of retort treatment.
4-3) Cast Polypropylene
CPP has function of protector against pin-hole and aluminium foil corrosion as a sealant which is located most inside layer of the pouch. Also sealability and impact strength are required, CPP for retort grade which has heat resistance and impact strength should be used for this application. CPP for bread, snack and instant noodle grade can not use for retort pouch, because impact strength is not enough.
4-4) Aluminium Foil
Aluminium foil is one of the basic materials for retort pouch because it has excellent barrier performance against light, oxygen and water vapor. Recently transparent metallized PET film such as SiOX-deposited PET film and oxidised aluminium (Al2OX)-deposited PET film have entered commercial use.
4-5) Adhesive
  1. Dry lamination is suit for retort pouch (extrusion coating can not use). Heat resistance is different between semi retort grade CPP and high retort grade CPP.
  2. There is slight difference of adhesion performance even if the same kind of component adhesive.
  3. Thickness of adhesive should be more than 2 at least, normally 3-4 coating thickness is required.
  4. 2-3 days ageing term is required under the 40 - 50 oC temperature condition.
5. Construction of Retort Pouch
5.1) Transparent type

In case of transparent type retort pouch, we can see the content from the outside but compare with the pouch which using aluminium foil, barrier performance for oxygen, water, aroma and light is not perfect. Therefore preservation term is short (1 - 6 months) and requires chilled preservation . generally, ON/CPP (or LLDPE) which has heat resistance, pin-hole resistance and impact resistance’s representative construction of transparent type. If it required high barrier performance, ON/PVDC/CPP is used. Recently transparent metallized PET film such as SiOX - deposited PET film and Al2Ox-deposited PET film have entered commercial use.
5.2) Non transparent type

About non transparent type, aluminium foil which can be cut off water, oxygen, aroma, light perfectly is used as middle layer material. Therefore, this type of pouch can be maintain the quality contents for a long time (1-2 years) same as can and bottle under the normal temperature condition. Three or four layer whites using aluminium foil is representative construction for retort pouch.  As standing pouch getting popular and omission of carton box, impact strength and pin-hole resistance are required, accordingly four layer construction (PET/ON/AL/CPP or PET/ON/AL/CPP) is becoming popular. Retort grade of CPP is used as a sealant and its lamination method is dry lamination. Recently the material for retort pouch which easy peel performance is required because mostly we open the pouch after boiling.
5.3) Container and lidding

There are non-transparent type and transparent type for lidding of retort cup. Construction is basically same as retort pouch.