“PPD” and “PE” represent the material of which the bags are made. PP is an abbreviation for polypropylene (D stands for Durable) whereas PE stands for polyethylene. These are polymers of respectively propylene and ethylene and have different physical and chemical properties.

The consequence of these differing monomers is that polypropylene can be autoclaved and polyethylene cannot. If you’re looking for a bag which can be autoclaved together with the substrate at 121°C, you’ll need a bag from our PPD range.

Luckily there are ways to sterilize PE bags, for instance through gamma irradiation. This guarantees a 100% completely sterile product and is most often used in bulk production processes or in systems where sterilised bags are poured into another bag before inoculation.

Filters up:

For the production of spawn, we strongly recommend to use “filters up”- Microsacs, in which the filters are situated on the upper half of the bag.

Fill the bag till the grain carrier touches the lowest filter. This sounds like a contradiction considering the rule is to keep the filters as dry and clean as possible, but it is necessary to ensure a correct autoclaving cycle. If gas exchange is impossible during autoclaving, the bag might either become stone hard from compression when the pressure is building up, or explode when the pressure is lowered. Moreover, this touching filter allows the vapour to penetrate the substrate, leading to a shorter time lag for the centre of the bag to reach the required temperature of 121°C.

After cooling down, inoculation and shaking, turn the Microsac upside-down, so the  filters are positioned alongside the grain carrier, thus ensuring an evenly distributed gas exchange.

Evenly distributed Filters

The Microsac with its filters evenly spread over the bag is meant to contain more grain carrier. Several filters will touch the grains and therefore the risk of water absorption during the autoclaving cycle is higher. If you run a well organized lab with a high standard of hygiene and you adopt a correct working attitude, you can opt for this system. The autoclaving cycle will be a little faster than with the “ filters up”- Microsacs because more steam can penetrate through the filters.

We have two version bags: bags with the (Regular) R-filter and bags with the S-filter.

The type of filter is mentioned in our codes.
For example:
Our model PP75-REU6-X32-57 is a bag with R-filter, and
the model PP75-SEU6-X37-57 is a bag with S-filter

The S-filter gives more gas exchange against the R-filter. This is why the S-model is mostly used for Substrate and the R-model for Spawn.

Other parameters related to the gas exchange are of course the amount of filters per bag and the volume of the bag.
Only thorough tests will tell which bag is the most suitable for which products and which bag gives the best results for your purpose.

The B filter is not a standard filter anymore and this one is our safest filter but gives the least gas exchange.

We recommend storing the bags in a clean and dry place at a minimum temperature of 15°C – 60°F. Storage at temperatures below 0°C (frost) can cause heavy damage to PP bags.

We recommend using a heat sealing device for both PP and PE Microsacs. We have tried and tested many different machines and have had best results with the devices we offer. Have a look.

The code of our PP bags seems complicated but includes all the information of the bag type. It consists of three parts: the first part indicates the used film; the second part mentions the type and the final part describes the size.

For PP (polypropylene) bags:

  1. First part: film
    1. PP Polypropylene
    2. 50/75 Thickness of the film in µm
  2. Second part: type
    1. B/S Thin zipper/broad zipper
    2. E Filter material
    3. U/H/D Filter location on bag: up (near opening)/spread/ down (near bottom)
    4. 2/4/6 Amount of filter strips
  3. Third part: size
    1. V/X Presence of bottom gusset or not
    2. 00-00 Width and length of bag in cm

For instance: PP75/BEU6/X32-57 is a polypropylene bag, 75µm thick with a thin E-filter zipper where the 6 filters are located on the top of the bag which measures 32 x 57 cm and has no bottom gusset.

For PE (polyethylene) bags:

  1. First part:
    1. PE polyethylene film
    2. 80 thickness of the film in µm
  2. Second part:
    1. G/L/T Filter material with T standing for Tyvek©
    2. 3 Amount of filter strips
    3. V Vertically orientated filter strips
    4. (S/M) Small/medium width filter strip
    5. (3/4/7) Number of perforation rows
  3. Third part:
    1. 00-00 Bag dimensions

Standard sterilization through wet steam autoclavation takes place at 121°C and 1 bar overpressure. We advise to place the bags into the autoclave without the filters touching the wet substrate. Sterilization time will differ according to filling volume/weight.

No, there’s a good chance your bags will explode during the cycle. The only reason why you would, is when your autoclave does not exit into a cleanroom, i.e. your cooling room does not meet hygiene requirements.

Our PP (polypropylene) bags are guaranteed to resist temperatures up to 124°C. Sterilization should be done at 121°C. Please note that PE (polyethylene) bags are NOT autoclavable.

Since our polyethylene bags are non-autoclavable but sterility is top priority in the mushroom business, we offer these bags pre-sterilized. This means that the bags have undergone a gamma irradiation treatment to ensure complete sterility. The bags are prepacked per 50 pcs in an overbag, which are then prepacked per 3 packets of 50 in another larger overbag. That way you’re flexible to use less than a full carton after opening the package.

Saco2 takes pride in a wide portfolio of products. Besides Microsacs and Microboxes we also sell related machinery. Whether you need a tumbler or a sealing device, take a look on our machinery page and see what we have on offer.

If you can’t find your fancy in our product range, please know that we’re happy to discuss custom made bags. We have no problem to make whatever you need for your production process within the limits of our machines. Note that we have a minimum order of 20.000 pcs for custom made bags.

Our filters are made from non-woven materials. The fibres form a three dimensional maze which traps the contaminants. 

As they are non-woven, they do not have a micron rating. However, customer feedback proves that contamination is hardly an issue if the bags are used according to our recommendations.


Read more about Air Plasma treatment here. 

Our plastic is not Air Plasma treated (Corona treated), we have found that the laser seals are stronger with untreated plastic. Air plasma treated bags are easier to print on and their surface is better at accepting adhesive labeling, but without the treatment the bags are stronger, the seals hold up much better, which is more appropriate and important for your purposes.


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