How do we eliminate blisters on fermented crackers like water crackers or cream crackers from an equipment stand point?
The simplest and most effective way to completely remove surface blisters is to spray a very light atomised water mist directly onto the top surface immediately before the product enters the oven.
The spray nozzles should be mounted about 200 mm above the product flow and be evenly spaced to ensure no overlap of spray pattern
No other changes to the process are required other than a slight temp increase in the final zone of the oven as the water mist will result in a slight loss of colour.
Use of this method will almost certainly reduce the final moisture significantly which may be regarded as a good thing (eg in prevention of checking without excessive colouration) or a bad thing (eg water generally being the cheapest part of your final product weight) depending on your product.
During baking, the laminations lift apart irregularly and this is how blisters may form on the biscuit surfaces! The mechanism of this lift principally as a result of discontinuity formed b/w thin sheets of dough (the laminations) by the cracker dust filling, or the skinning caused by flour, or by the dough drying out. The lenticular cavities which are formed initially expend as the air warms, but the greatest expansion result as the water vapor pressure rises when the dough temperature reaches at 60⁰C and more.
Eventually the gas bubbles burst. At this point the gluten and the starch structure in the dough should have been coagulated and gelled by the heat to form a structure that doesn’t collapse completely before the biscuit has dried out.
There are at least three common problems associated with the baking laminated crackers and they act together to compound each other.
One problem, which has just been mentioned, is that if the blisters are too pronounced, they will tend to color to burn very easily. These big blisters will be damaged in post-oven biscuit handling, giving the biscuits an untidy, damaged appearance.
Bad blistering can be result of poor laminations structure caused by insufficient filling dust, a dough quality that is unable to form thin lamination or damage to the laminated structure by crushing or pulling in the final gauging sections. Too hot an oven may also cause bad blistering but this is usually subsidiary to one of the other possible causes.
High temperature at high speed gives the best cracker structures.
I agree with Masud by tradition Laminated Crackers are processed to have blisters and an open texture.
Is your problem that your cracker blisters are too tender?
Marijo published an article of mine a few years ago on this topic, and the application of 'Air Waves Technology' which increased the stack height of crackers by 10% but imporatntly the Blisters were not 'Tender'
Cracker Ovens are designed with a Pre-Heat Section so that the Oven Band is over 200oC before entering the oven, contributing to 'Oven Spring' opening up the texture in Zone 1 with a relatively high temperature, with a higher ratio of Bottpm Heat than Top Heat
The temperatures in Zones 2 and 3 are to drive off the moisture and create the Maillard Reaction
George W Wright
International Food Processing Consultancy
Most of the blisters occur due to chemical balancing, wheat flour quality and process conditions like standing time, undissolved chemicals etc., etc.,
If you want to correct the blisters through machine point of you,
I would suggest
1. More relaxation conveyor length
2. Rubber roller hardness where your docker pins get through the dough piece and get released normally to transfer web.(Include transfer web that is one short web of one or one half meter length of same width you supplying), where you have to remove the scrap by scrap pick up web. Thus you can give more pressure through docker pins, and get the biscuit released without any deformation and scrap lifted without any problem. I am sure this design will give you better hole in the biscuit and please remember that rubber roller hardness recommended here is 80mho. Try this in one of your equipment and tell me the result. You will get surprised.
3. More controls to have good steam in initial zone where we need to keep good humidity as in crackers we give more bottom temperature in initial zone and thus by it should not get dried out in top to develop blisters.
1. inadequate docker- increase the docker pieces, increase the docker diameter or redesign the place of docker on surface of the biscuit
2. lamination- Bad blister can be the result of poor lamination structure caused by insufficient filling dust .. improve the lamination system.
3. inadequate dough mixing: increase the mixing time to get stable dough form
4. baking profile: decrease the baking aggressive temperature profile
5. recipe: regulate the raising quantity in the recipe
Plz apply followings from equipment stand point:
In cutting apply emboss pressure a bit more as compared to normal. Also check your embosser/docker pins are ok there number is sufficient. If you are making from laminator just try increase 1 extra layer that would help as well.
In oven keep a bit low temperature in initial zones and gradually increase from other zones to bake the biscuit properly.
This I replied from equipment point of view. Apply these settings and let us share the results.