How to resolved the checking problem in rotary molded(Digestive) biscuit.
Dear Mr Basak,
It is very less chance that short dough variants like Digestive biscuits getting checking problem. Checking problem is entrapped moisture from center of the biscuit, is releasing through the biscuit radius results in checking. Mostly this happens in Hard dough variants as water is more than oil in those recipes. In short dough that too in digestive it is happening means it is because of baking profile only. If your digestive biscuit is having docker pin or not
1. Please check the baking profile. In initial zones top heat should be more than bottom heat. Here case hardening should not happen then moisture will get entrapped.
2. Please check the steam circulation in initial zones. keep maximum steam inside the oven to use more convection heat through top of the biscuit. Please keep top and bottom temperature at least 20-25*C difference should be there.
3. In middle zone 50% convection heat can be given and there after release the steam completely to get better baked biscuit through radiation and conduction heat. After middle zone increase the bottom temperature to get proper bottom colour.
4. If this setting done either you have docker pin or not biscuits will not have checking problem.
5. if 5 zones are there initial two zones keep max top heat setting, in middle zone keep 50-50 heat setting then last two zones keep bottom heat more and top heat less.
6. Pl give your feed back after setting this and baked the biscuits
Checking for rotary molder product with high level of fat and sugar is often the consequence of bad baking curve
You have two type of checking one which are immediate after cooling (but often with intermediate level of moisture) and one after 2 to 14 days which are due to rebalancing of moisture with the time. Higher is the mass of moisture to rebalance, higher is the risk. Nevertheless if cooling is too fast you increase the delta of moisture between center to surface and if cristalization effect to fast on the surface the risk of checking is here :
1 - level of moisture = if moisture is too high the risk increase but sometime could be a support to decrease delta of moisture from center to edge
2- delta of moisture = difference of moisture in the volume of biscuit : center to edge but also potentially top to bottom. If you have significant difference of color between top to bottom (without glazing effect ) you can have here a good indication of you baking quality
in consequence of oven type or bad regulation you can have also some significant difference in the width or in the time, always interesting to characterize how is the issue repartition = collect some product at the exit of oven in different area (operator side/ center/ Opposite operator side) , several time to measure the occurence of your problem to see if hazard repartition or if you have one occurence in the time or in the width
The repartition will help you to define the best way to solve
If the level is really high and permanent , try to increase the baking time
Dear Mr Basak,
The technical implication of checking is having many different factors which are more or less affecting the appearance of the relevant defect. Some of the factors are outlined below:
1. Homogenized mixing reducing as much as possible raw materials with different granulometry,
2. Addition of Oat Fibers with specific macro fiber form, aiming to maintain mosture equilibrium,
3. Increase of the docker pins in the Rotary Moulder allowing a better heat transfer,
4. Usage of the most Optimum Cooling Time allowing mositure equilibrium after baking. Normally a Cooling Time of 1,5 times the baking time. Star wheel stacking principle or penny stacker priciniple,
5. Increase of baking time allowing a better an more controlled water evaporation,
7. Manipulation of Relative Humidity in the first zones of the Tunnel Oven,
6. Maintaining the proper Relative Humidity during Cooling in order to control moisture loss during cooling,
An application of different composition of docker pins throughout product rows in the outer as well as the inner product rows has been applied in order to ease different moisture migration tendency in the Tunnel Oven.
I hope that the relevant guidelines would be helpful enough.