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Asked on 01.12.2020.

Rancidity in hard sweet laminated biscuits

Recently, we have noticed some degree of rancidity in Maria biscuits. Dough fat melting point is 42º C, but sometimes bulk fat arrives at 67ºC from supplier, when I believe that it should be maximum 55ºC. Besides that, could line belts and equipment condition be a cause, too? 


Accepted answer
Answered on 02.12.2020.

Dear Jose,

Apart from the reason already mentioned by our experts, there are other reasons also to get rancid quickly.  If this happening very recently then please check up your wheat flour germ oil acidity and content.  If it is higher than standard and your Marie biscuit moisture also high then there are chances that you get rancid smell.  Because in Marie biscuit Wheat flour quantity is high and fat also not very much.  

As you mentioned in your question, the quality of hygiene, machine condition, baking quality, storage, if any problem in packing machine,  storing of naked biscuit until it get packed are the factors to be taken care too.

Answered on 22.12.2020.

Hi Jose Carlos!

In fact, I have very seldom seen sweet biscuits rancid, because normally sugar has an anti oxidative effect. If the biscuit gets rancid the reason comes from one of the raw materials used as explained in the answers already given. Either the fat comes already with a high peroxide index or the tanks in which the fat are not cleaned regularly or, or etc.

If the rancidity is oxidative look for the culprit in the raw materials, if the rancidity is hydrolytic look for bad protection in the packaging, as it sometimes happen in crackers.

I remember testing a quite rancid sweet biscuit which was left a lot of time in a storefront under the sun rays.

Answered on 01.12.2020.

Hi Jose Carlos!

Besides measuring the melting point of your fat, you should be measuring the saponification index and the peroxide index, because those two elements will tell you about the presence of hydrolytic rancidity and oxidative rancidity.

You should agree with your supplier about these two indexes which are more important than the melting point in determining rancidity.

Apart from these two fundamentals you should agree with the supplier about the use of inhibitors of rancidity like rosemary extract or BHT or BHA.

Theoretically if the fat has a higher melting point it has less opportunity of becoming rancid.

Answered on 01.12.2020.

Hi José Carlos,  

Along with all the care suggested by other colleagues, I suggest you to pay special attention to the way you are storing fat. Try to clean storage tanks at every 6 months, or at most at every year, exhausting, cleaning and washing the tank and the piping, in order to deplete and eliminate all traces of old fat. Because if you store new fat over old fat, there will always be traces of oxidized fat remaining. As the oxidative reaction occurs on an exponential scale, problems can be observed in a relatively short period in the final product or even in the storage tanks. As the oxidative reaction occurs on an exponential scale, problems can be observed in a relatively short period in the final product. When doing fat analysis, compare the analysis of samples collected from the supplier bulk, with fat samples collected from the factory's storage tank. I hope I helped you. Kind regards

Answered on 02.12.2020.
Is it possible to ask your supplier to deliver the fat between 55-60°C.
I assume your fat is palmoil based fat. That is OK but it should not been contaminated with liquid oils. This you can check with the fatty acid comosition, which you can ask your supplier.
Liquid oils can lead quicker to oxidation and so to rancidity.
Answered on 21.12.2020.

Thanks for the answers so far. Do you know if hard sweet biscuits tend to be  more susceptible to oxidation for some reason? Higher baking temperature profile or higher dough temperatures? More layers in lamination (thus more space for air), could also be a reason, or any other? We have been using this fat for quite some time now, and it has not been an issue previously.  The problem occurs mainly in laminated hard sweet biscuits, but also in crackers at a lower range.


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