The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts


Aya's picture


Hello everyone.
My name is Aya and I am a food technology in a major bakery.
We make golden and white bread crumbs. For over 3 years now, I have a technology problem that only the white bread crumbs get stale and even reminiscent of oxidation. the golden bread crumbs have peprika extract that Probably hiding the uncharacteristic scent cause paprika is kind of anti-oxidation.

 At first we thought it was an oxidizing scent and the direction was to test the wheat flour as it is known to contain about 1 percent of fat. We replaced the flour supplier, it helped for a while and than came back. we also replaced the yeasts but unfortunately- nothing. the smell came back.

We make bread for crumbs consisting of wheat flour, water, salt, yeast and vitamin C only.
The bread was baked in the oven and then shredded to breadcrumbs, undergoing further drying to 7-9 percent moisture. After a certain period of time, an uncharacteristic odor of the product begins to appear.
Does anyone have any idea what the unusual smell might be? It should be emphasized that the phenomenon read intermittently and it is not clear what the source is.
I would love ideas from the experts.

BaniJP's picture

A few questions to narrow down some things:

What kind of smell is it? Is it sour, rancid, moldy, sweet?

How do you dry the crumbs? Do you just let it sit until dry, do you turn them so they dry evenly?

How warm is the drying room/area? Is it well ventilated?

When does the smell occur? Immediately or after a week or longer?

And most importantly: do the crumbs taste off/can they be sold?

My first guess would be the crumbs start fermenting after some time...

Aya's picture

thanks for the reply.
We produce bread from flour, salt, water, yeast and vitamin C.
The bread is swelled and then baked. After baking, it goes into grinding and further drying to a
moisture content of up to 10.5 percent.
After drying the crumbs go into storage in a dedicated silo.
The odor develops after a certain period of time about 3 weeks after production.
And the smell is a smell that is sometimes reminiscent of oxidation and even acetone Although there is no oil
at all in the product.
We tried to replace flour, and yeast and still the problem was not solved.

BaniJP's picture

I had similar smells when I was fermenting blueberries my first guess remains that the crumbs are starting to ferment. Especially when they are just sitting in a silo (think of other grains in silos or silage). So the storage method might be the main culprit.

Maybe reduce the drying time by increasing the surface area? Or turning the crumbs over every once in a while? Basically drying them as quickly as possible...

Since fermenting is an anaerobic process, I guess they crumbs at the bottom (where there is little to no oxygen) start to ferment (and give off, sour, sometimes alcoholic smells) while the ones at the top are oxidizing...

(I know blueberries are not the same as crumbs, but thats the direction my guess comes from)

yozzause's picture

The bakery i did my apprenticeship at used to make bread crumbs from returns of unsold bread  so it was usually 2 or 3 days old it was put through a hammer mill and the crumbs were spread onto the baking sheets about 25mm deep they  were placed into the revolving ovens at the end of the day when the ovens were turned off and used up residual heat. The crumbs were very dry and cold and then tipped from the trays into a hopper for filling  containers or packs.

I presume from the fact that your doughs are made using vitamin c that they are of the instant variety that is there is no bulk fermentation.

You don't say what part of this big wide world that you are from so i'm unsure of your climatic conditions,

A big clue would be your description of the smell being even a bit like acetone, this is a smell that is quite familiar to bakers that are trying to establish their sour dough cultures and often appears in the early stages before the symbiotic harmony is established between the natural yeasts and the lactobaccilus. So i think BaniJP is correct and it could be fermentation starting up

I am inclined to think that moisture content of 10% is quite high for what is a dry product.

What size is the scale of the production and the storage silo prior to packaging. 

regards Derek


Aya's picture

Derek hi!,
this is actually a bread made especially for crumbs and it is not a mixture for immediate preparation.
We actually add flour, salt, water yeast and vitamin C to the mix and actually create bread dedicated to crumbs.

We are in Israel so in the summer the temperatures are very high, about 35 degrees Celsius.
We really noticed that the phenomenon happens mainly in the summer,
probably the high temperatures affect the processes very much.

While packing the product I do not feel a smell at all,
but after a period of 2- 3 weeks, I start getting complaints from customers about the unusual smell that is old,
a little oxidized and even today I felt a little acetone.

yozzause's picture

Interested in seeing pictures of the bread made specifically for crumbs  and the formula for the doughs and the process for handling. Also of interest would be the scale of production. Israel would have a very similar climate to us here in Western Australia  (Mediterranean)  We also experience problems with moulds in breads and quite often packaged bread develops that vinegary acetone aroma just prior to moulds developing. I can never be sure its not from the retardants that are added to try to counter such development especially in the humid summer weather.  regards Derek

Aya's picture

If this is true,
what causes them to continue to ferment?
After all, it goes through a furnace at a temperature of 220 degrees Celsius and then a drying oven
at a temperature of about 118 degrees.
After all, all the yeast and enzymes in flour are dead and destroyed at these temperatures,
so what causes the product to ferment? Could there be spores causing this?
Do you know what test you need to find out?

BaniJP's picture

Even though you kill off anything during baking and drying, as soon as you open the bag, you expose the crumbs to an uncontrolled amount of air and bacteria again. LAB (lacto acid bacteria) and yeasts are everywhere in the air, on your hands, equipment, everything. Those are not harmful though. But in addition to that, there are many other molds and bacteria that can be dangerous.
Especially with such a high moisture content and warm summer temperatures, this is basically the perfect environment for a plethora of microorganisms to grow and spread. 

The easiest two solution would probably be:

- using the crumbs before they go bad - there is a reason here in Germany every package of every food says "After opening, use within a few days"

- if you use them for longer, storing the crumbs in a cold and dark place, preferably even the fridge should slow down the bacteria. Freezing them should keep them good for even longer.

Another solution would be to lower the moisture content even further.


Aya's picture

Look, we make 2 kinds of bread crumbs in the factory.
White and gold. I would expect the golden breadcrumbs to look unusual, but not.
The complaints only come from the white bread crumbs.

The difference between the two types is that the golden bread crumbs have a paprika extract
that probably hides the bad smell.

The moisture reaches about 6-7 percent of the moisture and water activity
is normal and is within the appropriate range before microorganisms develop.
The odor can develop further in the silo and not in the packaging, that is, even before packaging.

BaniJP's picture

As long as there is any kind of moisture and a warm-ish temperature, there will be microbiological growth and activity, which eventually will lead to weird smells, no matter how and where you store it (except maybe the freezer).

I would do a couple of test batches in a controlled environment, for example:

- different moisture contents

- leave one to sit, another you turn and mix every few days and another you turn every day

Tests like that will help you narrow down the problem and you can work off the results :)

(paprika extract might be antibacterial, like you suggested. If its enough to color the crumbs golden, there should be enough to prevent unwanted bacteria and smells :)

Aya's picture

There is a very nice graph of the effect of water activity on microbiological development in the product.
To my delight, I'm not in that range. When moisture is high, water activity is high and this causes
the development of microbiology in the product.
We tested odorless products and odorless products and found no correlation between moisture and
odor appearance. What's more, in a competing product, the wetness was like my product,
and there was no smell at all. In my opinion, this is really some kind of contamination in equipment
that develops under extreme conditions like extreme heat.

I had just sent in parallel to the forum, examples of a German lab that sensorically examined the odor,
waiting for the results.