Need help with microbiological results on glucose syrup

Dear All,

I am a chemist . in my company we prepare glucose syrup of 80 brix . according to our new microbiologist if yeast is present less than 10 cfu/ g. product can be ferment because microorganism multiply time to time.is it correct .......one more thing new micro biologist test the product and found Total Plate Count=6000cfu/g and when we tested that sample with accredited external lab we received <250 cfu/g .micro biologist justified him self that after passing of time TPC will decrease due to using of whole air within the packaging material .I am not satisfied with his reply .some one expert comment on my situation?

Dear All,

I am a chemist . in my company we prepare glucose syrup of 80 brix . according to our new microbiologist if yeast is present less than 10 cfu/ g. product can be ferment because microorganism multiply time to time.is it correct .......one more thing new micro biologist test the product and found Total Plate Count=6000cfu/g and when we tested that sample with accredited external lab we received <250 cfu/g .micro biologist justified him self that after passing of time TPC will decrease due to using of whole air within the packaging material .I am not satisfied with his reply .some one expert comment on my situation?

</h3><h3> <h3>Hello Qasim Abbasi
</h3> Glucose or corn syrup with water activity below .80 will not be fermented by yeasts (i.e. with dextrose equivalent (DE) of 65 and solids of 80 % and above.

Low conversion corn syrups are likely to be spoiled by osmophilic yeasts if given enough time. Hence yeast count has to be Kept below 10 cfu /gm in final product and should be stored in dry packed condition below 30c for long shelf life until opened.


Once opened it should be consumed fast ,as being hygroscopic it will absorb moisture from air,and allow the growth of yeasts for fermentation.

However bacteria’s are normally not supported for high brix syrups as because of osmoisis,it cannot support growth.

Regarding differences in bacterial count of your companys analysis and outside lab analysis it should not vary by more than 15% deviation if both are using the same method (SOP)of total plate count/APC analysis.

If there is difference of method like you using pour plate or outside lab using spread plate than it may go wrong.

If both are using the same method of pour plate technique which is common method of analysis of APC than it should not vary much.

Errors can be in dilution factor, preparation of samples, improper weighing (product is semi-solid and hygroscopic), dissolving improperly glucose syrup in Diluent, using wrong pipettes for dilution (i.e. dispensing 1ml sample from 5 ml /10 ml pipettes instead of 1ml graduated pippete, colonies should be counted in plate of dilution which gives count in the range of 150-200 Colonies (or may be taken in duplicate/triplicate and averaged).

Higher dilution factor with fewer colonies will give large error.

Hence procedure (SOP) and sampling should be the same for supplier and user as otherwise all the specification of products of all industries will be rejected /out of control and will be unreliable.

Attaching some specification of glucose syrup

Regards

Sushil

Dear All,

Target maximum inter-lab deviation in previous post seems somewhat optimistic to me. Nonetheless the quoted difference between results is surely excessive.

Difficult to comment much on a datum of 1 x 2 points. First reaction is that "something" wrong, eg sample size / original procedure / technique, onward sample handling, external lab. procedure. Some questions need to be asked, maybe repeat analysis ?.


How about other current in-house results on similar material ? What were results like prior to change in operator ? I have no knowledge of the product / possible errors but the potential difficulty mentioned should be easily checkable - Just get some more data. And any standard procedure will surely be aware of such a practical limitation if correct. Is there a standard procedure ?

i'm impressed that you can measure the level of yeast ? what is the result ?

Rgds / Charles.C

80°Bx glucose syrup should be relatively stable microbiologically, as long as storage is good; condensation on the surface can form a dilute layer and begin fermentation by yeasts. Small numbers of yeasts are common in such products, but few can grow in those conditions of water activity & osmotic pressure.

Your differences in aerobic plate counts are large, but might be explaned by timing; high numbers at the start can reduce rapidly over time as many bacteria become non-viable quickly due to drying out. It could also be explained by sampling contamination as sugar syrups are easy to contaminate. But as Charles says, 15% difference between tests on the same sample is very optimistic; +/- 1/2 a log is common even in the same lab testing the same sample. That's microbiology for you...

Marco.