Maltodextrin will kill all the bacterial cells? - (Jan/20/2014 )

Dear all researchers, 

I would like to seek for your advice. I was gained a strange result of my research study. I have prepared the sample mixture as follows:

1) probiotic culture

2) probiotic culture+maltodextrin

3) probiotic culture + Fructooligosaccharides (FOS)

4) probiotic culture X FOS + maltodextrin 

All the samples were incubated at 70C for 2 hours and follow by CFU count. Result as below:

Without 70C incubation

1) Probiotic culture : 2 x 10^-12 CFU

2) Probiotic culture + maltodextrin:5 x 10^-12 CFU

3) Probiotic culture +  FOS: 8 x 10^-11 CFU

4) Probiotic culture + FOS + maltodextrin: 8 x 10^-12 CFU

After 70C incubation

1) Probiotic culture: 2 x 10^-11 CFU

2) Probiotic culture + maltodextrin: 0

3) Probiotic culture + FOS: 1 x 10^-11

4) Probiotic culture + FOS + maltodextrin: 0

Did anyone know why the probiotic cells were not able to survive after incubate at 70C with the presence of maltodextrin? Is there any possibilities that high temperature will alter the maltodextrin's properties which will kill all the bacterial cells. 

Thank you. 

Perhaps a problem with osmotic concentration?

What maltodextrin concentration do you use?

It could be due to an osmolarity increment as hobglobin says. Polysaccharides are hydrolysed at high temperatures and maltodextrin is not more than a polymer of glucose. You can test that measuring free glc in the maltodextrin solution before and after treatments, probably is the easiest way to measure it indirectly... well, probably is not that "you can" but maybe "you should" do it as a control. Just do it in the maltodextrin solution and/or in the solution + medium.

By the way, if the pH of the mix before heat-treament is not neutral, the hydrolysis effects will be enhanced and if the treatment is not performed in sealed tubes, the lose by evaporation may enhance the osmotic effects in case that this is what happens

Thanks for the info! According to the ratio, concentration of maltodextrin is 60%. I agree with you and Hobglobin, majority of bacteria will not able to survive when sugar concentration more than 50%. 

Do you think spray dry technique will help to prevent this problem since it is rapidly spray out the powder at high temperature? Please advice. Thanks.

Well, I'm not sure what do you want to achieve but definitely at 70° C any sprayed aqueous solution will dry very fast.

In any case I'm not sure if the hydrolysis really happens during the process, I don't know how thermally stable is the maltodextrin but if spraying works go for it.

Dear all, 

I was repeated the same experiment by reducing the temperature to 40 degree, however there is still no bacterial cells manage to survive after incubated together with maltodextrin. Do you think 40C will cause hydrolysis?