Redshifting / Postswelling DCG

[a_k]

This is how i understand the mechanisms:

Some of the internal linkages are replaced by linkages with CA/SA, which causes the swelling:

The aminoacids constituting the gelatin molecule carry positive or negative charges, which leads to an electrostatic attraction between parts with opposite charges.

One of these pairs are amino- and carboxyl (-COOH) groups. CA/SA can displace the internal (-COOH) groups from their bondage with amino groups and take their place.

In the case of DCG, mainly (-COOH) groups are involved with cross linkage. Since these groups are not available for displacement (or to a lesser degree) less CA/SA gets embedded into the gelatin molecule and thus the swelling is less pronounced.

[Sergio]

Thanks a lot Martin. I don't assume that Jeff would mind to be cited in this context.

The bottom line of Jeff's detailed explanations seems to be that:
- Citric acid allows a large colour shift but the effect disappears after a certain amount of time
- The colour shift achieved with succinic acid is less dramatic but remains (water solubility is only around 6%)
- With DCG a smaller amount of red shift is to be expected because the carboxylic groups are already used for crosslinking.

It looks like this method would not produce a large red shift with DCG. Maybe the succinic acid could be replaced with another organic acid, with similar properties but with a higher water solubility? Any ideas?

Well, verifying in the Dicarboxylic acids group we found Adipic acid as a good new candidate due the fairly water solubility, also boiling point is higher, 337.5 °C. Important that is a huge produced industrial product..

CAS number 124-04-9 , mild toxic only.