Stability in Solution

Acid and oxidizing agents may hydrolyze carrageenan in solution leading to loss of physical properties through cleavage of glycosidic bonds. Acid hydrolysis depends on pH, temperature and time.

For minimum degradation during processing, high temperature short time processes are preferred. Carrageenan in solution has maximum stability at pH = 9 and should not be heat processed at pH-values below 3.5. At pH = 6 or above, carrageenan solutions withstand processing conditions normally encountered by sterilizing fish and meat products in cans as in the case of pet foods.

Effect of Acid on Gel Strength of Carrageenan at 58°C 1.2% Kappa - iota carrageenan 8.0% Sugar 0.2% Potassium citrate Citric acid
Effect of Acid on Gel Strength of Carrageenan at 115°C 1.0% Kappa Carrageenan - locust bean gum 1.0% Sodium chloride 0.5% Potassium chloride 0.7% Sodium citrate Citric acid buffer
Effect of heat treatment on Gel Strength of Carrageenan at pH = 3.6 1.2% Kappa - iota 8.0% Sugar 0.2% Potassium citrate Citric acid

The acid hydrolysis takes place only when the carrageenan is dissolved, and the hydrolysis is accelerated as the processing temperature and/or the processing time is increased. However, when the carrageenan is in its gelled state the acid hydrolysis no longer takes place.

Stability	Kappa	Iota	Lambda
At the neutral and alkaline pH	Stable	Stable	Stable
At acid pH	Hydrolyzed in solution when heated. Stable in gelled form.	Hydrolyzed in solution. Stable in gelled form.	Hydrolyzed

Reaction with other Electrically Charged Hydrocolloids

Carrageenan is a sulfated galactan being strongly negatively charged over the entire pH-range encountered in food.

Carrageenan may interact with other charged macromolecules, e.g. proteins, to give various effects such as viscosity increase, gel formation, stabilization or precipitation. The result of the carrageenan-protein interaction is highly dependent on pH of the system and the isoelectric pH of the protein. When carrageenan and gelatin are used together in a sys-tem in which the pH is higher than the isoelectric pH of gelatin, carrageenan increases the melting temperature of the gel without influencing the texture of the gel significantly.