Proper dispersion and solubilization are critical to ensuring proper functionality of gelatine. Regardless of your application, proper dissolution begins with swelling.
Gelatine is able to absorb five to 10 times its own weight of cold water. The time required to absorb this quantity of water varies with particle size of the gelatine.
Small particles, < 0.08mm, typically swell completely within minutes
Medium particles, 0.80mm - 2.00mm, usually require approximately 10 minutes
Large particles, > 2.00mm, will require an hour or more
Solvent composition will also affect the rate of swelling.
Citric, acetic, or tartaric acids will reduce swelling time
High levels of solids, sugar or salt for example, will increase swelling time
Solubilization
Although completely swollen, gelatine is only partially soluble at temperatures below 40ºC. Increased heat facilitates solubilization, but can adversely affect gelatine functionality if not monitored and controlled. Gelatine solution held at 60ºC for two hours, for example, can exhibit a 5% reduction in gelling power. Such losses are increased with extended time, or under acidic or alkaline conditions. Temperatures in excess of 100ºC should be avoided as short exposure times can cause substantial losses of functionality.
High and Low Percentage Gelatine Solutions
Dissolution of very low or very high concentration gelatine solutions can be facilitated using specific dissolution protocols.
High concentration gelatine solutions - 20% to 40% gelatine
Use only large/coarse particle gelatine. (Fine particles absorb water very quickly, leading to lumps that are difficult to dissolve.)
Quickly disperse coarse gelatine into water with sufficient agitation to ensure complete wetting of all particles. Stop mixing when all water is absorbed to avoid the induction of air. Allow mixture to sit until completely swollen.
Place mixture in a 60º-70ºC water bath. To minimize induction of air, do not begin mixing until most of gelatin is solubilized. If air is incorporated, the solution can be degassed by allowing it to stand (without mixing) at a maximum temperature of 60°C for up to two hours.
Low concentration gelatine solutions -up to 15% gelatine
Gelatine solutions with a concentration of up to maximum 15% can be prepared according to the method described above. However, because lower concentration solutions contain a larger quantity of free water, the dissolution process can be reduced using either of the following processes
PROCESS 1
i. Disperse the entire quantity of gelatine into half of the required quantity of water and allow it to swell sufficiently.
ii. Boil the remaining water, and add it while stirring to the swelled gelatine solution. Continue stirring until the gelatine is completely dissolved.
PROCESS 2
i. Under vigorous agitation, slowly pour gelatine into hot water (80°- 90°C).
ii. Continue stirring until gelatine is completely dissolved. Undesirable lumps can occur if the gelatine is added too quickly or if stirring is carried out too slowly.
iii. Prepared solution should be cooled as quickly as possible to 60°C in order to prevent loss of gelling capacity.