Graduation Year


Document Type




Degree Granting Department

Biomedical Engineering

Major Professor

William E. Lee III, Ph.D.

Committee Member

Leo E. Ondrovic, Ph.D.

Committee Member

Rickey S. Shelley, Ph.D.


Polymer, Stress Test, Statistical Analysis, Rheology, Molecular Weight


The properties of the aged gel and subsequent softgels were examined using mechanical and chemical testing methods. Our hypothesis was that a negligible variation will exist between the aged gel of the same type. The greater difference is expected to be seen between the types of gels described as 150 Bloom (alkaline treated collagen) and 195 Bloom (acid treated collagen).

The types of gelatin used were the acid processed (195 Acid Bone) and alkaline processed (150 Lime Bone). Because of the differences expressed as the result of their manufacture sequence (namely their molecular weights), it follows that physical attributes will further contribute to their distinction. In addition to observing different characteristics between the types of gels, we aged the gelatin and produced softgel capsules to qualify and quantify the changes that occur as a function of time. Two production lots of over 1 million softgel capsules were executed to produce a population that lends itself to statistical analysis. Softgel capsules were manufactured with gelatin which was aged at intervals of 0-8 hrs, 32-40 hrs, 66-72 hrs and 88-96 hrs. The manufacturing process made use of this strategy for the acid and alkaline treated gelatin where a total of eight lots were made (4 acid and 4 alkaline). One hundred thousand softgels were manufactured for the acid processed gelatin, per lot. Additionally, one hundred and fifty thousand softgels were manufactured for the alkaline processed gelatin per lot.

The results of the different tests provided trends that were not solely a function of time. Gel extensibility for both gel types showed a decrease in the amount of force needed to rupture the gelatin ribbon, as a function of time. The resilience of the tested ribbon remained constant throughout the aging process. The burst strength was the only test showing an inverse relationship between the two gel types. The amount of force needed to rupture the 150 Bloom softgels decrease in time whereas the amount of force needed to rupture the 195 Bloom softgels increase with time. The rheological testing was described in the literature as being associated with the molecular weight distribution. Such association was seen in our research and both the results of the rheological and the molecular weight tests decreased with the aging process.