Nanostructuring fiber morphology in 12HSA organogels and the development of a food grade organogelator

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Rogers, Michael Armin

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University of Guelph

Abstract

The non-isothermal nucleation rate of a self-assembling fibrillar network of 12-hydroxystearic acid in canola oil was found to be inversely proportional to the undercooling-time exposure of the system. Fiber growth kinetics could be modeled using the Avrami equation. Both nucleation and fiber growth kinetics displayed two distinct regimes, above and below 5°C/min. The abrupt change in the rate of nucleation, crystal growth rate constant, and the degree of branching are related to whether the nucleation and crystal growth processes are governed by mass transfer or thermodynamics. At rapid cooling rates, above 5°C/min, the driving force for both nucleation and crystal growth is the time-dependent chemical potential difference between the molten solid in solution and the crystallized solid. At low cooling rates, however, the rate of crystallization is no longer determined by this dynamic chemical potential difference, but rather only limited by time. Using the models developed and adapted in this work, we could accurately predict the fiber length, rate of nucleation, rate of crystal growth, induction time of nucleation and the degree of branching of a 12HSA SAFIN. The crystallinity and oil binding capacity of 12-hydroxystearic acid (12HSA)-vegetable oil organogels was modified by changing the post-crystallization annealing temperature from 5°C to 30°C for 24 hrs. The gels stored at 5°C had a highly branched crystalline structure with small uniform pores. At 5°C, there is an increase in supersaturation and hence the crystallographic mismatch barrier is significantly lower, increasing fiber tip branching. The nucleation-growth-branching-growth model for SAFiNs explains the differences in crystallinity, pore size and oil syneresis observed for the 12HSA-vegetable oil organogels. It was found that the gels stored at 30°C synerese 1.35 times faster than the gels stored at 5°C. Furthermore, the change in the T2 relaxations and the ratio of the complex viscosity/pore radius, which is a measure of relative oil mobility, were 1.35 and 1.30 respectively. We discovered that certain ceramides from synthetic and food sources, including milk and eggs, could gel oils very efficiently. Ceramides derived from the enzymatic conversion of sphingolipids were also demonstrated to immobilize liquid oil in an organogel structure.

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Keywords

nanostructuring fiber morphology, 12HSA organogels, food grade organogelator, canola oil, crystal growth

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