Vitamin Degradation
I ate a nutrition bar today. Nevermind that the line between nutrition bar and cookie is sometimes rather thin. This bar packed a punch - 35% daily value of vitamin A, 50% of vitamin C, 100% of vitamin E, and 50% of vitamin B6. At least, that's what the label says.
How much vitamin C I actually got is less clear. While food products languish on the shelf, they lose vitamins. Vitamin C is a classic example - the molecule oxidizes in the presence of air rather quickly. The two largest influencers on the reaction rate for vitamin degradation reactions take place are temperature and water activity.
As with most other reactions, vitamin degradation increases with increasing water activity. The speed with which vitamins degrade depends on both which vitamin we're talking about, and the specifics of your product. Here's how you test your product to determine its susceptibility to vitamin degradation:
Materials: You'll need your product (preferably formulated at different water activity levels), a temperature controlled chamber, a water activity meter, and test kits for measuring vitamin concentrations.
- Use water activity meter to measure the water activity of each sample.
- Measure concentration of vitamin in samples
- Store samples under abuse conditions, preferably at different temperatures
- Measure concentrations of vitamin under investigation at different time intervals
- Use Clausius-Clapeyron equation to calculate shelf life under ambient conditions