Writing in the Journal of Food Science, researchers from Purdue University, USA, found that the use of anticaking agents – additives placed in powdered or granulated materials to prevent spoilage or the formation of lumps from moisture damage – can significantly affected the chemical stability of the vitamin C suggesting that foods made with powdered vitamin C may lose the vitamin’s nutritional and chemical properties at a lower humidity than previously thought.
They reported that silicon dioxide, calcium silicate, and calcium stearate were the only anticaking agents to improve the physical stability of a powder containing sodium ascorbate – whilst none of the anticaking agents improved its chemical reactivity or tendency to degrade.
“The additives that the food industry puts in to make these powders more stable didn’t help the vitamin C, and in some cases actually made things worse,” said Rebecca Lipasek, who worked on the research.
“No anticaking agent improved the chemical stability of the vitamin, and most caused an increase in chemical degradation even if physical stability was improved,” they added.
Mauer and her team explained that although the current research focused on the stability of vitamin C, it is possible that anticaking agents could “greatly affect” other chemically labile ingredients that have a high affinity for moisture (deliquescent ingredients).
"I really thought some of those anti-caking agents would help, but they didn't," Mauer commented.
C for stability?
Vitamin C is an essential nutrient that is often fortified into foods and beverages, said Mauer and her colleagues, adding that the nutrient and is usually distributed in powdered form.
“It is often added to foods in forms such as ascorbic acid or sodium ascorbate not only for nutritional value and label claims but also for stability of the food product ... Vitamin C is [also] known to function as a preservative, antioxidant, colour fixing agent, and nutrient,” they explained.
To maintain its functionality, vitamin C must however be reasonably stable. Yet the researchers noted that many studies refer to vitamin C as one of the most unstable vitamins added to foods.
“Formulation has been shown to significantly affect moisture sorption and chemical stability of deliquescent ingredients in powder blends,” they noted, adding that as a result anticaking agents are often added to food systems to improve the physical properties and stability.
However, they noted that very little information is available on the effects of anticaking agents on both the physical and chemical stability of deliquescent ingredients.
To investigate the effects of anticaking agents on vitamin C stability, the research team blended a variety of agents – including calcium phosphate, calcium silicate, calcium stearate, corn starch, and silicon dioxide – with powdered sodium ascorbate, and exposed them to different relative humidity.
The team noted that it is normally presumed that sodium ascorbate dissolves at 86% relative humidity and is stable below that level. Some anti-caking agents, however, caused the degradation to begin at lower humidity levels, they reported.
Storage humidity, time, and anticaking agent type and ratio all significantly affected moisture sorption and vitamin C stability, said Mauer and her colleagues.
The problem, explained the Mauer, lies with the chemical properties of the anticaking agents themselves, noting that the water-repellent anticaking agents are mobile and so can clump together, leaving vitamin C exposed and susceptible to degradation.
Source: Journal of Food Science
Published online ahead of print doi: 10.111/j.1750-3841.2011.02333.x
“Effects of Anticaking Agents and Relative Humidity on the Physical and Chemical Stability of Powdered Vitamin C”
Authors: R.A. Lipasek, L.S. Taylor, L.J. Mauer