Chip makers can slash sodium by reducing salt crystal size, say researchers

29-Sep-2013 - Last updated on 30-Sep-2013 at 15:00 GMT

Sodium concentration in the saliva and saltiness perception were both higher when smaller salt crystals were used on the potato chips

Smaller salt crystals give a faster, more concentrated perception of saltiness in potato chips, offering a viable sodium reduction strategy, researchers say.

Published in the Journal of Texture Studies, the study analysed the impact of different size salt crystals on in-mouth delivery of sodium and saltiness perception in potato chips.

Findings showed that manufacturers could achieve a greater maximum saltiness per unit of sodium if smaller salt crystals are used.

“The smallest crystal size fraction dissolved and diffused throughout the mouth to the tongue saliva faster than the medium and the largest ones; the smallest crystal size fraction also had the highest maximum concentration and greatest total sodium,” the researchers from the University of Nottingham, UK wrote.

“These results correlated well with the sensory perceived saltiness, where the smallest crystal size fraction resulted in the fastest, highest maximum saltiness intensity and maximum total saltiness,” they added.

Researchers said that modification of salt crystal size is therefore a viable approach to reducing sodium in crisp snacks.

Saliva sodium levels and perceptions

The research involved a trained panel that were asked to chew the potato chips in a defined protocol – three times before leaving on the tongue for 65 seconds.

The sodium concentration of the saliva was then measured and the sensory perception of saltiness recorded over the 65 seconds by each panellist.

Findings showed higher sodium levels in the saliva within a shorter time-span for smaller salt crystals. Researchers said this could be a result of the increased surface area facilitating a more rapid dissolution.

In terms of saltiness perception, the researchers said that among the differing responses, there was a curve shape trend across the board where panellists recorded a maximum saltiness that then dropped off as time went on.

Hurdles to overcome…

While the researchers flagged used of smaller salt crystals as a viable sodium reduction strategy, they did acknowledge technical and sensorial hurdles.

There are limitations in processability, they said, and also changes in the time-intensity profile when it comes to salt perception.

They said that while use of smaller salt crystals results in maximum salt perception, there is a much more rapid loss of saltiness after chewing.

“But the results do demonstrate that enhanced dissolution and diffusion kinetics can be achieved through modification of salt crystal size, which should be seriously considered by snack food manufacturers when approaching product reformulation,” they said.

The study also found that the adhesion of smaller salt crystals to potato chips was better. “The ground fractions gave a broader distribution across the crisp surface, whereas the larger crystals had a more inhomogeneous distribution,” the researchers said.

Industry has already started working on adapting salt crystal size for sodium reduction. One example is Tate & Lyle's now patented technology which uses smaller crystals of hollow sodium chloride particles to enable manufacturers to cut sodium levels. Morton Salt in the US also offers different particle sizes of its sodium reduction products, among others.

Source: Journal of Texture Studies
Published online ahead of print, doi: 10.1111/jtxs.12017. In print, October 2013, Volume 44, Issue 5, pages 338-345
“Impact of salt crystal size on in-mouth delivery of sodium and saltiness perception from snack foods”
Authors: R. Rama, N. Chiu, M. Carvalho Da Silva, L. Hewson, J. Hort and ID. Fisk