Writing in the August issue of the journal Food Research International​, T. Yu et al. outlined a method that involves entrapping high pressure gas inside the pores of spray dried soluble coffee by cycling pressure and temperature.

The method, originally developed by Kraft Foods (US 2006/0040038 A1 – Foaming Soluble Coffee Powder Containing Pressurized Gas), was evaluated for its ability to modify aroma delivery.

The release of pressurized gas on hydration caused, in the scientists’ words, “a burst of volatile aroma compounds into the headspace”.​

This was both faster (77%) and more intense (60%) than could be achieved using standard instant coffee or by using chemical effervescent agents such as sodium hydrogen carbonate or citric acid, they explained.

The process of natural gasification also increased the delivery of individual aroma compounds such as 2,3 butanedione and acetaldehyde during hydration.

According to Yu et al: “Natural gasification…allows effective gas entrapment and modification of aroma delivery…’​

“[It] not only alters the maximum headspace gas concentration (intensity), but also allows a degree of control over the temporal release dimension (time to maximum aroma headspace intensity) of the individual aroma compounds.”​

Dissecting the coffee occasion…​

Discussing the experience of drinking soluble coffee, the team said that ‘sensory modalities’ included mouthfeel, hydration, physiological response, taste and aroma.

They dissected aroma into specific consumer experience points: (1) opening the jar (2) mixing the dried powder in the cup with water (3) orthonasal perception of the drink after preparation (4) retronasal perception of the beverage on consumption.

“All the different stages play varying roles in perception, and crucially, all play a different role in distinguishing products, brands and roast and ground coffee from instant coffee,” ​the team wrote.

Nonetheless, they picked out point 2 (above) as a “often overlooked critical point of consumer differentiation between roast and ground coffee and instant coffee”​

Entering the ‘coffee matrix’​

The scientists exposed the spray dried powder to elevated pressure whilst heating it beyond its ‘transition temperature’, at which point they said that the ‘coffee matrix’ became more permeable to pressuring gas that was internalized within the powder.

Adding water to the powder led a rapid increase in gas mobility through the matrix, they added, with the material moving from a “rigid glassy”​ to a “softened rubbery state”​, while the internalized gas was released into the hydrating medium.

It would either rise to the surface and be released or form a surface cream, Yu et al. wrote, while on its release it affected the coffee by increasing the dissolution of carbohydrates and volatile aroma compounds.

Such new flavour delivery tools would provide product developers with a new approach to product formation and allow greater flexibility when approaching reformulation challenges, the team added.

Title: ​‘Aroma delivery from spray dried coffee containing pressurized internalized gas’

Authors: ​T.Yu, B. Macnaughtan, M.Boyer, R.Linforth, K.Dinsdale, I.D Fisk

Source: ​Food Research International ​(2012), doi: 10.1016/j.foodres.2012.08.021​