But the scientists based at the University of Reading and the University of Nottingham said that their results, published in Food Chemistry, would suggest that, although pressure treatment may enhance overall consistency of the gums, it cannot be used to convert, in rheological terms, a ‘bad type’ gum into a ‘good type’.
The authors maintain that the use of HPP as a possible alternative processing method to thermal treatment has brought about the need to study the pressure behaviour of macromolecular food ingredients such as proteins and polysaccharides.
And, to date, they argue that there has been little research published regarding the effect of this treatment on the physical properties of gum arabic, which is commonly used in food formulation and can prevent sugar crystallisation in confectionery.
The study
To evaluate the combined effects of HPP and various pH conditions on the rheological profiles of two different gum types, the researchers looked at a ‘good’ grade gum arabic, described as KLTA, which was a spray-dried preparation of Kordofan gum, sometimes described as ‘light type’ due to its pale colour.
They said the ‘poor’ gum, GCA, was again a spray-dried preparation but derived from a colour-sorted gum fraction known as gum combretum, which, the authors added, is usually regarded as having inferior rheological and emulsifying properties.
The researchers explained that the effect on the viscoelastic behaviour of pressure-treating hydrated gum arabic samples (800 MPa) at different pH values (2.8, 4.2 and 8.0) was investigated, using controlled stress rheometry.
Approximately 25 ml of gum solutions, in either deionised water or buffer, were sealed in plastic bags made from polyethylene and then subjected to 800 MPa pressure for 10 minutes, with the temperature in the pressure cell kept at between 27° and 30°C by circulating cold water, notes the article.
And, continued the authors, the treated samples were analysed for their complex, storage and loss moduli as a function of frequency, using dynamic oscillatory testing.
“HPP treatment of gum arabic solutions resulted in a ‘stronger’ viscoelastic structure for both the ‘good’ and the ‘poor’ quality gums when compared to the native (unpressurised) samples,” found the researchers.
But the authors note that while both grades of gum increased in terms of their consistency they retained their essential differences post HPP, with the ‘good’ gum still more gel-like at the low frequencies.
More specifically, HPP treatment enhanced the overall dynamic moduli in the ‘good’ quality, KLTA gums over and above any enhancement seen in the ‘poor’ quality, GCA gums, they found.
The UK scientists concluded that while pressure treatment alone does not convert a ‘bad gum’ profile into that of a ‘good’ gum, it can be used increase the overall consistency of a poor grade gum to that of a native ‘good’ gum.
Source: Food Chemistry
Published online ahead of print:
Title: Effect of high-hydrostatic pressure and pH on the rheological properties of gum arabic
Authors: A.G. Panteloglou, A.E. Bell, F. Mab