12 January - 20 June 2016

Reducing the high viscosity of an EFSA approved weight management ingredient so it can be used in food

Research published in the journal Food Hydrocolloids has found that blending konjak glucomann, a soluble dietary fibre with extraordinarily high water-holding capacity, with chitosan, a pH-sensitive biopolymer, could be added to foods to help consumers feel fuller for longer. Konjac glucomann (KGM) is the only EFSA approved ingredient for weight management.

Research published in the journal Food Hydrocolloids has found that blending konjak glucomann, a soluble dietary fibre with extraordinarily high water-holding capacity, with chitosan, a pH-sensitive biopolymer, could be added to foods to help consumers feel fuller for longer.  Konjac glucomann (KGM) is the only EFSA approved ingredient for weight management.  The water holding capacity means that KGM swells in the stomach, providing a satiety sensation.  Due to its high viscosity it is unable to be added to foods at levels beneficial to health.  Various strategies have been used to try and reduce the hydration of KGM, although whilst they limit KGM swelling in aqueous solution, scientists need to ensure that KGM develops a high viscosity in the stomach in order to promote satiety sensation.

In this current study Lopez-Rubio et al investigate whether combining KGM and chitosan may be a solution by examining characteristics such swelling behaviour and the formation of interpenetrating hydrocolloid networks (IHNs – are blends of different hydrocolloids which interact with each other simply by being mixed rather than through ionic or chemical linkages).  

The team prepared different ratios of KGM and chitosan (90:10, 75:25 and 50:50) with either low molecular weight chitosan (LCh) or high molecular weight chitosan (HCh) to create 6 different blends.  Using the blends, the scientists created films, half of which were neutralised using sodium carbonate and half used as is, as a reference. The films were then tested in both neutral and simulated gastric conditions (pH 3).  Lopez-Rubio et al. report that the non-neutralised films were unstable at both pH’s whilst the neutralised films were stable in the neutral solution, although the amount of water absorbed depended on the ratio of KGM:chitosan and also the molecular weight of the chitosan.  Swelling significantly decreased with chitosan content and was greater for the blends with HCh.  All films were unstable in the acid contents except the neutralised films with the highest contents of high Mw chitosan.  They state that these types of structure “could be excellent candidates for the development of satiating ingredients that are able to swell in the stomach but not in neutral food matrices.” 

The team then prepared freeze dried particles and again half were neutralised using sodium carbonate.  The particles were prepared with the aim they could be treated as food ingredients. To understand how the particle’s viscosity would change in a simulated gastric condition, the flow consistency index of each freeze-dried materials was obtained by rehydrating then in a neutral buffer solution or simulated gastric solution.   The team found that when freeze drying KGM:Ch solutions contained sodium carbonate, the blends with higher KGM content displayed better reactions to pH.  They note that the salt seems to be involved in “inter- and intramolecular interactions.”  They conclude by stating that “these compositions are promising candidates for the development of satiating ingredients”. 

RSSL's Product and Ingredient Innovation Team, has considerable expertise in developing a wide range of food and drink products at a laboratory and pilot scale.  For more information please contact Customer Services on +44 (0) 118 918 4076 or email enquiries@rssl.com

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