Effect of gamma irradiation on the macromolecular integrity of guar gum

Irradiation is becoming an increasingly important method of processing foodstuffs. Our understanding of its effects on the molecular integrity of food polysaccharides such as guar gum is however still very limited. In this study a range of techniques was used to determine absolute weight-average molecular weights and conformational parameters for a homologous series of irradiated guar gum samples. It was found that molar masses and viscosities of the irradiated samples decreased with increasing irradiation dose. However, this decrease was not linear but appeared to occur in two stages. Mark-Houwink parameters confirmed that there was no significant change in the gross conformation due to irradiation. Evaluation of the radiation yield through so-called G(seission) values gave an average value of 3.8 which is lower than expected for polysaccharides indicating some resistance to radiolytic degradation. The amount of guar gum recovered after sample work-up increased with increasing radiation dose. This suggests concentrated solution properties of guar gum are significantly influenced by non-hydrated/undissolved material.