Orientador: Prof. Dr. Antonio Roberto Giriboni Monteiro

Data da Defesa: 24/03/2016



INTRODUCTION. Hydrocolloids are widely used in food industry as they have ability to retain water, are notable thickeners and gelling, have capacity of synerese controlling and stabilize emulsions. Psyllium husk and chia seed are sources of those hydrocolloids and the physicochemical  properties of their mucilage them an emerging ingredients in the manufacture of bread, cakes and desserts as substitute of fat ingredients. Some polysaccharide gels may have weak interactions that, in some cases, are strengthened by the use of mixtures of polysaccharides called mixed gels. An example is the case of dilute solutions of xanthan gum and locust beans, which do not exhibit significant shear stress, but together they do.
AIMS. This thesis aimed to investigate the chia and psyllium mucilage properties when mixed in different proportions and also to check for changes in these features when these mucilage are
extracted together.
MATERIAL E METHODS. Psyllium husk (P) and chia seed (C) from the respectively species Plantago psyllium L and Salvia hispanica L, were obtained in a local market and sent to Cereals
Technology laboratory to be storage under room temperature. The mucilage extraction consisted in an aqueous method. Temperature, time and seed/water ratio were settle based in the literature previous studies. Two different methods were used to join the mucilage: blending and combining water extraction in which the raw materials were added and extracted together. Six treatments using mucilage powders of psyllium husk (P) and chia seed (C) were prepared. The blending range was:
(T1) 100% P; (T2) 75% P, 25% C; (T3) 50% P, 50% C; (T4) 25% P, 75% C and (T5) 100% C. The combined mucilage was denominated T6. For a complete homogenization, each treatment was dissolved in distilled water, scattered using a mixer, and freeze-dried for 48 hours (-50oC). Factors such as total carbohydrate content, oBrix, pH, oil holding capacity, loss of solubility were used to investigate the mucilage interactions. The mucilage blends profile were also raised as the thermal characteristics, viscosity and the attenuated total reflection (ATR) spectra. In order to compare samples, analysis of variance (ANOVA) followed by the Tukey test allowed the distinction of the
treatments to 5% significance level. RESULTS E DISCUSSION. The aqueous extraction yield for chia, psyllium and combined mucilage were respectively 9.03% of dry chia seed mass, 47.4% of dry psyllium husk mass and 21.98% of dry chia seed and dry psyllium husk mass. The pH, oBrix and oil-holding capacity showed no significant difference between the reconstituided samples. Regarding to carbohydrates content, T5 results were significantly higher than the others. The psyllium mucilage resulted in a solubility of 6.98% (T1) while the chia mucilage was 51.26% (T5). By this fact, psyllium uses most of its mucilage to form the gel chain while chia mucilage may loss the major part of it after centrifugation. Tests conducted to conclude that the combined fraction is consistent with the individual mixed one in a proportion of 32% P and 67% C. The TGA plot of the samples showed thermal effects resembling to that of a natural hydrogel. An early endothermic loss assigned has been reported by the loss of absorbed moisture. Two stages of decomposition were observed for all samples. The first is responsible for the major breakdown of the polymer chain. The second decomposition stage is characterized by a decreasing curve up to the final temperature of 600oC. The char yield average was 38.68%. The mucilage of all treatments were found to have shear thinning properties. Three shear rate points (2.72s-1, 7.82s-1 and 14.96s-1) of the viscosity curve were compared. Once the chia mucilage concentration is raised, the viscosity has a downward trend from T1 to T5. SampleT6 presented unexpected behaviour presenting the highest viscosity value of the blends indicating thataquous combined extration acts differently than blending process. Similar ATR spectra were obtained for psyllium and chia mucilage on previous studies. In general, the bands in certain regions emerge or become more visible as it adds the different mucilage. Sample T6 did not follow the trend of the mixtures and presented in most regions similar spectra to the psyllium mucilage. Assuming that the molecular structure, among other factors, influences the properties of a polymeric gel, the ATR spectra may explain the T6 viscosity behavior above expectation since it conformation is similar to T1.
CONCLUSION. Blending chia and psyllium mucilage behaves differently than the combined extraction as the viscosity resulted of combined mucilage was higher than expected being the highlight of this work. As the industry seeks to leverage factors, such as thickening, without adding artificial ingredients, combined extraction process may prove to be interesting in this case. The ATR spectra was an important tool to investigate the causes of the increased viscosity by displaying, on the molecular level, the similarities with the highest viscosity samples structures.
Key words: hydrocolloid, TGA, DSC, viscosity, ATR.

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