Publicação
Importance of the rheological evaluation in the technological development of medicinal extracts
| Resumo: | The main goals of this work were to characterize the rheological behaviour, time-dependency, ageing and temperature effect on the liquorice, German chamomile and hawthorn extracts; describe the flow behaviour of two probiotic yoghurts (one containing Bifidobacterium spp. and the other Lactobacillus casei) and characterize the rheological effect of the addition of liquorice, German chamomile and hawthorn extracts to those yoghurts. A Brookfield digital viscometer, model DV-II+ was used in the rheological measurements. The medicinal plants were successfully extracted until exhaustion at room temperature, using the adequate extractive solutions. Each probiotic yoghurt was enriched with different amounts of the medicinal extracts, so as to obtain in the end, for each yoghurt/extract pair, five different samples. Prior to the rheological assays, preliminary physical and chemical tests were conducted in order to better characterize the medicinal plants and the probiotic beverages. Experimental data showed that the three extracts exhibited a non-Newtonian, rheo-thickening behaviour, with time dependency for two of them (German chamomile and liquorice). As far as the ageing effect is concerned, the viscosity of the liquorice and the German chamomile extracts increased with storage time, while the hawthorn’s suffer no significant change in its apparent viscosity. As expected, the increase in the temperature resulted in a decrease of the apparent viscosity of the three extracts. Arrhenius model was used to describe the dependence of the viscosity on the temperature. Hawthorn had the highest activation energy value (16.27 kJ mol-1), while the German chamomile had the lowest (3.96 kJ mol-1). As far as the probiotic beverages are concerned, all of them exhibited shear-thinning behaviour. The yoghurt containing Bifidobacterium spp., showed a better suitability for the incorporation of the medicinal extracts. The results obtained may thus contribute for the development of probiotic beverages enriched with medicinal plants extracts. |
|---|---|
| Autores principais: | Caetano, João Pedro Valente Rodrigues da Silva |
| Assunto: | Liquorice Chamomile Hawthorn Probiotics Lactobacillus spp. Bifidobacterium spp. Functional foods Rheology Non-Newtonian Shear-thickening Shear-thinning Thixotropy Anti-thixotropy Mestrado Integrado - 2013 |
| Ano: | 2013 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso restrito |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | The main goals of this work were to characterize the rheological behaviour, time-dependency, ageing and temperature effect on the liquorice, German chamomile and hawthorn extracts; describe the flow behaviour of two probiotic yoghurts (one containing Bifidobacterium spp. and the other Lactobacillus casei) and characterize the rheological effect of the addition of liquorice, German chamomile and hawthorn extracts to those yoghurts. A Brookfield digital viscometer, model DV-II+ was used in the rheological measurements. The medicinal plants were successfully extracted until exhaustion at room temperature, using the adequate extractive solutions. Each probiotic yoghurt was enriched with different amounts of the medicinal extracts, so as to obtain in the end, for each yoghurt/extract pair, five different samples. Prior to the rheological assays, preliminary physical and chemical tests were conducted in order to better characterize the medicinal plants and the probiotic beverages. Experimental data showed that the three extracts exhibited a non-Newtonian, rheo-thickening behaviour, with time dependency for two of them (German chamomile and liquorice). As far as the ageing effect is concerned, the viscosity of the liquorice and the German chamomile extracts increased with storage time, while the hawthorn’s suffer no significant change in its apparent viscosity. As expected, the increase in the temperature resulted in a decrease of the apparent viscosity of the three extracts. Arrhenius model was used to describe the dependence of the viscosity on the temperature. Hawthorn had the highest activation energy value (16.27 kJ mol-1), while the German chamomile had the lowest (3.96 kJ mol-1). As far as the probiotic beverages are concerned, all of them exhibited shear-thinning behaviour. The yoghurt containing Bifidobacterium spp., showed a better suitability for the incorporation of the medicinal extracts. The results obtained may thus contribute for the development of probiotic beverages enriched with medicinal plants extracts. |
|---|