Interação entre caseína micelar e nanoblendas de polidiacetileno/copolímeros triblocos (EO)n-(PO)m-(EO)n

• Autor(a) principal: Souza, Luana Cypriano de
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2944
• topic: Nanotecnologia; Leite; Proteínas; Sensores; Nanotechnology; Milk; Proteins; Sensors; CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::CIENCIA DE ALIMENTOS::QUIMICA, FISICA, FISICO-QUIMICA E BIOQUIMICA DOS ALIM. E DAS MAT.-PRIMAS ALIMENTARES

Polydiacetylene are conjugated polymers with great potential for use as colorimetric sensors because exhibit unique properties polymers. However, dairy systems are complex matrices and constituents present in these foods can interfere in colorimetric transition of these sensors. This study aimed to determine and assess the driving forces involved in the intermolecular interactions between micellar casein and nanoblends of polydiacetylene (PDA) and triblock copolymer (TC). Nanoblends (NB) composed of polydiacetylene molecules (PDA) and triblock copolymers (TC) were synthesized. Different concentrations of micellar casein suspension (CM) were added in sensor suspensions. From analysis of UV-vis spectroscopy was possible to verify that the suspension of CM induced color transition from blue to red, when added to the PDA/L64 nanoblends in a certain concentration range (5.10-4 a 3.10-3 μmol-1). However, the maximum colorimetric response (CR) achieved did not exceed 90%. For the concentration of TC L64 (0.1%, w/w) the colorimetric transition of nanoblends was reduced to 40%. However, the behavior was similar to nanoblends containing 1.0% and 2.0% (m / m) of L64 and thus, we chose to work with L64 concentration equal to 1.0%. However, the behavior was similar to nanoblends containing 1.0% and 2.0% (m/m) of L64 and thus, we chose to work with L64 concentration equal to 1.0%. When nanoblends were separated from the MC suspension by dialysis membrane was obtained almost the same behavior that is a maximum RC around 90%. However, when the dialyzed micellar casein (DMC) for five days was added to the nanoblends suspension the maximum RC obtained was around 20% and after seven days of dialysis RC was approximately equal to zero. The size and zeta potential of nanoblends increased with increasing concentration of CM, from 50 to 140 nm and -28 to -20 mV, respectively, showing that the interactions between NB and MC occur predominantly in the surface region of the nanostructures. From this concentration there was an abrupt increase in enthalpy of interaction varying from -15 to 150 kJ.mol-1. Coincidentally, the RC was detected in the same concentration range where the abrupt change of enthalpy of interaction occurs. This result demonstrates that MC without calcium phosphate interacts with nanoblend releasing energy, not absorbing enough to overcome the conformational barrier and promote the colorimetric transition energy. The effect of hydrophilic/hydrophobic balance of TC was evaluated by substitution of TC L64 by F68 and was observed that at lower concentrations of MC (2.0 x 10-3 mol.L -1 ) there was higher RC in nanoblends PDA/F68. However, since this concentration the PDA/L64 nanoblends were more sensitive to the presence of CM, with a CR maximum 10% greater than for PDA/F68 nanostructures. When molecules that interact with MC, as K- carrageenan (k-CAR), were added to nanoblends we observed a decrease in the RC of about 20% compared to pure NB PDA/L64. Several factors may affect the CR of this nanosensor as MC concentration, salts released from the MC, hydrophilic/hydrophobic balance of TC and the presence of other molecules in the middle. Thus, these results may in future contribute to the development and application of sensors based on PDA/TC nanoblends for dairy foods.