Banca de DEFESA: REBECCA BARBOSA SILVA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : REBECCA BARBOSA SILVA
DATA : 13/02/2020
HORA: 13:00
LOCAL: INSTITUTO DE ZOOTECNIA DA UFRRJ
TÍTULO:

Variations of goat milk protein fractions and association with the properties of PVA / Casein / Pluronic nanofibers. 

PALAVRAS-CHAVES:

Goats; Milk Protein; Nanomaterials.

PÁGINAS: 124
GRANDE ÁREA: Ciências Agrárias
ÁREA: Zootecnia
SUBÁREA: Produção Animal
RESUMO:

 

SILVA, Rebecca Barbosa. Variations of goat milk protein fractions and association with the properties of PVA / Casein / Pluronic nanofibers. 2020. 125p. Tesis (Doctoral degree in Animal Science). Instituto de Zootecnia, Universidade Federal Rural do Rio de Janeiro, Seropédica, RJ, 2020.

 The characteristics of nanofibers containing milk proteins depend on the chemical composition of the milk used to produce it. In goats, the genetic polymorphism in the CSN1S1 locus, which encodes α_S1-casein, generates variations in milk protein fractions, in the conformation of casein micelles, and in the structure of dairy derivatives. In the first experiment, we aimed to evaluate the physical-chemical and mechanical characteristics of the nanofibers of PVA, goat casein and Pluronic produced by electrospinning. The treatments tested were the inclusion levels of casein (10%, 15%, 20%, 25% and 30%) in the nanofiber composition. A completely randomized design (DIC) was used, with three replicates (scaffolds) per treatment, totaling 15 experimental units. The mean values of the variables fiber diameter (µm), breaking force (MPa), Young's modulus (MPa/mm²), degree of crystallinity (%), degradation temperature (ºC), glass transition temperature (Tg) (ºC), crystallization temperature (Tc) (ºC) and melting temperature (Tm) (ºC) were analyzed using regression analysis by the SAS statistical program (Statistical Analyzes System, 1998). The results of the spectrometry analysis in the infrared region with Fourier transform (FT-IR) were analyzed qualitatively. In all treatments it was possible to produce nanofibers, which presented a homogeneous structure except for the proportion of 30%, which presented a structure in the form of beads. The fiber diameter was significantly (P<0.05) affected by the inclusion of casein. FT-IR proved the presence and interaction of the components in the nanofiber. X-ray diffraction (XRD) demonstrated a reduction in the crystallinity of nanofibers with the increase in the inclusion of casein in the solutions. Thermogravimetric analysis (TGA) demonstrated that the material can withstand temperatures up to 272.8 ºC. Differential scanning calorimetry (DSC) showed a decrease in Tg in samples with higher levels of casein inclusion. There was no Tc in the treatments 25% and 30%. In the second experiment, we aimed to evaluate the physical-chemical and mechanical characteristics of nanofibers produced by electrospinning with PVA, Pluronic and caprine casein, which presents variations in the primary structure of amino acids due to the polymorphism observed in the CSN1S1 locus. The tested treatments were the genotypes (AA, AF, EE and EF) in the composition of the nanofibers. A DIC was used, with four repetitions (scaffolds) per treatment, totaling 16 experimental units. The observed variables were similar to the first experiment. For the analysis of the variables, the Duncan test was used by the SAS statistical program (Statistical Analyzes System, 1998). FT-IR spectra were analyzed qualitatively. In all treatments, it was possible to produce nanofibers, which showed a heterogeneous structure, without counting in treatments AA and AF. The diameter of the fibers was significantly (P<0.05) affected by the genotypes. FT-IR demonstrated more pronounced absorbance peaks in AA and EE genotypes. XRD showed a significant difference (P<0.05) between treatments, with a higher degree of crystallinity in AA treatment. The TGA indicated degradation temperatures above 238.36 ºC for the material. The DSC demonstrated two peaks for Tg, Tm and Tc, with a significant difference (P<0.05) for Tm 1. It is concluded that the genotypes, by altering the primary structure of proteins, alter the physical-chemical characteristics of nanofibers.

MEMBROS DA BANCA:
Externo à Instituição - MARCOS LOPES DIAS - UFRJ
Externa ao Programa - 1051901 - MARINA MORTATI DIAS BARBERO
Externo à Instituição - PAULO HENRIQUE DE SOUZA PICCIANI - UFRJ
Interno - 2142739 - RODRIGO VASCONCELOS DE OLIVEIRA
Presidente - 1899630 - VINICIUS PIMENTEL SILVA