Authors:G. Fontanari, J. Batistuti, G. Bannach, I. Pastre, E. Ionashiro, and F. Fertonani
The guava seed protein isolate (PI) was obtained
from the protein precipitation belonging to the class of the gluteline (Ip
4.5). The conditions for the preparation of the PI were determined by both
the solubility curve and simultaneous thermogravimetry-differential thermal
analysis (TG-DTA): pH 11.5, absence of NaCl and whiteners and T=(253)C.
Under these conditions a yield of 77.00.4%, protein content of 94.20.3,
ashes 0.500.05% and thermal stability, T=200C,
were obtained. The TG-DTA curves and the PI emulsification capacity study
showed the presence of hydrophobic microdomains at pH 11.5 and 3.0 suggesting
a random coil protein conformation and, to pH 10.0, an open protein conformation.
The capacity of emulsification (CE), in the absence of NaCl, was verified
for: 1 – pH 3.0 and 8.5, using the IP extracted at pH 10.0 and 11.5,
CE≥3435 g of emulsified oil/g of protein; 2 – pH 6.60 just
for the PI obtained at pH 11.5, CE≥1408 g of emulsified oil/g of
Authors:G. Fontanari, G. Souza, J. Batistuti, V. Neves, I. Pastre, and F. Fertonani
Glutelin, the major protein fraction from guava seed, was obtained by fractioning as described by Osborne. The total proteins
were extracted and the isolates obtained by isoelectric precipitation presented similar DSC curves, concordant with the results
obtained by gel filtration chromatography and electrophoresis in polyacrylamide gel (PAGE-SDS). However, the DSC curves showed
a higher enthalpy with regard to the denaturing protein isolate (PI) extracted at pH 10.0 when compared to a PI at pH 11.5.
Such results are in accordance with those obtained for PI extracted at pH 10.0 using chromatography, this one being present
in the form of molecular aggregates of greater molecular mass. The glutelin fraction, however, did not present a denaturation
peak in the DSC curve, showing that the process for obtaining the same significantly altered its conformation.
Authors:Gustavo Guadagnucci Fontanari, José Manuel Martins, Marcelo Kobelnik, Iêda Aparecida Pastre, José Alfredo Gomes Arêas, José Paschoal Batistuti, and Fernando Luis Fertonani
. Fontanari et al. [ 11 ], in similar procedure for guavaseed protein isolate, reported higher levels of ash in PIs obtained at higher pHs without NaCl adding.
Thermal behavior of PIs
The TG–DTG curves recorded for PIs
Authors:K. Takács, E. Szerdahelyi, A. Nagy, and É. Gelencsér
guavaseed protein isolates: yield, composition and protein quality . Nahrung , 36 : 50 – 55 . 10.1002/food.19920360108 Adler-Nissen , J. ( 1979 ). Determination of the degree of hydrolysis of food protein hydrolysates by trinitrobenzenesulphonic