RESUMEN
The object of this study was tilapia fish that were fried in soybean oil. Volatile compounds were extracted from the fish by ASE-HVE and were studied by GC-O-MS and the AEDA analysis method. A total of 30 aroma compounds were initially determined, and these compounds contribute to the aroma of fried tilapias. The key volatile compounds in fried tilapia were quantitatively analyzed by GC-MS, and the volatile compounds in soybean-fried tilapia were studied by flavor recombination and deletion experiments. Trimethylamine, hexanal, 2,3-dimethylpyrazine, dimethyl trisulfide, trans-2-octenal, 2,3-dimethyl-5-ethylpyrazine, (E)-2-nonenal, 2-propyl-pyridine, and (E,E)-2,4-decadienal were finally determined to be the key volatile compounds in soybean-fried tilapia.
RESUMEN
The alkaline protease gene, Apr, from Bacillus licheniformis 2709 was cloned into an expression vector pET - 28b (+), to yield the recombinant plasmid pET-28b (+) - Apr. The pET-28b (+) - Apr was expressed in a high expression strain E. coli BL21. The amino acid sequence deduced from the DNA sequence analysis revealed a 98% identity to that of Bacillus licheniformis 2709. Sodium salt-Polyacrylamide gel electrophoresis (SDS-PAGE) was used to access the protein expression. SDS-PAGE analysis indicated a protein of Mr of 38.8 kDa. The medium components and condition of incubation were optimized for the growth state of a recombinant strain. The optimal composition of production medium was composed of glucose 8 g/L, peptone 8 g/L and salt solution 10 mL. The samples were incubated on a rotary shaker of 180 r/min at 37°C for 24 h.
Asunto(s)
Bacillus/enzimología , Bacillus/genética , Proteínas Bacterianas/biosíntesis , Proteínas Bacterianas/genética , Endopeptidasas/biosíntesis , Endopeptidasas/genética , Proteínas Recombinantes/biosíntesis , Secuencia de Aminoácidos , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Biocatálisis/efectos de los fármacos , Electroforesis en Gel de Poliacrilamida , Endopeptidasas/química , Endopeptidasas/metabolismo , Escherichia coli/genética , Glucosa/metabolismo , Cinética , Datos de Secuencia Molecular , Peso Molecular , Peptonas/farmacología , Plásmidos/genética , Reacción en Cadena de la Polimerasa , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Análisis de Secuencia de ADN , Factores de TiempoRESUMEN
Egg white protein powder, one of the main egg products, was hydrolysed by Alcalase, Trypsin, and Pepsin respectively to prepare antioxidant peptides. All hydrolysates were assayed by determination of reducing power (RP) ability. Three kinds of hydrolysates were prepared under optimal enzymatic parameters that were obtained from the preliminary one-factor-at-a-time (OFAT) and response surface methodology (RSM) experiments. The results showed that the Alcalase hydrolysates exerted the best RP ability. Thereafter, the Alcalase hydrolysates were sequentially fractionated by ultra filtration membranes in cut-off molecular weight (MW) of 30, 10, and 1 kDa, and tested their antioxidant activities in terms of RP ability, DPPH radical scavenging ability, ABTS radical scavenging ability, and FRAP assay. Effects of high intensity pulsed electric field treatment were further investigated on antioxidant peptides to improve their activities. The results showed that Alcalase hydrolysates possessed the strongest antioxidant ability compared with the other two hydrolysates, particularly for the Fraction-3 with MW <1 kDa. After PEF treatment, this fraction showed a significant improvement of RP ability within 5 h (P<0.05).
Asunto(s)
Antioxidantes/química , Clara de Huevo/química , Péptidos/química , Hidrolisados de Proteína/química , Animales , Antioxidantes/aislamiento & purificación , Pollos , Hidrólisis , Peso Molecular , Péptidos/aislamiento & purificación , Hidrolisados de Proteína/aislamiento & purificación , Subtilisinas/química , Tripsina/químicaRESUMEN
In the present study, aberration, body weight, food consumption, haematology, organ coefficients, and both gross and microscopic appearance of some histiocytes were compared between the test and control groups. A sperm abnormality test, bone marrow cell micronucleus test, and a haematology study were conducted at levels of 1.25 g/kg, 2.5 g/kg, and 5 g/kg of trehalose. In both the sperm abnormality test and bone marrow cell micronucleus test, statistically significant differences were observed between the positive control and treatment groups (P<0.05), while no statistical difference was observed among the negative control, high dose, moderate dose and low dose groups (P>0.05). In the haematology study, there was no significant difference found from the controls at P>0.05. The results obtained in the present study could support the conclusion that consumption of trehalose has no adverse effects for humans.
Asunto(s)
Trehalosa/toxicidad , Animales , Peso Corporal/efectos de los fármacos , Línea Celular , Humanos , Masculino , Ratones , Tamaño de los Órganos/efectos de los fármacos , Reproducción/efectos de los fármacos , Espermatozoides/efectos de los fármacos , Trehalosa/administración & dosificaciónRESUMEN
The trehalase activity plays an important role in extraction of trehalose from beer yeast. In this study, the effect of pulsed electric field processing on neutral trehalase activity in beer yeast was investigated. In order to develop and optimize a pulsed electric field (PEF) mathematical model for activating the neutral trehalase, we have investigated three variables, including electric field intensity (10-50 kV/cm), pulse duration (2-10 µs) and liquid-solid ratio (20-50 ml/g) and subsequently optimized them by response surface methodology (RSM). The experimental data were fitted to a second-order polynomial equation and profiled into the corresponding contour plots. Optimal condition obtained by RSM is as follows: electric field intensity 42.13 kV/cm, liquid-solid ratio 30.12 ml/g and pulse duration 5.46 µs. Under these conditions, with the trehalose decreased 8.879 mg/L, the PEF treatment had great effect on activating neutral trehalase in beer yeast cells.