Aerated whey protein gels as a controlled release system of creatine investigated in an artificial stomach

A controlled creatine-release system has been developed from whey protein-based gels. Their functionalization was carried out by aeration and sodium ions induced “cold gelation” processes. The effect of protein concentration in the aerated whey protein gels at pH 7.0 and 8.0 was analyzed. Physicochemical properties of the aerated gels were evaluated. It was possible to obtain the ions induced whey protein aerated gel with well distributed creatine and different microstructure as well as rheological properties. Different protein concentrations and pH enabled obtaining gels with different rheological properties, texture, air fraction, diameter of air bubbles, microstructure and surface roughness. An increase in the protein concentration enhanced the hardness of the samples, regardless of their pH. The mechanical strength of gels prepared at pH 8 were higher than those obtained at pH 7, as was manifested by the smaller storage modulus of the latter. The former gel exhibited a microstructure between particulate and fine-stranded. A stronger gel matrix produced smaller air bubbles. Aerated gels produced at pH 7.0 had higher roughness than those obtained at pH 8.0. Optimal conditions for inclusion of air bubbles into the gel matrix were: 9% protein concentration at pH 8.0 and this aerated gel was selected for digestion in the artificial stomach. There is a small conversion of creatine to creatinine in the artificial stomach digestion process (9.6% after 6 h). The diffusion of creatine crystals from the aerated gel matrix was the mechanism responsible for the release process. Aerated whey protein gels can be used as matrices for time extended releasing of creatine in the stomach.     

Changes in the textural and flavor characteristics of egg white emulsion gels induced by lipid and thermal treatment

Egg white (EW) and peanut oil (PO), show good gel and flavor properties and were used to study the effects of lipid and heat treatment on the texture and flavor of emulsion gels. Good emulsification was obtained at low protein concentrations, and extremely high or low protein concentrations were essential for the formation of emulsion gel hardness, whereas the chewiness of emulsion gels with intermediate protein concentrations was sensitive to heat treatment. A new nonflowing proton (H⁺) from EW and lipid was integrated, and the water and lipids were closely bonded with other macromolecules in EW-PO emulsions. The bound and free water were combined with nonflowing water in emulsion gels due to heat treatment. 2-Methylbenzyl alcohol, octanoic acid ethyl ester, phenol and nicotinyl alcohol were the main flavor components of EW and PO, whereas 3,5-diethyl-2-methyl-pyrazine and 1-methyl-1H-pyrrole-2-carboxaldehyde were produced during the formation of the EW-PO emulsion. The formation of methylene-benzeneacetonitrile, 1H-pyrrole-2-carboxaldehyde, etc., in EW-PO emulsion gels were affected by the proportion of PO. Phthalic acid, benzaldehyde, 2,3-dihydro-benzofuran, 4-bromo-3-chloro-N-(4-methylthiobenzylydene)-benzenamine, 2-aminopyridine, hexanal, heptaethylene glycol monododecyl ether, isophytol and nicotinyl alcohol, etc., were formed in EW-PO emulsion gels. The main and differential flavors of EW-PO emulsions (or gels) may be attributed to EW and peanut oil, and the variation in flavor emitted from peanut oil and EW-PO gels was induced by heat treatment.     

液相色谱法检测鱼类肝脏中天然维生素A北大核心CSCD

为了准确测定鱼类肝脏中维生素A(维生素A_(1)、维生素A_(2))含量,对样品预处理方法(水浴皂化法、室温皂化法、直接提取法)和检测方法(正相色谱法、反相色谱法)进行筛选,并应用于9种经济鱼类肝脏中维生素A的测定。结果表明:维生素A_(1)、维生素A_(2)标准品用反相色谱法检测分离效果良好,且在各自线性范围内线性关系良好,R^(2)均大于0.99;水浴皂化法维生素A含量显著高于室温皂化法及直接提取法(p<0.05),且维生素A_(1)平均回收率为104.52%,维生素A_(2)平均回收率为90.94%;在9种鱼中,除了淡水鱼乌鳢和大口黑鲈外,其他淡水、海水鱼类肝脏中维生素A总含量均达200μg/100 g以上,其中海水鱼龙趸石斑鱼肝脏中维生素A总含量最高,达到14413.78μg/100 g。水浴皂化法结合反相色谱法精密度良好,适用于鱼类肝脏中维生素A的分析测定。