Effect of addition of thermally modified cowpea protein on sensory acceptability and textural properties of wheat bread and sponge cake.
This paper investigates the sensory acceptability and textural properties of leavened wheat bread and sponge cake fortified with cow protein isolates that had been denatured and glycated by thermal treatment. Defatted cowpea flour was prepared from cow pea beans and the protein isolate was prepared (CPI) and thermally denatured (DCPI). To prepare glycated cowpea protein isolate (GCPI) the cowpea flour slurry was heat treated before isolation of the protein. CPI was more susceptible to thermal denaturation than GCPI as determined by turbidity and sulphydryl groups resulting in greater loss of solubility. This is attributed to the higher glycation degree and higher carbohydrate content of GCPI as demonstrated by glycoprotein staining of SDS PAGE gels. Water absorption of bread dough was significantly enhanced by DCPI and to a larger extent GCPI compared to the control, resulting in softer texture. CPI resulted in significantly increased crumb hardness in baked bread than the control whereas DCPI or GCPI resulted in significantly softer crumb. Bread fortified with 4% DCPI or GCPI was similar to control as regards sensory and textural properties whereas 4% CPI was significantly different, limiting its inclusion level to 2%. There was a trend for higher sensory acceptability scores for GCPI containing bread compared DCPI. Whole egg was replaced by 20% by GCPI (3.5%) in sponge cake without affecting the sensory acceptability, whereas CPI and DCPI supplemented cakes were significantly different than the control.
Contribution of linoleic acid to the formation of advanced glycation end products in model systems during heat treatment
Zhao X., Yue L., Liu X., Liu L. (2017): Contribution of linoleic acid to the formation of advanced glycation end products in model systems during heat treatment. Czech J. Food Sci., 35: 367–375. Advanced glycation end products (AGEs) are glycosylated metabolic products generated in vivo and are associated with aging-related diseases. They are also formed during heat treatment in food processing. In this work, we investigated the contribution of linoleic acid (LA) to AGE formation using a protein/glucose model. An electronic tongue, denaturing polyacrylamide gel electrophoresis, electron spin resonance spectroscopy, circular dichroism, and ultraperformance liquid chromatography-tandem mass spectrometry were used to analyse reaction intermediates and reactive radical formation. The results show that LA is the key factor responsible for the change in flavour including the rapid triggering of glycation reactions. The amount of lipid-induced reactive radicals was significantly higher than in the non-fat system, radical generation in the non-fat system was gradually quenched after a robust radical-yielding reaction in the first 25 minutes. Subsequent unsaturated lipid oxidation, and AGE accumulation surpass Maillard reaction-only outcomes. Initial LA-induced changes in protein structure are followed by glycation and are enhanced by hydrophobic interactions and increased carbonyl levels resulting from lipid oxidation. These findings implicate lipids and lipid oxidation as the main factors responsible for AGE formation during the processing of fat-rich unsaturated fatty acid-containing foods.
Influence of soy protein on rheological properties and water retention capacity of wheat gluten
Abstract A better understanding of the physicochemical and rheological changes in soy/wheat composite dough may lead to overcome the problems caused by the incorporation of high levels of soy products on bread formulation. The effects of commercial soy protein isolate (SPI) on uniaxial extension and creep behavior, microstructure and free water of hydrated gluten were studied. Different solid:moisture ratios were used. Results showed that the substitution of wheat protein by soy protein negatively affected the gluten–SPI mixture rheological properties due to network weakening. It was demonstrated that gluten was weakened as a consequence of the interference effect of soy proteins on their structure, and the smaller availability of water to the build-up of the gluten network. A greater amount of moisture could partially improve the rheological performance of the gluten–SPI mixture.