Volatile compounds in whole meal bread crust: The effects of yeast level and fermentation temperature.
The influence of fermentation temperatures (8°C, 16°C, and 32°C) and yeast levels (2%, 4%, and 6% of the flour) on the formation of volatile compounds in the crust of whole meal wheat bread was investigated. The fermentation times were regulated to optimum bread height for each treatment. The volatile compounds were extracted by dynamic headspace extraction and analyzed by gas chromatography-mass spectrometry. The results were evaluated using multivariate data analysis and ANOVA. In all crust samples 28 volatile compounds out of 58 compounds were identified and the other 30 compounds were tentatively identified. Higher fermentation temperatures promoted the formation of Maillard reaction products 3-methyl-1-butanol, pyrazine, 2-ethylpyrazine, 2-ethyl-3-methylpyrazine, 2-vinylpyrazine, 3-hydroxy-2-butanone, 3-(methylsulfanyl)-propanal, and 5-methyl-2-furancarboxaldehyde whereas at lower temperature (8°C) the formation of 2- and 3-methylbutanal was favored. Higher levels of yeast promoted the formation of 3-methyl-1-butanol, 2-methyl-1-propanol and 3-(methylsulfanyl)-propanal, whereas hexanal was promoted in the crust fermented with lower yeast level.
Four insect oils as food ingredient: physical and chemical characterisation of insect oils obtained by an aqueous oil extraction
Insect fractionation and insect ingredient characterisation is of relevance in view of the increase in insect production and demand of insect ingredients worldwide. This study aims to contribute to the knowledge of insect oils that were extracted from insects commercially reared in Europe. Oil was extracted from yellow mealworm, lesser mealworm, house cricket and Dubia cockroach by an aqueous based oil extraction method. These insect oils were physico-chemically characterised on the most important parameters for food applications, namely thermal behaviour (differential scanning calorimeter), colour (spectrophotometry) and aroma compounds (gas chromatography-mass spectrometry). The amount and the composition of the un-extracted lipid fraction was determined by means of fatty acid (FA) profiling (gas chromatography with flame ionisation detector). Although no distinctive pattern was seen in all four species, it becomes clear from its FA profile that the extracted fat is more similar to the residue and cream fractions than to the pellet and supernatant. The amount of lipids that was not extracted was species dependent ranging from 40 to up to 82% of the total lipid content. Further work is needed to reduce the oil loss in this extraction. The extracted insect oil presented a wide range of melting peaks, from -30.7 to 22.7 °C, which makes them liquid-like at room temperature. Its thermal profile shows separated peaks showing that fat fractionation is feasible. Oil colour was bright yellow-reddish. Most oils had compounds related to pleasant aromas, except for Dubia cockroach. In the latter oil several acid compounds related to unpleasant aromas were identified. This study shows that yellow meal worm oil, lesser mealworm oil and cricket oil have characteristics desirable for table oils and for oils use as food ingredients.
Evaluation of buckling load and dynamic performance of steel shear wall retrofitted with strips made of shape memory alloy
One of the most imperfections of the steel shear wall is out of plane displacements that cause severe damage in both structural and non-structural elements. In this paper, the effects of shape-memory alloys on steel shear walls are investigated. First, a numerical analysis using the finite element method in ABAQUS software has been carried out according to an experimental test. The results of the numerical analysis have been verified with experimental results. Next, shape-memory alloy fibers have been added vertically and horizontally to various parts of the steel shear wall. The results show that retrofitting with the shape-memory alloy reduces the out-of-plane displacement of the steel shear wall under both cyclic and seismic loadings. Besides, the buckling load in the steel shear wall increases when it is retrofitted with the shape-memory alloy. Also, the total out-of-plane movement (accumulated absolute displacements) of the steel shear wall and non-structural damage are controlled by the characteristic of a shape-memory alloy material called “super-elastic”.