Effects of roasting on alkylpyrazin compounds and properties of cocoa powder

Effects of stir-frying on chemical profile, sensory quality and antioxidant activity of Chrysanthemi Flos: A metabolomics and sensory study

Chrysanthemi Flos has been consumed as floral tea for centuries, but the effects of stir-frying on its chemical profile, sensory characteristics, and bioactivity remain unclear. This study used untargeted metabolomics, sensory assessment (E-eye, E-nose, E-tongue), and antioxidant activity evaluation to investigate compositional changes and their effects. In the metabolomics analysis, a total of 101 non-volatile and 306 volatile differential metabolites were identified. During stir-frying of Chrysanthemi Flos, glycosidic bond rupture in flavonoid glycosides, thermal decomposition of caffeoylquinic acid, Maillard, and caramelization reactions occurred. This led to the formation of 4 flavonoid glycosides (luteolin, diosmetin, apigenin, and quercetin) and 33 roasted aroma compounds like pyrazines, furans, 2-methylbutanal, and 2-furanmethanol. The Spearson's correlation analysis of metabolomics, E-eye, and E-tongue data showed that these compositional changes not only resulted in darkening and scorching of the color of Chrysanthemi Flos after stir-frying, but also improved the bitter and astringent taste of Chrysanthemi Flos tea broths, and enhanced the antioxidant activity of Chrysanthemi Flos. These findings will provide new perspectives on the selection of processing methods for Chrysanthemi Flos.

Influence of process conditions of alkalization on quality of cocoa powder

In this study, the effects of independent variables such as alkaline (NaOH) salt concentration (3.0-6.0 g/100 mL), alkalization temperature (60-90 °C), and time (20-40 min) on cocoa powder (low-fat) properties were investigated by using Central Composite Design. The physicochemical and color properties of samples, powder characteristics, volatile component profile, total polyphenol content (TPC), as well as antioxidant activity potentials using different methods (DPPH and ABTS) were determined. Significant models were identified for the effects on major alkalization indicators (L*, a*/b*, pH), as well as TPC and antioxidant activity potential (DPPH), which are the main motivators for the preference and consumption of cocoa products (p < 0.05). The established model was validated, and their predicted values were found to be very close to real results. It was determined that the alkali concentration had a more significant effect on dependent variables, especially on alkalization indicators, compared to the other independent variables. Furthermore, strong correlations were determined between TPC and antioxidant activity potential and color properties (L*, a*, b*, and a*/b*). Optimum concentration, temperature and time were found to be 5.3 %, 84 °C and 35.7 min for maximizing a*/b* value. The establishment of such models lead to optimizing process conditions of alkalization with minimum effort and labor force for obtaining cocoa powder with desired quality depending on the usage purpose.