Butterfly pea flower have great sensory attraction, but they have not yet been used widely in Vietnam. Extracts of butterfly pea flowers can be used conveniently as a natural blue colorant for food products. In this study, the identification of anthocyanin compounds in butterfly pea flowers was performed by UPLC coupled with a UV and Mass spectrometer instrument. Positive and negative ion electrospray MS/MS chromatograms and spectra of the anthocyanin compounds were determined. By analyzing the chromatograms and spectra for each ion, five anthocyanins were identified in the butterfly pea flower extract; these were delphinidin-3-(6″-p-coumaroyl)-rutinoside, cyanidin 3-(6″-p-coumaroyl)-rutinoside, delphinidin-3-(p-coumaroyl) glucose in both cis- and trans- isomers, cyanidin-3-(p-coumaroyl-glucoside) and delphinidin-3-pyranoside. Additionally, based on their intensity, it was determined that cyanidin-3-(p-coumaroyl-glucoside) was the most abundant anthocyanin, followed by cyanidin 3-(6″-p-coumaroyl)-rutinoside, delphinidin-3-(p-coumaroyl-glucoside), delphinidin-3-(6″-p-coumaroyl)-rutinoside and delphinidin-3-pyranoside. In this study, cyanidin derivatives were discovered in butterfly pea flower extract, where these compounds had not been detected in previous studies.

Mulberry powder was created from the extract using a foam-mat drying process. The studies aimed to evaluate the effects of egg albumin, carboxymethyl cellulose (CMC), digestion-resistant maltodextrin (DRM) contents, and whipping time (5 to 15 min) on the foam properties. The impact of different drying temperatures (60 to 75 °C) on the quality of the finished mulberry powder was also noted. The best foam expansion/stability value was determined using multiple regression models as a function of egg albumin, CMC, DRM, and whipping time. The results indicated that the main influencing factors for the foam properties were whipping time followed by egg albumin, CMC, and DRM. Optimum values of foam expansion and stability were achieved at 467.9% and 97.02%, respectively. The foam had a porous structure and good stability for subsequent drying, with optimal contents of egg albumin, CMC, and DRM used at 7.6%, 0.4%, and 2%, respectively, along with a whipping time of 14.5 min. The established models had a high coefficient of determination (R² > 0.9) and a high correlation between the predicted and observed values. Therefore, the model could be adjusted to determine the characteristics of the foam suitable for subsequent drying. The optimal values were then also verified. Minimal fluctuations (1.78–2.98%) between the experimental data and the optimal value were found. The drying temperature also significantly affected the quality of the mulberry powder. The foam was dried at 65 °C for 4 h to produce apowder with a beautiful light color (L* = 62.65), a characteristic purple-red color of mulberry (a* = 5.97). The moisture, water activity, and anthocyanin content of the finished mulberry powder were 4.57%, 0.3, and 5.4 mg/g, respectively.

In manufacturing food powders, foam-mat drying provides a cost-effective alternative to traditional drying methods. This study aimed to select the foaming conditions which support the subsequent drying of Magenta leaves extract. In the initial stage, concentrations of egg albumin (5 to 15%) as a foaming agent, xanthan gum as foam stabilizer (0.1 to 0.5%), and whipping time (2 to 8 min) were designed. Multiple regression analysis was applied to analyze the relationship between the dependent variables (Foam expansion volume and foam density) and three independent variables as an indicator of foaming capacity and foam stability. The multiple response optimization was applied to optimize the foam density and foam expansion. The optimum foam density (0.25 g/mL) and foam expansion volume (298.12%) were obtained at the optimum egg albumin and xanthan gum concentrations, and whipping time at 12.21%, 0.24%, and 5.8 min, respectively, indicating a stable foam structure. Experimental moisture loss data are fitted for five selected drying models. The mathematical models were compared according to three statistical parameters, such as coefficient of determination (R²), chi-square (χ²), and root mean square error (RMSE). Among the five mathematical models tested with experimental data, the Page model could be applied to describe the foam-mat drying process of magenta leaves extract. The highest value of R² (99.54%), the lowest value of χ² (0.0007), and RMSE (0.0253) were observed for a air drying temperature of 60 °C. The effect of temperature on diffusion is described by the Arrhenius equation with an activation energy of 100.21 kJ/mol. Effective moisture diffusion values ranged from 2.27 × 10⁻¹⁰ to 6.71 × 10⁻¹⁰ m²/s as the temperature increased. The effect of drying conditions on anthocyanin changes of magenta leaves powder was compared. The results showed that the highest quality of the sample was observed when the sample was dried at 60 °C.

Quercetin is a bioactive compound that has many beneficial effects on human health. Due to a lack of information about quercetin and quercetin derivatives in the Vietnam shallot, this work aimed to identify the quercetin family in shallot skin and flesh by liquid chromatography-mass spectrometry. Effect of extraction method (conventional solvent extraction and ultrasound-assisted extraction), including ethanol concentration (40–80%) and extraction time (15 to 60 mins) on the yield of quercetin were also investigated in this study. Quercetin, quercetin-glucoside and methylated-quercetin-hexose were commonly found in the extract of shallot flesh and skin. A very small amount of quercetin aglycone (0.7%) was found in flesh extract, while it was the most abundant in the skin sample (46.3%). The high content of quercetin-mono-glycoside was obtained in shallot extract (43.8% and 35.3% in the shallot flesh and skin, respectively). The flesh extract also contained high level of quercetin-di-glucoside (38.9%). About 14-16% of methylatedquercetin (-glucoside) were found in shallot bulb (both skin and flesh). It was found that ethanol concentration and extraction time directly affected on the quercetin extraction yield. The highest quercetin content was obtained in the sample which was extracted in 60% ethanol in combination with ultrasound-assisted extraction for 15 to 45 mins. The ultrasound-assisted extraction method improved quercetin yield by 13.38-15.64% and 49.46-56.88% for shallot skin and flesh compared to conventional solvent extraction. This study proved that ultrasound-assisted extraction could successfully be used for extraction of quercetin from shallot (both skin and flesh).

The red dragon fruit (Hylocereus polyrhizus), an available and popular agricultural source in Vietnam, is potential material for food colourants because of the presence of betacyanin. For the purpose of using dragon fruit extract to add colour to processed foods, the study on the effects of extraction methods (conventional and ultrasound-assisted) on the flesh and peel of the fruit was carried out using water as an extraction solvent. The obtained results showed that using ultrasonic waves in extraction enhanced the total betacyanin content in red dragon flesh and peel extract. Multiple regression analysis for betacyanin and the independent variable was obtained with a high coefficient determination (R2 >0.8). The highest total betacyanin content predicted by the models were 27.49 mg/100 mL and 22.28 mg/100 mL corresponding to extracted at a ratio of 83.74% red dragon flesh for 13.15 mins and the ratio of peel to the water of 90.63:9.37 for 12.91 mins. The obtained result could be applied to the food industry to use the achieved as a natural food colour for further processing.

Orange-fleshed sweet potato (OFSP) noodles were created by replacing a portion of the wheat flour with OFSP flour in a formulation. This study was performed to identify the physical and chemical characteristics as well as sensorial attributes of noodles prepared from OFSP with some flours (wheat flour and semolina). The addition of xanthan gum and incubation time was examined. Instrumental analyses of noodles (cooking loss, volume increase, rehydration ratio, structure and microstructure) were carried out to assess the impact of experimental factors. The obtained results revealed that noodles made with more OFSP flour had a more yellow color than those with less OFSP flour. The mixture of OFSP and wheat flour in the formula F2 (the percent of OFSP 18.79% and wheat flour 28.18%) produced noodles with high quality and was the most favorable in appearance, taste, texture, and acceptability among the four formulas. Cooking weight and volume were increased from 164.89 to 174.12% and from 184.74 to 194.81%, respectively when semolina was added to the formula. The supplemental semolina 10.57%, xanthan gum of 2% and the incubation time 30 mins were obtained to enhance dough binding properties. The results suggest that OFSP flour could be replaced up to 40% wheat flour for noodles to improve the nutritional value (i.e. increased b-carotene) and might be acceptable to consumers with health food.