Xianzhe Zheng

Optimization of Parameters for Microwave-Assisted Foam Mat Drying of Blackcurrant Pulp

Both analysis and optimization of parameters of microwave-assisted foam mat drying (MAFM), viz. microwave power, pulp load, drying time, and pulp thickness, for the dehydration process of blackcurrant pulp were performed in a household microwave oven. During MAFM drying, microwave power, pulp load, and drying time have positive effects on both vitamin C and anthocyanin content of blackcurrant pulp up to a certain level then a negative trend is observed. The increase of microwave power and decrease of pulp load accelerate the dehydration of blackcurrant pulp. The pulp thickness has a significant positive effect on both vitamin C and anthocyanin content of blackcurrant pulp. The optimum parameters valid for MAFM drying of blackcurrant pulp are as follows: microwave power of 560 W, pulp load of 65 g, drying time of 8 min, and pulp thickness of 4.46 mm. MAFM drying is a potential method for dehydrating blackcurrant pulp.

Analysis of Puffing Characteristics Using a Sigmodal Function for the Berry Fruit Snack Subjected to Microwave Vacuum Conditions

In order to clarify the mechanism of influence of independent variables in terms of microwave power, vacuum degree, initial moisture content, and puffing time on the objective indexes, in terms of moisture ratio and expansion ratio, a series of single-factor experiments was performed during microwave vacuum puffing of raspberry leathers. The results showed that microwave power, vacuum, and initial moisture content had a significant influence on the dehydration and texture quality of raspberry snacks in terms of expansion ratio, hardness, and porosity. The change in both moisture content and volume obeyed a sigmoid function as microwave power, vacuum pressure, and initial moisture content, respectively. Both microwave power and initial moisture content had a positive influence on the puffing kinetics up to a certain value followed by negative trends, with the exception of vacuum pressure in the selected range of 15–45 kPa which was insignificant. Texture evolution, including hardness and porosity index processes, has three distinct stages during microwave vacuum puffing of raspberry leathers. But the change in temperature of raspberry leather lags behind that in the texture of hardness and porosity. Raspberry snacks with a high expansion ratio may be obtained under the following conditions: microwave intensity 28 Wg−1, vacuum pressure 30 kPa, and initial moisture content 20.0% (wb).

Microwave Energy Absorption Behavior of Foamed Berry Puree Under Microwave Drying Conditions

The microwave energy absorption behavior of foamed berry puree was studied considering the variations in the physical properties of the material. The absorptions of microwave energy within foamed berry puree indicated fluctuating trends in decay as microwave drying progressed, which were attributed to the effects of temperature, moisture content, and density of the material. Mathematical models of the dielectric constant ϵ′ and dielectric loss factor ϵ″ as a function of temperature and moisture content were developed using second-order functions. During microwave drying of foamed berry puree, moisture content had the most important negative influence on the dielectric constant and dielectric loss factor, followed by temperature and porosity.

Effect of Drying Conditions on the Texture and Taste Characteristics of Rough Rice

The effects of drying conditions, viz. drying temperature, surface velocity, and initial moisture content, on the quality characteristics of cooked rice, including both texture and taste attributes, were investigated. A response surface methodology was employed to analyze the effects of drying conditions on the cooked rice quality and to optimize the drying parameters. The results show that moisture content is the most important positive factor, followed by drying temperature with a negative effect, and surface velocity is the least important, with a negative effect on taste. The drying conditions exert the significant effects on the texture and taste attributes of cooked rice. Drying temperature has a positive effect on the cohesiveness value of cooked rice and negative effects on the partial quality attributes, including hardness, gumminess, chewiness, stickiness, color, and flavor. The increase of surface velocity may cause an increase in cohesiveness and color and a decline in hardness, gumminess, smell, palatability, and flavor. Higher moisture content of rough rice contributes to improved color and palatability attributes and reduce the hardness and gumminess indexes. The overall taste value of cooked rice for the dried rough rice has a positive correlation with the hardness, gumminess, and stickiness (p < 0.05). Results suggested that the highest taste value for the rough rice was obtained under optimal conditions of drying temperature of 35.13°C and surface velocity of 0.41 m/s for rough rice with an initial moisture content of 19.69%. The result was verified by validation experiments.

Drying Properties and Parameters of Blue Honeysuckles Pulp under Foam Assisted Microwave Drying Conditions

The drying properties and optimal parameters of foamed blue honeysuckles pulp under microwave drying conditions were studied. The microwave power, loading mass and thickness were selected as the influencing factors, and objective factors were content of anthocyanin, vitamin C, moisture and values of color of the final blue honeysuckles powder. The drying process may be divided into three stages: acceleration stage, slow decline stage and quick decay stage. The initial drying phase lasted until the moisture content was less than 4 kg/kg. The constant drying phase was long when the influencing factor was loading mass. The deceleration drying phase is short in all conditions. This study achieve the continuous production of blue honeysuckles powder and the optimum experiment parameters were obtained as follows, the content of anthocyanin in honeysuckle powder is 64.58 mg/g, the content of vitamin C is 14.604 mg/g, moisture ratio is 9.88 % and the color value is 9.78 with the microwave power at 8.86 kW, loading mass at100 g and the thickness at 4mm.

Effect of the Microwave Irradiated Treatment on the Wine Sensory Properties

An instantaneous microwave irradiation method was applied to treat young dry red wine in order to accelerate the desired aging process during storing wine for the improvement of its taste quality. Effects of the microwave power and irradiation duration on the wine sensory property were investigated. Experimental results showed that microwave treatment had a significant effect on taste and total score, but no obvious effect was found on appearance, fragrance, fragrance duration and overall assessment. The influence of irradiation duration was significant on appearance, fragrance and total score, while not obvious on other indexes. The optimum conditions were obtained with microwave power 420 W and irradiation duration 5 min, and the result was corresponding to the content of chemical constituents of treated wine.

Effect of microwave energy dissipation on drying process of berry puree under microwave foam drying conditions

ABSTRACT Microwave foam drying (MFD) is a novel drying technology particularly for the drying of agricultural products with high viscosity and thermal-sensitive components. The effect of dissipation of microwave energy on the drying process of berry puree was investigated in MFD conditions. The results show that the dissipation of microwave energy induces the vapor pressure inside the berry puree to improve the formation of bubbles. The changes of pressure inside bubbles of berry puree follow Sine equations. The favorable conditions of bubbles formation inside berry puree are the temperature of 70–80°C with the corresponding viscosity of 70–80u2009pau2009s and moisture content of 80–85% (wb). The dissipation of microwave energy in berry puree tends to decaying trend due to the changes of dielectric properties. Moisture content has the most significant positive effect on both dielectric constant and dielectric loss factor of berry puree, followed by the density, and the drying temperature has the least but significant effect on both indicators. The focusing phenomenon of microwave irradiation depended on the dielectric properties determines the distribution of temperature of berry puree. The findings in current work contribute to a better understanding the MFD behavior of berry puree and will help to optimize the drying conditions of MFD for enhancing energy efficiency and drying quality.

Puffing Characteristics of Blackcurrant Leather Under Microwave Vacuum Conditions

In order to obtain the blackcurrant snack with high quality and efficiency, the puffing characteristics of blackcurrant leather under microwave vacuum conditions were investigated using single factor experimental method. The puffing characteristics, repersented by the moisture content and expansion ratio were determined in the different vacuum pressure, initial moisture content and the microwave power. The results show that both the microwave power and initial moisture content have significant effect on the moisture content. And no significant effect of the vacuum pressure on the final moisture content was found. For the initial moisture content of 35 %（w.b.）, the optimum processing parameters for maximum expansion ratio with 200% were obtained in the condition of microwave power of 2.48 kW and vacuum pressure of 70 kPa.

Effects of Microwave Power on Extraction Kinetic of Anthocyanin from Blueberry Powder considering Absorption of Microwave Energy

Microwave power as directly controlled parameter determines the absorption of microwave energy inside extraction vial and the yield of objective component in microwave-assisted extraction (MAE). The aim of this study was to elucidate the effects of microwave powers on the yield of anthocyanin from blueberry (Vaccinium spp.) powder based on the absorption of microwave energy in extracts under MAE. Rising microwave powers have little effect on the distribution of microwave energy in extraction vial, but increase its temperature. The simulation results indicated that strength of electrical field tends to decay trend along with microwave irradiation; however, temperatures have the highest level in center location in an extraction vial. High microwave power strongly breaks cell wall of blueberry to open diffusion route of interior anthocyanin toward extraction solvent. A critical extraction temperature of °C is obtained with the highest anthocyanin yield under MAE. Three monomers of anthocyanin including pelargonidin, cyanidin, and delphinidin are, respectively, of the highest content of 1.02u2009μg/mL, 0.66u2009μg/mL, and 0.31u2009μg/mL. The research results contribute to the improvement of efficiency of microwave energy and yield of anthocyanin.