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Drying is one of the most important post-harvesting processes with the aim of increasing the storage time. The present study investigates and compares color changes and shrinkage of red beetroot thin layers in four different drying methods (hot air flow, microwave, vacuum and freeze drying). The process of changing these two parameters was simulated by fitting to different models. The experiments were carried out in hot air and vacuum air dryers at three temperature levels (50, 70 and 90 °C), in microwave dryer at a power level of 180, 360 and 600 W, and in a freeze dryer at -50 °C.The results showed that the changes in the brightness index (L) and yellowness (b) relative to the time were increasing and the trend of changes in the red index (a) was decreasing. The slightest changes in the parameters of brightness, redness and yellowness occurred in freeze drying, microwave and vacuum, respectively. The overall results showed that the highest amount of color change (ΔE) was 1.59 in drying by microwave and at 180 W, and the lowest drying rate was 0.76 in freeze drying. Also, shrinkage changes in sugar beet samples showed that the use of freeze dryer reduced the amount of shrinkage by 10-25% compared to the other three methods of drying. Also, modeling of color parameters and shrinkage showed that exponential models have higher ability to predict the process of color variation and shrinkage. [ABSTRACT FROM AUTHOR]

Abstract Foam-mat drying has been recently welcomed as an effective technique since it lacks deficiencies that plague conventional methods including poor water absorption and long process time. In this study, effect of hot air temperature (50, 60 and 70 °C) on quality properties of lime juice was investigated during foam-mat drying. The process was also simulated to determine the effect of temperature on the uniformity of moisture and temperature distributions during drying. Increase in temperature improved powder flowability. With a decrease in temperature, water absorption index increased by 17.74%. Moreover, effective moisture diffusion coefficient increased as a result of a rise in temperature, which, in turn, increased the drying rate by 20.23%. Increase in temperature also resulted in a 1.80% increase in the total color change and 6.60%, 1.18% and 1.35% decrease in chroma index, hue angle and browning index, respectively. A correlation coefficient of 0.903 was achieved between experimental and simulated data. Uniform distributions of temperature and moisture during drying resulted in an improvement in the qualitative properties of the final product regarding the uniformity of the powder's moisture content, improvement of water absorption properties and, finally, increase in the product's quality. Graphical abstract 3D moisture content profile at the end of drying process at air temperature 70 °C. Image 1 Highlights • Experimental and numerical foam-mat drying of lime juice was examined. • Increase in temperature from 50 to 70 °C resulted in a 20.23% rise in drying rate. • Uniform temperature and moisture distributions were obtained during the process. • 17.74% improvement in the powder's water absorption index was noticed at 50 °C. • The methodology may be a desirable counterpart for industrial applications. [ABSTRACT FROM AUTHOR]

The drying process of pasta plays a crucial role in assuring its final quality, since the operational conditions of this process may imply thermal and mechanical damage that also affect final product yield. In this work, independent analyses on furosine, carbohydrates, and color indices (red, yellow, and lightness) have been conducted on pasta samples produced by an Italian pasta factory in order to correlate the examined parameters with pasta drying process. The investigation has been focused on pasta samples having different shapes in order to evaluate how the considered parameters are affected by the specific thermal process scheduled for each pasta format. The same analyses were also performed on semolina used for each pasta sample production, with the aim of verifying whether furosine amount, color indices, and maltulose change in relationship with Maillard reaction (MR) occurring during the drying process. Maltulose presence has been evaluated in semolina for the first time. In addition, the study has been extended to commercial pasta samples of different qualities; a Principal Component Analysis (PCA) has also been conducted to combine together all observed data with the aim of proposing an overall quality index. Finally, a statistical model based on chemical and color parameters as independent variables was successfully developed ( R = 0.990) by means of a multiple linear regression (MLR) analysis to predict commercial pasta cook values and drying cycles as consequences. [ABSTRACT FROM AUTHOR]