Effect of Microwave-Vacuum Drying on the Carotenoids Retention of Carrot Slices and Chlorophyll Retention of Chinese Chive Leaves

Abstract Microwave-vacuum drying, and combined microwave-vacuum with air or vacuum drying were investigated as potential methods for drying green and high-carotenoid vegetables of Chinese chive leaves and carrot slices. The samples were dried by microwave-vacuum until the moisture content reached about 20% (wet basis), and then by conventional air drying at the temperature of 45–50°C or conventional vacuum drying at the temperature of 55–60°C or by continued microwave-vacuum drying at lower power level to final moisture content about 6% (wet basis). The carotenoid retention of carrot slices and chlorophyll retention of Chinese chive leaves, dried by these methods, was evaluated and compared with those dried by freeze-drying and conventional hot-air drying. The comparison showed that the carotenoid retention of carrot slices and chlorophyll retention of chive leaves, dried by the current methods, was very close to or even as much as those dried by freeze-drying and much better than those dried by conventional hot-air. Blanching was not necessary when using microwave-vacuum drying or combined microwave-vacuum with conventional hot-air drying or vacuum drying, because the activity of enzymes which were responsible for the degradation of color was greatly reduced with extremely rapid decreasing of moisture, and because oxygen was absent in microwave-vacuum drying.

[1]  F. J. Francis,et al.  Effect of Processing Temperature on Pigments and Color of Spinach , 1962 .

[2]  Chang Yong Lee,et al.  Effect of Blanching on Enzyme Activity and Quality Changes in Green Peas , 1987 .

[3]  M. Holden.  Lipoxidase activity of leaves. , 1970 .

[4]  Antonio Mulet,et al.  DRYING OF CARROTS. II. EVALUATION OF DRYING MODELS , 1989 .

[5]  W. Horwitz.  Official Methods of Analysis , 1980 .

[6]  Alejandro Reyes,et al.  DRYING OF CARROTS IN A FLUIDIZED BED. I. EFFECTS OF DRYING CONDITIONS AND MODELLING , 2002 .

[7]  Zacharias B. Maroulis,et al.  KINETICS ON COLOR CHANGES DURING DRYING OF SOME FRUITS AND VEGETABLES , 1998 .

[8]  Y. W. Park,et al.  Effect of freezing, thawing, drying, and cooking on carotene retention in carrots, broccoli and spinach , 1987 .

[9]  A Bast,et al.  Beta-carotene as antioxidant. , 1996, European journal of clinical nutrition.

[10]  Carolyn A. Raab,et al.  Drying fruits and vegetables , 1976 .

[11]  I. Grün,et al.  Blanching Effects on the Chemical Composition and the Cellular Distribution of Pectins in Carrots , 2002 .

[12]  P. Cunniff.  Official Methods of Analysis of AOAC International , 2019 .

[13]  C. Tong,et al.  Degradation kinetics of green color and chlorophylls in peas by colorimetry and HPLC , 1996 .

[14]  H. S. Ramaswamy,et al.  Microwave-assisted convective air drying of thin layer carrots , 1995 .

[15]  V. Böhm,et al.  Antioxidant and Antimutagenic Activity of Dietary Chlorophyll Derivatives Determined by Radical Scavenging and Bacterial Reverse Mutagenesis Assays , 2002 .

[16]  J. Hutchings.  Chemistry of Food Colour , 1994 .

[17]  G. Poppel,et al.  Epidemiological evidence for beta-carotene in prevention of cancer and cardiovascular disease. , 1996 .

[18]  Shahab Sokhansanj,et al.  Kinetics of Dehydration of Green Alfalfa , 1996 .

[19]  Da-Wen Sun,et al.  Dehydration of Garlic Slices by Combined Microwave-Vacuum and Air Drying , 2003 .

[20]  S. Schwartz,et al.  Kinetics of Chlorophyll Degradation to Pyropheophytin in Vegetables , 1983 .

[21]  John D. Floros,et al.  Optimization of Carrot Dehydration Process using Response Surface Methodology , 1989 .