Ying Lyu1,2, Jinfeng Bi1,2, Qinqin Chen2, Xuan Li2, Xinye Wu2, Haonan Hou2, Xing Zhang2. 1. Department of Food Science, Shenyang Agricultural University, Shenyang, China. 2. Key Laboratory of Agro-Products Processing, Ministry of Agriculture and Rural Affairs, Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences (CAAS), Beijing, China.
Abstract
BACKGROUND: High carotenoid content always lead to a yellower/redder color in carrots, while a puzzling phenomenon still exists that freeze-dried carrots (FDC) have a higher carotenoid content but a lighter color compared with thermal-dried carrots. It seems that carotenoid is not the only main factor affecting sample color. Hence the discoloration characteristics of freeze-dried carrots were comprehensively analyzed from physical structure and color-related chemical composition profile. RESULTS: Outcomes of low-field nuclear magnetic resonance and scanning electron microscopy showed that sublimation of immobilized water preserved the intact porous structure of FDC, which kept the volume shrinkage below 30% and led to less accumulations of color-related compositions. Besides, results of correlation and principal component analysis-X model proved that lutein and caffeic acid mainly affected a* value (r = 0.917) and b* value (r = 0.836) of FDC, respectively. Moreover, lipoxygenase indirectly affected sample color by degrading carotenoids, and the lutein content loss for fresh and blanching FDC was 41.56% and 47.14%, respectively. CONCLUSIONS: The discoloration of FDC was significantly affected by both physical structure and color-related chemical compositions.
BACKGROUND: High carotenoid content always lead to a yellower/redder color in carrots, while a puzzling phenomenon still exists that freeze-dried carrots (FDC) have a higher carotenoid content but a lighter color compared with thermal-dried carrots. It seems that carotenoid is not the only main factor affecting sample color. Hence the discoloration characteristics of freeze-dried carrots were comprehensively analyzed from physical structure and color-related chemical composition profile. RESULTS: Outcomes of low-field nuclear magnetic resonance and scanning electron microscopy showed that sublimation of immobilized water preserved the intact porous structure of FDC, which kept the volume shrinkage below 30% and led to less accumulations of color-related compositions. Besides, results of correlation and principal component analysis-X model proved that lutein and caffeic acid mainly affected a* value (r = 0.917) and b* value (r = 0.836) of FDC, respectively. Moreover, lipoxygenase indirectly affected sample color by degrading carotenoids, and the lutein content loss for fresh and blanching FDC was 41.56% and 47.14%, respectively. CONCLUSIONS: The discoloration of FDC was significantly affected by both physical structure and color-related chemical compositions.