Effect of thermal and ultrasonic pretreatment on enzyme inactivation, color, phenolics and flavonoids contents of infrar
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ORIGINAL PAPER
Effect of thermal and ultrasonic pretreatment on enzyme inactivation, color, phenolics and flavonoids contents of infrared freeze‑dried rose flower Yoon Hlaine Barani1,3 · Min Zhang1,2 · Bing Wang4 Received: 19 March 2020 / Accepted: 12 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The effects of ultrasound and thermal pretreatment prior to freeze drying combined with infrared on enzyme activity, color changes and antioxidant activities of dried rose flowers were studied. The activities of polyphenol oxidase (PPO) and peroxidase (POD) in rose after ultrasonic pretreatment were significantly decreased than thermal treatments. Ultrasonic pretreatment could improve the color of dried rose flowers. In addition, low-frequency ultrasound pretreatment could significantly improve the content of anthocyanins content and reduce the degradation rate. The antioxidant activity of low-frequency ultrasound pretreatment rose was also higher than that of dried rose flowers by thermal and high-frequency ultrasound pretreatment. However, thermal pretreatment as high temperatures affected the total phenolic content and product quality in different way such as loss of color and nutrients degradation. Keywords Thermal pretreatment · Ultrasound pretreatment · Enzyme inactivation · Anthocyanins · Color stability
Introduction Edible flowers have attracted much attention because of its attractive color, flavor and aroma, as well as biologically active substances, including phenolics and flavonoids. In the edible flowers rose (Rosa damascena) is also known for its smoothness, coolness, astringent, antidepressant and anti-inflammatory properties [1]. Roses are one of the most important flower products in the world. For thousands of years, roses have been grown as a popular garden flower and cut flower. Qiu et al. [2] reported that Rose’s flowers include vitamins, flavonoids, polyphenols, polysaccharides and other * Min Zhang [email protected] 1
State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi 214122, Jiangsu, China
2
Jiangsu Province Key Laboratory of Advanced Food Manufacturing Equipment and Technology, Jiangnan University, Wuxi 214122, Jiangsu, China
3
International Joint Laboratory On Food Safety, Jiangnan University, Wuxi 214122, Jiangsu, China
4
Shandong Huamei Biology Science & Technology Co., Pingyin 250400, Shandong, China
biological active substances can prevent diabetes, cancer, cognitive decline and other chronic degenerative diseases, beneficial to the human body. Drying is one of the most important ways of preserving food. Preservation of food cannot only significantly prolong the shelf life of vegetables, but also to provide consumers with different foods [3, 4]. On the other hand, fruits and vegetables undergo physical and chemical changes during drying, such as volume contraction, surface hardening, and discoloration [5, 6]. Freeze-drying is one of the most
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