CIMO/School of Agriculture, Polytechnic Institute of Bragança, Campus de Stª Apolónia, Bragança, 5300-253, Portugal.
LAQV@REQUIMTE/Laboratory of Bromatology and Hydrology, Faculty of Pharmacy, Porto University, Rua Jorge Viterbo Ferreira, 228, Porto, 4050-313, Portugal.
J Food Sci. 2020 Apr;85(4):1151-1159. doi: 10.1111/1750-3841.15097. Epub 2020 Mar 10.
Edible flowers are a new gourmet product; however, they are not always available all years. Thus, it is essential to find out technologies to guarantee this product for a longer time. Flowers of four species (borage [Borago officinalis], heartsease [Viola tricolor], kalanchoe [Kalanchoe blossfeldiana], and dandelion [Taraxacum officinale]) were subjected to freezing (in their natural form and in ice cubes) and analyzed in terms of visual appearance, the content of flavonoids, hydrolysable tannins, phenolics, antioxidant activity (2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and reducing power), and microbial quality after storage for 1 and 3 months. Flowers in ice cubes showed similar appearance to fresh ones during the 3 months of storage, whereas frozen flowers were only equivalent up to 1 month with the exception of kalanchoe. Even though flowers in ice cubes showed good appearance after 3 months of storage, they had the lowest values of bioactive compounds and antioxidant activity. On the contrary, when frozen, the content of bioactive compounds maintained or even increased up to 1 month of storage compared to fresh flowers, except for borage. Furthermore, in both freezing treatments, the microorganisms' counts decreased or maintained when compared to fresh samples, except in dandelion. In general, both treatments may allow keeping the flowers after their flowering times. PRACTICAL APPLICATION: The market of edible flowers is increasing, although they are a very perishable product with short shelf-life. Edible flowers are stored in the cold (frozen or in ice cubes); however, the effect on the bioactive compounds and microbial quality that this treatment may have on borage (Borago officinalis), heartsease (Viola tricolor), kalanchoe (Kalanchoe blossfeldiana), and dandelion (Taraxacum officinale) flowers is unknown. So, the present study was conducted to increase the knowledge about the changes that freezing treatments may have in different edible flowers. The results of the present study underline that each flower has different behavior at frozen and ice cubes storage. However, freezing flowers maintain/increase the contents of bioactive compounds, while ice cubes not. Both treatments are effective in protecting flowers from microorganism growth. So, suggesting that both freezing treatments can be used as a preservative method and may allow keeping the flowers after their flowering times.
可食用花卉是一种新型美食产品，但并非全年都有供应。因此，找到能够更长时间保证这种产品供应的技术至关重要。我们对四种花卉（琉璃苣 [Borago officinalis]、三色堇 [Viola tricolor]、长寿花 [Kalanchoe blossfeldiana] 和蒲公英 [Taraxacum officinale]）进行了冷冻（自然形态和冰块中）处理，并在储存 1 个月和 3 个月后，从外观、类黄酮、可水解单宁、酚类、抗氧化活性（2,2-二苯基-1-苦基肼自由基清除活性和还原能力）和微生物质量等方面进行了分析。在储存的 3 个月内，冰块中的花卉外观与新鲜花卉相似，而冷冻花卉仅在 1 个月内与新鲜花卉等效，除了长寿花。尽管在储存 3 个月后，冰块中的花卉外观良好，但与新鲜花卉相比，它们的生物活性化合物和抗氧化活性的含量最低。相反，当冷冻时，与新鲜花卉相比，除了琉璃苣之外，在 1 个月的储存期内，生物活性化合物的含量保持或甚至增加。此外，与新鲜样品相比，在这两种冷冻处理中，微生物的数量都减少或保持不变，除了蒲公英。总的来说，这两种处理方法都可以延长花卉的花期。实际应用：可食用花卉的市场正在增长，尽管它们是一种非常易腐的产品，保质期很短。可食用花卉存放在冷藏（冷冻或冰块中）中；然而，这种处理方法对琉璃苣（Borago officinalis）、三色堇（Viola tricolor）、长寿花（Kalanchoe blossfeldiana）和蒲公英（Taraxacum officinale）花卉的生物活性化合物和微生物质量可能产生的影响尚不清楚。因此，本研究旨在增加对冷冻处理可能对不同可食用花卉产生的影响的了解。本研究结果表明，每种花卉在冷冻和冰块储存中的表现都不同。然而，冷冻花卉保持/增加生物活性化合物的含量，而冰块则不然。这两种处理方法都能有效地防止花朵受到微生物的生长。因此，这两种冷冻处理方法都可以作为一种保鲜方法，使花卉在花期过后仍能保持新鲜。
