Knoxfield Centre, Department of Primary Industries, Victoria, Ferntree Gully Delivery Centre, Victoria 3156, Australia.
J Agric Food Chem. 2010 Apr 28;58(8):5109-13. doi: 10.1021/jf904279j.
Carrots are one of the highest dietary sources of beta-carotene and are naturally high in the (all-E)-beta-carotene isomer, which has higher bioavailability, provitamin A activity, and antioxidant capacity compared to Z (cis) isomers. The objectives of the present study were to investigate the effects of storage temperature, time, and cooking (boiling for 15 min) on the levels of carotene isomers in 'Stefano' carrots. Storing carrots at either 4 degrees C to simulate long-term storage or 20 degrees C to simulate marketing practices resulted in increases in (all-E)-beta-carotene of 20.3% after 3 days at 4 degrees C and 34.4% after 14 days at 20 degrees C, respectively. The levels of Z isomers in raw carrots were low with (13Z)-beta-carotene and (9Z)-beta-carotene accounting for less that 1.8% of the total beta-carotene present. Levels of (9Z)-beta-carotene decreased during storage at either temperature, whereas storage at 4 degrees C resulted in a 109% increase in (13Z)-beta-carotene after 56 days. Cooking significantly increased the levels of (13Z)-beta-carotene and (9Z)-beta-carotene and resulted in the production of (15Z)-beta-carotene, which was absent in raw carrots. Storage at 4 degrees C for 15 days or more prior to cooking reduced the susceptibility of (all-E)-beta-carotene to thermal isomerization during cooking, resulting in lower levels of all three Z-beta-carotene isomers being generated, while storage at 20 degrees C for up to 21 days resulted in significantly higher levels of (all-E)-beta-carotene before and after cooking but had no effect on Z-isomer production during cooking. Consequently, we conclude that, for the greatest health benefit, fresh carrots can be stored for up to 21 days at 20 degrees C or at 4 degrees C for up to 56 days without significant reduction in (all-E)-beta-carotene and should be consumed raw or boiled for less than 15 min to limit Z-beta-carotene isomer formation.
胡萝卜是β-胡萝卜素含量最高的食物来源之一，天然富含全反式β-胡萝卜素异构体，与 Z（顺式）异构体相比，其生物利用率、维生素 A 前体活性和抗氧化能力更高。本研究的目的是研究贮藏温度、时间和烹饪（煮沸 15 分钟）对‘Stefano’胡萝卜中类胡萝卜素异构体水平的影响。将胡萝卜贮藏在 4°C 以模拟长期贮藏，或贮藏在 20°C 以模拟市场销售，分别在 4°C 贮藏 3 天后，（全反式）β-胡萝卜素增加了 20.3%，在 20°C 贮藏 14 天后增加了 34.4%。生胡萝卜中的 Z 异构体水平较低，（13Z）-β-胡萝卜素和（9Z）-β-胡萝卜素含量不到总β-胡萝卜素的 1.8%。在任何温度下贮藏时，（9Z）-β-胡萝卜素的水平都会降低，而在 4°C 贮藏时，56 天后（13Z）-β-胡萝卜素增加了 109%。烹饪显著增加了（13Z）-β-胡萝卜素和（9Z）-β-胡萝卜素的水平，并产生了（15Z）-β-胡萝卜素，而在生胡萝卜中不存在（15Z）-β-胡萝卜素。烹饪前在 4°C 贮藏 15 天或更长时间会降低（全反式）β-胡萝卜素在烹饪过程中热异构化的敏感性，从而生成的三种 Z-β-胡萝卜素异构体水平较低，而在 20°C 贮藏长达 21 天，在烹饪前后会显著增加（全反式）β-胡萝卜素水平，但对烹饪过程中 Z-异构体的生成没有影响。因此，我们得出结论，为了获得最大的健康益处，新鲜胡萝卜可以在 20°C 下贮藏 21 天或在 4°C 下贮藏 56 天，而（全反式）β-胡萝卜素不会显著减少，应生吃或煮沸 15 分钟以下，以限制 Z-β-胡萝卜素异构体的形成。
