Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan, United States of America.
Department of Animal Science, Michigan State University, East Lansing, Michigan, United States of America.
PLoS One. 2020 Feb 26;15(2):e0229340. doi: 10.1371/journal.pone.0229340. eCollection 2020.
There is increased consumer interest in grass-finished beef (GFB) with retail sales reaching $272 million in 2016. GFB contains higher omega-3 fatty acid levels compared to grain-finished beef, but variations in fatty acid (FA), mineral, and antioxidant content by producers and season is poorly documented. Hence, GFB samples from cattle finished in both fall and spring were obtained from four producers representing several US sub-regions. FAs were extracted using microwave-assisted extraction, derivatized to methyl-esters, and quantified using gas chromatography-mass spectrometry. Mineral content was quantified using coupled plasma mass-spectrometry and antioxidants were quantified via UV-absorption. Overall, total omega-3 FA content was greater in beef from cattle finished in the spring (13.4 mg/100g beef) than the fall (10.3; P<0.001). Additionally, α-tocopherol was present in greater amounts in spring-finished beef (259 vs. 223 ug/100g beef, P<0.001) as was the micromineral selenium (18.2 vs. 17.3ug/100g beef, P = 0.008). Despite using the same feed in fall and spring, cattle from producer 4 had higher total omega-3, omega-6, and total polyunsaturated fatty acids in spring compared to fall (P<0.010). These results suggest there are seasonal differences in omega-3 and omega-6 fatty acids, minerals and antioxidants in grass-finished beef independent of finishing diet.
消费者对草饲牛肉（GFB）的兴趣日益增加，2016 年零售额达到 2.72 亿美元。与谷物育肥牛肉相比，GFB 中的欧米伽-3 脂肪酸水平更高，但生产者和季节对脂肪酸（FA）、矿物质和抗氧化剂含量的变化记录很少。因此，从四个代表美国几个次区域的生产者处获得了秋季和春季育肥的牛的 GFB 样本。使用微波辅助提取提取 FA，衍生为甲酯，并使用气相色谱-质谱法进行定量。使用等离子体质谱法定量矿物质含量，通过紫外线吸收法定量抗氧化剂。总的来说，春季育肥牛的总欧米伽-3 FA 含量（13.4mg/100g 牛肉）高于秋季（10.3；P<0.001）。此外，春季育肥牛肉中的α-生育酚含量更高（259 比 223ug/100g 牛肉，P<0.001），微矿物质硒含量也更高（18.2 比 17.3ug/100g 牛肉，P = 0.008）。尽管在秋季和春季使用相同的饲料，但来自生产者 4 的牛在春季的总欧米伽-3、欧米伽-6 和总多不饱和脂肪酸含量高于秋季（P<0.010）。这些结果表明，草饲牛肉中的欧米伽-3 和欧米伽-6 脂肪酸、矿物质和抗氧化剂存在季节性差异，与育肥饮食无关。
