Jackson Lauren S, Tolleson William H, Chirtel Stuart J
National Center for Food Safety & Technology, Food and Drug Administration, 6502 South Archer Road, Summit-Argo, Illinois 60501, USA.
J Agric Food Chem. 2006 Sep 20;54(19):7300-4. doi: 10.1021/jf061199n.
Ricin is a potent protein toxin found in the seeds of the castor bean plant, Ricinus communis. Ricin specifically and irreversibly inactivates ribosomes, promoting cell death by inhibiting protein synthesis. It is composed of a ribosome-inactivating enzyme (A-chain) linked to a lectin (B-chain) by a single disulfide bond. Several reports indicate that ricin can be detoxified by thermal treatment; however, the conditions required for inactivation are not well characterized. In addition, little information exists on the thermal stability of ricin added to foods. The objective of this work was to determine the effects of heat treatments on the detection and toxicity of ricin added to milk- and soy-based infant formulas. Reconstituted infant formula powders containing 100 mug of ricin/mL were heated at 60-90 degrees C for up to 5 h. The heat-treated formulas were analyzed by ELISA to determine levels of ricin. The residual cytotoxicity of ricin-containing infant formula after heat treatments was determined using RAW264.7 mouse macrophage cells. The ELISA and the cytotoxicity assay indicated that ricin detection and toxicity decreased with increasing heating times and temperatures. Minimal losses in detection and toxicity were found for ricin heated at 60 degrees C for 2 h. The half-lives of ricin cytoxic activity in a milk-based infant formula at 60, 70, 75, 80, 85, and 90 degrees C were >100, 9.8 +/- 0.5, 5.8 +/- 0.9, 5.1 +/- 0.7, 3.1 +/- 0.4, and 1.8 +/- 0.2 min, respectively; the comparable values for a soy-based infant formula were >100, 16 +/- 1.6, 8.7 +/- 1.2, 6.9 +/- 1.1, 3.0 +/- 0.4, and 2.0 +/- 0.3 min. ELISA detection was a good indicator of the cytotoxicity of heat-treated ricin. The results indicate that ricin is a relatively heat stable protein and may remain toxic under some food processing conditions.
蓖麻毒素是一种存在于蓖麻植物种子中的强效蛋白质毒素。蓖麻毒素能特异性且不可逆地使核糖体失活，通过抑制蛋白质合成促进细胞死亡。它由一条核糖体失活酶（A链）和一条凝集素（B链）通过一个二硫键相连组成。多项报告表明，蓖麻毒素可通过热处理解毒；然而，使其失活所需的条件尚未得到充分表征。此外，关于添加到食品中的蓖麻毒素的热稳定性信息很少。这项工作的目的是确定热处理对添加到以牛奶和大豆为基础的婴儿配方奶粉中的蓖麻毒素的检测和毒性的影响。将含有100微克/毫升蓖麻毒素的复水婴儿配方奶粉粉末在60 - 90摄氏度下加热长达5小时。通过酶联免疫吸附测定法（ELISA）分析热处理后的配方奶粉，以确定蓖麻毒素的含量。使用RAW264.7小鼠巨噬细胞测定热处理后含蓖麻毒素的婴儿配方奶粉的残留细胞毒性。ELISA和细胞毒性测定表明，随着加热时间和温度的增加，蓖麻毒素的检测和毒性降低。在60摄氏度下加热2小时的蓖麻毒素在检测和毒性方面损失最小。在以牛奶为基础的婴儿配方奶粉中，蓖麻毒素细胞毒性活性在60、70、75、80、85和90摄氏度下的半衰期分别为>100、9.8±0.5、5.8±0.9、5.1±0.7、3.1±0.4和1.8±0.2分钟；以大豆为基础的婴儿配方奶粉的相应值为>100、16±1.6、8.7±1.2、6.9±1.1、3.0±0.4和2.0±0.3分钟。ELISA检测是热处理后蓖麻毒素细胞毒性的良好指标。结果表明，蓖麻毒素是一种相对耐热的蛋白质，在某些食品加工条件下可能仍具毒性。
