By Karl Kruszelnicki
The Latin name for the cacao tree, from which chocolate comes, is Theobroma cacao. The name means “food of the gods”, and chocolate-lovers agree. But people also love their pets. So should you share the love around and feed your pet some chocolate? Definitely not, because chocolate can kill pets, especially dogs.
Chocolate comes from the cacao tree, which grows some 6-12 metres tall. After about four years, the mature cacao tree begins to make its fruit—the pod. There are up to 70 pods, each about 35 centi- metres long, and ranging in colour from deep purple to bright yellow. Inside each pod are about 20-60 beans, each about 2-3 centimetres long. This is the Mother Lode2 of Chocolate. The farmers remove the beans and bury them in large piles, so they can ferment. This is when the flavour begins to develop. After a few days, they are roasted, to remove some water, to develop the flavour further, and to drop the acidity and the bitterness. Then the beans are popped3 out of their shells and ground up4. In the World of Chocolate, there is a special word called “conching5”, which means to stir and aerate6. Depending on the quality, the gluggy7 brown chocolaty8 mess is conched for between 4 and 72 hours, while being heated to between 55°C and 88°C. If you cool this down into 5 kg blocks, you have your basic chocolate.
Baking chocolate and dark chocolate are usually quite bitter, because they have no or little sugar added. Sweet chocolate has (of course) sugar added, as well as a whole bunch of other flavourings such as vanilla. To get milk chocolate, you add milk. The baking and dark chocolate have the highest amounts of pure cacao, up to 85%.
Chocolate was drunk by the Preclassic Maya9 some 2,500 years ago. They frothed10 it into a foam by repeatedly pouring the liquid from one vessel to another. By the time of the Spanish Conquest of Middle and South America, chocolate was drunk with most meals, and usually mixed with another ingredient such as water, honey and chilli. Columbus in 1502 brought back some cocao beans to Spain. The Spaniards11 did manage to keep the secret of their bitter but delicious drink for a century. Chocolate remained a drink until 1847, when J. S. Fry & Sons12 came up with a solid form of chocolate.
Cacao has over 500 different chemicals, including a few in the methylxanthine class. The two methylxanthines that we humans seem to love are caffeine and theobromine. The theobromine seems to be the dog killer.
The toxic dose of theobromine is 100-150 mg/kg of body weight. It turns out that different types of chocolate have different amounts of theobromine. Milk chocolate has 154 mg of theobromine for each 100 gm of chocolate, while for the same weight, semisweet chocolate has (528 mg) 3-4 times more, with bitter baking chocolate carrying a massive (1,365 mg) 9 times more of theobromine.
So for your “average” 20-25 kg family dog, the fatal dose of chocolate is about 1.5 kg of milk chocolate, about 400 gm of semisweet chocolate, and 140 gm of baking chocolate—which is not a lot of chocolate for a dog to scoff13. The dog could suffer seizures14 or convulsions15, blueish skin and a fast irregular heart rate as it heads down theobromine’s lethal16 pathway. You definitely need to see a vet immediately, who may try to stabilise the dog’s breathing, heart rate, electrolytes, acid-base balance and over-excited nervous system, as well as remove any remaining chocolate from the dog’s gut. So yes, chocolate can kill your dog.
Chocolate can have similar effects on humans, but again, usually only with massive overdoses.
However, in small doses, chocolate definitely seems to be good for you—especially if it’s dark chocolate. Cacao contains chemicals that fight the bacteria that cause tooth decay. On the other hand, milk chocolate is rich in sugar that feed these bacteria. Other good chemicals in chocolate keep the blood vessels both elastic17 (which is good) and wide-open (which is also good). And of course, that matches your kids’ mouths, which are also elastic and wide-open for chocolate ...
巧克力来自可可树，可可树的拉丁学名是Theobroma cacao，意思是“神的食物”，喜爱巧克力的人会有同感。而人们也爱自己的宠物。那么你该与宠物一起分享你喜爱的巧克力吗？当然不行，因为巧克力会毒死宠物，特别是狗。
巧克力来自可可树，这种树可长到6至12米高，四年左右成熟，成熟后便开始结果———荚果。一棵树的荚果可达70个，每个约35厘米长，颜色从深紫色到亮黄色。每个荚果内约有20至60粒可可豆，每粒可可豆约长2至3厘米，这就是巧克力的母体。农夫们取出荚果内的可可豆，将它们堆成大堆发酵，巧克力的香味就此开始产生。几天后进行烘烤处理，去除一些水份，使其香味更浓，并去掉些酸味和苦味。此时可可豆脱壳而出，并被碾细磨碎。在巧克力世界里，专门有个叫“conching”的词来表达这一过程，意思是对巧克力进行搅拌揉捏并使其充满气体。褐色巧克力浓浆被加热到55至88摄氏度搅拌时汩汩作响，根据巧克力品质的不同，搅拌时间也从4小时到72小时不等，当冷却为5公斤的大块后，就成了最初的巧克力。
可可浆和黑巧克力通常因不加糖或只加少量的糖而相当苦。甜味巧克力当然是加过糖的，还要加上各种各样的调味品，比如香草。要想得到牛奶巧克力，就要加进牛奶。可可浆和黑巧克力的纯巧克力含量最高，达85%。
大约2500年前，“前古典玛雅”时期的人就已经饮用巧克力，他们将巧克力反复从一个容器倒向另一个容器，使其起泡沫。西班牙人征服中、南美洲时，几乎每餐都饮用巧克力，而且通常与另一种成份混在一起，如水、蜂蜜和甜椒。哥伦布于1502年将一些可可豆带回西班牙，西班牙人将这种苦而美味的饮料秘方保存了一个世纪。巧克力一直是饮料，直到1847年英国J. S. Fry & Sons巧克力工厂才开始生产固态巧克力。
可可豆含有500多种不同的化学成份，其中包括几种甲基黄嘌呤类化学物质，似乎受人喜爱的两种是咖啡因和可可碱，可可碱可能是犬科动物的“杀手”。
可可碱的中毒剂量是每公斤体重100 到150毫克，不同品种巧克力中可可碱的含量不同。每100克牛奶巧克力中含154毫克可可碱，同样重量的低甜度巧克力则含有528毫克，是前者的3至4倍，而同样重量的苦味可可浆含有9倍以上的可可碱，约1365毫克。
因此对于一般重20至25公斤的家犬，牛奶巧克力的致命剂量约为1.5公斤，低甜度巧克力的致命剂量为400克，可可浆的致命剂量为140克———这个量对贪吃的狗来说不算多。狗中毒后会出现痉挛、抽搐、皮肤发青，以及心跳加速、心率不齐等症状，并行将死亡。这时一定要立即去看兽医，医生可以设法稳定其呼吸、心率、电解质、酸碱平衡水平以及过分兴奋的神经系统，并从狗的内脏里清除一切残留的巧克力。所以，巧克力确实会将你的狗致于死地。
巧克力对于人类也会产生类似的影响，但通常只是在大量食用的情况下。
不过，看来少量巧克力对人显然是有益的，特别是纯巧克力。可可所含的化学物质能够杀死引起蛀牙的细菌，相反，牛奶巧克力里含有的丰富糖份却正是这些细菌的食物，巧克力中其他一些对人体有益的化学成份能使血管保持弹性和舒张，这些对于人体健康都是有益的。当然，巧克力也适合孩子的口味。对巧克力来说，孩子们的嘴也灵活而畅通无阻……
Notes:
1. toxic 有毒的
2. Mother Lode （地质学名词）母脉, 主矿脉，这里指巧克力的来源
3. pop 使砰（或啪）的一声爆裂（或打开）
4. grind up 磨碎，磨细
5. conching搅拌揉捏（巧克力）
6. aerate 使充满气体
7. gluggy发汩汩声的
8. chocolaty加巧克力的，如巧克力般的
9. Preclassic Maya学术界将公元250－900年称作“古典玛雅”（Classic Maya）时期，在此之前是“前古典玛雅”（Preclassic Maya）时期。
10. froth 使起泡沫
11. Spaniard西班牙人
12. J. S. Fry & Sons英国一家巧克力工厂，建于1728年
13. scoff 贪吃，狼吞虎咽
14. seizure （疾病）发作
15. convulsion抽搐
16. lethal 致命的
17. elastic有弹性的，灵活的 |
