红豆和花生大米一起煮，往往会发现红豆的颜色发生变化，从鲜红变成了暗红甚至黑色。这个现象常常让人感到困惑，究竟是什么原因导致红豆变色呢？

首先，我们需要了解红豆的化学成分。红豆中含有丰富的类黄酮化合物，如花青素和花色苷。这些化合物是天然的色素，赋予红豆鲜艳的红色。然而，当红豆和花生大米一起煮时，这些色素会发生改变，导致红豆变色。

其中一个原因是，红豆中的花青素在遇到酸性环境下容易被氧化。当花青素氧化后，它的颜色就会发生变化。而在煮红豆的过程中，通常会加入一些酸性成分，例如柠檬汁或醋，以帮助红豆更快地煮熟。这样的酸性环境促使红豆中的花青素氧化，从而导致红豆变色。

另一个原因是，红豆中的花青素与花色苷在高温下会发生反应，产生新的化合物。这些新的化合物往往是暗红色或黑色的，所以红豆在煮的过程中逐渐变暗。尤其是在长时间的煮沸过程中，红豆中的花青素和花色苷与其他成分发生更多的反应，导致红豆的颜色更加深沉。

虽然红豆的颜色发生了变化，但这并不影响其的食用价值。事实上，红豆的变色可能会为食物增添一些独特的美味。尽管有些人可能对红豆的变色感到困惑或不习惯，但红豆仍然是一种营养丰富的食物，含有大量蛋白质、维生素和矿物质。

总结起来，红豆和花生大米一起煮时，红豆的变色是由于花青素的氧化和反应所致。这些变化在酸性环境下更容易发生，以及在高温下更为显著。虽然红豆的颜色发生了改变，但它的食用价值并未受到影响。因此，无需担心红豆的变色现象，尽情享受美味的红豆花生大米煮食吧！

Translation:

When red beans are cooked together with glutinous rice and peanuts, it is often observed that the color of the red beans changes from bright red to dark red or even black. This phenomenon can be confusing, leaving one wondering why the color of the red beans changes.

Firstly, we need to understand the chemical composition of red beans. Red beans contain abundant flavonoid compounds, such as anthocyanins and anthoxanthins. These compounds are natural pigments that give red beans their vibrant red color. However, when red beans are cooked together with glutinous rice and peanuts, these pigments undergo changes that cause the color of the red beans to change.

One reason for this is that anthocyanins in red beans are easily oxidized in an acidic environment. When anthocyanins oxidize, their color changes. During the cooking process of red beans, acidic ingredients such as lemon juice or vinegar are often added to help the beans cook faster. The acidic environment promotes the oxidation of anthocyanins in red beans, resulting in a change in color.

Another reason is that anthocyanins and anthoxanthins in red beans react with other components at high temperatures, producing new compounds. These new compounds are often dark red or black in color, causing the red beans to darken during cooking. Especially during prolonged boiling, more reactions occur between anthocyanins, anthoxanthins, and other components in red beans, resulting in a deeper color.

Although the color of red beans changes, it does not affect their nutritional value. In fact, the discoloration of the red beans may even enhance the unique taste of the food. While some people may find the color change confusing or unfamiliar, red beans remain a nutritious food rich in proteins, vitamins, and minerals.

In conclusion, when red beans are cooked together with glutinous rice and peanuts, the discoloration of the red beans is caused by the oxidation and reaction of anthocyanins. These changes occur more readily in an acidic environment and are more pronounced at high temperatures. Despite the change in color, the nutritional value of red beans remains unaffected. Therefore, there is no need to worry about the discoloration of red beans and one can enjoy the delicious red bean, glutinous rice, and peanut dish wholeheartedly!