Why squeeze lemon into spinach, water turns red?

In water spinach contains some substances such as color indicator, in alkaline environment it is green, and acid environment will turn yellow or red.

Lemon juice contains a weak organic acid, citric acid is quite high up to 8% of dry weight in the fruit, so when squeezing lemon will change the acidity of the vegetable juice.(Illustration).

The bowl of boiled water spinach will taste better if it is squeezed with lemon juice, then the blue water will turn red. According to expert Nguyen Duc Phuong (Hanoi National University), in water spinach contains an amount of alkali Ca (OH) ₂ , chlorophyll reacts as a color indicator.

While lemon juice contains weak organic acid, citric acid is quite high up to 8% of dry weight in the fruit, so when squeezing lemon will change the acidity of the vegetable juice. This makes the color of water spinach changes from green to yellow or red, depending on the acidity.

This expert warns, with water spinach sprayed with pesticides or growth, toxic chemicals that remain in the trunk, vegetable leaves will make the vegetables not change color, if there is not significant when squeezing lemon juice. This is also one of the signs of whether or not vegetables are clean.