Some history of chemistry
It is sometimes said that “albumin coagulates when meat is cooked”. Wrong!
The story begins at the end of the XVIII th century when chemists began analyzing matter such as egg
whites, which “coagulate”. They observed that some other material from animals had the same ability
to coagulate and they published that these materials were containing “albumin”.
But at the turn of the XIX th century, chemistry was turned over by the discovery of “plant albumin”: in
plants such as lentils, chemists discovered other materials that could also coagulate and had some
common properties with “meat albumin”. This was a revolution, as it showed that animals and plants
had something in common, contrary to what some interpretation of the Bible said.
Slowly, chemistry improved, and chemists discovered that “albumins” contain nitrogen. But it appeared
that all nitrogen containing compounds were not of the same kind. At the beginning of the XX th
century, it appeared that “proteins” can be very different, and the name “albumin” was kept only for
some of the proteins: small, coiled ones. Blood contains some, called “serum albumin”, and egg white
also contains some “albumins”, such as ovalbumin.
But when meat is cooked, it’s not because of “albumin coagulation”. This coagulation of meat occurs
because of the proteins inside muscular fibres: actin and myosin mostly.
Forget about albumin: it’s a centuries old thing!
Vegetables and fruits
Vegetables and fruits: these come from plants, and we know that there is a difference between
animals and plants. So it is no wonder that the chemistry is also different.
What remains true is that plant tissue also contains a lot of water: we all know fruit juice, but also
juices from various vegetables.
Another difference: plant contains “fibres”. You can seem them by grinding leeks and soaking them.
On filtering, you recover a hard and fibrous material. It is mostly composed of cellulose, the same as in
cotton (cotton is pure cellulose)!
One property of cellulose is that it doesn’t dissolve in water (try!) and it is not easily chemically