Answer to Question 1
Adding acid early in the cooking process will inhibit the softening of pectic substances.
Answer to Question 2
Legumes lack the essential amino acid methionine, but are a rich source of lysine, another essential amino acid. Most cereals contain methionine, but often lack lysine. Therefore, legumes and cereals complement each other and comprise a complete protein. When legumes and cereals are consumed together, one receives all the essential amino acids.