Rice Protein

Quantity and quality of rice protein

The rice caryopsis, more simply called bean, contains about seven percent protein; although it is a modest quantity, rice proteins are qualitatively superior to those of any other cereal.

However, like all vegetable protein sources (soy, beans, cereals and vegetables), rice proteins are deficient in some essential amino acids, specifically lysine and tryptophan as regards the proteins of polished rice, and only lysine for those of brown rice. This last amino acid constitutes 4% of the rice proteins, twice the percentage of that contained in wheat or corn flour. Even the percentages of threonine and methionine, two other essential amino acids, are very high compared to those of other cereals.

To fill the qualitative deficiencies of rice proteins, it is sufficient to supplement the diet with legumes, or animal proteins (fish, meat, eggs and dairy products).

The biological value of rice proteins is higher than that of any other cereal, including wheat, which compensates for the slightly lower protein content. According to FAO data, the biological value of rice proteins is equal to 69 (compared to 49 of wheat and 44 of corn).

Tab.1 Content in essential amino acids in some foods and relative biological value of proteins

Food	isoleucine	Leucine	Lysine	Methionine	Fenialalanina	threonine	Tryptophan	Valine	Biological value
Egg	393	551	436	210	358	320	93	428	100
Bean	262	476	450	66	326	248	63	287	44
Wheat	204	417	179	94	282	183	68	276	62
Naus	230	783	167	120	305	225	44	303	49
Potatoes	236	377	299	81	251	235	103	292	34
Rice	238	514	237	145	322	244	78	344	69
Soy	284	486	399	79	309	241	80	300	67

Quantity and quality of rice proteins obviously vary according to the variety and industrial process suffered by caryopses; they are for example superior in the integral product and parboiled compared to the polished one.

The absence of gliadin and glutenin fractions typical of wheat - which allow the formation of gluten but which in many cases cause serious food intolerances (for example, celiac disease) - makes rice protein a food suitable for everyone, even those who suffer of celiac disease.