Biochemical and technological studies on the production of isolated guar protein

Guar seeds contain 32% crude protein. Therefore, attempts were made to prepare protein isolates from guar seed flour (GSF) by extraction in different media (distilled water, salt solution, alkali solution alone or in combination) followed by a precipitation at acid pH. From the four technologies adopted, mixed salt-alkali solution was found to be the most satisfactory for extraction of protein from GSF. The highest amount of product was obtained in the mixed technology along with the highest amount of protein (87.5%). Protein isolates were also nutritionally evaluated following well-established rat bioassay procedures in a comparative study with casein as standard. The protein isolates are rich in lysine but poor in sulphur-containing amino acids such as methionine and cysteine. Protein isolates obtained by mixed salt-alkali solution showed high water and oil absorption as well as good emulsifying and foaming stability. The results indicate that protein isolates can be used as a supplementary source of protein in different food industries.