THE COMPOSITION AND PROPERTIES OF DATE PROTEINS

Proteins from various date cultivars were isolated by extraction with phosphate-buffered saline (PBS) and were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Dates contained a number of proteins with molecular weights ranging from 12000 to 72000. Although there were minor protein bands, most date cultivars contained two prominent bands appearing at 30000 and 72000. Upon isoelectric focusing on thin-layer polyacrylamide gels, date proteins were resolved into five or six bands in the pH range of 4 . 15-5 . 85. Sequential extraction of date pulps, first with water and later with PBS, showed that most date proteins were water-soluble albumins. When the kinetics of protein accumulation were studied, it was observed that early green dates contained very little protein. There was a rapid increase in the protein content and also in the number of protein components at a later stage in maturation. Dates from the countries of the Middle East such as Saudi Arabia, Oman and Iran were similar in their protein profiles as they contained similar complex mixtures of proteins in the molecular weight range of 12000-72000. A date variety from the USA had very little protein and also a simple protein profile with one major band appearing at 30000. Amino acid analysis revealed that dates, irrespective of their cultivars, contained all the essential amino acids. These proteins were rich in acidic amino acids and poor in sulphur-containing amino acids such as methionine and cysteine.