Akira Tomizawa

Low Rejection Reverse Osmosis Membrane Treatment of Peptides, Enzymatically Prepared from Cow's Milk Casein.

A peptide mixture obtained from enzymatic hydrolysis of milk casein was concentrated by using a low rejection reverse osmosis membrane (LRO membrane, sulphonated polyether sulphone composite membrane, NaCl rejection: 50%). The effect of LRO treatment on the chemical composition and amino acid composition of the peptide mixture was investigated. All samples were concentrated to a CF (concentration factor) of 3 in a batch concentration mode (BC). Furthermore, the only one sample was diafiltrated to a WDR (water dilution ratio) of 3 in a constant volume diafiltration mode (DF). (1) In the BC mode, the ash content of retentate was concentrated more than the nitrogen content. On the other hand, in the (BC+DF) mode, the result was the reverse. (2) In the BC mode, the nitrogen and ash contents and °Bx of the retentate increased with operating pressure. (3) Free amino acids decreased remarkably in the (BC+DF) mode than in the BC mode. However, a small difference between the decreasing rate of the hydrophilic and hydrophobic free amino acids was recognized in both mode. (4) LRO treatment was proved to be effective in eliminating free amino acids, but ineffective in removing bitter peptides. (Received Jul.15, 1991)