Abstract
The characteristics of the phosphatase activity of dried soup mixes and their raw materials were examined and the stability of 5'-ribonucleotides was studied. The results are as follows. (1) Some of spices, such as red pepper, thyme and sage, had fairly high phosphatase activity, which affected the stability of 5'-ribonucleotides. Their phosphatase was perfectly inactivated by heating at 80°C for 10min. (2) Thickening agents with certain treatments such as roller skim milk powder and starches, had no phosphatase activity, but those from natural sources such as full fat soy flour, soft wheat flour and corn flour had high phosphatase activity. The stability of 5'-ribonucleotides depended on the moisture level of samples which had the phosphatase activity and it is certain that 5'-ribonucleotides were decomposed when samples absorbed more moisture than certain amounts. (3) 5'-Ribonucleotides were very stable in the dried soup mix, when the raw materials used had no phosphatase activity. Thus, it is desirable to use the raw materials which received heat-treatments or purification. If the raw materials with phosphatase activity are used, the moisture level of the dried soup mix should be kept below 5-8% to maintain the stability of 5'-ribonucleotides.
