Partial substitution of wheat flour with soymeal in instant egg noodles

Abstract

The objectives of this research were to investigate the effects of soymeal and drying methods on the qualities of instant egg noodles. Wheat flour was replaced by soymeal at 20-30% of flour in the formula. The color (L*, a*, b*) of dough and tensile strength, protein and fiber contents and sensory attributes of cooked noodle were determined. The result showed that a* value (redness), protein and fiber contents increased but L* value (lightness), b* value (yellowness), tensile strength and sensory attributes decreased as the soymeal level increased. Based on sensory attributes and tensile strength, egg noodle substituted with 25% soymeal was the most acceptable (p<0.05) and its protein and fiber contents increased about 49% and 447%, respectively. The qualities of the noodles were improved by the addition of commercial hydrocolloid, Isagum®, at the level of 0-0.3% (w/w). The results showed that increasing the amount of Isagum® would increase the tensile strength, elasticity and overall preference scores of the noodle. The appropriated level of Isagum® addition was 0.2%. The noodle was then either dried at 60°, 70° and 80°C until its moisture content reached 8% (db) or fried at 130°, 140° and 150°C for 30, 60 and 90 seconds. The results showed that increasing the drying temperature would increase cooking loss but decrease water activity and rehydration rate of the noodle. Increasing the frying temperature and time would decrease tensile strength but increase oil absorption and rehydration rate. However the fried noodle still had beany odor. In order to overcome the problem, water in the formula was replaced by the extract of green tea (1:3 and 1:1 w/v) or Kaffir lime leave with water (1:3 and 1:1 w/v). It was found that the sensory scores on odor and overall preference increased with the Kaffir lime leave extract giving the higher scores. Thus the optimum conditions for dried noodle was drying at 80°C for 195 minutes and fried noodle with Kaffir lime leave extract (1:1, w/v) was deep-fat frying at 150°C for 60 seconds. The samples were stored (35°, 45° and 55°C) in aluminum-laminate bags and the changes of the quality properties (aw, moisture, TBA value, TPC, and yeast-mold) were evaluated. It was found that TBA and aw were the important factors in shelf-life determination. From the kinetic parameters of these quality properties the predicted shelf-life of instant dried and fried noodles were 2398 and 1625 days, respectively.