EFFECT OF COOKING TYPES ON THE NUTRITIONAL VALUE OF POTATO

Abstract

Two commonly consumed potato varieties, Draga and Alpha, were subjected to three different cooking methods: conventional boiling, frying and Sudanese home cooking style (stew). The purpose of this study is to evaluate the effect of the three cooking methods on potato from nutritional point of view. The evaluation was done by chemical analyses and panel tests. Boiling time was 35 minutes, frying process was carried out at 180 ْ c for 9 minutes and stew was done by traditional procedure for 33 minutes cooking time. Both the raw and cooked samples were analyzed for moisture content, protein content, fat content, ash content, carbohydrates content, fiber content and starch content. Ash was analyzed for calcium, sodium, potassium, Iron, phosphorous and magnesium. Amino acids content and sensory evaluation:(color, flavor, taste, texture and over all acceptability) were studied. The percent of protein for stew was 3.47and 3.16, of boiled potato was 1.37 and 1.4 , of fried potato was 2.6 and 2.7%, and of raw potato was 1.77 and 1.60 for Draga and Alpha respectively . Ash content of potato stew was 3.33and 3.83% ,in fried potato was 1.25 and 1.38%, of raw potato was 0.87 and 0.83for Draga and Alpha respectively, and in boiled potato was 0.5 (for the two varieties). Fiber content of stew was 0.9 and 0.8% while in fried samples was 0.5 and 0.43% , in boiled ones was 0.57 and 0.53 % ,and of raw potato was 0.47 and 0.43 for Draga and Alpha respectively . All Amino acids content after cooking decreased however in stew samples were higher than others cooking procedures .Results showed that histidine content for raw potato was 32.25 and 39.25 mg/100g, of boiled potato was 1.2 and 1.98 mg/100g, of fried potato was 1.71 and 2.5 mg/100g, and of stew was 4.68 and 5.21 mg/100g for Alpha and Draga respectively. Lysine content of raw potato was IX 56.39 and 55.9 mg/100g, and of stew was 1.49 and 1.39 mg/100g. Leucine content of raw potato was 124.23 and 119.89 mg/100g, of stew was 38.26 and 35.94 mg/100g,of fried samples was 2.79 and 3.07 mg/100g, and of boiled potato was 1.6 and 2.06 mg/100g. Isoleucine content of raw potato was 79.0 and 57.14 mg/100g, of stew was 31.86 and 26.67 mg/100g, of fried potato was 2.17 and 1.42 mg/100g,and of boiled potato was 1.8 and 1.95 mg/100g for Alpha and Draga respectively. Therionine content of raw potato was 62.9 mg/100g for Alpha variety, of stew was 6.62 and 1.32 mg/100g for Alpha and Draga, of fried potato was 0.79 mg/100g for Alpha variety, and of boiled was 0.23 mg/100g for Alpha variety. Phenylalanine content of raw potato was 114 and 118 mg/100g, of stew was 21.8 and 19 mg/100g for Alpha and Draga respectively, and of fried potato was 0.53 mg/100g for Alpha variety. Valine content of raw potato was 180and 175 mg/100g, of stew was 5.15 and 3.16 mg/100g, of fried potato was 3.03 and 2.99 mg/100g, and of boiled potato was 2.7 and 1.57 mg/100g, for Alpha and Draga respectively. Arginine content of raw potato was 82.08 and 99.5 mg/100g, for Alpha and Draga respectively, and of fried sample was 2.55 mg/100g for Draga variety. Methionine content for raw potato was 22.68 and 35.73 mg/100g for Alpha and Draga respectively While was destructed in other samples. Calcium in stew was 33.33 and 36.67 mg/100g where as in boiled potato was 14.87 and 13.33 mg/100g , in fried potato was 23.03 and 26.67 mg/100g,and of raw potato was 16.87 and16.67for Draga and Alpha respectively. Sodium was 34.6 and 35.0 mg/100g in stew , in boiled samples was 9.5 and 10.33 mg/100g , in fried potato was 4.5 and 3.33 mg/100g for Draga and Alpha respectively,and of raw potato was 24.67for the two varieties. Potassium in stew was 439 and 437 mg/100g, in fried samples was 300 and 317 mg/100g ,in boiled potato 250 and 200 mg/100g,and of raw potato was 430 and 433 for Draga and Alpha respectively. Phosphorous was 61.0 and 60.0 mg/100g in stew samples,45.0 and 44.0 mg/100g in fried samples ,47.0 and 45.567 mg/100g in boiled samples, and of raw potato was 52.0and 48 for Draga and Alpha respectively. Magnesium was 34.76 and 36.0 mg/100g in stew potato, in boiled potato was 25.67 and 26.67 mg/100g , in fried potato was 22.67 and 23.0 mg/100g ,and of raw potato was 31.77 and 34.67 for X Draga and Alpha respectively .Iron content of stew was 2 mg/100g (for the two varieties), of boiled samples was 1.93 and 1.86 mg/100g ,of fried samples was 1.97 and 1.85 mg/100g,and of raw potato was 1.76 mg/100g for the two varieties . Fat content of the fried samples was 6.40 and 6.20% while of boiled samples was 0.47 and 0.37% , in stew samples it was 2.2and 2.43 %,and of raw potato was0.53 and 0.050 for Draga and Alpha respectively . Carbohydrates content of the boiled potato was 88.77 and 88.93% where as of the stew potato was 63.94 and 63.77% , of the fried potato was 75.71 and 75.18%,and of raw potato was87.15 and 88.20 (on dry basis) for Draga and Alpha respectively . Starch content of the boiled samples was 46.56 and 44.15% while of fried samples was 42.29 and 41.13 % ,in stew samples was 32.93 and 39.73%,and of raw potato was49.45 and 49.90(on dry basis) for Draga and Alpha respectively. Results showed that stew is the best type of cooking in nutritional aspects if it is compared to boiling and frying: protein, ash, fiber, minerals (six elements) and amino acid contents, were the highest in the potato stew. While fat content was the highest in the fried potato. Carbohydrates and starch contents were the highest in the boiled potato. Organoleptic tests of cooked samples revealed that frying process is the popular methods of cooking of potato.