Effect Of Chinese Cooking On The Content Of Resistant Starch

China is rich in potatoes, with the annual output of about 60 million ton. Patatoes are also one of the most consumed foods in the daily diet by Chinese people. Potatoes are high in nutritional value, which have high content of digestible starch, resistant starch, protein, fat, amino acid and so on. The contents of resistant starch and other main nutrients in potatoes before and after five Chinese cooking methods (stir-frying, stewing after frying, deep-frying, steaming and boiling) were investigated, which provided theory evidences for Chinese residents to evaluate their daily diet nutritions and to select the right cooking methods. The potatoes were washed, pared off and sliced into pieces before cooking. The content of resistant starch was detected by Akerberg AKE method, while the quantities of other nutrients (starch, protein, fat, water, etc.) were evaluated using GB methods. The effects of different cooking conditions on the content of resistant starch were also detected in the research. The cooked potatoes were then refrigerated and microwave heated, after which the changes in the content of resistant starch were investigated. The main results were presented as follows:1. The contents of resistant starch in potatoes, sweet potatoes, yams and taros were detected by Akerberg AKE method. The content of resistant starch in them were 73.08g/100gTS,47.90 g/100gTS,55.49 g/100gTS,57.25 g/100gTS, respectively.2. Different cooking methods had different impacts on the content of resistant starch and other nutrients in potatoes. The contents of resistant starch in potatoes after different cooking methods (stir-frying, stewing after frying, deep-frying, steaming and boiling) were 25.26g/100gTS,22.21 g/100gTS,21.76 g/100gTS,18.70 g/100gTS and 17.43 g/100gTS, respectively. For the methods of stir-frying and stewing after frying the reserve factors of resistant starch were high,34% and 30%, respectively. However, in boiling procedure, the resistant starch degraded much more and the reserve factor was only 24%. The contents of total starch and protein in potatoes after cooking both decreased compared with the fresh potatoes, whereas the concentration changes of water and fat were not in the same rules with starch and protein.3. Different cooking conditions had different impacts on the content of resistant starch in potatoes, such as cooking time, quantity of oil and water. The factor of cooking time had the most impact on the change of resistant starch in potatoes. The difference between the content of resistant starch in potatoes after boiling in hot water and boiling in cold water was little. But the difference between high pressure and atmosphere pressure was large. The factors of quantity of adding oil and water had little effect on the resistant starch.4. The contents of resistant starch in cooked potatoes significantly increased after storing at 4℃for 12 hours. The cooked potatoes were microwave heated after storing at 4℃for 12 hours and the content of resistant starch decreased after detected.