Initially, when the word "resistant starch" was coined, it was for the purpose of naming that fraction of starch which did not undergo hydrolyzation with alpha amylase and pullulanase even after 20 min of incubation in vitro. However, now it is more commonly used to refer to that fraction of starch which cannot be digested by the small intestine and is hence not available for absorption by the body.
There exist 4 different types of resistant starch (RS) fractions.
RS1- These starches have a physical coat or covering and are hence protected from the attack of enzymes. Eg: Whole grains, seeds, legumes. These can be made available by processes that interfere with their protection, like milling( in case of grains). Chemically, it can be measured as the difference between the glucose released due to enzyme digestion when the food sample is homogenized and when it is not homogenized. Due to physical protection, these foods are generally heat stable.
RS2- These structures have a relatively compact granular form thus allowing little water or enzymes to penetrate their insides and therefore resistant to breakdown. Eg: raw potatoes, green bananas. However, food processing can soften these starches. Chemically, their content is calculated as the difference between the glucose released upon enzymatic digestion from a boiled, homogenized sample to that of a non boiled non homogenized sample.
RS3- It is the most resistant starch fraction and is not at all susceptible to digestion by pancreatic amylase. It is measured as that fraction which is dispersed by Potassium hydroxide and dimethyl sulfoxide.
RS4- This starch contains novel chemical bonds that are formed because of interaction between the food and the chemical agents or additives used in its processing.
Certain activities like autoclaving of the food, parboiling, baking may increase the RS content of certain foods. On the other hand, microwave cooking, germination of legumes, fermentation may help reduce the RS content.
RS has a small particle size, bland in taste and low water holding capacity. They can be used as a dietary fiber or added to other foods to improve its fiber content or lower its calorific value. It is digested over a long period of time and is thus beneficial to be used by diabetics. It can also function as a laxative.
Reference:
http://onlinelibrary.wiley.com/doi/10.1111/j.1541-4337.2006.tb00076.x/pdf
There exist 4 different types of resistant starch (RS) fractions.
RS1- These starches have a physical coat or covering and are hence protected from the attack of enzymes. Eg: Whole grains, seeds, legumes. These can be made available by processes that interfere with their protection, like milling( in case of grains). Chemically, it can be measured as the difference between the glucose released due to enzyme digestion when the food sample is homogenized and when it is not homogenized. Due to physical protection, these foods are generally heat stable.
RS2- These structures have a relatively compact granular form thus allowing little water or enzymes to penetrate their insides and therefore resistant to breakdown. Eg: raw potatoes, green bananas. However, food processing can soften these starches. Chemically, their content is calculated as the difference between the glucose released upon enzymatic digestion from a boiled, homogenized sample to that of a non boiled non homogenized sample.
RS3- It is the most resistant starch fraction and is not at all susceptible to digestion by pancreatic amylase. It is measured as that fraction which is dispersed by Potassium hydroxide and dimethyl sulfoxide.
RS4- This starch contains novel chemical bonds that are formed because of interaction between the food and the chemical agents or additives used in its processing.
Certain activities like autoclaving of the food, parboiling, baking may increase the RS content of certain foods. On the other hand, microwave cooking, germination of legumes, fermentation may help reduce the RS content.
RS has a small particle size, bland in taste and low water holding capacity. They can be used as a dietary fiber or added to other foods to improve its fiber content or lower its calorific value. It is digested over a long period of time and is thus beneficial to be used by diabetics. It can also function as a laxative.
Reference:
http://onlinelibrary.wiley.com/doi/10.1111/j.1541-4337.2006.tb00076.x/pdf
No comments:
Post a Comment