Process for producing slowly digestible starch

#The invention relates to a process for producing slowly digestible starch by treatment of high-amylose starch. The invention further pertains to a slowly-digestible starch product and to its dietetic use.

#Glucose is an important source of energy to the cells in the human body and is abundantly present in food ingredients. After consumption of starch or other dietetic available sources of glucose and their subsequent digestion, glucose is released in the gastro-intestinal tract, where it is rapidly and effectively absorbed from the intestinal lumen. This will usually increase glucose concentrations in blood. The change in glucose after consumption of a food is called the postprandial glucose response (PPGR), which can be measured as the area under the curve (AUC), which plots the plasma glucose concentration with time. The human body strives to maintain homeostasis of glucose levels in tissue and blood with time, in order to allow proper functioning of all cells. One important instrument to achieve glucose homeostasis is the release of insulin by the pancreas when the concentration of specific food components like glucose starts to increase. Under normal circumstances this will increase glucose transport into the cell and formation of glycogen using glucose, and trigger other metabolic changes, therewith rapidly causing the blood glucose levels to decrease to normal levels.

#A person that does not react properly on released insulin is said to be insulin-resistant. Large groups of persons suffer from insulin resistance like many obese persons, persons suffering from the so-called metabolic syndrome (or syndrome X), diabetics and many patients in hospitals or nursing homes who developed a temporary or longer lasting insulin resistance as a cause of their disease. Part of the diabetics also experience an insufficient capacity to increase insulin concentrations in blood after consumption of food (i.e., post-prandially). Persons that suffer from insulin-resistance demonstrate abnormal high postprandial glucose response, even after consumption of moderate amounts of food ingredients that comprise glucose. When high postprandial glucose concentrations occur relatively frequently and over longer periods of time, they can cause several severe health problems. Known secondary side effects, as can be found in diabetics, are problems in the cardio-vascular system, such as hypertension, atherosclerosis, poor blood supply to peripheral tissues, stroke, heart attacks etc., as well as problems in the kidney, in particular an abnormal glomerular filtration rate, and a wide range of neuropathies and retinopathies like cataract. It was also found that mortality of severe disease in hospital patients is associated with the severity of insulin resistance.

#FIG. 1 shows particle size distribution of Actistar® that has been heated for 5 minutes at various elevated temperatures and then cooled to room temperature with running tap water. Details are provided in Example 1.

#FIG. 2 shows the rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) content of Actistar® after heat treatment and then cooling to different temperatures, expressed as percentage of the weighed powder. Details are provided in Example 2.

#It was found according to the invention that the problem of instability and unattractive mouth-feel of slowly digestible starches could surprisingly be overcome by heating a resistant starch product, in the presence or absence of other food components, up to at least 120° C. for at least 3 minutes, followed by rapid cooling to a temperature below 20° C. The resulting product remains unaltered and dispersed when in liquid form for extended periods of time for at least 1 month, when stored at temperatures below 10° C.

#The product obtained by the process of the invention is a high amylose starch having a substantial content of slowly digestible starch (slow-release glucose), and a narrow distribution of relatively fine particles. It also has relatively low proportions of readily digestible starch and non-digestible starch, thus simultaneously minimizing fecal problems, caused by large volumes of resistant starch, and plasma glucose peaks, caused by high levels of readily digestible starch.

#The essential steps in the process for producing slowly digestible starch (SDS) having a useful particle size are the heating step and the cooling step. The heating should be at conditions which are equivalent of at least 120° C. for 3 minutes, up to e.g., 30 minutes. The heating temperature should be sufficient for melting most of the amylose, but not so high to degrade the amylose. This will typically imply a minimum temperature of about 110° C. (for melting purposes) and a maximum temperature of about 160° C. (to avoid degradation). It is obvious that the maximum temperature may be easily determined by the skilled person in practice. Examples of such equivalent conditions are 110° C. for 6-75 minutes, 130° C. for 1-10 minutes, 140° C. for 15 sec.-5 minutes etc. Preferred time periods are 4-30 minutes at 121° C., 3-20 minutes at 124° C., 2-15 minutes at 130° C. Although lower temperatures can be used for producing a product having the desired particles distribution, provided the reaction time is sufficient as indicated above, it is preferred to use temperatures of at least 120° C. in order to obtain high proportions of slowly digestible starch, more preferred at least 123° C., and most preferred at least 127° C.