SR9078 - In Vivo and In Vitro Characterization of Resistant Starches from Ontario Corns and Corn-Products as Value-Added Functional Food Ingredients

Lead researcher

Dr. Qiang Liu, Agriculture and Agri-Food Canada, Guelph

Objectives

1. To develop high levels of enzyme-resistant starches from Ontario corn and corn-products as value-added functional food ingredients and to establish a standardized analytical method for determining resistant starches.
   
2. To characterize physiochemical properties of different types of resistant starches from in vivo and in vitro experiments and to establish the relationship between resistance to enzymes and molecular structure of starch.
   
3. To determine the recovery of resistant starch isolates from Ontario corn at the end of the small intestine and to quantify the amount of fermentation loss of the resistant starches in the large intestine in vivo using pigs as an animal model.
   
4. To characterize major biochemical, physiological and functional changes in response to ingesting the selected resistant corn starches in the pig model.

Expected benefits

1. Benefit to Ontario farmer: Large demand for resistant starch from food industry and other industries would lead to increased acreage of specialty corns and would benefit Ontario corn producers.
   
2. Benefit to Ontario Food Industry: will use resistant starches as value added food ingredients in the development of new functional foods.
   
3. Benefit to Ontario Consumer: preventing obesity, promoting bowel health, lowering glycemic index, decreasing the risk of colon cancer and reducing health care costs.
   

Results

Resistant starches have been introduced to human nutrition and the food industry as an increasingly important functional food ingredient in recent years. Unlike sugars and digestible starches, resistant starches resist enzymatic hydrolysis in the upper gastrointestinal tract, thus resulting in little or no direct glucose absorption. However, there is increased microbial fermentation production of short-chain fatty acids in the large intestine, a typical phenomenon of fiber consumption. Resistant starches have been shown to have equivalent and/or superior impacts on human health similar to the conventional fiber-enriched food ingredients.

These impacts include the following: 1) Decreasing dietary caloric values for body fat deposition, important in the prevention of obesity. 2) Lowering glycemic index, important in diabetes. 3) Decreasing blood cholesterol levels to control cardiovascular diseases. 4) Decreasing the risk of colon cancer through increasing short-chain fatty acid production, especially butyrate. Unfortunately, most current food products are relatively low in resistant starch content.
Generally, the resistant starch content is very low in Ontario corn varieties. However, through proper processing, milling practices and physicochemical treatments, the amount of resistant starch in Ontario corns can be dramatically enhanced.

This project focuses on developing effective processing procedures to enhance the yield of functional resistant starches and dramatically increase the market value and profit return from Ontario corn varieties and corn products, and developing research methods to evaluate physiological properties of resistant starch using an animal model.

In this three-year research project, various corn starches were employed as model starches to develop new resistant starch to meet high demand from the current market. Using annealing technique during starch isolation, resistant starch content was increased in high amylose corn starch. Regular corn starch was treated by suspending starch in an aqueous solution of hydrochloric acid for different times, then debranched using debranching enzymes, and processed by heating and storing to increase resistant starch content. By introducing citric acid to regular corn starch, the modified starch (starch citrates) acquired heat-stable resistant starch properties. For these new starches derived from corn, the thermal properties were analyzed using differential scanning calorimetry; the molecular weight profile was obtained using high performance size-exclusion chromatography. The long- and short-range orders of these materials were also examined using X-ray diffraction and Fourier transform infrared spectroscopy.

To answer the question "does resistant starch have a true physiological benefit", an animal model (pig) was used in this study to evaluate the physiological properties of different resistant starches. We modified research techniques to determine recovery starch at the end of the small intestine and to quantify the amount of fermentation loss of the resistant starches in the large intestine in vivo using pigs as an animal model by measuring cecal short chain fatty acid (SCFA) production. We also developed research method to determine plasma glucose concentration, total cholesterol in plasma, HDL and LDL, Triglycerides, and the digestive and post-absorptive utilization of phosphorus (P) and calcium (Ca) after digestion of resistant starch and other diets. We discovered that different resistant starch types resulted in different biochemical and physiological changes such as production of short chain fatty acids in pig model.

Researchers anticipate delivering a well-established production technology for effectively producing and evaluating functional resistant starches from Ontario corn and corn starch products as value-added functional food ingredients. Increasing functional resistant starch yield from Ontario corn will not only benefit consumers' health and dramatically decrease our health care costs, but also will potentially enhance returns to the corn producers and increase corn consumption. Increased acreage of specialty corns through production of resistant starches will result in an economic benefit to corn producers and enhance the agriculture and agri-food sector of the Ontario economy.

Related information

• Other projects funded through the New Directions Research Program in 2001