Some varieties of resistant starch made from potatoes helps fortify bread products.

Resistant Starch

Also known as Enzyme-resistant Starch


What is Resistant Starch?

Resistant starch (RS) is defined as the portion of starch and starch products that resist digestion in the gastrointestinal tract. It can be classified as a dietary fiber due to its desirable physiological attributes.1

Sources of this kind of starch are:

  • Oats
  • Raw potato starch
  • Legumes
  • Green bananas
  • High-maize flour
  • Retrograded starches

Origin

The term “resistant starch” was first introduced by Englyst et al. in 1982 to describe a small fraction of starch that is resistant to hydrolysis by exhaustive alpha-amylase and pullulanase activity in vitro.2

Nutrition

Many health benefits are associated with eating resistant starch. By escaping digestion in the small intestine, fermentation of this starch in the large intestine produces organic and short chain fatty acids. These metabolites provide important biological effects such as:

  • Improved glycaemic
  • Controlled insulinemic responses
  • Bowel health
  • Reduced blood glucose spikes after a meal3

Average daily intake of RS in the US is 6 g,4 which is quite low as the Daily Value is 25-28 grams of dietary fiber.5

Types/Variations

Resistant starch can be classified into five categories:

RS I: physically inaccessible due to entrapment in the plant storage cells.  Examples include whole or partially milled cereal grains such as muesli, coarsely ground seeds and legume kernels.

RS II: includes native RS such as  high-amylose maize or raw banana starch. After cooking, most of these starches may become highly digestible due to gelatinization.

RS III: retrograded starches produced during food processing and manufacturing. Examples include cooked and cooled potatoes, stale bread and high amylose corn starch.

RS IV: chemically modified starch formed by chemical or enzymatic cross-linking.

RS V: refers to thermally-stabilized amylose-lipid complexes.

Commercial production

Resistant starch is naturally available from numerous crops including some maize hybrids, native potato starch, tapioca starch, kidney beans, corn flakes, rye crispbread, wheat bran, etc. It can also be manufactured by thermal processing of native starches.

Application

Bakery products are typically formulated with  RS II and RS III types. The low water-holding capacity of RS helps with crispness and expansion of baked goods.

Commercial starches with high RS levels may negatively affect the crumb color, external appearance and symmetry of bread loaves. Incorporating transglutaminase (TG) and/or glucose oxidase or xylanase enzyme helps in overcoming these challenges by improving gluten strength and its water holding capacity.6

Vital gluten at 5-15% concentrations can also be added to doughs containing cross-linked RS starch to strengthen and stabilize the dough and improve bread loaf volume.7

FDA Regulation

Approved methods for preparing resistant starches and their usage limits are listed by the FDA  (Title 21 Part 172.892).8 In these regulations, the chemicals and enzymes used to treat starch are listed and their limitations are included. The US, Canada, Mexico, Chile, EU, Australia and Japan are some countries that have authorized chemically modified RS in the food industry.

References

  1. Eerlingen, R.c, and J.a Delcour. “Formation, Analysis, Structure and Properties of Type III Enzyme Resistant Starch.” Journal of Cereal Science 22.2 (1995): 129-38.
  2. Sajilata, M. G., Singhal, Rekha, S., and Kulkarni, Pushpa, R. Resistant Starch- A Review.Comprehensive Reviews in Food Science and Food Safety. 5 (2006): 1-17.
  3. Nugent, A. P. Health properties of resistant starch. Nutrition Bulletin. 30 (2005): 27-54.
  4. Murphy, Mary M., Judith Spungen Douglass, and Anne Birkett. “Resistant Starch Intakes in the United States.” Journal of the American Dietetic Association 108.1 (2008): 67-78.
  5. “Dietary Fiber.” Accessdata. Fda. Gov. Food and Drug Administration, 6 June 2016. www.accessdata.fda.gov/scripts/InteractiveNutritionFactsLabel/dietary-fiber.html Accessed 6 Oct. 2016.
  6. Altuna, Luz, Pablo D. Ribotta, and Carmen C. Tadini. “Effect of a Combination of Enzymes on the Fundamental Rheological Behavior of Bread Dough Enriched with Resistant Starch.” LWT – Food Science and Technology 73 (2016): 267-73.
  7. Hung, Pham Van, and Naofumi Morita. “Dough Properties and Bread Quality of Flours Supplemented with Cross-linked Cornstarches.” Food Research International 37.5 (2004): 461-67.
  8. “21CFR172.892.” CFR – Code of Federal Regulations Title 21. 1 Apr. 2016. www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=172.892 Accessed 6 Oct. 2016.