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Resistant starch (RS) is defined as 'the sum of starch and products of starch degradation not absorbed in the small intestine of healthy individuals'. This basic definition includes different types of starches that (1) are physically inaccessible, usually due to an encapsulation in intact cell walls, or (2) are naturally highly resistant to mammalian α-amylase, or (3) have been modified by hydrothermic treatments then retrograded. Interest in RS has increased significantly during the last two decades, mostly due to its capacity to produce a large amount of butyrate all along the colon. Butyrate has been observed to have a range of effects on cell metabolism, differentiation and cell growth as well as inhibition of a variety of factors that underlie the initiation, progression and growth of colon tumours. The physiological definition of RS, which seems to be nearly consensual, raises a difficulty in proper analytical quantification of RS. A number of methods have, however, been proposed and provide similar values for the RS content in most of the starch types and starchy foods. It seems, however, that some starches, proven to be partly resistant according to in vivo investigations on ileostomy subjects, could not be quantified by most of these methods. This may be due to a widespread use of glucoamylase during the first steps of these methods. Accordingly, there is an international debate on health aspects of RS and on how to quantify the RS content of food products. The present review describes aspects of classification of RS, past and current consumption, physiological effects and analytical aspects, and concludes with impacts on food and product labelling. Dietary fibre: Resistant starch: Food analysis: Food labellingAbbreviations: ACF, aberrant crypt foci; AOAC, Association of Official Analytical Chemists; BA, butyric acid; EURESTA, European Flair-Concerted Action Research Programme; RS, resistant starch; RS1, physically inaccessible starch; RS2, resistant starch granules; RS3, retrograded starch; RS4, chemically modified starch; SCFA, short-chain fatty acids. * Corresponding author: Dr Martine Champ, fax +33 2 40 67 50 12, email champ@nantes.inra.fr IntroductionResistant starch (RS) is present in a wide variety of carbohydrate-based foods and may constitute up to 15 % of the DM of a food product. Several studies indicate that its presence in food might be beneficial for health (Asp et al. 1996). RS is by definition not absorbed in the small intestine (Asp, 1992), thus it does not contribute to postprandial hyperglycaemia . Its effect on lipid metabolism has recently been investigated. When added to meals, RS may be beneficial for patients with subnormal or abnormal levels of lipaemia . Moreover, some animal studies indicate a serum cholesterol-lowering effect but no evidence of similar effects in human subjects has been demonstrated (Heijnen et al. 1996). RS is largely fermented, producing short-chain fatty acids (SCFA) and bacterial cells. It may be important for colonic epithelial cell health through effec...

Since 1953, the definition of 'dietary fibre' (DF) has evolved significantly following an international debate based on analytical progress, new nutritional and physiological knowledge and also private interests of the food industry. The overall tendency is towards an extension of the definition by including resistant starches as well as non-digestible oligosaccharides. This broadened definition is indeed based on physiological considerations as these compounds are not digested in the small intestine and become substrates for the colonic microflora, resulting in fermentation products that have a variety of local and possibly also systemic effects. A main reluctance to use this definition, however, is linked to the difficulty to quantify, with a universal method, the various compounds that fulfil the characteristics defined by this broad definition. At this point, if such a definition were adopted, there are two options, not necessarily antagonistic, which would be (1) to sum the content of NSP, resistant starches and non-digestible oligosaccharides quantified by distinct methods or (2) to use the Association of Official Analytical Chemists (AOAC) method of DF analysis (AOAC 985.29, 991.43) with complementary analyses of the different non-digestible oligosaccharides likely to be present in the food. With none of these solutions being fully satisfying from a scientific but also from a practical point of view, an innovative method has to be proposed within the next decade. The present review describes the various types of DF, effects of DF consumption on physiology and metabolism, past and current definitions, analytical aspects to measure DF and some aspects of DF claims and food labelling.

Interlaboratory performance statistics was determined for a method developed to measure the resistant starch (RS) content of selected plant food products and a range of commercial starch samples. Food materials examined contained RS (cooked kidney beans, green banana, and corn flakes) and commercial starches, most of which naturally contain, or were processed to yield, elevated RS levels. The method evaluated was optimized to yield RS values in agreement with those reported for in vivo studies. Thirty-seven laboratories tested 8 pairs of blind duplicate starch or plant material samples with RS values between 0.6 (regular maize starch) and 64% (fresh weight basis). For matrixes excluding regular maize starch, repeatability relative standard deviation (RSDr) values ranged from 1.97 to 4.2%, and reproducibility relative standard deviation (RSDR) values ranged from 4.58 to 10.9%. The range of applicability of the test is 2–64% RS. The method is not suitable for products with <1% RS (e.g., regular maize starch; 0.6% RS). For such products, RSDr and RSDR values are unacceptably high.