Bulking and Fat-Replacing Agents - Sweeteners: Nutritional Aspects, Applications, and Production Technology - page 402

in the small intestine but reaches the colon, where it provides additional beneits, including the
growth of probiotics (Vasiljevic and Shah 2008). The fermentation of resistant carbohydrates by
anaerobic bacteria results in the release of short-chain fatty acids (SCFAs), including acetic, pro-
pionic, and butyric acids, which are the respiratory fuel of cells lining the colon (Cummings and
Englyst 1995).
Resistant starch has been classiied into four general types, termed R1-R4, mainly based on
the level of digestibility and physical properties: (1) RS1—physically inaccessible starch, which
is entrapped within whole or partly milled grains or seeds; (2) RS2—some types of raw starch
granules and high-amylose starches; (3) RS3—retrograded starch as a result of a food process;
and (4) RS4—chemically modiied starches to improve their resistance to enzymatic digestion
(Baixauli et al. 2008; Sanz et al. 2009). The RS1 classiication is assigned to resistant starch when
it is physically inaccessible to digestion (Hernández et al. 2008). This type of resistant starch is
heat stable under a variety of conventional cooking operations, which has broadened their applica-
tion (Sajilata et al. 2006). The structural and conformational properties of RS2 starches prevent
digestion (Hernández et al. 2008). In the diet, this starch is consumed in foods such as banana
(Sajilata et al. 2006). The RS3 form is generally formed during the retrogradation of starch gran-
ules (Wepner et al. 1999) by heating starchy foods and then keeping them at low or room tempera-
ture (Hernández et al. 2008). This particular type is heat stable, which expands its applicability
in a wide variety of conventional foods (Haralampu 2000). The application of moist heat during
food processing may degrade the RS1 and RS2 types but may actually produce the RS3 form
(Faraj et al. 2004). In addition to the three main types of RS, chemically modiied starch has been
assigned as RS4 type, similar to resistant oligosaccharides (ROs) and PDs (Wepner et al. 1999).
These starches have been chemically modiied by conversion, substitution, or cross linking in such
a manner as to decrease their digestibility.
Resistant starches have desirable physical properties, including swelling, thickening, gelling, and
water-binding capacity, which make them a useful ingredient in a variety of foods. These starches
are characterized by a small particle size, white appearance, and bland lavor, all of which contrib-
ute to improved handling in processing and appropriate texture in the inal product (Sajilata et al.
2006). For these properties, most resistant starches can replace lour on a one-for-one basis without
detrimentally affecting dough rheology. As mentioned above, the processing conditions can affect
the content of the resistant starch by inluencing its gelatinization and retrogradation (Thompson
2000). Theoretically, it is achievable to increase its content in foods by modifying the process-
ing conditions such as pH, heating temperature and time, number of heating and cooling cycles,
freezing, and drying (Sajilata et al. 2006). Commercially manufactured resistant starches are not
affected by processing and storage conditions. For example, the amount of RS2 in green bananas
decreases with the extent of ripeness; on the other hand, a commercial form of RS2, Hi-maize, does
not undergo this transformation (Nugent 2005). The inclusion of high quantities of resistant starches
into products is driven with a multitude of effects, including physical and physiological functional-
ity and processing stability.
13.4 MaLtODeXtrINS
As described above, starch consists of two fractions: amylose and amylopectin. Starch in foods
affects texture, viscosity, gelling properties, adhesion, binding, water-holding capacity, ilm forma-
tion, and product homogeneity. Starch has also been used in the pharmaceutical industry, textiles,
alcohol-based fuels, and adhesives. Novel uses of starch include low-calorie substitutes, biode-
gradable packaging materials, thin ilms, and thermoplastic materials with improved thermal and
mechanical properties (Biliaderis 1998). Starch is frequently modiied to overcome shortcomings
of native starches and, thus, diversify the utilization of starch in industrial applications. Starch