42
important components, one such healthier component being Resistant starch (RS)
(Mikulíková, Masár and Kraic 2008), that is widely used as a functional ingredient
in a range of foods containing high dietary fiber levels and slowly digestible starch
(SDS). SDS also forms an important component of dietary fiber due to its incomplete digestion and absorption properties that ultimately leads to its partial fermentation in the large intestines (Marteau et al. 2001).
Definition
The growing importance of functional foods has lead to an increased consumer
demand for nutritious, healthy and beneficial foods. Starch and starch derivatives
being the major food components contribute an energy reserve roughly about
60–70%. Resistant starch (RS) refers to the fraction of starch and starch products
that resist digestion as they pass through the gastrointestinal tract (Nugent 2005).
Resistant starch on a whole is that part of dietary fiber that is not fully hydrolyzed
to D- glucose or sugar after an hour or 120 min after being consumed but gets fermented in the distal part of the large intestine releasing some important fatty acids
including acetate, propionate and butyrate (Fergusan et al. 2007). The resulting
short chain fatty acids get absorbed in distal part of large intestines and account for
almost 5–10% of energy (Nordgaard and Mortensen 1995). On an average 80–90%
of the RS of the total food components ingested that passes into the human colon is
fermented by microbial fauna rest is excreted via feacal elimination. As such RS
significantly shifts the positive balance of microbial colonies that decreases the fermentation of non starchy components hence increasing the feacal bulk (Cummings
et al. 1996). Many studies have shown that RS is a linear molecule of α-1,4-Dglucan, essentially derived from the retrograded amylose fraction, and has a relatively low molecular weight (1.2 × 10
5
Da) (Tharanathan 2002). RS has a small
particle size, white appearance and bland flavor. RS also has a low water-holding
capacity. It has desirable physicochemical properties such as swelling, viscosity
increase, gel formation, and water-binding capacity, making it useful in a variety of
foods (Fausto et al. 1997). RS is an extremely broad and diverse range of materials
and a number of different types exist (RS1–RS4) (Nugent 2005). The early classification involved only three forms of starch (Englyst and Cummings 1987; Englyst
et al. 1992): RS 1—physically inaccessible starch; RS 2—starch of raw (nongelatinised) granules of some plant species; RS 3—retrograded starch. In successive
years, those forms were supplemented with another one (Eerlingen and Delcour
1995; Haralampu 2000), namely—RS 4—chemically or physically modified starch.
Presently, all the four types are categorized according to their physicochemical
characteristics (Nugent 2005). RS1 type of starches are resistant to GI tract conditions due to physical inaccessibility offered by seed coats and outer walls of partly
processed grains and dense starchy foods making it stable to almost all cooking
operations (Sajilata et al. 2006). RS2 represents that fraction of starch that is packed
tightly inside the starch granule in such a way rendering it difficult for enzymes to
G. Akhtar et al.
important components, one such healthier component being Resistant starch (RS)
(Mikulíková, Masár and Kraic 2008), that is widely used as a functional ingredient
in a range of foods containing high dietary fiber levels and slowly digestible starch
(SDS). SDS also forms an important component of dietary fiber due to its incomplete digestion and absorption properties that ultimately leads to its partial fermentation in the large intestines (Marteau et al. 2001).
Definition
The growing importance of functional foods has lead to an increased consumer
demand for nutritious, healthy and beneficial foods. Starch and starch derivatives
being the major food components contribute an energy reserve roughly about
60–70%. Resistant starch (RS) refers to the fraction of starch and starch products
that resist digestion as they pass through the gastrointestinal tract (Nugent 2005).
Resistant starch on a whole is that part of dietary fiber that is not fully hydrolyzed
to D- glucose or sugar after an hour or 120 min after being consumed but gets fermented in the distal part of the large intestine releasing some important fatty acids
including acetate, propionate and butyrate (Fergusan et al. 2007). The resulting
short chain fatty acids get absorbed in distal part of large intestines and account for
almost 5–10% of energy (Nordgaard and Mortensen 1995). On an average 80–90%
of the RS of the total food components ingested that passes into the human colon is
fermented by microbial fauna rest is excreted via feacal elimination. As such RS
significantly shifts the positive balance of microbial colonies that decreases the fermentation of non starchy components hence increasing the feacal bulk (Cummings
et al. 1996). Many studies have shown that RS is a linear molecule of α-1,4-Dglucan, essentially derived from the retrograded amylose fraction, and has a relatively low molecular weight (1.2 × 10
5
Da) (Tharanathan 2002). RS has a small
particle size, white appearance and bland flavor. RS also has a low water-holding
capacity. It has desirable physicochemical properties such as swelling, viscosity
increase, gel formation, and water-binding capacity, making it useful in a variety of
foods (Fausto et al. 1997). RS is an extremely broad and diverse range of materials
and a number of different types exist (RS1–RS4) (Nugent 2005). The early classification involved only three forms of starch (Englyst and Cummings 1987; Englyst
et al. 1992): RS 1—physically inaccessible starch; RS 2—starch of raw (nongelatinised) granules of some plant species; RS 3—retrograded starch. In successive
years, those forms were supplemented with another one (Eerlingen and Delcour
1995; Haralampu 2000), namely—RS 4—chemically or physically modified starch.
Presently, all the four types are categorized according to their physicochemical
characteristics (Nugent 2005). RS1 type of starches are resistant to GI tract conditions due to physical inaccessibility offered by seed coats and outer walls of partly
processed grains and dense starchy foods making it stable to almost all cooking
operations (Sajilata et al. 2006). RS2 represents that fraction of starch that is packed
tightly inside the starch granule in such a way rendering it difficult for enzymes to
G. Akhtar et al.