الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
Resistant starch (RS) is a recently recognized source of fiber and is classified as a fiber component with partial or complete fermentation in the colon, producing various beneficial impacts on health. Resistant starch is widely used as a functional ingredient in foods containing high levels of dietary fibre. Resistant starch has great potential to be used in foods due to its potential physiological benefits and unique functional properties. Foods containing resistant starch have small particle size, white appearance, bland flavour and good handling during processing. In addition, resistant starch showed enhancing product attributes. Bakery products such as bread, muffins, and breakfast cereals; can be prepared by using resistant starch as a source of fibre. The amount of resistant starch used to replace flour depend on the particular starch being used, the application and desired fibre level. The incorporation of resistant starch in baked and pasta products imparts improved textural characteristics and health advantages.
This study evaluated modified corn starch into resistant starch by heat moisture treatment (RS1), autoclave treatment (RS2), microwave treatment (RS3) and citric acid treatment (RS4).
The impact of these treatments on resistant starch content, as well as resistant starch muffins, their physical properties (including volume, specific volume, weight loss, depth of penetration), color indices and organoleptic characteristics were studied.
The obtained results coluld be summarized as follow:
1. Resistant Starch Content of wheat flour; corn starch and three different treatments for resistant starch. Obtained results indicate that resistant starch content increased gradually by physical treatment from 19.18 to 30.97 % which indicate that microwave treatment had the highest resistant starch content compared with wheat flour and corn starch.
2. Micro-Visco-Amylograph of the raw and resistant starch
Treatment with citric acid at 160°C did not show any behavior as it was found inability to absorb water or form viscosity and gel to a negligible degree because a whole breakdown of starch granules and thus the inability to form the gel state, so this treatment was excluded.
Raw corn starch showed a maximum (peak) viscosity of 569 (BU) during heating cycle. All modified starch samples showed lower “maximum” viscosity values ranging between only 1 BU (for citric acid, 160 °C modification) and 106 BU (for microwave treated starch samples, 2.5 min).
The corresponding values of setback viscosities (final viscosity – viscosity after holding at 92 °C) were 719 (BU) for raw corn starch paste and in the range of 34 to 114 (BU) for pastes obtained from modified starch samples.
3. X-ray diffraction measured for the raw and resistant starch
X-ray analysis was demonstrated to study the impact of the different treatments on the christalinity degree of the tested starch samples. Raw corn starch granules showed an A-type starch, which is characteristic for cereal starches. The moist heat treatment and autoclaving heating of corn starch showed no different in the cristallinity ratio (RC) than that of raw corn starch, both modified starch samples showed the appearance of a new cristal peak, which was not found in the x-ray pattern of raw corn starch a result of release in some amylose molecules during heating of starch, led to a never decrease in peaks intensity and the total area of the cristalls, the amorphus area was increased. On other side, microwave treatment led to increase in the intensity of the new peak which is a sign for the more release of amylose, forming complex with starch lipids and producing A+V types of starch cristalls. Cristalls area under the XRD-diagram was increased by microwaves treatment and the cristallinity ratio (RC) reached 33.26% and 35.50%, respectively for the 2.5 and 5 minutes microwave treatments. Treatment of starch with citric acid at 130 ºC did not reamarkabely changed the christallinity nature of corn starch samples. However, increasing the temperature of citric acid treatment to 160 ºC, led to a drastic increases in the amylose-lipid complex.
4. Fourier transforms infrared (FTIR) Spectroscopy of the raw and resistant starch
Infrared spectroscopy was used to study alters in the functional groups present in native and modified corn starch samples. Modification of corn starch induces changes in wave numbers, which caused shifts in bands but did not in removal or reduce in the intensity of functional groups. Modified starch have higher degree of order. On other side the dgree of double helix (DD) of the microwave heated and citric acid treated starch were lower than that of raw corn starch, may be because of partial gelatinization induced by there treatments.
5. Physical characteristics of muffins
Physical attribuites of muffins made from origin and modified corn starches by different methods showed that the measurements of softness (penetrometer) indicated that the microwave resistant starch (RS) had a higher remarkable impact on the tenderness of the produced muffins then corn starch, control and autoclave modified starch incorporated muffin samples. Meanwhile, the heat moisture (RS1) recorded lowest tenderness than the other physical treatment.
Also, results of volume value of muffin made from all types of modified starch were decreased a little when compared by that made from control and corn starch. On other side, muffins with autoclave modified starch were recorded highest weight loss value compared to others muffin sample. However, lowest values of specific volume were observed in muffin made from microwave and autoclave treated starch.
6. Color parameters of muffins
Analysis of muffins for color parameters like; (L) lightness, (a) redness and (b) yellowness as well as chroma and total intensity characteristics indicated that the whiter muffin samples were recorded for containing RS3 modified starch comparison with other samples. While, muffins with RS2 showed significantly higher (a) values than all the other muffins, which revealed its higher red color component. On the other hand, control and RS3 muffin samples showed the highest value of parameter (b), compared to other muffin. Meanwhile, muffins with RS3 recorded significantly higher chroma and intensity value.
7. Sensory evaluation of muffins
Sensory acceptance scores for the appearance, texture, flavor and overall acceptance of the control muffin and the muffins with the different modified method of RS showed that all muffin treatments did not differ significantly in appearance, texture and flavor. On the other hand, Overall acceptability also showed the muffins containing autoclaved resistant starch significantly the lowest overall acceptability in comparison to the other muffin treatments.
Based on the abovementioned results achevment, it could be understand that the resistant starch content increased by modified method especially microwave. Also, the addition of resistant starch in muffins produced a softer texture except those prepared from heat moisture treated starch, Results of physical characteristics, color parameters and sensory evaluation of muffin samples made from corn starch modified by heat moisture, autoclave and microwave methods indicated that, resistant starches are suitable as a supplemented materials for producing and enhancing bakery products like muffins.