Resistant Starch (RS) possesses unique functional properties and physiological benefits as a food ingredient. It has a lower caloric value (8 kJ/g) and is beneficial to the production of high-quality foods. Unique functional properties of RS involve a fine particle size, bland flavor, and whitish color. In addition, it possesses desirable physicochemical properties such as an increase in viscosity, gel formation, swelling index, and water-holding capacity. RS therefore can be widely utilized in a large variety of food products.
- Introduction to Resistant Starch
- Structure and Thermal Properties of Starch Granules
- 5 types of Resistant Starch (RS)
- Factors that affect the digestibility of starch
- Resistant Starch (RS) Preparation
- Resistant Starch (RS) Detection
- The Health Effects of Resistant Starch (RS)
However, each type of Resistant Starch (RS) has a single profile of physiological and technological functionalities. For example, because of the different stabilities of different sources of RS, the appropriate selection should be considered. In most cases involving high temperature and moisture (e.g., frying and high temperature drying), RS1 and RS2 may be destroyed, but RS3 is resistant or can be formed after processing. In addition, cooling of baked foods at ambient temperatures enhanced RS3 formation.
Cross-linked starches prepared from maize, tapioca, and potato are used for formulations that need a pulpy texture, smoothness, flow ability, low pH storage, and high-temperature storage. Commercial sources of RS2 and RS3, which are natural sources that have a high pasting temperature, excellent extrusion, film forming qualities, and lower water retaining properties than traditional fibers like bran, can form low-bulk, fiber-rich, high-quality products with good appearance and improved texture and mouth feel. Consistent with this possibility, numerous food products have been produced that were enriched in RS, including bread, cakes, muffins, pasta, cheese, battered foods, milk desserts, and even beverages.
Resistant Starch (RS) in Bread Making
Bread has been fortified with conventional DFs such as wheat bran and barley flour, which usually have certain negative attributes like reduced volume, dark color, and poor flavor. These negative attributes prompted the use of Resistant Starch (RS).
One study evaluated the effect of oat fiber, wheat fiber, cellulose, and two commercially available RSs with 23% (Hylon™ VII) and 40% TDF (Novelose 260) characteristics of bread. The results showed that the water absorption capacity of flour added with two kinds of RSs was similar to that of the control, while flours fortified with oat fiber, wheat fiber, and cellulose showed a significantly higher water absorption capacity. The low water absorption capacity of RS consequently had less negative impact on dough rheology and was closest to the control dough. Furthermore, bread fortified with 40% RS showed greater loaf volume and better cell structure when compared with traditional fibers.
In another study, the effect of type 4 resistant wheat starch (RS4) on wheat flour dough and breads was evaluated. Wheat flour was substituted by RS4 at 10%, 20%, and 30% w/w (RS10, RS20, and RS30, respectively). Rheological and thermal behaviors of dough, bread quality, starch digestibility, and bread staling were analyzed. The results showed that all substituted doughs exhibited viscoelastic behavior but lower elastic and viscous moduli. Regarding bread quality, the specific volume and crumb texture were negatively affected in breads made with RS4. However, all samples were technologically acceptable. During storage, crumb hardening was observed in breads without and with RS4, but amylopectin retrogradation was not affected. The in vitro digestibility of bread with RS showed a lower estimated glycemic index, suggesting a healthier profile.
The effects of wheat flour replacement by modified pea starch (PeaP) containing high levels of RS1 on dough rheological properties, bread storage, and bread performance were analyzed. The water absorption of flour significantly increased with increasing PeaP content from 54.6% to 74.6%, which was due to the high waterholding capacity (WHC) of RS. A significant increase of adhesiveness, gumminess, and hardness was also observed in dough samples with 20% and 30% of PeaP added, and addition of 30% PeaP significantly and negatively affected the ability to handle the dough. Furthermore, the hardness and chewiness of the crumb were significantly increased when the PeaP concentration was elevated, while cohesiveness and springiness were only slightly affected with the inclusion of 30% PeaP addition in the formulation. Overall, breads with 20% flour replacement with PeaP were acceptable to consumers.
Resistant Starch (RS) in Baked Foods
Resistant Starch (RS) is incorporated in a wide variety of baked foods, including batter systems, such as cakes, muffins, and brownies.
Firmness and adhesiveness are textural properties that are the most important parameters for cooking quality of baked cereal products. Some application tests of RS showed that it acts as a texture modifier, to impart favorable crispness or tenderness to the crumb.
It is well-known that the quality of cakes and cookies is highly affected by the quality and level of the ingredients. The textural characteristics of these products are mostly imparted by their high fat content. Fat is the principle ingredient that gives flavor, tenderness, palatability, lubricity, and mouthfeel to cookies. There has therefore been great interest in using RS as a fat replacer in bakery products. There have been many studies in this area. A type III enzyme-RS with a melting point of at least 140 °C, which could be used as a low-calorie flour replacement in bakery products, exhibited baking characteristics (cookie spread, golden brown color, pleasant aroma, and surface cracking) comparable to those achieved using conventional wheat flour. Excellent quality sponge cakes were prepared by replacing 30% of the flour with four cycled autoclaved-cooled RS3 cornstarch, cross-linked maize starch (RS4), and annealed and cross-linked RS4 maize starch (ARS4), while for the yellow layer cake, the replacement level was found to be 12.5%.
Resistant Starch (RS) in Cheese
Extensive studies have investigated the feasibility of manufacturing a low fat cheese containing Resistant Starch (RS). RS has been incorporated into cheese, not as an attempt to replace the more expensive casein but rather to increase the health benefits.
Mozzarella cheese normally contains approximately 20–27% fat and is popular as an ingredient in pizza. A study showed that the addition of Novelose240 (RS2) or Novelose330 (RS3) in this cheese reduced up to 50% of the fat content, with accepted functional properties. Hardness linearly increased with increasing RS content, with RS3 being more effective than RS2. Cohesiveness was increased linearly with increasing RS2, but RS3 had no effects on the cohesiveness.
The effects of RS2 content on moisture absorption isotherms, and functional properties of imitation cheese, were studied. Cheese moisture remained constant (58%) when the RS2 content was increased from 8.9% to 18.2%. With increasing RS2 content, the hardness and cohesiveness showed no significant increase except at 12.9%. Moreover, the absorption behavior of the cheese was not affected by increasing the RS2 content. Overall, 18% RS2 had no effect on the cheese texture and overall acceptability.
Resistant Starch (RS) as a Functional Ingredient in Other Foods
The stability of RS3 at high temperatures is greater than the other types of RSs, making RS3 acceptable in fried battered foods. Color is one of the main properties of fried battered foods, and the most desirable color is light golden brown. Replacement of wheat flour by 20% RS3 (Novelose330) caused a significant increase in the golden brown color. The main explanation for the intensified color was Maillard and caramelizing reactions. The hardness and crispness of battered fried product also were significantly increased with a 20% level of replacement. The sensory scores including color, flavor, oiliness, crispness, and overall acceptability scores were higher than five, demonstrating that all batter formulas (10% RS3, 20% RS3, and no-RS3 added) were acceptable to customers.
Dried pasta products fortified with 15% RS were prepared with little or no effect on dough handling and rheology during extrusion cooking. In opaque health beverages, RS may also be substituted for insoluble fibers because they involved a suspension, added opacity, imparted a gritty mouth feel, and masked flavors. In another study, fish oil was microencapsulated in a mixture of sodium caseinate and RS. The study showed that modified resistance with low molecular weight and reduced crystallinity improved the encapsulation efficiency, but not the oxidative stability of the fish oil.
Resistant Maltodextrin in Beverages
Resistant dextrins are produced by heating starch acidified with hydrochloric and citric acids. The formation of new 1→2- and 1→3-glucosidic bonds makes dextrins less susceptible to the activity of digestive enzymes. Resistant dextrins have properties such as high water solubility, low viscosity, transparent solutions, and stability, which make them suitable for use in soft drinks.
It is hoped that resistant dextrins may replace some of the sugars in beverages. This would reduce the caloric content of these beverages and provide a beneficial effect on the intestinal microflora of people consuming beverages enriched with enzyme-resistant dextrins, although sensory analysis should be performed prior to the industrial application of such dextrins.