| Resistant starch (RS) is that the starch and the products of starch degradation cannot be absorbed in the small intestine of healthy individuals. Generally, it is subdivided into four fractions: physically trapped starch (RS1), resistant starch granules (RS2), retrograded starch (RS3), chemically modified starch (RS4). RS performs better than dietary fiber in physiological function, playing a key role in protecting gut function and reducing glycemic concentration after meal. In our research, the morphological and physicochemical properties of common corn starch granule and resistant starch granule were systemically studied using Rapid Visco Analyzer (RVA), Farinograph, Mixograph, TA-plus, Laser Particle Analyzer, Differential Scanning Calorimeter (DSC) and Fourier Transform Infrared Spectrometer (FT-IR). And the influences of resistant starch on pasting properties of wheat flour and rheological properties of dough with different gluten strengh were investigated, so did effects on sensory and texture characteristics of staple food in northern China. These results will provide some theoretical basis for resistant starch widely using in food industry.The major results were as follows.1. Study on physicochemical properties of resistant starch.RS2 was small particles with more irregular sphere and small amount cylinder, while RS3 was large particles with sponge-like structure. The mean diameters of RS2 and RS3 were 12.1μm and 44.0μm, respectively. These two kinds of RS were more different in particle size and shape, which could cause different mechanism of resistance. Pasting curves for RS3 and RS2 were almost straight lines and viscosities approximately were zero. These results suggested that resistant starch couldn't be swelling, collapsing, escaping and polymerizing under the experimental conditions and had not pasting properties of common starch. Meanwhile, DSC spectra suggested that RS could remain unchanged under most food processing conditions. UV-VIS spectra and Infrared spectra showed that the resistant starch didn't form new groups, which reflected that RS was physically modified starch to some extent.2. Effect of resistant starch on pasting and gel propertiesEffects of RS3 on strong, intermediate and weak gluten wheat (SGW, IGW and WGW) flours had the same tendency, so did those of RS2. But their effects'degree appeared different. The peak, trough and final viscosities of RS3-wheat flour blends were higher than those of the corresponding RS2-wheat flour blends. The peak, trough, breakdown, final, and setback viscosities of RS-wheat blends decreased with increasing of resistant starches in the blends, because the RVA pasting properties of RS-wheat blends were attributed to wheat flours starch, not resistant starches which didn't swell and gelatinize under the condition of experiment. The viscosity of blend is the sum of viscosity of two kinds of materials, and correlates with the viscosity of each material and the proportion of two materials. Additionally, the amylopectin in the blends plays a main role at early stage in the RVA pasting curve and the amylose exerts a significant effect at middle stage. The hardness, adhesiveness and gumminess were significantly decreased with an increase of RS content in blends, but had little effect on cohesiveness and springiness.3. Effect of resistant starch on wheat dough rheological propertiesThe farinograph, mixograph and extensograph characteristics showed a similar changing trend when adding resistant starch to different kinds of wheat flour. The water absorption of RS-wheat flour blends significantly increased (P<0.05) and the dough development time, dough stability, dough breakdown time, farinograph quality number, peak height, peak height at 8 min, maximum resistance, extensibility and extension area decreased with an increase of resistant starch contents in blends. The addition of RS deteriorated the processing quality of RS-SGW and RS-IGW flour blends, but had little influence on RS-WGW flour blends. The influential tendencies of RS3 on extension resistance of SGW, IGW, and WGW flour blends were consistent with those of RS2. The extension area and R/E value showed that RS-IGW flour blends were more suitable for producing steamed breads and noodles. Meanwhile, RS-WGW flour blends were more suitable for producing biscuits.4. Effect of resistant starch on northern style Chinese steamed bread processing qualitiesThe hardness and chewiness of three kinds of steamed bread with different gluten strength increased significantly and the springiness, cohesiveness and resilience decreased significantly when the RS3 proportion in the blends increased. The hardness and chewiness of 10% RS3-SGW and 5% RS3-IGW steamed bread were significantly lower than that of WGW steamed bread. They had acceptable taste and flavor. The addition of RS3 deteriorated the processing quality of wheat flour. It was shown as follows: the RS3-wheat flour steamed breads had large hardness, small springiness and low sensory scores, but low addition of the RS3 (5% or so) had little influence on processing quality of steamed bread. The staling of steamed bread mainly occurred within the first 24 hours. All the steamed bread had the same staling trends. The correlation analysis showed that the specific volume, internal structure, elasticity, and stickiness played an important role in steamed bread quality evaluation. So, the processing quality of steamed bread could be predicted by farinograph quality number, peak height of mixograph, and extension area in a stretching experiment.5. Effect of resistant starch on northern style Chinese noodle processing qualitiesWith the increase of RS3 content in blends, the color of fresh white water noodle (WWN), white salted noodle (WSN) and yellow alkaline noodle (YAN) became better and better when placed at ambient temperature for 0-24 hour, while the maximum resistance, extensibility and extension area of fresh WWN, WSN and YAN showed decreasing. There was no significant difference between 5% RS3 noodles and noodles without RS3. With the increase of RS3 content in blends, loss ratio of boiling for dry WWN and WSN was almost invariant. The maximum resistance, extensibility and extension area of dry WWN, WSN and YAN all decreased and kept fluctuately. WWN , 5%RS3WSN and YAN had the best elasticity. The breaking strength of all dry WWN, WSN and YAN with 0%-10% RS3 decreased gradually and the flexibility increased gradually. The breaking strength of 15% RS3 WWN and WSN slightly increased and the flexibility decreased evidently. The breaking strength and the flexibility of 15% RS3 YAN showed smaller than that of others. Significant correlations were shown between the elasticity, smoothness and taste flavor and noodle quality evaluation. Therefore, the processing quality of noodle could be predicted by pasting, mixograph and extensograph parameters.6. Effect of resistant starch on bread processing qualitiesThe hardness and chewiness of 5% RS–SGW bread were similar to that of SGW bread, and the resilience was slightly higher than that of SGW bread. It showed that the quality of 5% RS–SGW bread was equivalent to that of SGW bread. The hardness and chewiness of RS-SGW breads with 10%-15% RS significantly increased, so did that of RS-IGW breads with 5%-15% RS. The loaf volume, elasticity, taste flavor of RS-wheat flour bread became smaller, lower and more hardness than that of control. The crust color became irregularity and appeared spots. All these indicated that the addition of RS deteriorate the quality of bread. The correlation analysis showed that the loaf volume, crust appearance, crust structure, crust color, crumb color, crumb texture, crumb grain, crust elasticity, and taste flavor highly significantly correlated with bread quality evaluation. The processing qualities of RS–wheat flour bread can be predicted by dough development time, peak height and peak viscosity in farinograph, mixograph and pasting testing, respectively.
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