Cooked Starch Research Articles

Influence of dietary fiber on macrostructure and processing traits of extruded dog foods

Fiber is currently used in dog food formulations due to its nutritional properties. However, few studies have evaluated the influence of fiber on the extrusion traits and kibble formation. The present study evaluated the effect of fiber type and particle size on extrusion processing parameters and kibble macrostructure of dog foods. In treatment 1, guava fiber was added to a control formula (CO) at different inclusion levels: 3% (GF3), 6% (GF6), and 12% (GF12). In treatment 2, two fiber types (sugarcane and wheat bran) and two fiber particle sizes were compared to a control (CO) product. Foods were manufactured using a single screw extruder. Each food was processed on two separate days and samples were collected four times per run, for a total of eight replications per diet. The processing conditions were not changed for any treatment. Data were analyzed via analysis of variance, and compared by polynomial contrasts for treatment 1, and by defined orthogonal contrasts for treatment 2 (P<0.05). Guava fiber inclusion resulted in a linear increase in temperature, pressure, and specific mechanical energy (SME) input (P<0.001) during extrusion, whereas starch cooking (assessed by the amyloglucosidase method) and radial expansion decreased linearly (P<0.001). Kibble density and cutting force increased linearly (P<0.001) with guava fiber inclusion. In treatment 2, fiber addition also increased SME (P<0.001) and decreased radial expansion (P=0.008). However the latter was compensated by an increase in longitudinal expansion in the case of sugarcane fiber, resulting in no change in kibble density. Cutting force was higher (P<0.001) for fiber supplemented foods, similar to treatment 1, but sugarcane fiber had a higher impact on hardness than wheat bran (P<0.001). The finely ground fibers led to higher starch gelatinization (P<0.05) and kibbles with lower piece density (P=0.018). To summarize, insoluble fibers such as guava fiber, sugarcane and wheat bran at high inclusion rate increase the electric energy required to extrude, may reduce starch cooking and result in the production of less expanded, denser and harder kibbles. However, kibble characteristics are also significant impacted by fiber type and particle size.

Effects of Cooked Starches and Sucrose or their Combination on Salivary ?-Amylase Activity and Oral pH

Effects of Cooked Starches and Sucrose or their Combination on Salivary ?-Amylase Activity and Oral pH

Modeling of cooked starch digestion process using recombinant human pancreatic α-amylase and maltase-glucoamylase for in vitro evaluation of α-glucosidase inhibitors

In human, digestion of cooked starch mainly involves breaking down of α-amylase to α-limit dextrins and small linear malto-oligosaccharides, which are in turn hydrolyzed to glucose by the gut mucosal maltase-glucoamylase (MGAM). Human pancreatic α-amylase (HPA), amino- and carboxyl-terminal portions of MGAM (ntMGAM and ctMGAM) catalyze the hydrolysis of α-d-(1,4) glycosidic linkages in starch, playing a crucial role in the production of glucose in the human lumen. Accordingly, these enzymes are effective drug targets for the treatments of type 2 diabetes and obesity. In this study, a Plackett–Burman based statistical screening procedure was adopted to determine the most critical factors affecting cooked starch digestion by the combination of HPA, ctMGAM and ntMGAM. Six factors were tested and experimental results showed that pH and temperature were the major influencing factors, with optimal pH and temperature at 6.0 and 50 °C, respectively. Surprisingly, ntMGAM had no significant contribution to the glucose production from starch digestion compared to the HPA and ctMGAM. The optimal proportion of HPA and ctMGAM in a starch digestion system was further determined by response surface methodology. Results showed a maximum starch digestion (88.05%) within 0.5 h when used HPA:ctMGAM=1:9 (U). The inhibitory effects of various inhibitors on the cooked starch digestion by HPA1/ctMGAM9 were evaluated by determining their half maximal inhibitory concentration (IC50) values. Acarviostatin II03 showed the highest inhibitory activity, with 67 times higher potency than acarbose. Moreover, acarviostatin II03 could significantly depress postprandial blood glucose levels in mice, better than that by acarbose. These findings suggest that our in vitro enzymatic system can simulate in vivo starch digestion process, and thus can be used to screen and evaluate α-glucosidase inhibitors.

Diet and the microbial aetiology of dental caries: new paradigms

To compare the effect of 40 seconds versus 2 minutes brushing on saliva and dental biofilm fluid fluoride in children ages 4-5 years over 1 hour. This was a single-blind, cross-over, randomised, two-period clinical study in healthy children. Three days before the start of each treatment subjects received a thorough brushing and then refrained from all oral hygiene procedures. At treatment visits, after collecting baseline biofilm and saliva samples, staff brushed the occlusal surfaces of the subject's posterior teeth with a pea-sized amount (0.25 g) of NaF/silica toothpaste for the randomised time. Samples were taken at 5 minutes, 15 minutes, 30 minutes and 60 minutes after brushing and analysed for fluoride using a microanalytical methodology. There was a minimum 4-day washout period between treatments. Log changes from baseline biofilm fluid and saliva fluoride were statistically significant (P < 0.05) for both brushing times at all post-brushing time-points [except 60 minutes saliva where P = 0.06 (t-test)]. Statistically significantly greater ln-AUC (area under the curve) was found for biofilm fluid and salivary fluoride after brushing for 2 minutes compared with brushing for 40 seconds over the 1-hour test period. There was a statistically significantly higher concentration of fluoride in the log change from baseline saliva levels after 5, 15, 30 and 60 minutes for the 2-minute brushing time compared with 40 seconds brushing time. There was no statistically significant difference in concentration of log change from baseline fluoride levels in biofilm fluid at each individual time-point (5, 15, 30 and 60 minutes) for the 2-minute brushing time compared with the 40-second brushing time, but significant differences were observed for 15, 30 and 60 minutes in favour of 2-minute brushing time when log biofilm fluid value was analysed. The findings provide further evidence for the benefits of increased duration of brushing with respect to fluoride delivery.

Mechanism of Hydrolysis of Native and Cooked Starches from Different Botanical Sources in the Presence of Tea Extracts

A series of experiments were conducted to highlight the mechanism of inhibition of hydrolysis and differences in hydrolysis among starches from different sources in the presence of green or black tea extract. The first experiment showed that black tea extract was more effective at reducing final viscosity for all starches. The second experiment showed that black tea was more effective at inhibiting starch hydrolysis compared to green tea when starch, tea extract, and pancreatin were added at the beginning of pasting. The third experiment, when starches were pretreated with tea extracts, showed that both treatments reduced starch hydrolysis. Analysis of supernatant free phenolic content and of soluble dextrins showed that amyloglucosidase activity was affected, with exceptions for potato starch. These observations suggest that starch hydrolysis is affected by interactions and also by the impact on specific enzymes based on starch structure.

Effects of Cooking Temperatures and Starch Source on the Gelatinization and Thickening Power of Roux

Roux made from three wheat flours and cornstarch and cooked to six different temperatures were tested for gelatinization onset temperatures and thickening power. All roux showed an increase in thickening power on moderate heating. Cooking to higher temperatures greatly reduced thickening power. Bread flour and all-purpose flour showed increasing gelatinization onset temperatures on heating, whereas pastry flour and cornstarch showed the opposite trend. Only roux made with wheat flours developed color during cooking. These results suggest that the browning during roux cooking is due to Maillard reactions and that caramelization is only a minor contributor to color change.

Impact of γ-irradiation, CIPC treatment, and storage conditions on physicochemical and nutritional properties of potato starches

Abstract In the present study, three potato varieties were treated with chlorpropham (CIPC, 35 ppm), γ-irradiated (0.1 kGy) and stored for up to 5 months at 8 °C, and the physicochemical properties and in vitro starch digestibility of native and cooked starches were investigated. Sprouting was found to be satisfactorily suppressed by γ-irradiation and CIPC treatment. However, irradiation increased total free glucose content in two potato varieties, and decreased the thermal transition and pasting temperature of starch. The crystallinity of starch in irradiated potatoes decreased significantly ( p ⩽ 0.05) which may explain its decreased resistant starch content. Sprout inhibiting treatments and storage had no effect on in vitro starch digestibility in cooked starches, but cooling cooked starch significantly ( p ⩽ 0.05) increased its resistant starch content.

Digestion profiles and some physicochemical properties of native and modified borlotti bean, chickpea and white kidney bean starches

Native starches isolated from borlotti bean ( Phaseolus vulgaris L.), chickpea ( Cicer ariteninum L.), and white kidney bean ( Phaseolus vulgaris L.) was modified by pyrodextrinization (PD), cross-linking with sodium trimetaphosphate (CL), heat–moisture treatment (HMT), and gelatinization–retrogradation (GR) process. The effects of these modifications on the nutritionally important starch fractions, namely rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS), were studied in both uncooked and cooked starches. Solubility, swelling power and gelatinization parameters of the native and modified starches were also studied. PD, CL, and HMT reduced the swelling power of all three legume starches. Significant increases in solubility were observed after PD and CL, where GR decreased the solubility of all starches. CL and HMT shifted the onset temperature of gelatinization (T o) to a higher temperature and tended to decrease the gelatinization enthalpies (ΔH). PD and GR starches has the largest proportion of RDS (39–69%) among uncooked starches where the RDS percentage of uncooked native, CL and HMT starches were only between 2–7%. Compared with native starches, all the modifications applied tended to decrease the RDS percentage of cooked starches. The highest decrease in RDS was determined after GR treatment for all the legume starches studied. The total SDS + RS, the two starch fractions that have nutritional benefits, content of GR and HMT starches were notably higher than the CL and PD starches.

Physicochemical and Rheological Properties of Rice Starch Cooking and Eating Qualities of White Rice (Part 1)

Physicochemical and Rheological Properties of Rice Starch Cooking and Eating Qualities of White Rice (Part 1)

Effects of α-Amylase and Its Inhibitors on Acid Production from Cooked Starch by Oral Streptococci

This study evaluated acid production from cooked starch by Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguinis and Streptococcus mitis, and the effects of α-amylase inhibitors (maltotriitol and acarbose) and xylitol on acid production. Streptococcal cell suspensions were anaerobically incubated with various carbohydrates that included cooked potato starch in the presence or absence of α-amylase. Subsequently, the fall in pH and the acid production rate at pH 7.0 were measured. In addition, the effects of adding α-amylase inhibitors and xylitol to the reaction mixture were evaluated. In the absence of α-amylase, both the fall in pH and the acid production rate from cooked starch were small. On the other hand, in the presence of α-amylase, the pH fell to 3.9–4.4 and the acid production rate was 0.61–0.92 μmol per optical density unit per min. These values were comparable to those for maltose. When using cooked starch, the fall in pH by S. sanguinis and S. mitis was similar to that by S. mutans and S. sobrinus. For all streptococci, α-amylase inhibitors caused a decrease in acid production from cooked starch, although xylitol only decreased acid production by S. mutans and S. sobrinus. These results suggest that cooked starch is potentially acidogenic in the presence of α-amylase, which occurs in the oral cavity. In terms of the acidogenic potential of cooked starch, S. sanguinis and S. mitis were comparable to S. mutans and S. sobrinus. α-Amylase inhibitors and xylitol might moderate this activity.

Effect of Acetylation on Some Properties of Corn and Potato Starches

AbstractCorn starch and starches separated from different potato cultivars were acetylated to evaluate the effect of plant source on the physicochemical, morphological, thermal, rheological, textural and retrogradation properties of the starches. Corn starch showed a lower degree of acetylation than potato starches under similar experimental conditions. The degree of acetylation for different potato starches also differed significantly. Morphological examination revealed that the granules of acetylated Kufri Chandermukhi and Kufri Sindhuri starches tended to appear as fused and less smooth than native starch granules. Acetylation of corn and potato starches decreased the transition temperatures and enthalpy of gelatinization and increased swelling power and light transmittance. However, the change in these was greater in the potato starches with higher percentage of small sized granules. Acetylated starches showed higher peak G', G'' and lower tan δ than their counterpart native starches during heating. Among the starches from different cultivars, the change in the rheological parameters after acetylation differed to a significant extent. The retrogradation was observed to be negligible in the acetylated cooked starch pastes. Results implied that the change in functional properties of starches with acetylation depends on source and granule morphology of native starch.

POST-EXTRUSION STEAMING OF STARCH ACETATE FOAMS

Post-extrusion steaming was applied to extruded foam blends of starch acetate and cellulose or polylactic acid(PLA). Extrudates were obtained by twin-screw extrusion at 160.C barrel temperature and 225 rpm screw speed for starchacetate -cellulose blends and 150 rpm screw speed for starch acetate-PLA blends. Extrudates were steamed at atmosphericpressure for six different steaming times and time intervals (steamed once for 1, 2, and 4 min and steamed twice for 1, 2, and4 min with 1 min between cycles.) One sample was steamed at 960.3 kPa. Extrudates without post-extrusion steaming wereused for comparison. Radial expansion ratio, unit and bulk densities, unit and bulk spring indices, and thermal conductivityof the steamed and unsteamed samples were measured. Scanning electron micrographs were taken to observe foam cellstructures. The highest radial expansion ratio of starch acetate-cellulose extrudates was obtained after steaming twice for2 min with a 1 min interval between cycles. Thermal conductivity of the foams decreased slightly as the steaming time wasincreased. Functional properties of the post-extrusion steamed starch acetate foams were strongly dependent on the formationof inter-molecular linkages between cooked starch acetate and melted cellulose or PLA.

Morphological, thermal, rheological and noodle‐making properties of potato and corn starch

AbstractA comparison between the morphological, thermal, rheological and noodle‐making properties of corn starch and potato starches separated from five different potato cultivars was made. The granule size and shape of all starches differed significantly. Potato starch granules were comparatively larger than corn starch granules, while the transition temperatures were found to be higher for corn starch. Consistency coefficients and flow behaviour indices measured by back extrusion were higher for potato starches than for corn starch. Stickiness of cooked starch pastes was observed to depend upon their consistency coefficient. The gels made from all potato starches showed higher gel strength than those from corn starch. The gel strength of starches from both corn and potato increased during refrigerated storage. The amylose content, swelling power, solubility and light transmittance values of potato starches were significantly higher than those of corn starch. Noodles made from potato starches had higher cooked weight and cooking loss than corn starch noodles. Texture profile analysis revealed that potato starch noodles also had higher hardness and cohesiveness than corn starch noodles. Hardness of cooked noodles from all starches increased and cohesiveness decreased during storage. Noodles made from starches of higher viscosity exhibited higher hardness and cohesiveness. Textural differences among cooked starch noodles appeared to be associated with morphological, thermal and rheological properties of corn starch and potato starches.© 2002 Society of Chemical Industry

An Integrated Microstructural, Sensory and Instrumental Approach to Describe Potato Texture

A new method was developed to objectively measure a range of microstructural features in thin sections of raw and cooked potatoes using light microscopy and semi-automatic digital image analysis. Scanning electron microscopy was employed for qualitative visualization of the texture showing the degree of cell adhesion and cell wall softening. Sensory texture analysis and uniaxial compression tests were used to determine the textural properties of cooked potato samples. Six conventionally and two organically grown potato cultivars were used in the study. Eight image features grouped the potato cultivars with respect to three different structural qualities by principal component analysis. The most important structural differences between potatoes is characterized as a contrast between potatoes having a low volume fraction of cell walls (large cells), a small number of cells and starch grains, and large numbers of elongated cells. Another type of variation in the structural data grouped the potato cultivars with respect to volume fraction of starch grains, volume fraction of gelatinized starch, and formfactor of cells. The volume fraction of raw and cooked starch and the formfactor of cells were significantly lowered during storage. Image features were correlated with sensory and textural properties using multivariate data analysis (Partial Least Square Regression). Volume fraction of raw starch, volume fraction of gelatinized starch, and dry matter content were found to be highly correlated with sensory geometrical qualities. Mechanical sensory properties were found to be more correlated with a uniaxial compression measure (stress at fracture) than was the image data.

Water content measurement of thin sheet starch products using a conductance technique

An electrical conductance technique for water content measurements of drum-drying and extrusion cooking starch products is described in this paper. It is based on the conductance measurement of a thin sheet of material between two electrically isolated metallic plates, acting as electrodes. Water content measurements are calibrated against the conventional loss-in-weight method. Once calibrated the conductance technique yields satisfactory accuracy, repeatability and stability compared to the loss-in-weight method. Yet, it offers the distinct advantage of a major reduction in measurement time (less than a minute). The latter is of critical importance, as clearly demonstrated by moisture absorption/desorption experiments. The method is easy to use and calibrate, readily installed and can be implemented at relatively low cost. The conductometric technique employed in this work, enabled rapid and reliable water content measurements of maize starch sheets (thickness of 0.085, 0.5 and 1 mm) ranging from around 0% to 20%.

Starch Cooking with Limited Water as Affected by Zein and Guar Gum

ABSTRACTDSC (Differential Scanning Calorimetry) peak temperature of starch was decreased by adding zein, but was increased by adding guar gum. Adding zein increased the initial rate of starch cooking, but adding guar gum decreased it. Kinetic studies were carried out at 115, 125, and 135°C. At25°C, zein absorbed less water than waxy corn starch, especially at water activities &gt;0.6 where guar gum absorbed more water than starch. The strong binding of water by guar gum increased DSC‐peak‐temperature and decreased the initial rate of starch cooking. The relatively weak binding of water by zein decreased DSC peak temperature and increased the initial rate of starch cooking. Although water sorption data at cooking temperatures are difficult to measure, the kinetic data at these temperatures and DSC data could be used to supplement the sorption data.

Modeling Shearing Resistance of Powdery Starch for Simulation Studies of Extrusion Cooking Processes

Modeling extrusion cooking of starch requires the use of appropriate intrinsic kinetic equations. Knowledge of shear stress profile in a particulate system such as that in the transition zone of an extruder is crucial for calculation of degrees of conversion (gelatinization and melting) of starch. Shearing resistance of moistened powder starch as affected by temperature, normal pressure, effective shear rate, moisture content, and degree of starch conversion was studied in a model system. A modified vane shear testing device was used for experimental measurement of each individual effect. Within the experimental ranges studied (temperature 30 to 80°C, moisture content 16 to 35 %. effective shear rate 0 to 550 s -1 , starch conversion 0 to 0.36 (36%), and normal pressure 0 to 83 kPa) parameter values in each functionality were evaluated. A single mathematical model useful for calculating shear stress was obtained by combining these effects in a single relationship. A good correlation was shown when the calculated shear stress was plotted against the experimentally measured. The methodologies developed here are useful for the studies of powdery food materials. The potential application of this correlation to the simulation of extrusion processes was discussed.

Determination of Water Separation from Cooked Starch and Flour Pastes after Refrigeration and Freeze‐thaw

ABSTRACTA procedure for determination of net syneresis in starch and flour materials was developed based on free water in freshly cooked pastes, syneresis water expelled during cold storage and absorbed water in the contracted gel. Free water values decreased from 50% to &lt;5%, as starch concentrations increased from 4 to 10%, indicating the need for correction of expelled+absorbed water values from free water for calculating net syneresis. Normal cereal, root and dicotyledonous seed starches exhibited a broad range of expelled water values during refrigeration, but gave high absorbed water values during freeze‐thaw cycles. Waxy starches had low net syneresis during refrigeration and, except waxy corn, during freeze‐thaw. For comprehensive evaluation, two refrigeration and two freeze‐thaw cycles are recommended.

Numerical simulation of the extrusion process for food materials in a single-screw extruder

A numerical study of extrusion cooking of starch based materials in a single-screw extruder is carried out. The low moisture levels and high temperatures typically encountered in practical circumstances are considered. The starch conversion process is studied in the rheological region of the extruder which is often the last few turns of the screw, where the material is treated as a non-Newtonian fluid. A numerical method based on finite-difference approximation is employed to solve the governing non-linear equations for momentum, energy and mass conservation for a non-Newtonian fluid undergoing physicochemical changes. The initial conditions for the problem are taken from experimental observations. The screw configuration and the operating parameters, such as barrel temperature, screw speed and throughput, are varied to study their influence on the conversion of starch. It is found that 28% conversion is obtained due to viscous dissipation alone, whereas 61% conversion occurs by raising the barrel temperature by about 25 °C above the inlet. It is also observed that, at any screw speed, a smaller flow rate caused by a smaller die diameter leads to a higher degree of conversion. Furthermore, it is found that the compression ratio of the screw has a significant influence on pressure rise, bulk temperature and average residence time. As the compression ratio increases the temperature increases but the residence time decreases. The former effect increases the degree of conversion where as the latter decreases the degree of conversion. Therefore there exists a compression ratio at which a minimum degree of conversion at the die is obtained.

Surface Energy of Extruded and Jet Cooked Starch

AbstractContact angles of water and other liquids were measured on films and extruded ribbons of normal, high amylose and waxy cornstarch using a Chan dynamic contact angle analyzer. The contact angles were then used to calculate the critical surface energy of the starch via a Zisman plot. Attempts were also made to use the contact angles to calculate the surface energy of starch via the harmonic‐mean method. No differences were found for the critical surface energy due to starch type. Using a composite of all contact angles for the three different starches, an average critical surface energy of 40 dynes/cm was calculated. This value was close to the literature value of 39 dynes/cm found for starch. The surface energy of starch, calculated from the harmonic‐mean method, was more variable and ranged from 35‐42 dynes/cm. The harmonic‐mean method not only calculates the surface energy, but it also estimates the polar and non‐polar components of surface energy. The estimate calculated for the polar portion for the surface energy of starch was too low for a polar solid like starch. Values for the polar component range from 0.3 to 10 dynes/cm. A theoretical argument is made for the surface energy of starch being greater than the 39 dynes/cm now reported in the literature.