Influence of Extrusion Cooking Conditions on the Efficiency of the Cationization and Carboxymethylation of Potato Starch Granules

A systems analytical model for the extrusion of starches and flours was modified to determine the optimal extrusion conditions for the cationization and the carboxymethylation of potato starch and to determine the effect of the extrusion conditions, optimal for the reaction yield (R.E.) and the desired degree of substitution (D.S.), on the rheological properties of the derivatives. In order to improve the describability of the postulated functional relationships between the defined system parameters and the R.E. it was decided to measure the heat flow over the length of the processing part of the extruder in order to enable a more precise measure of the specific thermal energy input (STE). Test run results showed that the STE is highly correlated to the SME. Therefore the initial proposal to substitute the STE for the product temperature in the modified systems analytical model could not be successful. The extension of the working range for these trials to higher SME and mean residence time levels compared to previous studies enabled the production of cationic starch with a maximum R.E.>90% and the production of carboxymethylstarch with a maximum R.E. of about 85%. The modified systems analytical model could not yet be used precisely for the optimization of the R.E. of the derivation of starches. The influence of process parameters and D.S. on rheological properties of the examined derivatives could be described with regression equations.     

Einfluß der Extrusionsparameter auf funktionelle Eigenschaften von Weizenstärke

The Influence of Extrusion Parameters on the Functional Properties of Wheat Starch. The functional properties of native starch can be altered by regulating the technical parameters in the extrusion cooking process. The influence of specific variables on the resultant starch properties can be differentiated by means of system analysis. To make this clear, a model has been put forward which divides individual factors into those which influence the process and those which are influenced by the process, as well as examining their interrelationships. As a result of the experiments, it was possible to use regression analysis to examine the relationships between the various system analysis components. Thus it is possible either to predict the properties of the resultant starch knowing the extrusion and system parameters, or to suggest suitable extrusion conditions in order to obtain a particular starch product.     

AQUEOUS DISPERSION RHEOLOGY OF EXTRUSION COOKED MAIZE

The effects of twin screw extrusion cooking of maize grits at different high moisture contents are described. Starch granules survive in the extrudate at high extrusion moisture or with a low shear screw configuration. The aqueous dispersion rheology of the milled extrudate and its dependence on shear rate and heat treatment is explained in terms of the starch swelling behaviour and solubility. These data resemble that of raw maize most closely for the low shear screw configuration. For the high shear configuration under similar conditions of moisture, temperature and mechanical energy dissipation, starch granules are not seen and the dispersion rheology is markedly different from that of raw maize.     

Chemische und verfahrenstechnische Gesichtspunkte zur Herstellung von kationischer Kartoffelstärke durch Kochextrusion

Chemical und Processing Aspects of the Production of Cationic Starch Using Extrusion Cooking. Cationic potato starches were produced by carrying out the chemical reaction under varying extrusion cooking conditions in order to investigate the influence of the extrusion parameters on the reaction efficiency (R.E.) and the degree of substitution (D.S.) dependent on this. The extrudates were used to develop a suitable analytical method for an accurate determination of the D.S. To achieve the necessary analytical accuracy all nitrogen containing substances not chemically bound to the molecules of the starch must quantitatively be extracted from the cationic starch prior to the determination of its nitrogen content. It could be shown by extraction experiments that the extractability of such substances from ground cationic potato starch extrudates is dependent on the penetration of the solvent through the extrudate particles and the diffusion of the soluble substances in the particles into the solvent. Optimal results for the R.E. were achieved by suspending one part ground cationic potato starch extrudate in ten parts solvent consisting of 80% Ethanol and 20% water (w/w). The suspension had to be kept in a sealed glass vessel for 40min at a temperature of 80°C. Within the experimental range of the extrusion experiments the reaction conditions for the cationization could be kept constant. Besides the formulation of the reactive components the D.S. was influenced by the variation of the extrusion parameters. A. R. E. of 80% was achieved over the investigated range for the D.S. of 0.03 to 0.10.     

Pea starch noodles: Effect of processing variables on characteristics and optimisation of twin-screw extrusion process

The effects of processing variables (moisture content, barrel temperature and screw speed) on the physicochemical, cooking and textural properties of pea starch noodles prepared by twin-screw extrusion were investigated using response surface methodology. Results indicated that increasing dough moisture content increased the b^∗ value (yellowness), expansion ratio, percentage of gelatinised starch, resistant starch content, cooking time, firmness and surface stickiness, but reduced cooking loss. Raising barrel temperature reduced cooking loss and cooked weight, but increased the expansion ratio, percentage of gelatinised starch, resistant starch, firmness and surface stickiness of cooked pea starch noodles. The b^∗ value, expansion ratio, percentage of gelatinised starch, resistant starch, cooking time, firmness and surface stickiness were increased as screw speed was increased, whereas the a^∗ value and cooked weight were reduced. The optimum processing conditions for pea starch noodle-making by twin-screw extrusion was established. Good agreement was noted between experimental values obtained at optimum process conditions and predicted values. Pea starch noodles prepared by twin-screw extrusion exhibited similar brightness in colour and cooking time to, but firmer texture than, commercial mung bean starch noodles.     

Application of an In‐line Viscometer to Determine the Shear Stress of Plasticised Wheat Starch

An in‐line viscometer was designed and constructed to enable determination of the shear stress of plasticised wheat starch during extrusion cooking. The viscometer was installed between the end of the barrel section and the extruder die plate so that the shear stress could be determined for the plasticised material, irrespective of the geometrical shape into which it was subsequently moulded by the extruder die. The extrusion conditions were described in terms of the process parameters, i. e. water content, barrel temperature, screw speed and screw configuration; and of the system parameters, which were the specific mechanical energy input (SME), product temperature (PT) and mean residence time (MRT). The parameters were measured and the results evaluated using statistical methods. Regression equations were used to describe functional relationships between the shear stress and the extrusion conditions on the one hand, and between the shear stress and the product characteristics of the extrudates on the other. The shear stress of plasticised wheat starch determined in‐line can be used to predict the morphological structure (volumetric expansion) and the functional properties (cold paste viscosity and cold water solubility) of extruded, directly expanded starch with a high degree of accuracy. The measurement technique used and the results of the extrusion tests undertaken for this project will therefore enable the shear stress of plasticised material in an extruder to be used as the principle parameter for controlling extruders on‐line.     

Extrusion Process Parameters, Sensory Characteristics, and Structural Properties of a High Moisture Soy Protein Meat Analog

ABSTRACT: Soy protein isolate and wheat starch at 9:1 ratio were extruded at 60%, 65%, and 70% moisture contents and 138, 149 and 160 °C cooking temperatures. The results indicated that moisture content was a more important factor than cooking temperature for both extrusion process parameters and product sensory characteristics. Extrusion at a lower moisture content resulted in a higher product temperature and higher die pressure. The resultant products were tougher, chewier, and more cohesive and had a more layered and fibrous structure. Water absorption capacity increased with both higher extrusion moisture and higher cooking temperature.     

The Extrusion Cooking of Potato Starch Material

The effect of extrusion cooking on the pasting properties of potato starch materials is examined using a Couette rheometer. The dispersion viscosity of aqueous dispersions of potato starch, pregelatinized potato starch and commercial potato granules has been investigated. The effect of extrusion moisture and progress down the extruder on this property has been studied. The dispersion viscosity response is related to the gelatinization and disruption of starch granules. Extrusion at high moisture levels leads to high viscosity dispersions tending to that of gelatinized starch whereas low moisture levels result in lower viscosity dispersions.     

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.     

A multiple-step slit die rheometer for rheological characterization of extruded starch melts

Extrusion cooking is a very important process in the field of cereal and snack manufacturing. The rheological properties of the starch based matrix strongly influence this process. A newly developed online rheometer was mounted on a twin screw extruder in order to measure these properties. It was possible to obtain viscosity of wheat flour and corn grits at typical extrusion cooking conditions over a shear rate range of three decades. Flow curves for varying screw speed and water content at a constant thermomechanical history of the starch were measured. Also the temperature dependence of the apparent viscosities could be determined showing activation energies in the range found for synthetic polymers. Furthermore, additional pressure drops that occur at step changes of the slit height were detected. Thus, it was possible to evaluate visco-elastic properties of extruded starch melts at different extrusion cooking conditions.     

Influence of Extrusion Cooking on In Vitro Digestibility,Physical and Sensory Properties of Brazilian Pine Seeds Flour (Araucaria Angustifolia)

Brazilian pine seeds (pinhão) are gluten‐free products derived from Araucaria angustifolia. The commercialization of these seeds is essentially associated with a low level of industrialization. In this context, extrusion cooking is a potential alternative for preparing extrudates of pinhão as a food product, which can be easily digested and is ready for human consumption. Brazilian pine seeds flour was processed in a single‐screw extruder following a central composite rotatable design. Three factors (independent parameters) were considered: moisture content (14 to 22 g/100 g), screw speed (100 to 250 rpm), and temperature in the 3rd heating zone (120 to 200 °C). The structural characteristics, in vitro digestibility and sensory acceptance were also evaluated. The resistant starch contents is almost reduced to zero after extrusion cooking while the slowly digestible starch content is increased. An increase in moisture positively affected the hardness and the luminosity (L^*), although it negatively affected the volumetric expansion index, crispness, and color parameters (a^*, b^*, and ΔE). The experimental conditions of this study allowed the production of expanded extrudates from Brazilian pine seeds with good expansion, texture properties, and acceptance qualities. Thus, extrusion cooking was found to be a potential method for the industrialization of Brazilian pine seeds as a food product.     

Resistant Starch Derived from Extruded Corn Starch and Guar Gum as Affected by Acid and Surfactants: Structural Characterization

Corn starches with and without guar gum [10% (w/w)] and 2% (w/w) of diacetyl tartaric acid ester of monoglyceride, sodium stearoyl‐2‐lactylate or citric acid, respectively, were extrusion‐cooked in a twin‐screw extruder at 18% moisture, 150 °C and 180 rpm screw speed. The content of resistant starch was determined by sequential enzymatic digestion. The formation of resistant starch in extruded corn starch was strongly affected by the addition of gum and the different food additives. X‐ray diffraction of the extruded starches gave a V diffraction pattern indicating the effect of extrusion cooking and amylose‐lipid complexes. Enzymatic digestion did not affect the V‐structure, which could apparently be attributed to extrusion cooking. Similarly, differential scanning calorimetric thermograms indicated that all isolated resistant starches exhibited endothermic transitions between 71—178 °C signifying a complex formation between amylose and the emulsifiers and possibly the melting of amylose crystallites in the resistant starch. Purification of the isolated resistant starches by size exclusion‐high performance liquid chromatography showed a dependence of molecular weight on the added additives. Results of differential scanning calorimetry and X‐ray diffraction suggest that amylose‐lipid complexes could also be involved in the formation of resistant starch in extruded cornstarch.     

Extrusion of Hulled Barley Affecting β-Glucan and Properties of Extrudates

Grits from eight different hulled barley cultivars were subjected to extrusion cooking on a twin screw extruder, and the effect of extrusion variables (temperature and moisture) on β-glucan and physicochemical properties was evaluated. The highest bulk density was observed for extrudates extruded at 150 °C and 20% moisture (low temperature high moisture, LTHM) while the highest expansion was observed for the extrudates extruded at 150 °C and 15% moisture (low temperature low moisture). Extrusion reduced the lightness (L*) of the extrudates and the highest decrease observed for LTHM extrudates. Increasing the feed moisture decreased water solubility index (WSI) significantly while increasing the extrusion temperature significantly increased WSI. The high temperature high moisture (HTHM) extrudates exhibited the highest water absorption capacity. The total β-glucan content was not affected by extrusion cooking, but a significant increase in soluble β-glucan was observed with the highest in high temperature low moisture extrudates. The ratio of soluble to insoluble β-glucan varied from 0.7 to 1.5 in the control barley, but after extrusion cooking, the ratio was changed from 1.2 to 3.1. The β-glucan extractability increased by up to 8% after extrusion with extrudates from HTHM showing the highest extractability. The extent of starch gelatinization varied from 80% to 100% upon extrusion, and the highest was observed in HTHM extrudates. A significant decrease in the peak and final viscosity of the extrudates at all the extrusion conditions was observed.     

Reduction of ochratoxin A in extruded barley meal

The objective of this work was to determine the effects of extrusion cooking on the stability of ochratoxin A (OTA) in an artificially contaminated hulled barley meal (0.73-mm grain diameter) using a single screw extruder. The extrusion cooking parameters were temperature (140, 160, and 180 degrees C), initial moisture content of barley meal (24, 27 and 30%), and residence time (30, 40, 50, 60, and 70 s). Both unextruded and extruded samples were analyzed for OTA by high-performance liquid chromatography. Extrusion cooking variables significantly affected the stability of OTA (P < 0.05). Greater OTA reductions were achieved at higher residence time (70 s), medium temperature level (160 degrees C), and either high (30%) or low moisture (24%) content of samples. The amount of OTA destroyed during the extrusion process ranged from 17 to 86% depending on the studied parameters. The decrease in the amount of OTA after extrusion cooking followed first-order kinetics, showing that the fastest treatment in OTA reduction was that at 140 degrees C and 24% of moisture content.     

Compounding of Thermoplastic Starch with Twin-screw Extruders

The compounding of thermoplastic starch can be regarded as a combined process consisting of extrusion cooking and plastic compounding. The quality of the product is determined largely by the degree of mechanical shear, temperature and water content. These parameters can be influenced both by the machine system and the various components of a machine. These include infinitely adjustable throttle systems and continuous condensation and evaporation equipment. On account of the fact that the starch pellets are sometimes soluble in water, the type of pelletizing is also very important. A product quality which has been optimized can be reproduced every day by means of automatic systems. Some examples of on-line quality control systems are shown.     

Functional,biochemical and pasting properties of extruded bean (Phaseolus vulgaris) cotyledons

Response surface methodology was used to investigate the effects of extrusion conditions – namely moisture content (12.3–23.7 g 100 g^?1) and temperature (150–178 °C) – on physicochemical, antinutritional compounds, functional and pasting properties of extruded bean cotyledons. Results indicated that extrusion cooking did not change the chemical composition of bean flours, but completely eliminated the activity of the trypsin and α‐amylase inhibitors and haemagglutinins. The extrusion significantly improved starch and protein digestibility, water solubility and absorption of bean cotyledon. In addition, extrusion conditions significantly affected pasting properties, resulting in extrudate flours with different peaks and final viscosity values. From the results obtained in this work, it is possible to design a product with specific physicochemical, functional and nutritional properties using the appropriate moisture and temperature during extrusion.     

十六烷基羧甲基淀粉醚的挤压法制备及其性质的研究

以羧甲基淀粉为原料,溴代十六烷为醚化剂,NaOH为催化剂,利用双螺杆挤压机在干法挤压条件下制备了一种高碳疏水基团的十六烷基羧甲基淀粉醚。探讨了醚化剂用量、螺杆转速、机筒温度、物料水分及碱用量对产品乳化性的影响,利用紫外分光光度计、红外光谱分析仪、粒度仪等对不同取代度(0、0.025 6、0.049 5、0.058 0、0.0701)的十六烷基羧甲基淀粉醚的结构和表面活性、乳液粒径等进行了表征比较。红外光谱图在2 960~2 850 cm~(-1)处产生了吸收峰,-OH的伸缩振动变得弱而平缓,这是因为淀粉中羟基基团进一步被取代所导致,说明溴代十六烷的长碳链已接入淀粉分子;与原淀粉相比,产物的表面张力减小,且随着产物溶液质量分数的增大表面活性越大;随着醚化取代度的增加,乳状液的平均粒度逐渐减小,从粒径分布可以证明羧甲基淀粉疏水化后乳化性明显得以改善;当淀粉接入长碳链疏水基团后,十六烷基羧甲基淀粉醚的水溶性降低。     

Physical and Functional Properties of Arrowroot Starch Extrudates

ABSTRACT:  Arrowroot starch, a commercially underexploited tuber starch but having potential digestive and medicinal properties, has been subjected to extrusion cooking using a single screw food extruder. Different levels of feed moisture (12%, 14%, and 16%) and extrusion temperatures (140, 150, 160, 170, 180, and 190 °C) were used for extrusion. The physical properties—bulk density, true density, porosity, and expansion ratio; functional properties such as water absorption index, water solubility index, oil absorption index, pasting, rheological, and textural properties; and in vitro enzyme digestibility of the extrudates were determined. The expansion ratio of the extrudates ranged from 3.22 to 6.09. The water absorption index (6.52 to 8.85 g gel/g dry sample), water solubility index (15.92% to 41.31%), and oil absorption index (0.50 to 1.70 g/g) were higher for the extrudates in comparison to native starch (1.81 g gel/g dry sample, 1.16% and 0.60 g/g, respectively). The rheological properties, storage modulus, and loss modulus of the gelatinized powdered extrudates were significantly lower ( P < 0.05) and these behaved like solutions rather than a paste or a gel. Hardness and toughness were more for the samples extruded at higher feed moisture and lower extrusion temperature, whereas snap force and energy were higher at lower feed moisture and temperature. There was a significant decrease in the percentage digestibility of arrowroot starch (30.07% after 30 min of incubation with the enzyme) after extrusion (25.27% to 30.56%). Extrusion cooking of arrowroot starch resulted in products with very good expansion, color, and lower digestibility, which can be exploited for its potential use as a snack food.     

挤压参数对酿造酱油原料糊化度的影响

利用挤压技术对酿造酱油的芝麻粕和面粉等原料进行预处理,可以起到淀粉糊化的作用。在单因素试验的基础上,以挤出物 糊化度为考察指标,以挤压温度、螺杆转速、面粉含量、含水量为挤压参数,运用Box-Behnken试验设计对挤压芝麻粕酿造酱油中挤压 参数进行优化。 结果表明,最佳挤压参数为挤压温度90 ℃,螺杆转速200 r/min,面粉含量26%,含水量21%。 在此最优条件下,挤出物 的糊化度为91.23%。     

Twin-screw extrusion of two pea varieties: Effects of temperature and moisture level on antinutritional factors and protein dispersibility

A series of tests was made with two varieties of pea (Pisum satirum L) to measure the effects of extrusion temperature (105–140°C) and moisture level (14-33%) on the level of antinutritional factors (ANF). Twin-screw extrusion cooking of peas showed the dependence of proteinaceous ANF (such as trypsin inhibitors and lectins) on the processing variables used. For the round-seeded pea variety (Finale), the moisture level as well as the temperature proved to be an important variable, although inactivation of trypsin inhibitor activity was complete for all processing conditions investigated. For the wrinkle-seeded pea (var C306), the temperature used during extrusion cooking largely inactivated ANF. The costs of extrusion vary considerably according to the processing conditions and are confined to the desired objectives of extrusion cooking. The objectives, in terms of the inactivation rates for pea ANF, must therefore, be clearly defined and based on threshold levels established from experiments with monogastric animals. Regression models for the inactivation of ANF are given to facilitate the choice of twin-screw extrusion-cooking variables for the upgrading of the nutritional value of pea protein.