Bernhard van Lengerich

Effect of Extrusion Cooking on Molecular Parameters of Corn Starch

By using a systems analytical model (SAM) and a fuzzy logic control software (fuzzy CIM) extrusion experiments were designed, that enabled a differentiation of the influence of the thermal energy input, expressed by the product temperature (PT), and the influence of the specific mechanical energy input (SME) on the molecular structure of extruded starch. The chromatographic examination of the molecular changes in the starch clearly revealed the influence of the extrusion cooking conditions on molecular degradation. The molecular size of extruded starch, expressed as the weight average of the molecular weight (Mw), decreased exponentially when SME increased. In the range of 110—180 °C, PT had no significant influence on Mw so that the observed reduction of Mw was primarily dependent on the increase in SME. By contrast, the polydispersity depended both on PT and SME. The influence of PT on the polydispersity was of minor significance up to 160 °C, increasing more steeply at higher temperatures. PT increase above 180 °C resulted in increasing reducing power of the extruded starch, whereas SME had almost no effect on reducing power. Only at a PT of more than 180 °C small amounts of short chain molecules with a degree of polymerisation (DP) smaller than 6 could be determined.

A salty-congruent odor enhances saltiness: Functional magnetic resonance imaging study

Excessive intake of dietary salt (sodium chloride) may increase the risk of chronic diseases. Accordingly, various strategies to reduce salt intake have been conducted. This study aimed to investigate whether a salty‐congruent odor can enhance saltiness on the basis of psychophysical (Experiment 1) and neuroanatomical levels (Experiment 2). In Experiment 1, after receiving one of six stimulus conditions: three odor conditions (odorless air, congruent, or incongruent odor) by two concentrations (low or high) of either salty or sweet taste solution, participants were asked to rate taste intensity and pleasantness. In Experiment 2, participants received the same stimuli during the functional magnetic resonance imaging scan. In Experiment 1, compared with an incongruent odor and/or odorless air, a congruent odor enhanced not only taste intensity but also either pleasantness of sweetness or unpleasantness of saltiness. In Experiment 2, a salty‐congruent combination of odor and taste produced significantly higher neuronal activations in brain regions associated with odor–taste integration (e.g., insula, frontal operculum, anterior cingulate cortex, and orbitofrontal cortex) than an incongruent combination and/or odorless air with taste solution. In addition, the congruent odor‐induced saltiness enhancement was more pronounced in the low‐concentrated tastant than in the high‐concentrated one. In conclusion, this study demonstrates the congruent odor‐induced saltiness enhancement on the basis of psychophysical and neuroanatomical results. These findings support an alternative strategy to reduce excessive salt intake by adding salty‐congruent aroma to sodium reduced food. However, there are open questions regarding the salty‐congruent odor‐induced taste unpleasantness. Hum Brain Mapp, 2013.

Glass transition of extruded wheat, corn and rice starch

Commercial wheat, corn and rice starch were extrusion cooked under a specific mechanical energy input (SME) ranging from 81 to 365 Wh/kg (288 to 1314 kJ/kg). Extrusion cooking at low and high SME resulted in products having significant differences in molecular weight distribution and having crystalline structures of the V- and E-type, as determined by gel permeation chromatography and X-ray diffraction analysis. Differential scanning calorimetry revealed that the glass transition temperature (T g ) of the extruded starches was independent of the botanical source, the degree of extrusion-induced molecular fragmentation and the formation of the V- and E-type crystalline structures. The obtained master curve, defined by the relationship between water content and T g of the amorphous starch, may be used as a predictive tool in modelling the extrusion process of starch or starch containing blends, especially with regard to the formation of the morphological structure and texture attributes of directly expanded products.

Recommendations for optimization of fortified and blended food aid products from the United States

Fortified blended foods (FBFs) were introduced into the Food for Peace program (also known as US Public Law 480) in the 1960s. Minimal changes have since been made to their formulations. A Food Aid Quality Enhancement Project to assess the nutritional adequacy of FBFs for vulnerable populations was conducted, and the findings indicate that FBFs do not meet the nutritional needs of infants and young children between the ages of 6 and 24 months. Improvements are also needed for FBFs intended for school-aged children and adults. Two separate products would better meet the varying nutritional needs of diverse groups of beneficiaries. Proposed here is a two-step strategy for better addressing the needs of todays food aid beneficiaries: 1) improving FBFs for general distribution to households, schools, and emergency settings, with potential efficiencies gained in manufacturing and formulation to reduce costs; 2) developing new products for infants and young children, which would deliver the nutrient density required for growth and development.

Description of Extrudate Characteristics in Relation to the Shear Stress of Plasticised Starches Determined In-line

The behaviour of wheat, corn and rice starch as well as of mixtures thereof was investigated with the aid of the shear stress of material plasticised under extrusion cooking conditions. The shear stress was determined in a laboratory extruder using an in-line viscometer. The extrusion experiments were performed using a combination of a fractionated factorial design and mixture experiments. It was shown for each starch and mixture of starches that a functional dependency existed between the extrusion process parameters and the shear stress of the plasticised materials. A second relationship was found between the shear stress of the plasticised materials and the product characteristics of the extrudates. With respect to the extrusion cooking of various types of starch, it could thus been demonstrated that it is possible to predict the development of product characteristics by determining the shear stress of plasticised materials in-line. Furthermore, regression analysis showed that the levels of the test ranges for the relationship between the shear stress and the process parameters are dependent on the starch or starch mixtures used. Molecular degradation of the starch polymers of the different types of starch and their mixtures resulted in extrudates with different functional properties. This also applied to extrudates with the same mean molecular weight. Extrudates made of wheat starch had a much higher cold paste viscosity than extruded rice or corn starches. Extrudates made of corn starch and those made of mixtures of rice, corn and wheat starch had a higher cold water solubility and a lower sediment volume than those made of wheat or rice starch.

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.

SME-arrhenius model for WSI of rice flour in a twin-screw extruder

ABSTRACT We have modeled a rice extrusion process focusing specifically on the starch gelatinization and water solubility index (WSI) as a function of extrusion system and process parameters. Using a twin-screw extruder, we examined in detail the effect of screw speed (350–580 rpm), barrel temperature, different screw configurations, and moisture content of rice flour on both extrusion system parameters (product temperature, specific mechanical energy [SME], and residence time distribution [RTD]) and extrudate characteristics (expansion, density, WSI, and water absorption index [WAI]). Changes in WSI were monitored to reveal a relationship between the reaction kinetics during extrusion and WSI. Reaction kinetics models were developed to predict WSI during extrusion. WSI followed a pseudo first-order reaction kinetics model. It became apparent that the rate constant is a function of both temperature and SME. We have developed an adaptation of the kinetic model based on the Arrhenius equation that shows bet...

Empirical Modeling of Die Pressure, Shaft Torque, SME, and Product Temperature of Rice Flour in a Corotating Twin-Screw Extruder

ABSTRACT Empirical models for predicting die pressure, product temperature, shaft torque, and specific mechanical energy (SME) input based on rice flour extrusion using a DNDL-44/28D Buhler twin-screw extruder are presented. The models incorporate the effects of shear rate, barrel temperature, moisture content, flow rate, and screw geometry. The models were tested using rice flour at various screw configurations and extrusion conditions. Die pressure is a function of moisture content, product temperature, and flow rate. By testing the die pressure model, we found that, within the experimental range tested, die pressure was not significantly affected by barrel temperatures and screw configurations. Product temperature and shaft torque are functions of shear rate, moisture content, flow rate, barrel temperature, and screw configuration. Introducing the effect of screw configuration into the models for temperature and shaft torque resulted in an overall improved model performance. Predictions of various mode...

Control of cell morphology of probiotic Lactobacillus acidophilus for enhanced cell stability during industrial processing

The viability of bacteria during industrial processing is an essential quality criterion for bacterial preparations, such as probiotics and starter cultures. Therefore, producing stable microbial cultures during proliferation is of great interest. A strong correlation between the culture medium and cellular morphology was observed for the lactic acid bacterium Lactobacillus acidophilus NCFM, which is commonly used in the dairy industry as a probiotic supplement and as a starter culture. The cell shapes ranged from single short rods to long filamentous rods. The culture medium composition could control this phenomenon of pleomorphism, especially the use of peptone in combination with an adequate heating of the medium during preparation. Furthermore, we observed a correlation between the cell size and stability of the microorganisms during industrial processing steps, such as freeze-drying, extrusion encapsulation and storage following dried preparations. The results revealed that short cells are more stable than long cells during each of the industrially relevant processing steps. As demonstrated for L. acidophilus NCFM, the adaptation of the medium composition and optimized medium preparation offer the possibility to increase the concentration of viable cells during up- and survival rate during down-stream processing.

Empirical Modeling of Mean Residence Time in a Co-Rotating Twin-Screw Extruder with Rice Flour

ABSTRACT Mean residence time of rice flour in a twin-screw extruder was determined using a blue tracer. Variables studied included moisture content, screw speed, barrel temperature, and screw configuration. Mean residence time increased with the increase of the barrel temperature and with the addition of reverse and kneading elements. Mean residence time was significantly related to screw speed, moisture content, die pressure, and screw configuration (P < 0.05). An empirical model was developed to predict mean residence time with the ability to reflect the changes of the barrel temperature and screw configuration. The effects of different extrusion operating conditions including screw speed, moisture content, barrel temperature, and screw geometry on the mean residence time were considered in the model. The validity of the developed model was extensively evaluated and verified using different screw geometries and other processing variables. The mean residence times predicted by the developed model are in ...