Relationship between viscosity and expansion properties of variously extrusion-cooked corn grain components

Normal corn flour and starch were extrusion-cooked at different die L/D ratios (extrusion pressure), screw speeds and moisture contents. Apparent viscosity, shear rate, expansion volume and molecular degradation of starch during or after extrusion-cooking were determined and the interrelationships among these properties were studied. Overall, the apparent viscosity of the extrusion-cooked starch or flour affected expansion more than did the extrusion pressure. The maximum expansion volume of 13.8 for starch was obtained at an apparent viscosity of 3 kPa-s.     

Nanofibre-based bilayer biopolymer films: enhancement of antioxidant activity and potential for food packaging application

This study aimed to enhance the antioxidant property of biopolymer film without the incorporation of external agents. The active bilayer film with improved antioxidant activity has been developed by electrospinning zein, a prolamine of corn as nanofibre (average diameter of 286 nm) on solvent cast chitosan film. Zein nanofibres exhibited a slight increase in antioxidant activity as compared to solvent cast zein film. But, zein nanofibre coating on chitosan films significantly improved its antioxidant activity from 12.41% to 44.17%. The developed bilayer films were evaluated for its ability to prevent browning in minimally processed apple slices and compared with those of chitosan and zein films plasticised with polyethylene glycol. Higher surface to volume ratio and better affinity of zein nanofibres in the bilayer film helped enhance its anti-browning ability. Thus, zein nanofibre-coated chitosan bilayer films can be used as an effective anti-browning packaging material for the packing of minimally processed fruits.     

Computational fluid dynamics (CFD) modeling of an electrical heating oven for bread-baking process

Radiation is the most dominant heat transfer mode in an electrical heating oven. A 3D CFD model for an electric heating baking oven was developed. Three different radiation models namely, discrete transfer radiation model (DTRM), surface to surface (S2S) and discrete ordinates (DO) were employed for the simulation of the electrical baking oven. All models predicted almost similar results, which tallied well with the experimental measurements. During the full heating cycle, the oven set-point temperature was reached after 360 s. Lower temperature zones occurred near oven wall due to lower air flow. Based on preliminary evaluation of applicability, the DO radiation model was selected for bread baking simulation and validated with the experimental measurement of bread temperature. Bread simulation was carried out to study the profiles of temperature and starch gelatinization of crust and crumb of the product. This study indicated the baking process to be complete at 1500 s when the temperature of bread-center reached 100 °C.     

Indane‐based bismaleimide and cloisite 15a nanoclay blends: Kinetics of thermal curing and degradation of particulate nanocomposites

Bismaleimide, 5(6)‐maleimide‐1(4′‐maleimidophenyl)‐1,3,3′‐trimethyl indane (BMII) was prepared, different weight ratios (1, 3, 5, 7, and 9%) of cloisite 15a were blended with BMII ultrasonically and thermally polymerized at 230°C for 6 h. The Fourier transform infrared spectrophotometry (FTIR) studies of the polymerized materials reveal that the clay particles affect only the indane nucleus present in the bismaleimide. Differential scanning calorimetry results reveal that the nanoclay particles affect the enthalpy of curing and the extent of this effect depends on the degree of clay loading. In the case of particulate nanocomposites, irrespective of the amount of clay loading, the endset degradation temperatures of the nanocomposites were found to increase (35–60°C). The change noted in the apparent activation energies (E_a) for curing and degradation with respect to the extent of the reaction (α) is much dependent on the amount of cloisite 15a present in BMII. The TG‐FTIR studies showed the compounds such as CO, CO₂, aromatic amine, and aromatic isocyanates are the major degradation products from polyBMII. Possible degradation mechanism of polyBMII is presented and discussed. The scanning electron microscopy results show that the aggregation of clay particles are noted for higher level loadings (5 and 7%) of cloisite 15a nanoclay particles in BMII. POLYM. COMPOS. 34:1279–1297, 2013. © 2013 Society of Plastics Engineers     

Computational fluid dynamics modeling of bread baking process

A computational fluid dynamic (CFD) model was developed to study the temperature and browning profile of bread. This study differs from previous work of CFD modeling reported in literature in that phase change during evaporation as well as evaporation-condensation mechanism during baking process was incorporated in this model. Simulation results were validated with experimental measurements of bread temperature at three different positions. In this study crumb temperature does not cross 100 °C due to incorporation of evaporation-condensation mechanism in this model. Baking process completes within 25 min of processing time once the temperature of crumb becomes stable at 98 °C. Formation of crust and browning of bread surface were studied using earlier reported kinetic model and it predicted more browning at bread edges than the surfaces. However, predicted browning index was well within the range (< 52).     

A new method for finite element transitional mesh generation

In the preparation of finite element meshes, inclusion of transitional blocks is important in order to construct optimal meshes. In this paper, a new method is proposed which is capable of generating quaddominated arbitrary transitional meshes. These meshes are well graded and do not require any mesh smoothening algorithm. The inverse isoparametric mapping combined with an elimination procedure is used to construct transition zones. This new algorithm is described in detail and its efficiency is illustrated with appropriate examples. Different methods available for inverse isoparametric mapping are discussed with their merits and limitations. Many of the existing techniques for inverse isoparametric mapping require the calculation of some special coefficients which may vary with the element type. These techniques lose their clarity and efficiency in the case of three dimensional and higher order two dimensional elements. In this paper, a generalized iterative procedure is proposed to carry out the inverse isoparametric mapping. The computations in this approach are already part of every finite element program based on the isoparametric formulation. Hence implementation of the new algorithm is very simple and straightforward.     

Characteristics of Gel-chromatographic Fractions of Starch in Relation to Rice and Expanded Rice-Product Qualities

Starch from waxy and nonwaxy rices was separated on Sepharose. In nonwaxy rice, the major (void volume) fraction stained a varying shade of blue with iodine depending on the sample. The water-insoluble amyolose content as estimated in milled rice flour was highly positively correlated with the λ_max of the iodine colour as well as with the „amylose”︁ content of the fraction. Debranching with pullulanase showed that the fraction had the dual character of being both amylopectin and amylose. A second fraction was for the most part true amylose. The volume of expanded rice product seemed to increase with average molecular weight of starch. The highest average molecular weight of starch corresponded to analytical values of water-insoluble amylose as estimated in rice flour and the same corresponded to the greatest expansion volume.