Investigation of physicochemical properties of breads baked in microwave and infrared-microwave combination ovens during storage

Staling of breads baked in different ovens (microwave, infrared-microwave combination and conventional) was investigated with the help of mechanical (compression measurements), physicochemical (DSC, X-ray, FTIR) and rheological (RVA) methods. The effect of xanthan-guar gum blend addition on bread staling was also studied. Xanthan-guar gum blend at 0.5% concentration was used in bread formulation. The gums were mixed at equal concentrations to obtain the blend. After baking, the staling parameters of breads were monitored over 5 days storage. During storage, it was seen that hardness, retrogradation enthalpies, setback viscosity, crystallinity values, and FTIR outputs related to starch retrogradation of bread samples increased, whereas FTIR outputs related to moisture content of samples decreased significantly with time. The hardness, retrogradation enthalpy, setback viscosity, and crystallinity values of microwave-baked samples were found to be highest among other heating modes. Using IR-microwave combination heating made it possible to produce breads with similar staling degrees as conventionally baked ones in terms of retrogradation enthalpy and FTIR outputs related to starch retrogradation. Addition of xanthan-guar gum blend decreased hardness, retrogradation enthalpy and total mass crystallinity values of bread samples showing that staling was delayed.     

The effects of gums on macro and micro-structure of breads baked in different ovens

In this study, the effects of gums on macro and micro-structure of breads baked in different ovens (infrared (IR)-microwave combination and conventional) were investigated by the help of image and SEM analysis, respectively. The gums used were xanthan, guar, κ-carrageenan and xanthan-guar blend. The gums were added to the formulation at 0.5% concentration. As a control, no gum added formulations were used. Results of Image analysis demonstrated that xanthan-guar gum blend addition improved bread quality with increasing pore area fractions. It was seen that about 75% of the pores of control breads baked in infrared-microwave combination oven and about 63% of the pores of control breads baked in conventional oven had diameters of above 1000 μm. According to SEM analysis, pores in control breads baked in conventional oven were found to be smaller, and had spherical, oval-like shape as compared to the ones baked in IR-microwave combination oven. Moreover, more homogeneous closed-cell structure was observed for conventionally baked control breads. The pores of breads baked in IR-microwave combination oven were so close to each other which resulted in coalescence of the gas cells to form channels, then the pores were no longer spherical. The starch granules in conventionally baked breads were more distorted and seen as a continuous sheet of gelatinized starch. On the other hand, granular residues and continuous starch structure was observed together in IR-microwave combination heating.     

Degradation of organophosphorus pesticides in wheat during cookie processing

For investigating carryover of some organophosphorus pesticide residues in the cereal food chain from grain to consumer, a study was set up on wheat bran, flour and cookies, with and without bran. Special emphasis was given to malathion and chlorpyrifos-methyl residues in cookies for better protection of consumers. Pesticide-free wheat was placed in a small-scale model of a commercial storage vessel and treated with these pesticides. The residue levels of insecticides were determined in wheat, as well as in bran, flour and cookies produced from stored wheat at various time intervals during storage. A multiresidue analysis was performed using GC–NPD and GC–MS. Malathion and chlorpyrifos-methyl residue levels were higher than the maximum residue limits (MRLs) in wheat after 240 days of storage. MRLs established by the EC for malathion and chlorpyrifos-methyl in wheat are 8 and 3 mg kg⁻¹, respectively. The residue levels of insecticides in flour samples also exceeded the MRL (2 mg kg⁻¹ for both insecticides). Eight months of storage were not effective for reducing the residues in wheat to the levels below MRLs. Although, considerable amounts of the insecticides remained in the bran and flour, the cookie processing significantly reduced the concentrations in general. Chlorpyrifos-methyl was more persistent than was malathion and comparatively less degradation occurred during milling and cookie processing due to its physicochemical properties.     

Thermophilic dark fermentation of acid hydrolyzed waste ground wheat for hydrogen gas production

Batch dark fermentation experiments were performed to investigate the effects of biomass and substrate concentration on bio-hydrogen production from acid hydrolyzed ground wheat at 55 °C. In the first set of experiments, the substrate concentration was constant at 20 g total sugar L⁻¹ and biomass concentration was varied between 0.52 and 2.58 g L⁻¹. Total sugar concentration was varied between 4.2 and 23.7 g L⁻¹ in the second set of experiments with a 1.5 g L⁻¹ constant biomass concentration. The highest cumulative hydrogen formation (582 mL, 30 °C, 1 atm), formation rate (5.43 mL h⁻¹) and final total volatile fatty acid (TVFA) concentration (6.54 g L⁻¹) were obtained with 1.32 g L⁻¹ biomass concentration. In variable substrate concentration experiments, the highest cumulative hydrogen (365 mL) and TVFA concentration (4.8 g L⁻¹) were obtained with 19.25 g L⁻¹ initial total sugar concentration while hydrogen gas formation rate (12.95 mL h⁻¹) and the yield (200 mL H₂ g⁻¹ total sugar) were the highest with 4.2 g L⁻¹ total sugar concentration.     

Pricing and lot-sizing decisions in a two-echelon system with transportation costs

We consider a single-buyer single-supplier system. The market demand is sensitive to the selling price set by the buyer. Both the buyer and the supplier operate with unit product costs, inventory holding costs, and order placement costs. In addition, the buyer is responsible for the freight cost. We formulate a model for determining the optimal lot-sizing and pricing decisions. Existing models for the problem do not consider the transportation costs with price sensitive market demand, and determine the optimal decisions through an exhaustive search. We propose an approximate solution procedure, and report the computational results on the effectiveness of the proposed procedure.     

The Effect of Silver Substitution in Bi1.7Pb0.3Sr2Ca2?xAgxCu3Oy

The effect of Ag substitution on the properties of high-temperature superconductor Bi_1.7Pb_0.3Sr₂Ca_2−x Ag _x Cu₃O _y system have been investigated. The electrical and structural properties of the samples, prepared by the conventional solid-state reaction method, have been characterized by X-ray diffraction (XRD), electrical resistance and scanning electron microscopy (SEM) studies. XRD analysis reveals a multiphase structure of the samples, whereas SEM micrographs indicate some morphological changes induced by silver addition. It was found that an increase of the amount of Ag₂O addition leads to an enhancement of the critical temperature and the percentage of Bi-2223 phase in the phase mixture.     

Recommendations for ammonia borane composite pellets as a hydrogen storage medium

The perspective of this study describes a new concept for ammonia borane (NH₃BH₃, AB) in the form of pellet composited with CoB catalyst to use as a hydrogen storage medium. For the purpose of this, hydrogen storage capacity and physical-chemical properties of composite pellet are examined and tested to investigate effects of specified environmental conditions by exposing pellets in temperature from 22 °C to 80 °C in a long period of time (1 day–4 months). A statistical strategy is provided to detail the investigation for significant differences between holding conditions and their interactions. These results suggest that the changing in holding time is more important than the temperature. The general point of view, there is no change in hydrogen storage properties when the composite pellets held at low temperature about 22 °C for 3 months, and the same trend is also preserved when the composites are kept at the higher temperature for a week. It is concluded that the composite pellets shown performance at hydrogen storage with easy handling and controlled hydrogen generation for on-board energy applications.     

Probiotic properties of ice creams produced with dietary fibres from by‐products of the food industry

The objective of this study was to investigate the effects of adding dietary fibre‐rich by‐products to probiotic ice creams. For this purpose, fruit (grape, apricot, apple)‐ and grain (rice, corn, sunflower, barley)‐based by‐products were added to ice cream. The viability of Lactobacillus acidophilus (ATCC 4357D‐5) and Bifidobacterium animalis subsp. lactis (ATCC 27536) was determined with microbial analyses at 1, 15, 30 and 60 days of storage. In conclusion, it was shown that dietary fibre‐rich by‐products could be used in ice cream with improved survival of the probiotic strains without any adverse effects on the physicochemical, microbiological and sensory properties of the ice cream.