Volume 6, Issue 4

The drying kinetics of apple slices was investigated in a semi-industrial continuous band dryer. Apple slices with a thickness of 5 mm were dried at temperatures of 50, 60 and 70 °C, air velocities of 0.5, 1.0 and 1.5 m/s and chain linear velocity of 1.85E-04, 2.22E-04 and 2.78E-04 m/s. The Weibull model was fitted to the experimental data of moisture ratio against sample position using MATLAB computer program. The low reduced chi-square and RMSE and the high regression coefficients indicated the suitability of the Weibull model for predicting moisture ratio of apple slices during drying in length of continuous band dryer. Correlations of the scale and shape parameter of the Weibull model with the variables of T, Ua and Uc were determined. The transport of water during drying was described by Fick’s second low and effective diffusivity varied from 9.24E-08 to 3.5E-07 m2/s. The energy of activation was described by the Arrhenius equation and varied from 35.37 to 45.51 kJ/mol.

Noncrystalline granular (NCG) starch is a peculiar form of starch. The granules have granular shape but no crystalline structure. It is a middle state between native semi-crystal structure and paste. The conception of NCG starch was presented and its preparation methods for native maize starch were explored. Cross-linking by chloroepoxy propane was adopted as the chemical method while ethanol treatment was adopted as the physical method. Cross bonds and ethanol were both able to protect starch granules from swelling while thermal treatment was able to destroy crystalline structure of the granules. The structure of granule was observed by polarization microscope and scanning electron microscopy (SEM). Change from crystalline to noncrystalline structure was confirmed by X-ray diffraction (XRD). It indicated that preparation of NCG starch with the physical method was better than chemical method. The detailed conditions were: maize starch (40%, w/w) was slurried in 50%-ethanol, underwent thermal treatment at 85°C for 2 minutes, washed with anhydrous ethanol (2000 ml), and freeze dried.

This study evaluated the effect of washing conditions on gel properties of Spanish mackerel and investigated the application of high pressure to improve the gel properties of Spanish mackerel. Alkaline-saline washing process surimi (ASWPS) showed the increase in gel strength by 40.19% than unwashed surimi, and by 26.74% than conventional washing process surimi (CWPS). These increases were associated with the lowered expressible moisture content. However, no differences were found in deformation of gels prepared by different washing processes. Electrophoretic studies revealed that ASWPS had the highest MHC and actin band intensity. Alkaline-saline washing process surimi was subjected to ultra-high pressures of 100, 200, 300, 400, 500 MPa for 30 min at 40°C. The effects of pressure on both springiness and cohesiveness were insignificant. Hardness and chewiness of samples treated at 300 and 400 MPa increased significantly when compared with the control, which increase by 2.68 and 2.40 times at 300 MPa and by 2.87 and 2.70 times at 400 MPa, respectively. However, these values slightly decreased after treatment at 500 MPa. In addition, pressure increased the whiteness of surimi, the higher pressure the more increase.

Central composite rotatable design for k = 3 was used to study the combined effect of feed moisture (12-44%), cowpea concentration (0-20%) and groundnut concentration (0-10%) on the physical and functional properties of extruded sorghum-legume blends in a single screw extruder using response surface methodology. Product expansion ratio, bulk density, total colour change, water absorption capacities at 27°C and 90°C and swelling capacities were determined on the products using standard analytical methods. Expansion ratio, bulk density and total colour of extrudates from the sorghum-legume blends decreased with increasing feed moisture. Increasing the concentration of legumes in the product increased the water absorption capacities at 27°C and 70°C and increased swelling capacities due to the gel forming ability of the macromolecules (proteins and starch) in the products and availability of hydrophilic groups to bind water molecules, thus enhancing the functional properties of the blends. Models developed for the indices gave R2-values ranging from 61.6% (for water absorption capacity at 27°C) to 89.9% (for bulk density) with insignificant lack of fits indicating the adequacy of the model in explaining the data. The optimal conditions noted for producing the puffed extruded snack products with better physical properties and functional characteristics from sorghum-groundnut-cowpea blends were at 16-18% feed moisture, 14-16% cowpea and 6-8% groundnut additions.

Response surface methodology was used to optimize the pretreatments before solar cabinet drying of bitter gourd slices (6-7 mm thick). Central composite design (CCD) was used to conduct the experiments which consisted thirteen experiments with two variables, viz., blanching time (1-5 min) and potassium metabisulfite (KMS) (0.2-0.5 %). After the pretreatments, the bitter gourd slices were dried up to 6 % (Approx.) moisture content (d.b) in solar cabinet dryer at air temperature, relative humidity and air velocity in the range 38 to 62°C, 45 to 55 % and 0.9 to 1 m/s, respectively. The responses taken were chlorophyll retention (mg/100g of dried sample) and texture (hardness) of dehydrated bitter gourd slices. The optimum process condition was found at 4.24 min blanching time and 0.49 % KMS which resulted in 20.15 mg/100g chlorophyll retention and 340.55 g hardness. Some selected quality attributes of solar cabinet dried bitter gourd slices pretreated with the optimized combination of blanching time and KMS were compared with the quality of freeze and open sun dried samples and it was found that quality of solar cabinet dried product was falling in between open sun and freeze dried products. Also, the drying data of bitter gourd slices obtained during solar cabinet, freeze and open sun drying were analyzed and drying constants as well as moisture diffusivity were calculated.

Ohmic heating is an emerging thermal processing technique in which electrical conductivity is one of the most important factors. Inhomogeneous cuboid food models were built with a plate inserted in the center of a food system. The effects of the plate’s electric conductivity on both the surrounding material (?p/?s) and the orientation of the plate in ohmic heating were analyzed with a finite element method. It was revealed that when the plate’s electric conductivity was lower than that of the surrounding material, the plate’s temperature was lower than the surrounding material when the biggest cross-section of the plate was parallel to the electric field. When the biggest cross-section of the plate was perpendicular to electric field, the case was more complicated. The plate’s temperature was higher than that of the surrounding material when ?p/?s was 0.1 and 0.5. The plate’s temperature was lower than that of the surrounding material when ?p/?s was 0 and 0.02. When the plate’s electric conductivity was higher than that of the surrounding material, the plate’s temperature was always lower than that of the surrounding material when the biggest cross-section of the plate was perpendicular to the electric field. When the biggest cross-section of plate was parallel to that of the electric field, the case was more complicated. The plate’s temperature was higher than that of the surrounding material when ?p/?s was 2 and 10. The plate’s temperature was lower than that of the surrounding material when ?p/?s was 50.

Anthocyanins are natural colorants which have gained a growing interest due to their extensive range of colors and beneficial health effects. The red and blue shades of 15 flowers were extracted with 1 % acidic methanol and these extracts were then screened for Total Anthocyanin content (TAC) using the pH method. In this paper the overall anthocyanin content of red and blue flowers was determined at room temperature (25°C). TAC accounts for the antioxidant activity of red and blue flowers. A quantitative relationship between acid-base and redox chemistry was also drawn.

Optimization of process parameters is of critical task in developing an industrial fermentation process for various reasons. Many techniques are available for experimental design and optimization of fermentation process parameters, i.e., fermentation medium composition and conditions, each having its own advantages and disadvantages. In this work response surface methodology (RSM) with central composite design (CCD) of experiments and artificial neural network (ANN) coupled with global optimization technique (TOMLAB’s Direct Alogoritm—gblSolve) are used for optimization of process parameters for the production of alpha amylase using banana peel as the substrate and bacterial source Bacillus subtilis MTCC 441. A 46 run central composite design was used to plan the experiment with six parameters (banana peel concentration, peptone concentration, pH, temperature, incubation time and inoculum size) with five levels. The maximum amylase activity predicted by CCD and ANN is in good agreement with the experimental values at the optimized levels. The present work shows the better optimization and prediction capacity of ANN techniques compared to RSM technique.

In the present study we examined the use of a chemostat system to investigate the impact of changes in the specific growth rate of Saccharomyces cerevisiae CABI 039916 on cellular amino acid profiles and total protein content. This experimental system allowed the unambiguous examination of the link between changes in dilution rate and the culture response, which would have been difficult in batch or fed-batch cultures. Alteration of the specific growth rate (via manipulation of the dilution rate) within a carbon and energy-limited chemostat has a significant impact on the physiology of Saccharomyces cerevisiae. Low dilution rates (<0.1h-1) led to predominantly respiratory metabolism and the maximisation of cellular protein content within the cell (58%), by contrast high dilution rates (>0.2h-1) led to respirofermentative metabolism, where the cellular protein content was minimal (~40%). The content of nearly all amino acids in the yeast protein pool fell significantly as dilution rate increased in parallel with the decline in cell protein content. By contrast, the concentration of two related key food/feed amino acids in the cell protein pool—glutamic acid and arginine could be increased within the cellular protein by 5% (increasing the dilution rate from 0.05h-1 to 0.25h-1) and 1.5% respectively (decreasing the dilution rate from 0.05h-1 to 0.2h-1). Despite previous studies showing that metabolic change was associated with major changes in free amino acid levels, the present study indicates that the total cellular yeast protein amino acid composition is largely invariant despite profound metabolic changes, with one or two key exceptions.

The effects of marination on the weight gain, cooking loss and Warner-Bratzler shear force of three beef muscle types, i.e. blade roast (BR), biceps femoris (BF) and semitendinosus (ST) were investigated by treating them in distilled water (as control), brine solution, tamarind juice, tamarind juice plus salt and satay marinade for 180 minutes. The weight gain of ST muscles were significantly higher (P < 0.01) than the BR muscles in brine solution, tamarind juice plus salt and satay marinade, while ST and BF muscles did not differ significantly (P > 0.01) in all the five treatments. For cooking loss, muscle types did not show a significant difference (P > 0.01) in all marinating treatments except for BR and ST muscles in tamarind juice (P = 0.00023). The presence of salt in tamarind juice gave better results in tenderising ST muscles than using tamarind juice alone.

Gelatinization and retrogradation of a high amylose cornstarch modified by hydroxypropylation were studied by DSC. It was found that the gelatinization temperature of the starch was decreased and a narrow gelatinization range was measured by DSC after hydroxypropylation. The decreasing of the gelatinization temperature is explained by disrupting inter- and intra-molecular hydrogen bonds, while the narrowing of the gelatinization endotherm is explained by destroying the amylose-lipid complex. Morphologies of the starch granules with and without iodine treatment were studied under microscopy with normal and polarized lights. Brightness and birefringence decreased with increasing molar substitution since crystal structure in starch granular was partly destroyed. Weaker retrogradation was observed for the hydroxpropylated starch, ascribed not only to steric effects imposed by the bulky hydroxypropyl groups in amylopectin, but also to the removing of amylose-lipid complexes during alkaline treatment.

Mung bean starch has been manufactured by sour liquid processing for hundreds of years in China. Ions in sour liquid will impact the starch properties and vermicelli quality. To understand the role of the ions act on the processing and starch quality, different concentrations of NaCl or KCl effect on precipitation rate of starch slurry, starch properties and the potential quality of vermicelli were studied. Results showed that starch slurry took a shorter time to start precipitating when NaCl or KCl concentration increased from 0.027mol/L to 0.088 mol/L. Light transmittance, swelling power and peak viscosity of mung bean starch was significantly decreased from 0.02mol/L to 0.10mol/L NaCl or KCl. Increasing To, Tp, Tc and Tc-To was noticed from 0.02mol/L to 0.10 mol/L NaCl or 0.04mol/L to 0.08mol/L KCl. These changes would be helpful for improving vermicelli quality. However increasing solubility at test concentrations of NaCl and KCl was not good for vermicelli quality.

This work provides a novel view of explaining water uptake behavior commonly observed in legume seeds. A model proposed by Peleg to describe the mechanical changes in biomaterials transitioning from a glassy state to a rubbery state was used to describe water uptake by legume seeds exhibiting a lag during imbibition and to characterize the mechanical changes of the seed coat as affected by soaking time. The seeds characterized by Peleg’s model possessed seed coats with a glass transition temperature higher than ambient soaking conditions. Alternatively, the water uptake behavior of legume seeds that did not exhibit a lag phase was characterized by an exponential equation used in polymer science to model solvent sorption by materials above their glass transition. A modified exponential equation was developed to model the mechanical behavior of these seed coats as affected by soaking time. Seeds characterized by the exponential equation possessed seed coats with a glass transition temperature near ambient soaking conditions. This work demonstrates, through the use of two separate models, water uptake behavior of legume seeds can be explained by the glass transition temperature of the seed coat.