Band 5, Heft 2

In the present work, de-oiled rice bran (DOB) was exploited for SCP production using three different fungi, namely, Aspergillus oryzae MTCC 1846, Trichoderma viride NRRL 1186 and Aspergillus niger MTCC 1842 under solid state fermentation. DOB was found to contain 9% protein, 39% cellulose, 28% hemicellulose and 24% lignin. All the three cultures have shown more specific growth rate when grown on glucose in comparison to maltose and cellulose. The specific growth rates on glucose were 0.203, 0.201 and 0.196 h-1 and on maltose were 0.173, 0.171, 0.169 h-1 for A. oryzae MTCC 1846, T. viride NRRL 1186 and A. niger MTCC 1842, respectively. All the three microorganisms showed lowest specific growth rate on cellulose 0.119, 0.117, 0.114 h-1 for A. oryzae MTCC 1846, T. viride NRRL 1186 and A. niger MTCC 1842, respectively. The major constituent of dried fungi is crude protein, which contributes to 43% in A. oryzae MTCC 1846, 44% in T. viride NRRL 1186 and 39.2% in A. niger MTCC 1842 on dry basis. Among the three fungi A. oryzae MTCC 1846 shows minimum content of nucleic acids (5.3%) while A. niger MTCC 1842 and T. viride NRRL 1186 showed (6.1%) and (7.2%), respectively.

The thermomechanical property of the rice kernels was investigated using a dynamic mechanical analyzer (DMA). The length change of rice kernels with a loaded constant force along the major axis direction was detected during temperature scanning. The thermomechanical transition occurred in rice kernels when heated. The transition temperatures were determined as 47°C, 50°C and 56°C for the medium-grain rice with the moisture contents of 18.1%, 16.0% and 12.5% (wet basis), respectively. Length change of the rice kernels increased with the increase of the temperature and moisture content. Among the four rice varieties investigated, the results showed that the thermomechanical property was not significantly affected by variety.

The effects of incubation temperature (35-45oC), starter culture level (0.003-0.006%, w/v), and milk total solids content (12.32-15.68%, w/v) on the rheological properties of yogurt were investigated using central composite rotatable design (CCRD) and response surface methodology (RSM). Gelation time during milk fermentation and apparent viscosity of yogurt stored for 3 days were the rheological parameters studied. The results revealed that the gelation time and apparent viscosity of yogurt were significantly affected (P < 0.1) by incubation temperature, starter culture level, and total solids. Incubation temperature had the greatest influence on the gelation time. Higher temperature led to shorter gelation time, but resulted in lower apparent viscosity of yogurt. Apparent viscosity of yogurt was mainly affected by total solids. Higher apparent viscosities were also obtained at lower incubation temperature.

Invertase production by Aspergillus niger in submerged culture was evaluated under different concentrations of sucrose and glucose. When the initial concentration of sucrose was increased from 6.25 to 50 gL-1, a higher biomass production (6.1 gL-1) was observed. The biomass production was increased 4 times more when a glucose-sucrose combination was used as substrate (26.31 gL-1). The strain A. niger produced extracellular beta-fructofuranosidase activity at all test concentrations of the substrate and the highest enzymatic activity (3873 UL-1) was obtained when sucrose was used at 12.5 gL-1. However, with a glucose-sucrose concentration of 25 gL-1 the beta-fructofuranosidase activity was of 23706 UL-1. The maximum rate of invertase enzyme production in presence of sucrose by Aspergillus niger in submerged culture was 3.67 UL-1h-1 at 12.5 gL-1 concentration, while in the case of glucose-sucrose mixture, it was 13.95 UL-1h-1 at a concentration of 25 gL-1. It was observed that the enzyme yield (YE/X) was 1.25 times more in presence of sucrose than with glucose-sucrose combination. In addition, the results suggested that an addition of lower concentration of glucose is a viable option to increase the enzyme secretion by the fungi.

Four yeast cultures, Kluyveromyces marxianus, Kluyveromyces fragilis, Saccharomyces marxianus and Saccharomyces fragilis, were selected for isolation of ?-galactosidase. Enzyme activity was measured for all four strains and found Kluyveromyces marxianus (177 ONPG unit/ml) to have the highest activity. Experimental whey was hydrolyzed with the enzyme extracted from K. marxianus, and the concentrations of enzyme used were 0.5, 1.0, 1.5, 2.0 and 2.5 ml of enzyme per litre of whey. The percentage of lactose hydrolysis was found to be a maximum of 80% in 60 minutes time for the enzyme concentration of 2.0 ml/ litre of whey.

The main objective of this work was to determine an effective moisture diffusivity of long grain rice during fluidized-bed drying (FBD) with inlet drying temperatures ranging of 40-150°C by 10°C/step and to investigate the specific energy consumption of the FBD process. Three initial moisture contents of the local indica paddy were set at 25.0, 28.8 and 32.5% dry-basis. The experimental results of thin-layer fluidized-bed drying for the long grain rice variety were determined and statistically analyzed by non-linear regression method. The results showed that an effective diffusion coefficient was highly dependent on the drying temperature, compared to initial moisture content. Consequently, the mathematical simulation of FBD, using the developed thin-layer drying mentioned above, was evaluated and used for predicting the paddy drying system. The simulated value of energy consumption in each of the drying conditions was comparatively simulated. The simulated results showed that a FBD with low temperatures and low initial moisture content gave higher specific energy consumption than drying with high temperatures and high initial moisture contents. The total specific energy consumption increased with a decreased fraction of re-circulated outlet drying air. According to the simulation results and our previous work, the conclusion is that the long grain paddy drying with FBD technique under a high initial moisture content and drying air temperature over 100°C is the good drying condition for recommendation.

Agglomeration in spray dryers occurs by overlapping the spray patterns of multiple liquid nozzles and the airstreams containing recycled fine powder. In this work, the role of the recycled fines stream is explored by measuring the extent of agglomeration. Two scales are investigated, a small-scale dryer with nominal capacity of ~ 1 kg/h and a pilot-scale dryer of ~ 75 kg/h. Experiments were designed to investigate a number of parameters at three levels: low, medium and high about midpoints that represent typical operation at each scale. These operating points are representative of those available, or potentially available, to operators of agglomerating spray dryers: spray flow rate, spray solids concentration, spray droplet size, powder flow rate, and powder particle size. Drying conditions were kept as constant as possible and all experiments used skim milk powder. A measure of success, called the agglomeration efficiency, was developed based on examining the agglomerated product size distribution relative to the spray and fines. The efficiency reflects the proportion of particles sizes that disappear from the spray size distribution and then appear in the agglomerated product after the fines have been censored from it. Comparisons were made between the reference case of natural agglomeration when the dryer was run without fines, and later forced agglomeration trials with fines. These confirm that fines addition does promote agglomeration. Trials containing fines show that the extent of agglomeration depends principally on the mass flux ratio of fines to spray followed by the particle size of the fines; this can be linked to the probability of interaction between spray and fines in the turbulent interaction zone. The concentration of the spray liquid has a weaker effect on influencing forced agglomeration, but has a major influence on the final product particle size because high solids concentrations promote natural agglomeration when sprays interact. This relates to the development of surface stickiness which influences the success of collisions. The two scales of dryer have the same trends and approximately scale.

Computer simulations are used to represent the essential features of a real system so that analyzers can test their design skills in a convenient and safe environment. Organizations throughout the world are quickly moving to adopt process modelling and simulation as an integral part of their business decision-making and continuous improvement initiatives, due to their significant role in the design of a cost-effective system. ARENA fulfils these needs by mapping processes and simulating discrete and continuous systems. The properties of ARENA software engine involved in its ease of use and rapid mastery, power of complex system modelling, and open architecture to support user applications. This paper outlines how ARENA is applied to model, simulate and analyze the basic production processes. The case study is the bakery's production processes, at which the model creation is explained in detail and the simulation results are analyzed. This study gives a real-life example of how to use ARENA to model a complete production line in an efficient way.

The objective of this study was to evaluate the ability of the Weibull distribution to predict the inactivation of Salmonella in three meat products cooked under isothermal and non-isothermal conditions. Ground turkey thigh (5.09% fat, pH 6.45), turkey breast (0.47% fat, pH 6.04) and pork (17.04% fat, pH 6.36) were inoculated with an 8 strain Salmonella cocktail. The meat was cooked isothermally at 50, 54, 58, 62 and 66ºC, and non-isothermally at two heating rates (5 or 10 ºC/min) to 54, 60 and 66 ºC. Surviving Salmonella were enumerated at intervals during the cooking process. Isothermal survival curves were described by the Weibull distribution, log S (t) = -b (T) tn(T), and its simplified form as a linear equation (n=1). Nonlinearity was observed in Salmonella survival curves. The Weibull distribution described pathogen inactivation better than its simplified linear form for all isothermal trials. The b and n parameters from isothermal data were used to predict the non-isothermal survival curves. Piecewise cubic hermite interpolating polynomial was used to estimate b and n in the non-isothermal program. At 54 and 66 ºC, the Weibull model well predicted the non-isothermal Salmonella survival curves for all meats. The model over-predicted the destruction of Salmonella in three meats at 60 ºC for both heating rates. The accurate prediction of Salmonella destruction at 66 ºC was at a higher temperature than the range of validity reported in the literature.

The size, colour, level of internal damage and external damage of walnuts are four important quality factors. Colour properties (‘L', ‘a', ‘b', hue angle and chroma values) of Bilecik, Yalova-1 and Yalova-3 shelled walnut varieties as a function of moisture content were determined. The average ‘L' values of shelled walnuts decreased with increase in moisture content for Bilecik, Yalova-1 and Yalova-3 walnut varieties. All colour characteristics were affected by the moisture content studied.

The effects of air temperature (50, 60 and 70°C), sample thickness (2, 4 and 6mm) and pretreatment conditions (hot water blanching, 1 and 3% sodium metabisulphite solutions) on the drying characteristics and kinetics of okra were investigated using a convective hot air dryer at a flow rate of 1.5m/s. It was observed that pretreatment conditions, sample thickness and drying air temperature significantly (P<0.05) affected drying rate. Drying rate increases as temperature of drying air increases from 50 to 70°C. The drying curve for all experiments occurred in the falling rate period with no constant rate period. Three thin layer drying models (Page, modified Page I and Wang and Singh) were evaluated using coefficient of determination (R2), root mean square error (RMSE) and the reduced chi square (?2). The three models can appropriately describe the drying kinetics of okra slices considering the different experimental conditions. The effective diffusivity was determined using the Fick’s model and was observed to vary between 1.125x10-8 – 9.93x10-9m2/s and 1.165x10-8 – 7.131x10-9 m2/s for treated and untreated samples. The Arrhenius-type relationship describes the temperature dependence of diffusivity coefficient and was determined to be 16.749kJ/mol and 22.437kJ/mol for treated and untreated samples respectively.

Pre-fermented douchi, also called douchi qu, is a salt-free semi-product of a Chinese traditional fermented soybean food (douchi), which is classified into three types, that is, Aspergillus-type, Mucor-type and Bacteria-type. In this work, angiotensin I-converting enzyme (ACE) inhibitor activities of douchi qu started by different types of cultures were compared. It was found that douchi qu fermented with Aspergillus oryzae, Mucor wutungkiao, Bacillus subtilis natto and Bacillus subtilis B1 showed significantly different (p < 0.05) ACE inhibitor activities with decreasing IC50 values of 0.4991, 0.3535, 0.2294 and 0.0901 mg/mL, respectively. Twenty-five fractions were separated by gel filtration chromatography and the strongest ACE inhibitor activity was observed in a fraction with high contents of glycine, lysine and arginine from B. subtilis B1 fermented sample. Results indicated that the type of starter cultures affected significantly the production of ACE inhibitors in douchi qu, and that B. subtilis B1 could be potential candidate as an inoculant to prepare fermented soybeans with strong ACE inhibitor activity in functional food industry.

In this study, the relationship of oil extraction rate (OER) and fruit ripeness will be determined. The sample of oil palm fruits was collected from the unripe until the overripe stage and the oil content of the mesocarp for fresh fruit bunches (FFB) was extracted by using bunch analysis procedure to get the oil extraction rate. Using the same samples of FFB, the pixel value of images which measure in hue, was determined by developed image analysis software. The images were captured under an outdoor environment in an oil palm plantation. The sunlight intensity of environment was recorded using Extech light meter at various times of the day from morning to afternoon in the oil palm plantation. The result of the experiment that showed a good relationship was found between the oil content of FFB with its image pixel values. The mathematical model was developed in determining the optimum days for FFB harvesting.