Bran-induced effects on the evolution of bubbles and rheological properties in bread dough.

Evolution of bubbles is the key to volume development in bread dough. The influence of wheat bran on bubble growth in bread dough through the mixing, fermentation, and proofing stages is described as a function of its level of addition. Confocal laser scanning microscopy in combination with image processing tools was used to obtain the bubble size and shape parameters. The relationship between bubble behavior and dough rheology was mapped using biaxial extension and dynamic oscillatory rheometry studies. With increase in level of bran addition, mean bubble size decreased corresponding to each stage and showed an inverse relationship with dough overpressure and elastic modulus. Addition of wheat bran was observed to suppress the bubble coarsening phenomenon in dough. Experimental observations indicated the plausibility of coalescence-mediated bubble growth in bread dough during the latter stages of fermentation and proofing, which was hindered in the presence of bran particles. PRACTICAL APPLICATION: The results of this work provide an insight to the underlying mechanism by which wheat bran addition impacts the volume development in bread dough. The inferences presented in this research work can be used as a basis to study bubble dynamics in an opaque food system such as bread dough. This information would be of interest to industrial researchers working on the new product development of aerated bakery products with functional fibrous ingredients.

Effect of temperature abuse on frozen army rations: Part 2: Predicting microbial spoilage.

Numerically simulated heat transfer model of frozen US military rations was combined with microbial kinetics to predict the microbial spoilage of the food products, during two possible temperature abuse scenarios. An army breakfast menu box containing five different food items was selected for conducting this research. One of the food item in the menu box, beefsteak, was chosen for detailed microbial study. A microbial predictive tool was used to identify and evaluate the kinetics of the most prone microorganism that can grow in a beefsteak. Numerical predictions suggested that the food items exposed to external temperatures ranging from 20°C to 40°C can be allowed to stay at those temperatures for maximum times of 28.7h to 11.9h, respectively. The food items can be allowed to stay inside the broken freezer for a maximum time of 186h, to ensure microbial safety in the case of freezer failure.

Effect of temperature abuse on frozen army rations. Part 1: Developing a heat transfer numerical model based on thermo-physical properties of food.

Numerical simulation was carried out to predict the effect of external temperature conditions on thermal behavior of frozen US military rations, during storage and transportation. An army breakfast menu box containing beefsteaks, concentrated orange juice, peppers & onions, French toast, and Danishes, was selected for conducting this study. Thermo-physical properties of each food item were characterized using their composition and differential scanning calorimeter (DSC). Apparent heat capacity method was used to account for the latent heat of phase change during simulation of thawing and freezing. Numerically simulated results were experimentally validated using a gel-based model food system and the food items in the menu box. The average deviation between numerically predicted temperature and experimentally measured temperature for the model food system was approximately 1°C and for the targeted food items the deviation ranged from 2°C to 5°C, depending on the food item.

Media optimization for biosurfactant production by Rhodococcus erythropolis MTCC 2794: artificial intelligence versus a statistical approach.

This paper entails a comprehensive study on production of a biosurfactant from Rhodococcus erythropolis MTCC 2794. Two optimization techniques--(1) artificial neural network (ANN) coupled with genetic algorithm (GA) and (2) response surface methodology (RSM)--were used for media optimization in order to enhance the biosurfactant yield by Rhodococcus erythropolis MTCC 2794. ANN and RSM models were developed, incorporating the quantity of four medium components (sucrose, yeast extract, meat peptone, and toluene) as independent input variables and biosurfactant yield [calculated in terms of percent emulsification index (% EI(24))] as output variable. ANN-GA and RSM were compared for their predictive and generalization ability using a separate data set of 16 experiments, for which the average quadratic errors were approximately 3 and approximately 6%, respectively. ANN-GA was found to be more accurate and consistent in predicting optimized conditions and maximum yield than RSM. For the ANN-GA model, the values of correlation coefficient and average quadratic error were approximately 0.99 and approximately 3%, respectively. It was also shown that ANN-based models could be used accurately for sensitivity analysis. ANN-GA-optimized media gave about a 3.5-fold enhancement in biosurfactant yield.

Use of response surface optimization for the production of biosurfactant from Rhodococcus spp. MTCC 2574.

The production of biosurfactant from Rhodococcus spp. MTCC 2574 was effectively enhanced by response surface methodology (RSM). Rhodococcus spp. MTCC 2574 was selected through screening of seven different Rhodococcus strains. The preliminary screening experiments (one-factor at a time) suggested that carbon source: mannitol, nitrogen source: yeast extract and meat peptone and inducer: n-hexadecane are the critical medium components. The concentrations of these four media components were optimized by using central composite rotatable design (CCRD) of RSM. The adequately high R2 value (0.947) and F score 19.11 indicated the statistical significance of the model. The optimum medium composition for biosurfactant production was found to contain mannitol (1.6 g/L), yeast extract (6.92 g/L), meat peptone (19.65 g/L), n-hexadecane (63.8 g/L). The crude biosurfactant was obtained from methyl tert-butyl ether extraction. The yield of biosurfactant before and after optimization was 3.2 g/L of and 10.9 g/L, respectively. Thus, RSM has increased the yield of biosurfactant to 3.4-fold. The crude biosurfactant decreased the surface tension of water from 72 mN/m to 30.8 mN/m (at 120 mg L(-1)) and achieved a critical micelle concentration (CMC) value of 120 mg L(-1).

Solid-state fermentation for enhanced production of laccase using indigenously isolated Ganoderma sp.

Laccase production by solid-state fermentation (SSF) using an indigenously isolated white rot basidiomycete Ganoderma sp. was studied. Among the various agricultural wastes tested, wheat bran was found to be the best substrate for laccase production. Solid-state fermentation parameters such as optimum substrate, initial moisture content, and inoculum size were optimized using the one-factor-at-a-time method. A maximum laccase yield of 2,400 U/g dry substrate (U/gds) was obtained using wheat bran as substrate with 70% initial moisture content at 25 degrees C and the seven agar plugs as the inoculum. Further enhancement in laccase production was achieved by supplementing the solid-state medium with additional carbon and nitrogen source such as starch and yeast extract. This medium was optimized by response surface methodology, and a fourfold increase in laccase activity (10,050 U/g dry substrate) was achieved. Thus, the indigenous isolate seems to be a potential laccase producer using SSF. The process also promises economic utilization and value addition of agro-residues.