Volume 7, Issue 6

The present study was aimed at finding the optimal conditions for maximum gallic acid production using polyurethane-immobilized Aspergillus niger cells and determining the operational stability of recycled cells for gallic acid production. Maximum gallic acid (142 µg/ml) was produced with 1% tannic acid at 40°C, pH 5.0, with polyurethane foam size of 1.5 cm3 cubes after 48 h under submerged fermentation at 220 rpm, as compared to free cells, which produced 72 µg /ml gallic acid in 72 h at 37°C and pH 5.0. Continuous production of gallic acid by recycling of the immobilized cells resulted in maximum gallic acid production of 199 µg/ml after the fourth cycle, and thereafter remained stable till the seventh cycle and could be continued till the tenth cycle. Pyrogallol, a degradation product of gallic acid and gallic acid decarboxylase (GADC), was also monitored under static and aerobic states and showed comparable values, in contrast to bacteria where aeration caused inhibition. However, 72.73% inhibition of GADC activity by oxidizing agents with simultaneous increase in gallic acid production was observed. This is the first report of gallic acid production by immobilized A. niger cells, producing higher amounts of gallic acid in a shorter cultivation time.

Vacuum cooling technology is a proven technology widely applied on precooling of leafy vegetables, mushrooms, baked goods, fish, sauces, cooked foods, and particulate foods. Vacuum cooling is known as a rapid evaporative cooling technique for moist and porous products. Vacuum cooling has some advantages, such as shortened processing time, extended product shelf life, and improved product quality and safety. The aim of this paper is to apply the vacuum cooling technique to the cooling of purslane and show the pressure effect (for 0.7 kPa, 1 kPa, 1.5 kPa) on the cooling time and temperature decrease. Another purpose of this article is to compare conventional cooling (cooling by refrigerator) with vacuum cooling. It has been seen that purslane can be cooled much more rapidly and efficiently with vacuum cooling than with conventional cooling.

Moisture sorption isotherms of red onion slices were determined at 30, 40, 50, and 60°C using the standard gravimetric static method over a range of relative humidity from 0.11 to 0.83. The experimental sorption curves were fitted by seven empirical equations: modified Henderson, modified Chung–Pfost, modified Halsey, modified Oswin, modified Smith, modified BET, and GAB. Also three types of Artificial neural network models: linear, multilayer perceptron, and radial basis function were tested and developed to predict the equilibrium moisture content of onion slices and the selected models were trained by using related algorithms. The modified Oswin model was found acceptable for predicting adsorption moisture isotherms and fitting to the experimental data, based on the coefficient of determination (R2= 0.991), mean relative percent error (MRE=15.019), and standard error of estimation (SEE=1.371). Besides, multilayer perceptron model with four layers (2: 17: 14: 1) was selected as the best artificial neural network for estimation of onion slices’ equilibrium moisture content by considering R2= 0.993 and good performance. The net isosteric heat of adsorption of moisture was determined by applying the Clausius–Clapeyron equation to the sorption isotherms at different temperatures. The net isosteric heat of adsorption of red onion slices varied between 1.46 and 4.96 kJ/mol at moisture content varying between 2% and 52% (d.b.).

Developments in low temperature drying of food products are still an interesting issue; especially with respect to the energy efficiency. This research studies the energy efficiency that can be achieved by a dryer using air which is dehumidified by zeolite. Experimental results are fitted to a dynamic model to find important variables for the drying operation. The results show that ambient air temperature as well as the ratio between air flow for drying and air flow for regeneration, affect the energy efficiency significantly. Relative humidity of used air, and shift time have a minor effect on the dryer performance. From the total work, it can be noted that the dryer efficiency operated at 50-60°C achieves 75 percent, which is attractive for drying of food products.

Artificial neural network (ANN) was successfully applied to model fermentation parameters for biosurfactant production by Bacillus subtilis ATCC 6633 using sugar cane molasses. Cell growth and biosurfactant production were monitored along the surface activity of the cell-free broth. Response surface methodology (RSM) as a formal statistical model building system was used for the ANN development. The network predicted biosurfactant concentration was 0.381 g/l which showed almost no differences with the relevant experimental value which obtained according to the RSM arrangement. Furthermore, the ANN surface tension reduction was 30.48 mN/m, which was within 3.24% of the experimental value. Comparisons between RSM and the ANN showed preference of using ANN as complementary to RSM and not as a replacement to it.

Flavor is one of the most important features of food, especially of coffee. The evaluation of this sensory feature is complex yet indispensable in quality control of instant coffees. In this work, an artificial neural network (ANN) was developed for instant coffee classification based on an electronic nose (EN) aroma profile. To this purpose, a hybrid algorithm was developed, containing: bootstrap resample methodology; factorial design and sequential simplex optimization to tune network parameters; an ensemble multilayer perceptron (MLP) trained with backpropagation for coffee classification; and causal index procedure for knowledge extraction from the trained ANN. The produced neural network classifier correctly recognizes 100% of coffees studied. Furthermore, the causal index employment allowed inference of some rules on how the coffees were separated according to the sensors available in EN. The results indicate that the applied methodology is a promising tool for instant coffee quality control.

The carob pod, an important fruit of the food industry in the production of concentrated syrup, is rich in potentially health-promoting phenolic compounds and sugars. Moreover, one of the important bioactive components of carob is D-pinitol, and it has some beneficial effects on human metabolism. The optimum conditions for extraction of D-pinitol and total phenolic compounds (TPC) from cultivated and wild types of carob pods were determined using response surface methodology (RSM). The Box-Behnken Design (BBD) was used to investigate the effects of three independent variables; extraction temperature (ºC), dilution rate (w/v), and extraction time (h) on the response, D-pinitol and the total phenolic compounds. The optimum extraction conditions obtained using the response optimizer were an extraction temperature of 80ºC, a dilution rate of 1:4, and an extraction time of 2h. Under the mentioned above conditions, the maximum D-pinitol and TPC concentrations were 9.67 g/L and 5916.55 mg/L in wild carob pod extract, respectively.

The objective of this experiment was evaluate of the impact damage to pinto bean seeds where seed moisture content (9.25, 12.51, 15.01, 17.52, 20.01% wet basis), impact velocity (5.5, 8, 10, 12.5 and 15m/s) and seed orientation (end and side) were independent variables. The study was conducted under laboratory conditions, using an impact damage assessment device. The results showed that impact velocity, moisture content and seed orientation significantly influenced the physical damages of pinto beans at 1% level. Increasing the impact velocity from 5.5 to 15m/s caused an increase in the mean values of damage from 0.39 to 37.30%. With increase the moisture content from 9.25 to 17.52%, the mean values of percentage of damaged beans decreased significantly from 41.24 to 4.27%. However, by a higher increase in the moisture from 17.52 to 20.01%, the mean values of physically damaged beans showed a nonsignificant increasing trend. There was an optimum moisture level of 17.52% at which seed damage was minimized. The relationship between the percent of physical damage with impact velocity and beans moisture content was expressed mathematically. It was found that the percentage damage to seeds was a quadratic function of moisture content and impact velocity. Impact to the end of the seeds (18.62%) produced the higher damage than side orientation (13.12%).

The effect of soybean dietary fiber in the functional and mechanical properties of restructured products from ribbonfish induced by their different treatments was investigated. Different amount of soybean dietary fiber (0, 10, 20, 30, or 50g/kg) was added at the same time as ice water to maintain similar moisture level in all samples. Then the samples with the same level of soybean dietary fiber were treated by high pressure (300MPa, 10min, P), high pressure followed by cooking (300MPa for 10min, then 90 ℃ for 20min, PC), and cooking after setting (40 ℃ for 30min, then 90 ℃ for 20min, SC), respectively. Results obtained suggest that soybean dietary fiber increased the gel strength of sample gels regardless of the treatments, and improved the texture properties of gels induced by PC and SC with almost imperceptible effect on the whiteness. The presence of soybean dietary fiber in the surimi gels also resulted in the increase in myosin heavy chain (MHC) band intensity. For gels with the same level of soybean dietary fiber, the high pressure treatment only made them softer, more elastic, and more translucent, and they kept their native color, compared with the other two treatments. The gels induced by PC had a significant increase in gel strength compared to that treated by SC.

Mechanical damage of seeds due to harvest, handling, and other processes is an important factor that affects the quality and quaintly of seeds. This study evaluated impact damage to the mung bean seeds with moisture contents of 9.54 to 25% wet basis and subject to impact velocities from 10 to 25 m/s using a laboratory impact damage assessment device. The results showed that impact velocity, moisture content, and the interaction effects of these two variables significantly influenced the percentage physical damage in mung ban seeds (p<0.01). Increasing the impact velocity from 10 to 25 m/s caused a significant (p < 0.05) increase in the mean values of damage from 0.53 to 31.78%. The mean values of physical damage decreased significantly (p < 0.05) by a factor about two (from 22.41 to 11.24%), with increase in the moisture content from 9.54 to 20%. However, by a higher increase in the moisture from 20 to 25%, the mean value of damage showed a non-significant increasing trend. There was an optimum moisture level of 20%, at which seed damage was minimized. An empirical model composed of seed moisture content and velocity of impact developed for accurately describing the percentage of physical damage to mung beans. It was found that the model has provided satisfactory results over the whole set of values for the dependent variable.

The efficient prediction of freezing processes is important for the frozen food industry with the purpose of preserving food quality. A comparison is made between the finite difference and finite volume methods to predict the unsteady 2D temperature distribution for the freezing of three different ground meat cylinders, with variable convective boundary conditions. Experiments were carried out to measure the local heat transfer coefficients as a function of freezing time and location. Time-dependent air temperature conditions caused by thermostat action were included in the analysis. The meat thermophysical properties as density, specific heat, and thermal conductivity are assumed to vary non-linearly with temperature. The experimentally measured time-temperature data were compared with the simulation results obtained by both numerical methods. According to statistical test results (RE %), the finite volume method gave the best fit quality. The finite volume method is more accurate for simulating the freezing process, as well as estimating the freezing time of this product

Thermal process is still the most used and safer method for food preservation. Although the mathematical modelling of heat transfer has been used for thermal process evaluation, microbial validation is rarely carried out, and the evaluation of retortable stand up pouch processes were not studied. The present work employed a finite elements analysis model (FEA) for the evaluation of a conductive meat pet food process sterilization in stand up retortable pouches. The results obtained by the model showed good agreement with the experimental values, for both temperature histories and microbial inactivation comparison. The results obtained demonstrate the utility of using mathematical models for describing the heat transfer and microbial inactivation in food thermal process, and reinforce that it can be a powerful tool in food process evaluation and design.

The growing demand for safer and high-quality food products creates the need for better knowledge of the processes involved in food production. The computational fluid dynamics (CFD) have been widely used to better understand food thermal process, one of the safest and most frequently used methods for food preservation. However, no consistency in mathematical models has been observed, especially on the boundary conditions definition. The present study has evaluated four methodologies for the definition of boundary conditions for heating water in two commercial bottles: (M1) temperature profile of heating water (T∞) and convective heat transfer coefficient (h), (M2) T∞ as boundary condition for the outside package wall, (M3) T∞ as boundary condition for the outside heated liquid edge, and (M4) internal temperature profile (T=T(x,y,z,t)), previously measured in the inner package wall, as boundary condition for the outside heated liquid edge. Models that considered the measured value of h e T∞ as boundary condition showed good agreement with experimental values, compared by thermal history and sterilization value (F). The models that considered the temperature profile of the heating water or the inner package wall as boundary conditions, showed faster heating. By over-estimating the product heating rate, those models are not appropriated for thermal process modelling, as it compromises the safety and preservation of food products.

The purpose of the present study was to explore the effects of feed moisture and the addition of whey protein isolate on some physicochemical properties of the obtained extrudates from potato flakes. Extrudates were produced using a laboratory single-screw extruder. Conditions during extrusion were: screw speed - 200 rpm; compression ratio - 3:1; extruders temperature zones - 120, 150, 160 °C; diameter of the nozzle - 5 mm. With increasing of feed moisture content and protein level, there was a significant rise of density as well as lowering of expansion of extrudates. As the feed moisture content increased from 13 to 20 percent w.w. the water absorption index (WAI) increased and the water solubility index (WSI) decreased. The feed protein level increased the protein content and decreased WAI. A maximum of WSI was observed at feed moisture content 20 percent w.w. and protein level 18 percent w.w. The extrusion and the protein addition do not affect the equilibrium moisture of the potato flakes extrudates.

The rheological characterization of food is important for efficient product and process design. Although its importance in semi-arid regions, there are only a few studies regarding the rheological properties of cactus pear products in the literature. The present work has used the Mitschka-Briggs-Steffe method for evaluation of the rheological behavior of cactus pear concentrated pulps. The pulps have shown pseudoplastic behavior. The flow behavior index (n) shows a constant value in the evaluated conditions, and its average value was considered in the evaluated temperature and concentration range. The consistency index (k) has shown dependency of concentration and temperature, being well modeled by a modified Arrhenius equation. Thus, the rheological parameters of cactus pear concentrated pulps can be obtained using a single equation, related with temperature, concentration and shear rate. The obtained data are potentially useful for future studies on product development, food properties and process design.