Deep eutectic solvent pretreatment of cork dust - Effects on biomass composition, phenolic extraction and anaerobic degradability.

In this study, phenolic compounds using deep eutectic solvents (DES) were extracted from cork dust, and the biogas production potential of DES-treated cork dust samples was determined. The DES treatment was carried out using choline chloride and formic acid (1:2 M ratio) at various temperatures (90, 110 and 130 °C) and treatment times (20, 40 and 60 min) at a solid-to-solvent ratio of 1:10 g mL-1. The highest total phenolic content (137 mg gallic acid equivalent (GAE) g-1 dry cork dust) was achieved at 110 °C/20 min. The extracts exhibited an antioxidant capacity of up to 56.3 ± 3.1 % 1,1-diphenyl-2-picrylhydazyl (DPPH) inhibition at a dilution rate of 100. DES treatment resulted in minimal sugar solubilization at low temperatures, while approximately 42 % of the xylan fraction in the biomass degraded under severe conditions (e.g., 130 °C/60 min). Catechin, 4-hydroxybenzoic acid and gallic acid were the major phenolics in DES extracts. The biogas yield of DES-treated cork dust increased with treatment severity. The highest biogas yield (115.1mLN gVS-1) was observed at 130 °C/60 min, representing an increase of 125 % compared to the untreated sample. SEM images revealed that the surface structure of the samples became smoother after mild pretreatment and rougher after harsh pretreatment. Compositional and FTIR analyses indicated that a higher biogas formation potential was associated with increased cellulose content in the substrate, which could be attributed to hemicellulose solubilization in the hydrolysate. Overall, DES pretreatment effectively enhanced phenol extraction and anaerobic degradability.

Comparison of antifungal activity of essential oils of clove, lemongrass and thyme for natural preservation of dried apricots.

Currently, the majority of fresh apricots destined for the production of dried apricots undergo sulphur oxide fumigation before drying to protect the fruit against fungal spoilage. To eliminate the use of sulphite, packaging assisted with essential oil is a promising strategy to increase shelf-life of dried apricots since it does not impact its flavor characteristics. In this study, three essential oils were selected: clove, lemongrass and thyme. They were screened for antifungal activity against Eurotium spp. with different methods: micro- and macro-dilution and agar-diffusion. Growth/no-growth data were used to develop models for all three methods. Clove exerted the strongest antifungal activity with an inhibitory concentration of 0.075%, 0.035% and 0.05% through respectively micro-dilution, macro-dilution and agar diffusion. For thyme the following values were obtained: 0.775%, 0.070% and 0.100%. This means that the antifungal activity of thyme is 10 times lower in micro-dilution and 2 times lower in macro-dilution and agar diffusion compared to clove. Through micro-dilution, lemongrass was found to have the second highest antifungal activity (0.25%). When used in the volatile atmosphere of dried apricots and in macro-dilution, the antifungal activity of lemongrass was the lowest, with respective values of > 0.200% and 0.105% for G/NG prediction.

Investigation of dielectric properties, total phenolic content and optimum formulation of microwave baked gluten-free cakes.

This study discusses the production of microwave baked gluten-free cakes formulated by mixing buckwheat flour and rice flour at different concentrations. Three different ratios of buckwheat flour to rice flour (20:80%, 30:70%, 40:60%) and two different gum types (xanthan and guar gum) with a white layer cake recipe were employed. The batters were baked in microwave oven at different microwave powers (540 W, 450 W, 360 W) for different baking times (3 min, 3.5 min, 4 min). The effect of microwave power, baking time and buckwheat flour concentration on weight loss, color, specific volume, porosity, total phenolic content and dielectric properties were investigated. The optimum microwave power, baking time and buckwheat flour concentration were found as 432.77 W, 3 min, 40% for guar gum added cakes and 360 W, 3.70 min and 29.23% for xanthan gum added ones. It was found that weight loss and color values of the cakes that were baked at the optimal conditions were less than those of control cakes. On the other hand, total phenolic content, specific volume, porosity, dielectric constant and dielectric loss factor values were higher for guar gum added cakes compared to control samples. In addition, it was observed that the cakes prepared with guar gum had similar pore size distribution with control cakes. As a conclusion of the study, it can be declared that surface color and specific volume problems of microwave baking could be solved by addition of guar gum to the formulation which also enables the production of functional, phenolic rich microwave baked cakes.

Phenolic content and some physical properties of dried broccoli as affected by drying method.

Broccoli samples ( Brassica oleracea) with an initial moisture content of 82.87% (wb) were dried using microwave technology (18, 36, and 54 W/g). Convective drying was used as a control group. The dependent variables investigated in the study were phenolic content, color, rehydration capacity, and microstructure of broccoli samples. Moreover, the best fitting thin layer model to the experimental moisture ratio was determined. The phenolic contents were found as 892.4, 740.6, and 759.8 mg gallic acid/100 g dry matter for fresh, convective dried, and microwave (MW) dried at 54 W/g broccoli samples, respectively. The total phenolic content of samples dried at 54 W/g was closest to fresh samples compared to other MW power intensities and convective drying. A similar result was obtained for color values too. L*, a*, and b* of microwave-dried samples at 54 W/g were comparable to fresh broccoli. Another important result obtained from the study was the insignificant effect of drying conditions on rehydration capacity. In addition, it was found that microwave power had a positive effect on drying time; as the microwave powers applied were compared, the shortest drying time was reached at 54 W/g. When the process durations of microwave drying and convective drying were compared, it can be reported that a much lower process time for microwave drying was obtained with respect to convective drying. Drying in microwave oven has reduced the drying time by 49-52%. In the light of the results obtained, it may be declared that it is possible to produce high-quality dried broccoli samples in a very short time by using microwave drying at 54 W/g.

Dielectric properties, optimum formulation and microwave baking conditions of chickpea cakes.

The aim of this study was to correlate dielectric properties with quality parameters, and to optimize cake formulation and baking conditions by response surface methodology. Weight loss, color, specific volume, hardness and porosity were evaluated. The samples with different DATEM (0.4, 0.8 and 1.2%) and chickpea flour concentrations (30, 40 and 50%) were baked in microwave oven at different power (300, 350, 400 W) and baking times (2.50, 3.0, 3.50 min). It was found that microwave power showed significant effect on color, while baking time showed effect on weight loss, porosity, hardness, specific volume and dielectric properties. Emulsifier level affected porosity, specific volume and dielectric constant. Chickpea flour level affected porosity, color, hardness and dielectric properties of cakes. The optimum microwave power, baking time, DATEM level and chickpea flour level were found as 400 W, 2.84 min, 1.2% and 30%, respectively. The comparison between conventionally baked and the microwave baked cakes at optimum points showed that color difference, weight loss, specific volume and porosity values of microwave baked cakes were less than those of conventionally baked cakes, on the other hand, hardness values were higher. Moreover, a negative correlation between dielectric constant and porosity, and weight loss values were detected for microwave baked samples. A negative correlation between dielectric loss factor and porosity was observed. These correlations indicated that quality characteristics of a microwave baked cake sample can be assessed from dielectric properties. These correlations provides understanding on the behavior of food material during microwave processing.

Optimization of formulation of soy-cakes baked in infrared-microwave combination oven by response surface methodology.

The aim of present work is to optimize the formulation of a functional cake (soy-cake) to be baked in infrared-microwave combination oven. For this optimization process response surface methodology was utilized. It was also aimed to optimize the processing conditions of the combination baking. The independent variables were the baking time (8, 9, 10 min), the soy flour concentration (30, 40, 50 %) and the DATEM (diacetyltartaric acid esters of monoglycerides) concentration (0.4, 0.6 and 0.8 %). The quality parameters that were examined in the study were specific volume, weight loss, total color change and firmness of the cake samples. The results were analyzed by multiple regression; and the significant linear, quadratic, and interaction terms were used in the second order mathematical model. The optimum baking time, soy-flour concentration and DATEM concentration were found as 9.5 min, 30 and 0.72 %, respectively. The corresponding responses of the optimum points were almost comparable with those of conventionally baked soy-cakes. So it may be declared that it is possible to produce high quality soy cakes in a very short time by using infrared-microwave combination oven.

Optimization of ethanol production from microfluidized wheat straw by response surface methodology.

In this study, wheat straw was pretreated with a microfluidizer to improve its enzymatic hydrolysis and ethanol yields. The pretreatment was performed at various pressures (500, 1000, and 1500 bar) and solid loadings (1, 2, and 3%). The microfluidized biomass was then subjected to hydrolysis and simultaneous saccharification and co-fermentation (SSCF) experiments at different enzyme loadings (5, 10, and 15 FPU/g dry wheat straw) using a mutant yeast. The results indicated that the microfluidization method alters the structure of biomass and leads to a reduction in lignin content. The samples pretreated at 1% solid loading contained the minimum lignin concentration and provided the maximum sugar and ethanol yields. These results signified that the microfluidization method is more effective on biomass at low solid loadings. The process conditions were optimized for higher ethanol and sugar yields using response surface methodology (RSM). The optimum pressure and solid and enzyme loadings were found as 1500 bar, 1%, and 15 FPU/g dry wheat straw, respectively. The yields obtained at this condition were 82%, 94%, and 65% for glucose, xylose, and ethanol, respectively. High sugar yields implied that microfluidization is an effective pretreatment method for cellulosic ethanol production. On the other hand, low ethanol yield may indicate that the microorganism was sensitive to inhibitory compounds present in the fermentation medium.

The effect of different formulations on physical properties of cakes baked with microwave and near infrared-microwave combinations.

The aim of this study was to determine the effect of different formulations on color and textural characteristics of different cakes during baking in microwave and near infrared-microwave combination ovens. For comparison, cakes were also baked in conventional ovens. Color and hardness for both types of baking schemes were found to be dependent on formulation. Cakes containing Simplesse, a fat replacer consisting mostly of whey protein, baked in microwave and near infrared-microwave combination ovens were found to be the firmest cakes.

Investigation of dielectric properties of different cake formulations during microwave and infrared-microwave combination baking.

Dielectric properties can be used to understand the behavior of food materials during microwave processing. Dielectric properties influence the level of interaction between food and high frequency electromagnetic energy. Dielectric properties are, therefore, important in the design of foods intended for microwave preparation. In this study, it was aimed to determine the variation of dielectric properties of different cake formulations during baking in microwave and infrared-microwave combination oven. In addition, the effects of formulation and temperature on dielectric properties of cake batter were examined. Dielectric constant and loss factor of cake samples were shown to be dependent on formulation, baking time, and temperature. The increase in baking time and temperature decreased dielectric constant and loss factor of all formulations. Fat content was shown to increase dielectric constant and loss factor of cakes.