Color changes kinetics during deep fat frying of kohlrabi (Brassica oleracea var. gongylodes) slice

Impact of the Temperature Reconditioning of Cold-Stored Potatoes on the Color of Potato Chips and French Fries

The effect of temperature reconditioning on cold-stored potato tubers was investigated for three popularly consumed potato varieties (Shangi, Unica, and Dutch robjin) grown in Kenya. The potatoes were stored at 4 °C for 30 days, followed by removal and storage at 22 ± 3 °C for 9 days during which changes in sugar concentration were evaluated every two days. In parallel, potato chips and French fries were processed, and their colors were determined. The results showed that sugar content decreased significantly with increasing reconditioning time. The relative decrease in fructose content was the highest (p < 0.05) in Dutch robjin (57.49%), followed by Shangi (49.22%) and Unica (38.18%). Glucose content decreased by 54.1% in Dutch robjin, 49.5% in Shangi, and 50.8% in Unica. The lightness (L*) of French fries and chips increased significantly (p < 0.05) with reconditioning time while the redness (a*) values decreased significantly (p < 0.05) across all varieties. The correlation between lightness and the total reducing sugar content of the potatoes was r < -0.93, indicating a strong negative correlation for both products. The coefficient of determination showed that the glucose content of the tubers accounted for 80.5-97.6% of the lightness of French fries and 88.4-94.2% for potato chips. The critical glucose content range for acceptable products in French fries and chips based on the color (L* and a*) values was 12-22 mg/100g and 8-14 mg/100g, respectively, for the varieties in this study.

Effects of ultrasound and microwave pretreatments of carrot slices before drying on the color indexes and drying rate

The aim of this study was to examine the impacts of microwave pretreatment (MWP) and ultrasonic pretreatment (USP) on drying time (DT), mass transfer kinetics, effective water diffusivity (Deff), rehydration rate, color index (L*, a*, b*), and the surface shrinkage of carrot slices when dried in a hot air dryer (70 °C). The microwave process was performed for 0, 15, 30, 45, and 60 s before drying of carrot slices. In addition, the ultrasound process was performed in an ultrasonic bath (40 kHz and 150 W) for 0, 5, 10, 15, and 20 min. The results confirmed that the MWP and USP decreased the DT (higher water loss) of carrot slices. Deff values for microwave-pretreated slices were considerably higher than those for nontreated carrot slices (p < 0.05). The Deff calculated by Fick's second law was increased from 8.69 × 10-10 to 10.96 × 10-10 m2 s-1, and from 7.56 × 10-10 to 9.39 × 10-10 m2 s-1, for samples pretreated by microwave and ultrasound, respectively. The empirical value for the drying curves were fitted to the common thin film-equations, and Page's equation was the most suitable to describe the dehydration rate of carrot slices. The average rehydration ratio of nontreated, microwave-treated, and ultrasound-treated carrot slices were 432.3 %, 449.2 %, and 360.9 %, respectively. The redness, yellowness, and surface shrinkage parameters of pretreated samples by microwave were higher than the nontreated slices. The lightness and redness parameters of pretreated carrot slices by ultrasound were higher than the nontreated samples under all conditions.

Effects of gum-based coatings combined with ultrasonic pretreatment before drying on quality of sour cherries

Application of pretreatment methods such as ultrasound and edible coatings is used to reduce processing time and/or preserve food product quality in drying technology. The aim of this research was to measure the impacts of gum-based coatings (guar, sodium alginate, and basil seed gums) in combination with sonication before drying on total phenolic content (TPC), antioxidant capacity (AC), effective water diffusivity (Deff), total color difference (ΔE), surface shrinkage (SS), and rehydration ratio (RR) of sour cherries. Ultrasonic pretreatment (40 kHz, 150 W, at 25 °C, for 12 min) increased the TPC, AC, Deff, and RR, and decreased the drying time, ΔE, and SS values of sour cherries. Edible coating increased the TPC, AC, drying time, and RR, and decreased the Deff, ΔE, and SS values of sonicated sour cherries. The TPC for untreated, uncoated-sonicated, guar gum-coated, sodium alginate-coated, and basil seed gum-coated sour cherries were 2965.9, 3398.1, 3480.8, 3511.0, and 3898.3 Âµg gallic acid equivalent/g dry, respectively. The highest value of AC (71.2±3.7 %) was observed on coated sour cherries by basil seed gum. The experimental data for drying curves were fitted to several widely used models, and the Midilli model using the experimental constants that best represent the drying rate of sour cherries. The edible coatings significantly reduced the color changes and shrinkage of dried sour cherries, with the lowest ΔE and SS values in the basil seed gum-coated samples (p < 0.05).

Production and evaluation of total phenolics, antioxidant activity, viscosity, color, and sensory attributes of quince tea infusion: Effects of drying method, sonication, and brewing process

This study aimed to examine the influence of drying approaches (convective and infrared (IR)), sonication, and brewing time on the total phenolic content (TPC), antioxidant activity (AA), viscosity, color indexes, and sensory attributes of quince tea infusion (QTI). The AA and TPC in the QTI dried in the IR dryer were higher than in the convective dryer. The TPC and AA of QTI prepared by convective and IR dryers increased when the ultrasound treatment and brewing time were increased. In terms of viscosity and Brix, there was no differences between the QTIs and the average viscosity and density of the samples were 1.79 ± 0.28 mPa.s and 3.18 ± 0.07°Brix, respectively. The QTI prepared by the IR has a reddish-brown hue (higher a* value), but the samples prepared with the convective dryer were yellow (higher b* value). The sensory attributes scores of QTI prepared by IR were higher than those of convection-dried samples. In general, the use of an IR dryer for drying grated quince, ultrasound treatment for 8 min, and brewing time for 30 min is a promising condition for the production of QTI with higher TPC and AA, and with appropriate color and sensorial acceptance.

Effects of ultrasound time, xanthan gum, and sucrose levels on the osmosis dehydration and appearance characteristics of grapefruit slices: Process optimization using response surface methodology

In this work, the novel use of ultrasonic pre-treatment and edible coating treatment during osmosis dehydration to optimize the weight reduction, moisture loss, sucrose gain, rehydration, and surface shrinkage using a response surface methodology (RSM) based on a central composite design (CCD) technique was successfully conducted on grapefruit slices. The process parameters include sonication pre-treatment time (5-10 min), xanthan-gum-based edible coating (0.1%-0.3%, w/w), and sucrose concentration (20-50 Brix), were examined and optimized for osmosis dehydration of grapefruit slices. At each step, three grapefruit slices were immersed in an ultrasonic water bath at 40 kHz, 150 W, and 20 C. Then, the sonicated slices were placed in a container contain sucrose and xanthan, and the container was put in a 50 C water-bath for 1 h. The optimum concentration of xanthan gum, sucrose, and time of treatment were predicted to be 0.15%, 20.0 Brix, and 10.0  min, respectively. Under this optimum condition, estimated values of response variables are as follows: weight reduction 14.14%, moisture loss 25.92%, solids gain 11.78%, rehydration ratio 203.40%, and shrinkage 2.90%. The weight reduction and moisture loss increased when the sonication time and sucrose concentration increased. Results demonstrated that the experimental data could be adequately fitted into a linear model with p-value ranging from 0.0001 to 0.0309 for all the variables examined. The rehydration of dried samples increased when xanthan concentration increased. Also, the weight reduction, moisture loss, sucrose absorption, and shrinkage declined with increasing in the xanthan levels.

Optimization of sonication time, edible coating concentration, and osmotic solution °Brix for the dehydration process of quince slices using response surface methodology

The goal of this work was to examine the effects of sonication time, edible coating concentration (with guar gum), and °Brix (sucrose solution) on the osmotic dehydration (OD) parameters (mass reduction, water loss, soluble solids gain, and rehydration ratio) and the appearance properties (color indices and surface area) of quince slices using a response surface methodology (RSM) approach based on the central composite design (CCD), for the optimization of the process. The process parameters, sonication treatment time (5-10 min; 40 kHz and 150 W), edible coating concentration using guar gum (0.05%-0.15%, w/w), and osmotic concentration using sucrose solution (20%-50%, w/w), were investigated and optimized for OD of quince slices. After each OD process, the quince slices were dehydrated in an oven at 70°C for 240 min. Results demonstrated a good correlation between empirical data with the linear model. Using the optimization method, optimum input operating conditions were determined to be a sonication time of 5 min, guar gum concentration of 0.05%, and sucrose concentration of 37.19°Brix. At this optimum point, the OD process of quince slices reached the optimal mass reduction (17.74%), water loss (25.77%), soluble solids gain (8.03%), rehydration ratio (206.19%), lightness (77.6), redness (0.60), yellowness (34.84), total color change (ΔE) (8.92), and area changes (7.59%).

Effect of surface coating with seeds mucilages and xanthan gum on oil uptake and physical properties of fried potato strips

The oil uptake and high-fat/oil content problem associated with fried food products can be decreased using polysaccharides (mucilages and gums) as edible coatings. In this study, the efficiency of seeds mucilages (Balangu, Basil, and Wild sage), and xanthan gum as edible coatings on the oil uptake, moisture retention, and physical properties (color indexes and surface shrinkage) of potato strips during oil frying have been examined. Coating treatment with seeds mucilages and xanthan gum significantly decreased the moisture loss and oil uptake of potato strips (p < .05). Lightness (L*) index values of uncoated-control and coated potato strips decreased during frying. The lowest and highest color change intensity (∆E) and surface shrinkage (%) values were observed for the potato strips coated by Wild sage seeds gum and uncoated-control sample, respectively. The MMF (Morgan-Mercer-Flodin) model was selected as the best equation for describing the color changes intensity kinetics of untreated and treated potato strips during frying. The appropriate coating suspension for reducing the oil content of fried potato strips and improving product appearance quality was 1.0% Wild sage seeds gum.