Carrot Cubes Research Articles

Potential of drying carrot using ozone pre-treatment: Mass transfer modelling and techno-functional properties

The objective of this study was to investigate the influence of ozone (O3) as a novel pre-treatment for carrot drying. To establish the best conditions, carrot cubes were exposed to increasing concentrations of O3 (0–40 µg/L) for 2 h before air convective drying at 70 °C. According to the mass transfer models, the results highlighted a correlation between higher effective diffusivity (4.654 × 10−11 m2/s) and increasing O3 concentrations. Furthermore, dried carrot cubes exhibited sustained levels of phenolic compounds (29.33–56.42 mg GAE/100 g), carotenoids (5.17–14.58 mg/100 g), antioxidant activity (1.27–5.01 µM Trolox/g), and inhibitory activity (IC50) against α-amylase (56.02–95.63 μg/mL) and α-glucosidase (29.72–69.08 μg/mL) as the O3 concentration increased up to 40 µg/L. Differential scanning calorimetry analysis showed different thermal profiles on carrot cubes due to O3 treatment. Furthermore, the O3 pre-treatment significantly accelerated and enhanced the rehydration of carrot cubes, resulting in faster absorption of moisture and restoration to the initial texture and volume. Overall, this study shows that O3 pre-treatment (40 µg/L) can be a rational strategy to optimize drying process, bringing an innovative and straightforward solution to preserve the techno-functionality of carrots. Future research should investigate the long-term stability of bioactive compounds and sensory characteristics of dried carrot subjected to O3 pre-treatment.

Developing a spouted bed for combined radio frequency-hot air treatments to improve the heating uniformity in high-moisture carrot cubes

Uneven and thermal runaway heating is the biggest obstacle to industrial applications of radio frequency (RF) technology, while the existing research mainly focuses on the RF heating uniformity of low-moisture foods with fewer reports about the useful solutions to avoid heterogeneous heating of high-moisture foods. Thus, the combined RF-hot air treatment in a newly designed spouted bed (RFHASB) was developed in this study to improve the RF heating uniformity of fresh carrot cubes selected as the high-moisture model sample. This RFHASB was used to evaluate effects of four processing parameters (cone angle, nozzle diameter, inlet air speed and electrode gap) on the RF heating rate and uniformity of carrot cubes with comparison of those between the RFHASB and the hot air treatment alone in the spouted bed (HASB). The results showed that the RFHASB effectively alleviated the non-uniform heating in the treated high-moisture carrot cubes through mixing and stirring particles. Both heating rate and uniformity index in RFHASB increased with decreasing cone angles and electrode gaps but decreased when nozzle diameters and inlet air speeds were reduced. The RFHASB had better heating performances than the HASB. These findings may provide the theoretical basis for the effective drying of high-moisture fresh fruits and vegetables in RFHASB.

Enzyme activity and nutritional profile of different-sized carrot cubes treated with supercritical carbon dioxide

This study evaluated changes in the enzyme activity, color, carotenoids, sugar profile, individual phenolic compounds, and antioxidant capacity of supercritical carbon dioxide (SCCD)-treated carrot cubes of different sizes (1 cm and 2 cm). Results demonstrated that SCCD reduced the activities of polyphenol oxidase (PPO) and peroxidase (POD) more in 1 cm carrot cubes than in 2 cm carrot cubes. Nevertheless, the a* , b* , and ∆E values of 1 cm SCCD-treated were enhanced compared to 2 cm SCCD-treated samples. The carotenoids, phenolic compounds, and antioxidant capacity of 1 cm SCCD-treated samples were increased under moderate processing conditions. In contrast, the nutritional composition in 1 cm SCCD-treated samples was lower than in 2 cm SCCD-treated samples at harsh processing conditions. The principal component and correction analysis displayed a visual variation between the enzyme activities and nutritional composition of 1 cm and 2 cm carrot cubes after SCCD processing. According to the results above, 1 cm carrot cubes processed with SCCD at 10 MPa, 35 ℃, and 45 min are the most effective at preserving fresh-cut carrots with relatively high enzyme inactivation and the highest retention of bioactive compounds. This work provides a more comprehensive theoretical basis for optimizing SCCD processing for fresh-cut carrots and recommendations for industrial production.

Combined Heat and Mass Transfer Associated with Kinetics Models for Analyzing Convective Stepwise Drying of Carrot Cubes.

Stepwise drying is an effective technique that promotes energy saving without additional capital cost. The stepwise drying mode was investigated for energy consumption and dried product qualities using a coupled heat and mass transfer model associated with kinetics equations of volume shrinkage and degradation of β-carotene in carrot cubes. Simulations were performed using a finite element method with extension of a chemical species transport. Validation experiments were carried out under constant drying modes at 60 °C, 70 °C and 80 °C using a lab-scale convective hot air dryer. The verified models were subsequently employed to investigate the effects of two step-up drying modes (60 to 70 °C and 60 to -80 °C). The optimal drying condition was determined using the synthetic evaluation index (SI) with criteria of high specific moisture evaporation rate (SMER), low shrinkage ratio and β-carotene degradation. Simulated results showed comparable agreement with experimental data of moisture content, shrinkage ratio and β-carotene ratio. Step-up drying of 60 to 70 °C gave the highest SMER of 0.50 × 10-3 kg of water evaporated per kWh, while the operation at constant temperature of 80 °C gave the lowest value of 0.19 × 10-3 kg of water evaporated per kWh. Model-predicted results showed less shrinkage of carrot cubes, but higher degradation of β-carotene under step-up drying compared to single-stage drying under temperature of 60 °C. Based on the highest SI value (0.36), carrot cubes were optimally dried under step-up mode of 60 to 70 °C.

An Edible and Quick-Dissolving Film from Cassia Gum and Ethyl Cellulose with Improved Moisture Barrier for Packaging Dried Vegetables.

A quick-dissolving edible film was made from cassia gum (CG) incorporated with ethyl cellulose (EC). Mechanical results show that addition of 5% EC based on CG gave rise to the highest tensile strength (TS) of the composite film. Scanning electron microscopy revealed that excess addition of EC slightly decreased the homogeneousness of films. Fourier transform infrared spectroscopy showed that the compatibility between CG and EC was good and the incorporation of EC changed the original interaction of molecules by forming hydrogen bonds with CG. Although film light transmittance decreased, it is transparent enough for packaging. The film water vapour barrier property improved dramatically by blending CG and EC, although they showed dissolution rates over 80% in boiling water after 5 min. The dried carrot cube packaged by CG-EC films showed lower mass growth rates in 53% RH. Therefore, the film presents a potential application in packaging of dried vegetables in convenience foods.

Obtaining model parameters of drying kinetics for highly shrinkable materials without knowing the surface area a priori

AbstractShrinkage parameters of highly shrinkable materials such as length, diameter and surface area during drying are difficult to quantify in situ. However, these are significant components of an accurate model. In this study, an attempt to isolate the surface area effect is reported in order to fetch the REA model (reaction engineering approach) parameters without knowing it a priori. Carrot cube and cabbage leaf were selected as experimental material and dried with hot air under a range of conditions. Shrinkages was calculated using an optical method which is used to qualitatively compare with that “calculated” using the current approach. By matching the experimental temperature and moisture content profiles against time after obtaining REA parameters for both samples without knowing the surface area, the surface areas can be “calculated” numerically. Surface area was found to be affected by sample temperature as well as the moisture content. Drying simulations can be well carried out when correlating the surface area against sample moisture content X and temperature T, and it provides the best accuracy in predicting data on T and X vs. time. In addition, carrot cube can shrink ideally while cabbage leaf cannot. The overall relative errors of predicted moisture content and temperature were less than 1%.

Effect of ultrasound pretreatment on physical, bioactive, and antioxidant properties of carrot cubes after centrifugal dewatering

Ultrasound-pretreated centrifugal dewatering (UCD) is a novel method for vegetable dewatering process in the central kitchen. In this study, carrot cubes were blanched and dewatered by UCD at various ultrasonic frequencies (0, 20, 30, 45, 80 and 100 kHz). Conventional centrifugal dewatering (CCD) was performed for comparison. At similar centrifugal conditions, the dewatering capacity of UCD was >30% higher than CCD. The retention of β-carotene, phenolic and flavonoid substances also increased by 10–50%. The optimized ultrasonic frequency for UCD processing was 45 kHz. At this optimized condition, the reducing power of carrot cubes was improved by 3.4%. Retention of total phenolics, flavonoids and β-carotene were increased by 33.89%, 48.51% and 26.71%, respectively. Nevertheless, a moderate reduction (25.82%) of hydroxyl radical scavenging capacity was observed for the UCD. Overall, UCD can be used as an alternative improved method of CCD to enhance the dewaterability and quality of carrot. Highlights Ultrasound-pretreated centrifugal dewatering (UCD) improved dewaterability of carrot and retained its nutritional values. UCD increased the dehydration rate of carrot by >30% than conventional centrifugal dewatering (CCD). The β-carotene, phenolics and flavonoids substances in UCD carrot was 10-50% higher than that of CCD. UCD has a positive effect on antioxidant activity of carrot.

Modeling of vacuum‐ and ultrasound‐assisted osmodehydration of carrot cubes followed by combined infrared and spouted bed drying using artificial neural network and regression models

AbstractThis research seeks to understand the effects of using various vacuum pretreatments (0 and 200 mBar) and different ultrasound power levels (0 and 130 W) on osmodehydration and spouted bed drying of carrot cubes. Effects of using diverse air‐drying temperatures (55, 65 and 75°C), infrared power (0 and 250 W) and the presence of Teflon beads as inert particles (0 and 30% w/w), were also investigated. The effects of above‐mentioned parameters on drying time and physicochemical characteristics of dried carrot samples including hardness, shrinkage, total carotenoid content, rehydration ratio and total color difference (∆E) were examined. The results explicitly demonstrated that the utilization of osmodehydration in conjunction with ultrasound and vacuum (UVOD) had shorter drying time compared to those just treated with osmotic dehydration. The highest total carotenoid content and the lowest ∆E were belonged to the samples exposed to UVOD. The efficiency of artificial neural network (ANN), genetic algorithm based ANN (GANN) and Regression mathematical models were investigated to determine the nonlinear relationship between the inputs and outputs variables. To find the efficiency of all models, mean square error were compared. The results indicate that the ANN model could provide more reliable prediction over the other models.Practical applicationCombined IR‐convective drying has gained increased attention in the recent years because of the fast and efficient transfer of heat, cheap processing cost, and uniform heat transfer, which resulted in products with better organoleptic properties than common drying processes. The combination of hot air and IR radiation resulted in a synergistic effect, leading to more efficient drying than either individual convective or IR drying. Vegetables with high levels of moisture content can be effectively dried using pretreatments such as ultrasonically vacuum‐assisted osmotic dehydration, which reduced the drying time.

Investigation of Hot Air–Assisted Radio Frequency as a Final-Stage Drying of Pre-dried Carrot Cubes

Carrot cubes were firstly blanched by radio frequency (RF) heating and then pre-dried by ultrasound-assisted osmotic dehydration (UOD). Hot air–assisted radio frequency (HA-RF) was applied as a final-stage drying method for pre-dried carrot cubes in this study. HA-RF drying characteristics and associated quality of carrot cubes were evaluated by comparing with those dried by conventional hot air (HA) and vacuum freeze (VF) drying. Moisture content of carrot cubes was reduced to 50% when compared with conventional HA drying (550 min). LF-NMR and MRI results showed that the inside moisture migrated to the outside along with the evaporation of surface moisture during the drying process which indicated that HA-RF was a relatively uniform drying process. Logarithmic model was found to be more suitable for HA-RF drying with R2, RMSE, and SEM value at 0.994, 0.013, and 0.004, respectively. Carrot cubes dried by HA-RF had expected redness and relatively high hardness, and Vc retention rate was comparable with that dried by VF. This study demonstrated that HA-RF is an effective final-stage drying method for pre-dried carrot cubes.

Multistage relative humidity control strategy enhances energy and exergy efficiency of convective drying of carrot cubes

Industrial drying is one of the most energy intensive unit operations encountered in most industrial sectors. Therefore, much effort has been devoted to energy savings in drying. Most methods applied to convective drying are based on heat recovery from dryer exhaust. However, there are major limitations on how much of the energy can be recovered cost-effectively. Here a new concept based on the relative humidity (RH) control of convective drying of carrot cubes was evaluated with the purpose of enhancing the energy and exergy efficiency of drying. Numerical simulations of heat and mass transfer were performed to investigate hot air drying behavior of carrot cubes. The model fitted well the moisture ratio and the material temperature data with average relative errors of 6.5% and 0.8%, respectively. Results show that both the energy loss caused by exhaust air and the irreversibility loss of thermodynamic process decreased with increase in RH of the drying medium from 4% to 40%. Multistage relative humidity control strategy improved both the drying rate and exergy efficiency. Among the tested schemes, the three-stage RH control strategy, i.e. (1) RH of 40% for 2 h, (2) RH of 20% for 2 h and (3) RH of 4% for 3.5 h was found to be the strategy with the highest exergy efficiency (53.3%). It was almost three times higher than that for constant 4% RH values.

Shrinkage modeling, drying kinetics and quality assessment of carrot cubes dried in a two stage spouted bed drying process

A relatively easy to apply mathematical model based on the second Fick’s law inserting a correction factor α to describe drying kinetics of unblanched carrot cubes in a two stage drying process considering shrinkage, using a semipilot spout bed dryer for the first stage and a lab scale spout fluidized bed dryer for the second stage was successfully developed. Drying of the carrot cubes was done at three drying temperatures 60, 70 and 80°C. It was possible to keep air velocity constant in each drying stage 1.65 m/s at the first stage and 0.68m/s and 1.35m/s in the annulus and spout respectively in the second stage. Effective moisture coefficients obtained 0.821 to 1.02 x 10-9 m2/s for the first drying stage and 0.262 to 0.481 x10-9 m2/s for the second drying stage were according to the published data for carrots in this kind of dryer considering shrinkage. The model fitted accurately the experimental drying with SEE of 0.122 to 0.210 when shrinkage was considered and α correction factor was inserted compared to SEE of 1.002 to 1.263 when shrinkage was neglected. Also residual analysis of models confirmed the adequacy of the model to predict drying kinetics. Quality parameters obtained β-Carotene retention (80±5.4%), peroxidase residual activity (30-35%), pectin methyl esterase residual activity (83-95%) and rehydration ratio (4.5-5.3 water absorbed/kg dried solids) resulted similar to the ones reported in the literature and except for β-Carotene retention they all showed dependence with drying temperature.

Investigation of hot air-assisted radio frequency heating as a simultaneous dry-blanching and pre-drying method for carrot cubes

Hot air-assisted radio frequency (HA-RF) heating was studied as a novel method for simultaneous dry-blanching and pre-drying of carrot cubes, and ultrasound-assisted osmotic dehydration (UOD) was also investigated as an improved conventional pre-drying method for comparison. After conventional hot water blanching, UOD was optimized by orthogonal experiment and after 30.0 min UOD treatment at optimal condition (10% sodium chloride, 40% sucrose and 1,4 solid-liquid ratio), moisture content of carrot cubes decreased to 58.5% (w.b.); and after 9.0–12.0 min HA-RF treatment, moisture content decreased to 60.9–71.9% (w.b.) and enzyme activity (peroxidase-POD) could be reduced to <5% at the same time. UOD was better in lowering water activity and retaining redness of carrot cubes, while HA-RF treated samples had higher vitamin C content and better texture. Besides, HA-RF pre-treatment had lower energy consumption (<0.20 kW∙h/kg) than that of hot water blanching plus UOD treatment (0.67 kW∙h/kg). This study indicated that HA-RF was an effective simultaneous dry-blanching and pre-drying method for carrot cubes. This study proposed and investigated hot air-assisted radio frequency (HA-RF) heating as a new simultaneous dry-blanching and pre-drying method for carrots cubes. This technology may replace the conventional blanching and the following pre-dewatering or 1st stage drying process, since HA-RF pretreatment maintained good quality of carrot cubes and had lower energy consumption, and most importantly, this method can blanch and partially dehydrate samples at the same time without using water. Therefore, it holds great potential as the industrial pre-treatment method for drying of fruits and vegetables. • HA-RF simultaneously dry-blanching and pre-drying of carrot cubes was studied. • Moisture content decreased to 60.9–71.9% after HA-RF pre-drying treatment. • HA-RF was better in retaining vitamin C and maintaining texture of carrot cubes. • HA-RF had lower energy consumption and avoided generating of waste water. • HA-RF is an alternative simultaneous dry-blanching and pre-drying method.

Effect of Ohmic Heating on the Physical Properties of Fried Carrot Cubes

Effect of Ohmic Heating on the Physical Properties of Fried Carrot Cubes

Shape up! How shape, size and addition of condiments influence eating behavior towards vegetables.

Practical approaches to increase consumption of healthy foods such as vegetables are needed. Controlling eating rate is a promising strategy, since faster eating rates have been related to higher food intake. Food properties can be modified to influence eating rates, but little is known about the impact of vegetable dimensions and condiment additions on eating rates of vegetables. This study determined the influence of shape, size and condiment properties on eating behavior towards carrots. Eating behavior (mastication time, number of chews, chewing frequency, eating rate) was determined for carrots with same total weight but different shapes (cube, julienne), and varying in size, number of pieces and aspect ratio. Carrots presented in one large cube required the lowest mastication effort (shortest mastication time, fewest chews) among all pre-cut carrots. Carrot cubes required less mastication effort leading to higher eating rates than carrots julienne. To investigate the effect of condiment addition on eating behavior towards carrots, mayonnaises varying in fat content and viscosity were combined with carrots, and mastication behavior and bolus properties were determined. Mayonnaises, in particular those with high fat content or low viscosity, contributed to faster bolus formation of carrots. Carrots were swallowed with less particles of larger sizes when mayonnaises were added. These results indicate that a specific particle size is not a prerequisite to induce swallowing, and that other bolus properties such as lubrication or cohesiveness trigger the urge to swallow. We conclude that eating behavior towards carrots can be controlled by relatively small changes in both carrot and condiment properties. To increase carrot intake by increasing eating rate, we suggest to avoid cutting of carrots or to add condiments, which could be an effective strategy to increase vegetable consumption or to decrease mastication effort to target the elderly population.

The effect of trays’ slope in the tunnel dryer on drying rate of carrot cubes

Drying of food is perhaps the oldest method of food preservation. The aim of this study the analysis of the effect of changing the slope angle of trays in a tunnel dryer model on the drying rate. Real experiments were carried out for trays’ slopes of 0, 5, 10 and 15°. Carrots’ cubes were dried at a constant temperature of 60°C, with air flow velocity of 1.2 m/s. Also this process was simulated using the COMSOL Multiphysics 4.3 software. The research results showed that increasing slope angle of tray disrupted the laminar flow of the dried cubes layer through the drying air stream and forced the partial air flow through the layer. Thus, the contact surface of the heated air with the material particles and the drying rate have been increased and made it possible to shorten the duration of the drying.

Investigation of radio frequency heating as a dry-blanching method for carrot cubes

Radio frequency (RF) heating was investigated as a novel dry-blanching method for carrot cubes in this study. RF heating uniformity and effectiveness for inactivating peroxidase (POD) in carrot cubes were evaluated along with carrot quality (texture, color and vitamin C (Vc) content) after blanching. Results showed that RF heating uniformity increased with increasing RF electrode gap, and was affected by container shape and size, in which carrot cubes filled in cylinder shape container had better RF heating uniformity than that in rectangle container. Besides, POD activity of carrot cubes was reduced by 90–95% after RF blanching for 3.0–7.0 min at different electrode gaps (8.0–8.6 cm). RF dry-blanching maintained hardness, redness and Vc content of carrots cubes much better than hot water blanching. This study indicated that RF heating is an effective dry-blanching method for carrot cubes.

Temperature gradient control during microwave combined with hot air drying

Fresh carrot cubes were blanched and dried by microwave processing combined with hot air drying. Material temperature, temperature difference and size of cube were optimised in terms of total vitamin C content, colour change, drying time, sensory evaluation and rehydration ratio of dried samples. During a stage under the optimal drying condition, drying rate was affected by temperature gradient, as evidenced by changed shrinkage. The effect of different temperature gradients on the drying rate and quality was compared with that under the optimal condition by using fitted shrinkage models of the optimised material temperature, temperature difference and size of cube. The quality of dried carrot cubes under the average temperature gradient (ATG) of 6 °C mm−1 was better than that under other ATGs. A simple linear control method was developed based on the control for industrial production. Results showed that the product quality and drying time of samples in linear control were similar to those dried at 6 °C mm−1.

Drying based on temperature-detection-assisted control in microwave-assisted pulse-spouted vacuum drying.

An online temperature-detection-assisted control system of microwave-assisted pulse-spouted vacuum drying was newly developed. By using this system, temperature control can be automatically and continuously adjusted based on the detection of drying temperature and preset temperature. Various strategies for constant temperature control, linear temperature control and three-step temperature control were applied to drying carrot cubes. Drying kinetics and the quality of various temperature-controlled strategies online are evaluated for the new drying technology as well as its suitability as an alternative drying method. Drying time in 70 °C mode 1 had the shortest drying time and lowest energy consumption in all modes. A suitable colour, highest re-hydration ratio and fracture-hardness, and longest drying time occurred in 30-40-50 °C mode 3. The number of hot spots was reduced in 40-50-60 °C mode 3. Acceptable carrot snacks were obtained in 50-60-70 °C mode 3 and 70 °C mode 2. All temperature curves showed that the actual temperatures followed the preset temperatures appropriately. With this system, a linear temperature-controlled strategy and a three-step temperature-controlled strategy can improve product quality and heating non-uniformity compared to constant temperature control, but need greater energy consumption and longer drying time. A temperature-detection-assisted control system was developed for providing various drying strategies as a suitable alternative in making a snack product. © 2016 Society of Chemical Industry.

Evaluation of quality parameters of dried carrot cubes in a spout-fluidized-bed dryer with and without draft tube

Unblanched Carrot cubes (0.9 × 0.9 cm) were dehydrated in a spout-fluidized-bed dryer with and without draft tube. The temperatures used for drying in the annular region were (60, 70 and 80 °C) and they were combined with the same temperatures in the spout. No constant period was observed in the drying curve during the drying process, so a polynomial degree 5 or 6 was used to fit the experimental data in order to estimate the effective diffusion coefficients. The effective diffusion coefficients calculated are similar to the ones reported in the literature (0.66 to 1.60 × 10 to 9 m2/s) for carrots dried in spout-fluidized-bed dryers. As quality parameters, the β carotene content was estimated and it was found that practically no degradation occurred in any drying experience. Also the peroxidase (POD) residual activity and the pectin methyl esterase (PME) residual activity were estimated and the POD residual activity resulted between (40 and 60 %) and PME in the range of (70–100 %) depending on the drying temperatures. Rehydration ratio also resulted similar to the values reported in the literature 5.2–6.3 with respect to the dehydrated mass. A loss of around 33–40 % of soluble solids was found by leaching process during rehydration experiences. No difference in the quality of dried product was observed with or without the use of the draft tube however the required air per kilogram of dried solid was 7.8 % lower when the draft tube was used making the drying process 7.8 % more economic.

Model-based investigation of heat and mass transfer for selecting optimum intermediate moisture content in stepwise drying

We developed 3-D computer based model for heat and mass transfer during hot air drying of carrot cubes to predict the moisture content. Thermal energy, specific moisture evaporation rate (SMER) and drying time were predicted for stepwise-drying-air temperatures ranging from 60 to 70°C with various sizes of carrot cubes (10, 20 and 30mm). The cubes were dried at constant temperatures of 60°C and 70°C, step up temperature (60°C/70°C) and step down temperature (70°C/60°C). The drying temperature was changed at different intermediate moisture content levels (20–80%) of carrot. The lowest thermal energy consumption, the highest SMER and the shortest drying time were obtained at temperature in a step up mode associated with intermediate moisture content of 70% wet basis.