Carrot Slices Research Articles

Modeling Mass Transfer Kinetics and Mass Diffusivity During Osmotic Dehydration of Blanched Carrots

Osmotic dehydration of 3.5 mm thick blanched carrot slices was carried out in order to study the effect of sucrose concentration, solution temperature and time on mass transfer kinetics and mass diffusivity. The experiments were conducted at the combinations of four sucrose concentration (30, 40, 50 and 60% w/w) and four solution temperatures (25, 37.5, 50 and 62.5°C). At each combination, nine time intervals (10, 20, 30, 40, 50, 60, 80, 100 and 120 min) were selected to determine the moisture loss and sucrose gain. Sample-to-solution ratio was kept 1:10 w/w through all the experiments. It was found that sucrose concentration and time of osmosis increased mass transfer whereas; solution temperature showed effect only on solid gain. Azuara’s models were used to determine the mass transfer kinetics and variable mass diffusivity coefficients. The average moisture diffusivity and solid diffusivity values were in the range 2.23×10-8 to 12.85×10-8 m2/s and 1.20×10-8 to 7.64×10-8 m2/s, respectively. Also, at each concentration, the values of activation energies for moisture loss and solid gain were found to be in the range 12.46 to 24.98 kJ K-1 mol-1 and 9.68 to 31.27 kJ K-1 mol-1, respectively.

Antioxidant capacity of a new crispy type food products determined by updated analytical strategies

The updated analytical strategies were employed to determine the antioxidant capacity of hydrophilic and lipophilic extracts of a new crispy type food products such as crunchy apple slices, crunchy apple slices with cinnamon, crunchy beetroot slices with vinaigrette taste, crunchy carrot slices and crunchy tomato slices. The total antioxidant capacity (TAC) was calculated as a sum of the antioxidant capacity of hydrophilic and lipophilic extracts originating from the sample. Antioxidant capacity was measured directly by cyclic voltammetry (CV), against 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical cation (ABTS+) and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), and by photochemiluminescence (PCL) assay against superoxide anion radical (O2-·). The total polyphenol content in hydrophilic extracts was measured with Folin–Ciocalteu’s reagent. The rank of TAC obtained with updated analytical strategies was as follows: crunchy beetroot slices with vinaigrette taste>crunchy apple slices with cinnamon≈crunchy apple slices>>>crunchy tomato slices>crunchy carrot slices. The values of TAC determined by CV method were comparable with those provided by DPPH assay but they were twofold lower than those obtained by ABTS and PCL assay. The CV assay highly correlated with ABTS and PCL methods (r=0.99). The applied updated analytical strategy for determination of the antioxidant capacity proved to be useful tool for screening new crispy type food products.

First Report of Artichoke Bacterial Stem Rot Caused by Pectobacterium carotovorum subsp. carotovorum in China

A new disease on globe artichoke (Cynara scolymus L.) was observed in the springs of 2008 and 2009 and during the spring and fall seasons of 2010 in commercial fields (nearly 1,000 ha) in Changde, Hunan Province, China. Characteristic symptoms were wilting and necrosis of the outermost leaves and dark brown discoloration of the vascular tissue and pith of the stem base. Eventually, the plants wilted and died. Nearly 5, 35, and 4% (2008, 2009, and 2010, respectively) of the artichoke fields were destroyed because of the disease. Manual weeding and cuttings often led to the development of typical soft rot during propagation. To investigate the causal agent of the disease, isolations were made from rotted stems of field artichoke plants on nutrient agar (NA). Bacteria consistently isolated from the diseased tissues formed gray-white, glossy, convex, translucent, and round colonies on NA. The bacterial cells were gram-negative rods with two to eight peritrichous flagella. Ten isolates were negative for oxidase, arginine dehydrolase, H2S, gelatin liquefaction, and tryptophan ammonialyase. Isolates were positive for catalase, reduced NO3 to NO2, indole, glucuroide, galactosidase, Voges-Proskauer test, and β-galactosidase, along with being facultatively anaerobic and insensitive to erythromycin (40 μg/ml). Negative results were obtained for utilization of maltose, gluconate, and phenylacetic acid, and positive results were obtained from arabinose, glucose, mannose, N-acetyl-glucosamine, mannitol, and sodium citrate for all isolates. Acid was produced from glucose, inositol, rhamnose, melibiose, arabinose, mannitol, sucrose, and amarogentin. All test results were similar to reference strain PCC1000 (GenBank Accession No. JF721959) of Pectobacterium carotovorum subsp. carotovorum. These isolates could also cause soft rot of Chinese cabbage stem, carrot slice, pepper, lettuce and artichoke stems, and tomato and potato slices within 48 h at 28°C in an artificial inoculation test (3). PCR amplification was carried out by utilizing universal 16S rDNA primer pair 16SF/16SR and pel gene primers Y1/Y2 (1). The 16S rDNA and pel gene sequences of isolate HNXDT002 (GenBank Accession Nos. JF721958 and JF721960, respectively) had 99 and 93% nucleotide identity with strains of P. carotovorum subsp. carotovorum (GenBank Accession Nos. U80197 and CP001657, respectively). Pathogenicity was confirmed by needle-stab inoculation (1 × 108 CFU/ml) at the stem on three healthy artichoke plants held at 28°C for 48 h. Sterile distilled water was used as a negative control. Within 72 h after inoculation, water-soaking and soft-rot symptoms were observed on all inoculated artichoke plants, while controls remained healthy. The bacterium was recovered only from rotted stems of inoculated plants. In recent years, P. carotovorum was reported on such plants as Pinellia ternata (4) and Chinese cabbage (2) in China. To our knowledge, this is the first report of bacterial rot disease caused by P. carotovorum subsp. carotovorum on artichoke in China.

Periods of constant and falling-rate for infrared drying of carrot slices

The aim of this work was to study the infrared drying process of carrot slices and to determine coefficients related to the heat and mass transfer of the process. Fresh carrots were used, dried until constant weight in a dryer with infrared heating source. Different models were utilized to fit the experimental data of constant and falling drying rate periods. It was verified that the coefficients of heat and mass transfer, during the constant drying rate, significantly increased with temperature on rise. The Diffusion Approximation, Two Terms, Midili and Verna models satisfactory represented the falling period of drying rate of carrot slices. The effective diffusion coefficient increased with temperature and this relationship can be represented by the Arrhenius equation, obtaining activation energy to the drying process of 29.092 kJ mol-1.

Low Field MRI Detection With Tuned HTS SQUID Magnetometer

We set up a low field (LF) magnetic resonance imaging (MRI) system with a tuned high- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> (HTS) superconducting quantum interference device (SQUID) consisting of a SQUID magnetometer and a liquid-nitrogen-cooled <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> resonant pickup circuit, which are inductively coupled. Around 9 kHz, the configuration enhances the sensitivity of the system to 6-7 fT/√Hz. Meanwhile, the relatively large diameter of the coil <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> compensates the magnetometer's drawback of a small pickup area. We performed our experiments with a prepolarization field of 10 mT in a magnetically shielded room. The measurement field was 212.2 μT, corresponding to the Larmor frequency of 9.038 kHz. The compromise between the signal-to-noise ratio and the spatial resolution for our system was studied by recording one-dimensional MRI images of carrots under different gradient fields. For the sample of two carrot slices with center distance of 2.8 cm, a gradient field of 20 Hz/cm was suitable. Two-dimensional images were finally acquired. A HTS system for biological LF MRI detection by a tuned SQUID is demonstrated to be feasible.

Shrinkage and Color Change during Microwave Vacuum Drying of Carrot

Microwave vacuum drying (MVD) was applied to carrot slices and the radial shrinkage and changes in color and shape of its main tissues were evaluated. Tissue dimensions were obtained using computer vision; their visual color was quantified from Hunter Lab coordinates and their carotenoids contents were determined spectrophotometrically. The drying time varied from 24 to 42 min when the microwave power was changed from lower to higher values. MVD samples showed high rehydration capacity. The radial shrinkage values ranged from 36.2 ± 5.0 to 46.1 ± 4.6%, where higher values were seen in the core and under high microwave power. Circularity, solidity, and major and minor axes were shape descriptors of carrot slices that varied significantly during drying, changing from 0.58 to 44.3% of their initial values. In both fresh and dried products the cortex color exhibited superior color than that of the core. MVD incurred a significant whitening index and carotenoids losses.

High pressure carbon dioxide treatment for fresh-cut carrot slices

Abstract The effects of high pressure carbon dioxide (HPCD) treatment on natural microorganisms, indigenous enzyme activity, damage to cell membranes and hardness in fresh-cut carrot slices were investigated. 1.86 log 10 cycle reduction for aerobic bacteria (AB) and 1.25 for yeasts and molds (Y&M) were achieved at 5 MPa and 20 °C for 20 min. The residual activity ( RA ) of peroxidase (POD), polyphenol oxidase (PPO), and pectinmethylesterase (PME) exhibited initially increase and secondly decrease with treatment time and their minimum activity was 75.8%, 90.9% and 52.8% at 5 MPa and 20 C for 15 min, respectively. Membrane damage was evaluated by relative electrolyte leakage (REL) and malondialdehyde (MDA) content. HPCD caused a significant increase of REL in carrot slices and the REL of carrot slices treated at 5 MPa and 20 °C for 15 min was 5.7 times as much as that of the untreated, however, HPCD showed no effect on MDA content. The hardness was well retained after HPCD treatment and the largest loss was 7.9% at 5 MPa and 20 °C for 15 min. Industrial relevance Fresh-cut carrot slices are one of the most widely used products in prepared salads, and it required strict treatment conditions to protect its quality, especially to prevent microbial spoilage and enzymatic discoloration. HPCD is one promising novel non-thermal technique without compromising the flavor, taste and nutrition aspect of food. This study analyzed the effectiveness of HPCD as a method of preserving fresh-cut carrot slices, including inactivating natural microorganisms and enzymes which are crucial to quality control. Available data provided in this study will benefit the fresh-cut fruits and vegetables industry.

Modeling and Optimization of Mass Transfer during Osmosis Dehydration of Carrot Slices by Neural Networks and Genetic Algorithms

Osmotic dehydration, as a minimal processing method, has found increasingly wide prospects during the past few decades. This process involves mass transfer which is commonly modeled by applications of different procedures, mostly based on Fick's law. In this research, we approach the modeling process by first obtaining experimental measurement of carrot’s solid gain and water loss under different conditions of solution concentrations ( 20, 40 and 60% w/w), temperatures ( 40, 60 and 80°C) as well as time intervals (1-6h). Then two paradigms of artificial neural networks (ANN), feed forward neural networks (FFNN) and radial basis function neural networks (RBFNN) are applied and compared for modeling this process. Additionally, genetic algorithm is used to determine optimal conditions for osmotic dehydration.

Optimization of Osmotic Dehydration of Carrots under Atmospheric and Pulsed Microwave Vacuum Conditions

The osmotic dehydration of carrot slices was carried out by two methods: at atmospheric pressure and under pulsed microwave vacuum conditions. In the first part, 20 experiments were conducted using a central composite design (CCD) with sucrose concentration (23–57% w/w), solution temperature (29–71°C), and time of osmosis (6–74 min). The slice thickness of 3.5 mm and sample-to-solution ratio of 1:10 (w/w) was kept constant throughout all experiments. Numerical optimization was done for higher water loss (WL) and lower solids gain (SG) using developed correlations and optimum experimental conditions were found at 56.82% sucrose concentration, 29°C solution temperature, and 20-min osmosis time with water loss of 27.73% initial weight and 14.41% initial weight solids gain. In the second part of the investigation, osmotic dehydration of carrot samples under pulsed microwave–vacuum conditions was carried out at the optimum sucrose concentration and solution temperature obtained in the first part. The effect of microwave power and time on mass transfer was studied. The experiments were designed by using a CCD with two variables, viz. microwave time per minute (7 to 41 s) during initial 5 min of osmosis and total time of osmotic dehydration (7 to 41 min). During each experiment, vacuum at 6.66 kPa and microwave radiation of 1 W/g of osmotic solution and carrot slices at different pulsating levels were maintained during initial 5 min in the chamber and then osmotic dehydration was continued for different time intervals. Correlations were developed using a regression technique and the optimum conditions were found with 40.46% WL and 11.58% SG at microwave time per minute of 36 s during the initial 5 min and osmosis time of 12.48 min. In comparison to the osmotic dehydration of carrots at atmospheric pressure, the application of combined pulsed microwave vacuum during osmosis was found to increase WL.

Differentiation of Phytopathogenic agrobacterium spp.

Due to the difficulties in differentiation of phytopathogenic Agrobacterium spp. and lack of a standardized protocol, we carried out selection and evaluation of suitable methods based on the bacterial physiological, genetic and pathogenic properties. Strains of Agrobacterium tumefaciens, A. rhizogenes and A. vitis were differentiated using standard bacteriological and molecular methods. The biochemical and physiological tests confirmed authenticity of the strains. Two duplex PCR methods were conducted with four different primer pairs. In all strains, presence of plasmid virD2 and virC pathogenicity genes was detected. Chromosomal pehA gene was determined in A. vitis strain. Pathogenicity was confirmed on carrot slices and young plants of tomato and sunflower. Strains of A. tumefaciens and A. vitis were pathogenic on all test plants, while strain of A. rhizogenes induced characteristic symptoms only on carrot slices. The tests used in this study provided reliable discrimination between the three species and confirmed their identity as tumorigenic (Ti) Agrobacterium tumefaciens and A. vitis, and rhizogenic (Ri) A. rhizogenes.

Effect of processing parameters on physico-chemical and culinary quality of dried carrot slices

The investigation was carried out to evaluate the carrot (Daucus carota) cultivars, to optimize the pre-treatments, time and temperature combination for drying carrot slices and to assess the suitability of the dried product for culinary preparations. Among the 4 cultivars, ('PC-34', 'Sel-21', 'Ambala Local' and 'Nantes') the last one showed the best physico-chemical characteristics for dehydration. The dried carrot slices with highly desirable physico-chemical characteristics could be prepared from 4.5mm thick slices, blanched in water at 95°C for 4min followed by 2 stage phase drying at 90 ± 5°C for 2h and at 60 ± 5°C for 7h in a cross-flow hot air cabinet dryer. Dipping slices in 6% potassium metabisulphite solution prior to drying improved the rehydration ratio, colour, retention of ascorbic acid and carotenoids content of dried slices. The soup and curried product prepared from dried slices had highly acceptable sensory quality with 8.5 and 8.2 scores, respectively on a 9-point Hedonic scale.

Nutritional status, chewing function and vitamin deficiency in geriatric inpatients

The aim of this study was to investigate the correlation of vitamin and trace element deficiencies with the cognitive function, the Activities of Daily Living, the nutritional status and the chewing function in a population of geriatric hospitalized patients. Introduction All patients aged 70 years and over admitted to a geriatric department because of an acute disease were included into the study. Assessments of Activities of Daily Living (Barthel's Index), cognition (MMST) and chewing function (Carrot test) were done for every patient included. The nutritional status was assessed by the MNA, the BMI and by measurements of skinfold thickness. In addition to routine laboratory investigations the following laboratory investigations were done for every patient: Osteocalcin, Transketolase-Activity, Thiamin, Glutathion-Reductase-Activity, Niacin, Vitamin C, Vitamin A, Vitamin E and Selenium. Results Thirty-one patients (18 female and 13 male) were included into the study. No patient refused participation. The mean age was 78, 2 years. The mean BMI was 26.87 kg/m 2, the mean Barthel index was 60 points. The average score in the Mini-Mental-Status-Test was 20.7 points. Only 26% of the patients had a good nutritional status according to the Mini Nutritional Assessment (MNA). Forty-five percent of the patients had no own teeth. Eighty-one percent of the patients stated that they have no problems with chewing. However, objective testing revealed a higher prevalence of chewing dysfunction: 42% were not able to grind a carrot slice sufficiently in the carrot test. 55% of the patients had Vitamin C concentrations below the normal range, Selenium concentrations were below normal range in 52% of the patients investigated. Patients with a bad chewing function (index 6 in the carrot test) had a tendency to lower serum levels of Vitamin B1, Niacin, Vitamin C, Vitamin A and Selenium. There was a significant positive correlation of selenium levels with vitamin B 12 levels and lymphocyte count. The concentrations of Vitamin C and Vitamin A were significantly higher in patients taking many medications. No significant correlation was found between micronutrient deficiencies and BMI or the MNA score. Conclusions Elderly patients with acute illness have frequently micronutrient deficiencies, Vitamin C and Selenium being deficient in more than half of the patients. These deficiencies were not restricted to underweight patients: Patients with a normal BMI and even overweight patients showed micronutrient deficiencies. Geriatric and nutritional assessments alone are not suitable to identify the patients with these deficiencies.

The short-term effects of foot clipping as a nonlethal method of obtaining tissue samples from terrestrial gastropods

The most widely used method to obtain DNA for molecular analyses of terrestrial gastropods involves the death of the individual animal under study (Campbell, 2006). While the loss of a few individuals may not be important for the viability of populations of abundant species, this is not the case for rare or threatened species. Therefore, several recent studies have obtained tissue samples from terrestrial gastropods using an apparently nonlethal foot-clipping method. Most of the previous studies using foot clipping have examined endangered or localized gastropod species. Thacker & Hadfield (2000) and Holland & Hadfield (2002, 2004, 2007) studied the highly endangered Achatinella genus of Hawaiian tree snails, while Anderson (2007) used the same method to obtain tissue samples from the very localized polygyrid Euchemotrema hubrichti in southwestern Illinois. Wade & Mordan (2000) and Wade, Mordan & Naggs (2006) conducted phylogenetic analyses of pulmonate snails using pieces of tissue clipped from the foot of both common and rare species. It is likely that continuing advances in conservation genetics, combined with continuing degradation of the conservation status of many gastropods, will increase the need for molecular information from endangered species. Quantitative information about the effects of foot clipping would therefore be helpful to assess whether the method is appropriate for use and what its limitations might be. None of the previous studies reported experimental data on the behaviour or survival of clipped snails, although Thacker & Hadfield (2000) and Holland & Hadfield (2007) stated that no deaths followed the procedure in laboratory populations. In order to investigate the effects of clipping on the behaviour and survival of land snails, we conducted a randomized experiment on the discid Anguispira cumberlandiana (Lea, 1840), a nonthreatened species that is a close relative of the endangered Anguispira picta (Clapp, 1920). We gathered live A. cumberlandiana snails from the field by searching a limestone outcrop in Shakerag Hollow, Sewanee, Franklin County, TN, USA (location in decimal degrees: 35.226944, 285.909722, 365 m elevation). We assigned 23 snails to two groups (treatment and control), using a random numbers table to randomize assignments. We then placed all snails on individual pieces of parafilm. Snails at this point were withdrawn into their shells. We waited for the snails to emerge, which took from 2 min to 2 h. When they emerged, snails assigned to the treatment group (n 1⁄4 11 snails) had a piece of tissue about 1 mm sliced from the posterior tip of their foot with a sterile scalpel blade. The tissue sample was then immediately stored at 2208C until DNA was extracted. Snails that had been assigned to the control group (n 1⁄4 12 snails) were not clipped, but received the same handling as the treatment snails. After clipping and/or handling, all snails were replaced in cleaned, individual glass containers with a moist tissue paper and slices of carrot and cucumber. The jars were covered with perforated parafilm and stored on a laboratory bench that received indirect natural light and sporadic artificial light from laboratory overhead lights. We made behavioural observations of the snails after 6 h and 18 h, then at approximately daily intervals for 2 weeks. At each observation time we noted whether each snail was alive and, if so, whether it was active (i.e. the head and/or foot emerged from the shell) or inactive (snail withdrawn into shell). No snails died over the 2-week period of the experiment. The behaviour of clipped snails differed from unclipped snails at 6 h after the procedure, but thereafter we did not detect differences in behaviour (Fig. 1). Specifically, the portion of snails that were active was significantly lower for clipped than for unclipped snails after 6 h (Fisher’s exact test, P 1⁄4 0.012), but this difference was no longer significant at 18 h after clipping (Fisher’s exact test, P 1⁄4 0.68) or thereafter (Fisher’s exact test, P . 0.2 for all times). Our results accord with the lack of mortality reported by Thacker & Hadfield (2000) in clipped Achatinella. However, it appears that the foot-clipping procedure caused a short-term change in behaviour of the snails, with clipped snails remaining withdrawn in their shells for the first half-day after the procedure. Thereafter, there did not appear to be any differences in the behaviours that we observed. The observed short-term change in behaviour could result in loss of feeding opportunity, or even increase risk of predation if withdrawn snails are left in exposed areas. However, these indirect negative fitness effects are speculative. Our findings are also consistent with the results of clipping experiments in bivalves. Berg et al. (1995) examined the effects of mantle clipping in freshwater mussels,

Kinetic Models of β-Carotene Degradation During Air Drying of Carrots

The objective of this study was to determine the kinetic parameters of models that describe the joint influence of temperature and moisture content on the thermal degradation of β-carotene in a drying process of carrots. Two models were used: a first-order decay model with an Arrhenius and a polynomial dependency on temperature and water content, respectively, and a decay model with a WLF dependency of the decimal reduction time on glass transition temperature (Tg), with the Gordon and Taylor equation describing the influence of moisture content on Tg. Carrots were dehydrated in a cabinet air dryer at 50, 60, 70, and 80°C. Carrot samples were drawn at 20-min intervals and analyzed for moisture and β-carotene content. The parameters of the two models were estimated by nonlinear regression. In addition, the models were evaluated by comparing their predictions and experimental data during drying at 80°C of carrot slices with thickness of 3, 6, and 9 mm. Both models were found suitable for modeling the β-carotene degradation, though the lower sum of squares of residuals (SSQ) of the Tg approach model and the similar WLF parameters calculated at different drying air temperatures demonstrated the higher predictive ability of the Tg model over the more common empirical dependence model.

MODELING WITH SHRINKAGE DURING THE VACUUM DRYING OF CARROT (DAUCUS CAROTA)

ABSTRACT The drying kinetics of carrot slices have been measured in a vacuum chamber, the experiments were carried out at various temperatures (50, 60 and 70C) under conditions of low pressures (5, 15 and 25 kPa). It was observed that the best values of diffusivity were obtained at the major temperature and low pressure for the samples pretreated by freezing. The experimental data were modeled using Fick's diffusional model in terms of moisture concentration with and without shrinkage. It is found that the calculated values of effective diffusivity for the drying process considering no shrinkage were greater than those for the drying process considering shrinkage. PRACTICAL APPLICATIONS Vacuum drying is the effective method of removal of moisture from fruits and vegetables. In this research, the experimental study and modeling on drying kinetics during the vacuum drying of carrot was studied. Also, the effect of the pretreatments, pressure and temperature on the vacuum drying kinetics was determined. A diffusion model based on Fick's second law of diffusion with and without shrinkage was used to describe the transport mechanism in the falling drying rate regions. The results from this research can be used asreference for vacuum drying and modeling kinetics drying of carrot and vegetables.

Qualidade de mandioquinha-salsa minimamente processada e armazenada sob atmosfera modificada

O objetivo deste trabalho foi verificar o efeito da atmosfera modificada, passiva e ativa, sobre a conservação de mandioquinha-salsa minimamente processada da cultivar 'Amarela de Senador Amaral', adquirida de lavoura comercial do Município de Lavras, Minas Gerais (MG). As raízes foram selecionadas, lavadas com detergente neutro e enxaguadas em água corrente. Em seguida, foram imersas em solução de hipoclorito de sódio 300mg L-1, por 15 minutos, e secas em temperatura ambiente. As raízes foram descascadas e cortadas em fatias de aproximadamente 1cm de espessura, imersas em solução de hipoclorito de sódio 50mg L-1, por 10 minutos, drenadas em peneiras plásticas e embaladas. As bandejas contendo as fatias de mandioquinha-salsa foram armazenadas em câmara fria (5±1°C e 98% UR) por 15 dias. As seguintes análises foram realizadas a cada três dias: pH, acidez titulável, sólidos solúveis totais, firmeza, valores L* e b*, amido e avaliação sensorial (aparência e cor). O delineamento experimental foi inteiramente ao acaso (DIC), em esquema fatorial 3 x 6, sendo três tipos de atmosferas (passiva; ativa com injeção inicial das misturas: 2% O2 + 10% CO2 e 5% O2 + 5% CO2) e seis tempos de armazenamento (0, 3, 6, 9, 12 e 15 dias), com três repetições. Os valores médios de pH, acidez titulável, sólidos solúveis e firmeza encontrados neste trabalho foram 6,79, 0,13% de ácido málico, 4,04°Brix e 5,17N, respectivamente. A atmosfera modificada ativa (5% de O2 + 5% CO2) determinou maior valor L* às mandioquinhas-salsa minimamente processadas no sexto e no décimo segundo dia de armazenamento, quando comparada com a atmosfera (2% de O2 e 10% CO2). A atmosfera modificada ativa com 5% O2 + 5% CO2 determinou maiores valor b* e teores de amido às fatias de mandioquinha-salsa em comparação com as outras atmosferas. Conclui-se que a atmosfera modificada passiva, aliada à refrigeração e a boas práticas de fabricação, é suficiente para prolongar a vida útil de mandioquinhas-salsa minimamente processadas, preservando seus atributos de qualidade. Diante da avaliação sensorial realizada, a aparência e a cor das fatias de mandioquinha-salsa mantiveram-se aceitáveis para o consumo até o final do período de armazenamento.

Vacuum frying reduces oil uptake and improves the quality parameters of carrot crisps

Recent consumer trends towards healthier and low fat products have had a significant impact on the snack industry. The objective of this study was to examine the most important quality parameters of vacuum and atmospheric fried carrot slices in order to identify the specific advantages of vacuum technology. Said parameters include oil uptake, colour changes, and trans a and b-carotene degradation. Equivalent thermal driving forces were used (DT =6 0C and 80 C) to compare the processes, maintaining a constant difference in temperature between the oil and the boiling point of water at the working pressure. The results showed that vacuum frying can reduce oil content by nearly 50% (d.b.) and preserve approximately 90% of trans a-carotene and 86% of trans b-carotene. This process also allowed for the raw carrot colour to be preserved, which was reflected by good correlations between a* and trans b-carotene content, b* and trans a-carotene content, and hue and total carotenoid content.

Computer Simulation of Atmospheric Freeze Drying of Carrot Slices in a Fluidized Bed

Nam and Song's model, which describes the first stage of vacuum freeze drying, is adapted to atmospheric pressure conditions in a pulsating fluidized bed, discretizing the differential equations by finite-difference according to the implicit scheme. The generated algebraic systems of equations are solved by the tridiagonal matrix algorithm (TDMA). The effect of the variable time step on computation time is analyzed. The effect of particle size reduction, bed temperature increase, and the incorporation of infrared radiation made it possible to reduce drying times. Comparison with experimental values of the first stage of the freeze drying of carrot slices and the values calculated from the model showed a maximum mean quadratic error of 0.09.

Drying of carrot slices using infrared radiation

SummaryCarrot slices were dried from initial moisture content of 8.52 kg water kg−1 dry matter to 0.11 kg water kg−1 dry matter by infrared dryer. Experiments were conducted using three levels of infrared power (300, 400 and 500 W) and at air velocities (1.0, 1.5 and 2.0 m s−1). The effects of process variables on the drying kinetics of carrot, drying time, specific energy consumption and quality parameters of dried carrot (shrinkage, rehydration ratio and colour) were investigated. The drying time at infrared power of 300, 400 and 500 W was 252 and 277 min, 205 and 236 min, and 145 and 155 min at air velocities of 1.0 and 2.0 m s−1, respectively. The drying rate increased with increasing infrared power. The specific energy consumption values varied between 12.22 and 14.58 MJ kg−1‐evaporated water for all the drying conditions. Shrinkage, rehydration ratio and colour parameters were found to be affected by process variables.

Experimental and theoretical analysis of drying carrots

The drying characteristics of carrots are investigated experimentally and theoretically for different drying conditions. Carrot slices with three different thicknesses are used. Initially, sorption isotherms of the dried carrot slices are determined for different temperatures and equilibrium relative himidity (e.r.h.). Experiments are conducted for drying air temperatures of 35, 45 and 55°C, mean velocities of 0.2, 0.4 and 0.6 m/s and, relative humidity values of 40, 55 and 70%. In the covered ranges, the values of the effective moisture diffusivity, D eff , are obtained from the Fick's diffusion model varying from 1.257 × 10 −9 to 2.200 × 10 −9. The effects of the governing drying parameters on the total drying time are determined. A mathematical model based on the Fickian model was established to describe the mass transfer in a carrot slice. Comparison of experimental and calculated results shows good agreement.