Effects of Pulsed Electric Fields on Cabernet Sauvignon Grape Berries and on the Characteristics of Wines

The treatment of Cabernet Sauvignon red grapes by pulsed electric fields (PEFs) is performed prior to vinification in order to enhance the extraction of polyphenols. PEF treatments of the longest duration and of the highest energy (E?= 0.7 kV/cm, t _PEF?=?200 ms, W?=?31 Wh/kg) changed the structure of grape skins and produced a wine that was richer in tannins (34 %), while treatment of the highest strength (E?=?4 kV/cm, t _PEF?=?1 ms, W =?4 Wh/kg) altered the visual appearance of phenolic compounds in the skins and led to greater extraction of the anthocyanins (19 %). The PEF treatments caused the depolymerization of skin tannins, improving the diffusion of these decondensed tannins which are smaller. The PEF treatment of longest duration and of the highest energy had more impact on the parietal tannins and the cell walls of the skins while treatment of the highest strength modified more the vacuolar tannins. Changes in the operating parameters of the PEF treatment (E?=?0.7 to 4 kV/cm, t _PEF?=?1 to 200 ms, W?=?4 to 31 Wh/kg) did not affect alcohol content, total acidity nor volatile acidity in finished wines compared to the values of the control wine, but seemed to cause a slight increase in pH (1–2 %).     

Alternative Pressing/Ultrafiltration Process for Sugar Beet Valorization: Impact of Pulsed Electric Field and Cossettes Preheating on the Qualitative Characteristics of Juices

Alternative process of sugar beet transformation is investigated by tuning experimental conditions. A three-step process has been set-up: (1) sugar beet cossettes pretreatment by pulsed electric field (PEF) and (or) short preheating to different temperatures; (2) extraction of juice from pre-treated cossettes by pressing; and (3) purification of the expressed juice by ultrafiltration. The PEF treatment was applied to cold (10 °C) and preheated (to 20, 50, 60, 70, and 80 °C) sugar beet cossettes with intensity of E?=?600 V cm^?1 using rectangular monopolar pulses of 100 μs during t _PEF?=?5–20 ms. Experiments were performed with cossettes of three sizes. Control experiments were done without PEF treatment using cold (10 °C) and preheated (to 20–80 °C) cossettes. PEF-treated and (or) preheated cossettes were pressed at 5 bars during 15 min. Afterward, expressed juices obtained from the PEF-treated cossettes at 20 °C and from the untreated ones at 80 °C were purified by dead-end ultrafiltration with stirring (500 rpm) at the temperature of 20 °C by using polyethersulfone membrane with MWCO of 30 kDa. Application of PEF (E?=?600 V cm^?1, t _PEF?=?10 ms, T?=?20 °C) with following pressing of cossettes at 5 bars during 15 min permits to obtain the juice yield Y?=?66,5 %, which is equivalent to that obtained from cossettes preheated to 80 °C and untreated electrically (Y?=?64 %). The energy consumption of cold PEF treatment (≈2–3 Wh/kg) is very attractive as compared to preheating at high temperatures (≈138–194 Wh/kg). Combination of thermal and electrical pretreatments leads to additional softening of sugar beet tissue and to a slightly higher (on 5–10 %) juice yield, but the electroporation of preheated cossettes is more energetically costly. The raw juice expressed from PEF-treated cossettes at 20 °C has higher purity (93.5 %) than juices expressed at 50 °C (92.9 %) and at 80 °C (92.3 %). The temperature increasing from 20 to 80 °C results in a higher juice coloration (5680 IU at 20 °C and 7820 IU at 80 °C) and leads to a higher (on about 35 %) colloids concentration in the expressed juice. The filtrate obtained from the juice expressed at 20 °C with PEF treatment has a higher purity (96 %) than the filtrate obtained from the juice expressed at 80 °C (95.3 %) and its coloration is considerably lower (330 IU versus 1930 IU). In addition, the quantity of proteins and colloids in the filtrate of juice expressed at 20 °C is lower than that in the filtrate of juice expressed at 80 °C     

Modelling of Soy Sauce Desalting by Electrodialysis

In this work, the main features of electrodialytic (ED) desalting of microfiltered samples of a traditional soy sauce under constant electric current in the range of 1.25 to 6.5 A were quite well reconstructed using a mathematical model based on the Nernst–Planck equation. Amino nitrogen migration was characterised by a small effective transport number (t _AN?=?0.070?±?0.01), resulting in an average loss in amino nitrogen of about 30% whatever the electric current tested. The sodium chloride transport number (t _B?=?0.969?±?0.05) and diffusion rate (L _B?≈?0), as well as the effective membrane surface area, essentially coincided with those previously established when dealing with concentrated model brines. On the contrary, there was a significant diversity in the water transport number (t _W?=?8.3?±?0.1) and diffusion rate [L _W?=?(6.9?±?0.2)?×?10^?5 mol m^?2 s^?1?bar^?1], as well as in the anion- and cation-exchange membrane resistances (R _a?=?R _c?≈?0.04 Ω). The experimental procedure and mathematical model described in this work may be recommended not only to optimise the ED desalination of soy sauce but also to generate a first-cut design for ED desalting of other natural seasonings.     

Impact of Electric Pulse Treatment on Selective Extraction of Intracellular Compounds from Saccharomyces cerevisiae Yeasts

Treatments by high-voltage electrical discharges (HVED, needle-plate electrode geometry, U?=?40 kV, t _p?≈?0.5 μs) and pulsed electric field (PEF, plate–plate electrode geometry, E?=?5–40 kV/cm, t _p?≈?8.3 μs) were evaluated as tools for selective extraction of different intracellular components from the wine Saccharomyces cerevisiae (bayanus) yeasts in a 0.5% (w/w) aqueous suspension. The pulses in the form of damped oscillations and exponential decay were applied in HVED and PEF modes of treatment, respectively. The extraction efficiency results obtained using HVED and PEF techniques were compared with those for high-pressure homogenization technique. The HVED and PEF treatments always resulted in incomplete damage of yeast cells, though efficiency of HVED was higher than that of PEF. The high selectivity of extraction of ionic substances, proteins, and nucleic acids was demonstrated; e.g., electric pulse treatments at E?=?40 kV/cm and N?=?500 allowed extraction of ≈80% and ≈70% of ionic substances, ≈4% and ≈1% of proteins and ≈30% and ≈16% of nucleic acids in cases of HVED and PEF modes, respectively.     

Effects of Pulsed Electric Field Processing on Quality Characteristics and Microbial Inactivation of Soymilk

Effects of pulsed electric fields (PEF) on quality characteristics and microbial inactivation of soymilk were studied with different PEF parameters. PEF did not affect significantly the values of pH, “a” (an indicator of redness ranging from “?a” to “+a”, ?a?=?green, +a?=?red) and electric conductivity. The values of “L” (white if “L”?=?100, black if “L”?=?0) increased slightly, whereas values of viscosity and “b” (an indicator of yellowness ranging from “?b” to “+b”, ?b?=?blue, +b?=?yellow) decreased slightly as PEF time increased from 0 to 547 μs. Cysteine, tyrosine, phenylalanine, and serine reduced with the increase of PEF time. The relative activities of soybean lipoxygenase (SLOX) decreased with PEF time increasing from 0 to 1,036 μs. When PEF time and strength increased, the inactivation of Escherichia coli and Staphylococus aureus increased significantly (p?<?0.05), achieving a maximum of 5.20 and 3.51 log₁₀ cycles reduction at PEF time 547 μs and pulsed electric strength 40 kV/cm, respectively. The inactivation of E. coli, S. aureus, and SLOX as a function PEF time followed Weibull distribution. This study demonstrated that PEF could inactivate efficiently E. coli, S. aureus, and SLOX without affecting the quality characteristics of soymilk. Thus, this technique could be an advantageous alternative to heat treatment for pasteurization of soymilk.     

Pulsed electric field (PEF) technology for microbial inactivation in low-alcohol red wine

The decontamination of spoilage-related microbes in low-alcohol red wine was performed using a serial multiple electrode pulsed electric field (PEF) treatment system. The system consisted of seven electrodes connected in series, and it has been designed to produce square-wave high-voltage pulses of 1 μs duration at various electric field strengths and frequencies for decontamination. The initial counts of aerobic bacteria, yeast and lactic acid bacteria (spoilage-associated microbes) in the wine were 5.56, 5.61 and 5.22 log CFU/mL, respectively. The pattern of decontamination of the spoilage microorganisms followed first-order kinetics and the decontamination effect increased as the field strength and frequency increases. D_Hz and D_PEF values were inversely related to the electric field strength of the PEF treatment. The yeast exhibited relatively low D_PEF-value than the aerobic and lactic acid bacteria. The lowest Z_PEF-value was observed for the lactic acid bacteria (24.6 kV/cm) among the spoilage microbes.     

Pilot scale inulin extraction from chicory roots assisted by pulsed electric fields

A pilot study for the pulsed electric fields (PEF) assisted countercurrent diffusion of inulin from chicory roots is presented. The influence of PEF parameters (electric field intensity E = 600 V cm^?1, treatment duration t_PEF = 10–50 ms) and diffusion temperature (varied between 30 and 80 °C) on soluble matter extraction kinetics, inulin content of juice, and pulp exhaustion are investigated. The draft (liquid to solid mass ratio) was fixed at 140%, similar to the industrial conditions. PEF treatment facilitates extraction of inulin at conventional diffusion temperature (70–80 °C), and diffusion temperature can even be reduced by 10–15 °C with comparable juice inulin concentration. Less energy consumption can be achieved by reducing PEF treatment duration to 10 ms, which is observed sufficient for effective extraction.     

Molecularly Imprinted Layer-Coated Silica Gel Particles for Selective Solid-Phase Extraction of Pefloxacin and Enrofloxacin from Milk Samples

This study describes the synthesis of a molecularly imprinted polymer (MIP) as a novel solid-phase extraction adsorbent. The MIP consisted of pefloxacin (PEF) as a template, methacrylic acid (MAA) as a functional monomer, and silica gel particles as a support. The MIP was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and static adsorption. The MIP allowed the selective extraction of the fluoroquinolones PEF and enrofloxacin (ENR) and the simultaneous elimination of interfering components from milk matrices. Good linearity was obtained in a range of 2.5–500 ng?mL^?1, with correlation coefficients (R ²) >0.999. The average recovery rates of PEF and ENR ranged from 92.04 to 98.31 %, and the detection limits were 0.8–1.5 ng?mL^?1. This work provides a sensitive and selective tool for the detection of PEF and ENR residues in milk and potentially in other foods.     

Pulsed Electric Field Assisted Pressure Extraction and Solvent Extraction from Mushroom (Agaricus Bisporus)

This work compares the efficiency of extraction and stability of extracts from mushroom (Agaricus bisporus) for different methods of extraction: pressure extraction (PE), pressure extraction assisted by pulsed electric field (PE?+?PEF), hot water extraction (WE; temperature, T?=?343 K, time, t?=?2 h), ethanol extraction (EE; T?=?298 K, t?=?24 h), and supplementary ethanol extraction from cakes of slices (SEE; T?=?298 K, t?=?24 h). PE was done at room temperature and 5 bar pressure (p). PEF treatment was done using bipolar near-rectangular pulse protocol. The traditional hot WE (T?=?343 K, t?=?2 h) gave the relatively high contents of proteins, total polyphenols and polysaccharides; however, the extracts were cloudy and their colloid stability was low. The extracts obtained using EE method were also cloudy and unstable. The sizes of particles in extracts, produced by WE and EE methods, were estimated as?≈?0.25 and?≈?5 μm, respectively. From the other side, the extracts, produced by PE and PE?+?PEF methods, were clear and their colloid stability was high. Moreover, both PE and PE?+?PEF methods allowed selective separation of different components. The PE?+?PEF method gave higher nucleic acid/proteins ratio as compared with that of PE method. Moreover, PE?+?PEF allowed production of mushroom extracts with high contents of fresh-like proteins and polysaccharides. Application of the EE method supplementary to the PE or PE?+?PEF techniques allowed for an effective extraction of the total polyphenols that was comparable with the efficiency of the WE method.     

Sensitive Determination of Bromate in Water Samples by Capillary Electrophoresis Coupled with Electromembrane Extraction

Electromembrane extraction (EME) as a novel sample preparation technique was firstly applied for the purification and enrichment of bromate (BrO₃ ^?) in drinking water prior to capillary zone electrophoresis with capacitively coupled contactless conductivity detection (CZE-C⁴D). BrO₃ ^?, as the primary disinfection by-product of ozonation, could be well separated with the major inorganic anions coexisting in water samples using a 300 mmol L^?1 acetic acid solution as the running buffer. Under the optimum conditions, the calibration curve showed good linearity (r ²?=?0.996), and the limit of detection was down to 0.12 ng mL^?1 with the enrichment factor at 267. The relative standard deviation (RSD) values for peak area and migration time at a spiked concentration of 10 ng mL^?1 of bromate were below 8.8 and 2.5 %, respectively. This proposed EME-CZE-C⁴D method has been successfully applied to analyze bottled drinking water and tap water samples with recoveries in the range of 85~98 %, providing an alternative to the determination of bromate in drinking water.     

A mathematical model for moisture movement during continous and intermittent drying of <Emphasis Type="Italic">Eucalyptus saligna</Emphasis>

A modified diffusion-based mathematical model is proposed to describe the moisture movement during continuous and intermittent drying of Eucalyptus saligna. This model includes the temperature change, the surface drying coefficient (β _n ) and 2 diffusion coefficients [from green to FSP (D _f ) and from FSP to dry condition (D _o )] as important parameters. The final model expression obtained was M?=?exp (??25 β _n ² D _t /l²) with the β _n used was 1.5807 kg m^?2 s^?1, the D _f was 2.26?×?10^?11 m² s^?1, and the D _o was 5.85?×?10^?12 m² s^?1. The range of temperature change between heating and non-heating phases in the intermittent drying regimes was from 24.9 to 31.8 °C. The R² values obtained when the model was fitted into the drying data of different intermittent regimes ranged from 71.5 to 85.9%. The R² value was 87.4% when the model was fitted into continuous trial data. The high values of R² indicate that the model can be used to understand the moisture reduction both in intermittent and continuous regimes.     

Dehydrofreezing of Apple Fruits: Freezing Profiles,Freezing Characteristics,and Texture Variation

The present study deals with the dehydrofreezing of apples. Fresh samples (700 % db) and samples dehydrated up to different water contents (200, 100, and 30 % db) were frozen at high practical freezing rate (PFR⁺) and low practical freezing rate (PFR^?). The effects of water content (W) and practical freezing rate (PFR) were investigated in terms of freezing characteristics: initial freezing temperature (IFT), practical freezing time (PFT), specific freezing time (SFT), thaw exudate water (TEW), and texture (maximum puncture force as index of firmness). Only high W samples (700 and 200 % db) had a significant impact of PFR in terms of PFT, SFT, and TEW. IFT decreased sharply with the decrease in the sample W. PFT greatly depended on PFR for fresh apples. PFT varied from 86 to 329 min for fresh apples at PFR⁺ and PFR^?, respectively, whereas it was lower than 32 min for samples with W?=?30 % db. SFT decreased, equally, with sample W decrease. The TEW of fresh frozen samples, during thawing, was approximately 12 g/100 g water for low PFR (PFR^?), whereas it was lower than 3 g/100 g water for samples with W?=?200 % db at the same PFR. Moreover, the impact of PFR on TEW was significant and very important for high W samples. Finally, the firmness increased when W decreased for both PFR⁺ and PFR^?. Nevertheless, an insignificant impact of PFR on apple firmness was found. Thus, partial removal of water constitutes a promising solution to prevent the negative impacts of freezing on apple fruit firmness.     

Synergistic Processing of Skim Milk with High Pressure Nitrous Oxide,Heat, Nisin,and Lysozyme to Inactivate Vegetative and Spore-Forming Bacteria

Individual and combined effects of high pressure nitrous oxide (HPN₂O), heat, and antimicrobials on the inactivation of Escherichia coli, Listeria innocua, and Bacillus atrophaeus endospores in milk were all evaluated after 20-min treatments. Stand-alone milk treatments with HPN₂O (15.2 MPa), heat (45 and 65 °C), or nisin (50 and 150 IU mL^?1) resulted in log₁₀ reductions ranging only from 0.1 to 2.1 for E. coli and L. innocua. Combining HPN₂O (15.2 MPa) with heat (65 °C) inactivated 6.0 and 5.1 log₁₀ in the vegetative bacteria, respectively. Similarly, reductions of 5.9 and ≥ 6.0 log₁₀ of respective E. coli and L. innocua cells in milk were achieved through a combination of HPN₂O (15.2 MPa), heat (65 °C), and nisin (150 IU mL^?1). A 2.5 log₁₀ cycle inactivation of spores was obtained by HPN₂O, nisin (at both 50 and 150 IU mL^?1), and lysozyme (50 μg mL^?1) at 85 °C. Combining these processing techniques resulted in significantly greater microbial inactivation (p < 0.05) than the sum of individual reductions from each treatment alone, indicating synergistic effects. HPN₂O irrespective of processing temperatures did not cause any occurrence of sub-lethally injured cells or disruption in colloidal stability of milk at 65 and 85 °C (p ≥ 0.05). Color and pH changes in milk following the most demanding treatment conditions were minimal.     

Cysteamine-CdTe Quantum Dots Electrochemically Synthesized as Fluorescence Probe for Resveratrol

This work proposes a fluorescent probe based on CdTe quantum dots (QDs) for the determination of resveratrol in wine samples. The synthesis of cysteamine (CA) capped CdTe QD was carried out in a one-pot eco-friendly process, resorting to the electrochemical reduction of metallic tellurium powder in a graphite macroelectrode (cavity cell). The reduced species of tellurium (Te^2? and Te₂^2?) migrated to an intermediate compartment of the electrochemical cell and in the presence of a cadmium salt and organic stabilizing agent (CA), forming the colloidal dispersion of CdTe in a single step. Under optimum synthesis conditions, the fluorescence intensity of the prepared nanoparticles varied linearly with the resveratrol concentration in the range from 3.25 to 75 μg L^?1 (R²?=?0.9984), with a detection limit of 0.97 μg L^?1 and RSD of 3.7% (5.0 μg L^?1 resveratrol, n?=?10). The method was successfully applied to the resveratrol determination in wines, with recoveries from 97.8 to 112.4%. Student’s t test was applied and no statistically significant difference was observed between the two methods (HPLC and proposed), with a confidence level of 95% (t_tabulated?=?2.45 and t_calculated?=?0.38). The resveratrol determination method, by using CdTe-CA QDs as fluorescence probe, was simple, rapid, inexpensive, and sensitive.     

Ultrasonic-Assisted Extraction of α-Tocopherol Antioxidants from the Fronds of Elaeis guineensis Jacq.: Optimization, Kinetics, and Thermodynamic Studies

This article presents the first report on the extraction and quantification of α-tocopherol from the fronds of the oil palm (Elaeis guineensis Jacq). In this study, the optimization, kinetic, and thermodynamic data of α-tocopherol extraction by sonication are presented. Response surface methodology coupled with central composite design was used to optimize the experimental conditions for α-tocopherol extraction. Three independent variables, namely sample/solvent ratio (1:20–1:40 g/ml), extraction temperature (30–50 °C), and extraction time (20–50 min) were studied. For optimum conditions of 39.31 °C (~40 °C), 50 min, and 1:23.63 g/mL (~1:20 g/mL), total tocols and α-tocopherol optimal concentrations were 346.49 μg/g oil palm fronds (OPFs) by dry weight (DW) and 28.41 μg/g OPF DW, respectively. The effects of extraction temperature and tocol concentrations on the extraction kinetics and thermodynamic parameters were also studied. From the mass transfer rate equation, the kinetic and thermodynamic data obtained from the ultrasonic-assisted extraction (UAE) of α-tocopherol from OPF were activation energy, E _a (104.6 kJ mol^?1), UAE rate constant, k (6.886?×?10^?3 min^?1), ΔH (+0.818 kJ mol^?1), ΔS (+27.22 J mol^?1 K^?1), and ΔG (?8.52 J mol^?1). According to this study, the UAE of α-tocopherol from OPF is endothermic, irreversible, and spontaneous.     

Effect of thermosonication,pulsed electric field and their combination on inactivation of Listeria innocua in milk

The impact of thermosonication (TS) and pulsed electric field (PEF), individually and combined, on the survival of Listeria innocua 11288 (NCTC) in milk was investigated. TS (400 W, 160 s) without pre-heating reduced L. innocua by 1.2 log₁₀ cfu mL^?1, while shorter treatment times produced negligible inactivation, suggesting TS to be a hurdle rather than an effective standalone treatment. PEF (30 and 40 kV cm^?1, 50 μs) at 10 °C caused a reduction of L. innocua of 1.1 and 3.3 log cycles, respectively. The highest field strength (40 kV cm^?1) combined with TS (80 s) led to 6.8 log₁₀ cfu mL^?1 inactivation. Milk pre-heated to 55 °C (over 60 s) prior to TS followed by PEF (30 and 40 kV cm^?1) showed inactivation between 4.5 and 6.9 log₁₀ cfu mL^?1, the latter being comparable (P > 0.05) with thermal pasteurisation. The data indicate that TS followed by PEF represents a valid alternative for L. innocua inactivation in milk.     

Comparison of the performances of different fermentation strategies on cell growth and bacteriocin production by Lactobacillus curvatus CWBI‐B28

The dynamics of cell growth and bacteriocin production by Lactobacillus curvatus CWBI‐B28 in modified De Man/Rogosa/Sharp (mMRS) broth with various concentrations of glucose and complex nitrogen source (CNS; peptone, yeast extract and meat extract) was investigated in flask fermentations and in a laboratory fermentor using batch and fed‐batch cultivations. In fed‐batch fermentation the rate of feeding of the reactor with the substrates was either maintained constant (0.12 L h^?1) or varied exponentially as a function of time. The results showed that both cell growth and bacteriocin activity were influenced by changes in the concentrations of glucose and CNS. Optimal growth and bacteriocin activity were obtained in mMRS broth containing 40 g L^?1 glucose and 40 g L^?1 CNS (mMRS_40/40). A bacteriocin titre of 4266 AU mL^?1 and a cell count of 8.7 log colony‐forming units (cfu) mL^?1 were recorded when this medium was used for cultivation. In batch fermentation using the same medium, a higher cell count (9.5 log cfu mL^?1) and twice as much bacteriocin as in flask fermentation were produced. The highest bacteriocin titre (8533 AU mL^?1) was obtained with fed‐batch fermentation at an exponentially varying rate of feeding. Bacteriocin activity and cell dry mass did not always correlate. Copyright © 2007 Society of Chemical Industry     

Selective Determination of Selenium in Garlic, Mushroom and Water Samples by Chemically Modified Mesoporous Silica Solid Phase Coupled with ICP-OES

A selective sorbent for solid phase extraction (SPE), based on a chemically modified mesoporous silica (SBA-15), followed by inductively coupled plasma-optical emission spectrometry was used for extraction, preconcentration, and determination of selenium in water and food samples. The main parameters of SPE including pH, amount of mesoporous (solid phase), concentration of the eluent (desorption solvent), and equilibrium time were optimized by using a fractional central composite design (f-CCD). The optimum conditions were found to be 3.2 for pH, 21 mg for amount of the mesoporous, 1 mol l^?1 for eluent concentration, and 9 min for equilibrium time. Under the optimal conditions, the limit of detection (LOD) was 2.56 μg l^?1. The linear dynamic range (LDR) was 5–1,000 μg l^?1 with determination coefficient (R ²) of 0.999. Relative standard deviation (C?=?400 μg l^?1, n?=?5) was 3.84 %. The enrichment factor was 20. The maximum sorption capacity of the modified SBA-15 was 15 mg g^?1. The sorbent presented good stability, reusability, high adsorption capacity, and fast rate of equilibrium for sorption/desorption of selenium (IV) ions.     

A Miniaturized Preconcentration Method Based on Dispersive Liquid–Liquid Microextraction for the Spectrophotometric Determination of Aziridine in Food Simulants

In this work a simple, rapid and sensitive method using dispersive liquid–liquid microextraction (DLLME) combined with UV–Vis spectrophotometry has been developed for the preconcentration and determination of trace amounts of aziridine in food simulants. The method is based on derivatization of aziridine with Folin's reagent (1,2-naphthoquione-4-sulphonic acid) and extraction of color product using DLLME technique. Some important parameters, such as reaction conditions, and type and volume of extraction solvent and disperser solvent were studied and optimized. Under optimum conditions, a linear calibration curve in the range of 2.0–350 ng mL^?1 of aziridine was obtained. Detection limit based on 3S_b was 1.0 ng mL^?1, and the relative standard deviation for 50 ng mL^?1 of aziridine was 2.49c (n?=?7). The proposed method was applied for the determination of aziridine in food simulants.     

Changes in Chemical and Microbial Qualities of Dried Apricots Containing Sulphur Dioxide at Different Levels During Storage

Effects of different sulphur dioxide (SO₂) concentrations (188, 452, 791, 1,034, 1,236, 2,899 and 3,864 mg SO₂ kg^?1) and storage temperatures (5, 10, 20 and 30 °C) on the physical, chemical and microbial qualities of sulphited-dried apricots (SDAs) were evaluated. Analysis of kinetic data suggested first-order models for losses of moisture and SO₂ and formation of brown colour. Strong correlations were found between SO₂ concentrations and moisture loss constants (r?=??0.943), and brown colour values (r?=?0.949). β-carotene contents in SDA samples ranged from 26.6 to 36.2 mg 100 g^?1 dry weight, depending on SO₂ content of dried apricots. The SO₂ concentration over 791 mg per kg of dried apricots effectively protected carotenoids in dried apricots during drying. While storage times had significant effect on β-carotene contents, storage temperatures did not have such effects. The number of total mesophilic aerobic bacteria in all SDA samples ranged from 8.20?×?10¹ to 1.84?×?10² CFU g^?1. The number of total psychrophilic aerobic bacteria, lactic acid bacteria, yeast and mould, xerophilic mould, Staphylococcus spp. and total Enterobacteriaceae were below the detection limits (<4 CFU g^?1) in samples containing SO₂ even at the lowest level (188 mg SO₂ kg^–1) throughout the storage. Regardless of SO₂ concentration in dried apricots, low storage temperatures (below 20 °C) should be preferred to prevent the characteristic golden yellow colours of dried apricots.