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1.
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  相似文献   

2.
Extraction of sugar from sugar beet slices was studied following various pulsed electric field (PEF) treatments (intensities from 300 to 800 V cm?1 and number of pulses varying between 50 and 1000). Slices treated by PEF were immersed in water at ambient temperature at a liquid/solid ratio of 3. A significant increase in extraction yield was observed. This enhancement was due to permeabilisation of the cellular membrane and to the additional quantity of juice appearing on the surface of slices after PEF treatment being extracted rapidly by convection. The optimal conditions of PEF treatment were an intensity of 670 V cm?1 and 250 pulses. The extraction kinetics was studied on the basis of two approaches: Fick's diffusion equation and a two‐exponential kinetic model. The coefficient of diffusion was only slightly influenced by the conditions of PEF treatment. The two‐exponential model successfully described both the rapid and prolonged stages of extraction. By heating the solution at mild temperatures of 30–50 °C, the coefficient of diffusion was increased and the kinetics of extraction was enhanced. The quality of cellular juice obtained after PEF treatment was higher than that of juice obtained after thermal pretreatment at 75 °C. Copyright © 2004 Society of Chemical Industry  相似文献   

3.
Purification of the sugar beet juices obtained by novel low temperature extraction (at 30 °C) assisted by pulsed electric field (PEF) and conventional high temperature extraction (at 70 °C) was done by the method of lime-carbon dioxide treatment. The total concentration of lime used for the purification was varied from 6 to 15 kg of CaO/m3 of the juice. Filtration properties of the juices of first carbonation, as well as purity and coloration of the final thin juices, were compared. It was observed that purification of the juice extracted at 30 °C results in faster filtration of the juice of first carbonation and lower coloration of the final thin juice as compared to the juice obtained by means of purification of the juice extracted at 70 °C. It suggests that the quantity of CaO required for the efficient juice purification may be decreased from 15 kg/m3 (for the juice extracted at 70 °C without PEF treatment) to approx. 8 kg/m3 (for the juice obtained by PEF-assisted extraction at 30 °C).  相似文献   

4.
This study describes experiments on pulsed electric field (PEF)-assisted water extraction of sugar from sugar beet using a pilot countercurrent extractor with 14 extraction sections. Cossettes were prepared from sugar beet by industrial knives and PEF treatment of the cossettes was done with electric field strength E varied between 100 and 600 V/cm. The total time of PEF treatment was tPEF = 50 ms. The effects of the main extraction parameters (temperature of extracting water and draft) on the extraction kinetics, as well as on the juice and cossette (pulp) characteristics, were investigated. The temperature of extraction from PEF-treated cossettes was varied from 30 to 70 °C; the draft was varied from 120 to 90%. The principal possibility of cold (at 30 °C) and moderate thermal (50-60 °C) extraction of sucrose from sugar beet cossettes treated by PEF was confirmed on the pilot countercurrent extractor. The purity of the juice obtained by cold and moderate thermal extraction was not lower than the purity of juice obtained by conventional hot water diffusion at 70 °C. The sugar beet pulp can be well exhausted by cold or mild thermal extraction of cossettes treated by PEF. Decrease of draft to 100-90% permitted increasing of the extracted juice concentration, but the cossettes were worse exhausted. The pulp obtained by cold extraction of PEF-treated cossettes had dryness >30%, which was noticeably higher than dryness of the pulp obtained by conventional hot water extraction technique.  相似文献   

5.
This work discusses effects of thermal and PEF treatments on efficiency of soluble solids extraction from chicory tissues. The effects of temperature, PEF electric field strength and time of treatment on damage degree and acceleration of the soluble matter extraction kinetics are discussed. The PEF treatment with field strength 100–600 V/cm, treatment time 10−3–50 s, and temperature 20–80 °C, was applied. The activation energy of usual thermal damage was rather high (Wτ ≈ 263 kJ/mol), however, it can be noticeably reduced to Wτ = 30–40 kJ/mol by application of PEF treatment. The moderate electric energy consumption (U < 10 kJ/kg) at room temperatures demands application of relatively high electric field strength (400–600 V/cm), however, the value of U noticeably decreases with temperature increase. The benefits of PEF application for enhancement of the soluble matter extraction from chicory were demonstrated. The PEF-pretreatment noticeably accelerated diffusion even at low temperatures within 20–40 °С. Proposed technique appears to be promising for future industrial applications of “cold” soluble matter extraction from chicory roots.  相似文献   

6.
The effect of the application of pulsed electric field (PEF) treatments of different intensities (0–2 kV/cm) on Arbequina olive paste in reference to olive oil extraction at different malaxation times (0, 15, and 30 min) and temperatures (15 and 26 °C) was investigated. The extraction yield improved by 54 % when the olive paste was treated with PEF (2 kV/cm) without malaxation. When the olive paste was malaxated at 26 °C, the application of a PEF treatment did not increase the extraction yield as compared with the control. However, at 15 °C, a PEF treatment of 2 kV/cm improved the extraction yield by 14.1 %, which corresponded with an enhancement of 1.7 kg of oil per 100 kg of olive fruits. The application of a PEF treatment could permit reduction of the malaxation temperature from 26 to 15 °C without impairing the extraction yield. Parameters legally established (acidity, peroxide value, K232, and K270) to measure the level of quality of the virgin olive oil were not affected by the PEF treatments. A sensory analysis revealed that the application of a PEF treatment did not generate any bad flavor or taste in the oil.  相似文献   

7.
Detailed comparison of various properties (concentration of soluble solids, purity, nature of impurities, coloration and filterability) of sugar beet juices obtained by pulsed electric field (PEF) assisted “cold” extraction (T = 30 and 50 °C) and classical “hot” extraction (T = 70 °C) was done. It was shown that application of PEF-assisted “cold” extraction results in lower concentration of colloidal impurities (especially, pectins), lower coloration and better filterability of juice. Concentration of various colorants and their intermediates decreased significantly with decreasing of the extraction temperature from 70 °C to 30 °C. Filtrate obtained by dynamic filtration of juice extracted with PEF treatment had a high purity (95.3 ± 0.4%) and low coloration (1.2×103 IU). Obtained data suggest that PEF-assisted “cold” extraction is a promising method for preparation of sugar beet juices with high purity.  相似文献   

8.
Identifying equivalent processing conditions is critical for the relevant comparison of food quality attributes. This study investigates equivalent processes for at least 5-log reduction of Escherichia coli and Listeria innocua in pineapple juice–coconut milk (PC) blends by high-pressure processing (HPP), pulsed electric fields (PEF), and ultrasound (US) either alone or combined with other preservation factors (pH, nisin, and/or heat). The two blends (pH 4 and 5) and coconut milk (pH 7) as a reference were subjected to HPP at 300–600 MPa, 20°C for 0.5–30 min; PEF at an electric field strength of 10–21 kV/cm, 40°C for 24 µs; and US at 120 µm amplitude, 25 or 45°C for 6 or 10 min. At least a 5-log reduction of E. coli was achieved at pH 4 by HPP at 400 MPa, 20°C for 1 min; PEF at 21 kV/cm, 235 Hz, 40°C for 24 µs; and US at 120 µm, 45°C for 6 min. As L. innocua showed greater resistance, a synergistic lethal effect was provided at pH 4 by HPP with 75 ppm nisin at 600 MPa, 20°C for 5 min; PEF with 50 ppm nisin at 18 kV/cm, 588 Hz, 40°C for 24 µs; and US at 45°C, 120 µm for 10 min. The total soluble solids (11.2–12.4°Bx), acidity (0.47%–0.51% citric acid), pH (3.91–4.16), and viscosity (3.55 × 10−3–4.0 × 10−3 Pa s) were not significantly affected under the identified equivalent conditions. HPP was superior to PEF and US, achieving higher ascorbic acid retention and lower color difference in PC blend compared to the untreated sample.  相似文献   

9.
The effect of culture temperature on the conformation of membrane lipid of Salmonella Typhimurium as well as their pulsed electric field (PEF) resistance was investigated. Results revealed that S. Typhimurium cells cultured at relatively lower temperature (10 and 25 °C) were more easily inactivated by PEF treatment than those cultured at relatively higher temperature (37 and 45 °C). Using a Weibull model, it was determined that the PEF treatment time to inactivate 90% S. Typhimurium cells cultured at 45 °C was almost fourfold compared to those cultured at 10 °C. Results of micro‐Raman spectroscopy indicated that as the culture temperature increased, the order degree of C–C and lateral packing order of membrane lipid chain also increased, resulting in a drop in the membrane fluidity. These results are important in considering the use of heat and PEF to inactivate microbe contaminants in food.  相似文献   

10.
Radio frequency (RF) preprocessing combined with pulsed electric field (PEF) processing was employed to inactivate polyphenol oxidase (PPO) in apple juice. PPO enzyme levels, loss of total phenolic content (TPC), colours and volatile components in the apple juice were subsequently determined and compared with conventional processing methods (60 °C for 10 min and 70 °C for 10 min). Results indicated that, when the apple tissue was preprocessed using RF for 10 min, the residual activity of PPO decreased to 13.57%; when the squeezed juice was processed by PEF, the residual activity decreased to about 5% at 15–35 kV cm?1 for 400 μs. RF treatment caused no significant loss in TPC. Compared with the conventionally processed samples, the apple juice that was RF‐treated for 10 min and PEF‐treated at 15 kV cm?1 for 400 μs increased its lightness and maintained its fresh‐like flavour.  相似文献   

11.
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 %).  相似文献   

12.
ABSTRACT: Moderate heat in combination with pulsed electric fields (PEF) was investigated as a potential alternative to thermal pasteurization of a tropical fruit smoothie based on pineapple, banana, and coconut milk, inoculated with Escherichia coli K12. The smoothie was heated from 25 °C to either 45 or 55 °C over 60 s and subsequently cooled to 10 °C. PEF was applied at electric field strengths of 24 and 34 kV/cm with specific energy inputs of 350, 500, and 650 kJ/L. Both processing technologies were combined using heat (45 or 55 °C) and the most effective set of PEF conditions. Bacterial inactivation was estimated on standard and NaCl‐supplemented tryptone soy agar (TSA) to enumerate sublethally injured cells. By increasing the temperature from 45 to 55 °C, a higher reduction in E. coli numbers (1 compared with 1.7 log10 colony forming units {CFU} per milliliter, P < 0.05) was achieved. Similarly, as the field strength was increased during stand‐alone PEF treatment from 24 to 34 kV/cm, a greater number of E. coli cells were inactivated (2.8 compared with 4.2 log10 CFU/mL, P < 0.05). An increase in heating temperature from 45 to 55 °C during a combined heat/PEF hurdle approach induced a higher inactivation (5.1 compared with 6.9 log10 CFU/mL, respectively {P < 0.05}) with the latter value comparable to the bacterial reduction of 6.3 log10 CFU/mL (P≥ 0.05) achieved by thermal pasteurization (72 °C, 15 s). A reversed hurdle processing sequence did not affect bacterial inactivation (P≥ 0.05). No differences were observed (P≥ 0.05) between the bacterial counts estimated on nonselective and selective TSA, suggesting that sublethal cell injury did not occur during single PEF treatments or combined heat/PEF treatments.  相似文献   

13.
Grapefruit juice was investigated using pulsed electric fields (PEF) with (electric field strengths: 0, 5, 10, 15, 20 and 25 kV cm?1; flow rate: 80 mL min?1; pulse frequency: 1 kHz at 40 °C for 600 μs). Total phenolics, DPPH, total antioxidant capacity (TAC), total anthocyanins, total carotenoids, sugars and physicochemical properties of grapefruit juice were studied. In addition, the effect of PEF treatment on micro‐organisms was also observed. Results indicated that no significant change was observed in pH, Brix, titratable acidity, sugars, total anthocyanins and colour attributes with the increase in pulsed electric strength as compared to control treatment. However, significant decrease in nonenzymatic browning (NEB) and viscosity while an increase in cloud value, DPPH, TAC, total phenolics and total carotenoids, while reduction in the activity of micro‐organisms, was also observed with the increase in pulsed electric strength as compared to control treatment. This study suggested that PEF at 25 kV cm?1 could improve the quality of grapefruit juice.  相似文献   

14.
Inulin constitutes an important food ingredient, widely used for its fiber content, and its ability to substitute fat and sugar ingredients. Traditionally, industrial inulin production from chicory roots requires high extraction temperature (70–80 °C) and long extraction time (1–2 h). This conventional extraction is generally accompanied with the presence of a large amount of impurities in the extracted juice, mainly due to the application of high temperature, requiring thus further purification steps. To overcome these issues, developing novel extraction technologies, consuming less energy, faster, and providing high yield and purity, is of paramount importance to meet the requirements of a green extraction concept. In this review, the feasibility of using conventional and new promising technologies (enzyme assisted extraction, ultrasounds, microwaves, supercritical fluid extraction, and pulsed electric fields) to recover inulin from plant food materials and by-products from an environmental and economical point of view will be discussed.Industrial relevanceInulin is widely used in food industries mainly due to its ability to substitute fat and sugar ingredients. However, the current industrial recovery process of this molecule is mainly carried out by diffusion in hot water (70–80 °C), followed by a relatively complex purification process, due to the presence of a large amount of impurities generated by the application of high temperatures. The need for obtaining greener, sustainable, and viable processes has led food scientists to develop new processes in full correspondence with the green extraction concept based on the use of non-conventional technologies (i.e. pulsed electric fields, ultrasounds, microwaves, etc). The submitted review discusses the potential of some of these new promising technologies to allow the industrial sustainability and green recovery of inulin, which have as benefits: energy- and time-saving along with higher yields and milder temperatures, reducing thus the subsequent purification steps.  相似文献   

15.
The polyphenols extraction from grape seeds was studied. In order to increase the polyphenols yield and the extraction kinetics, three different pre-treatments were applied on grape seeds: pulsed electric fields (PEF) (8–20 kV/cm, 0–20 ms), high-voltage electrical discharges (HVED) (10 kA/40 kV, 1 ms) and grinding (180 W, 40 s). These electrical treatments can damage cell membranes (PEF/HVED) and cell walls (HVED) thus accelerating the compounds extraction but have different effects on the product fragmentation. The diffusion was then performed after pre-treatment with a mixture of water and ethanol. The PEF efficiency was improved when the treatment was performed at 50 °C in the presence of ethanol. PEF-assisted diffusion was then compared to HVED-assisted diffusion and to diffusion of ground grape seeds. These two pre-treatments increased both the extraction kinetics and the maximum polyphenols yield. For both cases, the final polyphenols content was 9 g GAE/100 g DM after 15 min of extraction with grinding and after 60 min with HVED. When PEF were applied in a suspension containing ethanol, the maximum polyphenols yield was also reached after 60 min. The subsequent solid–liquid separation was faster with PEF as compared to ground and HVED-treatments.  相似文献   

16.
Orange juice was treated with pulsed electric fields (PEF) in a pilot‐plant system to optimize PEF‐processing conditions for maximum microbial inactivation and to investigate the effects of PEF on pectin methyl esterase (PME) activity. Electric‐field strengths of 20,25,30, and 35 kV/cm and total treatment times of 39, 49, and 59 μs were used. Higher electric‐field strengths and longer total treatment times were more effective to inactivate microorganisms and PME (p < 0.05). PEF treatment of orange juice at 35 kV/cm for 59 μs caused 7–log reductions in total aerobic plate count and yeast and mold counts. About 90% of PME activity was inactivated by PEF treatment at 35 kV/cm for 59 μs. PEF‐treated orange juice at 35 kV/cm for 59 ms did not allow growth of microorganisms and recovery of PME at 4, 22, and 37 °C for 112 d.  相似文献   

17.
In this study, a D‐optimal design was used to optimise the extraction process conditions of inulin with a high degree of polymerisation from Globe artichoke heart (Cynara cardunculus L. subsp. scolymus (L.) Hegi.), using electromagnetic induction heating (EMIH) as a new extraction process. Four factors were simultaneously studied which were the extraction temperature (55–90 °C), the extraction time (30–120 min), the weight ratio (plant material dry weight/volume of distilled water: 5–10%) and the mode of heating (conventional or electromagnetic induction heating). It was found that the second‐order polynomial models developed by the response surface methodology (RSM) describe adequately the relationship between the factors and responses (extraction yield, viscosity and solubility of inulin). The optimum extraction conditions that led to a maximal extraction yield (45.98%) and an optimal viscosity (3.25 mL g?1) of extracted inulin are temperature of 89.49 °C, extraction time of 120 min and a 5.01% of weight ratio using EIMH process. Fourier Transform InfraRed spectroscopy spectrum of the extracted inulin was identical to that of the native inulin. The analysis of the extract by thin‐layer chromatography confirms the absence of pectin in the final product, as well as the X‐ray diffraction analysis exhibits a semi‐crystalline structure of the biopolymer.  相似文献   

18.
Purification of raw sugar beet juice expressed at ambient temperature (20 °C) from pretreated sugar beet slices by pulsed electric field (E = 600 V·cm 1, tPEF = 10 ms, T = 20 °C) was studied on the laboratory scale by dead-end ultrafiltration tests. Polyethersulfone (PES) and Regenerated Cellulose (RC) membranes with the same nominal molecular weight cut-off of 30 kDa were used. Experiments were carried out in unstirred and stirred (at rotation speed of 500 rpm) mode at constant trans-membrane pressure of 2 bar. The effects of the membrane polymer (Polyethersulfone and Regenerate Cellulose) on the filtration flux and the permeate quality were studied. In order to identify the fouling mechanism, the filtration kinetics was modeled using combined fouling models. Results showed that the filtration productivity (filtration flux) and selectivity (rejection ratio of impurities) depended on the membrane polymer. The juice filterability was better with Regenerated Cellulose (RC) membrane while the polyethersulfone (PES) membrane ensured a better retention of impurities (colorants, proteins and colloids), leading to a higher juice purity. Experimental and models data adjustment showed that combined models were preferable to investigate the fouling mechanism for both unstirred and stirred filtration. The desirable sugar purity (95–96%) of filtrate implies the potential application of a novel process (PEF treatment-cold pressing-ultrafiltration) for sugar industrial production.Industrial relevancePre-treatment by pulsed electric field PEF allowed cold or mild extraction of sucrose from sugar beet roots. The combination of PEF and ultra-filtration allowed high yield sucrose extraction and purification with less energy consumption. Membrane fouling analysis led to better filtration producibility. The obtained data can be useful for optimization of the sucrose production with high yield in industrial extraction processes.  相似文献   

19.
Nonenzymatic Browning in Pear Juice Concentrate at Elevated Temperatures   总被引:2,自引:0,他引:2  
The effect of temperature and soluble solids (°Brix) on nonenzymatic browning in pear juice concentrate was determined by following absorbance at 420 nm (A420) over the temperature range of 50–80°C. Browning could be modeled as a zero order rate process with rates of 22.2 × 10−4 (45.2 °Brix), 36.9 × 10−4 (55.4 °Brix), 53.5 × 10−4 (65.1 °Brix) and 107 × 10−4 (72.5 °Brix) A420· min−1 at 80°C. Temperature dependence was described by the Arrhenius relationship with an average activation energy of 21.9 kcal · mole−1. Formol titration indicated a 20% loss of amino acids during heating 4.4 hr at 80°C and no loss of carbohydrates was observed after any heating period.  相似文献   

20.
S. Min    Q.H. Zhang 《Journal of food science》2003,68(5):1600-1606
Effects of commercial‐scale pulsed electric field (PEF) processing on the flavor and color of tomato juice during storage at 4 deg;for 112 d were studied. Tomato juice was prepared by hot break at 88°C for 2 min and then thermally processed at 92° for 90 s or PEF processed at 40 kV/cm for 57 μs. The PEF‐processed tomato juice retained more flavor compounds of trans‐2‐hexenal, 2‐isobutylthiazole, cis‐3‐hexanol than thermally processed or unprocessed control tomato juice (P < 0.05). PEF‐processed juice had significantly lower nonenzymatic browning and higher redness than thermally processed or control juice (P < 0.05). Sensory evaluations indicated that the flavor of PEF‐processed juice was preferred to that of thermally processed juice (P < 0.01).  相似文献   

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