Modelling of 5-hydroxymethylfurfural photo-degradation by UV irradiation. Influence of temperature and pH

The main aims of this study were (a) to prove that the UV irradiation of juices prevents the formation of 5-hydroxymethylfurfural (HMF), (b) to know the influence of temperature and pH on the UV photo-degradation of the HMF when it is unfortunately present in the juice (for example, after a previous thermal treatment or after a long storage period) and (c) to model this photo-degradation, proposing a reaction mechanism related to the power absorbed by the solution that depends on the HMF concentration.For these purposes a mid-pressure mercury lamp with emission wavelengths between 250 and 740 nm was used.Firstly, nectarine juice was irradiated to be sure that HMF was not synthesised. Then, aqueous solutions of 100 mg·L^− 1 HMF at pH 3, 4 and 5 were irradiated at 12, 25, 35 and 45 °C for 120 min. Aliquots were analysed to measure their HMF contents and absorption spectra.The photo-degradation data fitted well to both zero-order and pseudo-first-order kinetic models and the constant values were similar. The increases in both temperature and pH enhanced the photo-degradation, the optimal conditions inside the ranges studied being 45 °C and pH = 5, when a reduction of 60% of the initial content of HMF was reached.The spectral radiant power absorbed by the whole solution and the incident spectral radiant power reaching any depth of the reactor were evaluated taking into account the linear spherical emission model and using the Simpson integration method. Its dependence on the HMF concentration was also studied. A three stage degradation mechanism was proposed, matching both the zero-order and pseudo-first-order kinetic models previously obtained.     

Kinetic Characterization and Thermal Inactivation of Peroxidase in Aqueous Extracts from Sweet Corn and Waxy Corn

The objective of this study was to evaluate the activity, kinetic behavior, and thermal inactivation kinetics of peroxidase (POD) in aqueous extracts from two kinds of milk ripe stage corn, sweet corn and waxy corn. Optimum activities using guaiacol as the hydrogen donor were obtained for sweet corn at pH 4.8 and for waxy corn at pH 6.0. The kinetics of POD showed characteristics which were dependent upon the concentrations of guaiacol and H₂O₂. The guaiacol K _m values for sweet corn POD and waxy corn POD were 11.01 and 23.01 mM, respectively, whereas the H₂O₂ K _m values for sweet corn POD and waxy corn POD were 2.85 and 0.33 mM, respectively. Thermal treatment of enzymatic aqueous extracts was carried out at different time–temperature combinations in the range of 0–25 min and 60–85 °C. Arrhenius plot determination and calculated thermodynamic parameters suggested that the inactivation of POD followed first-order reaction kinetics, and the activation energy (E _a) for inactivation of sweet corn POD (114.36 kJ/mol) was slightly lower compared with waxy corn POD (119.72 kJ/mol). There were several notable similarities between the inactivation kinetics in the two corn cultivars.     

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.     

Effect of cream aging temperature and agitation on butter properties

Aging of cream is an important process to manage production time and to produce butter with consistent quality. The objective of this study was to evaluate the combined effect of temperature (5, 10, and 15°C) and agitation rate (0, 40, and 240 rpm) during aging of cream on the physical properties of cream and butter in a model system. Cream's solid fat content (SFC), melting behavior, and droplet size distribution were measured during and after 90 min of aging. Butter physical properties such as melting behavior, water content, and hardness were measured. The effects of agitation on SFC and droplet size are dependent on aging and churning temperature. Solid fat content increased faster at 5°C, and the maximum SFC was the highest at this temperature. An effect of agitation on SFC was observed only when cream was aged at 15°C. Agitating cream at 40 rpm increased the droplet size regardless of aging temperature. Two melting peaks, medium melting fraction (MMF) and high melting fraction (HMF), were found in cream samples aged at 5 and 10°C, but only a HMF melting peak was seen in the cream aged at 15°C. The enthalpy of MMF in the cream aged at 10°C with 40 rpm and without agitation was significantly lower than that in samples aged at 5°C regardless of agitation rate. Butter can be formed only from cream aged under certain conditions during 14.5 min of churning, which are 5°C with high agitation and 10°C regardless of agitation level. Butter produced with cream aged at 5°C with high agitation showed significantly higher MMF and total enthalpy values. However, no significant difference in enthalpy values was observed among the butter samples made from the cream aged at 10°C. Further crystallization of MMF occurred in the butter produced with cream aged at 10°C during 24 h of storage at 5°C, whereas no further crystallization occurred in the butter made with the cream aged at 5°C with high agitation. The hardest butter was obtained when cream was aged at 5°C with 240 rpm and at 10°C with 40 rpm. Softer butter was obtained when cream aged at 10°C with 240 rpm was used. This butter also had the highest water content. This study shows that butter hardness can be tailored by changing the aging conditions of the cream. Cream can be aged at higher temperature with low agitation without altering the hardness of butter. These results will help dairy producers to optimize butter making processes to obtain desired properties in the final product.     

Honey thermal treatment effects on hydroxymethylfurfural content

The effects of honey thermal treatment on the hydroxymethylfurfural (HMF) content (temperature and time) were studied, during both transient and isothermal heating stages. Assay was carried out with two honey samples whose initial HMF values were 3.9 and 26.6 mg HMF/kg honey. During the transient stage, treatment time ranged between 14 and 60 s, and treatment final temperature ranged between 100 and 160 °C. This study determined that initial HMF concentration did not affect its formation kinetics. HMF content change during the isothermal stage of the thermal treatment was determined at the final temperature of the transient stage and for treatment times up to 90 s, and it follows a kinetic model of pseudo first order. First order rate constants were correlated with temperature by an Arrhenius-type equation. Thus the values of the frequency constant and activation energy were obtained.     

Quantification of 5-Hydroxymethylfurfural in Coated Deep-Fried Products: Optimization of the Extraction Procedure by Using Statistical Design

This study describes for the first time the development and validation of an extraction procedure for the quantification of 5-hydroxymethylfurfural (HMF) in coated deep-fried products by liquid chromatography with photodiode array detection. The method entailed the extraction of HMF with ethyl acetate/hexane (4:1) followed by a concentration step with 40 mM sodium formate (pH?=?3)/methanol (1:1). The optimum combination of the extraction variables was achieved by response surface methodology. Sample amount and concentration solvent volume showed a notable influence on HMF yield, while the effect of extraction solvent volume seemed to be less marked. From experimental results, 5 g of sample, 10 ml of the extraction solvent, and 550 μl of the concentration solvent were selected as optimal combination. The consistency between predicted and experimented values as well as in the quality parameters was observed. Quantities of HMF in coated deep-fried fish products were 1.25?±?0.21 μg g^?1.     

Enhanced inactivation of pectin methyl esterase in orange juice using modified supercritical carbon dioxide treatment

The aim of the study is to quantify the effect of ethanol addition and exposure surface on the inactivation of pectin methyl esterase (PME), a juice clarifying enzyme, in orange juice using supercritical carbon dioxide (SC‐CO₂). Addition of ethanol to the SC‐CO₂ at 2% (v/v) caused greater inactivation than SC‐CO₂ alone, with a maximum reduction of PME activity of 97% at 30 MPa and 40 °C for 60 min. As the surface area to volume ratio was increased, the rate of inactivation of PME increased. Analysis of first‐order reaction kinetic data revealed that D values were greatly influenced by ethanol addition and agitation. With the addition of 2% ethanol, the D value reduced by half, that is, 56 min from 109 min. With impeller agitation of the sample at 1100 ± 100 rpm, the D value for PME was further reduced to 43 and 30 min without and with ethanol, respectively. The activity of PME treated with SC‐CO₂ remained unchanged after 14 days of storage at 4 °C. Treatment did not significantly change pH or colour, but did significantly increase the cloud values of the juice, resulting in a cloud stabilised juice with similar qualities to fresh juice.     

Hydroxymethylfurfural in fruit puree and juice: preconcentration and determination using microextraction method coupled with high-performance liquid chromatography and optimization by Box–Behnken design

In the present study, a sensitive and rapid method for separation and determination of hydroxymethylfurfural (HMF) in fruit puree and juices was proposed. Dispersive liquid–liquid microextraction (DLLME) coupled with high-performance liquid chromatography (HPLC) was used for extraction and quantitative determination of HMF in fruit puree and juices. The effective parameters such as the type and volume of extraction and dispersive solvents, pH and salt amount (NaCl) were studied and optimized with the aid of response surface methodology based on Box–Behnken design to obtain the best condition for HMF extraction. At the optimized conditions, parameter values were 60 µL extracting solvent, 600 µL dispersive solvent, 2 g NaCl and pH 5. Repeatability of the method, described as the relative standard deviation, was 3.1% (n?=?6) and the recovery was 98.4%. The limit of detection and limit of quantitation were 1.47 and 5.28 µg L^?1, respectively. The merit figures of DLLME–HPLC–UV method showed that the proposed method can be noticed as a new, fast and good alternative method for investigation of HMF in various fruit puree and juice samples.     

Raising agents strongly influence acrylamide and HMF formation in cookies and conditions for asparaginase activity in dough

The impact of raising agents on formation of heat-induced contaminants, acrylamide and 5-hydroxymethylfurfural (HMF), with focus on the efficiency of enzyme asparaginase as a potent tool for acrylamide reduction was investigated in the model system of cereal products. Acrylamide formation was strongly supported by ammonium hydrogen carbonate (NH₄HCO₃), observing 6 times higher level in comparison with control sample without raising agents, and was suppressed effectively by sodium hydrogen carbonate (NaHCO₃) up to 52 %. Sodium pyrophosphate (Na₄P₂O₇) had no influence on the final acrylamide content. The level of HMF remained untouched by NH₄HCO₃ contrary to sodium raising agents that both diminished HMF concentration up to 95 % using NaHCO₃. Furthermore, enzyme asparaginase eliminated acrylamide formation in the range from 23 to 75 % depending mainly on pH value of dough and time of enzyme incubation (15, 30 and 60 min). The optimum pH value for asparaginase action was in neutrality. Na₄P₂O₇ shifted pH value of dough to the optimum in comparison with control (from 5.82 to 6.78). NH₄HCO₃ and NaHCO₃ changed pH value out of optimum up to 7.82 and 8.10, respectively. The longer the enzyme treatment, the higher the acrylamide elimination was observed, with the main importance in cases of pH shifting by raising agents. These findings indicate that a product-specific optimization of the conditions for enzymatic treatment is still challenging in terms of achieving desired quality parameters with improved safety, although acrylamide mitigation by means of asparaginase was proved to be a very effective tool especially in cereal-based products.     

Parameters affecting 5-hydroxymethylfurfural exposure from beer

5-Hydroxymethylfurfural (HMF) is generated during food and beverage heating processes and/or storage. Its daily intake, estimated as 4–10 mg day^?1, is several orders of magnitude higher than other process contaminants. Beer can be of relevance to the evaluation of HMF exposure; however, the information concerning its occurrence in different types of beer and during product storage is scarce. Therefore, the major goal of this work was to assess the amounts of HMF in different commercial beers, as well as the impact of storage, to deepen knowledge about the contribution of beer to HMF exposure. Blonde beers presented a mean content of 4.29 ± 1.05 mg L^?1, which was significantly lower (P ≤ 0.05) than those obtained for amber (6.84 ± 0.75 mg L^?1) and dark beers (6.99 ± 0.52 mg L^?1). Additionally, to study kinetic of HMF formation, fresh pilsner beers were stored at 30, 40 and 50°C during 40 days; a zero-order reaction was observed. The dependence of the rate constant on temperature was described by the Arrhenius equation and calculated activation energy was 101.85 kJ mol^?1. Storage can increase drastically HMF content, which means higher exposure for consumers. Thus, beer contribution to HMF exposure should not be neglected, since the intake of 1 L of beer entails a consumption of 4–7 mg of HMF or even more, depending on storage time and temperature.     

Micellar Electrokinetic Chromatography Method for Determination of the Ten Water-Soluble Vitamins in Food Supplements

The separation and determination of the ten water-soluble vitamins by using capillary electrophoresis in the micellar electrokinetic chromatography in a single run are proposed. The method uses low toxicity and cost solvent (ethanol) as modifier of background electrolyte (BGE) attending to the Green Chemistry principles. The electrophoretic method uses 10.0 % (v/v) ethanol, 2.0 % (w/v) SDS, 0.02 mol?L^?1 borate at pH 8.70 as BGE. The standard and real sample solutions were injected in the eletrophoretic system by hydrodynamic injection under pressure of 0.80 psi for 8 s, and the separation was carried out in a fused silica capillary under a potential of 28 kV at 25 °C; the analytical signals were monitored at 214 nm. The analytical method is precise (r.s.d.?<?6 %), accurate (better than 9 %), selective, sensitive, robust, simple, and presents high analytical frequency as ten water-soluble vitamins were separated in only 18 min, with migration times of 5.75?±?0.02, 6.81?±?0.02, 8.13?±?0.04, 8.80?±?0.07, 8.98?±?0.06, 11.10?±?0.08, 11.34?±?0.05, 13.85?±?0.15, 14.82?±?0.04, and 17.85?±?0.30 min. Detection and quantification limits of 0.34, 0.32, 0.27, 0.20, 2.50, 4.98, 4.92, 0.30, 0.86 and 0.28 mg?L^?1 and 1.02, 0.97, 0.83, 0.62, 7.56, 15.09, 14.91, 0.90, 2.59 and 0.83 mg?L^?1, for vitamins PP (nicotinamide), B₁₂ (cyanocobalamin), B₂ (riboflavin), B₆ (pyridoxine), B₈ (biotin), C (ascorbic acid), B₅ (pantothenic acid), B₃ (nicotinic acid), B₁ (thiamine), and B₉ (folic acid), respectively. Excellent recoveries (intra and inter-day) were obtained and, when the method was applied to food supplement analyses the results were in agreement with the conventional HPLC methods.     

Shorea dasyphylla sawdust for humic acid sorption

The efficacy of Shorea dasyphylla sawdust as an adsorbent for the removal of humic acid from aqueous solution was investigated as a function of pH value, agitation period, agitation rate, initial humic acid concentration and adsorbent dosage. The equilibrium nature of humic acid adsorption was described by the Langmuir, Freundlich and BET isotherms. The experimental adsorption data was best fitted to the Langmuir adsorption model, which gave adsorption capacity of 68.4 mg humic acid adsorbed per gram Shorea dasyphylla sawdust at pH 2.0 and initial humic acid concentration of 80 mg?L^-1. Kinetic studies indicated that the sorption process followed the pseudo-second-order kinetic model. It was revealed that after three cycles of adsorption and desorption, Shorea dasyphylla sawdust retained its promising adsorption ability. With an initial amount of 73.5 mg humic acid adsorbed per gram sawdust, more than 80% of humic acid desorbed by using 0.1 M HCl. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed to study the mechanism of the removal of humic acid. From the dimensionless factor, R_L data, it was determined that the adsorption of humic acid onto untreated Shorea dasyphylla sawdust was favourable.     

Kinetic and Thermodynamic of Thermal Inactivation of the Peroxidase,Polyphenoloxidase and Inulinase Activities during Blanching of Yacon (Smallanthus sonchifolius) Juice

The present study evaluated the kinetics and thermodynamic parameters for the thermal inactivation of peroxidase (POD), polyphenoloxidase (PPO) and inulinase (INU) from yacon juice. The yacon juice was acidified with 1 % citric acid prior to blanching at different time-temperature combinations in the range of 0–10 min, and 80–100 °C. All enzymes showed a biphasic kinetic behavior. The velocity constants increased and D values decreased with temperature for both the labile and the heat resistant fractions. The activation energy of the heat-labile (E _aL ) and heat-resistant fractions (E _aR ) were 38.19, 16.05, 30.08 kJ/mol, and 30.65, 71.94, 41.86 kJ/mol for POD, PPO and INU, respectively. Thermodynamic studies indicated a non-spontaneous (ΔG?>?0) and endothermic (positive enthalpy values) process, and the enzyme aggregation step is the rate determining of the reaction (negative entropy values).     

Steaming time effects on the moisture migration and structural properties of Chinese Northern-style steamed bread

The aim of this study was to investigate the steaming time effects on proton transverse relaxation behavior with low field 1H nuclear magnetic resonance and structural properties of Chinese Northern-style steamed bread (CNSB). Three proton populations could be distinguished at the first 4 min: T_2b (0.1–1 ms) corresponded to rigid and exchangeable protons; T₂₂ (9–21 ms) was associated with the water protons in small and large meshes of the dough microstructure; T₂₃ (69–300 ms) was assigned to the water protons on the surface of samples. The starch gelatinization began and the water turned into the integral part of the biopolymer at 6 min, forming T₂₁ (1–3 ms) fraction. The gelatinization effect was strengthened up to 8 min and supplied a more mobile microenvironment, resulting in the increase of T₂₁, A₂₁ and M₂₁. However, the gelatinization process ended at 8 min, bringing about the stabilization of T₂₁, A₂₁ and M₂₁ until 25 min. T₂₂ fraction accounted for the largest proportion during all the steaming process. All variation trends on structural properties of CNSB and T₂ relaxation parameters including T_i, A_i (relative intensity of T_i), and M_i (population abundance of T_i) indicated that 6 and 8 min were the two transitions. The gluten matrix began to be disrupted at 6 min and was quite damaged up to 8 min by scanning electron microscopy. The peaks at 15°, 18°, 20°, and 23° in X-ray diffraction patterns appeared in the first 6 min but were lost up to 8, 10, and 25 min.     

Linear correlation between pH value of stimulated beef and electrical current intensity

The aim of the present study was to determine mathematical relationships between pH changes in beef 24 h post-slaughter and changes in the intensity of electrical current flowing through bull and heifer carcasses during high-voltage electrical stimulation. The electrical stimulation was applied 40 min postmortem for 120 s. The pH values of m. longissimus thoracis et lumborum were analyzed in the function of electrical current intensity changes and its change during electrical stimulation. Mathematical linear correlations of the y = ax ± b type were demonstrated between pH values at 2, 6, and 24 h postmortem and the initial (I_i) and ultimate (I_u) electrical current intensity values, the difference between them and the initial pH values determined before electrical stimulation. High multiple correlation coefficients (R² = 0.416, α ≤ 0.001) between I_u and pH values 24 h post-slaughter enabled concluding that there is a possibility to predict a pH value of stimulated carcass with high accuracy, and thus also beef quality, based merely on the ultimate electrical current intensity values.     

Nylon fibers coated with diclofenac: adsorption properties

Dried gauzes properly coated with anti-inflammatory drugs could be helpful in providing topical treatment in inflammatory process. Therefore, thermodynamic of adsorption of Diclofenac Sodium, over Nylon fibers, as a function of concentration, temperature, and pH of the medium, have been studied. Maximum amount adsorbed in the best conditions tested, pH 5.6, 323 K and initial concentration of 150 mg/L has been 2.6 mg/g. Isotherm adsorption data were well fitted to the Langmuir and Freundlich model; therefore, multilayer formation must be considered. Negative and low values of free-energy change, ?17.9 kJ/mol and ?15.9 kJ/mol, in addition to moderate value of activation energy 13.14 kJ/mol point to physical interactions governing the process that, besides, is exothermic with negative enthalpy-change, ?43.44 kJ/mol, and also follows pseudo-first order kinetic model that is typical of this interaction. Desorption experiments carried out under physiological conditions confirm that the proposed procedure for DCF administration could be achieved.     

Biochemical and Structural Changes of Taro (Colocasia esculenta) Tubers During Simple Thermal Treatments (Low Temperature) or in Combination with Chemicals

The present study set out to study the structural and biochemical modification of taro (Colocasia esculenta) grown in Cameroon, through simple heating or in association with chemicals. Both techniques are known to inactivate the reactions of polyphenol oxidase. The textural analysis was performed on tubers heated in water, 0.5% NaCl and 1% NaCl solution at various times from 0 to 105?min. The result showed optimum pH and temperature for taro polyphenol oxidase (PPO) activity at pH?6.0 and t?=?40?°C with 10?mM catechol in 0.1?M phosphate buffer as substrate. K _m and V _max values were about 7.317?±?0.012?mM and 0.148?±?0.0003 OD_{430 nm}/minute. Seven inhibitors were tested in this study, and the most effective inhibitors were found to be NaCl, CaCl2 and KCl. Kinetic studies showed that the thermal inactivation of taro PPO followed first-order kinetics, with an activation energy of E _a?=?422.79?±?0.52?kJ/mol. The textural modification of taro tubers during heating follows the kinetic of the fractional model. It was noticed that the activation energy increased with the concentration of NaCl.     

Absolute Determination of the Gelling Point of Gelatin under Quasi‐thermodynamic Equilibrium

Thermodynamic studies on phase transformation of biopolymers in solution are useful to understand their nature and to evaluate their technological potentials. Thermodynamic studies should be conducted avoiding time‐related phenomena. This condition is not easily achieved in hydrophilic biopolymers. In this contribution, the simultaneous effects of pH, salt concentration, and cooling rate (Cr) on the folding from random coil to triple helical collagen‐like structures of gelatin were systematically studied. The phase transformation temperature at the absolute invariant condition of Cr = 0 °C/min (T_T^Cr=0) is introduced as a conceptual parameter to study phase transformations in biopolymers under quasi‐thermodynamic equilibrium and avoiding interferences coming from time‐related phenomena. Experimental phase diagrams obtained at different Cr are presented. The T_T^Cr=0 compared with pH and T_T^Cr=0 compared with [NaCl] diagram allowed to explore the transformation process at Cr = 0 °C/min. The results were explained by electrostatic interactions between the biopolymers and its solvation milieu.     

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     

Hydroxymethylfurfural determination in infant milk-based formulas by micellar electrokinetic capillary chromatography

A procedure for determining hydroxymethylfurfural (HMF) in milk-based products by micellar electrokinetic capillary chromatography (MECC) was settled on. The effect of the trichloroacetic acid on the migration time of HMF and presence of interference peaks were investigated. MECC procedure was applied on commercial liquid infant formulas and compared with the classical reversed-phase high performance liquid chromatography method, giving similar values of repeatability and recovery. HMF peak was well-resolved by using an uncoated fused-silica capillary (48.5 cm×50 μm i.d.) with 50 mM phosphate buffer (pH 7.5) containing 100 mM SDS as electrolyte, voltage at 20 kV (25°C). Sample injection was by pressure (50 mbar, hydrodynamic) for 2.5 s. HMF analysis by MECC was suitable for routine analysis since separation was completely achieved at 5 min.