Degradation of 5‐Hydroxymethylfurfural in Honey

ABSTRACT: 5‐Hydroxymethylfurfural (HMF) is the most important intermediate product of the acid‐catalyzed dehydration reaction of hexoses and/or Maillard reaction; furthermore, it is the most used index to evaluate thermal damages or ageing in food products. Usually its degradation reactions, being very slow, are neglected. This study reports the findings concerning the degradation kinetics of HMF, in honeys of different floral origin at a temperature between 25 and 50 °C. The results highlighted higher degradation rates (k_{HMFdegradation}) compared to the corresponding formation rates (k_HMFformation) in chestnut and citrus samples. Similar k‐values were found in multifloral honey. Moreover, the reaction of HMF degradation was characterized by lower activation energy (E_a) values compared to E_a formation values. The final concentration of HMF in honey, during storage at room temperature, should be ascribed to high sugar concentration. The fluctuation of HMF in honeys could depend on the equilibrium between the accumulation and the degradation processes. This can affect the validity of HMF as storage index in some honeys, above all during the analysis of those honeys whose legislation is too restrictive (citrus) or in chestnut honey analysis where it does not accumulate.     

Effect of storage on nonenzymatic browning reactions in carob pekmez

Carob pekmez was stored at 5, 25, 35 and 45 °C for studying the reaction kinetics of nonenzymatic browning reactions. Hydroxymethylfurfural (HMF) formation, browning index (A₄₂₀) and CIE (International Commission on Illumination) colour parameters were analysed to evaluate nonenzymatic browning reactions. HMF formation and A₄₂₀ values increased linearly with the storage time and temperature and both followed zero‐order reaction. No fitting model was found for the changes in visual CIE parameters. The dependence of rate constant of nonenzymatic reactions on temperature was represented by an Arrhenius equation and the activation values were found as 114.87 kJ mol^?1 and 86.62 kJ mol^?1 for HMF formation and A₄₂₀ values, respectively. The excellent linear correlations (r = 0.728–0.99) among colour parameters, browning index and HMF were found.     

Flow Properties of Low-Pulp Concentrated Orange Juice: Serum Viscosity and Effect of Pulp Content

65° Brix serum samples from four concentrated orange juice (COJ) samples, between -19 and 30°C, were mildy shear-thinning fluids with negligible yield stress. The power law model described well the flow data. For one sample, the Powell-Eyring model also described the data. The activation energy of flow (E_a) for the samples was between 11.2–13.6 kcal/gmole. The power law parameters were determined for a 65°Brix sample as a function of pulp content (0–11%) between −19 and 30°C. At a fixed temperature, the apparent viscosity and the consistency index increased exponentially with pulp content. E_a decreased with increase in pulp content and reached a constant value of about 10.2 kcal/gmole. Data on a high-pulp (21.2%), 65° Brix, sample indicated the presence of yield stress, particularly at low temperatures. The Mizrahi-Berk model predicted reliable values of the yield stress.     

Effect of toasting time on the browning of sliced bread

Slices of wheat bread were toasted for different times until a distinct intensity of brown colour was reached. Two assays were carried out: prolonged toasting times (5–60 min) and reduced toasting times (0.5–5 min). The browning indicators (furosine, available lysine, hydroxymethylfurfural (HMF), colour and absorbance at 284 and 420 nm) were determined. The precision of all indicators used was high (CV < 4%). No furosine or HMF was detected in the dough before baking. The furosine content increased until 7 min (299 mg per 100 g protein) and then decreased to 2.9 mg per 100 g protein at 60 minutes. For the first toasting times (0.5, 1 and 2 min) the furosine content decreased slightly. Available lysine reached losses of 50% after 25 min of heating. The toasting of bread increased HMF values from 12 to 2025 mg kg^?1 for the assay at prolonged times of heating and from 1.3 to 4.2 mg kg^?1 at reduced times (0.5–5 min). The HMF content decreased (1000 mg kg^?1) when the sliced bread was toasted until it burnt. Colour (ΔE, 100 ? L*) and absorbance at 284 and 420 nm always increased. High linear correlations (r² > 0.860) were obtained between browning indicators and time (A₂₈₄/time, A₄₂₀/time, 100 ? L*/time and HMF/time). © 2001 Society of Chemical Industry     

Evaluation of the non-enzymatic browning in thermally processed apple juice by front-face fluorescence spectroscopy

Fresh apple juice was heated at 95 °C for 30 and 60 min, and then stored for 6 days for obtaining different extent of non-enzymatic browning. Front-face fluorescence excitation–emission-matrix (EEM) with excitation at 355 and 400 nm and emission ranges of 385–600, and 430–600 nm was used to measure the juice samples. The sign test pointed out an enhanced sensitivity of EEM compared to commonly used browning indicators, such as non-enzymatic browning index (NEBI), color readings in L^∗a^∗b^∗ space, and the concentration of 5-hydroxymethylfurfural (HMF). Using the fluorescence data, the correctness of classifications of fresh juice, heated juice, and stored juice were >85%. Multivariate analyses were applied to study the relations of fluorescence emission spectra and common indicators. For predicting NEBI, b^∗, and HMF, the correlation coefficients were >0.80. Resulting, the spectroscopic analyses of fluorescent neoformed products such as HMF provide a feasible approach to monitor non-enzymatic browning of juice.     

Carbohydrate constituents of some nigerian maize varieties grown at three soil nitrogen levels

Of eight varieties of maize analysed, average values for constituent carbohydrates in g/100g dry matter were: soluble sugars, 1·61; starch, 62·04; water-soluble polysaccharides, 2·60; alkali-soluble polysaccharides, 6·85 and cellulose, 1·08. Lignin varied from 1·18 to 1·86%. Significant varietal differences (P < 0·05) were found for the carbohydrate fractions, although differences within varieties due to nitrogen fertilisation were not significant. Soluble sugars and starch, which contribute appreciably to the energy value of the maize, ranged between 56·68% for WCUI and 67·12% for Lag ABCD. Predicted digestible energy (DE) and metabolisable energy (ME) values for pigs were in the range 4005–4073 kcal/kg and 3881–3947 kcal/kg, respectively whilst metabolisable energy for poultry varied between 3692 and 4007 kcal/kg.     

Kinetics of 5-hydroxymethylfurfural formation in chinese acacia honey during heat treatment

In this paper, the 5-hydroxymethylfurfural (HMF) contents of the acacia honeys after heat treatment were determined by HPLC; the kinetics of HMF formation was also investigated. The HMF content of acacia honey was 0.38±0.01mg/kg, but rapidly increased to the maximum of 18,320.07±14.29 mg/kg at 190°C and decreased to 1,180.24±6.54 mg/kg at 230°C after heating. The HMF content increased gradually in honey samples heated in 12 h at the temperature of 80, 100, and 120°C. The apparent frequency constant was k _f =3.91×10²⁵/h, and the apparent activation energy was E _a=173.10 kJ/mol. The HMF content in the acacia honey was related to honey composition, heating temperature, and time, and the HMF formation could also be related to the initial honey pH.     

Effect of Oxygen on Thermal Degradation of 5-Methyl-5,6,7,8-Tetrahydrofolic Acid

Previous studies of thermal degradation of folic acid have not given consistent rate expressions or activation energies. The present study employed a model system which eliminated oxygen mass transfer limitations to examine degradation as a result of heating. A pseudo first-order reaction rate constant (k_365.K) and an activation energy (E_a) for thermal degradation due to an oxidative mechanism were estimated to be 0.154 ± 0.044 min^?1 and 16.3 kcal/mol, respectively. In the presence of N₂, these parameters were estimated to be 0.094 ± 0.009 min^?1 and 23.3 kcal/mol, respectively. While elimination of oxygen will not ensure folic acid retention, the overall degradation rate will be reduced significantly.     

Patulin Adsorption Kinetics on Activated Carbon, Activation Energy and Heat of Adsorption

The kinetics of adsorption of patulin on activated carbon were studied at different initial patulin concentrations (100–400 ppb) for the temperature range 20–80°C. Apparent adsorption rate constants (k_aapp) were changed from 1.07 × 10^?3 to 1.86 × 10^?3 g^?1 min^?1 while the temperature increased from 20 to 80°C. For equilibrium adsorption curves; the Langmuir model was attempted and model parameters (K and Q°) were obtained for different temperatures. Energy of activation and heat of adsorption were determined in a batch adsorption system (E_a= 2.02 kcal/mol and ΔH = 2.24 kcal/mol). The adsorption occurred endothermically and by physical mechanisms.     

Equilibration of Solutes in Nonfermenting, Brined Pickling Cucumbers

The equilibration of solutes between whole cucumbers and the brine in which they were held was found to be consistent with a diffusion-controlled first-order rate process. First-order rate coefficients for attainment of equilibrium (K_D) for sugar and malic acid (initially in cucumbers) and NaCl and lactic, tartaric, acetic and formic acids (initially in brine) varied up to threefold among four cucumber lots. However, the ratios of K_D values among solutes were not significantly different (P>0.05). K_D values increased as cucumber size decreased. Peeling increased K_D values 3.7- to 11.1-fold. Temperature dependency was greater for solute movement out of [apparent activation energies (E_a) of 6.5 and 6.3 kcal/mole for malic acid and sugar] than into (apparent E_a of 4.5 and 4.2 kcal/mole for NaCl and lactic acid) cucumbers. The equilibration-prediction model used may be helpful in studying rate limiting factors in the fermentation of brined vegetables and in other food preservation processes where solute movement is important.     

Thermal Destruction of Pteroylglutamic Acid in Buffer and Model Food Systems

First order rate constants (k) and activation energies (Ea) of pteroylglutamic acid (PteGlu) were determined between 100 and 140°C in citrate buffer (pH 3–6) and model food systems. The rate constants (hr^-1) in citrate buffer ranged from 0.145–2.36 at pH 3; 0.074–0.840 at pH 4.0; 0.021–0.207 at pH 5.0, and 0.015–0.133 at pH 6.0. Corresponding Ea values were 22.6, 19.5, 17.8, and 16.8 kcal/mole at pH 3, 4,5, and 6, respectively. In an apple juice model (pH 3.4), the rate constants ranged from 0.063–0.822 and in tomato juice model (pH 4.3), from 0.056–0.723. Ea values in apple juice an tomato juice were 20.0 and 19.7 kcal/mole, respectively.     

Kinetics of Phase Transition of Native,Cross-linked,and Hydroxypropylated Rice Starches

Kinetics of the phase transition of native and chemically modified rice starches have been investigated by using differential scanning calorimetry (DSC) after isothermal treatment. At the experimental conditions, the phase transition of these starches followed pseudo-first order kinetics. The kinetic order was not affected by the two chemical modifications used, hydroxypropylation and cross-linking, while the rate constants were altered. From the Arrhenius plot, peak temperature (T_p) from DSC thermogram appeared to be the turning point for the two steps, swelling and disruption/dissolution, associated in the phase transition of starch granules. When the temperature was below T_p high activation energy was obtained and fell in the range of 61 to 75kcal/mol. Once the temperature was above T_p, the activation energy dropped to be in the range of 10 to 30kcal/mol and the starch became less temperature sensitive.     

USE OF CLARIFYING AGENTS AND ULTRA FILTER TO DECREASE FUMARIC ACID, HMF AND INCREASE CLARITY OF APPLE JUICE

In this study, the effects of eight different processing treatments of apple juice (AJ) production (Process 1: Ultra filtration [UF], Process 2: Activated charcoal [AC], Process 3: polyvinylpolypyrolidone [PVPP], Process 4: Gelatine [G] + Bentonite [B], Process 5: [G + B] + UF, Process 6: [G + B] + AC, Process 7: [G + B] + PVPP and Process 8: [G + B] + Kieselguhr [K]) on the fumaric acid (FA), hydroxymethylfurfural (HMF), color and clearness values of AJ were investigated. With the exception of Processes 1 and 5, AC, K, PVPP, G and B were used at various doses in other processes. FA, HMF, color and clearness values of control sample were determined as 3.24 mg/L, 3.84 mg/L, 48.5 (%T) and 94.1 (%T), respectively. The highest proportional decrement in FA and HMF values of the samples were observed with Process 6 at the level of 5. The fifth level of Process 6 resulted in 35.8% (3.24–2.08 mg/L) and 35.9% (3.84 to 2.46 mg/L) reductions in FA and HMF values, respectively. On the other hand, the best improvement in clearness of AJ was obtained with Process 6 at the fourth level and obtained as 98.9 (%T).     

Thermal Kinetic Parameters of Thiamin in Wheat Flour at Temperatures Higher than 100°C

ABSTRACT: Kinetic parameters for thiamin degradation were obtained using 2 high-temperature heating methods: (1) atmospheric pressure (AP) with moisture correction and (2) controlled pressure (CP). At AP conditions, 33.3% dry basis (db) moisture wheat flour with 0.35% (db) thiamin was heated in thin steel cells isothermally at 145,160, and 172°C. To obtain the moisture correction factor, a constant-moisture study was conducted at 80°C using 6 moisture contents (6.1% to 36.9%). At CP conditions, flour at 19%, 28.2%, and 33.3% (db) moisture in double-seamed cans was heated in a CP steam retort at 129°C. For the AP method, the corrected activation energy for 33.3% moisture content was 129.5 kJ/g-mol and reaction rate at 80°C was 3.48×10⁻⁴ min⁻¹. Using the CP method, the activation energy and reaction rate were 121.0 kJ/g-mol and 9.69×10⁻⁵ min⁻¹, respectively. Results obtained from 2 methods were not statistically different. These results illustrated that the correction method could be used as an alternative for researchers without access to controlled pressure equipment and transient heat transfer software.     

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.     

Temperature Influence on Acetyllysine Interaction with Glucose in Model Systems due to Maillard Reaction

The interaction between N-α-acetyllysine and glucose was investigated in a dry cellulose matrix (1.8% moisture) at 40, 50 and 60°C and a_w 0.19-0.21. The loss in acetyllysine in 6 days at those temperatures was 22, 54, and 79%, respectively. The degradation data more clearly fit a double exponential function (Ae^BX+ Ce^DX) than the first order function, Ae^BX. An estimate of the activation energy of 36 kcal/ mol and a Q₁₀ of 5.5 was computed from second order rate constants for acetyllysine and glucose degradation. The increase in color followed zero order kinetics and indicated an activation energy of 44 kcal/mol for the presumed third phase of the Maillard reaction in the solid state.     

Energy and protein requirements of crossbred (Holstein × Gyr) growing bulls

The objective of this study was to estimate the energy and protein requirements of crossbred (Holstein × Gyr) growing bulls. Twenty-four 10-mo-old bulls [initial body weight (BW) = 184 ± 23.4 kg] were used in a comparative slaughter trial. Six bulls were slaughtered at the beginning of the experiment as the reference group, to estimate initial empty body weight (EBW) and energy and protein contents of the remaining animals. The remaining bulls were assigned to a completely randomized design with 3 levels of dry matter intake and 6 replicates. The levels of dry matter intake were 1.2% of BW, 1.8% of BW, and ad libitum to target orts equal to 5% of the total amount that was fed. The remaining bulls were slaughtered at the end of the experiment. The bulls were fed a diet consisting of 59.6% corn silage and 40.4% concentrate on a dry matter basis. The equation that determined the relationship between EBW and BW was EBW = (0.861 ± 0.0031) × BW. The relationship between empty body gain (EBG) and average daily gain (ADG) was demonstrated by the following equation: EBG = (0.934 ± 0.0111) × ADG. Net energy for maintenance (NE_M) was 74.8 ± 2.89 kcal/kg of EBW^0.75 per day, and metabolizable energy for maintenance (ME_M) was 120.8 kcal/kg of EBW^0.75 per day. The detected efficiency of use of metabolizable energy for maintenance (k_m) was 61.9%. The equation used to estimate net energy for gain (NE_G) was as follows: NE_G = (0.049 ± 0.0011) × EBW^0.75 × EBG^{0.729 ± 0.0532}. The efficiency of use of metabolizable energy for gain (k_g) was 35.7%. The metabolizable protein for maintenance (MP_M) was 3.05 g/kg of BW^0.75. The equation used to estimate net protein requirements for gain (NP_G) = (87.138 ± 65.1378 × EBG) + [(40.436 ± 21.3640) × NE_G]. The efficiency of use of metabolizable protein for gain (k) was 35.7%. We concluded that the estimates of energy and protein requirements presented herein are more appropriate than the National Research Council dairy cattle model and the Brazilian BR-CORTE system to balance the diets of crossbred (Holstein × Gyr) growing bulls.     

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.     

RHEOLOGICAL BEHAVIOUR OF CLARIFIED MANGO JUICE CONCENTRATES

The rheological behaviour of clarified mango juice was measured at temperatures 15–85C and concentrations 15–66 °Brix, using a rotoviscometer. Mango juice free of pectin and pulp behaves as a Newtonian fluid. The effect of temperature can be described by an Arrhenius-type equation. The activation energy for viscous flow was in the range of 1.64–8.44 kcal/g-mol, depending on the concentration. The effect of concentration was modelled better by an exponential relationship than a power-law relationship. Simple equations are proposed for describing the combined effect of temperature and soluble solids content on the juice viscosity.     

Determination of Mass Diffusivity of Simple Sugars in Water by the Rotating Disk Method

The rotating disk method is shown to be an accurate method for determining the mass diffusivity of solid food components in liquid solutions. The diffusivities of sucrose and glucose in water were determined to be 0.50 and 0.66 (m²/sec × 10⁹) at 25°C with activation energies of 36.3 and 31.6 kJ/g-mol, respectively.