Degradation of 5-hydroxymethylfurfural during yeast fermentation

5-Hydroxymethyl furfural (HMF) may occur in malt in high quantities depending on roasting conditions. However, the HMF content of different types of beers is relatively low, indicating its potential for degradation during fermentation. This study investigates the degradation kinetics of HMF in wort during fermentation by Saccharomyces cerevisiae. The results indicated that HMF decreased exponentially as fermentation progressed. The first-order degradation rate of HMF was 0.693?×?10^?2 and 1.397?×?10^–2?min^?1 for wort and sweet wort, respectively, indicating that sugar enhances the activity of yeasts. In wort, HMF was converted into hydroxymethyl furfuryl alcohol by yeasts with a high yield (79–84% conversion). Glucose and fructose were utilised more rapidly by the yeasts in dark roasted malt than in pale malt (p?<?0.05). The conversion of HMF into hydroxymethyl furfuryl alcohol seems to be a primary activity of yeast cells, and presence of sugars in the fermentation medium increases this activity.     

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.     

Direct conversion of starch to hydroxymethylfurfural in the presence of an ionic liquid with metal chloride

Starch can be exploited as an abundant resource for sustainable production of diverse chemical intermediates such as hydroxymethylfurfural (HMF). We present a simple process of producing HMF from starches using an ionic liquid, 1‐octyl‐3‐methylimidazolium chloride ([OMIM]Cl), and CrCl₂ catalyst. The addition of HCl and CrCl₂ significantly affected the yields of HMF on the whole. CrCl₂ increased the yields of HMF by approximately two‐folds on average. The synthesis of HMF was most effective between 60 and 90 min reaction time at both concentrations of 0.3 and 0.5 M HCl. Starch concentration had influence on the productivity of HMF. At 20% starch concentration with 0.3 and 0.5 M HCl, its productivity was greatest (2.8 folds high). Eight starch sources (corn, wheat, rice, potato tuber, sweet potato, tapioca, acorn, and kudzu starch) were tested for the synthesis of HMF. The highest yields of HMF (73.0 ± 3.8 wt%) were obtained in tapioca starch dissolved in 0.5 M HCl.     

Degumming of eri silk using ionic liquids and optimization through response surface methodology

The application of imidazolium ionic liquids (ILs) as green material for degumming of silk has been investigated. In this study, degumming of eri silk was attempted using ILs 1-butyl-3-methylimidazolium chloride [BMIM]Cl and 1-butyl-3-methylimidazolium hydrogen sulphate [BMIM]HSO₄, synthesized in the laboratory. The molecular structures of the ILs were confirmed by FTIR, ¹H-NMR, and ¹³C-NMR. The thermal properties and solubility were also analysed. Experiments were designed to find out the optimum processing parameters for degumming of eri silk by response surface methodology. The statistical software, Design-Expert 6.0, was used for regression analysis and graphical analysis of the responses obtained by running the set of designed experiments. Analysis of variance was used to estimate the statistical parameters. The polynomial equation of quadratic order was employed to fit the experimental data. The quality and model terms were evaluated by F-test. Three-dimensional surface plots were prepared to study the effect of variables on different responses. The comparison of responses obtained from the experiments of highest desirability with those obtained by alkaline H₂O₂ (control) indicates that ILs give better results in terms of weight loss and absorbency.     

Rate-Controlling Mechanisms in the Photo-degradation of 5-Hydroxymethylfurfural

Rate-controlling mechanisms in the photo-degradation of 5-hydroxymethylfurfural (HMF) were studied applying kinetic and thermodynamic compensations. Aqueous solutions of HMF were prepared at a concentration of 100 mg L^?1 and at pH values of 3, 3.4, 4, and 5. The UV irradiation of samples was performed in an installation consisting of a black chamber containing the reactor and a mid-pressure mercury lamp with emission wavelengths between 250 and 740 nm. Every sample was irradiated at 12, 25, 35, and 45 °C for 120 min, analyzing their HMF content each 10 min. The photo-degradation data fitted well to zero-order kinetic model, and the constant values were used to study whether the kinetic and thermodynamic compensation could be applied. The isokinetic temperature was very similar for kinetic compensation (T_B?=?278.0 K) and thermodynamic compensation (T_B?=?277.8 K). Applying the Leffler’s criterion, the HMF photo-degradation was entropically controlled, probably as a consequence of hydrophobic interactions. In order to check the entropical control, two experiments were repeated at pH 3 but avoiding agitation. As the new obtained kinetic constants were highly different from the values previously obtained using agitation, it can be concluded that the HMF photo-degradation is an entropy-controlled process and can be speeded up by changing non-thermal parameters, like agitation.     

Ionic liquid-modified countercurrent chromatographic isolation of high-purity delphinidin-3-rutinoside from eggplant peel

Delphinidin-3-rutinoside, a high-value of anthocyanin, was isolated and purified by ionic liquid (IL)-modified countercurrent chromatography (CCC) from waste peel of eggplant (Solanum melongena), one of the most common vegetables consumed all around the world. Different conventional CCC and IL-CCC solvent systems were evaluated in respect of partition coefficient (K), separation factor (α), and stationary phase retention factor (S_f) to separate polar target and other components. Basic solvent system, kind of ILs, and amount of ILs were systematically optimized by totally K-targeted strategy, which drastically reduced the experimental effort. Finally, a novel CCC two-phase solvent system (methyl tert-butyl ether–butanol–acetonitrile–1% trifluoroacetic acid water–1-butyl-3-methylimidazolium hexafluorophosphate ([C₄MIM][PF₆]) [2:4:1:5:0.2; v/v/v/v/v]) was successfully established and applied. The baseline separation of target fraction was obtained in one cycle process. The purity of delphinidin-3-rutinoside was over 99%. Moreover, the distribution behavior of different kinds of ILs in biphasic solvent system and the removal method of ILs were explored. The results showed that hydrophobic IL significantly improved the partition of polar anthocyanin in organic solvent system, thereby the separation resolution and stationary phase retention through introducing intermolecular forces. This IL-modified CCC strategy may be applied for the separation of other anthocyanins from variety of natural food resources and waste.     

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     

Nonenzymatic browning reactions of retro-aldol degradation products of carbohydrates

 Methylglyoxal and glyceraldehyde were used to demonstrate the involvement of retro-aldol degradation products of carbohydrates in browning (A ₄₂₀), the formation of hydroxymethylfurfural (HMF), and the extent to which the mechanism of browning proceeds by homolytic or heterolytic pathways in the caramelization and Maillard reactions of mono- and disaccharides. The amino component of Maillard systems is required for the retro-aldol cleavage of D-glucose. The short-chain α-dicarbonyl compounds so formed appear to dominate not only the formation of brown products but also the mechanism of the browning of D-glucose under these conditions, even if only small amounts are formed. Evidence is presented to link the formation of free radicals in the browning of glucose to reactions of the retro-aldol products. A novel reaction pathway is suggested for the formation of HMF from glyceraldehyde. Received: 9 October 1998 / Revised version: 15 December 1998     

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.     

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.     

Controlling hydrothermal reaction pathways to improve acetic acid production from carbohydrate biomass

A two-step hydrothermal process to improve the production of acetic acid was discussed. The first step was to accelerate the formation of 5-hydroxymethyl-2-furaldehyde (HMF), 2-furaldehyde (2-FA), and lactic acid (LA), and the second step was to further convert the furans (HMF, 2-FA) and LA produced in the first step to acetic acid by oxidation with newly supplied oxygen. The acetic acid obtained by the two-step process had not only a high yield but also better purity. The contribution of two pathways via furans and LA in the two-step process to convert carbohydrates into acetic acid was roughly estimated as 85-90%, and the ratio of the contributions of furans and LA to yield acetic acid was estimated as 2:1. The fact that WO of carbohydrates is not capable of producing a large amount of acetic acid, while the two-step process can enhance the acetic acid yield, can be explained because formic acid is a basic product of direct oxidation of carbohydrate, and acetic acid in WO of carbohydrates may come from the oxidation of dehydration products of aldose.     

Assessment of hydroxymethylfurfural intake in the Spanish diet

Estimation of hydroxymethylfurfural (HMF) exposure of the Spanish population from heat-processed food was performed. HMF levels in Spanish foods were obtained from the data previously published in peer-reviewed papers; in addition, it was identified which food categories contributed significantly to HMF exposure. The potential HMF exposure was calculated for three different scenarios by using individual food intakes and the minimum (scenario 1), median (scenario 2) and maximum (scenario 3) values of analytical data on the HMF content in foods. A mean HMF intake of 10 mg day^?1 (corresponding to scenario 2) was obtained, which is only ten-fold lower than the tolerable daily intake. Coffee and bread are the most important food items that contribute nearly 85% to the total HMF daily exposure, although biscuits, breakfast cereals, beer, UHT milk and tomato products are also important for HMF exposure.     

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.     

Degumming of Tasar silk using imidazolium-based ionic liquids

Abstract

In the present work, degumming of Tasar silk was carried out using novel reagents, the ionic liquids (ILs), 1-butyl-3-methylimidazolium chloride [BMIM]Cl and 1-butyl-3-methyl-imidazolium hydrogen sulphate [BMIM]HSO₄.The results on weight loss, tensile strength loss and absorbency were compared with soda ash-H₂O₂ method. These treatments were carried out under conventional heating, sonication and microwave irradiation as different techniques of energy input. The ILs showed higher weight loss and absorbency with negligible strength loss as compared to the soda ash-H₂O₂ method, [BMIM]Cl being the most effective with further advantage of working at nearly neutral pH. The treatments under sonication and microwave showed increasingly higher efficiency as compared to the conventional heating. The chemical structure of Tasar silk, as estimated by FTIR spectroscopy, and the crystalline structure, as elucidated by X-ray diffraction, remained unchanged. SEM images showed that the surface of Tasar silk degummed with ILs was smoother. The dye uptake was nearly the same for all degummed samples. A further advantage is accrued by recyclability of ILs, which makes the process cost effective.     

Degradation of 5-hydroxymethylfurfural during yeast fermentation

5-Hydroxymethyl furfural (HMF) may occur in malt in high quantities depending on roasting conditions. However, the HMF content of different types of beers is relatively low, indicating its potential for degradation during fermentation. This study investigates the degradation kinetics of HMF in wort during fermentation by Saccharomyces cerevisiae. The results indicated that HMF decreased exponentially as fermentation progressed. The first-order degradation rate of HMF was 0.693 × 10(-2) and 1.397 × 10(-2)min(-1) for wort and sweet wort, respectively, indicating that sugar enhances the activity of yeasts. In wort, HMF was converted into hydroxymethyl furfuryl alcohol by yeasts with a high yield (79-84% conversion). Glucose and fructose were utilised more rapidly by the yeasts in dark roasted malt than in pale malt (p<0.05). The conversion of HMF into hydroxymethyl furfuryl alcohol seems to be a primary activity of yeast cells, and presence of sugars in the fermentation medium increases this activity.     

A comparison study between antioxidant and mutagenic properties of cysteine glucose-derived Maillard reaction products and neoformed products from heated cysteine and hydroxymethylfurfural

It was previously reported that Maillard reaction products (MRP) obtained from glucose with cysteine (1 M/0.25 M) mixtures and compounds generated during the mixing of heated cysteine with HMF solutions (Mix) were prone to inactivate various vegetal polyphenoloxidases (PPO). In this study, antioxidant properties of these model systems were compared using in vitro assays (AAPH°, DPPH° and TMM tests). Results showed that antioxidant activity observed in MRP and the Mix could be attributed to the sulfhydryl group of cysteine. The Mix behaved like a non-competitive inhibitor towards eggplant PPO (K_i = 0.7 μM). A highly active fraction, devoid of thiol compound and HMF, was obtained after fractionation of the Mix by SPE. The Mix was as efficient as metabisulfite in preventing enzymatic browning of apple puree (CIE-La^∗b^∗). MRP, the Mix and HMF could not be considered as mutagenic in the Salmonella microsome assay using Salmonella typhimurium TA98 and 102 strains.     

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.     

High-intensity ultrasound assisted-emulsification using ionic liquids as novel naturally-derived emulsifiers for food industry applications

Over the last decade, conscious food consumption has been revolutionizing the food industry. The search for additives that meet concepts of naturalness, healthiness and sustainability represents one of the major challenges in food industry. The development of emulsifiers in the ionic liquid (IL) form using compounds that can be obtained from natural sources to replace conventional ones is a promising approach. In this work, we have reported the application of bio-based ILs derived from fatty acids (FAs) and choline (Ch) as novel emulsifiers to produce potential food-grade oil-in-water emulsions by pre-mixing (PM) or PM followed by high-intensity ultrasound (HIUS)-assisted process (PM + U). The effects of the type of IL, considering molecular structures of FAs (C₁₈OOH or C_18:1OOH) and vegetable oil concentration (30:70 or 70:30, oil:water ratio) to form and stabilize emulsions were evaluated. The study was focused on the following aspects: synthesis and characterization of ILs, and kinetic stability, droplet size and size distribution, optical microscopy, viscosity profile and rheological behavior of the emulsions. ILs presented high emulsifier ability, since some emulsions were stable after storage time of at least 30 days, being such stability related to the type of IL, oil concentration and emulsifying process. The observed behavior was associated to lower droplet size and/or emulsion viscosity. [Ch][C₁₈OO] presented higher emulsifier ability than [Ch][C_18:1OO], and this behavior was more evident at higher oil concentration. Emulsions obtained by PM presented phase separation after their preparation, whereas most of those prepared by PM + U were visually stable, being those containing higher oil concentration the formulations that presented higher viscoelasticity, with a gel like behavior. Therefore, bio-based ILs have promising application potential as emulsifiers, and their use to obtain high stable emulsions can be enhanced by using the HIUS technique.     

Furfurals removal from roasted coffee powder by vacuum treatment

The possibility of removing 5-hydroxymethylfurfural (HMF) and furfural from roasted coffee by application of vacuum treatments was studied. In particular, different combinations of pressure and time were used. Results showed that the vacuum treatment was ineffective in removing HMF and furfural from anhydrous (commercial) coffee powder, while it proved effective if applied to previously hydrated samples. Besides, the hydration step alone was responsible for furfurals removal, although prolonged times were needed. By applying a hydration step up to a_w 0.7, followed by a vacuum treatment at 2.7 kPa and 60 °C for 10 min, 20% and 100% HMF and furfural removals were achieved, respectively. These differences in the percentages of HMF and furfural removal can be attributed to differences in the chemical and physical properties of the two molecules. However, the vacuum treatments caused a significant decrease in the coffee headspace total volatiles that in turn was responsible for a lower odour intensity of the samples. Therefore further studies are needed to reveal process conditions able to minimise the loss of sensory properties, making this technology a reliable strategy to mitigate the furfural contents in coffee.