Furan Reduction Research Articles

Formation of furan and furan derivatives in baby food products

A comprehensive analysis of 89 commercial baby food samples showed the highest levels of furan in ready-to-eat full meals and vegetable purees (12–118 μg/kg). The alkylated furans (2- and 3-methylfuran, 2-ethylfuran, 2-pentylfuran) were predominantly found in these baby food categories. Furfuryl alcohol was notably abundant in ready-to-eat cereal porridge (3,550–13,100 μg/kg). The addition of lactose to self-made cereal porridge strongly influenced the formation of furfuryl alcohol. After reheating selected commercial baby food samples, a reduction of furan by 38 %, methylfurans by 28 %, and 2-ethylfuran by 26 % has been achieved. Raw materials, vegetable varieties, and storage conditions had a major impact on furan formation, which requires an adaptation of processing parameters. The most promising mitigation of furan (by 44 %) and most furan derivatives in vegetable puree were achieved by adding the additive calcium lactate gluconate. In contrast, in cereal porridge, the formation of furfuryl alcohol was reduced by 28 %.

Post-synthesis metal (Sn, Zr, Hf) modification of BEA zeolite: Combined Lewis and Br⊘nsted acidity for cascade catalysis

Zeolites modified by Lewis acidic metal centers such as Sn, Zr, and Hf are promising catalysts for numerous reactions relevant to biorefining, such as isomerization of carbohydrates and Meerwein-Ponndorf-Verley (MPV) reduction of furans. Preferred catalysts contain these metal ions in the framework of large-pore BEA zeolite, requiring often complex multistep preparation procedures based on expensive organometallic precursors. Herein, we developed a facile approach for obtaining highly dispersed isolated Sn, Zr, and Hf incorporated in dealuminated BEA zeolite with high metal content (Si/M ratio of 50–75) via a solid-state grinding approach using simple inorganic metal precursors. The efficient incorporation of isolated metal sites in the BEA framework with high content was achieved by methanol treatment before calcination, which removes excess metal. The Lewis acid sites derive from isolated metal ions in open sites for Sn, Zr, and Hf, while Sn-modified BEA also contains closed Sn sites. The open Sn sites display the highest Lewis acidity. The Br⊘nsted acidity stems from silanols perturbed by Lewis acidic metal ions of open metal sites and the OH group connected to the open metal sites. The metal-modified zeolites are active in the cascade reductive etherification of cinnamaldehyde, involving the MPV reduction to cinnamyl alcohol and the subsequent etherification to cinnamyl propyl ether with the isopropanol solvent over Lewis and Br⊘nsted acid sites, respectively. Sn-modified BEA was the most active sample, which stems from its strongest Lewis acidity, which is crucial for the first MPV step. Sn modification of the optimized solid-state ion-exchange method was applied to various BEA zeolites with different morphologies (nanocrystalline, hierarchical, and conventional BEA), showing that pore hierarchization can further benefit cascade reductive etherification reaction.

Effects of chlorogenic acid on the formations of furan, acrylamide, α-dicarbonyls and volatile compounds in canned coffee model systems

It was demonstrated that some antioxidants, especially chlorogenic acid (CGA), can trap glyoxal and methylglyoxal, which are Maillard reaction intermediates and precursors of furan, leading to the reduction of furan. This study investigated the effects of CGA on the changes in furan, acrylamide, α-dicarbonyls, and volatile compound levels in 11 types of canned coffee model systems (CCMSs) containing sugars and amino acids after thermal treatments. Furan decreased (3.77–34.7%) in all model systems treated with CGA. However, acrylamide decreased in sugar-only models but increased in sugar/amino acid models. α-Dicarbonyls were generally reduced with CGA treatment but increased in the sucrose/asparagine model. A total of 116 volatile compounds were identified in three types of CCMSs. Overall, volatile compounds were decreased by the addition of CGA. The trapping action of CGA might affect the reduction of furan and some volatiles but exhibits conflicting results for acrylamide.

Formation and reduction of furan in pumpkin puree by precursors, antioxidants, sterilization and reheating

The formation and mitigation of furan in pumpkin puree (PP) were studied during the complete process of producing PP. The content of furan was determined using headspace solid-phase microextraction combined by GC–MS analysis. Various PP samples added with precursors (glucose, fructose, linoleic acid, linolenic acid, β-carotene, ascorbic acid, glutamic acid, alanine, and serine) showed increased furan formation (30.81 ∼ 94.45 µg/kg) compared with the control (30.81 µg/kg), with β-carotene resulting in the formation of the largest amount of furan. The effects of antioxidants, such as caffeic acid, chlorogenic acid, quercetin, and butylated hydroxytoluene, on the reduction of furan in PP containing β-carotene were also investigated. All antioxidants showed significant reduction of furan. During sterilizing, the content of furan was considerably affected by temperature but not heating time. Reheating PP samples using a microwave oven, water bath, or open pot, revealed that open-pot reheating was the most effective for reducing furan (10.28 ∼ 11.72 µg/kg).

Formation of furan in baby food products: Identification and technical challenges

Furan is generally produced during thermal processing of various foods including baked, fried, and roasted food items such as cereal products, coffee, canned, and jarred prepared foods as well as in baby foods. Furan is a toxic and carcinogenic compound to humans and may be a vital hazard to infants and babies. Furan could be formed in foods through thermal degradation of carbohydrates, dissociation of amino acids, and oxidation of polyunsaturated fatty acids. The detection of furan in food products is difficult due to its high volatility and low molecular weight. Headspace solid-phase microextraction coupled with gas chromatography/mass spectrometer (GC/MS) is generally used for analysis of furan in food samples. The risk assessment of furan can be characterized using margin of exposure approach (MOE). Conventional strategies including cooking in open vessels, reheating of commercially processed foods with stirring, and physical removal using vacuum treatment have remained unsuccessful for the removal of furan due to the complex production mechanisms and possible precursors of furan. The innovative food-processing technologies such as high-pressure processing (HPP), high-pressure thermal sterilization (HPTS), and Ohmic heating have been adapted for the reduction of furan levels in baby foods. But in recent years, only HPP has gained interest due to successful reduction of furan because of its nonthermal mechanism. HPP-treated baby food products are commercially available from different food companies. This review summarizes the mechanism involved in the formation of furan in foods, its toxicity, and identification in infant foods and presents a solution for limiting its formation, occurrence, and retention using novel strategies.

Effects of hydroxycinnamic acids on the reduction of furan and α-dicarbonyl compounds

The effects of hydroxycinnamic acids such as cinnamic acid (CNA), p-coumaric acid(CMA), caffeic acid (CFA), and chlorogenic acid (CGA) on the reduction of furan in canned-coffee model systems (CCMS) containing α-dicarbonyls [glyoxal (GO) or methylglyoxal (MGO)] were investigated. The concentration of furan in CCMS containing GO, which was 59.76 μg/L, was reduced by the addition of CFA and CGA to 48.31 μg/L and 41.38 μg/L, respectively; similarly, the furan concentration in model system containing MGO was 45.79 μg/L, and this decreased to 35.41 μg/L (by CFA) and 32.65 μg/L (by CGA), respectively. In addition, the effects of hydroxycinnamic acids on the trapping of GO and MGO were determined. CFA and CGA greatly reduced the concentration of GO to 303.51 μg/L and 267.80 μg/L, respectively (compared to 515.79 μg/L in the control), whereas that of MGO was decreased to 207.01 μg/L and 219.14 μg/L (compared to 417.14 μg/L in the control). The trapping of α-dicarbonyls such as GO and MGO by CFA and CGA could be closely related to furan reduction in CCMS.

Furan formation from ingredient interactions and furan mitigation by sugar alcohols and antioxidants of bamboo leaves in milk beverage model systems.

Furan is a potential carcinogen that can be formed in various heat-treated foods, including milk beverages. Studies on the formation and mitigation of furan in milk beverages are rare. In the present study, the effects of ingredients on furan formation and the reduction of furan by sugar alcohols and antioxidants of bamboo leaves (AOB) were investigated in a milk beverage model system. The results obtained demonstrated that the Maillard reaction is the major pathway for furan formation in a milk beverage model system, and the type of sugar has a great influence on furan formation. High fructose corn syrup (HFCS 55) was more favorable for furan formation than sucrose. Thermal oxidation of ascorbic acid and lipids significantly enhanced furan generation. Xylitol, sorbitol and mannitol inhibited furan formation in model systems by replacing sucrose or HFCS. The maximum inhibition percentage of furan formation was observed when sucrose/HFCS was substituted completely by xylitol and the inhibition rate was 78.28% and 88.64% separately for the sucrose/HFCS-containing system. AOB significantly inhibited furan formation and the inhibition rate reached 32.13% and 28.52% separately for the sucrose/HFCS-containing system. The present study demonstrates that the use of sugar alcohols and AOB could be a feasible way of reducing furan formation in thermally processed milk beverages. © 2019 Society of Chemical Industry.

Furan Levels and Sensory Profiles of Commercial Coffee Products Under Various Handling Conditions.

Consumption of coffee has increased rapidly in Korea over the past few years. Consequently, the probability of exposure to chemical hazards presence in coffee products increases. Furan is a heterocyclic compound, formed mainly from Maillard reaction, therefore present in coffee products. This work demonstrated the strategy to reduce the levels of furan in coffee products at individual consumer level, by investigating the levels of furan served in common handling scenarios of coffee in Korea: canned coffee, instant coffee, and brewed coffee. Findings of this study can practically guide industry, government, and consumer agencies to reduce the risk exposure to furan during coffee consumptions.

Effect of oxygen availability and pH on the furan concentration formed during thermal preservation of plant-based foods

ABSTRACTThermally treated fruit- and vegetable-based foods are important contributors to the furan exposure of children and adults. Furan reduction by adding or removing precursors from the product has proven to be challenging because of major food constituents and interactions involved in the reaction pathways leading to furan formation. Instead of intervening at the precursor level, it might be more feasible to influence these formation pathways by adjusting the matrix properties of the product. As opposed to many previous literature sources, the present study investigated the effects of oxygen availability (normal versus reduced) and pH (acid versus low acid) on the furan formation in a real food system. Different combinations of both matrix properties were prepared in a reconstituted potato purée and subjected to a thermal treatment with a pasteurisation or sterilisation intensity. Irrespective of the addition of the furan precursors ascorbic acid, fructose and fatty acids, a considerable furan reduction was observed for the sterilised purées (F12110 = 15 min) with either a reduced oxygen availability (0.1–1.8 mg l–1) or at pH 3. The effects of both matrix properties were less pronounced in the pasteurised purées (P9010 = 10 min), because of the lower furan concentrations. Even though the mechanisms of furan reduction for both types of matrix properties could not be fully elucidated, the results showed that lowering the oxygen concentration or pH prior to thermal processing offers a powerful, additional strategy for furan mitigation in thermally treated plant-based foods.

Relative importance and interactions of furan precursors in sterilised, vegetable-based food systems

ABSTRACTMitigation strategies aimed at an intervention in the reaction pathways for furan formation (e.g., by adjusting precursor concentrations) might offer an additional route for furan reduction in sterilised, vegetable-based foods, without adverse effects on other food safety or quality attributes. As a first step towards product reformulation, the aim of the present study was to determine the relative importance and interactions of possible furan precursors in these types of foods. Based on an I-optimal experimental design, potato purée (naturally low in furan precursors) was spiked with known amounts of sugars, ascorbic acid, olive oil and β-carotene, and subjected to a thermal sterilisation. Significant correlations were observed between furan concentrations after thermal treatment and starting concentrations of ascorbic acid and monosaccharides (i.e., fructose and glucose). Ascorbic acid had a clear furan-reducing effect as an antioxidant by protecting (polyunsaturated) fatty acids against oxidative degradation. Fructose and glucose were the main precursors, which can most probably be attributed to their high, but realistic, concentrations in the product. The contributions of fatty acids and β-carotene were strongly dependent on redox interactions with other food constituents. In the same potato purées, only low concentrations (0–2 ng g–1 purée) of 2-methylfuran were detected, indicating that the direct importance of the spiked food constituents as a precursor for methylfuran formation was rather small. Based on the results of this study, reducing the amount of monosaccharides or adjusting the redox conditions of the matrix are suggested as two possible approaches for furan mitigation on the product side.

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Furan (C4H4O) is a volatile compound formed mostly during the thermal processing of foods. The toxicity of furan has been well documented previously, and it was classified as “possible human carcinogen (Group 2B)” by the International Agency for Research on Cancer. Various pathways have been reported for the formation of furan, that is, thermal degradation and/or thermal rearrangement of carbohydrates in the presence of amino acids, thermal degradation of certain amino acids, including aspartic acid, threonine, α-alanine, serine, and cysteine, oxidation of ascorbic acid at higher temperatures, and oxidation of polyunsaturated fatty acids and carotenoids. Owing to the complexity of the formation mechanism, a vast number of studies have been published on monitoring furan in commercial food products and on the potential strategies for reducing furan. Thus, we present a comprehensive review on the current status of commercial food monitoring databases and the possible furan reduction methods. Additionally, we review analytical methods for furan detection and the toxicity of furan.

Furan formation as a function of pressure, temperature and time conditions in spinach purée

In recent studies, innovative high-pressure high-temperature processing (HPHT) has presented itself as an interesting alternative for furan reduction in sterilized, vegetable-based foods. In order to explain the observed furan reduction following HPHT treatment, furan formation was studied under a range of pressure, temperature and time conditions, using spinach purée as a case study. For all the treatments, no furan was detected during the dynamic heating-up phase, followed by a steady increase in furan concentrations at isothermal(-isobaric) conditions. The increase in furan concentrations at isothermal(-isobaric) treatment conditions could be adequately described by an empirical, zero-order model. A pressure level of 600 MPa did not affect the rate of furan formation in spinach purée, as opposed to the processing temperature and time. As a result, the reduced furan concentrations for HPHT processing could be explained by the faster heating and cooling rates, resulting in shorter processing times as compared with conventional retort processing.

Formation and reduction of furan in a soy sauce model system

The formation and reduction of furan using a soy sauce model system were investigated in the present study. The concentration of furan fermented up to 30days increased by 211% after sterilization compared to without sterilization. Regarding fermentation temperature, furan level after 30days’ fermentation was the highest at 30°C (86.21ng/mL). The furan levels in the soy sauce fermentation at 20°C and 40°C were reduced by 45% and 88%, respectively compared to 30°C fermentation. Five metal ions (iron sulfate, zinc sulfate, manganese sulfate, magnesium sulfate, and calcium sulfate), sodium sulfite, ascorbic acid, dibutyl hydroxyl toluene (BHT), and butylated hydroxyanisole (BHA) were added in a soy sauce model system. The addition of metal ions such as magnesium sulfate and calcium sulfate reduced the furan concentration significantly by 36–90% and 27–91%, respectively in comparison to furan level in the control sample (p<0.05). Iron sulfate and ascorbic acid increased the furan level at 30days’ fermentation in the soy sauce model system by 278% and 87%, respectively. In the case of the BHT and BHA, furan formation generally was reduced in the soy sauce model system by 84%, 56%, respectively.

The impact of high pressure thermal sterilization on the microbiological stability and formation of food processing contaminants in selected fish systems and baby food puree at pilot scale

To this day there is no implementation of the high pressure thermal sterilization (HPTS) in the food industry. HPTS could result in better food quality, lower thermal load applied to the product and less unwanted food processing contaminants (FPCs) such as furan.Based on findings for selected foods at lab-scale extrapolated temperature-time combinations for a 12 log10 inactivation of Bacillus amyloliquefaciens were chosen for a scale-up with a 55 L vessel (HPHT system Hiperbaric). Temperature-time-combinations at 600 MPa were between 100 and 115 °C and 0.45–28min. The scale-up resulted in a reduction of furan, depending on the food system, between 41 and 98% to retorting. Results at pilot scale were similar to lab-scale experiments. The performed storage trials (standardized method NF V 08-408) showed that only for the baby food puree two selected treatment conditions (107.5 °C, 9.8 min and 115 °C, 0.45 min at 600 MPa) resulted in an unstable product. Overall the results of the scale-up process support the idea that the HPTS could be feasible for the implementation in the food industry.

Formation and reduction of furan in maillard reaction model systems consisting of various sugars/amino acids/furan precursors.

To investigate the effect of the temperature on the formation of furan, various furan models were conducted at 90, 121, and 150 °C. A total 15 models, including alanine (ALA), serine (SER), ribose (RIB), RIB/ALA, RIB/SER, glucose (GLU), GLU/ALA, GLU/SER, sucrose (SUC), SUC/ALA, SUC/SER, furoic acid (FUR), GLU/FUR, acetaldehyde (ACET), and GLU/ACET, were prepared. The maximum level of furan was detected in the GLU/SER and GLU/ALA models at a molar ratio of 0.5:0.5. The formation of furan was proportional to the temperature in all models. The RIB/SER model generated the greatest amount of furan among the 11 models ranging from 2.1 to 4931.9 ng mL(-1) under all temperature conditions. Among the precursor models, the FUR model formed the greatest amount of furan ranging from 1058.2 to 13 927.9 ng mL(-1) at all temperatures.

Reduction of Furan Formation by High-Pressure High-Temperature Treatment of Individual Vegetable Purées

The present study addressed the need for furan mitigation measures at the level of food production, where the effects of extrinsic (process-related) and intrinsic (product-related) properties on furan formation in vegetable-based systems were investigated. For the first time in the literature, the effect of high-pressure high-temperature (HPHT) processing on the formation of furan was demonstrated. HPHT processing was proven to be an interesting alternative for furan reduction in vegetable-based systems, when aiming for sterilization intensities. Following HPHT treatment, the furan concentrations of a wide range of individual vegetable purées dropped to levels close to the analytical limits (1–2 ng/g purée). A higher processing cost might limit the use of HPHT processing to high-value added products, which means that for many other conduction-heated food products, conventional heating would remain the standard technology. As a first step towards control of furan formation in the latter products, a mixed model regression was used to identify the major precursors in vegetable-based systems. Significant correlations were observed for vitamin C and sugars, which were attributed to the efficiency of the conversion and high concentrations, respectively. Next to furan, the HPHT- and thermally treated purées were analyzed for 2- and 3-methylfuran, which are likely to undergo the same metabolic fate as furan. For most of the vegetables tested, the total amount of methylfuran found in the thermally treated purées could not be ignored. Similarly to furan, there was a clear reduction in the concentrations found in the HPHT-treated purées.

Genetic changes that increase 5-hydroxymethyl furfural resistance in ethanol-producing Escherichia coli LY180

The ability of a biocatalyst to tolerate furan inhibitors present in hemicellulose hydrolysates is important for the production of renewable chemicals. This study shows EMFR9, a furfural-tolerant mutant of ethanologenic E. coli LY180, has also acquired tolerance to 5-hydroxymethyl furfural (5-HMF). The mechanism of action of 5-HMF and furfural appear similar. Furan tolerance results primarily from lower expression of yqhD and dkgA, two furan reductases with a low Km for NADPH. Furan tolerance was also increased by adding plasmids encoding a NADPH/NADH transhydrogenase (pntAB). Together, these results support the hypothesis that the NADPH-dependent reduction of furans by YqhD and DkgA inhibits growth by competing with biosynthesis for this limiting cofactor.

Risk assessment of furan in commercially jarred baby foods, including insights into its occurrence and formation in freshly home-cooked foods for infants and young children

Furan is a possible human carcinogen (IARC group 2B) with widespread occurrence in many types of foods. In this study, a survey of furan contamination in 230 commercially jarred ready-to-eat infant food products was conducted using headspace sampling in combination with gas chromatography and mass spectrometry (HS-GC/MS) with a detection limit of 0.2 µg kg−1. The incidence of furan contamination in jarred infant beverages, cereals and fruits was relatively low, with average concentrations below 10 µg kg−1. Significantly higher concentrations were found in pasta (34.8 ± 14.5 µg kg−1), meals containing meat (28.2 ± 15.0 µg kg−1), and meals containing vegetables (31.2 ± 17.3 µg kg−1). The average exposure of 6-month-old infants to furan was estimated to be 0.2 µg per kg bodyweight per day. The margin of exposure calculated using the T25 dose descriptor would be 2692, which points to a possible public health risk. In contrast to commercially jarred food products, none of 20 freshly home-prepared baby foods contained furan above the limit of detection. Only after re-heating in closed vessels was furan found to have formed. Furan was especially prevalent in reheated foods containing potatoes, with values ranging between 2.3 and 29.2 µg kg−1. The formation of furan in potato-containing baby foods was increased by addition of ascorbic acid, by longer heating times above 1 h and by temperatures above 50°C. Research regarding reduction of furan in commercial baby foods should be conducted, with a priority aimed at reducing this heat-induced contaminant without concomitantly increasing the microbiological risk.

Effectiveness of Ionizing Radiation in Reducing Furan and Acrylamide Levels in Foods

Furan and acrylamide are two possible carcinogens commonly found in many thermally processed foods. The possibility of using ionizing radiation to reduce the levels of thermally induced furan and acrylamide in water and selected foods was investigated. Aqueous furan solutions, and foods (frankfurters, sausages, infant sweet potatoes) that contained furan were irradiated to various doses of gamma-rays. Water and oil spiked with acrylamide and potato chips (a known acrylamide-containing food) were also irradiated. In addition, possible irradiation-induced formation of acrylamide in glucose and asparagine solutions was analyzed. Results showed that irradiation at 1.0 kGy destroyed almost all furan in water. In frankfurters, sausages, and infant sweet potatoes, the rate of irradiation-induced destruction of furan was much lower than the rate in water, although significant reductions in furan levels were observed in all foods. Irradiation at 2.5-3.5 kGy, doses that can inactivate 5-log of most common pathogens, reduced furan levels in the food samples by 25-40%. Similarly to furan, acrylamide in water was also sensitive to irradiation. After 1.5 kGy of irradiation, most of the acrylamide was degraded. Irradiation, however, had a very limited effect on acrylamide levels in oil and in potato chips, even at a dose of 10 kGy. No detectable acrylamide was formed in the mixture of asparagine and glucose upon irradiation. These results suggest that a low dose of irradiation easily destroys furan and acrylamide in water. In real foods, however, the reduction of furan was less effective than in water, whereas the reduction in acrylamide was minimal.

Effects of Ca(OH)2 treatments (“overliming”) on the composition and toxicity of bagasse hemicellulose hydrolysates

Hemicellulose syrups from dilute sulfuric acid hydrolysates of hemicellulose contain inhibitors that prevent efficient fermentation by yeast or bacteria. It is well known that the toxicity of these hydrolysate syrups can be ameliorated by optimized “overliming” with Ca(OH)2. We have investigated the optimization of overliming treatments for sugar cane bagasse hydrolysates (primarily pentose sugars) using recombinant Escherichia coli LY01 as the biocatalyst. A comparison of composition before and after optimal overliming revealed a substantial reduction in furfural, hydroxymethylfurfural, and three unidentified high-performance liquid chromatography (HPLC) peaks. Organic acids (acetic, formic, levulinic) were not affected. Similar changes have been reported after overliming of spruce hemicellulose hydrolysates (Larsson et al., 1999). Our studies further demonstrated that the extent of furan reduction correlated with increasing fermentability. However, furan reduction was not the sole cause for reduced toxicity. After optimal overliming, bagasse hydrolysate was rapidly and efficiently fermented (>90% yield) by LY01. During these studies, titration, and conductivity were found to be in excellent agreement as methods to estimate sulfuric acid content. Titration was also found to provide an estimate of total organic acids in hydrolysate, which agreed well with the sum of acetic, levulinic, and formic acids obtained by HPLC. Titration of acids, measurement of pH before and after treatment, and furan analyses are proposed as relatively simple methods to monitor the reproducibility of hydrolysate preparations and the effectiveness of overliming treatments. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 69: 526–536, 2000.