A comprehensive review of furan in foods: From dietary exposures and in vivo metabolism to mitigation measures

Furan is a thermal food processing contaminant that is ubiquitous in various food products such as coffee, canned and jarred foods, and cereals. A comprehensive summary of research progress on furan is presented in this review, including discussion of (i) formation pathways, (ii) occurrence and dietary exposures, (iii) analytical techniques, (iv) toxicities, (v) metabolism and metabolites, (vi) risk assessment, (vii) potential biomarkers, and (viii) mitigation measures. Dietary exposure to furan varies among different countries and age groups. Furan acts through various toxicological pathways mediated by its primary metabolite, cis-2-butene-1,4-dial (BDA). BDA can readily react with glutathione, amino acids, biogenic amines, or nucleotides to form corresponding metabolites, some of which have been proposed as potential biomarkers of exposure to furan. Present risk assessment of furan mainly employed the margin of exposure approach. Given the widespread occurrence of furan in foods and its harmful health effects, mitigating furan levels in foods or exploring potential dietary supplements to protect against furan toxicity is necessary for the benefit of food safety and public health.     

Quality-Related Enzymes in Fruit and Vegetable Products: Effects of Novel Food Processing Technologies,Part 1: High-Pressure Processing

The activity of endogenous deteriorative enzymes together with microbial growth (with associated enzymatic activity) and/or other non-enzymatic (usually oxidative) reactions considerably shorten the shelf life of fruits and vegetable products. Thermal processing is commonly used by the food industry for enzyme and microbial inactivation and is generally effective in this regard. However, thermal processing may cause undesirable changes in product's sensory as well as nutritional attributes. Over the last 20 years, there has been a great deal of interest shown by both the food industry and academia in exploring alternative food processing technologies that use minimal heat and/or preservatives. One of the technologies that have been investigated in this context is high-pressure processing (HPP). This review deals with HPP focusing on its effectiveness for controlling quality-degrading enzymes in horticultural products. The scientific literature on the effects of HPP on plant enzymes, mechanism of action, and intrinsic and extrinsic factors that influence the effectiveness of HPP for controlling plant enzymes is critically reviewed. HPP inactivates vegetative microbial cells at ambient temperature conditions, resulting in a very high retention of the nutritional and sensory characteristics of the fresh product. Enzymes such as polyphenol oxidase (PPO), peroxidase (POD), and pectin methylesterase (PME) are highly resistant to HPP and are at most partially inactivated under commercially feasible conditions, although their sensitivity towards pressure depends on their origin as well as their environment. Polygalacturonase (PG) and lipoxygenase (LOX) on the other hand are relatively more pressure sensitive and can be substantially inactivated by HPP at commercially feasible conditions. The retention and activation of enzymes such as PME by HPP can be beneficially used for improving the texture and other quality attributes of processed horticultural products as well as for creating novel structures that are not feasible with thermal processing.     

Ohmic heating: A promising technology to reduce furan formation in sterilized vegetable and vegetable/meat baby foods

Occurrence of furan, classified as carcinogen 2B by the International Agency for Research on Cancer, in heat-processed foods, especially sterilized baby foods, is of a health concern. On this account, innovative processing practices ensuring microbial safety, acceptable sensorial features, and, at the same time, minimizing furan formation have to be searched. In this study, the potential of ohmic heating to mitigate furan formation was demonstrated. Compared to conventional retort sterilization, significant mitigation (70–90%) of furan was achieved, assumingly due to reduced degradation of furan precursor under faster terms heating conditions. In purees containing meat, approx. two times less furan was formed, regardless of the processing technology. In addition to furan, also other headspace volatiles were measured and statistically evaluated. Compounds originated through fatty acids oxidation and Maillard reaction products were more abundant in conventionally sterilized samples compared to those treated by ohmic heating.Industrial relevanceOhmic heating is an emerging technology being employed in the field of food processing which applies a direct electric current to food products, providing rapid and uniform heating throughout the product. Shorter heating times used in ohmic heating, as compared to conventional retort sterilization, reduce potential losses of valuable nutrients and as well as reduce the formation of undesirable processing contaminants, in particular furan.The presented work examines furan concentrations across various stages of baby food production, in order to compare ohmic heating and retort sterilization processes. Volatile compound fingerprints for baby food purees processed via both sterilization methods, both prior and post sterilization were assessed. The results presented in this work are of high potential interest to the baby food industry to reduce both heat induced chemical changes and exposure of infants and babies to hazardous processing contaminants such as furan.     

Analysis of furan in heat-processed foods consumed in Korea using solid phase microextraction–gas chromatography/mass spectrometry (SPME–GC/MS)

Furan (C₄H₄O) is a volatile compound formed during the Maillard reaction and was recently classified as a possible human carcinogen (group 2B) by the International Agency for Research on Cancer. It has been reported to occur in various canned and jarred foods that undergo heat treatment. The aim of the present study was to optimise the sample preparation for furan analysis using solid phase microextraction–gas chromatography/mass spectrometry (SPME–GC/MS), according to the food matrix. We also performed the monitoring and risk assessment of furan in various food products. The optimised fibre exposure temperatures, time and amount of sample of liquid, semi solid and paste state foods were 5 g (ml), 50 °C, and 20 min, respectively. The level of furan in canned meat (32.16 ng/g) was the highest among the samples studied. The furan levels in canned fish, canned vegetable, nutritional/diet drinks, canned soups and jarred sauces were 29.40, 22.86, 7.28, 18.54 and 21.52 ng/g, respectively. Furan concentrations in baby food products were between 3.43 and 97.21 ng/g. Exposure estimates (14.59 ng/kg bw/day) of baby foods was the highest among all the tested food samples. However, the exposure estimate of baby foods was lower than that prescribed by the US FDA.     

Influences of Operating Parameters on the Formation of Furan During Heating Based on Models of Polyunsaturated Fatty Acids

Furan, a possible carcinogen, is commonly produced by thermal processing in a number of heated foods. The existence of furan levels in foods has attracted considerable attention worldwide. Recent research of furan in food has focused on the possible influences of operating parameters on the furan formation during heat processing. The aim of our study was to investigate the impacts of multiple factors (pH, temperature, heating time, ferric, and glutamic acid) on furan formation using linolenic and linoleic acids‐based model systems in which furan was analyzed by headspace gas chromatography–mass spectrometry (HS‐GC–MS). The results revealed that the content of furan increased rapidly when the heating temperature was elevated, with the highest levels of furan in neutral buffer solutions, the furan levels were also found to be related to heating time in all model systems. Ferric promoted furan formation from polyunsaturated fatty acids, conversely glutamic acid with an optimum concentration suppressed the furan formation. The minimal level of furan in foods during thermal treatment could be achieved via adding furan formation suppressors, and/or avoidance of furan forming promoter.     

Furan in heat‐treated foods: Formation,exposure, toxicity,and aspects of risk assessment

Furan is formed in a variety of heat‐treated foods through thermal degradation of natural food constituents. Relatively high levels of furan contamination are found in ground roasted coffee, instant coffee, and processed baby foods. European exposure estimates suggest that mean dietary exposure to furan may be as high as 1.23 and 1.01 μg/kg bw/day for adults and 3‐ to 12‐month‐old infants, respectively. Furan is a potent hepatotoxin and hepatocarcinogen in rodents, causing hepatocellular adenomas and carcinomas in rats and mice, and high incidences of cholangiocarcinomas in rats at doses ≥2 mg/kg bw. There is therefore a relatively low margin of exposure between estimated human exposure and doses that cause a high tumor incidence in rodents. Since a genotoxic mode of action cannot be excluded for furan‐induced tumor formation, the present exposures may indicate a risk to human health and need for mitigation. This review summarizes the current knowledge on mechanisms of furan formation in food, human dietary exposure to furan, and furan toxicity, and highlights the need to establish the risk resulting from the genotoxic and carcinogenic properties of furan at doses lower than 2 mg/kg bw.     

Some factors affecting the formation of furan in heated foods

Levels of furan in various foods were measured before and after heating under heating and laboratory conditions. The effect of contact with can coatings, sealing gaskets and the epoxidized oils used in gasket manufacture on furan formation was studied. The objective was to identify factors affecting furan formation. Furan present in heat-processed food samples persisted during cooking. Furan was shown to form in foods on heating, although it did not accumulate to a significant degree on heating in an open vessel. There were no interactions between foods and cans, can coatings or gaskets that had a significant influence on furan formation. Furan accumulated particularly in heat-processed canned and jarred foods because they are sealed containers that receive a considerable thermal load. Heating epoxidized oils used in sealing gaskets formed furan. At the levels used in gaskets, however, epoxidized oils should not affect the formation of furan in foods.     

Precursors, Formation and Determination of Furan in Food

The origins and mechanisms of formation of the recently identified and possible food carcinogen furan are reviewed including analytical methods used for its determination in food products. Literature data indicate a multiple source of furan formation originating from (i) thermal degradation/Maillard reaction of reducing sugars alone or in the presence of amino acids, (ii) thermal degradation of certain amino acids, and thermal oxidation of (iii) ascorbic acid, (iv) poly-unsaturated fatty acids and (v) carotenoids. Two approaches were suggested for the analysis of furan in food samples, one is based on simple headspace-GC/ MS and other is based on solid phase micro-extraction-GC/MS. Both techniques can detect furan in ppb levels and are adequate for monitoring low levels of furan formed in food.

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Zusammenfassung (Redaktion). Die Ausgangssubstanzen und die Bildungsprozesse für das erst kürzlich in Lebensmitteln identifizierte, m?glicherweise Krebs ausl?sende Furan werden dargestellt einschlie?lich der analytischen Methoden, um es in Lebensmitteln nachweisen zu k?nnen. Die publizierten Daten weisen darauf hin, da? Furan in Lebensmitteln gebildet werden kann durch (i) thermischen Abbau/Maillard-Reaktion von reduzierenden Zuckern ohne oder in Gegenwart von Aminos?uren, (ii) thermischen Abbau von bestimmten Aminos?uren und thermischen Abbau von (iii) Ascorbins?ure, (iv) unges?ttigten Fetts?uren und (v) Carotenoiden. Zwei experimentelle Vorgehensweisen werden vorgeschlagen, um Lebensmittelproben auf Furan zu untersuchen. Da mit beiden Verfahren Furan im ppb-Bereich nachgewiesen werden kann, sind sie für das Lebensmittelmonitoring in Bezug auf Furan geeignet.

     

Furan in commercial baby foods from the Spanish market: estimation of daily intake and risk assessment

ABSTRACT

The occurrence of furan in commercial baby food samples from the Spanish market was evaluated using an automated headspace solid-phase microextraction method coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS). A total of 76 baby food samples including infant formula, baby cereals, fruit in cans and/or jars, vegetables, meat, and fish, were surveyed for furan content. The lowest concentration of this compound was found in infant formula (<0.02–0.33 ng ml^?1), and cereal-based food (0.15–2.1 ng g^?1) while baby food containing fish showed the highest concentrations (19–84 ng g^?1). Following recommendation of the European Food Safety Authority (EFSA), the effect on furan content was evaluated of consumer home preparation of foods, heating and handling. Furan concentrations were reduced by up to 35% when samples were heated in a dish using microwave oven and by up to 53% when a hot water bath was used. Finally, we estimated the furan intake from baby food consumption (0.002–1.18 µg kg^?1 body weight day^?1) and we calculated the margin of exposure (MOE) from samples as purchased and also after home preparation of the food. For infant formula and cereal baby foods, the MOEs (26,278–412,776) indicated no infant health concern or priority, while for meat and fish-based baby foods the values pointed to a potential public health risk, even considering the furan losses during preparation at home.     

灭菌过程中乳糖-氨基酸模型生成呋喃的影响因素研究

呋喃是一种"2B"类致癌物,可由维生素C、碳水化合物、氨基酸、多不饱和脂肪酸和类胡萝卜素等多种前体合成,广泛存在于热加工食品中。呋喃的危害在婴幼儿食品中更为严重,为此本文基于婴幼儿金枪鱼泥中游离糖类和氨基酸类的成分及含量,构建了四种乳糖-氨基酸模型,设计了二水平部分因子实验,系统地研究了灭菌时间、灭菌温度、p H值、相态和缓冲体系对呋喃形成的影响。结果表明:在四种乳糖-氨基酸模型中,各因素对呋喃的影响有相似的规律,即高温、长时间加热、中性环境、液态和磷酸盐促进呋喃的形成;灭菌时间、灭菌温度、p H值、缓冲体系对呋喃生成量的影响较大,而相态的影响效果较小。本研究旨在为食品中呋喃的防控提供一定的理论基础,同时也为食品中其它危害物的研究提供方法借鉴。     

Microbial safety and consumer acceptability of high-pressure processed hard clams (Mercenaria mercenaria)

Littleneck hard clams (Mercenaria mercenaria) harvested from New Jersey coastal waters in the United States were high-pressure processed (HPP) in their shells using a 10 L high-pressure processing unit. A response surface (RS) methodology approach was used to optimize the pressure and time parameters for microbial inactivation caused by the high-pressure application. The total surviving microbial load in the hard clams was enumerated after processing at each experimental condition. The results indicated that log reduction in total plate count (TPC) due to high-pressure processing of hard clams was primarily a function of pressure. Pressure of at least 480 MPa was needed to achieve 1-log reduction in TPC in hard clams harvested from special restricted waters. In a parallel study, a panel of 60 regular raw clams consumers tasted both raw and processed hard clams that were harvested from approved waters and HPP at 310 MPa for 3 min. The consumers showed equal preference for processed and raw hard clams. Two subgroups of hard clam consumers were revealed; 1 group preferred the plumpness of the HPP clam and the other group preferred aroma of the unprocessed clam. Thus, plumpness and aroma may influence consumer acceptance of HPP hard clams. PRACTICAL APPLICATION: High-pressure processing has gained momentum as a processing technique that aids in retention of fresh appearance in foods. It holds promise as a method to process premium value food products while retaining quality attributes. Quantification of its impact on safety and consumer acceptance is critical for its acceptance and use in the food industry.     

Rapid and improved determination of furan in baby foods and infant formulas by headspace GC/MS

Furan is a 5-membered ring compound with high volatility. The U.S. Food and Drug Administration (FDA) has recently published a report on the occurrence of furan in a large number of thermally processed foods. However, the FDA's analytical method, using standard curve addition, is not suitable for high-throughput routine laboratory operations. We developed a rapid and improved method for determination of furan in foods by headspace GC/MS. Quantification was achieved by using an internal standard of d4-furan and an external calibration curve of furan normalized against the internal standard. The incubation temperature for equilibration was set at 60 degrees C to avoid the formation of furan during analysis. The levels of furan in baby foods and infant formulas were determined with this method. Validation data showed good precision and accuracy. The LOD and LOQ were 0.2-0.5 ng/g and 0.5-2 ng/g for various food matrixes, respectively. The level of furan detected was in the range of 1.4 to 90 ng/g in baby foods and in the range of non-detectable to 36 ng/g in infant formulas.     

Effect of cooking or handling conditions on the furan levels of processed foods

The aim of this study was to investigate the possible effects of cooking or handling conditions on the concentration of furan in processed foods. The analytical method used to analyse furan levels in foods was optimized based on solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). In baby soups, the concentration of furan decreased by up to 22% after opening a lid for 10 min. In the baby food in retort packaging, the level of furan was reduced by 15–33% after heating the foods at 50°C without a lid. Furan in rice seasonings was evaporated completely after heating the foods at 60°C. Regarding powered milk, the levels of furan were too low to be compared under various conditions. The levels of furan decreased to 58% in beverage products for babies, after storing them at 4°C for 1 day without a lid. The levels of furan in canned foods such as cereal and vegetable were reduced by zero to 52% when they were stored without stirring in a refrigerator at 4°C for 1 day. When we boiled canned fish, the furan present was almost completely evaporated. It is recommended that canned meats be heated up to 50–70°C for the reduction (26–46%) of furan levels. The levels of furan in instant and brewed coffee samples were significantly reduced after storing for 11 to 20 min at room temperature without a lid (p < 0.05).     

Recent Advances in Food Processing Using High Hydrostatic Pressure Technology

High hydrostatic pressure is an emerging non-thermal technology that can achieve the same standards of food safety as those of heat pasteurization and meet consumer requirements for fresher tasting, minimally processed foods. Applying high-pressure processing can inactivate pathogenic and spoilage microorganisms and enzymes, as well as modify structures with little or no effects on the nutritional and sensory quality of foods. The U.S. Food and Drug Administration (FDA) and the U.S. Department of Agriculture (USDA) have approved the use of high-pressure processing (HPP), which is a reliable technological alternative to conventional heat pasteurization in food-processing procedures. This paper presents the current applications of HPP in processing fruits, vegetables, meats, seafood, dairy, and egg products; such applications include the combination of pressure and biopreservation to generate specific characteristics in certain products. In addition, this paper describes recent findings on the microbiological, chemical, and molecular aspects of HPP technology used in commercial and research applications.     

Development of an analytical method and survey of foods for furan, 2-methylfuran and 3-methylfuran with estimated exposure

Furan has been found to form in foods during thermal processing. These findings, a classification of furan as a possibly carcinogenic to humans, and a limited amount of data on the concentration of furan in products on the Canadian market prompted the authors to conduct a survey of canned and jarred food products. Methyl analogues of furan, 2-methylfuran and 3-methylfuran, were analysed concurrently with furan via a newly developed isotope dilution method, as these analogues were detected in foods in the authors’ earlier work and are likely to undergo a similar metabolic fate as furan itself. The paper reports data on 176 samples, including 17 samples of baby food. The vast majority of samples were packaged in cans or jars. Furan was detected above 1 ng g^?1 in all non-baby food samples with a median of 28 ng g^?1 and concentrations ranging from 1.1 to 1230 ng g^?1. Also, 96% of these samples were found to contain 2-methylfuran above 1 ng g^?1 with a median of 12.8 ng g^?1 and a maximum concentration of 152 ng g^?1, while 81% of samples were found to contain 3-methylfuran above 1 ng g^?1 with a median of 6 ng g^?1 and a maximum concentration of 151 ng g^?1. Similarly, furan was detected above 1 ng g^?1 in all baby food samples with a median of 66.2 ng g^?1 and concentrations ranging from 8.5 to 331 ng g^?1. Also, 100% of these samples were found to contain 2-methylfuran above 1 ng g^?1 with a median of 8.7 ng g^?1 and a maximum concentration of 50.2 ng g^?1, while 65% of samples were found to contain 3-methylfuran above 1 ng g^?1 with a median of 1.6 ng g^?1 and a maximum concentration of 22.9 ng g^?1. Additionally, three coffee samples were analysed ‘as is’, without brewing, and were found to have high levels of furans, especially 2-methylfuran, at a maximum of 8680 ng g^?1. Using this data set, dietary exposures to furan and total furans were calculated. Average furan and total furan intakes by adults (≥20 years) were estimated at approximately 0.37 and 0.71 µg kg^?1 of body weight day^?1 respectively.     

Effect of ionizing radiation on furan formation in fresh-cut fruits and vegetables

ABSTRACT:  Furan, a possible carcinogen, is commonly induced by thermal processing in a wide variety of foods. The possible formation of furan from fresh-cut fruits and vegetables due to irradiation was studied. Nineteen fresh-cut fruits and vegetables were irradiated by 5 kGy gamma rays at 4 °C. Furan was analyzed from the irradiated samples using a number of preparation methods. The results showed that almost all tested fruits and vegetables, upon irradiation, produced nondetectable levels, or less than 1 ng/g of furan. Irradiation induced low ng/g levels of furan only in grape and pineapple. Dipping apple slices into calcium ascorbate before irradiation did not increase furan formation. The pH and the amount of simple sugars in fresh fruits and vegetables had a role in furan formation. Low levels of furan were induced by irradiation only in those fruits that had a high amount of simple sugars and low pH.     

Effects of high pressure processing on lipid oxidation: A review

High pressure processing (HPP) is an alternative mild-technology used in the past decades to sterilize and pasteurize food matrices such as meat and seafood. HPP obeys thermodynamic principles, namely Le Chatelier's law of equilibrium and the isostatic rule, both of which account for microbial inactivation. HPP has the advantage of ensuring reduction of pathogens and spoilage in foods, and preserving the organoleptic characteristics of the product that are compromised in traditional heat treatments. However, high pressure changes the thermodynamic equilibrium of chemical reactions. This is the case of lipid oxidation, in which kinetics is accelerated in the presence of high hydrostatic pressure.In recent years, there has been increasing focus on the response of lipid components to HPP, especially considering the deleterious outcomes that secondary products of oxidation have on the final product. The objective of this work is to review the literature on the effect of this “mild-technology” in the degradation of lipid fraction of foods. We discuss qualitative and quantitative determinations, as well as the thermodynamic and chemical interpretations underlying the phenomenon.Industrial relevanceIn this work we reviewed the literature concerning the effect of high-pressure processing (HPP) on lipid oxidation. Since 1990s HPP has been used as an alternative to thermal treatments to pasteurize and sterilize food products, such as meats and seafood. Many of these raw materials have a high content of lipids (among them trialglycerols and cholesterol-derivative) that are susceptible to oxidation. During the last decade, there has been increasing interest on the response of lipid components to HPP, especially considering the deleterious outcomes that secondary oxidation-derivative molecules have on the final product. This review intends to summarize and discuss the data reported in literature, contextualizing the oxidation within the broad transformation of biological structures due to hydrostatic pressure. A better understanding of the underlying phenomena could lead to the development of predicting models which could be use in food industry.     

Inactivation of foodborne viruses of significance by high pressure and other processes

The overall safety of a food product is an important component in the mix of considerations for processing, distribution, and sale. With constant commercial demand for superior food products to sustain consumer interest, nonthermal processing technologies have drawn considerable attention for their ability to assist development of new products with improved quality attributes for the marketplace. This review focuses primarily on the nonthermal processing technology high-pressure processing (HPP) and examines current status of its use in the control and elimination of pathogenic human viruses in food products. There is particular emphasis on noroviruses and hepatitis A virus with regard to the consumption of raw oysters, because noroviruses and hepatitis A virus are the two predominant types of viruses that cause foodborne illness. Also, application of HPP to whole-shell oysters carries multiple benefits that increase the popularity of HPP usage for these foods. Viruses have demonstrated a wide range of sensitivities in response to high hydrostatic pressure. Viral inactivation by pressure has not always been predictable based on nomenclature and morphology of the virus. Studies have been complicated in part from the inherent difficulties of working with human infectious viruses. Consequently, continued study of viral inactivation by HPP is warranted.     

氨基酸对葡萄糖、半乳糖模型产生呋喃的影响

为研究氨基酸对葡萄糖和半乳糖模型产生呋喃的影响,通过向葡萄糖模型和半乳糖模型中加入不同含量的甘氨酸、丝氨酸、苏氨酸、谷氨酸,模拟密封罐装食品的灭菌条件（121 ℃条件下油浴30 min）,采用顶空气相色谱-质谱（headspace-gas chromatography-mass spectrometry,HS-GC-MS）法检测呋喃的含量。结果表明：低含量（≤5 mg）的甘氨酸、极低含量（1 mg）的丝氨酸、高含量（50 mg）的苏氨酸和谷氨酸的添加能够明显促进葡萄糖模型产生呋喃,而对于半乳糖模型,所有高含量（50 mg）氨基酸的添加都能够导致呋喃的大量产生。苏氨酸对葡萄糖模型产生呋喃的促进作用明显强于其余3 种氨基酸（P＜0.05）;对于半乳糖模型,甘氨酸、苏氨酸对其产生呋喃的促进作用最强,且它们之间无明显差异。