Derivative spectrophotometric determination of 5-(hydroxymethyl)-2-furaldehyde (HMF) and furfural in Locust bean extract

Furfural and 5-(hydroxymethyl)-2-furaldehyde (HMF) are useful indicators of accurate storage temperature of food samples. A first derivative spectrophotometric method was developed for the determination of the furfural and HMF level in Locust bean pekmez. In addition, the levels of the furfural and HMF were investigated during Locust bean pekmez preparation. The recoveries were generally nearly 100%. This method is also rapid and accurate and results in economical analyses of furaldehydes.     

Nonenzymic browning reactions in boiled grape juice and its models during storage

Reaction orders, rate constants and activation energies were evaluated for 5-hydroxymethyl furfural (HMF) accumulation and brown pigment formation (BPF) in pekmez and its model systems stored at 55, 65 and 75°C over 10 days at pH 4.0. The model systems and their compositions were decided by considering the major pekmez components. Accumulation of HMF and BPF were the highest in pekmez and they were the smallest in model 1. ANOVA showed that the effects of temperature on both accumulation of HMF and BPF were significant (p<0.05). Results obtained from non-linear regression analysis indicated that reaction order was 0.5 for 5-HMF accumulation and was zero for brown pigment formation in the model systems. Reaction orders were zero for both HMF accumulation and BPF in pekmez. Calculated activation energies for HMF and brown pigment formation were in the range of 49.7–103 kJ mol⁻¹ and 116–132 kJ mol⁻¹ respectively.     

Relationship of Sensory Staleness in Two Lagers to Headspace Concentrations of trans‐2‐Nonenal and Three Staling Aldehydes

Key compounds in lager staling include furfural, hexanal, 5‐ hydroxymethyl furfural (5‐HMF), and trans‐2‐nonenal. Quantitative data of headspace concentration in two lagers — one premium at 5% (abv), the other a standard product at 4% (abv) — were obtained by solid phase microextraction (SPME) followed by gas chromatography using a mass selective detector (GCMS). The concentrations of the aldehydes were used to predict overall stale scoring from sensory assessor data, of lagers stored at 4, 12, 30, and 37°C for 7, 14, 21 and 28 days. Concentrations of all four aldehydes increased with time of storage and with higher temperatures. Correlation coefficients for prediction of staleness in the premium lager were similar at 0.81 and 0.84 for partial least square regression (PLS1) and artificial neural network (ANN) modelling respectively, and the latter showed a lower root mean square error (RMS error). For the standard product, the correlation coefficients were 0.72 and 0.86, with ANN showing lower RMS error respectively. In both PLS models, E‐2‐ nonenal had high regression coefficients and 5‐HMF lower coefficients. Furfural and hexanal differed in contributions to the lagers.     

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 non‐enzymatic browning of liquid infant milk formulae

Furfural, hydroxymethylfurfural (HMF), furosine, lactulose, ascorbic acid and absorbance at 284 and 420 nm (A₂₈₄ and A₄₂₀) were all determined in two types of liquid infant formula prepared with different processing protocols. These browning indicators were used to assess the effects of storage and modified atmosphere on the shelf‐life of infant formulae. The study was carried out at 20 and 55 °C for 15, 30 and 90 days. At 20 °C, slight browning was observed and could be evaluated by furosine, furfural and total HMF indicators. At 55 °C, formula type A (pasteurised, spray‐dried and reconstituted) showed more browning in nitrogen storage conditions than did type B. Furfural, HMF, lactulose, A₂₈₄ and A₄₂₀ are useful indicators to control the extent of browning reactions in adverse storage conditions. © 2002 Society of Chemical Industry     

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.     

Effects of metal ions on formation of acrylamide and 5‐hydroxymethylfurfural in asparagine–glucose model system

Undesirable substances of thermal food processing such as acrylamide (AA) and 5‐hydroxymethylfurfural (HMF) have been intensively studied in recent decades. The aim of this work was to investigate the evolution mechanism of AA and HMF contents in the presence of various valence metal cations at various concentrations in asparagine–glucose model system. Three interesting phenomena were found. Firstly, the AA contents first decreased and then increased, whereas the HMF contents first increased and then decreased, with increasing metal cations concentration; secondly, the concentration of cations for maximal HMF contents was lower than the concentration of cations for minimal AA contents; thirdly, the maximum AA‐inhibiting or HMF‐promoting efficiency was achieved more readily with trivalent, then divalent and lastly monovalent cations. These phenomena can be explained by that increasing the metal cations concentration can increase the protonated product contents, thus increasing the AA‐inhibiting efficiency and HMF‐promoting efficiency. With higher metal cations concentration in the model system, HMF as a reactant can react with the asparagine to form AA or directly decompose into furfural. These interesting results can provide a theoretical foundation to simultaneously control the formation of AA and HMF during food processing.     

In vitro gastrointestinal digestion of polyphenols from different molasses (pekmez) and leather (pestil) varieties

In this study, to evaluate the in vitro bioaccessibility of eight different pekmez and pestil samples, total phenolics, flavonoids, proanthocyanidins, anthocyanins and antioxidant capacity were determined at different phases of simulated gastrointestinal (GI) digestion. For the analysis of antioxidant activity, four different methods were used including 2,2‐azinobis(3‐ethylbenzothiazoline)‐6‐sulfonic acid, 1,1‐diphenyl‐2‐picrylhydrazil, ferric reducing antioxidant power and cupric ion reducing antioxidant capacity. The results revealed that the dialysed fraction (IN) represented 12–50%, 3–17% and 3–72% of the total phenolics, flavonoids and proanthocyanidins, respectively. Moreover, total antioxidant capacity of IN fraction was 2–57% of the initial values obtained for pekmez and pestil samples. To identify the influence of simulated in vitro GI digestion on total anthocyanins, only black mulberry molasses (pekmez) and plum leather (pestil) were analysed and according to the results no anthocyanins were detected in the IN fraction for both samples. The present study presented a detailed insight of bioaccessibility of polyphenols in various pekmez and pestil samples.     

RAPID HIGH PERFORMANCE LIQUID CHROMATOGRAPHIC DETECTION OF FUROSINE (ε‐N‐2‐FUROYLMETHYL‐L‐LYSINE) IN YOGURT AND CHEESE MARKETED IN TURKEY*

Furosine (ε‐N‐2‐furoylmethyl‐L‐lysine) content determination in the yogurt and different cheese types (pickled white, kasar, processed, canned tulum, blue‐veined and mozzarella cheeses) marketed in Turkey was performed using ion‐pair reversed‐phase high performance liquid chromatography (RP‐HPLC). Calibration study (R² = 0.9999), analytical method validation and recovery studies gave satisfactory results. The lowest furosine values were observed in pickled white cheeses (5.35 ± 0.01 to 7.28 ± 0.02 mg/100 g protein). All cheeses except pickled white showed furosine values between 182.16 ± 0.12 (canned tulum) and 261.32 ± 0.10 mg/100 g protein (ripened kasar). The highest content of furosine was observed in whole yogurt (316.47 ± 0.17 mg/100 g protein) which could be because of severe heat treatment and the addition of milk powder during the manufacturing process. The method provides a rapid, reproducible and accurate determination of this Amadori compound (ε‐deoxy‐fructosyl‐lysine) in yogurt and cheese samples.     

Catalytic conversion of carbohydrates into 5‐hydroxymethylfurfural by Hafnium(IV) chloride in ionic liquids

Conversion of carbohydrates into HMF in ionic liquids (ILs) catalyzed by HfCl₄ has been investigated in search of an efficient and environment‐friendly process. The structure of ILs, catalyst loading, and reaction temperature had remarkable effects on this new catalytic system. Under optimal conditions, HMF yield up to 77.5% was obtained from fructose in 30 min at 100°C. Moderate yields of HMF were also obtained from aldohexose such as glucose, cellobiose, even cellulose. Furthermore, a possible mechanism for carbohydrates conversion into HMF catalyzed by HfCl₄ was proposed according to the configuration of valence shell of Hf. This work provides a meaningful method for the conversion of carbohydrates into fine chemicals.     

Degradation of N‐(1‐Deoxy‐d‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐xylulos‐1‐yl)proline using thermal treatment

The formation and degradation of N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)proline, derived from the secondary amine Maillard reaction in xylose‐amino acid model solutions, were detailed in this study. The identification and quantitative analysis of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline were carried out using high‐performance anion‐exchange chromatography and high‐performance liquid chromatography. The formation of intermediate and advanced products derived from N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline was also tested using an UV‐Vis spectrophotometer to gain a better comparing of the degradation process of the two important Maillard reaction products using thermal treatment. Results showed that the degradation of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine was more significant than N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline. Moreover, xylose was tested in the degradation products of both N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline, which indicated that the degradation of N‐substituted 1‐amino‐1‐deoxyketoses was a reversible reaction to form reducing sugar.     

Does the pelleting process affect the nutritive value of a pre‐starter diet for suckling piglets? Ex vivo studies on mineral absorption

BACKGROUND: The effects of pelleting on the extent of the Maillard reaction (MR) and on calcium, magnesium and zinc solubility and absorption were analysed in a conventional pre‐starter diet for suckling piglets. Development was tested measuring colour, absorbance (280/420 nm), fluorescence, residual free lysine, furosine, hydroxymethylfurfural (HMF) and furfural contents before and after pelleting. Fluorescence, absorbance and mineral solubility were also measured after in vitro digestion of diets. The effects on mineral absorption were tested using Caco‐2 cells. RESULTS: MR indexes confirmed the development of the reaction during the pelleting of this particular diet compared with the meal diet. The CIE‐Lab colour parameters showed a decrease in luminosity (L*) and progress of the colour to the red zone (a*) in the pelleted diet. A 36% decrease in free lysine content was observed. Significant correlations were observed between fluorescence intensity and furosine levels, HMF and furfural. The pelleting process did not modify calcium and magnesium solubility after in vitro digestion, but soluble zinc increased. The efficiency of calcium and zinc transport across Caco‐2 cell monolayers was greater in the pelleted diet. CONCLUSIONS: Evidence of MR development is shown, resulting in various nutritional consequences. Optimisation of pelleting could result in a better formulation of diets for feedstuffs. Copyright © 2010 Society of Chemical Industry     

EFFECT OF SODIUM METABISULFITE ADDITION AND BAKING TEMPERATURE ON MAILLARD REACTION IN BREAD

ABSTRACT

In this study, the effect of sodium metabisulfite (SMBS) doses (0, 25, 50, 100 mg/kg dough) and baking temperatures (200, 230 and 250C) on the physical, chemical and sensory properties of bread were researched to reduce 5‐hydroxymethyl‐2‐furfural (HMF) and acrylamide contents. HMF and acrylamide contents of bread crust were decreased significantly by increasing SMBS dose and decreasing baking temperature. The HMF (137.29 mg/kg) and acrylamide (671.44 µg/kg) contents of bread crust were decreased by 33 and 67%, respectively by addition of 100 mg/kg SMBS. The maltol content of bread crusts were significantly affected by baking temperature, and were 7.19, 10.23 and 22.69 mg/kg in breads baked at 200, 230 and 250C, respectively. No HMF, acrylamide and maltol were detected in the bread crumb. The sulfur dioxide content of the crust and crumb of control bread was 6.99 and 10.69 mg/kg, and increased by 49 and 59%, respectively at 100 mg/kg SMBS dose. All breads were evaluated as acceptable by a sensory panel.

PRACTICAL APPLICATIONS

Since Maillard reaction products such as acrylamide and 5‐hydroxymethyl‐2‐furfural (HMF) are known as toxic compounds, mitigation of these compounds is important subject for health and nutrition. There is not an efficient method to prevent the formation of acrylamide and HMF in bread crusts comparison with potato crisps. The purpose of this research is to slow down Maillard reaction by addition of sodium metabisulfite in bread‐making process. As a result of this research, acrylamide and HMF content of bread crusts decreased by 33 and 67%, respectively with acceptable sensory evaluation.     

Some physico‐chemical characteristics of honeys produced from sunflower plant (Helianthus annuus L.)

This study was conducted to determine the physico‐chemical characteristics of honeys (n = 52 samples) produced from sunflower in Trakya region of Turkey. We have evaluated the conformity of the honeys in accordance with the criteria specified by the Turkish Honey Standard (TS 3036), Turkish Food Codex and European Union Commission. According to the results of our analysis, the average values determined were in Tekirdag (n = 10 samples), Malkara (n = 22 samples), Hayrabolu (n = 13 samples) and Muratl? (n = 7samples) respectively: 6.67%, 6.06, 8.43, 7.89 for hydroxymethyl furfural (HMF); 15.02, 23.98, 18.61, 17.61 (Goethe unit) for diastase activity; 2.01%, 2.39, 2.36, 1.69 for saccharose; 75.26, 73.78, 75.50, 76.80 for invert sugar (%); 23.38, 34.92, 31.70, 26.38 for meq kg^?1 for acidity; 0.16, 0.25, 0.31, 0.13 for ash value (%); 18.13, 18.21, 17.52, 18.21 for water content (%).     

Changes in browning‐related components of apple slices during different stages of instant controlled pressure drop‐assisted hot air drying (AD‐DIC)

The effect of instant controlled pressure drop‐assisted hot air drying (AD‐DIC) on browning‐related components in apple slices was studied. Results showed the AD temperature had no significant effect on colour index of final apple slices. The aspartic acid, glutamic acid, lysine, histidine, arginine, sucrose and dehydroascorbic acid (DHAA) in apple slices increased firstly during the AD process and then decreased during DIC process. The fructose, glucose, reduced ascorbic acid and major phenolic compounds reduced with the abrupt increase of 5‐hydroxymethylfurfural (5‐HMF) during AD‐DIC. There were significant correlations (P < 0.05) among moisture content (w.b.), water activity (a_w), water state, reduced ascorbic acid, DHAA, chlorogenic acid, procyanidin B₁, (+)‐catechin, (?)‐epicatechin and phlorizin during AD‐DIC. The colour difference showed that the major browning reaction of apple slices during the predrying process was enzymatic browning, while nonenzymatic browning played a crucial role on green‐red value (CIE a* value) during DIC.     

Species identification of Wickerhamomyces anomalus and related taxa using β‐tubulin (β‐tub) DNA barcode marker

Wickerhamomyces anomalus is used in food and feed processing, although the species has been reported as an opportunistic human pathogen, predominantly in neonates. Neither phenotypic nor the most frequently applied genotypic marker (D1/D2 LSU ribosomal DNA) provide sufficient resolution for accurate identification of this yeast. In this study, the β‐tubulin gene was used for species identification by direct DNA sequencing and as marker in a species‐specific PCR assay. The results showed that all examined W. anomalus strains were clearly distinguished from the closely related species by comparative sequence analysis of the β‐tubulin gene. In addition, the species‐specific primers were also developed based on the β‐tubulin gene, which was employed for polymerase chain reaction with the template DNA of Wickerhamomyces strains. A single 218 bp species‐specific band was found only in W. anomalus. Our data indicate that the phylogenetic relationships between these strains are easily resolved by sequencing of the β‐tubulin gene and combined with species‐specific PCR assay. Copyright © 2012 John Wiley & Sons, Ltd.     

α‐(1,4)‐Amylase,but not α‐ and β‐(1,3)‐glucanases,may be responsible for the impaired growth and morphogenesis of Paracoccidioides brasiliensis induced by N‐glycosylation inhibition

The cell wall of Paracoccidioides brasiliensis, which consists of a network of polysaccharides and glycoproteins, is essential for fungal pathogenesis. We have previously reported that N‐glycosylation of proteins such as N‐acetyl‐β‐d ‐glucosaminidase is required for the growth and morphogenesis of P. brasiliensis. In the present study, we investigated the influence of tunycamicin (TM)‐mediated inhibition of N‐linked glycosylation on α‐ and β‐(1,3)‐glucanases and on α‐(1,4)‐amylase in P. brasiliensis yeast and mycelium cells. The addition of 15 µg/ml TM to the fungal cultures did not interfere with either α‐ or β‐(1,3)‐glucanase production and secretion. Moreover, incubation with TM did not alter α‐ and β‐(1,3)‐glucanase activity in yeast and mycelium cell extracts. In contrast, α‐(1,4)‐amylase activity was significantly reduced in underglycosylated yeast and mycelium extracts after exposure to TM. In spite of its importance for fungal growth and morphogenesis, N‐glycosylation was not required for glucanase activities. This is surprising because these activities are directed to wall components that are crucial for fungal morphogenesis. On the other hand, N‐glycans were essential for α‐(1,4)‐amylase activity involved in the production of malto‐oligosaccharides that act as primer molecules for the biosynthesis of α‐(1,3)‐glucan. Our results suggest that reduced fungal α‐(1,4)‐amylase activity affects cell wall composition and may account for the impaired growth of underglycosylated yeast and mycelium cells. © 2013 The Authors. Yeast published by John Wiley & Sons Ltd.