Latest Updates From FoQus

  • 2nd Food Chemistry Conference has been held in Sevilla, Spain on Sep 17-19. Dr. Aytül Hamzalıoğlu, member of FoQuS research group has won the best early career presentation award for her presentation entitled “Multiresponse kinetic modeling of acrylamide and hydroxymethylfurfural formation during roasting of coffee as a sucrose-rich food system”. (2019)
  • We are pleased to announce the 2017 junior medal winner is Dr Tolgahan Kocadağlı, Research Assistant, Department of Food Engineering at Hacettepe University, Turkey. This award is based on his contribution to food chemistry, particularly in relation to research and publications on the Maillard reaction, aroma and acrylamide generation.
  • Cemile Yılmaz, member of FoQuS research group has completed successfully her PhD study entitled “Investigation of Changes in Amino Acids during Different Fermentation Conditions”. (2017)
  • Ecem Evrim Çelik, member of FoQuS research group has completed successfully her PhD study entitled “Determination of the Interactions between Bound and Free Antioxidants naturally Occurring in Foods”. (2017)
  • Patented invention by FoQuS members entitled “A Solution Extending Shelf Life of Ready-to-Eat Fresh Fruits and/or Vegetables and an Application Method Thereof” has won Gold Medal in the 2nd Istanbul International Inventions Fair (ISIF’17).
  • Aytül Hamzalıoğlu, member of FoQuS research group has completed successfully her PhD study entitled “Investigation of the Reactivities of Monomeric and Polymeric Food Components during in vitro Digestion”. (2017)
  • Neslihan Taş, member of FoQuS research group has completed successfully her PhD study entitled “Investigation of Chemical Reactions in Hazelnut Induced by Roasting”. (2017)
  • Acrylamide in Food Analysis, Content and Potential Health Effects, 1st Edition, edited by Vural Gökmen has been released (ISBN 9780128028322) in August 2015 (Elsevier – Academic Press).
  • Shortly after its discovery in 2002, acrylamide formation in foods during thermal processing has been one of the hottest topics in food science. According to the records of Web of Science, Vural Gökmen is top researcher of the world in this field of research.
  • B. Aytül Hamzalıoğlu and Ezgi Doğan Cömert, members of FoQuS research group have been selected as the Editorial Board member of Elsevier’s journal Food Research International (2015).
  • Tolgahan Kocadağlı, member of FoQuS research group has completed successfully his PhD study entitled “Investigation and Kinetic Modelling of alpha-dicarbonyl compound formation in foods”. (2016)
  • H. Gül Akıllıoğlu, member of FoQuS research group has completed successfully her PhD study entitled “Investigation of Controlled Modifications on Glycation Tendency of Proteins”. (2016)
  • 3rd International Congress on Cocoa Coffee and Tea (CoCoTea) has been held in Aveiro, Portugal on June 22-24. Neslihan Göncüoğlu Taş, member of FoQuS research group has been awarded the best poster prize for her presentation entitled “Effect of Alkalization on Maillard Reaction Process During Cocoa Roasting”. (2015)
  • Ezgi Doğan, member of FoQuS research group has completed successfully her MSc study entitled “Increasing the Total Antioxidant Capacity Bound to Insoluble Dietary Fiber”. (2015)
  • Kübra S. Özdemir, member of FoQuS research group has completed successfully her PhD study entitled “Coating of Food and Bioactive Food Components: Effects on Process and Storage Stability”. (2015)
  • Dr. Burçe Ataç Mogol has been recently promoted to Assistant Professor in Food Science Division of Food Engineering Department at Hacettepe University. (2015)
  • H. Gül Akıllıoğlu, member of FoQuS research group has been selected as as the Editorial Board member of Elsevier’s journal Food Research International (2015).
  • Vural Gökmen was selected as the Editorial Board member of Elsevier’s journal Food Chemistry (2014).
  • Vural Gökmen is ranked 131th in the list of 362 most successful Turkish scientists (h-index>20).
  • According to Thomson Retuter’s Web of Science, Vural Gökmen is currently among the top 100 authors of the world in FOOD SCIENCE and TECHNOLOGY. (2013)
  • Burçe Ataç Mogol, member of FoQuS research group has completed successfully her PhD study entitled “Mitigation of Thermal Process Contaminants by Alternative Technologies”. Please click here to access the thesis. (2014)
  • The manuscript entitled “Investigation of heat induced reactions between lipid oxidation products and amino acids in lipid rich model systems and hazelnuts” authored by Gökmen and others has been published in Food & Function, and selected as the journal’s cover article. (2013)
  • 11th International Symposium on Maillard Reaction (ISMR) has been held in Nancy where French chemist Louise Camille Maillard was born on Sep 16-20. Burçe Ataç Mogol, a member of FoQuS research group has been awarded the best poster prize for her presentation entitled “4-Methylimidazole formation from sugars and amino acids”. (2012)
  • Vural Gökmen has been selected as the Associate Editor of Elsevier’s journal Food Research International (2012).
  • In the competition of Industry Oriented Undergraduate Projects organized for the first time by Scientist Support Department of TUBITAK, Ayşegül Dönmez and Özge Alan from the department of Food Engineering have been ranked second best undergraduate project entitled “Development of Functional Margarine Containing Encapsulated Olive Mill Waste Water Phenolic Compounds”, in the category of manufacturing process and technologies among 201 projects presented by 474 students from 54 different universities in Turkey. (2012)
Lactose hydrolysis and protein fortification pose an increased risk for the formation of Maillard reaction products in UHT treated milk products

Journal of Food Composition and Analysis, 2019, 84, UNSP 103308

This study aimed to survey the content of Maillard reaction products in different UHT-treated milk products and to assess how formation of these products and lysine blockage is affected by the composition. For this purpose, different commercial UHT milks including milk (whole, semi-skimmed and skimmed), lactose-hydrolyzed, protein-fortified, lactose-hydrolyzed protein fortified and follow-on infant milks were analyzed. Among the Maillard reaction products, dicarbonyl compounds, 5-hydroxymethylfurfural, furosine, N-epsilon-carboxymethyllysine and N-epsilon-carboxyethyllysine were monitored. The results showed that fortification of UHT milks with protein and carbohydrates as well as hydrolysis of lactose promoted the Maillard reaction. Among the dicarbonyl compounds, 3-deoxyglucosone formation, which was the dominant dicarbonyl compound in milks, varied between 3.12-12.67 mg/L, 13.45-21.98 mg/L and 4.59-40.38 mg/L in lactose hydrolyzed, lactose-hydrolyzed protein fortified and follow-on infant milks whereas it was 0.22-0.40 mg/L in milks, respectively. Similarly, 5-hydroxymethylfurfural could not be detected in milks, whereas mean 5-hydroxymethylfurfural concentration was found to be 56.3 mg/L and 31.5 mg/L in protein-fortified milks and lactose-hydrolyzed protein-fortified milks, respectively. Accordingly, % blocked lysine, furosine, N-epsilon-carboxymethyllysine and N-epsilon-carboxyethyllysine content of different UHT milks were found to be significantly higher than milks (p < 0.05). This is the first study reporting the Maillard reaction products in protein-fortified and infant milks.

Kinetic evaluation of the formation of tryptophan derivatives in the kynurenine pathway during wort fermentation using Saccharomyces pastorianus and Saccharomyces cerevisiae 

Food Chemistry, 2019, 297, UNSP 124975

This study aimed to evaluate the formation of tryptophan derivatives in the kynurenine pathway during wort fermentation using a multi-response kinetic model and an empirical modified logistic model. Saccharomyces cerevisiae NCYC 88 (ale yeast) and S. pastorianus NCYC 203 (lager yeast) were used to understand the effect of fermentation type on tryptophan derivatives. According to the modified logistic model, tryptophan concentration was critical for the maximum production rate of kynurenic acid, a neuroprotective compound. The results indicated that utilization of tryptophan and kynurenic acid formation were faster in wort fermented with S. cerevisiae than with S. pastorianus. The reaction rate constants implied that the kynurenic acid formation stage was minor compared to other enzymatic reactions leading to NAD(+) synthesis. Multi-response kinetic modeling of kynurenine pathway provided insights into tryptophan derivative formation, which can facilitate improved beer fermentation processing.

Investigations on the Maillard Reaction in Sesame (Sesamum indicum L.) Seeds Induced by Roasting

Journal of Agricultural and Food Chemistry, 2019, 67(17), 4923-4930

This study investigated the formation of Maillard reaction products in sesame seeds under different roasting conditions. Sesame seeds were roasted at 150, 180, 200, and 220 degrees C for 10 min, and thermal process contaminants including 5hydroxymethylfurfural, acrylamide, furan, and dicarbonyl compounds (1-deoxyglucosone, 3-deoxyglucosone, methylglyoxal, and diacetyl) together with glycation markers namely N-epsilon-fructosyllysine, N-epsilon-carboxymethyllysine, and N-epsilon-carboxyethyllysine, were monitored. Roasting induced the formation of 5-hydroxymethylfurfural, acrylamide, and dicarbonyl compounds, except furan, significantly (p < 0.05). 5-Hydroxymethylfurfural and acrylamide content of roasted sesame seeds were found to vary as 3-40 mg/kg and 135-633 mu g/kg, respectively. Dicarbonyl compounds were in the following order: methylglyoxal > 3-deoxyglucosone > 1-deoxyglucosone > diacetyl. On the other hand, N-epsilon-fructosyllysine concentration decreased while the roasting temperature increased; however, N-epsilon-carboxymethyllysine and N-epsilon-carboxyethyllysine formation was induced under those conditions. This is the first study reporting the formation of thermal process contaminants and glycation markers in sesame seeds through Maillard reaction during roasting.

Interactions of dietary fiber bound antioxidants with hydroxycinnamic and hydroxybenzoic acids in aqueous and liposome media

Food Chemistry, 2019, 278, 294-304

The interactions between dietary fiber (DF)-bound antioxidants and free antioxidants, with different substitution patterns of -OH and -OCH3 groups on their aromatic rings has been investigated. The activity and efficiency of these interactions were examined with a structural approach. Whole wheat (WW) DF-bound antioxidants and 21 hydroxycinnamic acid/hydroxybenzoic acids (HCA/HBA) were used in the experimental studies. Studies were performed in liposome and aqueous media by monitoring lipid oxidation and scavenging of DPPH radical in the presence of WW-bound antioxidants and HCA/HBA derivatives. Predominantly synergistic interactions were observed in aqueous medium, while both synergistic and antagonistic interactions were seen in liposome medium. Concentrations of HCA/HBA and WW-bound antioxidants in mixtures and their 2-way interactions made significant effect on lipid oxidation and radical scavenging reactions, with some exceptions. HCA/HBA derivatives with 3,4 -dihydroxyphenyl substitution acted as strong antioxidants in liposome medium, while the number of -OH groups affected antioxidant activity in aqueous medium.

Investigations on the effect of broccoli and wine sulphur compounds on glyoxal scavenging under simulated physiological conditions 

Journal of Functional Foods, 2019, 55, 220-228

This study aimed to investigate the glyoxal (GO) scavenging effect of broccoli and wine sulphur compounds in model systems under physiological conditions. The model systems composed of GO and different sulphur compounds both in pure forms and food extracts were subjected to simulated physiological conditions (37 degrees C & 7.4 pH, 2 h). The results revealed that some of these sulphur sources could scavenging GO under these conditions. From the pure sulphur compounds tested, potassium metabisulphite and cysteine was found as the most effective. Wine scavenged 18.01 +/- 2.83% of GO (10 mu mole) whereas potassium metabisulphite addition (7 mu mole) to wine caused additional 20.81% scavenge. In addition, the results indicated that 11.70 +/- 7.07% and 54.48 +/- 6.38% of GO was scavenged by bioaccessible raw and steamed broccoli, respectively. High-resolution mass spectrometry scan analysis confirmed that it was attributed to the addition of GO to both amino acids and sulforaphane (SF)-amino acid adducts under physiological conditions.

Behaviour of Trolox with macromolecule-bound antioxidants in aqueous medium: Inhibition of auto-regeneration mechanism

Food Chemistry, 2018, 243, 428-434

This work aimed at investigating the behaviour of Trolox, vitamin E analogue, in presence of macromolecule-bound antioxidants in aqueous radical medium. Three main groups of macromolecule-bound antioxidants were assayed: dietary fiber (DF), protein and lipid-bound antioxidants, represented by whole wheat, soybean and olive oil products, respectively. Experimental studies were carried out in aqueous ABTS (2,2′-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid)) radical medium. Trolox and macromolecule-bound antioxidants were added to radical separately and together in different concentrations. Antioxidant capacities were determined using QUENCHER procedure. pH of radical media was altered for DF and protein-bound antioxidant studies to examine its effect. Chemometric tools were used for experimental design and multivariate data analysis. Results revealed antagonistic interactions for Trolox with all macromolecule-bound antioxidants. The reason behind this antagonism was investigated through oxidation reactions of Trolox via mass spectrometry analysis. Consequently, a proof was obtained for inhibitory effect of bound-antioxidants on auto-regeneration reactions of Trolox.

Determination of tryptophan derivatives in kynurenine pathway in fermented foods using liquid chromatography tandem mass spectrometry

Food Chemistry, 2018, 243, 420-427

This study aimed to develop an analytical method for the determination of tryptophan and its derivatives in kynurenine pathway using tandem mass spectrometry in various fermented food products (bread, beer, red wine, white cheese, yoghurt, kefir and cocoa powder). The method entails an aqueous extraction and reversed phase chromatographic separation using pentafluorophenyl (PFP) column. It allowed quantitation of low ppb levels of tryptophan and its derivatives in different fermented food matrices. It was found that beer samples were found to contain kynurenine within the range of 28.7 +/- 0.7 mu g/L and 86.3 +/- 0.5 mu g/L. Moreover, dairy products (yoghurt, white cheese and kefir) contained kynurenine ranging from 30.3 to 763.8 +/- g/kg d.w. Though bread samples analyzed did not contain kynurenic acid, beer and red wine samples as yeast-fermented foods were found to contain kynurenic acid. Among foods analyzed, cacao powder had the highest amounts of kynurenic acid (4486.2 +/- 165.6 mu g/kg d.w), which is a neuroprotective compound.

Investigation and kinetic evaluation of the reactions of hydroxymethylfurfural with amino and thiol groups of amino acids

Food Chemistry, 2018, 240, 354-360

In this study, reactions of hydroxymethylfurfural (HMF) with selected amino acids (arginine, cysteine and lysine) were investigated in HMF-amino acid (high moisture) and Coffee-amino acid (low moisture) model systems at 5, 25 and 50 degrees C. The results revealed that HMF reacted efficiently and effectively with amino acids in both high and low moisture model systems. High-resolution mass spectrometry (HRMS) analyses of the reaction mixtures confirmed the formations of Michael adduct and Schiff base of HMF with amino acids. Calculated pseudo-first order reaction rate constants were in the following order; k(Cysteine) > k(Arginine) > k(Lysine) for high moisture model systems. Comparing to these rate constants, the kCysteine decreased whereas, kArginine and kLysine increased under the low moisture conditions of Coffee-amino acid model systems. The temperature dependence of the rate constants was found to obey the Arrhenius law in a temperature range of 5-50 degrees C under both low and high moisture conditions.

Interactions between macromolecule-bound antioxidants and Trolox during liposome autoxidation: A multivariate approach

Food Chemistry, 2017, 237, 989-996

The interactions between free and macromolecule-bound antioxidants were investigated in order to evaluate their combined effects on the antioxidant environment. Dietary fiber (DF), protein and lipid-bound antioxidants, obtained from whole wheat, soybean and olive oil products, respectively and Trolox were used for this purpose. Experimental studies were carried out in autoxidizing liposome medium by monitoring the development of fluorescent products formed by lipid oxidation. Chemometric methods were used both at experimental design and multivariate data analysis stages. Comparison of the simple addition effects of Trolox and bound antioxidants with measured values on lipid oxidation revealed synergetic interactions for DF and refined olive oil-bound antioxidants, and antagonistic interactions for protein and extra virgin olive oil-bound antioxidants with Trolox. A generalized version of logistic function was successfully used for modelling the oxidation curve of liposomes. Principal component analysis revealed two separate phases of liposome autoxidation.

Formation and elimination reactions of 5-hydroxymethylfurfural during in vitro digestion of biscuits

Food Research International, 2017, 99, 308-314

This study investigated the possible formation and elimination reactions of 5-hydroxymethylfurfural (HMF) with amino and sulfhydryl groups in commercial biscuits during simulated in vitro gastrointestinal digestion. At the end of gastric phase, significant increase was observed in HMF contents of biscuits (p < 0.05). By high-resolution mass spectrometry (HRMS) analysis, it was confirmed that sugar dehydration products such as 3-deoxyglucosone and 3,4-dideoxyglucosone accumulated in biscuits during baking were converted to HMF under gastric conditions. However, reactions of HMF with amino acids proceeded with the progress of digestion. HRMS analysis in both HMF-amino acid model systems and in biscuits confirmed that formed HMF reacted with amino and sulfhydryl groups through Michael type addition. In addition, formation of Schiff base during intestinal phases led to a significant decrease in the concentrations of HMF (p < 0.05).

Formation of tyramine in yoghurt during fermentation – Interaction between yoghurt starter bacteria and Lactobacillus plantarum

Food Research International, 2017, 97, 288-295

This study aimed to investigate the formation of tyramine during yoghurt fermentation with the focus on interaction between Streptococcus thermophilus RSKK 04082, Lactobacillus delbrueckii subsp. bulgaricus DSM 20081 and Lactobacillus plantarwn RSKK 02030. These microorganisms were used in the yoghurt fermentation as single strains or mixed cultures containing double or triple strains. The interactions between microorganisms have been also revealed by determining total free amino acids and the pH of the medium together with the microbial count of the strains. It was observed that L. delbrueckii subsp. bulgaricus DSM 20081 did not produce tyramine while S. thermophilus RSKK 04082 and L. plantar RSKK 02030 could produce tyramine depending on the fermentation conditions. Synergistic interactions between S. thermophilus RSKK 04082 and L. delbrueckii subsp. bulgaricus DSM 20081 and, between L. delbrueckii subsp. bulgaricus DSM 20081 and L. plantarum RSKK 02030 were found in terms of tyramine production. It was observed in this study that L. delbrueckii subsp. bulgaricus DSM 20081 had indirect effect on accumulation of tyramine in the yoghurts.

Antioxidants Bound to an Insoluble Food Matrix: Their Analysis, Regeneration Behavior, and Physiological Importance

Comprehensive Reviews in Food Science and Food Safety, 2017, 16(3), 382-399

Dietary antioxidants play an important role in human health by counteracting oxidative stress and preventing chronic diseases. Most common dietary antioxidants in foods are vitamins, carotenoids, phenolic compounds, sulfurcontaining compounds, and neoformed antioxidants. Antioxidants may be present in free soluble or bound insoluble forms in foods. Antioxidants bound to insoluble food matrices have gained the spotlight because they exert their antioxidant effects much longer than free soluble ones. A direct procedure called QUENCHER has been shown to accurately measure the antioxidant capacity of antioxidants bound to insoluble matrices. This procedure overcomes the drawbacks of extraction-dependent classical assays leading to underestimation of the total antioxidant capacity (TAC) of foods. This review focuses on antioxidants that are found naturally in foods or are formed in foods during processing specifically the antioxidants bound to the insoluble food matrices. The literature gap on the importance of bound antioxidants, their physiological relevance, and methods for measurement of their antioxidant capacity will be filled by this comprehensive review. In particular, chemical properties and health effects of food antioxidants, measurement of the TAC of foods by the QUENCHER method, digestion behavior of bound insoluble antioxidants, and their interactions with free soluble antioxidants are discussed throughout this review.

Maillard reaction and caramelization during hazelnut roasting: A multiresponse kinetic study

Food Chemistry, 2017, 221, 1911-1922

A comprehensive kinetic model indicating the elementary steps of Maillard reaction and caramelization during hazelnut roasting was proposed based on a multi-response kinetic modeling approach. Changes in the concentrations of sucrose, fructose, glucose, amino acids, 3-deoxyglucosone, 1-deoxyglucosone, 3,4-dideoxyglucosone, glyoxal, methylglyoxal, dimethylglyoxal, and 5-hydroxymethylfurfural were examined in hazelnuts during roasting at 150, 160 and 170 degrees C for 15, 30, 60, 90, and 120 min. The results suggested that 1,2-enolization was important in the interconversion of glucose and fructose, 5-hydroxymethylfurfural formation mainly proceeded via fructofuranosyl cation dehydration rather than 3-deoxglucosone, glucose contributed more than fructose and fructofuranosyl cation to the early stage of the Maillard reaction. Methylglyoxal and dimethylglyoxal were mainly formed from 1-deoxyglucosone with high reaction rate constants while glyoxal formed through glucose degradation. a-Dicarbonyl compounds could have a role in the formation of melanoidins. The temperature dependence of the reactions was complicated and could not be explained by the Arrhenius equation.

Monitoring protein glycation by electrospray ionization (ESI) quadrupole time-of-flight (Q-TOF) mass spectrometer

Food Chemistry, 2017, 217, 65-73

In this study electrospray ionization quadrupole time-of-flight (ESI-Q-TOF) mass spectrometry was used to investigate protein glycation. The glycated species of cytochrome C, lysozyme, and beta-casein formed during glycation with d-glucose were identified and monitored in binary systems heated at 70 degrees C under dry and aqueous conditions. Cytochrome C had multiple charges in non-glycated state, primarily changing from +13 to +17 positive charges, whereas beta-casein had charge states up to +30. Upon heating with glucose at 70 degrees C in aqueous state, attachment of one glucose molecule onto proteins was observed in each charge state. However, heating in dry state caused much more glucose attachment, leading to the formation of multiple glycoforms of proteins. By using ESI-QTOF-MS technique, formation of glycated cytochrome C containing up to 12 glucose moieties were observed, while glycated species containing 6 and 8 glucose moieties were observed for lysozyme and beta-casein, respectively in various heating conditions.

Extending the shelf-life of pomegranate arils with chitosan-ascorbic acid coating

LWT – Food Science and Technology, 2017, 76, 172-180

The aim of this study was to evaluate the mixture of chitosan and ascorbic acid as an edible coating to extend the shelf-life of pomegranate arils. Pomegranate arils coated with varying concentrations of chitosan and ascorbic acid were stored at 5 +/- 1 degrees C for 28 days. Physical, chemical, microbiological and sensory quality attributes of the arils were determined during storage. There were no significant differences in the contents of anthocyanins, organic acids and sugars for coated and control (uncoated) samples during storage. Chitosan-ascorbic coating helped keeping the visual quality of arils during storage as confirmed by their surface color measurement. Chitosan-ascorbic coating inhibited bacterial and fungal growth on arils. Furthermore, the chitosan-ascorbic acid solution inhibited the mesophilic aerobic bacteria immediately after coating and coated arils presented no growth during storage. The bacterial and fungal growth were analyzed by using the Gompertz model to estimate the microbiological shelf-life of samples. The results revealed that chitosan-ascorbic coating can prolong the lag time of microorganisms and extend the shelf-life of arils up to 21 days during storage at 5 degrees C. Sensory scores (color, taste, aroma) were also higher in chitosan-ascorbic acid coated arils that were quite acceptable even after 25 days of refrigerated storage.

Multiresponse kinetic modelling of Maillard reaction and caramelisation in a heated glucose/wheat flour system

Food Chemistry, 2016, 211, 892-902

The study describes the kinetics of the formation and degradation of alpha-dicarbonyl compounds in glucose/wheat flour system heated under low moisture conditions. Changes in the concentrations of glucose, fructose, individual free amino acids, lysine and arginine residues, glucosone, 1-deoxyglucosone, 3-deoxyglucosone, 3,4-dideoxyglucosone, 5-hydroxymethyl-2-furfural, glyoxal, methylglyoxal and diacetyl concentrations were determined to form a multiresponse kinetic model for isomerisation and degradation reactions of glucose. Degradation of Amadori product mainly produced 1-deoxyglucosone. Formation of 3-deoxyglucosone proceeded directly from glucose and also Amadori product degradation. Glyoxal formation was predominant from glucosone while methylglyoxal and diacetyl originated from 1-deoxyglucosone. Formation of 5-hydroxymethyl-2-furfural from fructose was found to be a key step. Multi-response kinetic modelling of Maillard reaction and caramelisation simultaneously indicated quantitatively predominant parallel and consecutive pathways and rate limiting steps by estimating the reaction rate constants.

Effect of alkalization on the Maillard reaction products formed in cocoa during roasting

Food Research International, 2016, 89, 930-936

Cocoa beans are used in vast variety of food products whether as raw or after alkaline treatment. In this study, cocoa beans were treated with sodium carbonate or water and then roasted together with non-treated cocoa beans. To understand the effect of alkalization on Maillard reaction during cocoa roasting, changes in the concentrations of certain Maillard reaction compounds were determined. Additionally, changes in the concentrations of sugars and modification of lysine were also monitored. Alkaline treatment favored the degradation of sugars in cocoa together with roasting. The concentration of a-dicarbonyl compounds was higher in alkaline treated cocoa compared to water-immersed and non-treated cocoa. Roasting process substantially decreased the concentrations of 3-deoxyglucosone (3-DG), glucosone, glyoxal and diacetyl in alkaline treated cocoa. The concentrations of methylglyoxal and 5-hydroxymethylfurfural (HMF) increased in cocoa samples after roasting although this increase was less in alkaline treated cocoa compared to the other treatments. Most of the lysine was modified within 30 min and fructoselysine, measured as furosine, gradually degraded independent of the treatments, but depending on temperature. N-s-Carboxymethyllysine (CML) was doubled in alkaline treated cocoa although it did not change depending on the roasting.

Effect of sodium chloride on α-dicarbonyl compound and 5-hydroxymethyl-2-furfural formations from glucose under caramelization conditions: A multiresponse kinetic modeling approach

Journal of Agricultural and Food Chemistry, 2016, 64, 6333-6342

This study aimed to investigate the kinetics of α-dicarbonyl compound formation in glucose and glucose–sodium chloride mixture during heating under caramelization conditions. Changes in the concentrations of glucose, fructose, glucosone, 1-deoxyglucosone, 3-deoxyglucosone, 3,4-dideoxyglucosone, 5-hydroxymethyl-2-furfural (HMF), glyoxal, methylglyoxal, and diacetyl were determined. A comprehensive reaction network was built, and the multiresponse model was compared to the experimentally observed data. Interconversion between glucose and fructose became 2.5 times faster in the presence of NaCl at 180 and 200 °C. The effect of NaCl on the rate constants of α-dicarbonyl compound formation varied across the precursor and the compound itself and temperature. A decrease in rate constants of 3-deoxyglucosone and 1-deoxyglucosone formations by the presence of NaCl was observed. HMF formation was revealed to be mainly via isomerization to fructose and dehydration over cyclic intermediates, and the rate constants increase 4-fold in the presence of NaCl.

Effect of chitosan on the formation of acrylamide and hydroxymethylfurfural in model, biscuit and crust systems

Food & Function, 2016, 7, 3431-3436

Chitosan has been popular as a natural food preservative due to its antibacterial and antifungal activities. It may be used in thermally processed foods such as bread to delay staling and improve the microbial stability during the shelf-life. However, the thermal process could lead to the formation of harmful compounds in bakery products through chemical reactions, in which chitosan could take part. Therefore, this study aims to investigate the effect of chitosan on the formation of acrylamide and hydroxymethylfurfural (HMF) in different model systems. Addition of acid to the asparagine–glucose model system decreased the initial rate of acrylamide formation to approx. 4-times. The chitosan included model system contained higher acrylamide than the asparagine–glucose–acid model but still lower than the asparagine–glucose model system. The HMF content was decreased in the presence of acid due to acid-catalyzed degradation. Additionally, HMF is a potent carbonyl source and utilized in the Maillard reaction. In biscuit samples, addition of acid or chitosan solution to the dough did not significantly affect the acrylamide formation (p > 0.05), however addition of acid increased the formed HMF. In crust samples, acrylamide formation was decreased by acid, while chitosan showed no additional decrease. No interaction was found between HMF and chitosan. The results suggest that the effect of chitosan should be carefully evaluated apart from the effect of acid, in which chitosan was solubilized.

Investigations on the reactions of α-dicarbonyl compounds with amino acids and proteins during in vitro digestion of biscuits

Food & Function, 2016, 7, 2544-2550

This study investigated the interactions of reactive α-dicarbonyl compounds, particularly methylglyoxal (MGO) and 3-deoxyglucosone (3-DG), in commercial biscuits during gastrointestinal digestion. An in vitro multi-step enzymatic digestion system simulating gastric, duodenal and colon phases was used. MGO and 3-DG concentrations decreased with the progress of digestion. Model systems composed of MGO and lysine, cysteine or ovalbumin and model biscuits containing lysine, cysteine or ovalbumin were subjected to in vitro digestion. The results revealed that disappearance in dicarbonyl contents was due to interactions of reactive dicarbonyl compounds with the accumulating amino acids during digestive process. By a high resolution mass spectrometry analysis in model systems and biscuits, the formation of adducts of dicarbonyl compounds with amino or sulfhydryl groups of amino acids was confirmed.

Bioactive compounds in different hazelnut varieties and their skins

Journal of Food Composition and Analysis, 2015, 43, 203-208

Bioactive profiles of hazelnut skins belonging to fourteen hazelnut varieties were identified. Concentration of phenolic compounds, flavonoids and phenolic acids in soluble free, conjugated soluble and insoluble bound fractions together with their total concentrations were presented. In addition, tocopherol content and total antioxidant capacity of hazelnuts and their skins were revealed. Concentration of total phenolic compounds ranged between 51.9 and 203.1 mg gallic acid equivalent/g of skin among varieties, which is in accordance with the total antioxidant capacity. Total flavonoid content was almost 60% of the total phenolic compounds. Flavonoids and phenolic acids were found to be concentrated mostly in the conjugated soluble fraction. Tocopherol contents of hazelnut skins ranged from 226 to 593 mu g/g, and alpha-tocopherol was the most abundant. Total antioxidant capacity was between 309 and 1375 mu mol Trolox equivalent/g of hazelnut skins, which is more than 100 times higher than for hazelnuts without the skins.

Synergism between soluble and dietary fiber bound antioxidants

Journal of Agricultural and Food Chemistry, 2015, 63, 2338-2345

This study investigates the synergism between antioxidants bound to dietary fibers (DF) of grains and soluble antioxidants of highly consumed beverages or their pure antioxidants. The interaction between insoluble fractions of grains containing bound antioxidants and soluble antioxidants was investigated using (i) a liposome-based system by measuring the lag phase before the onset of oxidation and (ii) an ESR-based system by measuring the reduction percentage of Fremy’s salt radical. In both procedures, antioxidant capacities of DF-bound and soluble antioxidants were measured as well as their combinations, which were prepared at different ratios. The simple addition effects of DF-bound and soluble antioxidants were compared with measured values. The results revealed a clear synergism for almost all combinations in both liposome- and ESR-based systems. The synergism observed in DF-bound−soluble antioxidant system paints a promising picture considering the role of fiber in human gastrointestinal (GI) tract health.

Mechanism of the interaction between insoluble wheat bran and polyphenols leading to increased antioxidant capacity

Food Research International 2015, 69, 189-193

This study aimed to provide an in-depth investigation of the interaction between insoluble wheat bran and polyphenols. Treatment with tannic acid, but not gallic acid, increased the bound antioxidant capacity of insoluble wheat bran depending on its aqueous concentration (p < 0.05). Among the beverages tested (white and red wines, black and green tea infusions), treatment with green tea infusion caused the highest increase in the total antioxidant capacity. Temperature, time, air and pH were found to significantly affect the reaction between insoluble wheat bran and polyphenols. The bound antioxidant capacity of insoluble bran increased to above 100 mmol after treatment with green tea infusion at optimum conditions (50 degrees C, pH 9.0, no airflow). Concentration of free amino groups available in wheat bran significantly decreased (59.5%) after the treatment The results suggested that polyphenols are oxidized to quinones under alkaline conditions further bound to free amino groups available on the surface of wheat bran.

Effects of hydrophobic and ionic interactions on glycation of casein during Maillard reaction

Journal of Agricultural and Food Chemistry, 2014, 62, 11289-11295

This study aimed to investigate the effects of hydrophobic and ionic interactions on glycation of native and high-shear treated casein during heating. Casein–epicatechin and casein–calcium complexes were formed and glycated with glucose at different temperatures ranging from 70 to 150 °C in solution and dry states. Furosine, acid derivative of N-ε-fructoselysine (FL), and N-ε-carboxymethyl lysine (CML) were measured as indicators of early and advanced glycation, respectively. CML concentrations of casein–epicatechin and casein–calcium complexes heated in solution were significantly lower as compared to the control (p < 0.05). For instance, 182 ± 9.78 μg/g of CML formed in the control, while CML concentrations were 136 ± 10.7 and 101 ± 7.37 μg/g in casein–epicatechin and casein–calcium complexes, respectively, heated at 150 °C in the solution state. Treatment by high shear microfluidization further decreased the CML formed during heating at 70 °C in dry state. The results suggest that interactions with epicatechin molecule and calcium ion could be a useful strategy to limit advanced glycation of casein under certain conditions.

Investigation of the reactions of acrylamide during in vitro multistep enzymatic digestion of thermally processed foods

Food & Function, 2015, 6, 109-114

This study aimed to investigate the fate of acrylamide in thermally processed foods after ingestion. An in vitro multistep enzymatic digestion system simulating gastric, duodenal and colon phases was used to understand the fate of acrylamide in bakery and fried potato products. Acrylamide levels gradually decreased through gastric, duodenal and colon phases during in vitro digestion of biscuits. At the end of digestion, acrylamide reduction ranged between 49.2% and 73.4% in biscuits. Binary model systems composed of acrylamide and amino acids were used to understand the mechanism of acrylamide reduction. High-resolution mass spectrometry (HRMS) analyses confirmed Michael type addition of amino acids to acrylamide during digestion. Contrary to bakery products, acrylamide levels increased significantly during gastric digestion of fried potatoes. The Schiff base formed between reducing sugars and asparagine disappeared rapidly meanwhile acrylamide level increased during the gastric phase. This suggests that intermediates like the Schiff base accumulated in potatoes during frying are potential precursors of acrylamide under gastric conditions.

Mitigation of acrylamide and hydroxymethylfurfural in biscuits using a combined partial conventional baking and vacuum post-baking process: Preliminary study at the lab scale

Innovative Food Science & Emerging Technologies, 2014, 26, 265-270

A combined conventional and vacuum process was introduced as a new baking technology to mitigate acrylamide and 5-hydroxymethylfurfural (HMF) in biscuits in this study. Firstly, these processes were compared for acrylamide and HMF formations, drying rate, and browning development at different temperatures. Acrylamide concentrations in biscuits attained during vacuum baking were significantly lower than those attained during conventional baking at all temperatures studied (p < 0.05). Besides, there was no HMF formation in biscuits during vacuum baking. Comparing to conventional baking, heating under lower pressure provided lower time-temperature profile with slightly accelerated evaporation of water in dough. However, development of surface browning was lacking in vacuum baked biscuits. Secondly, combinations of conventional and vacuum processes were used to produce biscuits. The dough that was partially baked at 220 degrees C for 2-4 min under conventional conditions was post-baked under vacuum for accelerated drying at 180 degrees C and 500 mbar for 4-6 min until the desired final moisture content was attained. Doing so, exposure of biscuits to higher temperatures for longer time, which was essential to facilitate the chemical reactions leading to thermal process contaminants, was prevented. The combined process formed no acrylamide or HMF (<LOQ) in biscuits. It was considered as a promising alternative to produce safer biscuits for targeted consumers like infants.

Industrial relevance: The study has been performed in the course of the FP7 project PROMETHEUS that aimed to develop new or alternative technologies for the mitigation of thermal processing contaminants in foods. Mitigation of thermal processing contaminants, especially acrylamide in heated foods has been an intensive area of research in the last decade. It was confirmed repeatedly by many researchers that increasing processing temperature also increases the formation rates of those undesired compounds. Therefore, one approach to mitigate them is to lower temperature during processing. However, this is not viable practically, because lowering temperature requires longer time to achieve desired final moisture contents in the final product. The approach presented in this manuscript takes the advantage of faster drying of biscuits during heating under vacuum. Using the combination of conventional par-baking with vacuum post-baking seems to produce safer biscuits than the conventional counterparts in terms of their acrylamide and HMF contents. At industrial level vacuum application has been used in bread processing for cooling purposes. In that case, breads are cooled rapidly after baking in semi-continuous vacuum chambers. As implementation of vacuum application into the process has already been practiced, it is likely that partially baked biscuits could be post-baked for short times in semi-continuous vacuum chambers maintained at specified conditions. To the best of our knowledge, such combined baking process has not been investigated to date for the mitigation of thermal processing contaminants in biscuits. So, it is believed that the results of present manuscript would be interesting for bakery industry dealing with the above-mentioned safety problem, but also for the readers of this journal.

Investigation of alpha-dicarbonyl compounds in baby foods by high-performance liquid chromatography coupled with electrospray ionization mass spectrometry

Journal of Agricultural and Food Chemistry, 2014, 62, 7714-7720

Baby foods are exposed to elevated temperatures during processing treatments such as sterilization or spray drying. These treatments decompose sugars leading to the formation of a-dicarbonyl compounds that are of importance since they have been associated with several metabolic disorders. In this study, an analytical method based on high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) was used to determine a-dicarbonyl compounds in baby foods. The method entailed aqueous extraction of a-dicarbonyl compounds from the samples and derivatization with o-phenylenediamine prior to chromatographic analysis. The results indicated that major degradation product was 3-deoxyglucosone in the samples including cereal-based infant formula, canned fruit and vegetable puree. Its concentration ranged between 3.9 and 827.1 mg/kg in infant formula and between 26.7 and 92.3 mg/kg in fruit puree samples. The concentrations of glucosone, 1-deoxyglucosone, 5-hydroxymethy1-2-furfural, furfural, glyoxal, methylglyoxal, and dimethylglyoxal levels were rather low.

Formation of monochloropropane-1,2-diol and its esters in biscuits during baking

Journal of Agricultural and Food Chemistry, 2014, 62, 7297-7301

The formation of free monochloropropane-1,2-diol (3-MCPD and 2-MCPD) and its esters (bound-MCPD) was investigated in biscuits baked with various time and temperature combinations. The effect of salt as a source of chloride on the formation of these processing contaminants was also determined. Kinetic examination of the data indicated that an increasing baking temperature led to an increase in the reaction rate constants for 3-MCPD, 2-MCPD, and bound-MCPD. The activation energies of formation of 3-MCPD and 2-MCPD were found to be 29 kJ mol(-1). Eliminating salt from the recipe decreased 3-MCPD and 2-MCPD formation rate constants in biscuits by 57.5 and 85.4%, respectively. In addition, there was no formation of bound-MCPD in biscuits during baking without salt. Therefore, lowering the thermal load or limiting the chloride concentration should be considered a means of reducing or eliminating the formation of these contaminants in biscuits. Different refined oils were also used in the recipe to test their effect on the occurrence of free MCPD and its esters in biscuits. Besides the baking process, the results also confirmed the role of refined oil in the final concentration of these contaminants in biscuits.

Mitigation of acrylamide and hydroxymethyl furfural in instant coffee by yeast fermentation

Food Research International 2014, 61, 252-256

Acrylamide being known as carcinogenic and hydroxymethyl furfural (HMF) being known as cytotoxic compounds are heat induced process contaminants found in instant coffee. Today’s instant coffee production method involves roasting of coffee beans, grinding, flavor and aroma separation, extraction, concentration, and drying steps. During roasting, acrylamide and HMF are formed in varying amounts depending upon the degree of heat treatment as a result of the Maillard reaction. This study was conducted in order to reduce the concentrations of acrylamide and HMF in instant coffee. Instant coffee (20%, w/v) was mixed with sucrose (0-10, w/v) and baker’s yeast (Saccharomyces cerevisiae, 1-2%, w/v) in a tightly closed glass vessel. The mixture was fermented at 30 degrees C for 48 h. The kinetics of acrylamide and HMF degradation was investigated. HMF and acrylamide contents were reduced exponentially at varying rates, depending upon fermentation medium and time. After 24 h, HMF concentration was decreased by 61.2%, 75.7%, 93.6% and 99.2% in the fermentation media containing none, 1%, 5%, and 10% of sucrose, respectively. After 48 h, acrylamide concentration was decreased by about 70%. These results revealed that yeast fermentation is promising for the mitigation of HMF and acrylamide in instant coffee. (C) 2013 Elsevier Ltd. All rights reserved.

Hazelnut skin powder: A new brown colored functional ingredient

Food Research International 2014, 65, 291-297

Hazelnut skin arises as a by-product in the roasting process of hazelnuts. This study aimed to investigate the potential of its utilization as a brown colored functional ingredient. Chemical composition analyses revealed that hazelnut skin is a very rich source of dietary fibers (67.7%) and phenolic compounds (233 mg GAE/g). Its oil fraction (14.5%) was found to contain very high amounts of tocopherols (2.77 mu g/g) and oleic acid (75.2%). After defatting, coarse and fine hazelnut skin powders were obtained by low and high shear homogenization. High shear homogenization was performed at different pressures (10, 20 and 30 ksi) for different pass cycles (1, 3, 5 and 10). The powder samples were analyzed for particle size distribution, color, individual phenolic compounds, total phenolic content, and total antioxidant capacity. A desirable low micron particle size for the hazelnut skin for incorporation into food formulations was achieved by means of high shear homogenization, meanwhile there was no significant change in phenolic composition and antioxidant capacity.

Formation of melatonin and its isomer during bread dough fermentation and effect of baking

Journal of Agricultural and Food Chemistry, 2013, 62, 2900-2905

Melatonin is produced mainly by the pineal gland in vertebrates. Also, melatonin and its isomer are found in foods. Investigating the formation of melatonin and its isomer is of importance during bread dough fermentation and its degradation during baking since bread is widely consumed in high amounts. Formation of melatonin was not significant during dough fermentation. The melatonin isomer content of nonfermented dough was found to be 4.02 ng/g and increased up to 16.71 ng/g during fermentation. Lower amounts of isomer in crumb and crust than dough showed that the thermal process caused a remarkable degree of degradation in melatonin isomer. At the end of the 180 mm fermentation Trp decreased by 58%. The results revealed for the first time the formation of a melatonin isomer in bread dough during yeast fermentation.

Kinetics of furan formation from ascorbic acid during heating under reducing and oxidizing conditions

Journal of Agricultural and Food Chemistry, 2013, 61 (42), pp 10191–10196

This study aimed to investigate the effect of oxidizing and reducing agents on the formation of furan through ascorbic acid (AA) degradation during heating at elevated temperatures (≥100 °C) under low moisture conditions. To obtain these conditions, oxidizing agent, ferric chloride (Fe), or reducing agent, cysteine (Cys), was added to reaction medium. Kinetic constants, estimated by multiresponse modeling, stated that adding Fe significantly increased furan formation rate constant, namely 369-fold higher than that of control model at 100 °C. Rate-limiting step of furan formation was found as the reversible reaction step between intermediate (Int) and diketogluconic acid (DKG). Additionally, Fe decreased activation energy of AA dehydration and furan formation steps by 28.6% and 60.9%, respectively. Results of this study are important for heated foods, fortified by ferric ions and vitamins, which targets specific consumers, e.g. infant formulations.