Ethanol in food: liquid–vapour partition in model systems containing Maillard reaction products

The effect of Maillard reaction products (MRPs) with different browning degree on the liquid–vapour partition of ethanol was studied in model systems. In particular, glucose–glycine aqueous solutions subjected to different heat treatments, which consequentely had different water activity values, were added to increasing amounts of ethanol and analysed for ethanol vapour pressure. In order to study the effects of the water activity change and of melanoidins' formation on the ethanol partition, experiments were also carried out on samples equilibrated at the same water activity. Ethanol vapour pressure decreased as the Maillard reaction proceeded. This result was attributed to the increase in water activity rather than to binding effects of melanoidins towards ethanol. Changes in water activity were mainly due to reagent consumption, water molecule formation and melanoidin production.     

Biological activities and physicochemical properties of Maillard reaction products in sugar–bovine casein peptide model systems

The purpose of this study was to evaluate the biological activities and physicochemical properties of Maillard reaction products (MRPs), derived from aqueous reducing sugar (ribose, galactose and lactose) and bovine casein peptide (BCP) model systems. The fluorescence intensity of ribose-BCP MRPs reached the maximum value within 1 h, while it took 3 h for galactose-BCP MRPs. Size exclusion chromatography of all the MRPs indicated molecular rearrangements and production of new smaller molecules, as a function of the heating time. The consumption of ribose and amino groups was the highest in the ribose-BCP MRPs. BCP lost its known angiotensin-I-converting enzyme (ACE) inhibitory activity by the Maillard reaction with reducing sugars. Ribose–BCP MRPs had the lowest ACE inhibitory activity, but they showed the highest 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging activity and ferrous reducing power among all the MRPs. Galactose-BCP MRPs inhibited, slightly the growth of Caco-2 cells, while ribose-BCPand lactose-BCP MRPs had no cytotoxicity.     

Identification and quantification of α-dicarbonyl compounds produced in different sugar-amino acid Maillard reaction model systems

A mixture of α-dicarbonyl compounds generated from Maillard reaction (MR) model systems, comprising of fructose with glycine (Fru-Gly) and lysine (Fru-Lys); glucose with glycine (Glu-Gly) and lysine (Glu-Lys); ribose with glycine (Rib-Gly) and lysine (Rib-Lys), were identified and quantified. α-Dicarbonyl compounds generated in the hexose models were predominantly glucosone and 3-deoxyglucosone (3-DG), with 3-deoxypentosone (3-DP) and pentosone being the major α-dicarbonyls produced in the pentose models. Ethyl acetate extraction of model MRPs resulted in poor recovery of 2,3-diaminonaphthalene benzoquinoxalines of glucosone, 3-DG, pentosone, 3-DP and methylglyoxal (MGO), respectively. The temporal profiles of pentosone, 3-DP, glyoxal (GO) and MGO were similar in the pentose models, with maximum concentration occurring within 5 min. These four α-dicarbonyl compounds were higher (P < 0.05) in Rib-Gly than in Rib-Lys MR systems. The quantity of α-dicarbonyl compounds was affected by the interaction among the type of sugar and amino acid and the reaction time. The type of sugar is the most important factor that affected both the quantity and quality of α-dicarbonyl compounds produced in MR mixtures.     

Biological activities of Maillard reaction products (MRPs) in a sugar–amino acid model system

The various biological activities of Maillard reaction products (MRPs) from sugar (fructose and glucose) and 20 amino acid model systems were evaluated. Colour development, in vitro antioxidant, α-glucosidase inhibitory, antihypertensive, and antiproliferative activities of aqueous solutions of MRPs produced by heating at 130 °C for 2 h were measured. The fructose–amino acid mixture showed higher UV-absorbance and browning intensity than the glucose–amino acid mixture. The fructose–amino acid model MRPs showed higher DPPH and ABTS radical scavenging and ACE inhibitory activities than the glucose–amino acid model MRPs. The α-glucosidase inhibitory effect of MRPs derived from fructose– and glucose–tyrosine showed higher α-glucosidase inhibitory activity than that of other MRPs. Sugar–amino acid model MRPs inhibited the growth of HCT116 colon cancer cell in a dose-dependent manner (from 0.5 to 1.5 mg/ml). Glucose MRPs showed slightly higher antiproliferative activity than fructose MRPs. In particular, sugar–tryptophan and –tyrosine MRPs exerted higher biological activities than the other MRPs.     

Structure and antioxidant activity of β-lactoglobulin-glycoconjugates obtained by high-intensity-ultrasound-induced Maillard reaction in aqueous model systems under neutral conditions

Sonication is a new processing technology in the dairy industry. The aim of this study was to test glycation of β-lactoglobulin (BLG) in Maillard reaction (MR) induced by high-intensity ultrasound in aqueous solution under neutral conditions at 10–15 °C, which is not favourable for the MR. BLG was sonicated in the presence of glucose, galactose, lactose, fructose, ribose and arabinose. Formation of Maillard reaction products (MRPs) was monitored by mass spectrometry, spectrophotometry and fluorimetry. Ultrasound treatment resulted in formation of MRPs with all tested carbohydrates. Ribose induced the highest degree of modification resulting in 76% of BLG modified and an average of three anhydroribose units attached. Circular dichroism spectra analyses indicated only minor alterations in secondary and tertiary structures. MRP obtained by ultrasound exhibited 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity and possessed increased iron-chelating activity and reducing power. High-intensity ultrasound efficiently promotes BLG-glycoconjugates formation by MR in aqueous solutions under non-denaturing conditions.     

Effect of oxidation and hydrolysis of porcine myofibrillar protein on Nε-carboxymethyl-lysine formation in model systems

This study investigated the effects of oxidation and hydrolysis of porcine myofibrillar protein (MFP) on N^ε-carboxymethyl-lysine (CML) formation in model systems. Model systems of MFP/oxidised linoleic acid (MFP/OLA), mildly oxidised MFP/OLA (MO-MFP/OLA), severely oxidised MFP/OLA (SO-MFP/OLA), mildly hydrolysed MFP/OLA (MH-MFP/OLA) and severely hydrolysed MFP/OLA (SH-MFP/OLA) were incubated, and CML content was determined. Compared with MFP/OLA (39.1 ± 5.7 ng mg⁻¹ protein), there was a significant increase of CML in MO-MFP/OLA (53.9 ± 2.5 ng mg⁻¹ protein), whereas a marked decrease was observed in SO-MFP/OLA (25.1 ± 4.4 ng mg⁻¹ protein) during incubation. CML level increased with increasing degree of hydrolysis of MFP after 6 days of incubation. Therefore, mildly oxidised MFP and hydrolysed MFP could promote CML formation, while severely oxidised MFP impeded CML generation. These results suggested that effects of oxidation and hydrolysis of MFP on CML generation were mainly dependent on the degree of structural changes of MFP.     

Techniques for localisation of konjac glucomannan in model milk protein–polysaccharide mixed systems: Physicochemical and microscopic investigations

The effect of conjugating konjac glucomannan with fluorescein isothyocyanate (FITC) via covalent labelling on selected physicochemical properties of FITC and konjac was investigated using spectrophotometry, rheometry, and size exclusion chromatography (SEC). The binding of the lectin concanavalin A (ConA) to sugar residues of konjac was investigated using SEC. Covalent conjugation of konjac with FITC led to a shift in the absorbance spectrum peak of FITC to a lower wavelength and a decrease in the average molecular weight distribution of konjac. Furthermore, covalently labelled konjac showed reduced apparent viscosity compared to unlabelled konjac. ConA bound to the sugar residues in konjac. The potential of konjac–FITC covalent labelled conjugate or konjac–lectin labelled ConA complexes as fluorescent markers for localisation of konjac in a phase separated micellar casein–konjac mixture was investigated using confocal laser scanning microscopy. Results indicated that covalently labelled konjac has microscopic phase behaviour similar to that of un-labelled konjac and are therefore suitable for localising konjac glucomannan in a phase-separated micellar casein–konjac system.     

Potential DNA–protein cross-link products formed by sugar degradation products: identification of N 6-[2-(N 2-2′-deoxyguanosyl)propionyl]lysine

Sugar degradation products are formed during heat treatment of food as well as endogenously in vivo. As reactive carbonyl compounds, they react readily with proteins or DNA to form protein- or DNA-bound advanced glycation end products (glycation reaction or Maillard reaction). In this study, we investigated the formation of potential DNA–protein cross-link products from sugar degradation products. 2-Deoxyguanosine, l-lysine and different carbohydrates were incubated at 37 °C. The sugar degradation products dihydroxyacetone and d,l-glyceraldehyde lead to the formation of two new cross-link products. The new compounds were isolated by preparative high-performance liquid chromatography and identified by spectral data as the two diastereomers of N⁶-[2-(N²-2-deoxyguanosyl)propionyl]lysine. In this structure, the -amino group of lysine and the exocyclic amine group of 2-deoxyguanosine are linked via a carboxyethyl group, derived from the carbohydrate component. The binding sites and the binding types were confirmed by synthesis of the analogous products from N²-(1-carboxyethyl)guanosine and N-acetyllysine methyl ester.Dedicated to Professor Th. Severin on the occasion of his 75^th birthday     

Kinetics of the decomposition of [2Fe–2S] ferredoxin from spinach: implications for iron bioavailability and nutritional status

The decomposition of spinach ferredoxin has been studied, at 37°C, in the presence of: buffer (pH 7.5); water; 0.01 M hydrochloric acid; and 0.01 M hydrochloric acid with pepsin enzyme (0.09, 0.19 and 0.38%). The hydrolysis of the protein appears to occur slowly in the presence of water alone, but is greatly accelerated by the addition of acid. This hydrolysis reaction is proposed to involve the denaturation of the protein chain to the extent that the [2Fe–2S] core is released from the protein. In the presence of 0.01 M HCl, total iron release occurs. Pepsin appears to then breakdown the peptide linkages within the apoprotein. UV–visible spectroscopy has demonstrated a two stage reaction with loss of the peak at 422 nm correlating with breakdown and loss of the [2Fe–2S] cluster, and loss of the peak at 277 nm demonstrating breakdown of the protein chain. Uniphasic kinetics were observed at 422 nm with the observed pseudo-first order rate constant having a linear dependence on ferredoxin concentration.     

银川:宁夏大学,2017. [45]Alaejos M S,Afonso A M. Factors that affect the content of heterocyclic aromatic amines in foods[J]. Comprehensive Reviews in Food Science & Food Safety,2011,10(2):52-108. [46]姚瑶. 酱牛肉中常见杂环胺化合物的形成与控制研究[D]. 南京:南京农业大学,2013. 稳定同位素技术 在农产品产地溯源中的应用

农产品溯源技术是为保护地区品牌和特色产品,防止食品掺假和食源性疾病扩散,确保食品安全,降低公司召回成本而建立起来的一项追踪检测技术。建立高效的食品溯源体系是保证食品质量安全的关键,近年来稳定同位素技术因没有放射性、灵敏度高、可靠性强等优点,已广泛用于鉴别不同产地、不同食源的各种农产品,成为追溯食品来源的一种有效手段。文中系统阐述了稳定同位素技术在谷物、肉制品、果蔬、果汁饮料、葡萄酒、乳制品、水产品等各类食品在产地溯源方面的应用,进一步剖析了稳定同位素技术在我国农产品产地溯源中的优势及局限性,并对其发展前景进行展望,以期为我国农产品溯源体制的建立提供借鉴,推动稳定同位素技术在食品溯源中的应用。     

Inhibition of mutagenic N-nitroso compound formation in sausage samples by using -ascorbic acid and α-tocopherol

In this study 24 samples of sausage with different amounts of nitrite, -ascorbic acid and α-tocopherol were prepared in order to determine the inhibitory effects of -ascorbic acid and α-tocopherol as reductants against formation of mutagenic N-nitroso compounds that form in cured meat products. These mutagenic N-nitroso compounds were extracted by phosphate buffer and ethylacetate. The mutagenicity of extracts were investigated by salmonella/microsome assay. The number of revertants indicated the N-nitroso compounds content. Among the Salmonella typhimurium strains tested, the revertants of S. typhimurium TA100 were significantly reduced (P<0.5) by 60% when reductants were added to the samples.