Evolution of protein bound Maillard reaction end-products and free Amadori compounds in low lactose milk in presence of fructosamine oxidase I

Effect of brewer's spent grain melanoidins on maillard reaction products during storage of whey protein model systems

Maillard reaction readily takes place in dairy products because of the association between thermal treatments, extended storage and the matrix composition. Along with the impairment of protein digestion, the formation of glycation and α-dicarbonyl compounds is a concern for quality attributes of whey proteins when used as ingredients. In this paper, we outline the capacity of brewer's spent grain melanoidins in reducing the accumulation of α-dicarbonyl compounds, thus controlling the formation of dietary advanced glycation end-products in accelerated shelf life at 35 °C. Results revealed that brewer's spent grain melanoidins targeted methylglyoxal and glyoxal reactivity leading to the reduction of N-ε-carboxymethyllysine and methylglyoxal-hydroimidazolone up to 27 and 60%, respectively. We here describe that the presence of melanoidins is instrumental in limiting the undesired effects of α-dicarbonyl compounds on whey proteins.

Application of PLSR in correlating sensory and chemical properties of middle flue-cured tobacco leaves with honey-sweet and burnt flavour

Among the eight types of aroma and flavour characteristics of Chinese flue-cured tobacco (FCT), tobacco grown in Shandong is classified as having a honey-sweet and burnt aroma. To elucidate the key chemical components that determine the characteristics of the honey-sweet and burnt aroma styles of Shandong FCT, we qualitatively and quantitatively evaluated the smoke flavour quality and five categories of flavour-related chemical components (routine components, water-soluble sugars, free amino acids, Amadori compounds and key aroma-active compounds) in Shandong middle FCT leaves using sensory analysis and modern instrumental analysis techniques. The association between the chemical components and sensory quality was analysed. Our results showed that the total sugars, reducing sugars (fructose, glucose, and psicose), total sugar-nicotine ratio, proline-total amino acid ratio, sulphur-containing amino acid-total amino acid ratio and fructosyl-proline (Fru-Pro) were high in premium FCT leaves. The aroma-active compounds associated with the honey-sweet burnt flavour style of the Shandong Middle FCT included sweet-scented 2,3-pentanedione, 2,3-butanedione, butyrolactone, 2-furanmethanol, roasted-like 2-pentylfura, and green-like 1-penten-3-one. Partial least squares regression (PLSR) analysis revealed that 29 aroma precursors were positively correlated with the sensory quality characteristics of Shandong FCT. The results of our study can provide guidance for the targeted improvement and precise regulation of the flavour-style characteristics of Shandong FCT.

Non-canonical food sources: bacterial metabolism of Maillard reaction products and its regulation

Proteins are an important part of our regular diet. During food processing, their amino acid composition can be chemically altered by the reaction of free amino groups with sugars - a process termed glycation. The resulting Maillard reaction products (MRPs) have low bioavailability and thus predominantly end up in the colon where they encounter our gut microbiota. In the following review, we summarize bacterial strategies to efficiently metabolize these non-canonical amino acids. A particular focus will be on the complex regulatory mechanisms that allow a tightly controlled expression of metabolic genes to successfully occupy the ecological niches that result from the chemical diversity of MRPs.

Influence of Pasteurization on Maillard Reaction in Lactose-Free Milk

In order to improve the safety and quality of lactose-free milk (LFM) Maillard reaction products (MRPs), this study used raw cow's milk as raw material and lactase hydrolysis to prepare LFM, which was heat-treated using pasteurization and then placed in storage temperatures of 4 °C, 25 °C and 37 °C to investigate the changes in the Maillard reaction (MR). The results of the orthogonal test showed that the optimal conditions for the hydrolysis of LFM are as follows: the hydrolysis temperature was 38 °C, the addition of lactase was 0.03%, and the hydrolysis time was 2.5 h. Under these conditions, the lactose hydrolysis rate reached 97.08%, and the lactose residue was only 0.15 g/100 g as determined by high-performance liquid chromatography (HPLC), complying with the standard of LFM in GB 28050-2011. The contents of furoamic acid and 5-hydroxymethylfurfural were determined by high-performance liquid chromatography, the color difference was determined by CR-400 color difference meter, and the internal fluorescence spectrum was determined by F-320 fluorescence spectrophotometer. The test results showed that the variation range of furosine in lactose-free milk after pasteurization was 44.56~136.45 mg/100g protein, the range of 5-hydroxymethylfurfural (HMF) was 12.51~16.83 mg/kg, the color difference ranges from 88.11 to 102.53 in L*, from -0.83 to -0.10 in a*, and from 1.88 to 5.47 in b*. The furosine content of LFM during storage at 4, 25, and 37 °C ranged from 44.56 to 167.85, 44.56 to 287.13, and 44.56 to 283.72 mg/100 g protein, respectively. The average daily increase in protein content was 1.18-3.93, 6.46-18.73, and 15.7-37.66 mg/100 g, respectively. The variation range of HMF was 12.51~17.61, 12.51~23.38, and 12.51~21.1 mg/kg, and the average daily increase content was 0.03~0.07, 0.47~0.68, and 0.51~0.97 mg/kg, respectively. During storage at 4 °C, the color difference of LFM ranged from 86.82 to 103.82, a* ranged from -1.17 to -0.04, and b* ranged from 1.47 to 5.70. At 25 °C, color difference L* ranges from 72.09 to 102.35, a* ranges from -1.60 to -0.03, b* ranges from 1.27 to 6.13, and at 37 °C, color difference L* ranges from 58.84 to 102.35, a* ranges from -2.65 to 1.66, and b* ranges from 0.54 to 5.99. The maximum fluorescence intensity (FI) of LFM varies from 131.13 to 173.97, 59.46 to 173.97, and 29.83 to 173.97 at 4, 25, and 37 °C. In order to reduce the effect of the Maillard reaction on LFM, it is recommended to pasteurize it at 70 °C-15 s and drink it as soon as possible during the shelf life within 4 °C.

Promoted Formation of Pyrazines and Sulfur-Containing Volatile Compounds through Interaction of Extra-Added Glutathione or Its Constituent Amino Acids and Secondary Products of Thermally Degraded N-(1-Deoxy-d-ribulos-1-yl)-Glutathione

An Amadori rearrangement product (ARP) derived from ribose (Rib) and glutathione (GSH) was prepared and identified as N-(1-deoxy-d-ribulos-1-yl)-glutathione by ultraperformance liquid chromatography-tandem mass spectrometry and NMR. Thermal treatment of the ARP aqueous solution was conducted, and a relatively high temperature was found to accelerate the degradation of the ARP. The concentration of furans formed at 120 °C was more than 6.39 times that at 100 °C, and especially, the high temperature favored the formation of furfural and 4-hydroxy-5-methyl-3(2H)-furanone through deoxyosone dehydration. The promoting role of extra-added GSH or its constituent amino acids was investigated in the volatile formation during thermal processing of the ARP. Both, the added GSH and its constituent amino acids, could timely capture glyoxal (GO) and methylglyoxal (MGO) to facilitate Strecker degradation, which improved pyrazine formation. Compared with glycine and glutamic acid, cysteine was the most effective extra-added amino acid to react with GO and MGO to produce pyrazine and methylpyrazine. More importantly, the cysteine degraded from extra-added GSH effectively accelerated the generation of sulfur-containing volatile compounds through the reaction of cysteine degradation products with furans and shorter-chain α-dicarbonyl compounds.

Exceptionally versatile take II: post-translational modifications of lysine and their impact on bacterial physiology

Among the 22 proteinogenic amino acids, lysine sticks out due to its unparalleled chemical diversity of post-translational modifications. This results in a wide range of possibilities to influence protein function and hence modulate cellular physiology. Concomitantly, lysine derivatives form a metabolic reservoir that can confer selective advantages to those organisms that can utilize it. In this review, we provide examples of selected lysine modifications and describe their role in bacterial physiology.

Maillard reaction harmful products in dairy products: Formation, occurrence, analysis, and mitigation strategies

Various harmful Maillard reaction products such as lactulosyl-lysine (furosine), furfurals, and advanced glycation end products (AGEs) could be formed during the thermal processing of dairy products, which could lead to various chronic diseases. In this review, the furosine, furfurals, and AGEs formation, occurrence, analysis methods, and toxicological and health aspects in various dairy products were summarized to better monitor and control the levels of harmful Maillard reaction products in processed dairy products. It was observed that all types of dairy products, including raw milk, contain harmful Maillard reaction products, with the highest in whey cheese and condensed milk. High-performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) is the common method for the determination of furosine and furfurals and AGEs in dairy products, respectively. However, the simple, rapid, environment-friendly, and accurate methods of determination are still to be developed. Incorporating resveratrol, pectin oligosaccharides (POS) in milk are effective methods to inhibit AGEs formation. This review provides a guide not only for consumers regarding the selection and consumption of dairy products, but also for monitoring and controlling the quality of dairy products.

Dietary advanced glycation end-products, 2-monochloropropane-1,3-diol esters and 3-monochloropropane-1,2-diol esters and glycidyl esters in infant formulas: Occurrence, formulation and processing effects, mitigation strategies

Infant formula contains thermal processing contaminants, such as dietary advanced glycation end-products (dAGEs), glycidyl esters (GEs), 2-monochloropropane-1,3-diol esters and 3-monochloropropane-1,2-diol esters (MCPDEs). This systematic review aimed to gain insights into the occurrence of these contaminants in different types of infant formula, to understand potential effects of the formulation and processing of infant formulas on these contaminants, as well as into possible mitigation strategies. The occurrence of dAGEs in infant formula depends on the recipes and processing conditions. Hydrolyzed protein formulations promote dAGEs formation in infant formula since peptides are more prone to glycation than intact proteins, which is reflected in high dAGEs concentration in hypoallergenic infant formula. Different carbohydrates in recipes result into different glycation extents of infant formula: maltodextrin containing formulas contained less dAGEs than those with lactose. Concerning mitigation strategies, applying ultra-high-temperature (UHT) treatment during milk processing leads to less dAGEs formation than using in-bottle sterilization. Although data are limited, evidence showed that encapsulation of raw ingredients or the use of antioxidants or enzymes in recipes is promising. The occurrence of MCPDEs and GEs in infant formula fully depends on the vegetable oils used in the recipe. High levels of these contaminants can be found when relatively high amounts of palm oils or fats are used. The mitigation of MCPDEs and GEs should therefore be performed on fats and oils before their application to infant formula recipes. Data and knowledge gaps identified in this review can be useful to guide future studies.

The vast repertoire of carbohydrate oxidases: An overview

Carbohydrates are widely abundant molecules present in a variety of forms. For their biosynthesis and modification, nature has evolved a plethora of carbohydrate-acting enzymes. Many of these enzymes are of particular interest for biotechnological applications, where they can be used as biocatalysts or biosensors. Among the enzymes catalysing conversions of carbohydrates are the carbohydrate oxidases. These oxidative enzymes belong to different structural families and use different cofactors to perform the oxidation reaction of CH-OH bonds in carbohydrates. The variety of carbohydrate oxidases available in nature reflects their specificity towards different sugars and selectivity of the oxidation site. Thanks to their properties, carbohydrate oxidases have received a lot of attention in basic and applied research, such that nowadays their role in biotechnological processes is of paramount importance. In this review we provide an overview of the available knowledge concerning the known carbohydrate oxidases. The oxidases are first classified according to their structural features. After a description on their mechanism of action, substrate acceptance and characterisation, we report on the engineering of the different carbohydrate oxidases to enhance their employment in biocatalysis and biotechnology. In the last part of the review we highlight some practical applications for which such enzymes have been exploited.

Creme de leite UHT homogeneizado: perfil sensorial e sua relação com a expectativa de consumo

Resumo Creme de leite homogeneizado UHT em embalagem longa vida é amplamente consumido no Brasil. Versões livres de lactose e com teor reduzido de gordura também estão disponíveis do mercado, seguindo necessidades especiais de consumidores e tendência de ingestão controlada de macronutrientes, respectivamente. Além de fatores como preço e disponibilidade, os consumidores selecionam os produtos com base em suas características sensoriais. Neste contexto, este estudo buscou avaliar como as características sensoriais do creme de leite UHT influenciam sua escolha e aceitação. Para isso, seis amostras comerciais de creme de leite UHT com teores de gordura variando de 17% a 20%, sendo uma sem lactose, tiveram seus perfis sensoriais determinados por meio da Análise Descritiva Quantitativa (ADQ) e foram submetidos a testes de aceitabilidade e intenção de compra. Os dados obtidos foram correlacionados por meio da análise de regressão por mínimos quadrados parciais. Análises instrumentais de cor e reologia também foram realizadas. Descritores de textura tiveram maior influência sobre a aceitabilidade das amostras, sendo que as amostras percebidas pelos julgadores treinados como mais viscosas, encorpadas e consistentes obtiveram maiores médias no teste de aceitabilidade, ao contrário daquelas consideradas mais fluidas. Não foi verificada associação do teor de gordura com as propriedades reológicas das amostras, já que as duas amostras com 17% de gordura apresentaram valores instrumentais e sensoriais de viscosidade muito diferentes entre si. Uma delas foi considerada a mais fluida, e a outra a segunda mais viscosa, consistente e encorpada pelos julgadores treinados, o que foi confirmado pela análise instrumental.

Quantitation of α-Dicarbonyls and Advanced Glycation Endproducts in Conventional and Lactose-Hydrolyzed Ultrahigh Temperature Milk during 1 Year of Storage

A comprehensive quantitative characterization of Maillard reaction products was carried out for conventional (CON) and lactose-hydrolyzed (LH) ultrahigh temperature (UHT) milk during storage at 20, 30, and 40 °C for 1 year. The accumulation of 3-deoxyglucosone (3-DG) and 3-deoxygalactosone (3-DGal) in LH-UHT milk ranged from 20-fold (at 20 °C) to 44-fold (at 40 °C) higher than that in CON-UHT milk. High temperature storage (40 °C) significantly accelerated the accumulation of 3-DG, 3-DGal, and 5-hydroxymethyl furfural but not the majority of the analyzed advanced glycation endproducts (AGEs). The concentrations of major AGEs including N-ε-carboxymethyllysine (CML), N-ε-carboxyethyllysine (CEL), methylglyoxal-hydroimidazolone isomers (MG-H1/H3), glyoxal-hydroimidazolone isomers (G-H1/H3), and G-H2 detected in CON milk during storage were in the range 12-700, 1-14, 8-45, 4-13, and 1-30 μM, respectively, while they were 30-570, 2-88, 17-150, 9-20, and 5-34 μM, respectively, in LH milk. Pyrraline, S-(carboxymethyl)cysteine (CMC), and glyoxal-lysine dimer were detected in lower levels, while MG-H2, methylglyoxal-lysine dimer, argpyrimidine, glyoxal-lysine-amide, glycolic acid-lysine-amide, and pentosidine were not detected in any of the milk samples. This work demonstrates for the first time that five of the analyzed AGEs (CML, CEL, MG-H1/H3, G-H1/H3, and G-H2) could be selected as markers for evaluation of the extent of the Maillard reaction in UHT milk. These results contribute to a better understanding of how Maillard reactions progress during storage of UHT milk and can be used to develop strategies to inhibit Maillard reactions in LH milk.

Mitigation of 3-deoxyglucosone and 5-hydroxymethylfurfural in brown fermented milk via an alternative browning process based on the hydrolysis of endogenous lactose

During the conventional production of brown fermented milk (BFM), unhealthy substances (3-deoxyglucosone (3-DG), methylglyoxal (MGO), and 5-hydroxymethylfurfural (HMF)) are generated during the Maillard browning step. Here, an alternative browning process based on the hydrolysis of endogenous lactose was established. Compared with the conventional process, 3-DG and HMF were decreased by 5.91 mg kg-1 and 0.39 mg kg-1 in the brown milk base under the alternative browning process, and thereafter, 3-DG and HMF were decreased by 54.5% and 65.0% in BFM. Investigation into the formation of 3-DG, MGO, and HMF in different chemical models showed that different sugars lead to different Maillard reaction products and browning rates, contributing to the mitigation of 3-DG and HMF. Apart from the mitigation of unhealthy Maillard compounds, hydrolyzing lactose and avoiding the addition of external glucose make the alternative browning process a theoretical and practical basis for improving the quality and safety of BFM.

The Transformative Possibilities of the Microbiota and Mycobiota for Health, Disease, Aging, and Technological Innovation

The gut microbiota is extremely important for the health of the host across its lifespan.Recent studies have elucidated connections between the gut microbiota and neurological diseaseand disorders such as depression, anxiety, Alzheimer's disease (AD), autism, and a host of otherbrain illnesses. Dysbiosis of the normal gut flora can have negative consequences for humans,especially throughout key periods during our lifespan as the gut microbes change with age in bothphenotype and number of bacterial species. Neurologic diseases, mental disorders, and euthymicstates are influenced by alterations in the metabolites produced by gut microbial milieu. Weintroduce a new concept, namely, the mycobiota and microbiota-gut-brain neuroendocrine axis anddiscuss co-metabolism with emphasis on means to influence or correct disruptions to normal gutflora throughout the lifespan from early development to old age. These changes involveinflammation and involve the permeability of barriers, such as the intestine blood barrier, the blood⁻brain barrier, and others. The mycobiota and microbiota⁻gut⁻brain axis offer new research horizonsand represents a great potential target for new therapeutics, including approaches based aroundinflammatory disruptive process, genetically engineered drug delivery systems, diseased cellculling "kill switches", phage-like therapies, medicinal chemistry, or microbial parabiosis to namea few.

Synergistic Effect of a Thermal Reaction and Vacuum Dehydration on Improving Xylose-Phenylalanine Conversion to N-(1-Deoxy-d-xylulos-1-yl)-phenylalanine during an Aqueous Maillard Reaction

The synergistic effect of a thermal reaction and vacuum dehydration on the conversion of xylose (Xyl) and phenylalanine (Phe) to a Maillard-reaction intermediate (MRI) was researched. The yield of N-(1-deoxy-α-d-xylulos-1-yl)-phenylalanine was successfully improved and increased from 13.62 to 47.23% through the method combining a thermal reaction and vacuum dehydration. A dynamic process was involved in the transformation of Xyl and Phe (Xyl-Phe) to N-substituted d-xylosamine and in the transformation of N-substituted d-xylosamine to N-(1-deoxy-α-d-xylulos-1-yl)-phenylalanine during the initial stage of dehydration; then, only the transformation of N-substituted d-xylosamine to N-(1-deoxy-α-d-xylulos-1-yl)-phenylalanine occurred during the final stage. Furthermore, the MRI was prepared under optimized conditions (90 °C and pH 7.4), and the obtained MRI was characterized and confirmed by ESI mass spectrometry and NMR.

Meat flavor generation from different composition patterns of initial Maillard stage intermediates formed in heated cysteine-xylose-glycine reaction systems

Volatile compounds formed in model reactions involving synthesized initial Maillard intermediates Gly-Amadori and [¹³C₅]-2-threityl-thiazolidine-4-carboxylic acids ([¹³C₅]-TTCA) in different molar ratios and free cysteine and glycine were investigated by solid-phase microextraction/gas chromatography-mass spectrometry and gas chromatography-olfactometry. The 1:1 ratio composition pattern provided the highest yields of all the sulfur-containing compounds, the potent meaty flavors or their ¹³C-labeled/unlabeled fractions, indicating a moderate level of glycine relative to cysteine was optimum for maximally yielding meaty flavors in complex meat-like Maillard systems containing cysteine as well as glycine. In addition, the 1:1 ratio composition led to formation of ¹³C-labeled molecules of some key meaty flavors e.g. 2-furanthiol representing over 70%, indicating TTCA/glycine reaction was better than Gly-Amadori/cysteine to yield meaty flavors. Formation pathways of twenty-nine flavors were elucidated based on the detected isotope distribution patterns. In particular, 2-methyltetrahydrothiophen-3-one, 3-thiophenethiol, 2-ethylthiophene, 2,5-dimethylthiophene, and 5-methylthiophene-2-carboxaldehyde involved a new formation pathway. Thiophene-2-carboxaldehyde and 2-methylthieno[3,2-b]thiophene showed two formation pathways.

The quantification of free Amadori compounds and amino acids allows to model the bound Maillard reaction products formation in soybean products

The quantification of protein bound Maillard reaction products (MRPs) is still a challenge in food chemistry. Protein hydrolysis is the bottleneck step: it is time consuming and the protein degradation is not always complete. In this study, the quantitation of free amino acids and Amadori products (APs) was compared to the percentage of blocked lysine by using chemometric tools. Eighty thermally treated soybean samples were analyzed by mass spectrometry to measure the concentration of free amino acids, free APs and the protein-bound markers of the Maillard reaction (furosine, Nε-(carboxymethyl)-l-lysine, Nε-(carboxyethyl)-l-lysine, total lysine). Results demonstrated that Discriminant Analysis (DA) and Correlated Component Regression (CCR) correctly estimated the percent of blocked lysine in a validation and prediction set. These findings indicate that the measure of free markers reflects the extent of protein damage in soybean samples and it suggests the possibility to obtain rapid information on the quality of the industrial processes.

Sodium sulfite pH-buffering effect for improved xylose-phenylalanine conversion to N-(1-deoxy-d-xylulos-1-yl)-phenylalanine during an aqueous Maillard reaction

The yield of the Maillard reaction intermediate (MRI), prepared in aqueous medium, is usually unsatisfactory. However, the addition of sodium sulfite could improve the conversion of xylose-phenylalanine (Xyl-Phe) to the MRI (N-(1-deoxy-d-xylulos-1-yl)-phenylalanine) in aqueous medium. Sodium sulfite (Na₂SO₃) showed a significant pH-buffering effect during the Maillard reaction, which accounted for its facilitation of the N-(1-deoxy-d-xylulos-1-yl)-phenylalanine yield. The results revealed that the pH could be maintained at a relatively high level (above 7.0) for an optimized pH-buffering effect when Na₂SO₃ (4.0%) was added before the reaction of Xyl-Phe. Thus, the conversion of Xyl-Phe to N-(1-deoxy-d-xylulos-1-yl)-phenylalanine increased from 47.23% to 74.86%. Furthermore, the addition moment of Na₂SO₃ and corresponding solution pH were crucial factors in regulating the pH-buffering effect of Na₂SO₃ on N-(1-deoxy-d-xylulos-1-yl)-phenylalanine yield. Based on the pH-buffering effect of Na₂SO₃ and maintaining the optimal pH 7.4 relatively stable, the conversion of Xyl-Phe to N-(1-deoxy-d-xylulos-1-yl)-phenylalanine was successfully improved.

Tracking the behavior of Maillard browning in lysine/arginine-sugar model systems under high hydrostatic pressure

BACKGROUND

High-pressure processing is gaining popularity in the food industry. However, its effect on the Maillard reaction during high-pressure-assisted pasteurization and sterilization is not well documented. This study aimed to investigate the effects of high hydrostatic pressure on the Maillard reaction during these processes using amino acid (lysine or arginine)-sugar (glucose or fructose) solution models.

RESULTS

High pressure retarded the intermediate and final stages of the Maillard reaction in the lysine-sugar model. For the lysine-glucose model, the degradation rate of Amadori compounds was decelerated, while acceleration was observed in the arginine-sugar model. Increased temperature not only accelerated the Maillard reaction over time but also formed fluorescent compounds with different emission wavelengths. Lysine reacted with the sugars more readily than arginine under the same conditions. In addition, it was easier for lysine to react with glucose, whereas arginine reacted more readily with fructose under high pressure.

CONCLUSION

High pressure exerts different effects on lysine-sugar and arginine-sugar models. © 2017 Society of Chemical Industry.

Control of Maillard Reactions in Foods: Strategies and Chemical Mechanisms

Maillard reactions lead to changes in food color, organoleptic properties, protein functionality, and protein digestibility. Numerous different strategies for controlling Maillard reactions in foods have been attempted during the past decades. In this paper, recent advances in strategies for controlling the Maillard reaction and subsequent downstream reaction products in food systems are critically reviewed. The underlying mechanisms at play are presented, strengths and weaknesses of each strategy are discussed, and reasonable reaction mechanisms are proposed to reinforce the evaluations. The review includes strategies involving addition of functional ingredients, such as plant polyphenols and vitamins, as well as enzymes. The resulting trapping or modification of Maillard targets, reactive intermediates, and advanced glycation endproducts (AGEs) are presented with their potential unwanted side effects. Finally, recent advances in processing for control of Maillard reactions are discussed.

Fatty acid and sterol composition of tea seed oils: Their comparison by the "FancyTiles" approach

Confusion among tea seed oils from Sect. Thea, Oleifera and Camellia in Camellia is a widespread problem in research and production. In this work, 22 fatty acids, squalene and 13 phytosterols in the three groups of tea seed oils from 16 Chinese regions were analyzed with GC-FID and GC-MS respectively. Thea oils were significantly higher in linoleic (C18:2) and palmitic (C16:0) acids but lower in oleic acid (C18:1) than Camellia and Oleifera oils while the latter two overlapped in major fatty acids. Similarly, Camellia and Oleifera oils clustered together based on the data of squalene and 12 phytosterols while Thea oils branched from them in HCA. Finally, a "FancyTiles" model was constructed to describe the fatty acids, squalene and phytosterols in a plot of semi-quantitative strategy. The results supply the basic data of the three types of tea seed oils and reveal the similarities and differences among them.

Roles of different initial Maillard intermediates and pathways in meat flavor formation for cysteine-xylose-glycine model reaction systems

To explore initial Maillard reaction pathways and mechanisms for maximal formation of meaty flavors in heated cysteine-xylose-glycine systems, model reactions with synthesized initial Maillard intermediates, Gly-Amadori, TTCA (2-threityl-thiazolidine-4-carboxylic acids) and Cys-Amadori, were investigated. Relative relativities were characterized by spectrophotometrically monitoring the development of colorless degradation intermediates and browning reaction products. Aroma compounds formed were determined by solid-phase microextraction combined with GC-MS and GC-olfactometry. Gly-Amadori showed the fastest reaction followed by Cys-Amadori then TTCA. Free glycine accelerated reaction of TTCA, whereas cysteine inhibited that of Gly-Amadori due to association forming relatively stable thiazolidines. Cys-Amadori/Gly had the highest reactivity in development of both meaty flavors and brown products. TTCA/Gly favored yielding meaty flavors, whereas Gly-Amadori/Cys favored generation of brown products. Conclusively, initial formation of TTCA and pathway involving TTCA with glycine were more applicable to efficiently produce processed-meat flavorings in a cysteine-xylose-glycine system.

Simultaneous quantification of twenty Amadori products in soy sauce using liquid chromatography-tandem mass spectrometry

A liquid chromatography-tandem mass spectrometry method using a pentafluorophenylpropyl-bonded silica column was developed to simultaneously quantify twenty Amadori products (APs), including N-(1-Deoxy-d-fructosyl-1-yl)-l-isoleucine (Fru-Ile) and N-(1-Deoxy-d-fructosyl-1-yl)-l-leucine (Fru-Leu), in soy sauce, without the need for an ion-pairing reagent or sample derivatization. The method was applied to six types of soy sauce, to determine the total AP levels and the levels of individual APs. The level of total APs widely varied between the eight samples, from 358mg/L to 24347mg/L. The concentrations of N-ε-(1-deoxy-d-fructosyl-1-yl)-l-lysine (Fru-Lys) and N-(1-deoxy-d-fructosyl-1-yl)-l-pyroglutamic acid (Fru-pGlu) were the highest among the APs and the level of Fru-pGlu was similar to that of Fru-Lys. Furthermore, fermentation periods of up to six months greatly influenced AP levels in soy sauce but the levels remained constant thereafter. Thermal treatment of soy sauce had little effect on AP levels.

The quality of low lactose milk is affected by the side proteolytic activity of the lactase used in the production process

Lactose intolerance syndrome can be efficiently tackled consuming low lactose products. Lactase is the key tool to manufacture low lactose milk (LLM): its addition during milk processing can be done "in batch", i.e. before thermal treatment, or directly "in pack" after sterilization. In this paper data on sensory properties, Maillard Reaction products (MRPs) and free amino acids formation were obtained on six commercial Italian LLMs over six months storage. They showed that the side proteolytic activity of lactase caused the release of amino acids with a significant higher MRPs and off-flavors formation in four out of five samples produced by adding the enzyme in the pack after thermal treatment. We concluded that the in pack addition of lactase after milk sterilization can have negative sensorial and nutritional consequences mainly related to the enzyme side proteolytic activity especially for prolonged storage time.