Temperature and cysteine addition effect on formation of sunflower hydrolysate Maillard reaction products and corresponding influence on sensory characteristics assessed by partial least square regression

Enhancing bread anti-staling with glucose-derived Maillard reaction products: In-depth analysis of starches, gluten networks, and moisture status

In this study, six types of amino acids (Ala, Phe, Glu, Gly, Ser, and Lys) were combined with glucose to produce Maillard reaction products (MRPs) named G-Ala, G-Phe, G-Glu, G-Gly, G-Ser and G-Lys. The effect of MRPs on bread staling was evaluated through texture and sensory analyses during storage. Furthermore, the study comprehensively analyzed the anti-staling mechanisms of MRPs by examining moisture content, starches, and gluten network changes. The results indicated that G-Gly and G-Glu delayed bread staling, with G-Gly showing the most significant effect. Compared with control, the staling rate and starch crystallinity of G-Gly bread decreased by 24.07% and 7.70%, respectively. Moreover, G-Gly increased the moisture content (3.48%), weakly bound water mobility (0.77%), and α-helix content (1.00%) of bread. Component identification and partial least squares regression further confirmed the aldonic acid, heterocyclic acids and heterocyclic ketones in MRPs inhibit water evaporation, gluten network loosening, and starch degradation, thereby delaying bread staling.

Characteristics of meat flavoring prepared using hydrolyzed plant protein mix by three different heating processes

Meat flavoring was prepared using mainly enzymatic hydrolysate of plant protein mix, VB1, cysteine, and glucose by three heating processes, including A (80 °C-140 min), B (two-stage, 80 °C-30 min/120 °C-30 min), and C (120 °C-40 min). The A-, B-, and C-heated samples exhibited the strongest fatty and weakest meaty, the strongest meaty and kokumi, and the strongest roasted and bitterness characteristics, respectively. PLS-DA for free amino acids with TAVs and that for SPME/GC-MS results with GC-O and OAVs, suggested three amino acids and eight flavor compounds contributed significantly in differentiating taste or aroma attributes of the three heated samples. Molecular weight distribution and degree of amino substitution suggested 1-5 kDa peptides contributed to kokumi taste. Overall, C- and A-heating exhibited the highest rates in Maillard reaction and lipid oxidation, respectively, while those of B heating were between these two heating processes and responsible for better flavor of meat flavoring.

Generation of volatiles from heated enzymatic hydrolysates of perilla meal with coconut oil in Maillard reaction system

Perilla meal hydrolysates (PMHs) were prepared by proteases; volatile profiles from heated mixtures of PMH and coconut oil (CO) were evaluated for their application as odor providers. Amino acids composition and degree of hydrolysis, and antioxidant activity in O/W emulsion of PMHs were assessed. PMHs were heated with different concentration of CO or with CO, xylose, and cysteine, which were non-Maillard and Maillard system, respectively. Among PMHs, double enzyme treatment using Alcalase and Flavourzyme showed higher degree of hydrolysis and antioxidant activity compared to PMHs from one type of enzymes. The presence of CO significantly increased oxygen, sulfur, and nitrogen-containing volatiles from PMHs in non-Maillard system. In case of Maillard system, PMHs with 10 % (w/w) CO contributed the formation of oxygen and nitrogen-containing volatiles such as furan and 2-methylpyrazine. PMHs might serve as an odor generator in the presence of edible oils like CO.

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.

HS-SPME-GC-MS Combined with Orthogonal Partial Least Squares Identification to Analyze the Effect of LPL on Yak Milk's Flavor under Different Storage Temperatures and Times

Flavor is a crucial parameter for assessing the sensory quality of yak milk. However, there is limited information regarding the factors influencing its taste. In this study, the effects of endogenous lipoprotein lipase (LPL) on the volatile flavor components of yak milk under storage conditions of 4 °C, 18 °C and 65 °C were analyzed via headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) combined with orthogonal partial least-squares (OPSL) discrimination, and the reasons for the changes in yak milk flavors were investigated. Combined with the difference in the changes in volatile flavor substance before and after the action of LPL, LPL was found to have a significant effect on the flavor of fresh yak milk. Fresh milk was best kept at 4 °C for 24 h and pasteurized for more than 24 h. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were employed to characterize the volatile components in yak milk under various treatment conditions. Twelve substances with significant influence on yak milk flavor were identified by measuring their VIP values. Notably, 2-nonanone, heptanal, and ethyl caprylate exhibited OAV values greater than 1, indicating their significant contribution to the flavor of yak milk. Conversely, 4-octanone and 2-heptanone displayed OAV values between 0.1 and 1, showing their important role in modifying the flavor of yak milk. These findings can serve as monitoring indicators for assessing the freshness of yak milk.

Changes in flavor and biological activities of Lentinula edodes hydrolysates after Maillard reaction

This study aimed to elucidate how the Maillard reaction (MR) affects the flavor and bioactivities of Lentinula edodes hydrolysates (LEHs). Changes in flavor were investigated using non-targeted metabolomics techniques (GC-MS and LC-MS/MS) and sensory evaluation. Simultaneously, UV absorption, fluorescence, and FT-IR spectra were used to characterize the process of MR. We also evaluated the effects of MR on the antioxidant activity, hypoglycemic activity and antimicrobial activity of LEHs in vitro. The results revealed that MR produced many volatile aldehydes and ketones and decreased the content of most amino acids, sugars and flavonoids in the LEHs while increasing the content of l-theanine and succinic acid. MRPs had a strong caramel and like-meat flavor and an obvious improvement in umami, taste continuity, and total acceptability. Furthermore, MR improved the antioxidant and antimicrobial properties of LEHs. This research establishes a theoretical foundation for MR in the deep processing of edible mushrooms.

Flavor improving effects of cysteine in xylose-glycine-fish waste protein hydrolysates (FPHs) Maillard reaction system

A promising way to utilize fish by-products is to develop hydrolysis of fish proteins with enzymes. The obtained fish protein hydrolysates (FPHs) are rich in peptides and amino acids, but bitterness and aroma defects impede further utilization of FPHs. The present study adopted Maillard reaction to improve FPHs' flavor and illustrated the role of cysteine in this system. We investigated the impact of cysteine (0, 0.25%, 0.5%, 0.75%, and 1%) on the browning intensity, free amino acids (FAAs), molecular weight distribution, structure of MRPs, volatile compounds changes and organoleptic characteristics of xylose-glycine-FPHs Maillard reaction systems. Results showed that the addition of cysteine lowered the browning degree of Maillard reaction products (MRPs) by inhibiting the cross-linking of small peptides and reducing the production of melanin. GC-MS and GC-IMS analysis indicated that cysteine inhibited the formation of furans and nitrogen-containing compounds and facilitated the formation of sulfur-containing compounds contributing to the meaty flavor. Sensory analysis revealed that 0.25-0.75% range of cysteine increased the meaty, caramel, umami, mouthfulness and salty notes, and caused a decrease in bitter taste of the MRPs as confirmed by GC-MS. A highly significant correlation between the organoleptic characteristics and physicochemical indicators of MRPs was found by Mantel test. These results elucidated the influence of cysteine on the formation of Maillard reaction products and will help improve the flavor profile of meat flavorings.

Light-Colored Maillard Peptides: Formation from Reduced Fluorescent Precursors of Browning and Enhancement of Saltiness Perception

The browning formation and taste enhancement of peptides derived from soybean, peanut, and corn were studied in the light-colored Maillard reaction compared with the deep-colored reaction. The fluorescent compounds, as the browning precursors, were accumulated during the early Maillard reaction of peptides and subsequently degraded into dark substances, which resulted in a higher browning degree of deep-colored Maillard peptides (MPs), especially for the MPs derived from corn peptide. However, the addition of l-cysteine in light-colored Maillard reaction reduced the formation of deoxyosones and short-chain reactive α-dicarbonyls, thereby weakening the generation of fluorescent compounds and inhibited the browning of MPs. Synchronously, the peptides were thermally degraded into small peptides and amino acids, which were consumed less during light-colored thermal reaction due to its shorter reaction time at high temperature compared with deep-colored ones, thus contributing to a stronger saltiness perception of light-colored MPs than deep-colored MPs. Besides, the Maillard reaction products derived from soybean and peanut peptides possessed an obvious "kokumi" taste, making them suitable for enhancing the soup flavors.

Factors influencing on the formation of dimethyl disulfide and dimethyl trisulfide in model systems

The generations of dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) in a binary or ternary model system including lipids, free amino acids and Maillard reaction products (MRPs) were studied. Various factors affecting the formation of DMDS and DMTS indicated that cysteine (Cys) and Cys MRPs could effectively decrease not only the concentrations of methionine (Met), DMDS and DMTS, but also the pH level. Rapid drops in pH limited the formation of DMDS and DMTS during Met thermal degradation. Quantitative analyses of DMDS and DMTS at acidic aqueous solutions revealed that the mixtures of MRPs derived from Cys and xylose (Xyl) had the best inhibition effect on the formation of DMDS and DMTS. The low level of DMDS and DMTS and the increasing level of furfuryl methyl sulfide and 2-thiophenecarboxaldehyde during storage indicated that MRPs derived from Cys and Xyl could effectively not only decrease the concertation of DMDS and DMTS, but also promote the development of thiophene and sulfur substituted furan. Thus, this study implied that MRPs derived from Cys/Xyl could be applied as effective substances to control the formation of DMDS and DMTS and improve the production of volatile compounds with meat-like aroma.

Effects of freeze-drying and spray-drying on the physical and chemical properties of Perinereis aibuhitensis hydrolysates: Sensory characteristics and antioxidant activities

This work was to investigate the impact of drying on the physical, chemical stability and character properties of P. aibuhitensis hydrolysate. Properties including amino acid composition, color stability, molecular weight distribution, powder morphology, etc. were compared between the freeze drying powder (FD) and spray drying powder (SD). They were fractionated with ultra filtration in antioxidant activities test. FD and SD contained amounts of amino acids and umami amino acids. SD exhibited the higher lightness and whiteness. SD had more compounds between 451 Da and 6511 Da. The surface morphology of FD was porous and flaky while SD was microsphere. SD had more volatile flavor substances and higher antioxidant activities on DPPH, hydroxyl, and superoxide radical-scavenging. In summary, results demonstrated that drying methods indeed affected the characteristics of hydrolysate, and the one prepared by spray drying method had the potential to be utilized for antioxidant food development and seafood seasoning.

Maillard reaction of food-derived peptides as a potential route to generate meat flavor compounds: A review

Plant-based meat analogues (PBMA) are promising foods to address the global imbalance between the supply and demand for meat products caused by the increasing environmental pressures and growing human population. Given that the flavor of PBMA plays a crucial role in consumer acceptance, imparting meat-like flavor is of great significance. As a natural approach to generate meat-like flavor, the Maillard reaction involving food-derived peptides could contribute to the required flavor compounds, which has promising applications in PBMA formulations. In this review, the precursors of meat-like flavor are summarized followed by a discussion of the reactions and mechanisms responsible for generation of the flavor compounds. The preparation and analysis techniques for food-derived Maillard reacted peptides (MRPs) as well as their taste and aroma properties are discussed. In addition, the MRPs as meat flavor precursors and their potential application in the formulation of PBMA are also discussed. The present review provides a fundamental scientific information useful for the production and application of MRPs as meat flavor precursors in PBMA.

Dependence and Conversion Mechanism for Selective Preparation of a Xylose-Diglycine Amadori Compound and a Cross-linking Product in an Aqueous Maillard Reaction

The structure of the prepared Amadori rearrangement product of xylose-glycylglycine (XGG-ARP) and a cross-linking product (XGG-CP) was first characterized by liquid chromatography-mass spectrometry (LC-MS)/MS and NMR analysis, respectively. The dependences were then studied for the formation of XGG-ARP and XGG-CP in an aqueous Maillard reaction of a xylose-glycylglycine model system. The influence factors were the reaction temperature, pH, molar ratio of reactants, and the reaction time. It was found that XGG-ARP would acquire the highest yield of 73.8% when the thermal reaction was carried out at 70 °C and pH 8.0 for 10 min. A higher temperature and a lower pH might enhance the yield of the formation of XGG-CP. Combining the low-temperature dehydration reaction with the high-temperature aqueous-phase Maillard reaction increased the XGG-CP yield to 43.54%. The efficient and selective preparation of XGG-ARP and XGG-CP was controllable through the adjustment of reaction conditions. Moreover, the pathway of XGG-CP formation from XGG-ARP and Gly-Gly by the aldimine condensation reaction was also proposed. The high stability of an XGG-CP molecule enhanced by its p-π-p conjugated structure inhibited the occurrence of the Amadori rearrangement and led to a non-keto structure, blocking the further Maillard reaction of XGG-CP.

Recent insights in flavor-enhancers: Definition, mechanism of action, taste-enhancing ingredients, analytical techniques and the potential of utilization

The consumers' demand for clean-label food products, lead to the replacement of conventional additives and redesign of the production methods in order to adopt green processes. Many researchers have focused on the identification and isolation of naturally occurring taste and flavor enhancers. The term "taste enhancer" and "flavor enhancer" refer to umami and kokumi components, respectively, and their utilization requires the study of their mechanism of action and the identification of their natural sources. Plants, fungi and dairy products can provide high amounts of naturally occurring taste and flavor enhancers. Thermal or enzymatic treatments of the raw materials intensify taste and flavor properties. Their utilization as taste and flavor enhancers relies on their identification and isolation. All the above-mentioned issues are discussed in this review, from the scope of listing the newest trends and up-to-date technological developments. Additionally, the appropriate sensory analysis protocols of the naturally occurring taste-active components are presented. Moreover, future trends in using such ingredients by the food industry can motivate researchers to study new means for clean-label food production and provide further knowledge to the food industry, in order to respond to consumers' demands.

Volatile Profiling of Pleurotus eryngii and Pleurotus ostreatus Mushrooms Cultivated on Agricultural and Agro-Industrial By-Products

The influence of genetic (species, strain) and environmental (substrate) factors on the volatile profiles of eight strains of Pleurotus eryngii and P. ostreatus mushrooms cultivated on wheat straw or substrates enriched with winery or olive oil by products was investigated by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS). Selected samples were additionally roasted. More than 50 compounds were determined in fresh mushroom samples, with P. ostreatus presenting higher concentrations but a lower number of volatile compounds compared to P. eryngii. Roasting resulted in partial elimination of volatiles and the formation of pyrazines, Strecker aldehydes and sulfur compounds. Principal component analysis on the data obtained succeeded to discriminate among raw and cooked mushrooms as well as among Pleurotus species and strains, but not among different cultivation substrates. Ketones, alcohols and toluene were mainly responsible for discriminating among P. ostreatus strains while aldehydes and fatty acid methyl esters contributed more at separating P. eryngii strains.

Effects of roasting level on physicochemical, sensory, and volatile profiles of soybeans using electronic nose and HS-SPME-GC-MS

We applied oven-roasting on soybean in order to investigate their physicochemical, sensory, and volatile profiles using electronic nose and HS-SPME-GC-MS. Results revealed a temperature dependent kinetic on the physicochemical index except fat content. Roasting at 200 °C for 20 min decreased the protein dispersibility index about 38%; while, lipoxygenase and peroxidase were entirely inactivated. The primary heat sensitive amino acids were methionine, arginine, and cysteine. Electronic nose showed certain capacity to discriminate varying roasted soybeans. Out of 41 volatile compounds identified in soybean headspace, 2,5-dimethylpyrazine showed the highest abundance of 411.18 μg/Kg. Regression model suggested the association of hexanal and aliphatic alcohols with beany flavor, while pyrazines, heterocycles, and furanoids showed a positive correlation with roasted flavor. The selected flavor markers can be used to predict the development of flavor in roasted soybeans. Our study emphasized the effect of roasting level on nutritive value and flavor profiles of soybeans.

Analysis of taste characteristics and identification of key chemical components of fifteen Chinese yellow tea samples

In order to explore the taste characteristics and molecular sensory basis of Chinese yellow tea, in this study, quantitative descriptive analysis (QDA) and partial least squares regression (PLSR) were used to analyze the sensory characteristics and chemical components of 15 yellow tea samples from different regions of China. The results showed that: 11 sensory descriptors and their definitions were obtained by QDA, namely, sweet, umami, bitter, sour, astringent, sweet after taste, mellow, neutral, after-taste, thick and tainted taste. The results of variance indicated that there were significant variation in taste sub-attributes of different samples (p <0.05). Principal component analysis indicated that there was a positive correlation between bitter and astringent, between sweet, umami and sour, and between mellow, thick, after-taste and neutral. All yellow tea samples were divided into four categories according to cluster analysis. The results of PLSR showed that there were 22 chemical components that had an important contribution to the taste characteristics of yellow tea, and the chemical components that had an important influence on each taste component were obtained. The identification of key contribution components of taste characteristics in yellow teas will provide a theoretical basis for further research on the directional adjustment and control of tea taste quality.

Aromatic effects of immobilized enzymatic oxidation of chicken fat on flaxseed (Linum usitatissimum L.) derived Maillard reaction products

To control the oxidation in chicken fat by immobilized lipoxygenase (LOX), Maillard reaction products (MRPs) with chicken flavor were prepared and analyzed for flavor mechanism. >50% activity of immobilized LOX was retained after repeated use for five times or five weeks. The oxidized chicken fats were prepared by thermal, free LOX, and immobilized LOX treatments. After addition of chicken fats, Maillard reaction produced more aliphatic aldehydes and alcohols (126.0-839.5 ng/g and 493.5-2332.4 ng/g, respectively) which resulted in noticeable enhanced reaction, but the content of sulfur compounds such as thiols and thiophenes decreased significantly (870.8-1233.9 ng/g and 1125.0-2880.3 ng/g, respectively), and the structure of sulfur compounds could easily form alkyl side chains. However, there was no significant difference in sensory and flavors between oxidized chicken after treatments, which may be related to oxidized degree. The mechanism was proposed or aromatic effects of oxidized chicken fat on flaxseed derived MRPs.

Potential effects of rapeseed peptide Maillard reaction products on aging-related disorder attenuation and gut microbiota modulation in d-galactose induced aging mice

As a good flavor enhancer, rapeseed peptide Maillard reaction products (MRPs) were developed, and the effects of MRPs on d-galactose induced aging Kunming mice were investigated for 6 weeks with low (200 mg kg-1 day-1), medium (400 mg kg-1 day-1) and high (800 mg kg-1 day-1) doses. Compared with the natural aging group and d-galactose induced aging mice, the mice with MRP administration showed increases in body weight gain, food intake, organ indexes, feces color and urine fluorescence intensity. MRP intake significantly decreased the MDA content and elevated the activities of CAT, SOD and GSH-Px, and T-AOC in the serum and tissues of the liver, kidney and brain. Additionally, AChE activity was decreased in the brain, while Na+-K+ ATPase and Ca2+-Mg2+ ATPase activity increased in a dose-dependent manner, and decreasing levels of IL-1β, IL-6 and TNF-α were observed in the liver and kidney. Histopathological analysis suggested an attenuation of inflammatory cell infiltration in the liver and kidney without cell necrosis. High-throughput sequencing results revealed that the ratio of Firmicutes to Bacteroidetes increased in MRP groups, and the pathogenic bacteria were significantly inhibited, while some beneficial bacteria were significantly increased in the intestine. Overall, our results indicated that MRP consumption might have potential beneficial effects on postponing the aging process via reducing the oxidative stress and gut microflora modulation.

Cysteine's effects on chlorogenic acid quinone induced greening and browning: Mechanism and effect on antioxidant reducing capacity

Formation of green trihydroxy benzacridine (TBA) derivatives when chlorogenic acid (CGA) quinones and amino acids react can be unappealing for some consumers. Cysteine was studied as an anti-greening strategy, given that cysteine-CGA conjugates are colorless. Buffered 2.55 mM CGA: 5.09 mM lysine: (0-5.09) mM cysteine solutions at pH 8 and 9 were prepared and incubated for a maximum of 48 h at 22 C. Color intensity and conjugate formation was monitored spectrophotometrically, and by HPLC and LC-MS respectively, while antioxidant capacity was measured by Folin-Ciolcateau and Trolox equivalent antioxidant capacity assays. Green TBA formation was promoted at higher pH and inhibited as cysteine concentration increased. Concentration-dependent cysteine inhibition of CGA-lysine greening was attributed to redox diphenol regeneration and formation of cysteinyl-CGA conjugates, which also contributed to antioxidant capacity. pH had a greater effect on antioxidant capacity than added cysteine. Results suggested a potential anti-greening approach for alkaline CGA quinone-amine greening.

Maillard reaction derived from oil-tea camellia seed through roasting

BACKGROUND

The Maillard reaction products (MRPs) formed after roasting of oil-tea camellia seeds (camellia seeds) were investigated. Camellia seeds are inevitably heated during processing, but the effect of heating or roasting on the physicochemical properties of camellia seed or oil-tea camellia seed oil (camellia oil) has been seldom studied, especially with respect to the Maillard reaction.

RESULTS

Changes in reducing sugars, free amino acids, pH, color, browning intensity and MRP (furosine, glyoxal, methylglyoxal, 5-hydroxymethylfurfural and furural) concentrations were examined in camellia seeds during roasting at 120-160 °C for 20-120 min. Results showed that roasting leads first to a decrease and then to a considerable increase in free amino groups and, at the same time, to a reduction in moisture content and decrease in pH. The sucrose content of the seeds decreased, while that of glucose and fructose increased reciprocally during roasting. On the other hand, the observed changes concerning glyoxal were negligible. Furthermore, 5-hydroxymethylfurfural and furfural have been found at the end of the roasting process, with maximum values of 572.26 ± 1.91 mg kg^-1 dry wt and 0.46 ± 0.003 mg kg^-1 dry wt, at 160 °C for 120 min, respectively.

CONCLUSION

This investigation provides the initial groundwork necessary for the development and implementation of green and efficient technology that could be applied to obtain high-quality camellia oil. Future research is necessary to assess antioxidant capacity, quality and safety of oil after thermal processing of camellia seeds. © 2019 Society of Chemical Industry.

Effect of sodium chloride concentration on off-flavor removal correlated to glucosinolate degradation and red radish anthocyanin stability

Anthocyanin-rich concentrates from different red radish can be used as natural food colorants. However, the development of off-flavor during extraction has been major challenge in processing industries. This work aimed to evaluate the effect of sodium chloride (NaCl) concentration in phosphoric acidified medium pH 2.5 on removal of off-flavor from red radish anthocyanin. The effect of NaCl concentration on anthocyanin properties was also evaluated. Results showed that the total glucosinolate was highly degraded at high NaCl concentration (< 500 mM) compared with control, leading to higher off-flavor development. Additionally, the glucosinolate degradation was positively and significantly correlated to isothiocyanate, while was negatively and significantly correlated with dimethyl di-, trisulfide, cedrol, triacetin, 6-methyl-5-hepten-2-one. Moreover, total monomeric and color properties of extracted anthocyanins were degraded at high NaCl concentration (< 500 mM) compared with control. The tentative anthocyanin identification by UPLC-TQ-MS showed 12 glycosylated anthocyanins substituted at C3 and C5 in tested anthocyanin extracts. In conclusion, higher NaCl concentration (< 500 mM) could not be useful for red radish off-flavor removal and anthocyanin properties.

Heating and cysteine effect on physicochemical and flavor properties of soybean peptide Maillard reaction products

Maillard reaction products (MRPs) were obtained by using the xylose and soybean peptide system through a 2 h heating at pH of 7.6. Cysteine addition and thermal treatment at 80, 100, 120 and 140 °C were investigated via E-nose and E-tongue, free amino acids (FAA) and GC-MS analyses of MRPs. Afterwards, the combined effects were performed using the partial least square regression (PLSR). Results suggested that MRPs without cysteine addition (XSs) had stronger browning intensity, and the cysteine would be beneficial to the pH reduction with heating temperature increasing. PLSR analysis revealed that MRPs with cysteine addition heated at 140 °C (XSC-140) showed the lowest bitterness, and XS-100 had the highest umami and saltiness. Both bitter and umami FAA increased with the addition of cysteine, and more furans and nitrogen-containing compounds formed in the XSs brought caramel-like flavor, while XSCs exhibited meat-like flavor attributed to sulphides generation.

Discovery of Amadori-Type Conjugates in a Peptide Maillard Reaction and Their Corresponding Influence on the Formation of Pyrazines

Knowledge of the role of peptides in the Maillard reaction is rather limited. In this study, peptide Maillard reaction model systems were established. Volatile and nonvolatile MRPs (Maillard reaction products) were investigated by GC-O-MS and LC-MS. Carbohydrate module labeling (CAMOLA) experiments were performed to elucidate the carbon skeleton of these compounds. Results showed that the peptide reaction system generated more pyrazines than the free amino acid group. Several new Amadori-type conjugates were identified as novel Maillard reaction products that could greatly influence the formation of pyrazines. Our work suggested anew mechanism involving these Amadori-type conjugates and subsequent investigation revealed that the conjugates could be important intermediate products in the reaction between dicarbonyl and dipeptide. Our findings demonstrate anew pyrazine generation mechanism in the dipeptide Maillard reaction.

PRACTICAL APPLICATION

We found that a dipeptide Maillard reaction system generated more pyrazines than a reaction system composed of free amino acids. New cross-linked peptide-sugar compounds were identified and found to impact the formation of pyrazines. The results of this study may help in the preparation of thermal reaction flavors using enzymatically hydrolyzed vegetable/animal proteins, which contain a considerable amount of peptides, as one of the major reactants.

Antioxidant activity and sensory characteristics of Maillard reaction products derived from different peptide fractions of soybean meal hydrolysate

Four peptide fractions PF1 (>5;kDa), PF2 (3-5;kDa), PF3 (1-3;kDa), PF4 (<1;kDa) were isolated from soybean hydrolysate using the ultrafiltration method. Then, d-xylose and l-cysteine were reacted with specific peptide solution at 120;°C for 2;h, and the molecular weight distribution (MWD), pH, colour, browning intensity, DPPH radical-scavenging activity, free amino acids and sensory characteristics of corresponding Maillard reaction products (MRPF1, MRPF2, MRPF3 and MRPF4) were evaluated, respectively. Peptides with low molecular weight showed higher contribution to the changes of pH, colour and browning intensity during Maillard reaction. The DPPH radical-scavenging activity of PF4 was significantly improved after Maillard reaction. Aroma volatiles and PLSR analysis suggested MRPF3 had the best sensory characteristics with higher contents of umami amino acids and lower of bitter amino acids, therefore it could be deduced that the umami and meaty characteristics were correlated with the peptides of 1-3;kDa.

Effect of Temperature on Flavor Compounds and Sensory Characteristics of Maillard Reaction Products Derived from Mushroom Hydrolysate

Maillard reaction products (MRPs) were prepared from mushroom hydrolysate (MH) by heating with d-xylose and l-cysteine at various temperatures (100 °C-140 °C) for 2 h at a pH of 7.4. The sensory characteristics of MH and MRPs were evaluated by panelists and volatile compounds were analyzed by GC/MS. Additionally, partial least squares regression (PLSR) was performed to analyze the correlation between quantitative sensory characteristics and GC/MS data. GC/MS results revealed that higher reaction temperature resulted in more nitrogen and sulfur containing compounds in MRPs while alcohols, ketones and aldehydes were the major flavor compounds obtained in MH. PLSR results showed that 3-phenylfuran and 2-octylfuran were the compounds responsible for the caramel-like flavor; 1-octen-3-ol, (E)-2-octen-1-ol and geranyl acetone were significantly and positively correlated to mushroom-like flavor, whereas, 2-thiophene-carboxaldehyde, 2,5-thiophenedicarboxaldehyde and 3-methylbutanal positively affected MRPs meat-like attribute. Overall, 125 °C was identified as the optimal temperature for preparing MRPs with abundant volatile compounds and favorable sensory characteristics; the concentration of free amino acids and 5'-GMP, which are associated with the umami taste, in MRPs derived under 125 °C were 3 to 4 times higher than those in MH.

Characterization of the key odorants of fennel essential oils of different regions using GC-MS and GC-O combined with partial least squares regression

The key odorants and the aroma profile of six fennel essential oils from different regions were investigated by using gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS) and sensory evaluation. A total of 30 volatile compounds were determined by GC-O with aroma extract dilution analysis (AEDA) and the odor activity values (OAV) of them were calculated. Among these compounds, α-pinene, α-phellandrene, limonene, α-cubebene, β-caryophyllene, estragole, α-humulene, trans-anethole, δ-cadinene and p-anisaldehyde contributed greatly to the aroma of fennel essential oil due to their high flavor dilution (FD) factors and high OAVs. The aroma of fennel essential oils was described by 7 sensory terms as spicy, woody, grassy, floral, musty, sweet and green, and was correlated to the key odorants by partial least squares regression (PLSR). It was showed that spicy, woody, grassy, musty and green attributes were covaried well with aroma compounds. In addition, hierarchical cluster analysis (HCA) was used to find out the similarities among different samples and the result indicated that three main groups were identified.

Sensory Characteristics of Maillard Reaction Products Obtained from Sunflower Protein Hydrolysates and Different Sugar Types

The effect of different sugar types on the sensory characteristics of Maillard reaction products (MRPs) obtained from sunflower protein hydrolysates was evaluated. MRPs were prepared at 120 °C for a time of 2 h and a pH of 7.4. Results showed that the browning intensity, colour development and free and total amino acids of MRPs were highly affected by the sugar types. Peptide-xylose-cysteine (PXC) were more dark-brown in colour with lower free and total amino acid (FAA and TAA) content compared to the other MRPs. However, PXC showed great mouthfulness and continuity taste with stronger meat-like flavour and umami taste compared to MRPs. MRPs from hexose except PGaC, showed acceptable mouthfulness and continuity taste while PLC and PMC and PGaC showed higher caramel-like flavour and bitter taste. Furthermore, pentose sugars (xylose) were the great precursor of sulphur-containing compounds. It could be concluded that sunflower peptides, xylose, cysteine model system could be a good precursor of flavour enhancers.

Contribution of crosslinking products in the flavour enhancer processing: the new concept of Maillard peptide in sensory characteristics of Maillard reaction systems

In this study, the flavour-enhancing properties of the Maillard reaction products (MRPs) for different systems consisted of different peptides (sunflower, SFP; corn, CP and soyabean SP) with, xylose and cysteine were investigated. Maillard systems from peptides of sunflower, corn and soyabean with xylose and cysteine were designated as PXC, MCP and MSP, respectively. The Maillard systems were prepared at pH of 7.4 using temperature of 120C for 2 h. Results showed that all systems were significantly different in all sensory attributes. The highest scores for mouthfulness and continuity were observed for MCP with the lowest peptides distribution between 1000 and 5000 Da, known as Maillard peptide. This revealed that the MCP with the lowest Maillard peptide content had the strongest "Kokumi" effect compared to the other MRPsand demonstrated that "kokumi effect" of MRPs was contributed by not only the "Maillard peptide" defined by the molecular weight (1000-5000 Da). Results on sensory evaluation after fractionation of PXC followed by enzymatic hydrolysis showed no significant differences between PXC, P-PXC and their hydrolysates. This observation therefore confirmed that the presence of other contributors attributed to the "Kokumi" effect rather than the Maillard peptide. It can be deduced that the unhydrolyzed crosslinking products might have contributed to the "Kokumi" effect of MRPs. The structures of four probable crosslinking compounds were proposed and the findings have provided new insights in the sensory characteristics of xylose, cysteine and sunflower peptide MRPs.

Improving red radish anthocyanin yield and off flavor removal by acidified aqueous organic based medium

In view of the high content of the highly stable anthocyanin in red radish roots, the plant is considered as a potent source of natural anthocyanins.

Characterization of odor-active compounds of various Chrysanthemum essential oils by gas chromatography-olfactometry, gas chromatography-mass spectrometry and their correlation with sensory attributes

Volatiles of five kinds of Chrysanthemum essential oils with different manufactures were characterized by descriptive sensory analysis, gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS) and statistics analysis. Six sensory attributes (floral, woody, grassy, fruity, sour and minty) were selected to assess Chrysanthemum essential oils. A total of 38 volatile compounds were detected and quantified using standard substances by GC-O and GC-MS. Terpenes constituted the largest chemical group among the volatiles of the essential oils. Then partial least squares regression (PLSR) was used to elucidate the relationship between sensory attributes and aroma compounds. The result showed that α-pinene, β-thujene, α-terpinolen, β-cubebene, caryophyllene, (Z)β-farnesene, (-)-spathulenol, linalool, camphor, camphene, 4-terpineol, Z-citral and 4-isopropyltoluene were typical aroma compounds covaried with characteristic aroma of Chrysanthemum essential oils.