Changes in gaseous concentration of alkylpyrazine analogs affect mouse avoidance behavior.

We developed a rapid and accurate method for quantifying gaseous phase odorants using headspace solid-phase microextraction (HS-SPME) in conjunction with GC-MS and used our system to quantify alkylpyrazine analogs in the Y-maze. Rapid extraction of volatile compounds in the vapor phase achieved accurate quantitative analysis of gaseous alkylpyrazine analogs at several locations in the Y-maze. We also used a series of three SPME fibers to quantify changes in the concentration over time. We conducted a behavioral test of mice in response to these alkylpyrazines and identified a positive relationship between the rate of increase in gaseous concentration and the avoidance rate induced. Our results demonstrate that the Y-maze is a simple but reliable apparatus for behavioral studies of olfaction. The HS-SPME fast extraction method can quantify how gaseous concentrations of alkylpyrazines change over time, and the time-dependent increase of alkylpyrazine concentration is correlated with induction of aversive behavior in mice.

Application of integrative physiological approach to evaluate human physiological responses to the inhalation of essential oils of Japanese citrus fruits iyokan (Citrus iyo) and yuzu (Citrus junos).

This study investigated the effects of essential oil odors from Japanese citrus fruits, iyokan (Citrus iyo) and yuzu (Citrus junos), on human psychology and both the autonomic and central nervous systems. The inhalation of both essential oils significantly increased miosis rate and fingertip temperature and could induce parasympathetic dominance by suppressing sympathetic nerve activity. Oxyhemoglobin concentration in the prefrontal cortex increased after the inhalation of yuzu essential oil and decreased after the inhalation of iyokan essential oil. Subjectively, the inhalation of both essential oils reduced the feelings of fatigue and improved the feelings of refreshment, suggesting that the effect of autonomic nervous activity might involve in these psychological changes directly. Moreover, we observed that task performance improved after inhaling yuzu essential oil, which may be due to the increase in oxyhemoglobin concentration in the prefrontal cortex.

2,3-Dimethylpyrazine (3DP) and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) generated by the Maillard reaction in foods affect autonomic nervous activity and central nervous activity in human.

This study investigated the effect of the odors generated by the glycine/glucose Maillard reaction and the potent odorants 2,3-dimethylpyrazine (3DP) and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) on the human mood and integrative physiological activity. The score of certain subjective moods, especially anger-hostility, and tension-anxiety were decreased significantly after inhalation of the Maillard reaction sample and DMHF, and fatigue-inertia mood was also significantly decreased by DMHF, suggesting a sedative effect of these odors on mood, while 3DP had no effect. Miosis rate and fingertip temperature increased significantly following inhalation of the odor from the Maillard reaction sample and both potent odorants, suggesting that the parasympathetic nervous system dominates through suppression of the sympathetic activity. The physiological relaxing effect of these odors was also confirmed by decreased flicker frequency value and decreased oxyhemoglobin in the prefrontal cortex.

Odors generated from the Maillard reaction affect autonomic nervous activity and decrease blood pressure through the olfactory system.

BACKGROUND: Systolic blood pressure (SBP) of rats decreases significantly following exposure to the odor generated from the Maillard reaction of protein digests with xylose. This study identified active odorants that affect blood pressure and demonstrated the mechanism of action. RESULTS: Among the four potent odorants that contribute most to the odor of the Maillard reaction sample, 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) and 5-methyl-2-pyrazinemethanol (MPM) decreased SBP significantly. The earliest decrease in blood pressure was observed 5 min after exposure to DMHF. Application of zinc sulfate to the nasal cavity eliminated the effect. Furthermore, gastric vagal (parasympathetic) nerve activity was elevated and renal sympathetic nerve activity was lowered after exposure to DMHF. CONCLUSION: It is indicated that DMHF affects blood pressure through the olfactory system, and the mechanism for the effect of DMHF on blood pressure involves the autonomic nervous system. © 2017 Society of Chemical Industry.

Comparison of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, a volatile odor compound generated by the Maillard reaction, in cooked meat of various animal species and parts.

2,5-Dimethyl-4-hydroxy-3(2H)-furanone (DMHF), a compound having a sweet caramel-like odor, is one of the major compounds generated by the Maillard reaction. DMHF could affect the palatability of cooked and processed foods such as meat, while its inhalation induces several physiological functions. However, basic findings of DMHF generation in meat remain unclear. In this study, we compared the amount of DMHF in cooked meat of various animal meat (Japanese black cattle beef, Australian beef, pork, and chicken) and parts (round, loin, thigh, and breast). Meat samples were heated at 230°C, and then the amount of DMHF was measured using the solvent extraction methods. Moreover, the substrates (total free amino acid and glucose) used for the Maillard reaction were also measured to elucidate the relation between DMHF generation and nutrients in meat. DMHF was detected in all cooked meat samples, suggesting that DMHF is generated in meat regardless of animal species and parts. A significant positive correlation was observed between the DMHF generation and glucose content in the round and thigh parts. Our results suggest that DMHF generation during meat cooking would be regulated by the glucose content.

Repeated exposure to kairomone-containing coffee odor improves abnormal olfactory behaviors in heterozygous oxytocin receptor knock-in mice.

The oxytocin receptor (OXTR) knockout mouse is a model of autism spectrum disorder, characterized by abnormalities in social and olfactory behaviors and learning. Previously, we demonstrated that OXTR plays a crucial role in regulating aversive olfactory behavior to butyric acid odor. In this study, we attempted to determine whether coffee aroma affects the abnormal olfactory behavior of OXTR-Venus knock-in heterozygous mice [heterozygous OXTR (±) mice] using a set of behavioral and molecular experiments. Four-week repeated exposures of heterozygous OXTR (±) mice to coffee odor, containing three kairomone alkylpyrazines, rescued the abnormal olfactory behaviors compared with non-exposed wild-type or heterozygous OXTR (±) mice. Increased Oxtr mRNA expression in the olfactory bulb and amygdala coincided with the rescue of abnormal olfactory behaviors. In addition, despite containing the kairomone compounds, both the wild-type and heterozygous OXTR (±) mice exhibited a preference for the coffee odor and exhibited no stress-like increase in the corticotropin-releasing hormone, instead of a kairomone-associated avoidance response. The repeated exposures to the coffee odor did not change oxytocin and estrogen synthetase/receptors as a regulator of the gonadotropic hormone. These data suggest that the rescue of abnormal olfactory behaviors in heterozygous OXTR (±) mice is due to the coffee odor exposure-induced OXTR expression.

Inhalation of odors containing DMHF generated by the Maillard reaction affects physiological parameters in rats.

The effects of odors generated by the Maillard reaction from amino acids and reducing sugars on physiological parameters (blood pressure, heart rate, and oxidative stress levels) in Wistar rats were investigated in the present study. The Maillard reaction samples were obtained from glycine, arginine, or lysine of 1.0 mol/L and glucose of 1.0 mol/L with heat treatment. The odor-active compounds in the Maillard reaction samples were identified using the aroma extract dilution analysis. Among the odor-active compounds identified, 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF, FURANEOL and strawberry furanone) had the highest odor activity and its concentration was affected by amino acid types. The Maillard reaction odors generated from glycine or arginine significantly decreased systolic blood pressure and heart rate in rats when inhaled. These physiological effects were associated with DMHF. Furthermore, oxidative stress marker levels in rat plasma were decreased by the inhalation of DMHF. The inhalation of DMHF appears to at least partly affect physiological parameters by decreasing oxidative stress.

DMHF (2,5-dimethyl-4-hydroxy-3(2H)-furanone), a volatile food component generated by the Maillard reaction, promotes appetite and changes gene expression in the rat brain through inhalation.

Inhalation of odors can affect physiological parameter and change gene expression-related specific function. 2,5-Dimethyl-4-hydroxy-3(2H)-furanone (DMHF) is one of the major odor compounds generated by the Maillard reaction. We previously reported that the inhalation of DMHF decreased systolic blood pressure via the autonomic nervous system in rats. The autonomic nervous system is also closely related to appetite regulation. The present study investigated the effects of DMHF on dietary intake and gene expression. The inhalation of DMHF increased the dietary intake of rats during the feeding period. However, body weight did not change after 6 weeks feeding. A DNA microarray analysis showed that DMHF altered gene expression associated with feeding behavior and neurotransmission in the rat brain. DMHF inhalation promotes appetite and changes gene expression in rats. Furthermore, phenotypic changes may regulate neurotransmission and appetite at the mRNA level in addition to controlling the autonomic nervous system. PRACTICAL APPLICATION: DMHF is an important flavor component in the food industry. In this study, we first observed that the inhalation of DMHF promotes appetite. This finding is directly connected with the industrial application.

Investigation of potent odorants generated during the production of whey protein hydrolysates.

Whey protein hydrolysates (WPH) were prepared from whey protein concentrate (WPC) by partial or extensive hydrolysis. WPC and two WPH types were characterized by a descriptive sensory analysis. WPC exhibited a "milky", "sweet", and "mild milk fat" odor, whereas extensively hydrolyzed whey protein (E-WPH) demonstrated "cheese-like", "acrid odor", and "sour" olfactory characteristics. In E-WPH, 3-(methylthio)-propanal, phenylacetaldehyde, and 3-methylbutanoic acid were specifically detected with high flavor dilution factors upon aroma extract dilution analysis. These odor-active compounds likely contributed to the olfactory characteristics of E-WPH, and their concentration increased together with that of their respective putative precursors: free methionine, phenylalanine, and leucine.

Effects of odor generated from the glycine/glucose Maillard reaction on human mood and brainwaves.

Effects of the odor generated from the glycine/glucose Maillard reaction on human mood and brainwaves were investigated in the present study. Equimolar solutions of glucose and glycine were adjusted to pH 7 and pH 9 and heated at 90 °C for 30 min. The odor generated from the glycine/glucose Maillard reaction significantly decreased negative moods. Its effects on brainwaves differed according to pH; alpha brainwave distribution was increased after inhalation of the odor generated at pH 7, whereas it was decreased by the odor generated at pH 9. The effects on mood and brainwaves were also measured after inhalation of model solutions, which comprised of potent odorants determined by aroma extract dilution analysis (AEDA), and the results were similar to those obtained with the Maillard reaction samples. Therefore, odors constructed by potent odorants could influence human mood and brainwaves. Among all potent odorants, 2,3-dimethylpyrazine and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) were identified as the strongest, and high pH values resulted in higher yields of these odorants. Furthermore, DMHF was identified as the putative agent responsible for the decrease in alpha brainwave distribution after smelling the pH-9 Maillard reaction sample since higher concentrations of DMHF resulted in a similar effect.

Antioxidant activity of fermented meat sauce and isolation of an associated antioxidant peptide.

The present study was carried out to investigate the radical scavenging and antioxidant activities of fermented meat sauce (FMS) against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the hydroxyl radical (OH-radical), as well as to isolate substances in FMS related to its antioxidant activity. FMS was prepared by mixing ground pork, koji (rice fermented with koji mold such as Aspergillus), and salt, and fermenting for 24weeks. High antioxidant activities against the DPPH radical and the OH-radical in FMS were observed as about 0.55µmolTroloxeq./ml and 61.2%, respectively. DPPH radical scavenging activities were related to time-dependent changes in proteolysis and antioxidant peptides could be generated in FMS by proteolysis. Liquid chromatography-mass spectrometry analysis detected a substance of molecular weight 406.26g/mol from the purified peptide fraction, which showed an extremely high antioxidant activity against the OH-radical that was greater than 90%. This substance was anticipated to be the tripeptide Gln-Tyr-Pro.

Heme induces DNA damage and hyperproliferation of colonic epithelial cells via hydrogen peroxide produced by heme oxygenase: a possible mechanism of heme-induced colon cancer.

Epidemiological and animal model studies have suggested that high intake of heme, present in red meat, is associated with an increased risk of colon cancer. However, the mechanisms underlying this association are not clear. This study aimed to investigate whether heme induces DNA damage and cell proliferation of colonic epithelial cells via hydrogen peroxide produced by heme oxygenase (HO). We examined the effects of zinc protoporphyrin (ZnPP; a HO inhibitor) and catalase on DNA damage, cell proliferation, and IL-8 production induced by the addition of hemin (1-10 microM) to human colonic epithelial Caco-2 cells. DNA damage was determined with a comet assay, and cell proliferation was evaluated with 5-bromo-2'-deoxyuridine incorporation assay. Both ZnPP and exogenous catalase inhibited the hemin-induced DNA damage and cell hyperproliferation dose-dependently. IL-8 messenger RNA expression and IL-8 production in the epithelial cells increased following the hemin treatment, but the production was inhibited by ZnPP and catalase. These results indicate that hemin has genotoxic and hyperproliferative effects on Caco-2 cells by HO and hydrogen peroxide. The mechanism might explain why a high intake of heme is associated with increased risk of colon cancer.

Quantification and odor contribution of 2-furanmethanethiol in different types of fermented soybean paste miso.

2-Furanmethanethiol, a compound contained in many kinds of food, was identified for the first time in five types of miso fermented soybean paste (red salty rice miso, thin-colored salty rice miso, weak salty rice miso, barley miso, and soy miso) by specific extraction of volatile thiols using p-hydroxymercuribenzoate. In the triangle test with red salty rice miso, which included a higher concentration of 2-furanmethanethiol, and thin-colored salty rice miso, which included a lower concentration of 2-furanmethanethiol, it was shown that the aroma of thin-colored salty rice miso was similar to that of red salty rice miso by adding 2-furanmethanethiol into thin-colored salty rice miso. In addition, a quantitative descriptive analysis (QDA) clearly shows that 2-furanmethanethiol contributed to the intensity of three odor qualities "thick, complex", "sweet", and "pleasant aroma like coffee beans" in six odor qualities and was a very important component of miso aroma.

Effects of the amino-carbonyl reaction of ribose and glycine on the formation of the 2(or 5)-ethyl-5(or 2)-methyl-4-hydroxy-3(2H)-furanone aroma component specific to miso by halo-tolerant yeast.

The formation of HEMF[2(or 5)-ethyl-5(or 2)-methyl-4-hydroxy-3(2H)-furanone], the aroma component specific to miso and soy sauce, was promoted by cultivating the halo-tolerant yeast, Zygosaccharomyces rouxii, in a medium including the amino-carbonyl reaction products based on ribose and glycine. The glucose concentration in the medium influenced the HEMF formation by Z. rouxii.

The formation mechanism by yeast of 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone in Miso.

The mechanism of the formation of 4-hydroxy-2(or 5)-ethyl-5-(or 2)-methyl-3(2H)-furanone (HEMF) with yeast under caltivation in a medium containing amino-carbonyl reactants of ribose and glycine was investigated using stable isotopes of the corresponding compounds. It was confirmed that the skeleton of the five-membered ring and the methyl group of the side chain of HEMF was formed from ribose, and that the ethyl group was derived from the glucose metabolite by yeast. The formation of HEMF was confirmed when acetaldehyde as the glucose metabolite and a cell-free extract from yeast were added to the medium containing amino-carbonyl reactants. These results suggest that the role of yeast in HEMF formation is not only to provide the glucose metabolite, but also in combining the amino-carbonyl reactants with the glucose metabolite.