Milk proteins play an essential role in yogurt manufacture, by adsorbing onto the fat globule interface. This study aims to clarify the impacts of milk fat globules on the physicochemical properties of stirred yogurt, by modifying the particle size distribution of fat globules in reconstituted milk. The results show that high-pressure homogenization increased the association between milk proteins and milk fat globules. The zeta potential and protein surface hydrophobicity of reconstituted milk samples increased. Stirred yogurt prepared with reconstituted milk homogenized at high pressure (≥ 20 MPa) exhibited a fine mesoscopic structure with higher water holding capacity and apparent viscosity. Based on transmission electron microscopy and atomic force microscopy, the milk fat globules tended to form effective connections with casein micelles, giving the yogurt a finer network structure and higher viscosity. These findings reveal that controlling milk fat globule size can effectively improve stirred yogurt quality.

In contrast to the freeze-drying process, the rehydration process of freeze-dried foods remains unclear. This study investigated the rehydration of freeze-dried soybean curd, also known as tofu, and elucidated its breakage mechanism during rehydration, which impairs texture. The rehydration of freeze-dried tofu was observed at different water temperatures (20, 40, 70, and 100 °C), with the required rehydration time found to decrease with increasing water temperature. Furthermore, tofu was found to absorb water faster in cracks formed during production than in the porous body. Crack expansion was observed only in high-temperature water, leading to breakage of the tofu. Environmental scanning electron microscopy revealed that tofu expanded when a sufficient amount of water was absorbed. Accordingly, crack expansion in high-temperature water is attributed to the stress concentration at the tip of the crack, which is caused by differences in the rehydration rate and resulting stiffness between the porous body and cracks.

An aminopeptidase was purified from Proteax, a food-grade commercial enzyme reagent derived from Aspergillus oryzae that showed the highest debittering effect on casein hydrolysates among nine such reagents, and its enzymatic characteristics and debittering activities were investigated. Treatment with the enzyme, identified as leucine aminopeptidase A (LapA), on pepsin-degraded casein and cod protein solutions reduced their bitterness and increased the amount of free hydrophobic amino acids such as leucine, valine, isoleucine, and phenylalanine, as well as arginine, tyrosine, and threonine. These results indicated that LapA preferentially released hydrophobic amino acid residues at the amino terminus of peptides including bitter-tasting peptides and reduced the bitterness of protein hydrolysates.

This study compared the behavior of food boluses describing Newtonian and non-Newtonian fluids through a validated human swallowing simulator based on moving particle simulation. The simulation was qualitatively and quantitatively validated through comparisons with videofluorography images. The positions and configurations of the food boluses and normalized brightness of the simulated and videofluorography images during every timestep were similar, and we thought that the simulator can be used to study the mechanism of food bolus behavior. The validated swallowing simulator results show that the key factors for the optimal design of the thickener are the control of the bolus inflow velocity, which is influenced by rheological and tribological properties, prevention of small splash particles, and bolus discharge flow rate from the epiglottis to the esophagus. In addition, we propose an evaluation index for the degree of bolus coherence based on the bolus flow rate and velocity.

Strawberries are a high-value fruit with distinctive characteristics, including having a bright red color and juicy texture. The importance of their texture qualities requires the development of non-destructive analytical methods. This study focuses on the use of silicon-based visible–near infrared (Vis-NIR) spectroscopy to predict the texture qualities of strawberries. The highest correlation values (r) of prediction of firmness were 0.81 (transmittance) and 0.78 (reflectance), while those of brittleness were 0.78 (transmittance) and 0.77 (reflectance). It was found that transmittance mode can predict the texture qualities of strawberries better than reflectance mode. Savitzky-Golay filtering improved the prediction accuracy for most characteristics. The results showed that Vis-NIR spectroscopy, combined with partial least square regression analysis and Savitzky-Golay smoothing, can predict the texture qualities of strawberries at moderate to high accuracy. Further studies are needed to reduce the effects of individual sample sizes and improve prediction accuracy.

Histamine poisoning is a foodborne illness related to the consumption of histamine-accumulated foods. Morganella morganii is one of the major histamine-producing bacteria that contaminate fresh fish. In this study, we isolated and characterized five bacteriophages that infect M. morganii. The host ranges and adsorption patterns of the isolated phages suggest that they have different host recognition mechanisms. In this study, a M. morganii phage cocktail with a combination of seven phages was prepared. Compared to infection with individual phages, treatment with the phage cocktail delayed the growth of M. morganii for a longer duration (with two phages being the exception). The growth of M. morganii and histamine accumulation in the canned tuna flake were inhibited by the phage cocktail. These results suggest that the M.morganii phage cocktail has the potential to serve as a good biocontrol agent with respect to theprevention of M. morganii–associated histamine poisoning.

Bitterness-masking agents support the intake of functional food ingredients, which taste bitter. However, evidence-based methodology to find bitterness-masking agents remains to be established. In the present study, focusing on the fact that a bitter tastant-binding compound is expected to have a bitterness-masking effect, several epigallocatechin gallate (EGCg)-binding peptides were identified from the amino acid sequence of ribulose 1,5-bisphosphate carboxylase/oxygenase using peptide array technology. Deletion analysis and alanine scanning analysis of these peptides revealed that electrostatic interaction contribute strongly to the binding mechanism. EGCg-binding peptides identified in this study, namely, MHFRVLAKALR and FTGLKSTSAFPVTRK, successfully suppressed the activation of the bitter-taste receptor hTAS2R39 by administration of EGCg. These results suggest that peptide array technology can be used to screen bitterness-masking peptides.

Desirable bright cherry-red meat color of tuna depends on the redox state of myoglobin (Mb). Mitochondria involved in energy production in live muscle, also influence the redox state. However, no research has determined metmyoglobin (metMb) reduction in tuna muscle via mitochondria. This study aimed to assess the metMb reductase activity in the mitochondrial fraction from the dark muscle of tuna with a high concentration of Mb. As a result, elevated assay temperature resulted in increasing mitochondrial metMb reductase activity in the range of 10–30 °C. There was no significant change in the activity between pH 5.7–6.8, but a significant decrease was observed at pH 7.0. Furthermore, NADH, as the cofactor, was found to initiate the metMb reduction, while exhaustion of NADH resulted in metMb formation. Therefore, maintenance of NADH concentration was considered to be essential to maintain the color of tuna meat during chilled storage.

Salivation is indispensable for the smooth intake of food and maintenance of oral health. In this study, we investigated how we recognize foods in our mouth, with a focus on the salivary reflex response. Mastication of deacylated gellan gum (DGG) and native gellan gum (NGG) gels induced relatively higher salivation than that induced by the mastication of agar gel, which showed high syneresis. Furthermore, salivation correlated positively with masseter muscle activity for the mastication of agar and DGG gels showing relatively high elasticity and low plasticity. The increase in food volume consumed at one time increased salivation only within a relatively small range; however, the increase in surface area of gels did not affect salivation for the mastication of agar gels. These results enhance our basic understanding of the oral processing of food and provide guidelines for designing a salivation-promoting meal.

The anti-hypertensive effects of hesperidin and hesperidin-containing fermented Mikan tea were investigated in 8-week-old spontaneously hypertensive rats (SHRs) at a dose of 50 mg/kg body weight for both, over 20 weeks. At the end of the protocol, a significant (P < 0.05) reduction in the systolic blood pressure (SBP) of approximately 60 mmHg was observed in the SHRs with the intake of hesperidin and Mikan tea. No change in the heart rate was observed between groups. Hesperidin altered the impaired vasomotor response in 28-week-old SHRs. Investigation of receptor expression related to mitogen-stimulated vasomotor action revealed that the Mas receptor (MasR) in the aorta of hesperidin-administered SHRs was up-regulated, while no changes in angiotensin II-type 1 and type 2 receptor expressions were observed. An increase in cAMP levels was confirmed in the aorta of hesperidin-administered SHRs, demonstrating that anti-hypertensive hesperidin plays a role in vessel regulation via the upregulated-MasR/cAMP axis.

The color of beer, which is a typical example of the Maillard or browning reaction, is mainly attributed to melanoidins. However, as melanoidins are heterogeneous polymers formed by the Maillard reaction, there is little data on the chemical structure of the components responsible for the color of beer. To obtain chemical information on the color components of beer, we here isolated a low-molecular-weight yellow pigment from black beer and identified it using instrumental analyses and an authentic sample. As a result, the pigment was identified as perlolyrine, which is a Maillard reaction product from tryptophan; however, its contribution to the total color of beer was very low. This pigment was present in various kinds of beer at the level of 3.2–14.0 µg/100 mL.

Fatty acid polyglycerol esters are commonly used as emulsifiers in flavor emulsions. In recent years, transparent beverages based on clear flavor emulsions have been developed and are becoming increasingly popular in the market. Here, the quartz-crystal microbalance (QCM) method was applied to investigate the interaction between clear flavor emulsions containing lemon essential oil and lipid bilayers supported on electrodes. Comparative QCM resonance frequency data between clear- and cloudy-type emulsions demonstrated that clear-type emulsions showed smaller frequency changes, suggesting a size-dependent interaction with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). Furthermore, as indicated by the frequency changes, the affinity of clear-type emulsions increased with the increasing 1,2-dimyristoyl-sn-glycero-3-phosphatidyl-glycerol (DMPG) to whole lipid composition ratio. This indicated that surface regions of polyglycerol fatty acid ester emulsions may specifically interact with DMPG in mixed DMPC-DMPG systems. Our results may be helpful in understanding flavor expression and retention in cell membranes.

We investigated the effect of carbonation treatment with heating (CH) in the presence of glycerin fatty acid esters on Bacillus subtilis spores. The inactivation effect of CH was the highest in the presence of monoglycerol monocaprate (MC10). Monoglycerol monolaurate showed the highest bacteriostatic effect. The resistance of spores to CH with MC10 did not change with pre-heat activation. Freshly prepared spores from the surviving spores following CH with MC10 showed resistance similar to that of normal spores. The resistance of spores might be affected by the composition of the spore-forming medium. CH with MC10 enhanced adhesion of MC10 to spores and dipicolinic acid (DPA) release from spores, but did not induce DNA fragmentation. Inactivation of B. subtilis spores by CH with MC10 may be attributable to the impairment of physiological germination and/or decrease in heat resistance, which were induced by enhanced MC10 adhesion and the resultant DPA release.

Eight natto-producing factories were surveyed for the contamination of phages that infect Bacillus subtilis (natto). A total of 160 sampling points, including manufacturing pipelines, instruments, floors, drainage ports, containers, and building facilities were inspected by wiping the surfaces. Virulent phages were detected from 28 survey points in four of the factories. Phages were frequently found in factories that had experienced product spoilage by phage contamination within the past 3 years. Isolated phages were not clonal and variations in their genomes were observed, although some phages were very similar. We developed phage-resistant B. subtilis (natto) strains using isolated phages as indicators. They were resistant against all phages found in the survey and those isolated decades ago from spoiled natto. The yueB gene that codes the receptor for phage SPP1 was not essential for the phages tested in this study to infect B. subtilis (natto) strains.

In this study, we investigated the relationship between the size of food pieces generated by chewing and the taste intensity during mastication, using cubic gels of two sizes made from agarose of different molecular weights. The intensities of both sweetness and saltiness increased to peak intensity and then decreased with increasing number of chewing cycles, irrespective of the gel sample size and of the molecular weight of agarose gels used. The suppression of sweet taste release was strong with high molecular weight agarose gels with a large pre-ingestion size. In the large pre-ingestion size gel, agarose of higher molecular weight required larger differences in gel fragment size for perception of significant differences in the sweetness intensity than agarose of lower molecular weight. The sodium chloride concentration eluted from agarose gel and the perception of taste was positively correlated in the early stage of mastication, but negatively correlated in the late stage.

Studies were performed to investigate the Cadmium (Cd) distribution and Cd-binding proteins in rice kernel. Rice seeds [Oryza sativa L. (Akitakaomachi)] were cultured under Cd stress and after harvesting, the Cd distribution was determined using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The Cd concentrations and amino acid compositions in different storage protein fractions were analyzed using ICP-MS and an amino acid analyzer, respectively. The molecular weights of the Cd-binding proteins were determined by size exclusion chromatography-inductively coupled plasma mass spectrometry (SEC-ICP-MS). The Cd concentrations in rice kernel gradually decreased from the outer bran layers to the endosperm and Cd was particularly concentrated in the embryo, the outer pericarp and the aleurone layer. The Cd concentrations in different proteins fractions decreased in the following sequence: globulin > albumin > glutelin > prolamin. The presence of cysteine and methionine were closely related to the Cd concentration. The molecular weights of three prominent Cd-binding protein fractions were > 2000 k Da, 570 k Da and 131.9 k Da, respectively.

This study was conducted to identify key components that attenuate oral fat sensations in oolong tea. Oolong tea is often consumed with fatty food because of its “refreshing” effects during the course of a meal. We hypothesized that oolong tea gives a cleanness sensation via psychological and physical effects. We showed through a sensory study that oolong tea consumption significantly reduces oral fat sensations as compared to water. Interfacial tension was measured to evaluate the emulsifying properties of teas and its components. Oolong tea and tea-leaf saponins were significantly lower when compared with other teas and major tea components. Furthermore, the emulsion made from tea-leaf saponins and corn oil was stable after 24 h. Moreover, polyphenol enhanced oolong tea showed significantly decreased oral fattiness when compared with oolong tea. Thus, tea-leaf saponins appear to be key components in reducing oral fat sensation.

Ripened sweet rice wines (mirins) are stored at room temperature for several years to produce a well-balanced sweet flavor. We performed reverse-phase HPLC quantitative analysis of d-amino acids in eight ripened mirins by using derivatization reagents, and investigated the influence of the Maillard reaction on amino acid racemization in mirin during maturation. The relative quantities of d-enantiomers (%d) of Asp, Glu, and Ser in mirins matured for seven years or more were higher than in non-ripened mirins. Based on the calculated correlation coefficient between %D and the amount of Amadori rearrangement products (ARPs) analyzed by LC-MS in ripened mirins for each amino acid, Asp showed a statistically significant strong correlation. Finally, we conducted heating experiments using synthetic ARPs. Our results revealed for the first time that Asp was racemized via ARPs under the influence of pH during mirin maturation.