High correlation between octanol-air partition coefficient and aroma release rate from O/W emulsions under non-equilibrium.

Aroma release kinetics determines the palatability of food consumed by humans. Therefore, to estimate release behaviors of aroma compounds is important. We investigated the relationship between the rates of the release of aroma compounds from food matrices and octanol-water, octanol-air, and water-air partition coefficients. The aroma compounds used were limonene, ethyl hexanoate, 2-methylpyrazine, nonanal, benzaldehyde, ethyl benzoate, α-terpineol, geraniol, benzyl alcohol, and octanoic acid. The rates of their release from oil-in-water (O/W) emulsions were measured under non-equilibrium conditions using a purge-and-trap dynamic headspace extraction system. The results indicated that the octanol-air partition coefficients correlated better with the logarithms of the aroma compound release rates than either the octanol-water or the water-air partition coefficients. Furthermore, this correlation was independent of the oil volume ratios in the O/W emulsions. Our findings therefore suggest that octanol-air partition coefficients can be used to predict the release rates of aroma compounds from O/W emulsions.

Effectiveness of water-air and octanol-air partition coefficients to predict lipophilic flavor release behavior from O/W emulsions.

Flavor release from food matrices depends on the partition of volatile flavor compounds between the food matrix and the vapor phase. Thus, we herein investigated the relationship between released flavor concentrations and three different partition coefficients, namely octanol-water, octanol-air, and water-air, which represented the oil, water, and air phases present in emulsions. Limonene, 2-methylpyrazine, nonanal, benzaldehyde, ethyl benzoate, α-terpineol, benzyl alcohol, and octanoic acid were employed. The released concentrations of these flavor compounds from oil-in-water (O/W) emulsions were measured under equilibrium using static headspace gas chromatography. The results indicated that water-air and octanol-air partition coefficients correlated with the logarithms of the released concentrations in the headspace for highly lipophilic flavor compounds. Moreover, the same tendency was observed over various oil volume ratios in the emulsions. Our findings therefore suggest that octanol-air and water-air partition coefficients can be used to predict the released concentration of lipophilic flavor compounds from O/W emulsions.

Authentication of commercial spices based on the similarities between gas chromatographic fingerprints.

BACKGROUND: A simple and solvent-free method was developed for the authentication of commercial spices. The similarities between gas chromatographic fingerprints were measured using similarity indices and multivariate data analyses, as morphological differentiation between dried powders and small spice particles was challenging. The volatile compounds present in 11 spices (i.e. allspice, anise, black pepper, caraway, clove, coriander, cumin, dill, fennel, star anise, and white pepper) were extracted by headspace solid-phase microextraction, and analysed by gas chromatography-mass spectrometry. RESULTS: The largest 10 peaks were selected from each total ion chromatogram, and a total of 65 volatiles were tentatively identified. The similarity indices (i.e. the congruence coefficients) were calculated using the data matrices of the identified compound relative peak areas to differentiate between two sets of fingerprints. Where pairs of similar fingerprints produced high congruence coefficients (>0.80), distinctive volatile markers were employed to distinguish between these samples. In addition, hierarchical cluster analysis and principal component analysis were performed to visualise the similarity among fingerprints, and the analysed spices were grouped and characterised according to their distinctive major components. CONCLUSION: This method is suitable for screening unknown spices, and can therefore be employed to evaluate the quality and authenticity of various spices. © 2017 Society of Chemical Industry.

Increase in hydrophobicity of Bacillus subtilis spores by heat, hydrostatic pressure, and pressurized carbon dioxide treatments.

The effects of heat treatment (HT), hydrostatic pressure treatment (HPT), and pressurized carbon dioxide treatment (CT) on surface hydrophobicity of B. subtilis 168 spores were investigated. The spore surface hydrophobicity was measured by determining the ratio of hydrophobic spores (RHS) that were partitioned into the n-hexadecane phase from the aqueous spore suspension. The RHS after HT generally increased in a temperature-dependent manner and reached approximately 10% at temperatures above 60°C. The effects of pressurization by HPT and accompanying temperature on increased RHS were complex. The highest RHS after HPT was approximately 17%. Following CT, RHS reached approximately 80% at 5 MPa at 80°C for 30 min. An increased treatment temperature enhanced RHS by CT. The increase in RHS by CT led to the formation of spore clumps and adhesion of spores to hydrophobic surfaces. Acidification of spore suspension to pH 3.2, expected pH during CT, by HCl also increased the adhesion of spores at the similar degree with CT. The spore surface zeta potential distribution was not changed by CT. Furthermore, spores with increased RHS after CT had germination-like phenomena including loss of their refractility and enhanced staining by 4',6-diamidino-2-phenylindole. Physiological germination that was induced by the addition of l-alanine also increased the RHS. From these results, it is clear that CT under heating considerably increases RHS. CT under heating considerably increases RHS. This increase in RHS may be due to acidification or germination-like phenomena during CT.

Extraction of Volatile Flavor Compounds From Tobacco Leaf Through a Low-Density Polyethylene Membrane.

A low-density polyethylene (LDPE) membrane pouch method was developed to extract volatile flavor compounds from tobacco leaf. Tobacco leaf suspended in water was enclosed in a pouch prepared from a LDPE membrane of specific gravity 0.92 g/cm3 and 0.03 mm thickness and then extracted with diethyl ether. In comparison with direct solvent extraction, LDPE membrane excluded larger and higher boiling point compounds which could contaminate a gas chromatograph inlet and damage a column. Whilst being more convenient than a reduced-pressure steam distillation, it could extract volatile flavor compounds of wide range of molecular weight and polarity. Repeatabilities in the extracted amounts were ranged from 0.38% of 2.3-bipyridyl to 26% of ß-ionone, and average value of 39 compounds was 5.9%.

Preparation of reminiscent aroma mixture of Japanese soy sauce.

To prepare an aroma mixture of Japanese soy sauce by fewest components, the aroma concentrate of good sensory attributes was prepared by polyethylene membrane extraction, which could extract only the volatiles with diethyl ether. GC-MS-Olfactometry was done with the aroma concentrate, and 28 odor-active compounds were detected. Application of aroma extract dilution analysis to the separated fraction revealed high flavor dilution factors with respect to acetic acid, 4-hydroxy-2(or5)-ethyl-5(or2)-methyl-3(2H)-furanone (HEMF), 3-methyl-1-butanol (isoamyl alcohol), and 3-(methylsulfanyl)propanal (methional). A model aroma mixture containing above four odorants showed a good similarity with the aroma of the soy sauce itself. Consequently, the reminiscent aroma mixture of soy sauce was prepared in water. The ratio of acetic acid, HEMF, isoamyl alcohol, and methional was 2500:300:100:1.

L-Lactic acid production from glycerol coupled with acetic acid metabolism by Enterococcus faecalis without carbon loss.

Glycerol is a by-product in the biodiesel production process and considered as one of the prospective carbon sources for microbial fermentation including lactic acid fermentation, which has received considerable interest due to its potential application. Enterococcus faecalis isolated in our laboratory produced optically pure L-lactic acid from glycerol in the presence of acetic acid. Gas chromatography-mass spectrometry analysis using [1, 2-(13)C2] acetic acid proved that the E. faecalis strain QU 11 was capable of converting acetic acid to ethanol during lactic acid fermentation of glycerol. This indicated that strain QU 11 restored the redox balance by oxidizing excess NADH though acetic acid metabolism, during ethanol production, which resulted in lactic acid production from glycerol. The effects of pH control and substrate concentration on lactic acid fermentation were also investigated. Glycerol and acetic acid concentrations of 30 g/L and 10 g/L, respectively, were expected to be appropriate for lactic acid fermentation of glycerol by strain QU 11 at a pH of 6.5. Furthermore, fed-batch fermentation with 30 g/L glycerol and 10 g/L acetic acid wholly exhibited the best performance including lactic acid production (55.3 g/L), lactic acid yield (0.991 mol-lactic acid/mol-glycerol), total yield [1.08 mol-(lactic acid and ethanol)]/mol-(glycerol and acetic acid)], and total carbon yield [1.06 C-mol-(lactic acid and ethanol)/C-mol-(glycerol and acetic acid)] of lactic acid and ethanol. In summary, the strain QU 11 successfully produced lactic acid from glycerol with acetic acid metabolism, and an efficient fermentation system was established without carbon loss.

Effect of citrate ions on the softening of root crops prepared with freeze-thaw impregnation of macerating enzymes.

UNLABELLED: Freeze-thaw impregnation is a technique used for the rapid impregnation of substances into foodstuffs. Freeze-thaw impregnation with macerating enzymes has been applied to soften foodstuffs, while retaining their original shapes and flavors. In this study, we found that co-impregnation with citrate ions and macerating enzymes significantly facilitated the softening of root crops. When burdock roots were processed by the impregnating solution at pH 4.0-5.0, co-impregnated burdock roots exhibited 1/6-1/3 firmness values compared with burdock roots impregnated with only enzymes. The impregnation with citrate ions alone at pH 4.0 to 5.0 did not soften burdock roots. The firmness of burdock roots was positively correlated with the amount of water-insoluble calcium in the samples. The results suggested that the degradation of pectins by pectinolytic activities could promote contact with citrate to bridging-calcium ions interacting with the pectin chains. Therefore, the softening by the synergistic effect of citrate ions and macerating enzymes was related to the amount of pectins contained in root crops. That is, the synergistic effect was significant with burdock roots and carrots (from which 50% of polysaccharides are pectins) unlike with lotus rhizomes and bamboo shoots (from which 30% and 10% of polysaccharides are pectins, respectively). PRACTICAL APPLICATION: Freeze-thaw impregnation with macerating enzymes and citrate ions can be applied for the production of care foods which can be eaten without chewing. The softened products induce the pleasure of eating for consumers because their original shapes and flavors are retained.

Effects of high-pressure carbonation on intracellular ATP and NADH levels and DNA damage in Escherichia coli cells.

In order to understand the microbial inactivation mechanism of high-pressure carbonation (HPC), we examined the changes in the activity of the respiratory chain and DNA damage in Escherichia coli cells. HPC was performed under 1-6 MPa at 30°C for 1 min. The increase in CO2 pressure decreased the number of viable cells of E. coli, intracellular ATP, and intracellular NADH, and increased the number of apurinic/apyrimidinic sites. These results indicate that HPC has a detrimental effect on the functioning of the respiratory chain in E. coli and induces DNA damage, which could result in the death of the bacterial cells.

Combined effects of carbonation with heating and fatty acid esters on inactivation and growth inhibition of various bacillus spores.

The effects of carbonation treatment (1 to 5 MPa, 30 min) plus heat treatment (30 to 80°C, 30 min) in the presence of various fatty acid esters (FAEs; 0.05 and 0.1%, wt/vol) on counts of viable Bacillus subtilis spores were investigated. FAEs or carbonation alone had no inactivation or growth inhibition effects on B. subtilis spores. However, carbonation plus heat (CH; 80°C, 5 MPa, 30 min) in the presence of mono- and diglycerol fatty acid esters markedly decreased counts of viable spores, and the spore counts did not change during storage for 30 days. The greatest decrease in viable spore counts occurred in the presence of monoglycerol fatty acid esters. Under CH conditions, inactivation and/or growth inhibition occurred at only 80°C and increased with increasing pressure. The greatest decrease in spore counts (more than 4 log units) occurred with CH (80°C, 5 MPa, 30 min) in the presence of monoglycerol fatty acid esters. However, this treatment was less effective against Bacillus coagulans and Geobacillus stearothermophilus spores.

The effect of low-pressure carbonation on the heat inactivation of Escherichia coli.

The heat inactivating effect of low-pressure carbonation (LPC) at 1 MPa against Escherichia coli was enhanced to 3.5log orders. This study aimed to investigate the mechanisms of this increase in heat inactivation efficiency. The increased inactivation ratio was found to be the result of LPC-induced heat sensitization. This sensitization was not due to any physical damage to the cells as a result of the treatment. Following the depletion of intracellular ATP, the failure of the cells to discard protons caused an abnormal decrease in the intracellular pH. However, in the presence of glucose, the inactivation ratio decreased. In addition, a further increase in inactivation of more than 2log orders occurred in the presence of the protein synthesis inhibitor chloramphenicol. Hence, the decreased heat resistance of E. coli under LPC was most likely due to a depletion of intracellular ATP and a decreased capacity for protein synthesis.

The effects of high hydrostatic pressure treatment on the flavor and color of grated ginger.

High hydrostatic pressure (HHP) was applied to grated ginger in order to inactivate quality-degrading enzymes in a non-thermal manner. The effects of HHP treatment on the flavor and the color of the grated ginger were investigated just after treatment and during storage. After HHP treatment (400 MPa, 5 min), geraniol dehydrogenase (GeDH) was inactivated to less than 5%, but the activity of polyphenol oxidase (PPO) was reduced only to 37%. Heat treatment (100 °C, 10 min) inactivated GeDH to 43% and PPO to about 10%. In storage, the reduction of geranial, neral, and citronellal to the corresponding alcohols was observed in the untreated and the heat-treated ginger, while it was not in the HHP-treated grated ginger. In the HHP-treated sample, terpene aldehydes almost disappeared without the formation of the corresponding alcohols. Browning was not observed immediately after HHP treatment, while it was complete in the heat-treated sample. The color change during storage appeared to reflect the residual activity of PPO.

Enzyme inactivation and quality preservation of sake by high-pressure carbonation at a moderate temperature.

The effect of a high-pressure carbonation treatment on the change in quality of sake during storage was investigated. Measurements of the amino acidity and isovaleraldehyde content of carbonated sake (20 MPa pressure at 40, 45 and 50 degrees C for 7, 21 and 33 min, respectively) as well as of heat-treated sake (reaching temperature of 65 degrees C and immediately cooled) were almost unchanged during storage at 3 and 20 degrees C. Glucose in the sake subjected to these treatments was retained at an almost constant under the same storage conditions, except for the sake carbonated at 40 degrees C and stored at 20 degrees C. In contrast, the amino acidity, and glucose and isovaleraldehyde contents of non-pasteurized (fresh) sake increased during storage at both temperatures. The sake samples subjected to the carbonation treatment and heat treatment both gave better sensory scores than the fresh sake sample after 6 month of storage at 3 and 20 degrees C, especially at 3 degrees C for the flavor. These results suggest that the high-pressure carbonation treatment is an effective new technique for preserving the quality of sake.

Mechanisms behind tailing in the pressure inactivation curve of a clinical isolate of Escherichia coli O157:H7.

The tailing in pressure inactivation curve of clinically isolated Escherichia coli O157:H7 was investigated. A typical tailing was observed after the treatment period for 30min when 10(7) CFU/ml of the cell suspension was subjected to pressure treatment at 300MPa and 25 degrees Celsius. There was no effect on the tailing profiles by the addition of pressure-killed cells and released cellular components. When cells survived at a tail portion were re-propagated (tail-culture) and subjected to second pressure treatment, the cells of the tail-culture exhibited eminently higher barotolerance compared to those of the original-culture, suggesting that the presence of genetically pressure-resistant subpopulation was responsible for the tailing. The cytoplasmic membrane of the tail-culture cells had higher stability to a pressure treatment at 100MPa for 10min than that of the original-culture, which was evidenced by lower permeability to ethidium bromide. The addition of non-ionic surfactants including 0.5microl/ml polyoxyethylene p-t-octylphenyl ester (Triton X-100) and 0.53mg/ml lauric sugar ester dramatically reduced the level of tailing and made the inactivation curve linear.

Inactivation of Bacillus spores by the combination of moderate heat and low hydrostatic pressure in ketchup and potage.

The combination effect of moderate heat and low hydrostatic pressure (MHP) on the reduction of Bacillus subtilis, Bacillus coagulans and Geobacillus stearothermophilus spores in food materials (potage and ketchup) was investigated. These bacterial spores were suspended in potage (pH 7), acidified potage (pH 4), neutralized ketchup (pH 7) and ketchup (pH 4). The suspensions were treated with and without pressure (100 MPa) and temperatures of 65-85 degrees C for 3 to 12 h. The bacterial spores were inactivated by 4-8 log cycles during MHP treatment in potage, acidified potage and ketchup, whereas the spores were highly resistant to long time heat treatment in potage and neutralized ketchup. The degrees of spore destruction were mostly dependent on pH and medium composition during MHP treatment. The inactivation effect in MHP treatment was higher at the pH 7 than at pH 4 both in ketchup and potage. The bacterial spores showed higher inactivation in potage than ketchup during MHP treatment.

Inactivation of enzymes in fresh sake using a continuous flow system for high-pressure carbonation.

The Inactivation kinetics of alpha-glucosidase, glucoamylase, alpha-amylase, and acid carboxypeptidase in fresh sake using a continuous flow system for high-pressure carbonation were investigated. In addition, the effects of ethanol and sugar concentrations on inactivation of the enzymes in high-pressure carbonated sake were investigated. Among the enzymes investigated, alpha-glucosidase was the most stable and alpha-amylase was the most labile on inactivation under carbonation. The decimal reduction times (D values) of alpha-glucosidase, glucoamylase, alpha-amylase (extrapolated from the Z value), and acid carboxypeptidase were 29, 6, 2, and 5 min respectively at 45 degrees C. These values are lower than those subjected to heat treatment. On the carbonation treatment as well as the heat treatment, ethanol accelerated the inactivation of all four enzymes, but glucose depressed the inactivation of these enzymes, except for acid carboxypeptidase. These results suggest that this continuous flow system enabled effective inactivation of enzymes in fresh sake.

Effects of minerals on resistance of Bacillus subtilis spores to heat and hydrostatic pressure.

Among Bacillus subtilis IFO13722 spores sporulated at 30, 37, and 44 degrees C, those sporulated at 30 degrees C had the highest resistance to treatments with high hydrostatic pressure (100 to 300 MPa, 55 degrees C, 30 min). Pressure resistance increased after demineralization of the spores and decreased after remineralization of the spores with Ca(2+) or Mg(2+), whereas the resistance did not change when spores were remineralized with Mn(2+) or K(+), suggesting that former two divalent ions were involved in the activation of cortex-lytic enzymes during germination.

Identification of distinctive volatile compounds in fish sauce.

To make clear the distinctive odorants of fish sauce, addition tests were carried out with respect to deodorized fish sauce samples. Volatiles from the headspace gas of nontreated fish sauce and deodorized fish sauce were characterized by gas chromatography-olfactometry and gas chromatography-mass spectrometry. Four compounds contributing to the distinctive odor of fish sauce were 2-methylpropanal, 2-methylbutanal, 2-ethylpyridine, and dimethyl trisulfide. Addition tests (quantitative descriptive analysis) with respect to the four odorants showed that contributors to the fishy aroma were 2-ethylpyridine and dimethyl trisulfide and that all four odorants contributed to the sweaty aroma. Furthermore, the fecal note of fish sauce was essential with 2-ethylpyridine and dimethyl trisulfide, and the rancid note was essential with all four odorants.