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.

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.

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.

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 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.

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.

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.

Effect of feed gas composition of gas discharge plasmas on Bacillus pumilus spore mortality

AIMS

To investigate the effect of gas composition on the sensitivity of Bacillus pumilus spores to gas plasmas.

METHODS AND RESULTS

Inert gas plasmas, oxygen-based plasmas and various moisturized air plasmas were used to inactivate B. pumilus spores in low gas pressure of 50 Pa. Although the treatment temperature did not exceed 55 degrees C when exciting these plasmas, spore survival varied widely depending on the composition of the gas feed. Higher spore mortality was acquired by inert gases of low molecular weight except for helium. The highest spore mortality (4.54log reduction) was obtained when air with a 0.05 molar fraction of water vapour was used as the plasma carrier gas.

CONCLUSIONS

Water molecules in the plasma carrier gas play a significant role in inactivation of B. pumilus spores.

SIGNIFICANCE AND IMPACT OF THE STUDY

This strong inactivation may occur through hydroxyl free radicals generated from the moisturized air plasma.