Application of Mid- and Near-Infrared Spectroscopy for the Control and Chemical Evaluation of Brine Solutions and Traditional Sea Salts

Mid- and near-infrared spectroscopy methodologies were explored for the analysis of brine solutions and traditional sea salt samples. Brine solutions from different salt pans, corresponding to different stages of sodium chloride crystallisation, were collected. A total of 61 dried and non-dried traditional sea salts were also analysed. Partial least squares regression with leave-one-out cross-validation strategy was applied for the calibration of inorganic constituents Ca²⁺, Mg²⁺ and K⁺, alkalinity as HCO ₃ ^? , SO ₄ ^2? , NO ₂ ^? and NO ₃ ^? and phosphate in brine solutions. Promising results were obtained with the near-infrared (NIR) methodology for brine solutions with coefficients of determination R ²?>?0.90 for Mg⁺², K⁺, HCO ₃ ^? and SO ₄ ^2? . Using mid-infrared, the calibration for H₂PO ₄ ^? was R ²?=?0.85. In relation to the sea salt samples, the strategy adopted was the re-sampling based cross-validation using different spectral pre-processing treatments. In this case, the calibrations using the two IR methodologies fell bellow acceptable levels for the techniques; however, by comparing the R ² coefficient, the results were slightly better when using the NIR spectra of dried sea samples. In general, these results open a new possibility for the IR applications and also bring an opportunity for continuing with the NIR characterization for dried sea salt samples.     

Electron Spin Resonance Analysis of Radiation-Induced Free Radicals in Shells and Membranes of Different Poultry Eggs

Radiation-induced free radicals were investigated in the shells and membranes of ostrich, duck, hen, and quail eggs using electron spin resonance (ESR) spectroscopy. The non-irradiated egg shells and membranes showed a single resonance signal centered at g?=?2.0048?±?0.0001 and 2.0072?±?0.0002, respectively. Upon irradiation (1–3 kGy), a dose-dependent asymmetric ESR signal centered at g?=?1.9998?±?0.0002 was also determined in all eggshell samples, whereas the membranes were found silent for radiation-specific ESR signals. An X-ray diffraction spectrometric study showed the abundance of calcite minerals in the all egg shells. Radiation-induced and trapped CO ₃ ^3? , CO ₃ ^? , and CO ₂ ^? paramagnetic entities in the calcite matrix of egg shells might be responsible for a typical ESR signal. The ESR-based identification of all irradiated eggshells was easily possible in practical dose range (1–3 kGy).     

Coumaroyl quinic acid derivatives and flavonoids from immature pear (Pyrus pyrifolia nakai) fruit

Fourteen compounds were isolated from 60% ethanol extracts of immature pear (Pyrus pyrifolia Nakai cv. Chuhwangbae) fruit using Amberlite XAD-2 column HPLC with guided DPPH radical scavenging assay. Based on MS and NMR analysis, the isolated compounds were identified as 5-O-trans-caffeoyl quinic acid methyl ester (1), malaxinic acid (2), 5-O-trans-p-coumaroyl quinic acid methyl ester (3), 5-O-cis-p-coumaroyl quinic acid methyl ester (4), 5-O-trans-p-coumaroyl quinic acid (5), trans-p-coumaric acid (6), methyl cis-p-coumarate (7), methyl trans-p-coumarate (8), 3,5-O-dicaffeoyl quinic acid (9), (-)-epicatechin (10), (S)-(+)-2-cis-abscisic acid (11), isorhamnetin 3-O-β-d-galacto-pyranoside (12), isorhamnetin-3-O-β-d-glucopyranoside (13), and isorhamnetin 3-O-α-l-rhamnopyranosyl (1→6)-O-β-d-glucopyranoside (14). Six compounds (1, 2, 6, 9, 10, and 13) were identified previously, but other compounds (3–5, 7, 8, 11, 12, and 14) were isolated for the first time from pear.     

Isolation and structural determination of a novel flavonol triglycoside and 7 compounds from the leaves of oriental raisin tree (Hovenia dulcis) and their antioxidative activity

The hot water and ethanol extracts of oriental raisin tree (Hovenia dulcis Thunb) leaves showed DPPH radical scavenging activities. Antioxidants were purified and isolated from hot water and ethanol extracts by various column chromatographic procedures with the guided assay of DPPH radical scavenging. The structure of a novel flavonol triglycoside was determined to kaempferol 3-O-α-l-rhamnopyranoside-7-O-[α-d-glucopyranosyl(1→3)-α-l-rhamnopyranoside] (4). In addition, 7 known compounds were identified as caffeine (1), kaempferol 3,7-O-α-l-dirhamnopyranoside (2), kaempferol 3-O-α-l-rhamnopyranosyl( 1→6)-O-β-d-glucopyranosyl(1→2)-O-β-d-glucopyranoside (3), E-3-carboxy-2-petenedioate 5-methyl ester (5), quercetin 3-O-α-l-rhamnopyranoside (6), kaempferol 3-O-α-l-rhamnopyranoside (7), and quercetin 3-O-β-d-glucopyranoside (8). Compound 1–3 and 5–8 were newly identified in this plant. Quercetin glycosides (5, 7) showed higher DPPH radical scavenging activity than other compounds.     

Flavonoids from Pueraria mirifica roots and quantitative analysis using HPLC

The flavonoids, wighteone (1), naringenin (2), genistein (3), isoliquiritigenin (4), daidzein (5), daidzin (6), genistein-8-C-β-d-apiofuranosyl-(1→6)-O-β-d-glucopyranoside (7), ambocin (8), and genistin (9) were isolated from roots of Pueraria mirifica. Chemical structures of the compounds were determined based on spectroscopic data analysis. Flavonoids 1, 2, 4, 7, and 8 were isolated for the first time. The contents of 6 flavonoids in P. mirifica roots was determined to be 2.5±0.01 (1), 14.8±0.09 (3), 18.6±0.18 (5), 17.3±0.11 (6), 10.4±0.05 (7), and 6.0±0.02 (9) mg/kg, respectively, using HPLC.     

Turbidimetric Behavior of Colloidal Particles in Beer Before Filtration Process

The effect of colloidal particles and yeast on turbidity of Pilsen beer before the filtration process was studied in this work. The colloidal particles are mainly composed of polysaccharides, representing 96.89 %, in second place proteins with a concentration close to 2 %, and polyphenols less than 0.3 %. There is also a very low concentration of yeast (<0.25 %). The presence of different types of particles in the sample caused multimodal histogram in the particle size distribution and four distinct zones were identified: (1) very small individual particles ( $ \overline D = 0.0{\text{6}}\mu {\text{m}} $ ), (2) yeast ( $ \overline D = {\text{3}}\mu {\text{m}} $ ), (3) colloidal aggregates ( $ \overline D = {\text{17}}\mu {\text{m}} $ ), and (4) a zone with a high dispersion of size, with two $ \overline D $ values (101 and 200 μm). Particles size counts well correlate with both the scanning electron microscopy (SEM) digital image analysis, and the turbidity determination. The fractal dimension (D _f) of the aggregates was determined by analyzing the SEM images with the Variogram method, obtaining D _f?>?2.4 values. Those values are typical of aggregates formed by rapid flocculation or diffusion limited aggregation. Results of this study support the formulation of a model valid for the prediction of colloidal particles concentration in beer.     

Moisture movement in wood polypropylene composites

Moisture movement in an extruded wood polypropylene composite was evaluated by exposure to high humidity and immersion of the material in both fresh and seawater. The saturation moisture content was approximately 20 and 19% when exposed to distilled water and seawater, respectively. The moisture diffusion coefficient (D _m) of thin specimens exposed to high humidity was 3.4?×?10^?8?cm² $ / $ s. The D _m of small cubic specimens with extruded surfaces removed submerged in distilled water and seawater were estimated to be 3.1 and 2.3?×?10^?8?cm² $ / $ s, respectively. Use of these diffusion coefficients overestimates the rate of moisture movement in larger extrusion profiles indicating the role of transport phenomenon other than diffusion.     

Angiotensin converting enzyme inhibitory benzopyranoids from Angelica gigas

Angiotensin converting enzyme (ACE) plays a major role in the regulation of blood pressure. The potential antihypertensive activity of Angelica gigas was evaluated in vitro by its ability to inhibit ACE. A methanol extract of A. gigas roots exerted an inhibitory effect against ACE and was fractionated using several organic solvents, including dichloromethane, ethyl acetate, and n-butanol. The n-butanol soluble fraction, which manifested potent ACE inhibitory properties, was further purified via repeated silica gel and RP-18 column chromatography. Three benzopyriansides, such as nodakenin (1), umbelliferone (2), and umbelliferone 6-carboxylic acid (3) were isolated from A. gigas roots. Compounds 1–3 inhibited ACE activity in a dose-dependent manner, with IC₅₀ values of 63.95±0.16, 190.49±0.54, and 158.35±1.53 μM, respectively. The inhibition kinetics analyzed by Lineweaver-Burk plots revealed that the three compounds showed a mixed-type inhibition. The equilibrium constants for the inhibitor binding (K_i) of 1, 2, and 3 were estimated to be 1.56×10^?4, 4.70×10^?4, and 2.17×10^?4 M, respectively. We used A. gigas roots to isolate nodakinin, umbelliferone, and umbelliferone 6-carboxylic acid and tested their inhibition efficacy against ACE for the first time.     

Steaming time effects on the moisture migration and structural properties of Chinese Northern-style steamed bread

The aim of this study was to investigate the steaming time effects on proton transverse relaxation behavior with low field 1H nuclear magnetic resonance and structural properties of Chinese Northern-style steamed bread (CNSB). Three proton populations could be distinguished at the first 4 min: T_2b (0.1–1 ms) corresponded to rigid and exchangeable protons; T₂₂ (9–21 ms) was associated with the water protons in small and large meshes of the dough microstructure; T₂₃ (69–300 ms) was assigned to the water protons on the surface of samples. The starch gelatinization began and the water turned into the integral part of the biopolymer at 6 min, forming T₂₁ (1–3 ms) fraction. The gelatinization effect was strengthened up to 8 min and supplied a more mobile microenvironment, resulting in the increase of T₂₁, A₂₁ and M₂₁. However, the gelatinization process ended at 8 min, bringing about the stabilization of T₂₁, A₂₁ and M₂₁ until 25 min. T₂₂ fraction accounted for the largest proportion during all the steaming process. All variation trends on structural properties of CNSB and T₂ relaxation parameters including T_i, A_i (relative intensity of T_i), and M_i (population abundance of T_i) indicated that 6 and 8 min were the two transitions. The gluten matrix began to be disrupted at 6 min and was quite damaged up to 8 min by scanning electron microscopy. The peaks at 15°, 18°, 20°, and 23° in X-ray diffraction patterns appeared in the first 6 min but were lost up to 8, 10, and 25 min.     

Chemical constituents and antioxidant activity of the Musa basjoo flower

In this study, it was found that the ethyl acetate soluble fraction of Musa basjoo flowers was a rich source of antioxidant, due to its high total phenolic contents and significant antioxidant activity. Ten phenolic compounds were isolated from this plant. They are gallic acid (1), caffeic acid methyl ester (2), guaiacylglycerol (3), 3-(3,4-dihydroxyphenyl)-acrylic acid 1-(3,4-dihydroxyphenyl)-2-methoxy carbonyl ethyl ester (4), thero-guaiacylglycerol 8-O-β-d-glycopyranoside (5), quercitrin (6), buein (7), (2R, 3S)-5,7,3′,4′,5′-pentahydroxyflavanonol (8), isoquercitrin (9) and 1,7-bis(3,4-dihydroxyphenyl)-hepta-4E, 6E-dien-3-one (10). In addition, compounds 1, 2, 4, 6, 7, 8, 9 and 10 possessed potent strong free radical scavenging activity. Compounds 1 and 10 with powerful activity showed the higher content, implying important roles of 1 and 10 for the antioxidant activity of Musa basjoo flower. The study suggested that components of Musa basjoo flower possessed good antioxidant capacities and the species could be used in the prevention of diseases related to oxidant by-products of human metabolism.     

Retrogradation kinetics of chestnut starches cultivated in three regions of Korea

Retrogradation kinetics of chestnut starches from three different regions of Korea were investigated during storage at 4 °C. The retrogradation properties were determined using four DSC characteristics: glass transition temperature (\( {\text{T}}_{\text{g}}^{\prime } \)), ice melting enthalpy (ΔH_i), amylopectin melting enthalpy (?H_r) and degree of retrogradation (DR). The Gongju (GJ) starch showed the highest gelatinization enthalpy (?H_g) value, followed by Gwangyang (GY) and Hadong (HD). \( {\text{T}}_{\text{g}}^{\prime } \) of all samples gradually increased with increasing storage time, while ?H_i decreased as the storage time increased. ?H_r of all samples significantly increased after 2 days of storage. DR, calculated based on ?H_g and ?H_r, showed a similar tendency with ?H_r. The retrogradation rates of three chestnut starches were analyzed using the Avrami equation, and the time constants (1/k) were obtained. GY, GJ and HD showed the fastest retrogradation rate in \( {\text{T}}_{\text{g}}^{\prime } \), ?H_i, and ?H_r, respectively suggesting that each sample experienced different retrogradation kinetics in different region.     

Influence of buffer and l-phenylalanine concentration in the Rhizomucor miehei lipase catalysed synthesis of l-phenylalanyl-d-glucose ester investigated through response surface methodology

Reaction conditions for Rhizomucor miehei lipase (RML) catalysed synthesis of l-phenylalanyl-d-glucose using unprotected l-phenylalanine and d-glucose were optimized using response surface methodology (RSM). A central composite rotatable design (CCRD) was employed involving 32 experiments of five variables (l-phenylalanine concentration in mmol, amount of RML in mg, pH, incubation period in h and buffer concentration in mM) at five levels. A second-order polynomial equation was developed in terms of linear, quadratic and cross product terms to study the effects of variables on esterification yields. A R ² value of 0.7 was obtained for this complex reaction. From the surface and contour plots it was found that higher yields were observed for a very narrow pH range of 4.5–6.5 at l-phenylalanine concentrations above 3 mmol. The extent of esterification decreased with increase in RML concentration for incubation periods below 60 h. However, longer incubation periods above 60 h, enhanced esterification at all RML concentrations. Lower conversions below 0.5 mmol required less than 3.5 mmol l-phenylalanine concentration and a broad range of buffer concentration from 0.1 mM (0.1 ml, 0.1 M buffer of pH 6.0) to 0.5 mM (0.5 ml, 0.1 M buffer of pH 6.0). However, higher conversions from 0.6 to 0.8 mmol required a buffer concentration above 0.25 mM (0.25 ml, 0.1 M buffer of pH 6.0) at l-phenylalanine concentrations above 3.5 mmol. An optimum predicted yield of 1.01 mmol for l-phenylalanyl-d-glucose at 3 mmol l-phenylalanine, 100 mg of RML, 24 h incubation period, 0.5 mM (0.5 ml of 0.1 M buffer), pH 4.8 acetate buffer was found to agree with 0.97 mmol obtained under these experimental conditions. Validation experiments carried out under random conditions also exhibited good correspondence between predicted and experimental yields.     

A novel α-l-rhamnosidase with potential applications in citrus juice industry and in winemaking

The production of monoglycosylated flavonoids by α-l-rhamnosidases (EC 3.2.1.40) is an interesting development in biocatalysis. Applications of rhamnosidases in industry include removal of bitterness caused by naringin from citrus juices. In the present work, a psychrotolerant bacterial strain with α-l-rhamnosidase activity was isolated. The α-l-rhamnosidase was found to be able to degrade naringin and was purified and characterized. The α-l-rhamnosidase from Brevundimonas sp. Ci19 was able to release both rhamnose and prunin from naringin. The enzyme was partially purified with a performance of 2.7-fold purification. The α-l-rhamnosidase showed an optimum pH between 6.00 and 7.00 with substantial residual activity at pH 5.00 (85.3 %). The optimum temperature was between 20 and 37 °C. The enzyme showed activation in the presence of Ca²⁺ and Cd²⁺ ions and at a high ethanol concentration level (10 % v/v). Activity was found for β-d-glucosidase (EC 3.2.1.21) in the partially purified extract, but it was inactive in the acid pH region. This result indicates the potential for inactivation of β-d-glucosidase along with the high level of α-l-rhamnosidase activity necessary for the production of flavonoid glycosides. The α-l-rhamnosidase from Brevundimonas sp. Ci19 showed interesting properties for potential use not only in the citrus juice industry but also in winemaking.     

Time-temperature superposition principle on relaxational behavior of wood as a multi-phase material

The time-temperature superposition principle of wood is discussed by modeling the relaxation spectrum of wood and then the application is examined, considered a high order structure and a multi-phase system for wood. The relaxation spectrum of wood was theoretically derived on the several assumptions. After theoretical calculation on the assumptions, in the relaxation time region where wedge-type spectra overlap each other, which is probable for wood, the spectrum of wood is represented by $$lnH = - M_0 (ln\tau - lnA_T ) + M_1 $$ , whereM ₀ andM ₁ are constants related to volume fractions of wood components.A _T is represented by the following equation as a parameter which is the product of a slope (?b and ?c) of a wedge-type spectrum and a volume fraction (φ _B andφ _C) of a wood component related to the relaxation process: $$lnA_T = \phi _B b/ (\phi _B b + \phi _c c) \cdot lna_{Tb} + \phi _C c/ (\phi _B b + \phi _C c) \cdot lna_{Tc} $$ , wherea _Tb anda _Tc are shift factors of wedge-type spectra of wood components. This equation shows that the apparent shift factorA _T consists of shift factors of the relaxation processes of wood components. Consequently, the time-temperature superposition principle does not unconditionally apply for wood, since the temperature dependence of relaxation times is generally different from each other for relaxation processes of wood components. This can explain the experimental result for wood that relaxation curves at various temperatures do not superpose on a relaxation curve at a reference temperature, that is, the principle cannot be applied.     

Microwave treatment of dietary gelatin does not generate cis-4-hydroxy-l-proline, an inhibitor of collagen biosynthesis

Aqueous solutions (5?g/100?ml) of commercial preparations of (a) an enzymatic partial hydrolysate of gelatin and (b) type A gelatin were subjected to threefold heating to boiling in a domestic microwave oven at 750?W and to conventional heating. Then samples were totally hydrolyzed (6?M hydrochloric acid, 110??°C, 24?h) and investigated for the presence of eight possible stereoisomers of 3- and 4-hydroxyproline (Hyp) using capillary gas chromatography. Amino acids were analyzed as N(O)-trifluoroacetyl 2-propyl esters on Chirasil-l-Val and detected by selected ion monitoring mass spectrometry. Blanks of (a) and (b) were analyzed in parallel. Relative amounts of 5.0±0.2% cis-4-d-Hyp were generated from native trans-4-l-Hyp as a result of total hydrolysis in all samples and independent of previous treatment. Notably, neither cis-3-l-Hyp nor cis-4-l-Hyp could be detected in either of the gelatin samples. Thus a report on the generation of antifibrotic and therefore potentially hazardous cis-3-l-Hyp and cis-4-l-Hyp from protein-bonded native trans-3-l-Hyp and trans-4-l-Hyp on microwave heating of infant formulae could not be confirmed.     

Phytoestrogenic activity of Aceriphyllum rossii and rapid identification of phytoestrogens by LC–NMR/MS and bioassay-guided isolation

Aceriphyllum rossii Engler (Saxifragaceae) has been used as a nutritious food in Korea, but only minimal studies on this plant have been undertaken. We have examined the estrogenic effect of A. rossii and have discovered its potent constituents. To identify the estrogenic activity of A. rossii, we measured the transactivation of the estrogen-responsive element (ERE) in MCF-7 cells transfected with an ERE-containing construct after treatment of the extract and fractions of A. rossii. A. rossii showed a potent estrogenic activity and gallic acid ethyl ester; quercetin and kaempferol were identified as major constituents of the active fractions by liquid chromatography–nuclear magnetic resonance spectroscopy/mass spectrometry. We confirmed quercetin and kaempferol are the major active constituents after activity-guided isolation of seven compounds: gallic acid ethyl ester (1), quercetin (2), kaempferol (3), quercetin-3-O-(6″-galloyl)-β-d-glucopyranoside (4), quercetin-3-O-β-d-glucopyranoside (5), kaempferol-3-O-(6″-galloyl)-β-d-glucopyranoside (6), and kaempferol-3-O-β-d-glucopyranoside (7). These results show A. rossii could be a possible candidate for the treatment of postmenopausal symptoms.     

A regression model describing the effect of pH,NaCl and temperature on<Emphasis Type="Italic"> D</Emphasis> values of<Emphasis Type="Italic"> Bacillus stearothermophilus</Emphasis> spores

A new microbiological predictive model was developed, relating pH, NaCl concentration and temperature (T) with the decimal reduction coefficient D as dependent variable, using data previously reported by [1]. The model was obtained by multiple linear regression using only three predictor variables (T ², pH² and NaCl), easily computed from the basic variables pH, NaCl concentration and temperature (T). The fitted model is robust, stable and satisfies all the basic hypotheses of the regression models. It also provides simplicity when compared with previously published models based on multiple linear regression tools.     

Comparison of total antioxidant potential,and total phenolic,nitrate, sugar,and organic acid contents in beetroot juice,chips, powder,and cooked beetroot

Beetroot is a vegetable rich in nitrate (NO ₃ ^? ), antioxidants and phenolic compounds that are related to improvements in cardiovascular function and exercise performance. However, it is unknown if convenient forms of beetroot administration provide different amounts of these nutrients. The total antioxidant potential (TAP), total phenolic (TPC), sugar, organic acid, and NO ₃ ^? contents of beetroot juice (BJ), chips (BC), powder (BP), and cooked beetroot (CB) were compared. Significant (p<0.01) differences in chemical compositions and functional properties were found between beetroot formulations. Higher amounts of TAP and organic acids were observed in BC and BP, compared with the other formulations. BJ exhibited the highest contents of total sugars, TPC, and NO ₃ ^? . All beetroot formulations were suitable and advantageous based on taste preferences and convenience for consumers and for nutrient amounts required to meet dietary recommendations.     

Non-destructive Assessment of Guava (<Emphasis Type="Italic">Psidium guajava</Emphasis> L.) Maturity and Firmness Based on Mechanical Vibration Response

Storage potential and eating quality of guava (Psidium guajava L.) fruit depend on its maturity. Segregation of guava according to maturity and firmness measured using non-destructive technologies would help the industry to designate ripe fruit to immediate market and less ripe fruit for distant market (e.g., exportation). This research was conducted to evaluate the potential of experimental resonant frequency (f _e) and elasticity index (EI) to estimate fruit firmness, which has been reported to be inversely correlated to its maturity. A maturity index (I _m) was calculated as the ratio of total soluble solids/titratable acidity (TSS/TA). It was proved that TSS, TA, and I _m were significantly correlated (P?<?0.05) to skin firmness (F _s), flesh firmness (F _f), stiffness (S), and analytical resonant frequency (ω _n ), being S the attribute best fitted to I _m (R ²?=?0.77). Since it was observed that f _e and EI were sensitive to changes in fruit firmness, both of them were explored as alternatives to predict F _s, F _f, S, and ω _n of guava fruit. In some cases, EI improved the models to predict guava firmness traits (e.g., F _s vs f _e had a coefficient of determination of R ²?=?0.58, whereas for F _s vs EI, it was R ²?=?0.62). The best model occurred when plotting ω _n vs f _e (R ²?=?0.86), followed by S vs EI (R ²?=?0.84), making these promising features for the development of a new practical application using frequency response measurement as a non-destructive method to assess guava maturity.     

Enantiomeric distribution of odour-active epoxyaldehydes in yuzu (Citrus junos Sieb. ex Tanaka)

The odour-active epoxyaldehydes cis-4,5-epoxy-(E)-2-decenal (1), trans-4,5-epoxy-(E)-2-decenal (2), and trans-4,5-epoxy-(E,Z)-2,7-decadienal (3) are present in yuzu (Citrus junos Sieb. ex Tanaka) volatile oil. These epoxyaldehydes have two chirality centres at the C4 and C5 positions in the epoxide moiety. To date, little is known about the enantiomeric distributions of the expoxyaldehydes in natural products. In this study, we examined the enantiomeric distributions of the epoxyaldehydes in yuzu volatile oil using multidimensional gas chromatography. The standard substrates used for 1 and 3 were synthesised enantioselectively using the Katsuki-Sharpless epoxidation. Standard substrates used for 2 were made via the asymmetric organocatalytic epoxidation with a proline-derivative catalyst. The 4S,5R- and 4R,5S-enantiomers of 1 were obtained in moderate enantiomeric excess (44–66 % ee), while 4S,5S- and 4R,5R-enantiomers of 2 and 3 were obtained in high enantiomeric excess (2, 90–92 % ee; 3, 96 % ee). Enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC-MS) revealed that the chiral centres at C4 and C5 in the cis-form (1) have the (4R,5S) absolute configuration, while trans-forms (2 and 3) have the (4S,5S) configuration. The finding of the absolute configuration at C5 (S) suggests that the optically active epoxyaldehydes may be formed along with retention of the S configuration at C13 of the lipid hydroperoxides 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid (13S-HPOD) or 13(S)-hydroperoxy-9(Z),11(E),15(Z)-octadecatrienoic acid (13S-HPOT) during enzymatic lipid oxidation. Finally, we propose a pathway for the formation of the optically active epoxyaldehydes in yuzu.