Rice vinegars of different origins: discriminative characteristics based on solid‐phase microextraction and gas chromatography with mass spectrometry,an electronic nose,electronic tongue and sensory evaluation

Eight kinds of commercial rice vinegars from Korea, China and Japan were selected to evaluate their flavour‐related discriminative characteristics based on solid‐phase microextraction and gas chromatography with mass spectrometry (SPME/GC–MS), an electronic nose (e‐nose), electronic tongue (e‐tongue) and subjective sensory evaluation. Principal component analysis patterns based on SPME/GC–MS provided a clear categorical discrimination among the vinegars of three origins. The distribution patterns of the samples were similar between SPME/GC–MS and e‐nose analyses and Korean vinegars were clearly discriminated. A high correlation coefficient was determined between SPME/GC–MS and e‐nose on acetaldehyde (0.948) and diacetyl (0.970). e‐Tongue‐based principal component analysis patterns were subdivided into three regions according to the origin, and Chinese vinegars were clearly discriminated. Sensory panelists recorded origin‐specific scores on flavours for all the samples. In conclusion, SPME/GC–MS, e‐nose and e‐tongue analyses may be useful for discrimination of flavour profiles of rice vinegars of different producer origin. Copyright © 2017 The Institute of Brewing & Distilling     

Application of Electronic Nose for Measuring Total Volatile Basic Nitrogen and Total Viable Counts in Packaged Pork During Refrigerated Storage

The objective of this study was to predict the total viable counts (TVC) and total volatile basic nitrogen (TVB‐N) in pork using an electronic nose (E‐nose), and to assess the freshness of chilled pork during storage using different packaging methods, including pallet packaging (PP), vacuum packaging (VP), and modified atmosphere packaging (MAP, 40% O₂/40% CO₂/20% N₂). Principal component analysis (PCA) was used to analyze the E‐nose signals, and the results showed that the relationships between the freshness of chilled pork and E‐nose signals could be distinguished in the loadings plots, and the freshness of chilled pork could be distributed along 2 first principal components. Multiple linear regression (MLR) was used to correlate TVC and TVB‐N to E‐nose signals. High F and R² values were obtained in the MLR output of TVB‐N (F = 32.1, 21.6, and 24.2 for PP [R² = 0.93], VP [R² = 0.94], and MAP [R² = 0.95], respectively) and TVC (F = 34.2, 46.4, and 7.8 for PP [R² = 0.98], VP [R² = 0.89], and MAP [R² = 0.85], respectively). The results of this study suggest that it is possible to use the E‐nose technology to predict TVB‐N and TVC for assessing the freshness of chilled pork during storage.     

Alcohol,Tannins, and Mannoprotein and their Interactions Influence the Sensory Properties of Selected Commercial Merlot Wines: A Preliminary Study

The objective of this study was to assess the influence of the interaction among alcohol, tannins, and mannoproteins on the aroma, flavor, taste, and mouthfeel characteristics of selected commercial Merlot wines. Merlot wines (n = 61) were characterized for wine chemistry parameters, including pH, titratable acidity, alcohol, glucose, fructose, tannin profile, total proteins, and mannoprotein content. Agglomerative clustering of these physicochemical characteristics revealed 6 groups of wines. Two wines were selected from each group (n = 12) and profiled by a trained sensory evaluation panel. One wine from each group was evaluated using the electronic tongue (e‐tongue). Sensory evaluation results showed complex effects among tannins, alcohol, and mannoproteins on the perception of most aromas, flavors, tastes, and mouthfeel attributes (P < 0.05). The e‐tongue showed distinct differences among the taste attributes of the 6 groups of wines as indicated by a high discrimination index (DI = 95). Strong correlations (r² > 0.930) were reported between the e‐tongue and sensory perception of sweet, sour, bitter, burning, astringent, and metallic. This study showed that interactions among wine matrix components influence the resulting sensory perceptions. The strong correlation between the e‐tongue and trained panel evaluations indicated the e‐tongue can complement sensory evaluations to improve wine quality assessment.     

Qualitative and Quantitative Prediction of Volatile Compounds from Initial Amino Acid Profiles in Korean Rice Wine (makgeolli) Model

In Korean rice wine (makgeolli) model, we tried to develop a prediction model capable of eliciting a quantitative relationship between initial amino acids in makgeolli mash and major aromatic compounds, such as fusel alcohols, their acetate esters, and ethyl esters of fatty acids, in makgeolli brewed. Mass‐spectrometry‐based electronic nose (MS‐EN) was used to qualitatively discriminate between makgeollis made from makgeolli mashes with different amino acid compositions. Following this measurement, headspace solid‐phase microextraction coupled to gas chromatography‐mass spectrometry (GC‐MS) combined with partial least‐squares regression (PLSR) method was employed to quantitatively correlate amino acid composition of makgeolli mash with major aromatic compounds evolved during makgeolli fermentation. In qualitative prediction with MS‐EN analysis, the makgeollis were well discriminated according to the volatile compounds derived from amino acids of makgeolli mash. Twenty‐seven ion fragments with mass‐to‐charge ratio (m/z) of 55 to 98 amu were responsible for the discrimination. In GC‐MS combined with PLSR method, a quantitative approach between the initial amino acids of makgeolli mash and the fusel compounds of makgeolli demonstrated that coefficient of determination (R²) of most of the fusel compounds ranged from 0.77 to 0.94 in good correlation, except for 2‐phenylethanol (R² = 0.21), whereas R² for ethyl esters of MCFAs including ethyl caproate, ethyl caprylate, and ethyl caprate was 0.17 to 0.40 in poor correlation.     

E‐Beam Irradiation for Improving the Microbiological Quality of Smoked Duck Meat with Minimum Effects on Physicochemical Properties During Storage

This study was performed to evaluate the effect of different doses (0, 1.5, 3, and 4.5 kGy) of e‐beam irradiation on the quality parameters (pH, Hunter's parameter, and heme pigment) and stability qualifiers (peroxide value [POV], thiobarbituric acid reactive substances [ TBARSs], and total volatile basic nitrogen [TVBN]) of smoked duck meat during 40 d of storage under vacuum packaging at 4 °C. The initial populations of total bacteria (7.81 log CFU/g) and coliforms (5.68 log CFU/g) were reduced by approximately 2 to 5 log cycles with respect to irradiation doses. The results showed that pH, myoglobin, met‐myoglobin, L^*, a^*, and b^* showed significant differences with respect to different doses and storage intervals; a^* and b^* did not vary significantly because of storage. Higher pH was found in samples treated with 4.5 kGy at 40 d, while the minimum was observed in nonirradiated samples at day 0 of storage. Higher POV (2.31 ± 0.03 meq peroxide/kg) and TBARS (5.24 ± 0.03 mg MDA/kg) values were found in 4.5 kGy‐treated smoked meat at 40 d and the lowest was reported in 0 kGy‐treated meat at initiation of storage (0 d). However, irradiation suppressed TVBN during storage and higher TVBN (7.09 ± 0.32 mg/100 mL) was found in duck meat treated with 0 kGy at 40 d. The electronic nose (e‐nose) effectively distinguished flavor profiles during the different storage intervals. The results showed that different sensory attributes did not vary significantly with respect to the dose of irradiation. We conclude that low dose of e‐beam irradiation and vacuum packaging is beneficial for safety and shelf life extension without affecting the sensory characteristics of smoked duck meat.     

Flavour characteristics of Ilex paraguariensis infusion,a typical Argentine product,assessed by sensory evaluation and electronic nose

Sensory evaluation and electronic nose (E‐nose) technology were applied to study two formulations of a new product intended to have organoleptic characteristics similar to those of Ilex paraguariensis (Saint Hilaire) infusions. Infusions prepared from I paraguariensis, called ‘yerba mate’ in South America, possess distinct sensory properties that were described by trained panellists using a lexicon of 17 terms. The two commercial products were formulated by combining various flavour components and processed as instant powders for infusion. Results from the sensory panel showed that it would be necessary to change the product formulation in order to achieve desirable yerba mate characteristics. Odour, mouthfeel and sweetness intensities would have to be improved. The E‐nose had an array of 32 sensors which were able to discriminate between infusions prepared from yerba mate and from the instant powders. Using stepwise discriminant analysis, the group of sensors that contributed to this classification was identified. The response of these sensors correlated (P < 0.05) with yerba mate odour, mouthfeel and sweetness attributes. Comparison of the results obtained by the two methodologies enabled the E‐nose procedure to be improved and showed that this methodology is suitable for food product development and is a good complement to sensory evaluation. Copyright © 2004 Society of Chemical Industry     

Effects of the cultivation period of sweet potato on the sensory quality of imo‐shochu,a Japanese traditional spirit

Imo‐shochu is a Japanese traditional spirit made from sweet potatoes. Characteristic volatile compounds in imo‐shochu are mainly derived from the sweet potato and its flavour significantly depends on the quality and cultivar of sweet potato used. Thus, the effects of the cultivation period of sweet potatoes on sensory characteristics and composition of volatile compounds of imo‐shochu were investigated. Sweet potatoes (cv. Koganesengan) used in this study were harvested at 120, 150 or 180 days after planting, and each sample was used to prepare imo‐shochu. The imo‐shochu samples were evaluated by eight panellists in a blind study, who ranked them on the basis of various odour and taste attributes. Rank sums were calculated and data were analysed using the Friedman test. The compositions of the volatile compounds in the imo‐shochu samples were analysed using gas chromatography–mass spectrometry (GC‐MS). Sensory evaluations showed that a longer cultivation period of the sweet potatoes enhanced the floral aroma and characteristic taste of imo‐shochu. In addition, imo‐shochu prepared with the sample cultivated for 150 days was evaluated to have a sweeter taste than that prepared with the other samples. The GC‐MS analysis showed that imo‐shochu prepared with the sample cultivated for 180 days contained a lower concentration of monoterpene alcohols, but higher concentrations of β‐damascenone, rose oxide, and fatty acid esters than the imo‐shochu prepared with the sample cultivated for 120 days. These differences in the composition of the volatile compounds affected the sensory qualities of the imo‐shochu. Copyright © 2016 The Institute of Brewing & Distilling     

Change of volatile compounds in fresh fish meat during ice storage

Abstract: The change of volatile compounds in fresh fish meat during 3‐ to 4‐d ice storage was investigated for several fishes using an electronic nose system and a gas chromatography‐mass spectrometer (GC/MS) with headspace solid‐phase micro‐extraction (SPME). Principal component analyses for samples using the electronic nose system revealed that the increase of some volatile compounds during storage was rapid in sardine (Sardinops melanostictus), jack mackerel (Trachurus japonicus), and chub mackerel (Scomber japonicus); moderate in yellowtail (Seriola quinqueradiata), skipjack (Katsuwonus pelamis), and young oriental bluefin tuna (Thunnus thynnus). In contrast to these fishes, the change was little in “white meat” fishes such as red seabream (Chrysophrys major), Japanese seabass (Lateolabrax japonicus), flatfish (Paralichthys olivaceus), puffer (Lagocephalus wheeleri), and bartail flathead (Platycephalus indicus). SPME‐GC/MS analysis showed that some aldehydes and alcohols such as 1‐heptanol, (E)‐2‐octenal, (E)‐2‐hexenal, 1‐pentanol, (E,E)‐2,4‐heptadienal,2,4‐hexadienal, 1‐hexanol, 4‐heptenal, and so forth increased rapidly in jack mackerel and chub mackerel, slowly in skipjack, and a little in red seabream and puffer during the storage. The increase of these compounds was considered to have an effect on the change of electronic nose response. Hexanal was a dominant compound increased from the beginning of the storage in jack mackerel. The increase of volatile compounds was little in red seabream and puffer. The increase of these aldehydes and alcohols was thought to be an appropriate marker for monitoring the freshness of “fresh” fish except for white meat fish. Practical Application: The results of this study are ready to apply for preventing fishy off‐flavor of fisheries products. Lipid oxidative derivatives other than trimethylamine contributed to fresh fish flavor; therefore, to prevent lipid oxidation seemed important.     

Characteristic Flavor of Traditional Soup Made by Stewing Chinese Yellow‐Feather Chickens

The traditional recipe for Chinese chicken soup creates a popular taste of particular umami and aroma. The present study investigated the effects of stewing time (1, 2, and 3 h) on the principal taste‐active and volatile compounds and the overall flavor profile of traditional Chinese chicken soup by measuring the contents of free amino acids (FAAs), 5′‐nucleotides, minerals and volatile compounds and by evaluating the taste and aroma profiles using an electronic nose, an electronic tongue and a human panel. Results showed that the major umami‐related compounds in the chicken soup were inosine 5′‐monophosphate (IMP) and chloride, both of which increased significantly (P < 0.05) during stewing. The taste active values (TAVs) of the equivalent umami concentration (EUC) increased from 4.08 to 9.93 (P < 0.05) after stewing for 3 h. Although the FAA and mineral contents increased significantly (P < 0.05), their TAVs were less than 1. The volatile compounds were mainly hexanal, heptanal, octanal, nonanal, (E)‐2‐nonanal, (E)‐2‐decenal, (E,E)‐2,4‐decadienal, 1‐hexanol, and 2‐pentyl furan. With the prolonged stewing time, the aldehydes first increased and then decreased significantly (P < 0.05), while 1‐hexanol and 2‐pentyl furan increased steadily (P < 0.05). The aroma scores of the chicken soup reached the maximum after stewing for 3 h. The discrepancy in overall flavor characteristics tended to stabilize after 2 h of stewing. In general, stewing time has a positive effect on improving the flavor profiles of chicken soup, especially within the first 2 h.     

Optimization of extraction parameters for quantification of fermentation volatile by‐products in industrial ethanol with solid‐phase microextraction and gas chromatography

The rapid growth of the biofuels industry resulted in new research needs in chemical analysis. Methods for screening and quantification of impurities resulting from changes in feedstock, process and purification are needed. Direct sample injection methods are often not sensitive for lower concentrations. This research, developed an analytical method to simultaneously quantify fermentation volatile by‐products in industrial corn‐based ethanol. These include acetaldehyde, ethyl vinyl ether, 1,1‐diethoxyethane, isoamyl alcohol, isoamyl acetate, styrene, 2‐pentylfuran, ethyl hexanoate, ethyl octanoate, and ethyl decanoate. Headspace solid‐phase microextraction (SPME) coupled with gas chromatography–mass spectrometry (GC–MS) and GC‐FID were used. The effects of SPME coating, concentration, time, and salting out were tested. The optimized method used Carboxen/PDMS 85 µm coating with 10% (v/v) ethanol, 20 s headspace extraction, and no salt addition. The method had values of R² between 0.93 and >0.99 and relative standard deviations between 0.10 and 11.96%. The method detection limits were between 9.5 × 10^?4 to 9.7 × 10^?8 mol/L.This is one of the most comprehensive quantification methods for volatile impurities in raw ethanol to date. This new method was used to quantify 10 prevalent impurities in corn‐based industrial ethanol. Copyright © 2015 The Institute of Brewing & Distilling     

1,3‐Dimethoxybenzene,a newly identified component of port wine

1,3‐Dimethoxybenzene was identified by GC–O, GC–MS and Kovats indices (polar Supelcowax, 1709; non‐polar Rtx‐5MS, 1158) as a new volatile component of port wine. Sensory evaluation described this compound as having a sweet medicinal odour with hazelnut, resinous and woody notes. Respective threshold limits in model wine and port wine were 21 and 47 µg l^?1. Quantitative analysis by GC–MS, using a selected characteristic ion (m/z 138), indicated that young port wines from the 1998 vintage contained up to 3 µg l^?1 whereas ports from the 1999 vintage contained up to 20 µg l^?1. © 2002 Society of Chemical Industry     

Variety‐based discrimination of apple juices by an electronic nose and gas chromatography–mass spectrometry

The variety of raw material plays a crucial role in the quality and authenticity of fruit juices and juice products. To characterise and classify apple juices according to variety on the basis of their volatile compounds, electronic nose (EN) and gas chromatography–mass spectrometry (GC‐MS) were applied to detect the apple juices prepared by eight different varieties. The EN was used to analyse the mixture of volatile compounds as a whole and enabled rapid classification of juice samples when coupled with linear discriminant analysis (LDA). LDA showed a perfect discrimination of apple juices based on varieties. GC‐MS was utilised to illustrate the differences of volatile compounds among juice samples. Identification of volatile compositions and their contents provides useful access to differentiate juices from different varieties.     

Identification of aroma‐active compounds in fresh and stored ‘Mor’ mandarins

In this study, gas chromatography–olfactometry (GC‐O) (sniffing) combined with gas chromatography–mass spectrometry (GC‐MS) analysis was applied to identify volatile aroma‐active compounds in homogenised segments of fresh and stored ‘Mor’ mandarins. The GC‐O nasal impact frequency method was used to identify Twenty‐three aroma‐active compounds, of which seventeen odorants were identified by GC‐MS. The aroma of fresh ‘Mor’ mandarins derived from a mixture of eleven odorants that contribute ‘green’ [(E)‐3‐hexenol and hexanal], ‘fresh’ [(E)‐carveol], ‘fruity’ (ethyl 2‐methylbutanoate), ‘citrus’ (limonene), ‘floral’ (linalool), ‘musty’ (β‐myrecene and γ‐terpinene), ‘potato’ (α‐terpinene), ‘mushroom’ (unknown 2) and ‘cabbage’ (α‐cubebene) odours. During postharvest, storage losses were observed in ‘green’ [(E)‐3‐hexenol] and ‘fresh’ [(E)‐carveol] odours, accompanied by increases in ‘fruity’ (ethyl propanoate) and several unpleasant aromas, such as ‘alcohol’ (ethanol), ‘musty’ [α‐pinene, (E)‐2‐nonenal and 1‐terpinen‐4‐ol] and ‘fatty’ (octyl acetate and δ‐cadinene) odours, all of which possibly account for the observed decrease in sensory acceptability after harvest.     

Odour‐active compounds in mango (Mangifera indica L. cv. Corazón)

Simultaneous distillation–extraction combined with GC‐FID and GC‐MS were used to analyse volatile compounds from mango (Mangifera indica L. cv. Corazón) and to estimate the most odour‐active compounds in the fruit. The analyses led to the identification of 167 components, from which 128 were positively identified. The aroma‐active areas in the gas chromatogram were screened by the application of the aroma extract dilution analysis and by odour activity values. Eighteen odorants were considered as the most odour‐active compounds: (E)‐β‐damascenone, ethyl butanoate, (E,Z)‐nonadienal, ethyl 2‐methylpropanoate, (E)‐2‐nonenal, (E)‐β‐ionone, terpinolene, δ‐3‐carene, β‐caryophyllene, ethyl 2‐methylbutanoate, limonene, myrcene, linalool, γ‐octalactone, nonanal, methyl benzoate, 2,5‐dimethyl‐4‐methoxy‐3(2H)‐furanone and hexanal.     

Effects of 3 Feeding Modes on the Volatile and Nonvolatile Compounds in the Edible Tissues of Female Chinese Mitten Crab (Eriocheir sinensis)

To reveal the impact of different feeding modes on the flavor quality of female Chinese mitten crab (Eriocheir sinensis) this study was conducted to compare the sensory evaluation scores, flavor compounds in meat and hepatopancreas of female E. sinensis fed with 3 feeding modes, that is, natural diets (NDs), traditional diets (TDs), and formulated diets (FDs). The result showed that crabs fed with ND had significantly lower sensory scores than the other 2 feeding modes in both edible tissues. The odor and taste profiles were evaluated by Electronic nose (E‐nose) and tongue (E‐tongue) techniques, respectively; results of perchloric acid showed each edible tissue had significant differences among the 3 modes. Contents of volatile compounds were measured by Headspace‐solid phase micro extraction combined with gas chromatography‐mass spectrometer. A total of 35 and 44 volatile compounds were identified in meat and hepatopancreas, respectively. ND mode of meat had the highest relative odor activity value (ROAV) summation among the 3 diet modes. TD mode of hepatopancreas had significantly higher ROAV summations. Based on the analysis of free amino acids and 5′‐nucleotides, nonvolatile compounds were evaluated by equivalent umami concentration (EUC) and taste active values (TAVs) methods. For both meat and hepatopancreas, TD had the highest contents of umami amino acid, as for the 5′‐nucleotide, FD had the highest 5′‐inosin monophosphate concentrations. Overall, the EUC and TAVs of TD were higher than that of FD, whereas ND mode had the lowest values in the 2 edible tissues. In conclusion, TD mode had the best performance in terms of sensory evaluation, ROAVs of aroma‐active compounds, and nonvolatile active compounds.