Application of Static Headspace GC-MS Method for Selective 1,4-Dioxane Detection in Food Additives.

Efficient detection methods must be developed for 1,4-dioxane due to its suspected status as a human carcinogen, which is highly mobile in food and environmental resources. In this regard, this experiment has been conducted to develop reliable and selective detection and measurement methods by using static headspace (SH) isolation, followed by gas chromatography-mass spectrometry (GC-MS). A new method was developed for determining the spiked 1,4-dioxane contents in a polyethylene glycol 600 (PEG 600). The optimal condition for SH-GC-MS was discussed. The representative ions of 1,4-dioxane and 1,4-dioxane-d8 in the SIM mode of MS are 88 and 96, respectively, and the peaks of the SIM mode were separated and confirmed. The linear range for the method covers 0.25 to 100 mg/L with a coefficient of determination (R2) ≥ 0.999. The method applicability was demonstrated by spike recovery across a variety of food additives (i.e., chlorine bitartrate, choline chloride, polysorbate 20 and 60, and PEG 1000). All spike recovery from the tested samples was in the range of 89.50-102.68% with a precision of 0.44-11.22%. These findings suggest a new analytical method for food safety inspection, and could be applicable for ensuring the safety of foods and environmental and public health on a broad scale.

Comparison of Extraction Methods and Extraction Optimization in Aqueous Two-Phase System for Ethyl Carbamate Analysis in Model Systems for Maesil Wine.

Ethyl carbamate (EC) is a known carcinogen, and therefore its intake is regulated internationally. The objectives of this study were to compare the EC recovery yields under different liquid-liquid extraction (LLE) conditions and to investigate the optimum conditions of the aqueous two-phase system (ATPS) for EC extraction. Our results showed that for the LLE method, addition of 15% NaCl improved the EC yield by 15%, and dichloromethane as the extraction solvent showed a slightly higher yield (about 5%) than chloroform. However, there was little difference in the yield when mixing was performed using an ultrasonic bath compared to a vortex mixer. Using response surface methodology with central composite design to analyze the ATPS results, optimal extraction was found to occur at 21.5°C for 2.8 h in the sample containing 70% alcohol and 15% phosphate, showing a recovery yield of 75.64%. This information can be applied to alcoholic beverages and other fermented food products to analyze EC with better extraction methods, depending on the types of food.

Ethyl Carbamate Formation from Cyanate in Model System of Ethanol-Water Media Using Response Surface Methodology.

Ethyl carbamate (EC) has been identified as a possible human carcinogen belonging to Group 2A. EC is naturally formed during the fermentation and storage of alcoholic drinks and fermented foods. When ingested in large amounts, EC can cause various health problems, such as gastroenteric hemorrhage, vomiting, and cancer. In this study, optimization of EC formation from cyanate was examined using response surface methodology (RSM), a central composite design that includes variables such as alcohol concentration (10, 15, 20, 25, and 30%), pH (2.5, 3.0, 3.5, 4.0, and 4.5), storage temperature (5, 10, 15, 20, and 25°C), and storage duration (2, 4, 6, 8, and 10 days). EC content was determined using gas chromatography with flame ionization detection and the results were optimized using RSM. EC formation from cyanate degradation was found to increase with storage duration and temperature, acidity, and alcohol concentration. Cy-anate degradation was associated with the formation of EC. Approximately 83.1±0.1% of cyanate was degraded to 538±9 µM of EC. However, not all of the cyanate reacted with ethanol during fermentation to form EC. This study aimed to develop the ideal conditions for EC analysis to reduce EC production in alcoholic drinks and fermented foods.

Effects of the Addition of Herbs on the Properties of Doenjang.

Three types of doenjang, a fermented soybean paste, were prepared by adding coriander (CR), Korean mint (KM), and peppermint (PM) and compared to the control group (CN) by studying their metabolite profiles and antioxidant activities followed by different fermentation periods (1, 30, and 150 days, respectively). The primary metabolome was analyzed by GC-TOF-MS, and 36 of metabolites were identified in four types of doenjang samples (CN, CR, KM, and PM). Samples were clustered based on the herb type and fermentation period in PCA and PLS-DA analysis. For the secondary metabolome analysis, UHPLC-Q-orbitrap-MS was used, and 26 metabolites were identified. The statistical analysis showed that the samples were clustered by herb type rather than fermentation period, and the samples containing KM and PM were located in the same group. The DPPH assay showed that PM-containing doenjang had the highest antioxidant activity. Correlation analysis indicated that organic acids such as lactic acid, malonic acid, succinic acid, uracil, vanillic acid, and quinic acid showed positive correlation with the DPPH activity. Overall, our results demonstrated that incorporating herbs in doenjang during fermentation caused significant shifts (p-value < 0.05) in the doenjang metabolites and antioxidant activity. Hence, herbs could be utilized for enhancing doenjang fermentation.

Reduction of Trimethylamine Off-Odor by Lactic Acid Bacteria Isolated from Korean Traditional Fermented Food and Their In Situ Application.

Trimethylamine (TMA) is a well-known off-odor compound in fish and fishery products and is a metabolic product of trimethylamine N-oxide (TMAO) generated by the enzymatic action of microorganisms. The off-odor is a factor that can debase the value of fish and fishery products. The present study aimed to remove TMA using lactic acid bacteria (LAB). A total of fifteen isolates exhibiting the TMA reduction efficacy were isolated from Korean traditional fermented foods. Among these isolates, five LAB isolates (Lactobacillus plantarum SKD 1 and 4; Lactobacillus paraplantarum SKD 15; Pediococcus stilesii SKD 11; P. pentosaceus SKD 14) were selected based on their high TMA reduction efficacy. In situ reduction of TMA efficacy by the LAB cell-free supernatant was evaluated using a spoiled fish sample. The results showed effective TMA reduction by our selected strains: SKD1 (45%), SKD4 (62%), SKD11 (60%), SKD14 (59%), and SKD15 (52%), respectively. This is the first study on TMA reduction by the metabolic activity of LAB and in situ reduction of TMA using cell-free supernatant of LAB. The present finding suggests an economically useful and ecofriendly approach to the reduction of TMA.

Identification of Headspace Volatile Compounds of Blended Coffee and Application to Principal Component Analysis.

Coffee can be blended to create a variety of products to meet consumer's needs. In order to uncover the blending effect of coffee beans, we performed an experiment using principal component analysis (PCA). Twelve varieties of green beans were tested in 11 experimental groups, and the volatile compounds of the beans were analyzed. A total of 41 volatile compounds were identified. PCA was performed on 13 compounds that had a low odor threshold value or a high concentration among the identified compounds. PCA of total volatile compounds showed that principal component (PC) 1 and PC2 were extracted within 80% cumulative dispersion level. In PC1 and PC2, furfuryl alcohol and formic acid ethyl ester showed the greatest positive correlation coefficients among all the volatile compounds. The largest negative correlation coefficients in PC1 and PC2 were 4-hydroxy-2-butanone and 3-(ethylthio)propanal, respectively. Using PCA of the major volatile compounds in coffee, propanal and 1-methylpyrrole were found to have the largest positive correlation coefficients in PC1 and PC2, respectively. In the score plot of the major volatile components, 4 kinds of blended coffee were closely grouped, therefore showing similar aroma qualities. However, 5 kinds of other blended coffees showed a positive correlation with PC2. This is probably due to 3-(ethylthio)propanal acting as a specific value. The application of statistical methods to blended coffee allows for logical and systematic data analysis of data and may be used as a basis for quality evaluation.

Chemical Characterization and Oxidative Stability of Medium- and Long-Chain Fatty Acid Profiles in Tree-Borne Seed Oils.

This study was undertaken to evaluate chemical characteristics and oxidative stability of tree-borne seed oils. A total of 15 different fatty acids were identified in six tree-borne seed oils, which included seven types of saturated fatty acids, four types of monounsaturated fatty acids, and four types of polyunsaturated fatty acids. Japanese camphor tree (JCT) had a high content of medium-chain fatty acids (97.94 ± 0.04%), in which fatty acid composition was distinct from those of the other five plant seed oils. Overall, contents of tocopherols, a type of fat-soluble vitamin, ranged between 3.82 ± 0.04 mg/100 g and 101.98 ± 1.34 mg/100 g, respectively. Phytosterol contents ranged from 117.77 ± 1.32 mg/100 g to 479.45 ± 4.27 mg/100 g, respectively. Of all tree-borne seed oils, ß-sitosterol was the phytosterol at the highest concentration. Contents of unsaponifiables were between 0.13 ± 0.08 and 2.01 ± 0.02, and values of acid, peroxide, and p-anisidine were between 0.79 ± 0.01 and 38.94 ± 0.24 mg KOH/g, 3.53 ± 0.21 and 127.67 ± 1.79 meq/kg, and 2.07 ± 0.51 and 9.67 ± 0.25, respectively. Oxidative stability of tree-borne seed oils was assessed through measurement of oxidation-induction periods. These results should serve as a foundation to identify the potential of tree-borne seed oils in industrial application as well as in providing fundamental data.

Optimization of Maillard Reaction between Glucosamine and Other Precursors by Measuring Browning with a Spectrophotometer.

The individual Maillard reactions of glucose, glucosamine, cyclohexylamine, and benzylamine were studied at a fixed temperature of 120°C under different durations by monitoring the absorbance of the final products at 425 nm. Glucosamine was the most individually reactive compound, whereas the reactions of glucose, cyclohexylamine, and benzylamine were not significantly different from each other. Maillard reactions of reaction mixtures consisting of glucosamine-cyclohexylamine, glucosamine-benzylamine, glucose-cyclohexylamine, and glucose-benzylamine were also studied using different concentration ratios under different durations at a fixed temperature of 120°C and pH 9. Maillard reactions in the pairs involving glucosamine were observed to be more intense than those of the pairs involving glucose. Finally, with respect to the concentration ratios, it was observed that in most instances, optimal activity was realized, when the reaction mixtures were in the ratio of 1:1.

Optimization of Maillard Reaction in Model System of Glucosamine and Cysteine Using Response Surface Methodology.

Sulfur-containing amino acids play important roles in good flavor generation in Maillard reaction of non-enzymatic browning, so aqueous model systems of glucosamine and cysteine were studied to investigate the effects of reaction temperature, initial pH, reaction time, and concentration ratio of glucosamine and cysteine. Response surface methodology was applied to optimize the independent reaction parameters of cysteine and glucosamine in Maillard reaction. Box-Behnken factorial design was used with 30 runs of 16 factorial levels, 8 axial levels and 6 central levels. The degree of Maillard reaction was determined by reading absorption at 425 nm in a spectrophotometer and Hunter's L, a, and b values. ΔE was consequently set as the fifth response factor. In the statistical analyses, determination coefficients (R2) for their absorbance, Hunter's L, a, b values, and ΔE were 0.94, 0.79, 0.73, 0.96, and 0.79, respectively, showing that the absorbance and Hunter's b value were good dependent variables for this model system. The optimum processing parameters were determined to yield glucosamine-cysteine Maillard reaction product with higher absorbance and higher colour change. The optimum estimated absorbance was achieved at the condition of initial pH 8.0, 111°C reaction temperature, 2.47 h reaction time, and 1.30 concentration ratio. The optimum condition for colour change measured by Hunter's b value was 2.41 h reaction time, 114°C reaction temperature, initial pH 8.3, and 1.26 concentration ratio. These results can provide the basic information for Maillard reaction of aqueous model system between glucosamine and cysteine.

Physiochemical Changes and Optimization of Phosphate-Treated Shrimp (Litopenaeus vannamei ) Using Response Surface Methodology.

The objective of this study was to determine the factors responsible for the changed physiochemical properties of unpeeled shrimp treated in cold phosphate solution (2~4°C) with the intervention of 4 factors: phosphate concentration, dipping time, rotation speed, and volume of brine solution. Response surface analysis was used to characterize the effect of the phosphate treatment on shrimps by running 33 treatments for optimizing the experiment. For each treatment, phosphate amount, moisture content, and weight gain were measured. The results showed that phosphate concentration is the most important factor than other factors for facilitating phosphate penetration in the meat of the shrimp and for getting the best result. The optimum condition of phosphate-treated shrimp in this study was 110 to 120 min dipping time, 500 to 550 mL brine solution for 100 g shrimp sample, and 190 to 210 rpm agitation speed. The studied conditions can be applied in fisheries and other food industries for good phosphate treatments.

Headspace volatile compounds of steamed liriopis tuber tea affected by steaming frequency.

Flavor quality of Liriopis tuber tea that was made using a steaming process was studied by measuring changes in headspace volatile compounds. Headspace volatile compounds of the prepared samples were isolated, separated and identified by the combined system of purge & trap, automatic thermal desorber, gas chromatography, and mass selective detector. As steaming frequencies were increased, the area percent of aldehydes decreased from 32.01% to 3.39% at 1 and 9 steaming frequency times, respectively. However, furans and ketones increased from 18.67% to 33.86% and from 9.60% to 17.40% at 1 and 9 times, respectively. The savory flavor of Liriopis tuber tea was due to a decrease in aldehydes contributing a fresh flavor at the 1st steaming process and newly generated furans from nonenzymatic browning with repeated steaming frequencies. These results will provide basic information for quality control of the newly developed Liriopis tuber tea.

Removal of off-flavors from sea tangle (Laminaria japonica) extract by fermentation with Aspergillus oryzae.

This study was conducted to reduce off-flavors from sea tangle (Laminaria japonica) extract since the typical odor of seaweed is an impediment to consumption of seaweed products. Fifty-six odor compounds emitted from the extract were identified using a thermal desorbor and gas chromatography-mass spectrometry. On the basis of expected odor intensity (EOI), isovaleric acid (41.2%), allyl isothiocyanate (22.6%), octanal (11.1%) and acetaldehyde (10.6%) were responsible for about 85.5% of total odor strength in the extract, suggesting that the odor of the extract might mainly be attributed to these compounds. The EOIs of odor compounds were dramatically reduced or disappeared during fermentation by Aspergillus oryzae. Total EOI of the odor compounds decreased about four-fold, compared with that of the raw extract (control) after the four days of fermentation at 30°C with agitation at 120 rpm. These results indicate that microbial fermentation may be a good strategy to reduce off-flavors of seaweeds.

Chemometric Approach to Fatty Acid Profiles in Soybean Cultivars by Principal Component Analysis (PCA).

The purpose of this study was to investigate the fatty acid profiles in 18 soybean cultivars grown in Korea. A total of eleven fatty acids were identified in the sample set, which was comprised of myristic (C14:0), palmitic (C16:0), palmitoleic (C16:1, ω7), stearic (C18:0), oleic (C18:1, ω9), linoleic (C18:2, ω6), linolenic (C18:3, ω3), arachidic (C20:0), gondoic (C20:1, ω9), behenic (C22:0), and lignoceric (C24:0) acids by gas-liquid chromatography with flame ionization detector (GC-FID). Based on their color, yellow-, black-, brown-, and green-colored cultivars were denoted. Correlation coefficients (r) between the nine major fatty acids identified (two trace fatty acids, myristic and palmitoleic, were not included in the study) were generated and revealed an inverse association between oleic and linoleic acids (r=-0.94, p<0.05), while stearic acid was positively correlated to arachidic acid (r=0.72, p<0.05). Principal component analysis (PCA) of the fatty acid data yielded four significant principal components (PCs; i.e., eigenvalues>1), which together account for 81.49% of the total variance in the data set; with PC1 contributing 28.16% of the total. Eigen analysis of the correlation matrix loadings of the four significant PCs revealed that PC1 was mainly contributed to by oleic, linoleic, and gondoic acids, PC2 by stearic, linolenic and arachidic acids, PC3 by behenic and lignoceric acids, and PC4 by palmitic acid. The score plots generated between PC1-PC2 and PC3-PC4 segregated soybean cultivars based on fatty acid composition.