Namhyeok Chung

E-Beam Irradiation for Improving the Microbiological Quality of Smoked Duck Meat with Minimum Effects on Physicochemical Properties During Storage: E-beam irradiation for improving…

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, Hunters 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.

Optimization and modeling for heat reflux extraction of total yield, stevioside and rebaudioside-A from Stevia rebaudiana (Bertoni) leaves

ABSTRACT Stevia rebaudiana (Bertoni) leaves consist of stevioside and rebaudioside-A (Reb-A). This research sought to improve extraction of target steviol glycosides from stevia leaf powder using response surface methodology (RSM) and artificial neural networking (ANN) under these independent variables: ethanol concentration, X1 (0–100%), extraction temperature, X2 (55–75°C), and extraction time, X3 (45–75 min). ANN outperformed as potential alternative to RSM in predicting optimum conditions. Maximum responses were obtained at 100% X1, 55°C X2, and 60 min X3. Heat reflux extraction proved superior to maceration extraction in terms of higher extraction yields with reduced energy consumption and CO2 emission.

Comparative analysis of sensory profiles of commercial cider vinegars from Korea, China, Japan, and US by SPME/GC-MS, E-nose, and E-tongue

Solid phase microextraction and gas chromatography-mass spectrometry (SPME/GC-MS), electronic nose, and electronic tongue were used to characterize the sensory profiles of cider vinegars from Korea (K1-2), China (C1-2), Japan (J1-2), and US (U1-2). SPME-GC/MS detected acetic acid as the common volatile compound in all vinegars, in addition to isovaleric acid, octanoic acid, and phenethyl acetate. Acids and acetic esters were the major components of Korean and US vinegar samples, respectively. Chinese vinegars had high ethyl acetate content, while Japanese samples were characterized by a low content of acetic acid. Principal component analysis (PCA) pattern provided a clear categorical discrimination of Chinese vinegars by E-nose and E-tongue analyses. The instrumental sensory scores and the taste attributes for flavor (r=0.9431), sourness (r=0.9515), and sweetness (r=0.8325) were highly correlated. Therefore, SPME/ GC-MS, E-nose, and E-tongue analyses may be useful tools to discriminate the sensory profiles of cider vinegars of different origins.

Physicochemical Qualities and Flavor Patterns of Traditional Chinese Vinegars Manufactured by Different Fermentation Methods and Aging Periods

Physicochemical properties of Fujian Yongchun aged vinegar (FYAV) and Shanxi mature vinegar (SMV) were compared in terms of the fermentation methods applied and aging periods (3, 5, 8, and 10 years), and combined E-nose/E-tongue analyses were performed to assess their flavors. Compared with submerged fermentation-derived FYAV, solid-state fermentation-derived SMV showed higher values of pH, brix, soluble solids, total phenolic content, and antioxidant activity, but not total acidity or total organic acids. Aging period resulted in an increase in pH, total phenolic content, and antioxidant activity. Principal component analysis based on E-tongue/E-nose analyses was performed to distinguish between the vinegars produced by different fermentation methods and under aging periods. Solid-state fermentation and an aging process were considered good techniques for vinegar brewing, considering the various organic acids and high levels of total phenolics and antioxidant activity.

Application of E-tongue, E-nose, and MS-E-nose for discriminating aged vinegars based on taste and aroma profiles

The combined approach of E-senses was undertaken to discriminate the taste and aroma profiles of aged vinegars, including Chinese Shanxi extra aged vinegar (EX, 5-8 years), Japanese black vinegar (BL, 1-5 years), and Italian balsamic vinegar (BA, 8-25 years). The principal component analysis plot for E-tongue revealed that EX, BL, and BA formed individual groups with clear distinctions. The volatile compounds detected in E-nose based on Kovats indices represented that a major component in all vinegars was matched to acetic acid, which showed a strong relationship with the aging period (R=0.8186−0.9998). The discriminant function analysis plot accompanied by the MS-E-nose indicated that more volatiles were produced during prolonged aging in cereal vinegar, whereas the aging process degraded volatile constituents in fruit vinegar. Categorization with respect to aging years was possible using both E-noses. The approach using E-senses indicated a better discrimination for distinguishing the complex sensory information in aged vinegars.