Production of Low Salted and Fermented Shrimp by Irradiation

ABSTRACT: Shrimp ( Acetes chinensis ) were sliced, washed, and then salted with 15 and 20% (w/w) sodium chloride. Salted shrimp was 0, 5, and 10 kGy-irradiated at 2 different stages: 1) irradiated immediately after processing salted shrimp, 2) irradiated at optimum fermentation period, and fermented at 15 °C for 10 weeks. Nonirradiated shrimp with 30% salt were also prepared as a control. Irradiated shrimp were not different in proximate composition, salinity, and water activity from nonirradiated shrimp with the same salt addition and the same irradiation time. During fermentation, volatile basic nitrogen (VBN) contents increased as the salt concentration and irradiation dose decreased. From results of sensory analysis, total bacterial count, and pH, the combination of low salt concentration (15% or 20%) and gamma irradiation (5 or 10 kGy) was effective in processing low-salted and fermented shrimp. Results provided no adverse sensory quality and improved micro-bial shelf-stability compared to control (30% of salt addition).     

Irradiation Effects on Biogenic Amines in Korean Fermented Soybean Paste During Fermentation

ABSTRACT: Irradiation effects on biogenic amines (BAs) and microbiological populations of Korean fermented soybean paste were investigated during fermentation. Soybean paste was prepared and irradiated with doses of 5,10, and 15 kGy, and then fermented at 25 °C for 12 wk. Bacillus spp. and lactic‐acid bacteria decreased by irradiation but increased during fermentation. Biogenic amines detected were putrescine, cadaverine, β‐phenylethylamine, spermidine, spermine, tryptamine, histamine, tyramine, and agmatine. A significant difference was not observed in BA content between control and irradiated samples immediately after gamma irradiation. However, 4 kinds of BAs, putrescine, tryptamine, spermidine, and histamine, showed significant reduction by irradiation during fermentation (P < 0.05).     

Experimental hover performance evaluation on a small-scale rotor using a rotor test stand

This paper presents the work being carried out in order to deduce hover performance of a small-scale single rotor blade as a preliminary study of a small coaxial rotor helicopter development. As an initial research, a test stand capable of measuring thrust and torque of a small-scale rotor blade in hover state was constructed and fabricated. The test stand consists of three parts; a rotating device, a load measuring sensor and a data acquisition system. Thrust and torque were measured with varying collective pitch angle at fixed RPM. Through this research, hover performance tests were conducted for a small-scale single rotor blade operating in low Reynolds numbers (Re ≈ 3 × 10⁵). The rotor blades investigated in this paper have maximum FM values varying from 0.59 to 0.65, which are low relative to modern full-scale helicopters. From these differences in FM between a small and a full-scale helicopter, the induced power factor is determined as varying from 1.35 to 1.42. Through this study, tests of hover performance were conducted for a single small-scale rotor blade, as well as verifying the test stand itself for the acquisition of hover performance.     

Dieckol Attenuated Glucocorticoid-Induced Muscle Atrophy by Decreasing NLRP3 Inflammasome and Pyroptosis

Dexamethasone (Dexa), frequently used as an anti-inflammatory agent, paradoxically leads to muscle inflammation and muscle atrophy. Receptor for advanced glycation end products (RAGE) and Toll-like receptor 4 (TLR4) lead to nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3 (NLRP3) inflammasome formation through nuclear factor-κB (NF-κB) upregulation. NLRP3 inflammasome results in pyroptosis and is associated with the Murf-1 and atrogin-1 upregulation involved in protein degradation and muscle atrophy. The effects of Ecklonia cava extract (ECE) and dieckol (DK) on attenuating Dexa-induced muscle atrophy were evaluated by decreasing NLRP3 inflammasome formation in the muscles of Dexa-treated animals. The binding of AGE or high mobility group protein 1 to RAGE or TLR4 was increased by Dexa but significantly decreased by ECE or DK. The downstream signaling pathways of RAGE (c-Jun N-terminal kinase or p38) were increased by Dexa but decreased by ECE or DK. NF-κB, downstream of RAGE or TLR4, was increased by Dexa but decreased by ECE or DK. The NLRP3 inflammasome component (NLRP3 and apoptosis-associated speck-like), cleaved caspase -1, and cleaved gasdermin D, markers of pyroptosis, were increased by Dexa but decreased by ECE and DK. Interleukin-1β/Murf-1/atrogin-1 expression was increased by Dexa but restored by ECE or DK. The mean muscle fiber cross-sectional area and grip strength were decreased by Dexa but restored by ECE or DK. In conclusion, ECE or DK attenuated Dexa-induced muscle atrophy by decreasing NLRP3 inflammasome formation and pyroptosis.     

Modeling the effect of γ-irradiation on reducing total bacterial populations in <Emphasis Type="Italic">gochujang</Emphasis> intended for consumption by astronauts in space programs

This study modeled the effect of γ-irradiation on reducing bacterial populations in space gochujang (Korean red pepper paste). The gochujang samples were γ-irradiated at 0, 5, 10, 15, and 20 kGy, and stored under accelerated storage condition (35°C for 10 days). During storage, total bacterial populations in gochujang samples were enumerated on plate count agar (PCA) on day 0, 1, 3, 5, 7, and 10. To calculate maximum specific growth rate (μ_max; log CFU/g/day), lag phase duration (day), low asymptote (Y ₀; log CFU/g), upper asymptote (Y _max; log CFU/g), and surviving cell counts recovered with PCA were fitted to the Baranyi equation. The parameters then were further expressed as a function of irradiation dose. Total bacterial populations in gochujang were decreased to below detection limit (1 log CFU/g) after irradiation (5–20 kGy). The samples irradiated at 5, 10, and 15 kGy then had bacterial cell recovery, but no growth was observed in 20 kGy irradiated samples during accelerated storage. After validation of models, acceptable model performances (B factor=1.15, A factor=1.29, RMSE=1.044, R ²=0.862) were observed. These results indicate that the developed models may be useful in predicting irradiation doses to produce space gochujang.     

Identification of an emulsifier and conditions for preparing stable nanoemulsions containing the antioxidant astaxanthin

In this study, oil-in-water nanoemulsions of astaxanthin were prepared by high-pressure homogenization. The influence of emulsifying conditions including emulsifier type, concentration, passing time, astaxanthin concentration and coantioxidants were optimized. The stabilities of nanoemulsions were measured using zetasizer, FF-SEM, TEM, colorimeter and particle size analyzer. The mean diameter of the dispersed particles containing astaxanthin ranged from 160 to 190 nm. The size distribution was unimodal and extended from 100 to 200 nm. The nanoemulsions prepared with glyceryl citrate/lactate/linoleate/oleate (glyceryl ester) had smaller particle size and narrower size distribution than the emulsion prepared with hydrogenated lecithin. Stable incorporation of astaxanthin in nanoemulsion was performed and checked using HPLC, FF-SEM and TEM. The nanoemulsion was not significantly affected during storage under light and thermal condition for one month indicating that the nanoemulsion had a zeta potential of less than -41 mV, indicating a stable colloid.     

Structural optimization of a Cu(In,Ga)Se2 thin film solar cell using numerical simulation and design of experiment techniques

The structural optimization for a thin film solar cell module based on Cu(In,Ga)Se₂ is investigated through numerical simulation and sequential statistical analyses. First, an equivalent numerical model for solar cells is constructed with an electrical circuit consisting of large area diodes and analysis using finite element analysis (FEA). A good agreement in performance characteristic curves between the developed numerical model and practical solar cells is obtained after performing parameter adjustments. To maximize the light conversion efficiency, an optimization technique using the design of experiment (DOE) of orthogonal arrays is employed. The programmed block diagram is used to calculate electric potentials inside solar cell layers and the associated solar performances. Statistical analysis of variance (ANOVA) and F-test are used to discover the dominant design variables (DVs) which are more important on solar cell performances. The second order regression model which relates dominant DVs with solar cell efficiency is mathematically obtained by the employment of response surface model (RSM) and graphically described by the equipotential contour plots.     

E‐Band Wideband MMIC Receiver Using 0.1 µm GaAs pHEMT Process

In this paper, the implementations of a 0.1 µm gallium arsenide (GaAs) pseudomorphic high electron mobility transistor process for a low noise amplifier (LNA), a subharmonically pumped (SHP) mixer, and a single‐chip receiver for 70/80 GHz point‐to‐point communications are presented. To obtain high‐gain performance and good flatness for a 15 GHz (71 GHz to 86 GHz) wideband LNA, a five‐stage input/output port transmission line matching method is used. To decrease the package loss and cost, 2nd and 4th SHP mixers were designed. From the measured results, the five‐stage LNA shows a gain of 23 dB and a noise figure of 4.5 dB. The 2nd and 4th SHP mixers show conversion losses of 12 dB and 17 dB and input P1dB of –1.5 dBm to 1.5 dBm. Finally, a single‐chip receiver based on the 4th SHP mixer shows a gain of 6 dB, a noise figure of 6 dB, and an input P1dB of –21 dBm.     

The application of photo-coupler for frost detecting in an air-source heat pump

This experimental study is carried out to investigate reliability and effectiveness of a new method of using photo-coupler for detecting frost formation in an air source heat pump, and further to determine the most efficient initiation point of the defrost cycle. This new method of using photo-coupler as a frost sensing device is evaluated by comparing its performance with conventional time control defrost system in which defrost cycle is set to start at predetermined interval, e.g. about at every 1–1.5 h. Results indicate that overall heating capacity of photo-coupler detection method (case IV) is 5.5% higher than that of time control method. It is also shown that for maximum efficiency the defrost cycle must be initiated before the frost build-up area exceeds 45% of total front surface of the outdoor coil.     

Comparison of the quality and storage stability of salmon packaged in various retort pouches

The effect of thin metal oxide coated barrier materials on the quality of shelf stable salmon was investigated. Four different retort pouch structures were used: Cast polypropylene (CPP); polyethylene terephthalate (PET)/silicon oxide-coated nylon/CPP (SIOX); Aluminum oxide-coated PET/nylon/CPP (ALOX); PET/aluminum foil/CPP (FOIL). To determine the amount of lipid oxidation in the salmon, thiobarbituric acid reactive substance (TBARS) was measured. Salmon packaged in SIOX pouches had higher TBARS value, 43.53 mili-extinction/g, than salmon packaged in FOIL pouches, 37.06 mili-extinction/g, after 8 weeks of storage. A multiple comparisons test was used to evaluate the sensory characteristics of the salmon. Salmon packaged in SIOX pouches had less acceptability, 4.11, than salmon packaged in FOIL pouches, 5.44, after week 8. Conversely, salmon packaged in ALOX pouches had similar sensory and TBARS value with salmon packaged in FOIL pouches. The barrier properties of each pouch material were also investigated. Oxygen permeability (OP, g μm/m² day kPa) of SIOX increased from 0.88 to 10.55 after retort processing. SIOX had an OP of 10.94 at week 8 while ALOX and FOIL had 0.51 and 0.47 of OP, respectively. Overall, shelf stable salmon packaged in ALOX had a shelf life comparable to salmon packaged in a traditional FOIL pouch material, while salmon packaged in SIOX had a significantly lower shelf life then either ALOX or FOIL.