• Korean Journal of Food Science and Technology
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• v.25 no.1
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• pp.1-8
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• 1993

Extruded defatted soy flour (DSF) with twin screw extruder was compared with steam treated DSF for soy sauce fermentation. Independent variables of response surface methodology (RSM) for extrusion were barrel temperature $(145{\sim}165^{\circ}C)$, feed moisture content $(25{\sim}35%)$, and feed rate $(20{\sim}30\;kg/hr)$. Extrusion conditions for production of the extrudates having highest water absorption capacity, lowest bulk density and highest expansion ratio were obtained by regression analysis of each dependent variable. Electron photomicrographs revealed significant increase of porosity inside the koji made from extruded DSF. Therefore, growth of fungi inside the koji made from extrudates of DSF was accelerated to achieve higher activities of protease, ${\alpha}-amylase$, and glucoamylase compared to the koji made from steamed DSF. Although amino acid composition of soy sauces prepared from two different DSF did not show any significant difference, the content of free amino acids in soluble nitrogen compounds was higher $(13%{\pm}2)$ in soy sauce made from extruded SDF. During the whole period of fermentation color of soy sauce made from extrudates of DSF was darker. Sensory evaluation did not reveal any serious off-odor and off-taste in the soy sauce fermented from extruded DSF.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.52-58
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• 2023

With the increasing awareness of the importance of carbon neutrality in response to global climate change, the utilization of hydrogen as a carbon-free fuel source is also growing. Hydrogen is commonly used in fuel cells (FC), but it can also be utilized in internal combustion engines (ICE) that are based on combustion. Particularly, ICEs that already have established infrastructure for production and supply can greatly contribute to the expansion of hydrogen energy utilization when it becomes difficult to rely solely on fuel cells or expand their infrastructure. However, a disadvantage of utilizing hydrogen through combustion is the potential generation of nitrogen oxides (NOx), which are harmful emissions formed when nitrogen in the air reacts with oxygen at high temperatures. In particular, for the EURO-7 exhaust regulation, which includes cold start operation, efforts to reduce exhaust emissions during the warm-up process are required. Therefore, in this study, the characteristics of nitrogen oxides and fuel consumption were investigated during the warm-up process of cooling water from room temperature to 88℃ using a 2-liter direct injection spark ignition (SI) engine fueled with hydrogen. One advantage of hydrogen, compared to conventional fuels like gasoline, natural gas, and liquefied petroleum gas (LPG), is its wide flammable range, which allows for sparser control of the excessive air ratio. In this study, the excessive air ratio was varied as 1.6/1.8/2.0 during the warm-up process, and the results were analyzed. The experimental results show that as the excessive air ratio becomes sparser during warm-up, the emission of nitrogen oxides per unit time decreases, and the thermal efficiency relatively increases. However, as the time required to reach the final temperature becomes longer, the cumulative emissions and fuel consumption may worsen.