• Preventive Nutrition and Food Science
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• v.9 no.2
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• pp.113-120
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• 2004

Selected microbiological and biochemical characteristics of the steeping process for the production of yukwa, a traditional Korean oil-puffed snack made of waxy rice, were investigated during steeping of waxy rice in water for 15 days. The lengthy steeping process was largely predominated by lactic acid bacteria (LAB), particularly, Lactobacillus and Leuconostoc. The predominat type of bacterium isolated was the Y26 strain tentatively identified as Lactobacillus plantarum. The titratable acidity of the steeping medium increased from 0.01 to 1.13%, in parallel with the decrease in pH ranging from 6.3 to 4.2 as the steeping period increased from 0 to 15 days. A high amount of lactic acid and to a much lesser extent, butyric acid, acetic acid, propionic acid, and succinic acid were detected during the steeping process. The amount of reducing sugars in the steeping medium increased from 0.61 to 10.43 mg/mL, whereas sucrose decreased from 0.46 mg% to an undetectable level. Starch degradation products including glucose, maltose and oligosaccharides ranging G3-G7 were not initially noticed, but their content increased during the steeping process until completion. However, no oligosaccharides larger than G8 were detected in the steeping medium. The activities of $\alpha$-amylase, $\beta$-amylase and protease in the steeping medium of waxy rice tended to rise increase with time during the steeping process. From these results, the lengthy steeping process in yukwa production can be characterized as the spontaneous fermentation, dominated by lactic acid bacteria, which is a necessary process for inducing biochemical modification of waxy rice.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.1
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• pp.17-24
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• 1997

The effects of steeping on the physicochemical and gelatinization characteristics of glutinous rice flour and its starch were studied. Steeping conditions were 1 day at 25"C,7 days at 2iC and 7 days at 35"C. Crude protein, lipid and ash content were decreased br steeping. It was observed with scanning electron microscopy that endosperm cell wall of glutinous rice flour was diminished by steeping. Although morphology of the glutinous rice starch granules was not affected, the size was decreased by steeping. Density and water binding capacity(WBC) of glutinous rice flour and its starch were changed by steeping. X-ray diffraction pattern of glutinous rice starch was A type and was not affected by steeping. Swelling power of glutinous rice flour and its starch was increased but solubility was decreased by steeping. In Brabender amylographic examination, peak viscosity of untreated glutinous rice flour was very low and increased enormously by steeping resulting in the similar Brabender viscosity pattern to its starch. The gelatinization temperature examined by X-ray diffractometry was lowered by steeping. And the degree of gelatinization under the conclusion temperature increased with increasing of steeping Period and temperature.mperature.

• Korean Journal of Food Science and Technology
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• v.25 no.5
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• pp.535-540
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• 1993

Effects of steeping of waxy rice in water at $20^{\circ}C$ for 6 or 30 hr on physicochemical properties of rice flour and molecular structure of starch were examined. pH of the steep water was decreased upon steeping. The lightness of the flour was gradually increased, while redness and yellowness were decreased as steeping time increased. The protein content was linearly decreased during steeping period. The fat content was sharply decreased from 18hr of steeping. The ash content rapidly decreased up to 12hr of steeping. The water-binding capacity was increased up to 12hr of steeping and decreased thereafter. The swelling power at $80^{\circ}C$ was consistently increased during steeping period. The amylograph peak viscosity showed a linear relationship with the steeping time. The molecular structure of starch was not affected by steeping.

• Korean Journal of Food Science and Technology
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• v.28 no.6
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• pp.1026-1032
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• 1996

The effects of steeping temperature $(7^{\circ},\;15^{\circ},\;20^{\circ}\;and\;30^{\circ}C)$ and steeping time $(2{\sim}14\;hr)$ on the physicochemical properties of milled rice (variety; Chucheongbyeo) were investigated. The pH of the steep water decreased as the steeping time increased, which was more pronounced at higher steeping temperature. The solid loss was about 4.0% during steeping. The contents of protein, fat and ash decreased during steeping, which was greater at elevated temperature. The lightness of rice was slightly increased, and the yellowness was decreased upon steeping. The water-binding capacity of rice was increased during steeping at above $15^{\circ}C$. The slight increase of the swelling power of rice at $80^{\circ}C$ was observed upon steeping. The maximum wavelengh for the rice flour-iodine complex was moved to a higher wavelengh, but X-ray diffraction patterns remained constant regardless the steeping conditions. The pasting properties of rice flour (10%) by amylograph indicated that the peak viscosity increased as the steeping time was increased at all steeping temperatures. The steeping resulted in the greater breakdown and the 1ower setback. The log peak viscosity showed a linear relationship with the steeping time. The activation energy and $Q_{10}$ value for the visciosity increase rate was 2, 320 cal/mole and 1.14, respectively.

• Korean Journal of Food Science and Technology
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• v.25 no.1
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• pp.86-87
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• 1993

The steeping of waxy rice in water at $20^{\circ}C$ for 12 hr resulted in the decrease of protein, crude fat and ash contents. Water-binding capacity and swelling power (at $80^{\circ}C$) of waxy rice flour increased upon steeping. Maximum viscosity of waxy rice flour in 0.19 N sodium hydroxide solution was increased up to 6 hr steeping and decreased thereafter. The amylograph indices increased as the steeping time increased. The degree of changes in properties during steeping was different between two waxy rice cultivars.

• Korean journal of food and cookery science
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• v.11 no.2
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• pp.104-107
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• 1995

This study was attempted to simplify the complex steeping mechanism and propose the scientific approach of microorganism. As Enzyme activity showed that as steeping hours increase, the а-amylase activity increased. Most commonly microorganisms in steeping liquid were Corynebacter spp., Candida spp. and Lactobacillus spp. According to results, steeping acidifies the character of glutinous rice, affec-ting the starch's n-amylase and bring about component's changes. As Candide spp. and Lactobaillus spp. of the steeping liquid increase, the character of liquid is acidifying.

• Korean journal of food and cookery science
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• v.14 no.3
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• pp.213-218
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• 1998

The changes in gelatinization patterns of potato were investigated while steeping in water for 7 days at 30${\pm}$1$^{\circ}C$. The transmittance of 0.1% starch suspension was increased rapidly from 60$^{\circ}C$ in raw starch and the starch steeped for 2 days, and increased rapidly from 65$^{\circ}C$ in the starch steeped for 4 and 6 days. As the steeping period increased, the transmittance was decreased at above condition. The gelatinization temperature of the starch measured by differential scanning calorimetry was increased from 62.79$^{\circ}C$ to 63.72$^{\circ}C$ as the steeping period increased. The gelatinization enthalpy reached the maximum in the starch steeped for 4 days. By amylograph, the initial gelatinization temperature was increased from 66$^{\circ}C$ to 84$^{\circ}C$ as the steeping period increased. Peak viscosity was decreased during steeping and the starch steeped for 5 days had no peak viscosity. Peak height after cooling to 50$^{\circ}C$ was increased up to the 4th day and began to decrease. As the steeping period increased, there was much loss of birefringence at higher temperature. The crystallinity by X-ray diffraction disappeared from 65$^{\circ}C$.

• Food Science and Preservation
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• v.5 no.4
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• pp.368-373
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• 1998

The effects of steeping and washing were investigated in the physicochemical properties of acorn flour. The contents of crude protein, ash and total phenol of acm flour were gradually decreased with the steeping days and washing times. However, the contents of crude fat and dietary fiber were little different. The more steeping days and/or washing times became large, the more the color of acorn flour became light. Swelling power was enhanced by increasing of steeping days and washing times but solubility was some decreased Water binding capacity was decreased and intrinsic viscosity was increased with the increased steeping days and washing times. Washing times were more influential than steeping days to those changes.

• Korean Journal of Food Science and Technology
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• v.26 no.5
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• pp.638-643
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• 1994

Gelatinization and retrogradation properties of modified starches which were prepared by steeping sweet potato at $40^{\circ}C$ for 2, 4, 7 and 10 days were investigated. The peak temperature of gelatinization and enthalpy of untreated starch by DSC were $53.9^{\circ}C\;and\;1.32\;cal/g$, respectively, but those of modified starch were increased by steeping. In gelatinization by alkali, starches with 2, 4 and 7 day steeping showed higher viscosities than untreated starch, whereas the viscosities of starches with 10 day steeping decreased. The clarities in paste decreased during storage in all starches and decreased in starches with steeping. The degrees of retrogradation by ${\alpha}-amylase-iodine$ method were higher in starches with steeping than untreated starch. The enthalpy of retrograded starches by DSC increased by steeping except 4 day steeping starch. The sweet potato extract containing sugar inhibited the retrogradation of starch paste and the degree were higher in residual starches than in untreated starch.

• Korean Journal of Food Science and Technology
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• v.34 no.4
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• pp.597-603
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• 2002

The analysis of traditional process for a Korean puffed rice snack (Yukwa) is needed to develop an advanced process for Yukwa-making. Steeping and punching (Koarichigi) processes, consume time and labor in Yukwa-making, were analyzed on this study. Steeping of waxy rice at $15^{\circ}C$ for 3 days was required to equilibrate moisture absorption in waxy rice kernel. However, steeping for more than 6 days was required soft texture and small air cell distribution of Yukwa. Protein content at pericarp on endosperm of waxy rice kernel was decreased and starch granule was damaged during steeping. RVA paste viscosity was the highest at 6 day steeping after than decreased. Expansion ratio of Yukwa was increased with the increase in steeping time. Air bubbles in dough after punching were uniformly distributed and kneading energy input was decreased with the increase in steeping time. Soft texture, unique texture of Yukwa could be controlled by controlling steeping time and kneading energy input during punching process.