• Korean Journal of Food Science and Technology
• /
• v.27 no.5
• /
• pp.783-788
• /
• 1995

Cooked rices were frozen at four different rates(3, 5, 7 and 12 hr) of maximum ice crystal formation zone and stored at $-20^{\circ}C\;and\;-70^{\circ}C$ for 3 months. Freezing rate, storage temperature and storage period all affected the degree of retrogradation of cooked rice. As the maximum ice crystal formation zone increased from 3 hrs to 12 hrs, the degree of retrogradation of cooked rice increased from 14.9% to 40.0%. Further retrogradation occurred during the freezing storage and cooked rice stored at $-20^{\circ}C$ retrograded faster than that held at $-70^{\circ}C$. The hardness and adhesiveness of frozen cooked rice thawed in $40^{\circ}C$ water were measured. Hardness of the frozen cooked rice was higher than that of non-frozen sample and was higher at lower freezing rate. However, the hardness of cooked rice decreased after 3 months of storage. On the other hand, the adhesiveness decreased during the freezing processing, and adhesiveness decreased more rapidly at a higher freezing rate. However, the adhesiveness of cooked rice increased after 3 months of the storage, and the level of decrease was higher at $-70^{\circ}C$ than at $-20^{\circ}C$. After 3 months of storage, ice crystal size of frozen cooked rice became larger by recrystalization than that of frozen sample prior to storage. Microstructure of cooked rice was damaged by ice crystal formation and its growth when observed by scanning electron microscope.

• Korean Journal of Food Science and Technology
• /
• v.28 no.2
• /
• pp.305-310
• /
• 1996

The degrees of retrogradation (DR) for 50% rice flour gels kept at $4^{\circ}C$ and $20^{\circ}C$ for the 6-day storage period at 0.5, 1.0 and 2.0% (w/w, on dry weight basis) levels of lipid additives (sucrose fatty acid ester, SE1670; soybean oil) were measured by ${\alpha}$-amylase-iodine method, differential scanning calorimetry (DSC) and X-ray diffractometry. The DRs were higher in rice flour gels stored at $4^{\circ}C$ than those stored at $20^{\circ}C$. The sucrose fatty acid ester and soybean oil reduced the retrogradation of rice flour gels, but the effect was higher in samples stored for 1 day. The DR decreased more effectively in the addition of SE1670 than that of soybean oil In case of SE1670, the change of enthalpy by DSC showed similar patterns with the degree of retrogradation by ${\alpha}$-amylase method; however, it was not the case for soybean oil. The intensity of peak at $2{\theta}=16.7^{\circ}$ in X-ray diffraction pattern was reduced with lipid additives but it was not clear.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.36 no.10
• /
• pp.1320-1325
• /
• 2007

Retarding retrogradation of a Korean rice cake (Karedduk) added with carbohydrate materials after $0{\sim}30hrs$ of storage at $5^{\circ}C$ were investigated by Avrami equation using textural characteristics. Carbohydrate materials such as powdered sugar, trehalose, fructooligosaccharide (95%), isomalto, healtholigo, and galactooligo-saccharide (50%) were added in 0, 1, 5 or 10% levels on dry rice flour. In the amylogram, the breakdown (P-H) and consistency (C-H) for Karedduk added with carbohydrate materials were lower than those of the control. Decrease in the Avrami exponent (n) and increase in the time constant (1/k) of Karedduuk added with carbohydrate materials during storage determined by Avrami equation were important comparison factors to the control in terms of retrogradation rate analysis. The Aurami exponent (n) for control, fructooligosaccharide (95%) 10% and healtholigo 1% addition were 2.415, 1.977 and 3.297, respectively. The time constant (1/k) for fructooligosaccharide (95%) 5% and healtholigo 1% addition were lower than thecontrol. Lastly, Karedduk added with carbohydrate materials, except for fructooligosaccharide (95%) 5% and healtholigo 1% addition, was effective in retarding retrogradation.

• Korean Journal of Food Science and Technology
• /
• v.32 no.1
• /
• pp.140-146
• /
• 2000

The physicochemical properties, such as retrogradation, fat acidity and viscosity, on the pine nut's gruel at various contents of pine nut (0, 1, 3 and 5%) during storage at 4, 25 and $40^{\circ}C$ were investigated. The degree of retrogradation was increased rapidly at the initial storage stage. The lowest value (about 10%) of the degree of retrogradation was observed in the gruel sample containing 3% of pine nut. Also, the rate constant of retrogradation was showed the lowest value (0.0422) in the gruel containing 3% of pine nut regardless of storage temperatures. The fat acidity was showed the lower value than 30 mg KOH in all samples. The viscosity increasing velocity(RVU/min) between holding strength and final viscosity was decreased as the pine nut's content was increased. However, it was not affected by the storage temperatures.

• Korean journal of food and cookery science
• /
• v.24 no.5
• /
• pp.636-644
• /
• 2008

The principal objective of this study was to assess the effects of hydrocolloids(xanthan gum, guar gum, sodium alginate, k-carrageenan, carboxy-methyl cellulose) on the suppression of retrogradation in the bread. The pasting properties of the doughs and the sensory properties were determined in the bread samples, to which xanthan gum, guar gum, sodium alginate, k-carrageenan, and CMC, were added at different ratios(0.2%, 0.6%, 1%). CMC and k-carrageenan with 0.6% level were selected for the further retrogradation studies. Changes in the firmness of the bread samples at room temperature for 15 days were assessed using a texture analyzer, and the type of retrogradation was calculated via the Avrami equation. The thermal properties of the samples were also determined via differential scanning calorimetry (DSC). The addition of hydrocolloids was shown to increase the viscosities of the doughs. Setback and breakdown viscosity were reduced significantly via the addition of CMC(0.6%, 1%), xanthan gum(1%), and k-carrageenan(1%). Sensory hardness was significantly increased when 1% hydrocolloids were added. Our textural analysis showed that the addition of CMC reduced the firmness of the bread, whereas k-carrageenan didn't. However, the retrogradation rate was reduced via the addition of k-carrageenan, as was also demonstrated in the results of our DSC analysis.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.45 no.12
• /
• pp.1792-1798
• /
• 2016

This study investigated quality characteristics, antioxidant activities, and retarding retrogradation of Sulgidduck, traditional rice cake of Korea, prepared using rice flour added with 0%, 1%, 2%, 3%, and 4% pumpkin leaf powder. Moisture content of pumpkin leaf Sulgidduck showed a tendency to increase in the 1% and 2% added group but decrease in the 3% and 4% added group. pH level significantly increased (4.50~6.16) with an increase in content of pumpkin leaf powder (P<0.05). For color, as content of pumpkin leaf powder increased, L-value decreased and b-value increased. Hardness tended to increase with addition of pumpkin leaf powder except for the 1% added group. Springiness was not significantly different (P<0.05). Chewiness and adhesiveness increased according to addition level increase. Retarding retrogradation showed that the pumpkin leaf powder added group had a stronger effect compared to the control, whereas the 2% added group presented the most retarding retrogradation effect with the lowest Avrami exponent. Total phenols content and ABTS radical scavenging activity tended to increase as content of pumpkin leaf powder increased. Sensory properties by 7-point scale test showed that the 2% added group had the highest scores, whereas the 4% added group had the lowest scores. These results suggest that pumpkin leaf is considered as a good material to improve quality characteristics, antioxidant activities, and retarding retrogradation of Sulgidduck. The most appropriate proportion for the greatest effect of retarding retrogradation in Sulgidduck was considered to be 2%.

• Korean journal of food and cookery science
• /
• v.12 no.2
• /
• pp.186-192
• /
• 1996

Retrogradation of non-waxy rice (NWR) and waxy rice (WR) cakes (45% moisture) stored at 5$^{\circ}C$, $25^{\circ}C$ and -2$0^{\circ}C$ was studied by differential scanning calorimetry (DSC) and enzymatic ($\beta$-amylase-puuulanase) method. With DSC, endotherms did not appear with rice cakes stored at room ($25^{\circ}C$) and deep freezing (-2$0^{\circ}C$) temperatures but did with samples stored at low temperature (5$^{\circ}C$), showing accelerated retrogradation by low temperature. Onset temperature (To) and peak temperature (Tp) did not change under 14 days at 5$^{\circ}C$ but enthalpy values ($\Delta$H) increased rapidly within one day and increased steadily until 5th day of storage, then equilibrated. Higher $\Delta$H were obtained with WR cakes than NWR cakes. It was suggested that more amylopectin recrystallization occured with WR than NWR. Degrees of gelatinization of rice cakes determined by enzymatic method increased in the following order: 5$^{\circ}C$ < $25^{\circ}C$ < -2$0^{\circ}C$. In contrast with DSC results, dogrees of gelatinization of NWR cakes, were relatively lower than that of WR cakes. However, increased retrogradation extents (melting enthalpies) caused reduced enzyme susceptibilities to $\beta$-amylase-pullulanase system, among NWR or WR cakes stored at 5$^{\circ}C$. The degrees of retrogradation of rice cakes stored at 5$^{\circ}C$ were higher than those stored at $25^{\circ}C$ and -2$0^{\circ}C$ without regard to the kind of rice. The higher sensitivity of the enzymatic method was obtained than that of DSC method when the degrees of retrogradation of rice cakes were determined during storage under this experiment conditions.

• Korean journal of food and cookery science
• /
• v.18 no.4
• /
• pp.390-398
• /
• 2002

The purpose of this study was to select a cake ingredient acting as an emulsifier to retard the retrogradation of rice cake commercially available. For the purpose, Backsulgi, a traditional Korean rice cake, was prepared by adding various ingredients having high contents of lecithin such as raw soybean powder, parched soybean powder, soybean oil, egg yolk powder, and then the changes in the sensory and textural characteristics of the cakes were determined while storing them at the temperatures of 4$\^{C}$ and 20$\^{C}$ for 0, 1, 2 and 3 days. Based on the sensory evaluation, Backsulgi samples added with raw soybean flour were significantly different in roasted nutty smell, roasted nutty taste, softness, moistness, cohesiveness and overall quality compared with the control in the longer storage time at 20$\^{C}$.

• The Korean Journal of Food And Nutrition
• /
• v.11 no.4
• /
• pp.369-374
• /
• 1998

This study was conducted to investiagte influences of cold aged dough on the quality of bagutte. After 2 hours fementing, the dough was divided 2 parts and they were stored in the refrigirated adjusted 1∼-1$^{\circ}C$. The cold aging time was 24, 48 hours respectivley. After 2 hourse fermentation, the dough's pH was 5.45 and 24, 48 hours cold aged dough were 4.99, 4.81. During cold aging, the difference of pH was not significant. The main organic acids in the baguette were lactic acid, acetic acid and malic acid, Among these organic acids, the acetic acid was the largest quantity regardlessly in different fermentation and the cold aging acids, time. Right after baking, the enthalphy of all samples were almost same even thought in different cold aging time, but during different storage periods they showed the difference of retrogradation by the increase of the enthalphy. 24 hours cold aging baguette had the best taste, aroma and texture in bread's score sheet.

• The Korean Journal of Food And Nutrition
• /
• v.20 no.4
• /
• pp.427-432
• /
• 2007

The texture and descriptive sensory characteristics of a Korean rice cake(Karedduk) with added emulsifier were investigated after 2 and 24 hrs of storage at $5^{\circ}C$. The emulsifier, SP, was added at 0, 0.1, 0.5 and 1% levels to the dry rice flour. In the amylogram, the peak viscosity(P), hot paste viscosity(H) and cold paste viscosity(C) of the rice flour with added emulsifier were higher than those of the control. The texture property analysis by a Texture Analyzer revealed that the springiness, cohesiveness and adhesiveness of the Korean rice cake(Karedduk) with added emulsifier were similar to those of the control, while chewiness, gumminess and hardness were lower compared to the control. Also, the hardness by sensory characteristics was significantly different as compared to the control. Lastly, adding emulsifier to the Korean rice cake(Karedduk) was effective at retarding retrogradation.