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Abstract The effects of matcha (MAT), tea polyphenols (TP) and catechin (CAT) on rice cakes during storage for 180 days at 4 °C and 25 °C were evaluated using textural properties, water migration, XRD spectra and in vitro starch digestibility. Polyphenolic compounds, especially TP and CAT, primarily retarded the starch retrogradation of rice cakes by interacting with starch chains, which lowered the content of bonded water, as indicated by water migration and a lower relative crystallinity. The reduction of hardness and increase of adhesiveness was attributed to inhibition of starch chain cross-linking by the polyphenolic compounds (CAT and TP in particular). The polyphenolic compounds synergistically affected starch re-association at a high storage temperature (25 °C) and decreased the variance of rice cake quality caused by starch retrogradation during storage at 4 °C. The starch digestion of rice cakes was inhibited by polyphenolic compounds, especially CAT, which concomitantly increased the content of resistant starch. Furthermore, polyphenolic compounds reduced the changes of various properties which caused the stabilization of rice cake quality during long-term storage. Our study could provide an alternative for improving rice cake quality affected by storage.

The fermented rice cake is a unique traditional product of Thailand called “Khao-Maak,” which is usually made from white or black glutinous rice. Because the germinated black glutinous rice contains high levels of antioxidants and γ-aminobutyric acid (GABA), as well as epidermis with prebiotic potential, it was used in this study to increase the health benefits and functional values of Khao-Maak. Moreover, the probiotic yeast, Saccharomyces boulardii, was added during fermentation to ensure the synbiotic characteristics. In vitro gastrointestinal tests showed that the developed product had a higher yeast survival rate (97.10 ± 0.87%) compared to the control (< 70%). The prebiotic activity score (PAS) also showed a positive value of 1.81 ± 0.15, indicating its prebiotic characteristics. However, as the germinated rice is hard to digest, its use slowed down the fermentation process. Therefore, the cellulase and amylase each were added at 10 U/g to increase the fermentation rate while resulting in an acceptable score from the consumers. The functional value analysis showed that the developed product contained antioxidants such as anthocyanins, flavonoids, and GABA, each not less than 30 mg per 100 g-product. The shelf life study revealed that the product could be stored at 4 °C for 10 days while maintaining functional values within product specifications and meeting community product standards. This study demonstrated the possibility of increasing health benefits and functional values of rice products, as well as the effective use of food-grade enzymes to improve the productivity and quality of fermented foods.

In the rice processing industry, wastewater is an inevitable by-product of rice washing. To increase the utilization of washed rice water (WRW), seven types of fermented washed rice water (FWRW) were prepared using lactic acid bacteria (LAB) and carbohydrate hydrolase. The total concentration of small maltooligosaccharides (MOSs) in the amyloglucosidase (AMG) treatment groups was about ten times higher than in the untreated groups. After 6 h of fermentation, six of the seven FWRW samples reached a pH of 4 due to the increased concentration of organic acids and could, therefore, be used as food acidity regulators. To confirm the applicability of FWRW, the traditional Korean rice cake garaetteok was prepared with FWRW and stored at 4 °C for 5 days. A texture profile analysis (TPA) revealed that the hardness of garaetteok treated with FWRW was significantly lower than that of untreated garaetteok following storage. Differential scanning calorimetry (DSC) showed that FWRW retarded the retrogradation of garaetteok during storage. The addition of FWRW using Lactobacillus reuteri with an AMG group was particularly effective for inhibiting microbial activity in garaetteok during storage. These results suggest that FWRW using AMG-added L. reuteri can be used as a novel food additive for improving the quality of traditional Korean starch foods and could also reduce the volume of waste WRW.

Retrogradation properties and kinetics of rice cakes with the addition of glycerol (GLY) and sucrose fatty acid ester (SE) were investigated. In hardness, both rice cakes with glycerol (RGLY) and rice cakes with sucrose fatty acid ester (RSE) showed lower initial hardening compared with the control for up to 5 days. X-ray diffraction (XRD) pattern of RSE showed a B+V-type pattern, and the relative crystallinity showed that GLY and SE lowered the initial and final crystallization of rice cake. Both GLY and SE affected the retrogradation enthalpy, glass transition temperature, and ice melting enthalpy in differential scanning calorimeter (DSC). However, 1H NMR relaxation time (T2) of rice cake decreased regardless of additives. From these results, the addition of glycerol and sucrose stearate inhibits the retrogradation process of rice cakes, which will solve industrial problems. Applying the Avrami equation for retrogradation kinetics of rice cake was suitable in XRD and DSC with high coefficient of determination (0.9 < R2). Meanwhile, the other retrogradation index improved the R2 when the exponential rise to maximum equation was used. This suggests that there is an alternative of Avrami equation to predict the retrogradation.

The halal food market is steadily increasing. The use of alcohol for any reason is strictly prohibited in halal foods; however, ethanol is widely used as a preservative for commercial rice cakes (tteok). The purpose of this study was to investigate the use of natural substances as alternative preservatives for rice cakes. Four different solutions were tested: distilled water (control), ethanol, grapefruit seed extract (GSE), and a mixture of citric extracts and organic acids (MCO). We investigated the total plate count (TPC), yeast and mold counts, color, texture profile assays (TPA), and sensory evaluation. Significant reductions of 3.65 log CFU were observed in TPC in rice cake treated with MCO solution after 28 days of storage. However, mold and yeast counts were only reduced by ethanol treatment. Among the physical texture properties analysis, hardness was maintained for the 28 days in all samples. The total color difference values (ΔE) revealed no significant color changes in any rice cake compared to the controls. The ethanol-treated rice cake scored the lowest for overall preference and desired hardness.

The purpose of this study was to apply a powdered β-carotene-loaded emulsion to a real food product, Korean traditional rice cakes (Garaedduk). β-Carotene was incorporated into the oil phase of a sodium caseinate-stabilized emulsion. Emulsion powder containing β-carotene was prepared using freeze-drying, and maltodextrin and gum arabic were used as wall materials. Oil/protein/maltodextrin weight ratios of 3:1:2 and 3:1:5 (core-to-wall ratios of 1:1 and 1:2) were used, and gum arabic was added by replacing the amount of maltodextrin for 0.1%, 0.2%, and 0.5% w/w. Manufactured emulsion powders prepared with wall material at a core-to-wall ratio of 1:2 remained stable after reconstitution in terms of particle diameter and ζ-potential. The encapsulation efficiency of the emulsion powder increased by 90% in the presence of maltodextrin at a core-to-wall ratio of 1:2. Garaedduk containing the emulsion powder was then manufactured and it was confirmed that β-carotene was not degraded during the manufacturing process of Garaedduk by using HPLC. The results from this study may be useful for rational designing of functional foods with lipophilic bioactive materials.

This study aimed to control characteristics of fermented rice products by using functional fungi and yeasts isolated from traditional rice cake starters in Thailand. Amylolytic fungi, amylolytic yeasts, alcoholic yeasts and aromatic yeasts were isolated from rice cake starters through different isolation protocols. Among the protocols tested, the enrichment in rice cake fermentation prior to isolation was the most suitable protocol for isolation of amylolytic fungi from all rice cake starters. While the enrichment in submerged fermentation prior to isolation could increase the numbers of yeast isolates. The selected amylolytic fungus and amylolytic yeast were identified as Rhizopus oryzae F63S and Saccharomycopsis fibuligera Y71R, respectively. The yeast with high production of ethanol and aromatic ester was identified as Pichia anomala Y11E. Fermented rice cakes with different characteristics were prepared using various combinations of fungi and yeast. The combination of R. oryzae F63S with S. fibuligera Y71R exhibited strong amylolytic activity and produced an extra sweet fermented rice cake. While the combination of R. oryzae F63S with P. anomala Y11E showed higher alcoholic and aromatic flavors. Moreover, the pure yeast P. anomala Y11E added with commercial amylase has been proven as an innovative starter for fast fermentation. This concept may contribute greatly to the further development of fermented food with desired properties at industrial level.

In modern society, interest in health is increasing, and more consumers are taking care of their health due to COVID-19. As a result, immunity enhancement and antioxidant foods help to promote health, and the intake rate is increasing. Therefore, the purpose of this study was to investigate quality characteristics and antioxidant activity by adding 0%, 3%, 6%, 9% and 12% pistachios to rice cake, a traditional Korean food. The moisture content and pH decreased as the amount of pistachio added and the chromaticity L and a values tended to decrease, but the b values increased. It was confirmed that the polyphenol, ABTS a DPPH significantly increased as the amount of pistachio added increased. As a result of confirming the functionality and overall preference, it is suggested that the 9% content is the best, and this experiment is expected to improve the quality of rice cake and improve the nutritional balance, so that it can become an antioxidant functional food. As far as we know, it is the first study to prove that pistachios and rice cakes are combined, suggesting that rice cakes with added pistachios, a physiologically active substance, are healthful foods.

Hardening of cheese is one of major issues that degrade the quality of Home Meal Replacement (HMR) foods containing cheese such as Cheese-ddukbokki rice cake (CD, stir-fried rice cakes with shredded cheese). The quality of cheese, such as pH, proteolytic, and flavor properties, depends on various lactic acid bacteria (LAB) used in cheese fermentation. The hardening of cheese is also caused by LAB. In this study, various LAB strains were isolated from CD samples that showed rapid hardening. The correlation of LAB with the hardening of cheese was investigated. Seven of the CD samples with different manufacturing dates were collected and tested for hardening properties of cheese. Among them, strong-hardening of cheese was confirmed for two samples and weak-hardening was confirmed for one sample. All LAB in two strong-hardening samples and 40% of LAB in one weak-hardening sample were identified as Latilactobacilluscurvatus. On the other hand, most LAB in normal cheese samples were identified as Leuconostoc mesenteroides and Lactobacillus casei. We prepared cheese samples in which L. curvatus (LC-CD) and L. mesenteroides (LM-CD) were most dominant, respectively. Each CD made of the prepared cheese was subjected to quality test for 50 days at 10 °C. Hardening of cheese with LC-CD dominant appeared at 30 days. However, hardening of cheese with LM-CD dominant did not appear until 50 days. The pH of the LC-CD was 5.18 ± 0.04 at 30 days, lower than that of LM-CD. The proteolytic activity of LC-CD sample was 2993.67 ± 246.17 units/g, higher than that of LM-CD sample (1421.67 ± 174.5 units/g). These results indicate that high acid production and high protease activity of L. curvatus might have caused hardening of cheese.