Abstract
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1. Revising the micro-brewery brewing processes according to more than 50 % rice addition
- First of all, the brewing with adde...
1. Revising the micro-brewery brewing processes according to more than 50 % rice addition
- First of all, the brewing with added more than 50% rice was analyzed in terms of the process efficiency and the qualities of the intermediate and final products. The efficiencies in saccharification and fermentation were lowered with increase in rice contents. The qualities of beer were degraded by changing to dark yellow, having more bitterness, and loosing foam stability. In filtration process, the filter cake formation increased with rice contents. Eventually, the rice addition in brewing turn out to worsen both product and processing qualities, indicating needs to develop some means to dissolve the derived problems. Accordingly, we develop several methods and equipments as follows.
- Amylase was used in mashing process to compensate for the decreased amount of malt due to the rice addition. This treatment was found to be effective to enhance both product and processing qualities. Protease was used in mashing process to make the yeast required protein more available by breaking down the rice contained protein, because malt has more protein for yeast growth than rice. This treatment was found to not be effective except increasing the beer foam stability. Several amino acids were used in fermentation process to make up for some particular amino acids, which are contained less in rice than barly. The results were quite successful to enhance the qualities, which was pronounced in the glutamic acid treatment.
- By increasing rice addition, filtration (lautering) was clogged due to increase in filter cake out of rice paste. We created a rotating arm with 6 mixing blades which can be arranged by different angles to the arm. With increase in rotation speed, the filtration was facilitated, but after an optimum speed, it got worse. With decrease in angle between blade and arm, the filtration got better, but there was also an optimum condition. Eventually, the newly designed device was proven to overcome some deficiency of performance due to rice addition.
- As another solution for the filtration problem, we used paddy rice instead of polished rice. We intended to take advantage of the husk in the paddy rice as a potential filtering aid. The rice husk filter aid was quite effective to enhance prevention of clogging.
- By increasing rice addition, the turbitity of extracted wort from lautering increased, and therefore it was necessary to remove the impurities from the wort. We devised a novel whirlpool equiped with automatic distribution system. In the system, four inlets were placed at different height, and they opened or closed according to 3 cases. In case 1, only one of the four inlets was kept open. In case 2, the difference from the case 1 was the open inlet varied with the liquid level in whirlpool. In case 3, the inlets opened one by one, and all open at last. The case 2 was the best to get more sedimented mass. In addition, a potential use of centrifuge was tested, and found to be really effective.
2. Development of various rice beers and investigation of their volatile profies and antioxidant activity
- Analysis of volatile copounds found in rice beers The volatile profiles of various beers were prepared using SAFE (Solvent Assistant Flavor Evaporation) and GC-MS(Gas chromatography-mass spectrometry). Studied beers included commercial beer, brewed beer, 50% or 70% rice beer, 50% unhulled rice beer and sansuyu, hwangeum, and ogapy mixed beers. With increasing rice into beer brewing the amount of volatile compounds in the beers was reduced. The sum of peak area ratio of 50% unhulled rice beer (4.5296) was 62% compared with that of brewed beer (7.2995). However, various lactones such as $\gamma$-hexalactone, $\gamma$
- nonalactone and $\gamma$-decalactone which were not detected in brewed beer were analyzed in 50% unhulled rice beer. In rice beers total amount of volatiles were decreased but more diverse volatile compounds could be found.
- Antixodant activity of rice beers The antioxidant activity of brewed beer and rice beers was measured using DPPH radical scavenging assay. The antioxidant activity of brewed beer was 74.6% and higher than that of rice beers. Those of 50% and 70% rice beer were 17.6% and 7.7%, respectively. The antioxidant activity of unhulled rice beer was measured by two assay, DPPH radical scavenging assay and ABTS radical cation scavenging assay. In DPPH radical scavenging assay the antioxidant activity of 50% unhulled rice beer (65.5%) was lower than that of brewed beer (82%) but higher than that of commercial bottled beer (63.8%). In ABTS radical cation scavenging assay the antioxidant activity of 50% unhulled rice beer (55.2%) was lower than that of brewed beer (87.5%) as well as that of commercial bottled beer (60.4%). In conclusion the antioxidant activity of unhulled rice beer was lower than that of brewed beer but almost same as that of commercial bottled beer.
- Development of various medicinal plant added rice beers Various medicinal plant such as sansuyu, hwangeum, and ogapy added rice beers were developed by mixing medicinal plant extracts into 50% unhulled rice beer. The extract was prepared by extracting 150 g of plants at ${80^{\circ}C}$ with 3 L water for 3 hours. The concentration of the extract in beer was adjusted 5% and 10%. The amount of volatiles found in medicinal plant added rice beer increased compared with that of unhulled rice beer. Sum of peak area ratio of unhulled rice beer was 4.5296 but those of 5% ogapy, 10% ogapy, 5% hwangeum, 10% hwangeum, 5% sansuyu and 10% sansuyu were 5.7912, 9.8069, 7.6709, 9.3158, 9.0073, and 14.0923, respectively. Among the beers 10% ogapy showed the most diverse volatile profile in which 54 kinds of volatile compounds were detected.
- Antioxidant activity of various medicinal plant added rice beers The antioxidant activity of ogapy, hwangeum and sansuyu added rice beer was measured by DPPH radical scavenging assay and ABTS radical cation scavenging assay. Ogapy, hwangeum and sansuyu added rice beer showed higher antioxidant activity than that of unhulled rice beer. 5% ogapy rice beer which has the highest score in sensory evaluation test has lower antioxidant activity among medicinal plant added rice beers. However, the antioxidant activity of 10% sansuyu rice beer was 83% and 74% in DPPH radical scavenging assay and ABTS radical cation scavenging assay, respectively.
3. Investigation of quality control techniques including sensory properties of various rice beers
To investigate sensory properties of rice beer, sensory descriptors were developed by sensory panel and literature review. Fourteen basic categories were developed including fruty, nutty, cereal, caramel, phenolic, oxidized, sulfuric, microbiological, acidic, sweet, salty, bitter, mouthfeel, full-bodyness. These descriptors can be used in quality evaluation and control of rice beer. By addition of medicinal herbs such as sansuyu, hwangeum, and ogapy, 6 different rice beers were developed and those samples were evaluated by preference test and instrumental analysis with 100% rice wine and 100% beer. From the preference tests, overall acceptability of "rice 50% + ogapy 5%" was "5.70" by 9-point hedonic scale, which was highest among tested samples. Next was "rice 50% + ogapy 10%". Sansuyu was not considered as a good additive in rice beer. "rice 50% + ogapy 5%" sample was considered as proper levels in foam, sourness, bitterness, and cereal taste by 9-point just-about-right scale. The final formulation will be corrected to reflect consumer preference test results. A bitterness level was the highest in "rice 50% + hwangeum 10%" as "19.24", while other samples showed the range from 7.74 to 11.46. Foam stability was ranged from 809.03 to 83.43, which showed great differences among tested samples. "rice 50% + sansuyu 10%" showed the highest level, malt 100% was the lowest.
