2017 Research results

1. Phenotypes and brewing characteristics of sake yeast Kyokai no. 7 mutants resistant to valproate

Author: Kazuya Tomimoto, Takeshi Akao, Hisashi Fukuda
Abstract: Screening of drug-resistant mutants of sake yeast strains has been a major method for creation of superior strains. We attempted to create a valproic acid (VPA)-resistant mutant strain from sake yeast Kyokai No. 7 (K7). VPA is a branched-chain fatty acid and is an inositol synthesis inhibitor in mammals and yeast. We succeeded in isolating a mutant of strain K7 that can survive long-term in a VPA-containing medium. This strain, K7-VPA^LS, is significantly more resistant to not only VPA-induced cell death but also ethanol in comparison with the parent strain. Further experiments showed that the new strain is likely to have a deficiency in inositol and/or phosphatidylinositol synthesis. The major characteristics of sake brewed by strain K7-VPA^LS (compared with K7) were lower amino acidity, higher isoamyl acetate content without an increase in the isoamyl alcohol level and changes in constituent organic acids, particularly higher malate and succinate but lower acetate concentrations. In addition, taste sensor analysis revealed that K7-VPA^LS-brewed sake has milder sourness and higher saltiness or richness than K7-brewed sake does. High isoamyl acetate production may be related to a deficiency in phosphatidylinositol because this compound directly inhibits alcohol acetyltransferase, an enzyme responsible for isoamyl acetate synthesis. Strain K7-VPA^LS grew more rapidly than the parental strain did in a medium containing acetate as a sole carbon source, indicating that K7-VPA^LS effectively assimilates acetate and converts it to malate and succinate through the glyoxylate cycle. Thus, strain K7-VPA^LS shows improved characteristics for brewing of high-quality sake.
Source: Journal of the Institute of Brewing, 123, 252-258 (2017)

2. A correlation analysis of the compounds in Awamori and sweet potato shochu

Author: Hisashi Fukuda, Jinshun Han, Osamu Mizutani, Muneyoshi Kanai, Osamu Yamada
Abstract: Eighty-four volatile compounds of Awamori and sweet potato shochu were analyzed by head space solid phase micro extraction (SPME) and direct head space analysis, and the correlation between the compounds was analyzed. A high correlation between the medium-chain fatty acid esters and between higher fatty acid esters was generally shown, and the similarity of the chemical structure and biosynthesis was speculated to this contribute to correlation. In monoterpene alcohol and low boiling point ester, the compounds showed a high correlation and a synthesis path was expected. Surprisingly, furfural correlated with some of the aldehyde compounds. In addition, in Awamori and sweet poatato shochu, the compounds showing a high correlation were given individual consideration.
Source: J. Brew. Soc. Japan, 112, 273-314 (2017) in Japanese

3. Comparison the volatile composition of shochu exhibited in the Honkaku Shochu Contontest by used koji

Author: Hisashi Fukuda, Jinshun Han, Osamu Yamada
Abstract: Shochu exhibited in the Honkaku Shochu Contest was classified according to kinds of used koji, and 84 volatile compounds in it were attempted to be compared by koji category. Though there was a significant difference in some volatile compounds of shochu between used koji, it was expected to be due to materials. Then, as sample bias of sweet potato shochu among shochu exhibited was small compared to it of the other shochu, volatile compounds of sweet potato shochu were examined the effect of used koji. In sweet potato shochu, there was a significant difference in 13 volatile compounds between white koji products and black koji products. In a stepwise discriminant analysis procedure, white koji products and black koji products were classified by 6 volatile compounds (1-hexanol, 1-octen-3-ol, isobutyl caproate, ethyl myristate, α-bisabolol, and S-methyl thioacetate). Estimating the accuracy of the discriminant analysis by cross validation, the ratios of appropriate classification were 83.0%.
Source: J. Brew. Soc. Japan, 112, 343-349 (2017) in Japanese

4. Characteristics of the volatile composition of Japanese rum

Author

Hisashi Fukuda, Jinshun Han

Abstract

To classify Japanese rum (n=18) and imported rum (n=32), we analyzed 78 volatile compounds by solid phase micro extraction (SPME), and 6 volatile compounds by direct head space analysis. There was a significant difference in 34 volatile compounds between Japanese rum and rum made in Caribbean countries and bordering the Indian Ocean. In a stepwise discriminant analysis procedure using 6 volatile compounds (1-hexanol, guaiacol, diethyl succinate, 2-methylbutyl acetate, acetaldehyde and furfural), all of 50 samples were rightly classified. Estimating the accuracy of the discriminant analysis by cross validation, the ratios of appropriate classification were 100 %.

To test the robustness of a discrimination coefficient obtained, a discrimination analysis of Japanese rum and different imported rum (n=40) provided the ratios of appropriate classification at 92.5 %. We believe that Japanese rum can be distinguished from imported rum with relatively high precision by the discriminant analysis. In addition, the production process of Japanese rum speculated from compounds was given consideration.

Source

J. Brew. Soc. Japan, 112, 423-431 (2017) in Japanese

5. Factors affecting dimethyl trisulfide formation in wine

Author: Nahoko Nishibori, Asami Kuroda, Osamu Yamada, Nami Goto-Yamamoto
Abstract: Dimethyl trisulfide (DMTS), which develops in wine during storage, creates unpleasant aromas. However, mechanisms of DMTS formation in the wine-making process are poorly understood. Here we attempted to identify several factors that affect DMTS development during storage. Results show that the death of yeast cells followed by the leakage of cell contents into must enhances DMTS formation, but this effect differs with the kind of grapes. Oxidation of must as well as insufficient clarification of grape juice can also lead to DMTS development during storage. DMTS-P1 and methanethiol, precursor compounds of DMTS in other beverages, made little contribution to DMTS formation in wine. When synthetic grape must was fermented instead of grape juice, less DMTS developed, although almost yeast cells were dead. Results indicated that unknown compounds contained in grape juice are involved in DMTS formation and that key compounds involved in DMTS formation in wine originate from grapes.
Source: Food Science and Technology Research, 23, 241-248 (2017)

6. Analysis of Sake Components Presented to Sake Contest in 2016

Author: Tsutomu Fujii, Atsuko Isogai, Sachiko Iizuka, Hanae Izu, Ryoko Kanda, Nami Goto-Yamamoto
Source: Report of the Research Institute of Brewing, 189, 1-16 (2017) in Japanese

7. Review of the 39th Honkaku Shochu Contest in 2016

Author: Osamu Yamada, Nobuhiko Mukai, Muneyoshi Kanai, Osamu Mizutani, Nahoko Nishibori, Akinori Muto, Takeshi Akao, Maki Kamimoto, Nami Goto-Yamamoto
Source: Report of the Research Institute of Brewing, 189, 17-30 (2017) in Japanese

8. Anasysis of Beer Components Presented to Craft Beer Contest of Japan Brewers Association in 2016

Author: Kazutaka Kusaka, Akinori Muto
Source: Report of the Research Institute of Brewing, 189, 31-36 (2017) in Japanese

9. Shochu Sensory Assessmen

Author: Nobuhiko Mukai, Jinshun Han, Nahoko Nishibori, Muneyoshi Kanai
Source: Report of the Research Institute of Brewing, 189, 37-43(2017) in Japanese

10. Effects of low dose of ethanol on the senescence score, brain function and gene expression in senescence-accelerated mice 8 (SAMP8)

Author: Akiko Kimoto, Hanae Izu, Churan Fu, Sofya Suidasari, Norihisa Kato
Abstract: Accumulating epidemiological evidence suggests light to moderate alcohol intake reduces risk of several chronic diseases. However, there is limited information regarding the effects of low alcohol intake in animal studies. This study investigated the effect of low ethanol dosage on senescence-accelerated mouse (SAMP8), an animal model of aging and neurodegenaration. Male SAMP8 mice (11 weeks old) had free access to a commercial stock diet with drinking water containing 0%, 1% or 2% (v/v) ethanol for 15 weeks. The total grading score of senescence in the 1%-ethanol group was, in large part, the lowest among the three groups. Analysis using the open-field test revealed a significant elevation (+77%, P < 0.05) in the rearing activity (index of seeking behavior) in the 1%-ethanol group, but not in the 2%-ethanol group. In addition, 2% ethanol elevated spontaneous locomotor activity (+75%, P < 0.05), whereas 1% ethanol did not. Scrutiny of serum parameters indicated intake of 1% ethanol significantly decreased serum insulin levels (-13%, P < 0.05), whereas 2% did not. Intake of 2% ethanol significantly elevated (2.5-fold, P < 0.05) S100a8 mRNA (an inflammatory signal) in the brain, but that of 1% ethanol did not. Intriguingly, 1% ethanol intake remarkably elevated (10-fold, P < 0.05) mRNA of brain alcohol dehydrogenase 1 (Adh1), which metabolizes lipid-peroxidation products and is involved in the synthesis of retinoic acid, a neuroprotective factor. Of note, 2%-ethanol intake did not exert this effect. Taken together, intake of 1% ethanol is likely to be beneficial for SAMP8 mice.
Source: Experimental and Therapeutic Medcine, 14, 1433-1440 (2017)

11. Carbon Stable Isotope Analysis for Glucose in Sake: Simple Freeze-Dried Sake Can Substitute for Glucose Following HPLC Isolation

Author: Fumikazu Akamatsu, Tomokazu Hashiguchi, Yukari Igi, Hanae Izu, Tsutomu Fujii
Abstract: Carbon stable isotope analysis of ethanol is an established method for determining the authenticity of alcoholic beverages, but there is no accepted method for measurements of glucose carbon stable isotopic composition (δ¹³C). This study aims to establish two methods to determine accurately the δ¹³C value of glucose isolated from sake by high-performance liquid chromatography (HPLC) after three clean-up steps using ion exchange chromatography and in simple freeze-dried sake (total nonvolatile matter) and to examine two methods that yield different δ¹³C values. In the glucose isolation procedure, the δ¹³C values of glucose were not significantly affected by the glucose concentration, solvent (water or aqueous acetonitrile), drying method (freeze-dry or nitrogen-spraying), the clean-up step using ion exchange chromatography (weakly acidic cation-exchange, strongly acidic cation-exchange, and weakly basic anion-exchange resins), or HPLC isolation. Glucose nitrogen spray-dried after isolation by ion exchange chromatography and HPLC showed a carbon isotope discrimination value of <0.1 ‰. The glucose δ¹³C values ranged from -26.8 to -25.5 ‰ in authentic sake and from -27.0 to -11.0 ‰ in commercial sake samples. This HPLC isolation approach may provide a first step toward visualizing the brewing process via isotopic carbon flow during fermentation. Additionally, there was no significant difference between the δ¹³C values of glucose and total nonvolatile matter from sake. The δ¹³C measurement of simple freeze-dried sake can substitute for glucose δ¹³C measurement using HPLC isolation, thus aiding high-throughput detection of carbon derived from C₄ plants in sake.
Source: Food Analytical Methods, 10, 2792-2799 (2017)

12. Application of Carbon and Hydrogen Stable Isotope Analyses to Detect Exogenous Citric Acid in Japanese Apricot Liqueur

Author: Fumikazu Akamatsu, Takaaki Oe, Tomokazu Hashiguchi, Yuri Hisatsune, Takafumi Kawawo, Tsutomu Fujii
Abstract: Japanese apricot liqueur manufacturers are required to control the quality and authenticity of their liqueur products. Citric acid made from corn is the main acidulant used in commercial liqueurs. In this study, we conducted spiking experiments and carbon and hydrogen stable isotope analyses to detect exogenous citric acid used as an acidulant in Japanese apricot liqueurs. Our results showed that the δ¹³C values detected exogenous citric acid originating from C4 plants but not from C3 plants. The δ²H values of citric acid decreased as the amount of citric acid added increased, whether the citric acid originated from C₃ or C₄ plants. Commercial liqueurs with declared added acidulant provided higher δ¹³C values and lower δ²H values than did authentic liqueurs and commercial liqueurs with no declared added acidulant. Carbon and hydrogen stable isotope analyses are suitable as routine methods for detecting exogenous citric acid in Japanese apricot liqueur.
Source: Food Chemistry, 228, 297-300 (2017)

13. Evaluation of method bias for determining bacterial populations in bacterial community analyses

Author: Masayuki Takahashi, Yasuko Kita, Akihiro Mizuno, Nami Goto-Yamamoto
Abstract: Various methods are used for analyzing a bacterial community. We recently developed a method for quantifying each bacterium constituting the microbiota by combining a next-generation sequencing (NGS) analysis with a quantitative polymerase chain reaction (NGS-qPCR) assay. Our NGS-qPCR method is useful for analyzing a comprehensive bacterial community because it is enables the easy calculation of the amounts of each bacterium constituting the microbiota. However, it has not been confirmed whether the estimated bacterial community obtained using this NGS-qPCR method corresponds to the results obtained using conventional methods. Accordingly, we prepared model bacterial community samples and analyzed them by several methods (NGS-qPCR, species-specific qPCR, flow cytometry, total direct counting by epifluorescent microscopy [TDC], and plate count). The total bacterial cell densities determined by the PCR-based methods were largely consistent with those determined by the TDC method. There was a difference between the amounts of each bacterium analyzed by NGS-qPCR and species-specific qPCR, although the same trend was shown by both species-specific qPCR and NGS-qPCR. Our findings also demonstrated that there is a strong positive correlation between the cell densities of a specific bacterial group in craft beer samples determined by group-specific qPCR and NGS-qPCR, and there were no significant differences among quantification methods (we tested two bacterial groups: lactic acid bacteria and acetic acid bacteria). Thus, the NGS-qPCR method is a practical method for analyzing a comprehensive bacterial community based on a bacterial cell density.
Source: Journal of Bioscience and Bioengineering, 124(4), 476-486 (2017)

14. Phenotypic Diagnosis of Lineage and Differentiation During Sake Yeast Breeding

Author: Shinsuke Ohnuki, Hiroki Okada, Anne Friedrich, Yoichiro Kanno, Tetsuya Goshima, Hirokazu Hasuda, Masaaki Inahashi, Naoto Okazaki, Hiroyasu Tamura, Ryo Nakamura, Dai Hirata, Hisashi Fukuda, Hitoshi Shimoi, Katsuhiko Kitamoto, Daisuke Watanabe, Joseph Schacherer, Takeshi Akao, and Yoshikazu Ohya
Abstract: Sake yeast was developed exclusively in Japan. Its diversification during breeding remains largely uncharacterized. To evaluate the breeding processes of the sake lineage, we thoroughly investigated the phenotypes and differentiation of 27 sake yeast strains using high-dimensional, single-cell, morphological phenotyping. Although the genetic diversity of the sake yeast lineage is relatively low, its morphological diversity has expanded substantially compared to that of the Saccharomyces cerevisiae species as a whole. Evaluation of the different types of breeding processes showed that the generation of hybrids (crossbreeding) has more profound effects on cell morphology than the isolation of mutants (mutation breeding). Analysis of phenotypic robustness revealed that some sake yeast strains are more morphologically heterogeneous, possibly due to impairment of cellular network hubs. This study provides a new perspective for studying yeast breeding genetics and micro-organism breeding strategies.
Source: G3:Genes,Genomes,Genetics, 7 (8), 2807-2820 (2017)

15. Effects of moisture and pulverizing of rice on the absorption rate of rice grains used for awamori: improvement of the absorption ratio of steamed rice by two steamings

Author: Masaki Okuda, Midori Joyo, Hisashi Fukuda, Takako Tamamura
Abstract: Thai non-broken rice has been mainly used for the production of awamori after 2010. It is more difficult to absorb water ideally than for Thai broken rice, which has been mainly used for a long time. This difficulty in absorption for Thai non-broken rice has the recently demanded on immediate solution. In the present study, to obtain the basic knowledge for improving the absorption of Thai non-broken rice, we examined the suitability of Thai rice used for awamori production compared with Nipponbare, which is used for sake making. The property of Thai rice starch by RVA analysis was significantly different from that of Nipponbare. The water absorption ratio of rice showed a negative correlation with the moisture of rice grains in both Thai rice and Nipponbare. However, the ratio of water absorption of Thai rice was lower than that of Nipponbare, when the moisture of the rice was same. The speed of water absorption was significantly improved by pulverizing the rice grains when the steeping time was short. Two steamings also significantly improved the ratio of water absorption of steamed rice and enzyme digestibility. From the above results, we recommend that prevention of an increase in the moisture of rice grains is important to deal with Thai rice appropriately. Also, sufficient steeping time, or two steamings are effective to achieve the ideal ratio of water absorption when using Thai rice.
Source: J. Brew. Soc. Japan 112, 629-640 (2017) in Japanese

16. Chloride-free and water-soluble Au complex for preparation of supported small nanoparticles by impregnation method

Author: Haruno Murayama, Takayuki Hasegawa, Yusuke Yamamoto, Misaki Tone, Moemi Kimura, Tamao Ishida, Tetsuo Honma, Mitsutaka Okumura, Atsuko Isogai, Tsutomu Fujii, Makoto Tokunaga
Abstract: A novel simple and easy impregnation method for preparation of small gold (Au) nanoparticle (NP) catalysts (<3 nm) deposited on various supports including silica, which is difficult to be applied for conventional methods, has been developed. Chloride-free and water-soluble precursor, Au complexes coordinated with β-alanine, were successful for the preparing Au NPs, which exhibited an average diameter less than 3 nm. Thermal behavior of the Au complex was investigated by TG-DTA and in situ XAFS. XAFS analyses and DFT calculations revealed a molecular structure of the Au complex to be square-planar coordination structure and mononuclear complex of Au³⁺. Lower decomposition and reduction temperature of the chloride-free Au complex prevented Au atoms from aggregating and from following growth of Au particles. The prepared Au/SiO2 showed high selectivity for hydrogenation of 1-nitro-4-vinylbenzene into 1-ethyl-4-nitorobenzene and good performance for removal of unpalatable aroma by means of adsorption of polysulfide molecules.
Source: Journal of Catalysis, 353, 74-81 (2017)

17. Investigation of the content of nutrients and functional ingredients in shochu distillation residue

Author: Nobuhiko Mukai, Tomoko Morimoto, Narumi Fuke, Satoko Yoshida, Tsutomu Kumazaki, Takumi Teramoto, Daiki Uesako, Ryuichi Sato, Nahoko Nishibori, Muneyoshi Kanai, Osamu Yamada, Tsutomu Fuji
Abstract: Shochu distillation residue (SDR), generated as a shochu distillery by-product, includes abundant nutrients. We collected 54 samples of SDR made from various raw materials from 30 shochu manufacturers. SDR was separated into cake and liquid parts by centrifuges. The cake ratio of SDR was 28.0% on average, and the cake of SDR contained 79.1 g/100 g of moisture on average. The cake of SDR included 32.1 g of protein, 12.7 g of lipid, 51.7 g of carbohydrate, and 3.4 g of ash, 450.1 kcal of calorific value, 381.1 mg of folate (the sum of tetrahydrofolic acid (THF) and 5-methyltetrahydrofolate (5-MTHF)), 0.72 mg of vitamin B₆, 14.5 mg of S-adenosylmethyonine (SAM) and 9.1 mg of polyamines (the sum of putrescine (PUT), spermidine (SPD) and spermine (SPM)) at an average level per 100 g (dry weight). The liquid part of SDR included 10.3 mg of folate, 0.15 mg of vitamin B₆, 3.0 mg of SAM and 1.3 mg of polyamines at an average level per 100ml. It was revealed that SDR contains relatively large amounts of folate, vitamin B₆, SAM and polyamines in comparison with other foods and drinks. These results can lead to new utilizations and value-added improvements for SDR.
Source: J. Brew. Soc. Japan 112, 695-706 (2017) in Japanese

18. Chromosomal aneuploidy improves brewing characteristics of sake yeas

Author: Masafumi Kadowaki, Yuki Fujimaru, Seiga Taguchi, Jannatul Ferdouse, Kazutaka Sawada, Yuta Kimura, Yohei Terasawa, Gennaro Agrimi, Toyoaki Anai, Hideki Noguchi, Atsushi Toyoda, Asao Fujiyama, Takeshi Akao, Hiroshi Kitagaki
Abstract: The effect of chromosomal aneuploidy on the brewing characteristics in brewery yeasts has not been studied. Here, we report that chromosomal aneuploidy in sake brewery yeast (Saccharomyces cerevisiae) leads to the development of favorable brewing characteristics. We found that pyruvate-underproducing sake yeast, which produces less off-flavor diacetyl, is aneuploid and trisomic for chromosomes XI and XIV. To confirm that this phenotype is due to aneuploidy, we obtained 45 haploids with various chromosomal additions and investigated their brewing profiles. A greater number of chromosomes correlated with a decrease in pyruvate production. Especially, sake yeast haploids with extra chromosomes in addition to chromosome XI produced less pyruvate than euploids. Mitochondria-related metabolites and intracellular oxygen species in chromosome XI aneuploids were higher than those in euploids and this effect was canceled in their petite strains, suggesting that an increase in chromosomes upregulated mitochondrial activity and decreased pyruvate levels. These findings suggested that an increase in chromosome number including that in chromosome XI, in sake yeast haploids leads to pyruvate underproduction through the augmentation of mitochondrial activity. This is the first report proposing that aneuploidy in brewery yeasts improves their brewing profile.

IMPORTANCE

Chromosomal aneuploidy has not been evaluated in development of sake brewing yeast strains. This is the first study to show the relationship between chromosomal aneuploidy and brewing characteristics of brewery yeast strains. High concentrations of pyruvate during sake storage give rise to α-acetolactate and in turn to high diacetyl, which is considered an off-flavor. It was demonstrated that pyruvate-underproducing sake yeast is trisomic for chromosome XI and XIV. Furthermore, sake yeast haploids with extra chromosomes produced reduced levels of pyruvate and showed metabolic processes characteristic of increased mitochondrial activity. This novel discovery will enable the selection of favorable brewery yeasts by monitoring the copy numbers of specific chromosomes through a process that does not involve generation/use of genetically modified organisms.
Source: Applied and Environmental Microbiology, 83 (24), e01620-17 (2017)

19.. Characterization of amylolytic enzyme overproducing mutant of Aspergillus luchuensis obtained by ion beam mutagenesis

Author: Toshihiro Kojo, Chihiro Kadooka, Marisa Komohara, Shiori Onitsuka, Miya Tanimura, Yukiko Muroi, Shugo Kurazono, Yohei Shiraishi, Ken Oda, Kazuhiro Iwashita, Masahira Onoue, Kayu Okutsu, Yumiko Yoshizaki, Kazunori Takamine, Taiki Futagami, Kazuki Mori, Hisanori Tamaki
Abstract: Aspergillus luchuensis is a kuro (black) koji fungus that has been used as a starch degrader for the awamori- and shochu-making industries in Japan. In this study, we investigated the effect of ion beam irradiation on A. luchuensis RIB2601 and obtained a high starch-degrading mutant strain U1. Strain U1 showed reduced growth rate, whereas it showed higher α-amylase, glucoamylase, and α-glucosidase activities on a mycelial mass basis than the wild type (wt) strain both on agar plates and in rice koji. In addition, strain U1 showed higher N-acetylglucosamine content in the cell wall and higher sensitivity to calcofluor white, suggesting a deficiency in cell wall composition. Interestingly, produced protein showed higher expression of acid-labile α-amylase (AmyA) and glucoamylase (GlaA) in strain U1, although real-time RT-PCR indicated no significant change in the transcription of the amyA or glaA gene. These results suggested that the high amylolytic activity of strain U1 is attributable to a high AmyA and GlaA production level, but the elevated production is not due to transcriptional regulation of the corresponding genes. Furthermore, RNA-seq analysis indicated that strain U1 shows transcriptional changes in at least 604 genes related to oxidation-reduction, transport, and glucosamine-containing compound metabolic processes, which may be involved in the deficient cell wall composition of strain U1.
Source: The Journal of general and applied microbiology, doi10.2323/jgam.2017.02.004

20. Analysis of protein composition in rice cultivar used for sake brewing, and their effects on nitrogen compounds in sake

Author: Masaki OKUDA, Midori JOYO, Yuki TAMAMOTO, Motoki SASAKI, Kei TAKAHASHI, Nami GOTO-YAMAMOTO, Masaru IKEGAMI and Katsumi HASHIZUME
Abstract: Background and objectives

Protein composition analysis of 81 rice samples was performed on three cultivars harvested different regions in Japan, and the effects of the protein composition on the nitrogen composition in sake.

Findings

Crude protein content showed a significant positive correlation with glutelin content. Yamadanishiki cultivars showed lower crude protein and glutelin contents compared with Gohyakumangoku cultivars harvested from the same field. Total nitrogen content in the enzyme digest of steamed rice grains showed a significant positive correlation with the crude protein and glutelin contents. Ten polished (70%) white rice samples were investigated in a small-scale sake brewing test. Total nitrogen compounds, bitter-tasting peptides, and free amino acids in the brewed sake positively correlated with the glutelin content of the rice samples. There were no clear correlations between a-amylase and acid proteinase activities with the nitrogen compounds in the sake.

Conclusions

The results indicated that the glutelin content in the cultivar rice affects sake quality through taste-active and other nitrogen-containing compounds produced from rice glutelin in the sake brewing process.

Significance and novelty

We revealed that the glutelin content in the milled rice grains is important to brew high quality of sake clearly. The present results would be useful for cultivation or breeding of sake rice.
Source: Cereal Chemistry, 95, 320-329 (2018)

21. Characteristics of the volatile composition of Cachaca

Author: Hisashi FUKUDA and Jinshun HAN
Abstract: To classify the compounds of rum and imported cachaca, we analyzed 78 volatile compounds by solid phase micro extraction (SPME) and 6 volatile compounds by direct head space analysis. There was a significant difference for 10 volatile compounds between cachaca and rum made in Caribbean and Indian Ocean regions. In a stepwise discriminant analysis procedure using 3 volatile compounds (β-phenethyl alcohol, diethyl succinate and S-methyl thioacetate) , 31 of 33 samples were rightly classified. Estimating the accuracy of the discriminant analysis by cross validation, the ratios of appropriate classification were 90.9 %. For cachaca and Japanese rum, there was a significant difference in 18 of 84 volatile compounds. All of 16 samples were rightly classified by 2 volatile compounds (citronellol and furfural). When estimating the accuracy of the discriminant analysis, the ratios of appropriate classification were 100 %..
Source: J. Brew. Soc. Japan, 113, 105-114 (2018)

22. Changes in folate level during sweet potato shochu production

Author: Nobuhiko MUKAI, Tomoko MORIMOTO, Narumi FUKE, Daiki UESAKO, Osamu MIZUTANI, Nahoko NISHIBORI, Muneyoshi KANAI, Osamu YAMADA and Tsutomu FUJII
Abstract: We have reported that the shochu distillation residue (SDR) contains relatively large amounts of folate (the sum of tetrahydrofolic acid (THF) and 5-methyltetrahydrofolate (5-MTHF)) in comparison with other foods and drinks. However, the origin of the folate in SDR has not been clear. We carrried out a sweet potato shochu production test by pilot-scale plant (total weight of rice and sweet potato was 48 kg) to examine the folate high component factor in SDR derived from sweet potato shochu, and we analyzed the folate content of samples in each process of manufacture. THF was not present in rice, sweet potato, or rice koji. It was produced by yeast during fermentation, but almost disappeared by distillation. On the other hand, 5-MTHF was included in rice and sweet potato and produced by koji during koji making and by yeast during fermentation. It was partly decreased by distillation. When the total amount of folate at the end of the second mash was assumed as 100, the contribution of the steamed sweet potato used in the second mash was 46.4, and the production by yeast during fermentation in the second mash was 44.1. It was found that almost all of the folate in SDR came from sweet potato and the production by yeast. Thirty-six percent of the total folate was decreased in distillation. In addition, in the storage test of SDR, as a result of inhibiting of the decrease of 5-MTHF, the storage stability of the folate was improved by the deoxygenation treatment of SDR and freeze-drying of cake.
Source: J. Brew. Soc. Japan, 113, 115-122 (2018)

23. Ethyl Carbamate Degrading Enzyme from Yeast Meyerozyma caribbica strain SKa5: Purification and Biochemical Properties.

Author: Jantaporn THONGEKKAEW, Tsutomu FUJII and Kazuo MASAKI
Abstract: Ethyl carbamate degrading enzyme from yeast which was isolated from spoilage fruit was studied. Based on ITS1-5.8S-ITS2 region and D1/D2 domains of the 26S subunit analysis, the selected yeast was identified as Meyerozyma caribbica and named as M. caribbica SKa5. The enzyme from cell extracted was purified by anion exchange chromatography. The molecular mass of the enzyme was approximately 55 kDa, as identified by SDS-PAGE. The optimum pH and temperature were 7.0-8.0 and 37℃, respectively. The enzyme was stable at pH range of 4.5-8.0 and at temperature range of 10-37℃. The enzyme also exhibited ethanol tolerance at concentration of 20% (v/v). In addition, the enzyme was not affected in the presence of Na⁺, K⁺, Ca²⁺, Mg²⁺, Mn²⁺, β-mercaptoethanol and EDTA. This favorable properties could become one of potential enzyme resources for removal of ethyl carbamate in alcoholic beverages and fermented foods industry.
Source: Research Journal of Pharmaceutical, Biological and Chemical Sciences, 9(2), 276-284 (2018)

24. Change in the purity of cerulenin tolerant yeast and relation with the ethyl caproate content in a fermenting Shochu mash during repeating Sashimoto

Author: Takafumi MUTOU, Masaaki INAHASHI, Yasuzo KIZAKI, Naoto OKAZAKI, Takeaki ISHIKAWA and Takeshi AKAO
Abstract: On making the Japanese traditional spirits Shochu, the pitching is commonly carried out by the addition of a volume of about 0.6% of fermenting mash. The re-pitching procedure is called "Sashimoto". By the repetition of Sashimoto, the wild yeasts which invade the Shochu mash multiply and become dominant because the growth rates of most wild yeasts are faster than that of pure Shochu-yeast. Consequently, this brings about a decreased purity of Shochu-yeasts and undesirable quality for the resulting Shochu. We studied the changes in the purity of Shochu-yeast S4 during repeating Sashimoto and evaluated the qualities of resulting Shochu. Since S4 yeast is a cerulenin tolerant and ethyl caproate high producing strain while most wild yeasts are cerulenin sensitive strains, we confirmed that changes in S4 purity during the repeating Sashimoto were possible by detecting its cerulenin tolerance as the yeast purity index.We also confirmed that, in conditions of the wild yeast, the specific growth rate is from 1.2 to 2.4 times faster than that of Shochu-yeast, and it was necessary to keep yeast purity higher than 50% to maintain a high ethyl caproate content. A cerulenin sensitive wild yeast (WS1) isolated from the Shochu mash in this study was identified as Saccharomyces cerevisiae by its physical properties and the homologous analysis of the ITS domain.
Source: J. Brew. Soc. Japan, 113, 169-178 (2018)

25. Influence of starch retrogradation in steamed rice grains on the use of material in sake making

Author: Syuhei KAWANE, Masaki OKUDA, Midori JOYO, Hisashi FUKUDA and Nami GOTO-YAMAMOTO
Abstract: Using rice samples grown at a high temperature (2010 year) and low temperature (2009 year) during grain filling, the retrogradation of starch in steamed rice grains during sake making was examined in order to obtain the basic knowledge of improvement for the use of material rice grains grown under high temperatures during grain filling. Although the enthalpy change derived from the retrogradation of amylopectin increased during the koji making and sake mash processes, the speed of the retrogradation of rice grains harvested at a high temperature was faster than that harvested at a low temperature. Also, the speed of retrogaradation of amylopectin proceeded faster during koji making than during sake mash. From a small-scale brewing test, it was seen that the rice for koji had a greater influence on the material used such as sake cake ratios than the rice grains for steaming. The decreasing degree of enzymatic digestibility of steamed rice grains after partial retrogradation of starch stored in a plastic bag or in a buffer was higher in rice grains grown at a high temperature than for that stored in the rice grains grown at a low temperature. The degree of retrogradation showed a high negative correlation with the enzymatic digestibility of steamed rice grains after the partial retrogradation of starch stored in a plastic bag or in a buffer. Therefore, when the steamed rice grains were stored in a plastic bag such as under koji making but also in a buffer such as sake mash, the retrogradation of steamed rice grains proceeded and the retrogradation of steamed rice grains grown at a high temperature had a considerable influence on the enzyme digestibility during sake mash.
Source: J. Brew. Soc. Japan, 113, 179-190 (2018)