2018 Research results

1. 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)

2. 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)

3. 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)

4. 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)

5. 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)

6. 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)

7. Selective adsorption of 1,3-dimethyltrisulfane (DMTS) responsible for aged odour in Japanese sake using supported gold nanoparticles

Author

Haruno Murayama, Yusuke Yamamoto, Misaki Tone, Takayuki Hasegawa, Moemi Kimura, Tamao Ishida, Atsuko Isogai, Tsutomu Fujii, Mitsutaka Okumura, Makoto Tokunaga

Abstract

Gold (Au) nanoparticles (NPs) supported on SiO2 (Au/SiO₂) were prepared by a practical impregnation method and applied as an adsorbent for 1,3-dimethyltrisulfane (DMTS), which is responsible for an unpleasant odour in drinks, especially Japanese sake. Compared with a conventional adsorbent, activated carbon, Au/SiO₂ selectively reduced the DMTS concentration in Japanese sake without decreasing the concentrations of other aromatic components. DFT calculations revealed that the selective adsorption of DMTS occurred through the formation of a stable intermediate. The size of the supported Au NPs was controlled by the preparation conditions and determined from TEM observations and XRD measurements, and the size was ranged from 2.4 nm to 30 nm. Au/SiO₂ having Au NPs with a diameter of 2.4 nm adsorbed DMTS the most efficiently. Smaller Au NPs showed better DMTS adsorption capabilities because larger amounts of Au atoms were exposed on their surfaces in the size range of this study. Langmuir-type monolayer adsorption and one-to-one binding of Au-S are proposed to occur based on an adsorption isotherm experiment. Even though significant differences of the fruity aroma score were not observed in the sensory evaluation between Au/SiO₂ and activated carbon for this less aromatic Japanese sake, Au/SiO₂ selectively decreased the DMTS concentration in the instrumental analysis.

Source

Scientific Reports, 8, 16064 (2018)

8. Development of DNA markers to differentiate good Kyokai sake yeast and the other yeast strains

Author

Takeshi Akao, Zou Yan, Daisuke Watanabe, Naoto Okazaki, and Hitoshi Shimoi

Abstract

Previous studies revealed that a representative sake yeast strain, Kyokai No. 7 (K7), possesses three loss-of-function mutations, rim155067ins, msn4C1540T, Δppt1::Ty2, which enable high fermentation ability of the strain. Since all three were common and specific to K7 and closely related good strains, such as K6, K9, K10 and their derivative strains among approximately 30 strains tested by each mutation, they were expected to work as efficient DNA markers to differentiate those good strains from others. In this study, a rapid and accurate genotyping method, high resolution melting (HRM) analysis, was employed and optimized for typing RIM15⁵⁰⁶⁷ins and MSN4¹⁵⁴⁰, respectively. Typing of these DNA markers was then applied to a broad range of yeast strains (98 strains, 134 stocks) to estimate whether they belonged to the group of K7-realated strains.

Source

J. Brew. Soc. Japan,113 (10), 631-641 (2018) in Japanese

9. Characteristic features of the unique house sake yeast strain Saccharomyces cerevisiae Km67 used for industrial sake brewing

Author

Yoshifumi Takao, Toshinari Takahashi, Tasuku Yamada, Tetsuya Goshima, Atsuko Isogai, Kazuo Sueno, Tsutomu Fujii, and Takeshi Akao

Abstract

For several decades, almost all sake has been brewed with sake yeast Saccharomyces cerevisiae Kyokai no. 7 (K7) group strains. Although the widespread use of these strains has contributed to sake quality improvement, it may have lessened the diversity of sake gustatory properties brought about by house sake yeast (indigenous yeast of sake brewery). Sake yeast S. cerevisiae strain Km67 derives from the house yeast strain of Kiku-masamune Sake Brewing Co., Ltd., and it has been playing a central role in industrial sake brewing for decades. By using DNA sequencing, we revealed that strain Km67 does not possess specific loss-of-function mutations of stress response-related genes, which are characteristic of K7 group strains. Km67 had higher stress tolerance than K7 group strains likely because of the more efficient function of the stress response and heat shock elements in this strain. Sensory evaluation and taste sensor analysis demonstrated that sake brewed with Km67 had characteristically thicker body than sake brewed with K7 group strains. Chemical analysis suggested that unique sensory properties of the sake brewed with Km67 were due to high citramalic acid concentration. Taken together, these results revealed that strain Km67 differs from K7 group strains by genetic background and confers unique chemical composition and taste qualities upon sake it generates. It is expected that sake quality and gustatory properties will be diversified by utilizing house yeast such as strain Km67.

Source

Journal of Bioscience and Bioengineering, 126 (5), 617-623 (2018)

10. Analysis of Sake Components Presented to Sake Contest in 2017

Author

Tsutomu FUJII, Atsuko ISOGAI,Sachiko IIZUKA, Hanae IZU, Ryoko KANDA, Tomokazu HASHIGUCHI and Nami GOTO-YAMAMOTO

Source

Report of the Research Institute of Brewing, 190, 1-18 (2018) in Japanese

11. Review of the 40th Honkaku Shochu and Awamori Contest in 2017

Author

Nobuhiko MUKAI, Muneyoshi KANAI, Masayuki TAKAHASHIO, Nahoko NISHIBORI, Akinori MUTO, Toshihiro YOSHIMURA, and Nami GOTO-YAMAMOTO

Source

Report of the Research Institute of Brewing, 190, 19-34 (2018) in Japanese

12. Anasysis of Beer Components Presented to Craft Beer Contest of Japan Brewers Association in 2018

Author

Kazutaka KUSAKA, Maki KAMIMOTO and Akinori MUTO

Source

Report of the Research Institute of Brewing, 190, 35-40 (2018) in Japanese

13. Classification of Kyokai sake yeast stock strains by brewing charecteristics

Author

Naoto OKAZAKI, Futami NORO, Masaaki INAHASHI, Katsumi NAKAHARA, Hirokazu HASUDA, Takafumi MUTOU, Tomoko MURAKAMI, Tetsuya GOSHIMA, Takeshi AKAO, Yasuzo KIZAKI, and Takeaki ISHIKAWA

Abstract

Twenty brewing characteristics which contribute to classify a Kyokai sake yeast strains were selected by the partition analysis for 24 Kyokai yeast strains which contained 385 stock strains. It was possible to classify these as independent clusters for Kyokai yeast strains using 20 explanatory variables. This narrowed to 344 strains when excluding 41 strains of samples missed from the 24 main clusters. While the total numbers of distinction error strains of a discriminant analyses using 18 explanatory variables for 344 strains were 7 strains, when considered with 16 explanatory variables which excluded the amino acid component left 10 strains. Therefore, we decided to exclude amino acid composition from the analysis items because the contribution was small and there was little influence in cluster analysis and discriminant analysis. Regardless of the old or new period distributions, the brewing characteristics of the 344 strains of K-7 were kept for only one cluster and the K-7 cluster could be roughly divided into 3 sub clusters by the cluster analysis. The reason for being divided into 3 clusters was because of the fermentation ability. In the cluster analyses by 11 brewing characteristics for 24 kinds of all yeast select ion candidates in 1250 strains since 2003, 76 strains of clusters of high aroma generation strains were sorted out and the composition strains were only K-1601, K-1701 and K-1801. Also, all K-1801 distribution strains from 2006 to 2014 were contained in the cluster of K-1801, and the brewing characteristics of the K-1801 were stable.

Source

J. Brew. Soc. Japan,113 (8), 515-524 (2018) in Japanese

14. Effect of acetic acid bacteria on alcoholic liver injury in C57BL/6J mice.

Author

Satoshi SEINO, Hitoshi KURIHARA, Ryosuke MATSUOKA, Yohei OKUYAMA, Masaaki KUNOU, Hanae IZU, Yongqiang CHENG, Yanxiang GAO, Beizhong HAN

Abstract

The effect of ingestion of acetic acid bacteria on alcoholic liver injury was evaluated. C57BL/6J mice (8 weeks old, male, 22-27 g) were divided into three groups: the control group (without ethanol), ethanol group (ethanol 2.5 g/kg), and ethanol + acetic acid bacteria group (ethanol 2.5 g/kg + acetic acid bacteria 10 mg). The mice were given three times per day for 14 consecutive days in each group. Then the serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and liver lipids of the mice were measured. As a result, AST and ALT levels, liver triglyceride and cholesterol levels were significantly higher in the ethanol group than those in the control group (P＜0.05). The ethanol + acetic acid bacteria group had significantly lower levels than those in the ethanol group(P＜0.05). These results suggested that the ingestion of acetic acid bacteria might alleviate alcoholic liver injury.

Source

China Brewing 37(8), 28-31 (2018) in Chinese

15. Discrimination of wine from grape cultivated in Japan, imported wine, and others by multi-elemental analysis

Author

Hideaki SHIMIZU, Fumikazu AKAMATSU, Aya KAMADA, Kazuya KOYAMA, Masaki OKUDA, Hisashi FUKUDA, Kazuhiro IWASHITA, Nami GOTO-YAMAMOTO

Abstract

Differences in mineral concentrations were examined among three types of wine in the Japanese market place: Japan wine, imported wine, and domestically produced wine mainly from foreign ingredients (DWF), where "Japan wine" has been recently defined by the National Tax Agency as domestically produced wine from grapes cultivated in Japan. The main objective of this study was to examine the possibility of controlling the authenticity of Japan wine. The concentrations of 18 minerals (Li, B, Na, Mg, Si, P, S, K, Ca, Mn, Co, Ni, Ga, Rb, Sr, Mo, Ba, and Pb) in 214 wine samples were determined by inductively coupled-plasma mass spectrometry (ICP-MS) and ICP-atomic emission spectrometry (ICP-AES). In general, Japan wine had a higher concentration of potassium and lower concentrations of eight elements (Li, B, Na, Si, S, Co, Sr, and Pb) as compared with the other two groups of wine. Linear discriminant analysis (LDA) models based on concentrations of the 18 minerals facilitated the identification of three wine groups: Japan wine, imported wine, and DWF with a 91.1% classification score and 87.9% prediction score. In addition, an LDA model for discrimination of wine from four domestic geographic origins (Yamanashi, Nagano, Hokkaido, and Yamagata Prefectures) using 18 elements gave a classification score of 93.1% and a prediction score of 76.4%. In summary, we have shown that an LDA model based on mineral concentrations is useful for distinguishing Japan wine from other wine groups, and can contribute to classification of the four main domestic wine-producing regions of Japan.

Source

Journal of Bioscience and Bioengineering, 125, 413-418 (2018)

16. Construction of sake yeast with low production of dimethyl trisulfide (DMTS) precursor by a self-cloning method

Author

Yuriko IKEDA, Atsuko ISOGAI, Yuta MORIYOSHI, Ryoko KANDA, Kazuhiro IWASHITA, Tsutomu FUJII

Abstract

Dimethyl trisulfide (DMTS) is the primary component responsible for "hineka", the stale aroma of Japanese sake. Deletion of the MRI1 or MDE1 gene of sake yeast, encoding 5'-methylthioribose-1-phosphate isomerase and 5'-methylthioribulose-1-phosphate dehydratase, respectively, has been reported to greatly reduce the amount of DMTS precursor (DMTS-P1) in sake and to suppress the formation of DMTS during storage. In this study, we constructed sake yeast strains lacking MRI1 gene function by a self-cloning method. Two methods were applied: in one, a stop codon was introduced in the MRI1 ORF by point mutation; in the other, the entire MRI1 ORF was deleted from the genome. In both methods, a plasmid vector containing drug-resistance and counter-selectable markers was used to introduce the mutation. We successfully obtained the strains, which did not contain the plasmid sequences, by both methods. Small-scale sake brewing tests using these SC strains (strains obtained by the self-cloning method) found that DMTS-P1 was hardly detected in sake brewed with SC strains, and DMTS production after sake storage was greatly reduced as compared with the parent strain. The components of brewed sake were almost the same between the SC and parent strains. These results suggest that SC strains can produce sake with higher flavor stability without changing the sake brewing properties.

Source

Journal of Bioscience and Bioengineering, 125, 419-424 (2018)

17. The delaying effect of alpha-glycerophosphocholine on senescence, transthyretin deposition, and osteoarthritis in senescence-accelerated mouse prone 8 mice.

Author

Kiminori MATSUBARA, Mayumi OKUDA, Sachi SHIBATA, Shigeru MIYAKI, Takeshi OHKUBO, Hanae IZU, Tsutomu FUJII

Abstract

Administration of alpha-glycerophosphocholine (GPC), a choline compound in food, is expected to contribute to human health. In this study, we evaluated its effect on aging in senescence-accelerated mouse prone 8 (SAMP8) mice. Male SAMP8 mice had free access to a commercial stock diet and drinking water with or without GPC (0.07 mg/ml). Mice in the GPC group had significantly lower total senescence grading score than that of the control group at 36 weeks of age. Administration of GPC decreased the deposition of transthyretin (TTR), an amyloidogenic protein, in the brain. Aggregated TTR activated microglia and led to neuroinflammation. Thus, GPC would protect the brain by reducing TTR deposition and preventing neuroinflammation. In a histological study of knee joints, it was found that SAMP8 mice administered GPC showed decreased joint degeneration. These results suggest that GPC delays the aging process and may be a useful compound in anti-aging functional food development.

Source

Bioscience, Biotechnology, and Biochemistry, 82(4), 47-653 (2018)

18. MAL73, a novel regulator of maltose fermentation, is functionally impaired by single nucleotide polymorphism in sake brewing yeast

Author

Takumi OHDATE , Fumihiko OMURA, Haruyo HATANAKA, Yan ZHOU, Masami TAKAGI, Tetsuya GOSHIMA, Takeshi AKAO, Eiichiro ONO

Abstract

For maltose fermentation, budding yeast Saccharomyces cerevisiae operates a mechanism that involves transporters (MALT), maltases (MALS) and regulators (MALR) collectively known as MAL genes. However, functional relevance of MAL genes during sake brewing process remains largely elusive, since sake yeast is cultured under glucose-rich condition achieved by the co-culture partner Aspergillus spp.. Here we isolated an ethyl methane sulfonate (EMS)-mutagenized sake yeast strain exhibiting enhanced maltose fermentation compared to the parental strain. The mutant carried a single nucleotide insertion that leads to the extension of the C-terminal region of a previously uncharacterized MALR gene YPR196W-2, which was renamed as MAL73. Introduction of the mutant allele MAL73L with extended C-terminal region into the parental or other sakeyeast strains enhanced the growth rate when fed with maltose as the sole carbon source. In contrast, disruption of endogenous MAL73 in the sake yeasts decreased the maltose fermentation ability of sake yeast, confirming that the original MAL73 functions as a MALR. Importantly, the MAL73L-expressing strain fermented more maltose in practical condition compared to the parental strain during sake brewing process. Our data show that MAL73(L) is a novel MALR gene that regulates maltose fermentation, and has been functionally attenuated in sake yeast by single nucleotide deletion during breeding history. Since the MAL73L-expressing strain showed enhanced ability of maltose fermentation, MAL73L might also be a valuable tool for enhancing maltose fermentation in yeast in general.

Source

PLoS ONE 13(6): e0198744 (2018)

19. Estimation method for enzyme digestibility of steamed rice grains for sake making using alkali / urea solubility

Author

Masaki OKUDA, Midori JOYO, Hisashi FUKUDA

Abstract

In the present study, we investigated the estimation method for the enzyme digestibility of steamed rice grains for sake making using alkali / urea solubility. Visual observation of the alkali / urea concentration solubilizing rice grains showed significant correlations with the DSC (= Differential Scanning Calorimeter) gelatinization temperature, the enzyme digestibility of steamed rice grains, and the retrogradation of steamed rice grains. The absorbance of iodine staining after soaking rice grains in urea solutions measured using a spectrophotometer also showed significant correlations with the enzyme digestibility of steamed rice grains and the retrogradation of steamed rice grains. Therefore, the enzyme digestibility of steamed rice grains for sake making can be estimated easily by the alkali / urea concentration solubilizing rice grains and the absorbance of iodine staining after soaking the rice grains in a urea solution. However, the polishing ratio and the moisture content of rice grains influenced the urea concentration solubilizing rice grains, although the existence of a white-core did not. In conclusion, these methods will be useful to estimate the enzyme digestibility of steamed rice grains for sake making, if the estimation standards according to the polishing ratio and moisture content of the rice grains can be determined.

Source

J. Brew. Soc. Japan, 113, 315-330 (2018) in Japanese

20. Evaluation of Candida easanensis JK8 β-glucosidase with potentially hydrolyse non-volatile glycosides of wine aroma precursors

Author

Thongekkaew J, Fujii T, Masaki K, Koyama K

Abstract

Important 'floral' aromas naturally occur in grapes predominantly as flavourless glycoconjugate precursors. Since these aroma compounds can be released by hydrolysis, different glycosidase enzymes can potentially contribute different aromas to wines. In this paper, the effects of crude and purified Candida easanensis JK8 β-glucosidases on wine aroma precursors of Muscat of Alexandria grape powder were investigated by GC/MS combined with stir bar sorptive extraction (SBSE). A total of 19 bound volatile compounds were identified, including phenols, terpenes, aldehyde, ester and alcohols. The concentrations of terpenes especially nerol and geraniol, and β-Damascenone, a C13-norisoprenoid, contributes flowery and slightly fruity aromas were signiflcantly increased in enzyme treated. These results suggest the potential application of this yeast β-glucosidase as an aroma-enhancing enzyme in winemaking.

Source

Natural Product Research, 1-5 (2018)