Hirotaka Kaneda

The production of linoleic and linolenic acid hydroperoxides during mashing

Abstract To clarify the lipid oxidation mechanism during wort production, the production of hydroperoxides during mashing was studied using a chemiluminescence-HPLC method. Free linoleic and linolenic acids increased during mashing and their rates of increase were significantly accelerated at 65°C, indicating that lipase acts during mashing. Linoleic and linolenic acid hydroperoxides increased just after mashing-in, reached a maximum level after 10 min at 65°C, and then decreased. When malt with higher lipoxygenase activity was used or the mashing was started at a lower temperature, the production of both hydroperoxides significantly increased. When an inhibitor of lipoxygenase was added to the mash just before mashing, the production of both hydroperoxides drastically decreased. Therefore, it is suggested that lipoxygenase and lipase in malt plays an important role in the production of linoleic and linolenic acid hydroperoxides during mashing.

Identification and Functional Analyses of Two cDNAs That Encode Fatty Acid 9-/13-Hydroperoxide Lyase (CYP74C) in Rice

Fatty acid hydroperoxide lyase (HPL), a member of cytochrome P450 (CYP74), produces aldehydes and oxo-acids involved in plant defensive reactions. In monocots, HPL that cleaves 13-hydroperoxides of fatty acids has been reported, but HPL that cleaves 9-hydroperoxides is still unknown. To find this type of HPL, in silico screening of candidate cDNA clones and subsequent functional analyses of recombinant proteins were performed. We found that AK105964 and AK107161 (Genbank accession numbers), cDNAs previously annotated as allene oxide synthase (AOS) in rice, are distinctively grouped from AOS and 13-HPL. Recombinant proteins of these cDNAs produced in Escherichia. coli cleaved both 9- and 13-hydroperoxide of linoleic and linolenic into aldehydes, while having only a trace level of AOS activity and no divinyl ether synthase activity. Hence we designated AK105964 and AK107161 OsHPL1 and OsHPL2 respectively. They are the first CYP74C family cDNAs to be found in monocots.

Behavior of mono-, di-, and trihydroxyoctadecenoic acids during mashing and methods of controlling their production.

The behavior of mono-, di-, and trihydroxyoctadecenoic acids was investigated during laboratory-scale mashing under various conditions with a view to controlling their production. Using a malt in which the lipoxygenase activity was at only a trace level (less than 0.01 U/g) or starting the mashing at a higher temperature than that conventionally used (65 degrees C instead of 48 degrees C) significantly decreased the production of these hydroxy fatty acids. Lowering the pH of the mash to inhibit lipoxygenase activity and preventing O2 uptake by the mash using carbon dioxide were also effective in reducing the amounts of these acids produced during mashing. From the viewpoint of industrial-scale beer production, the prevention of O2 uptake by the mash was selected as an appropriate method for reducing oxidation during wort production without affecting the subsequent brewing process or the taste of the finished beer. After introducing oxidation prevention procedures, the content of trihydroxyoctadecenoic acids decreased by about 30% and the foam stability and taste were improved in commercial products brewed using less than 25% malts.

Adsorption to or desorption of beer components from a lipid membrane related to sensory evaluation

The relationship between the adsorption to or desorption of beer from a lipid membrane and sensory evaluation was studied using a lipid-coated quartz crystal microbalance connected to a flow injection system. The adsorption and duration of adsorption of commercial beers showed a significant correlation with their body and smoothness in a sensory evaluation, respectively. Isohumulones, tartaric acid, NaCl, glutamic acid, and tannic acid were adsorbed onto the lipid membrane. Di- and trihydroxyoctadecenoic acids increased the duration of adsorption of the beer components onto the lipid membrane but not the extent of adsorption. They decreased the astringent duration of beer and the smoothness in the sensory evaluation but did not affect the intensity of bitterness or astringency or the body. It seems that this system, which modifies the electrostatic and hydrophobic interactions of the beer components with the tongue and throat surfaces, can mainly evaluate bitterness and/or astringency which significantly affect the body and smoothness of beer.

Flavonoid Glycosides Extracted from Hop (Humulus lupulus L.) as Inhibitors of Chemical Mediator Release from Human Basophilic KU812 Cells

The antiallergic properties of hop water extract (HWE) were studied by evaluating histamine release from human basophilic KU812 cells induced by calcium ionophore A23187. HWE significantly inhibited histamine release, but boiling water extract and chloroform–methanol extract did not show any inhibitory effect on it. A 50% methanol-eluted fraction separated from HWE by XAD-4 column chromatography (MFH) had a strong inhibitory effect as compared with HWE. Quercetin glycosides and kaempherol glycosides were identified in MFH, of which quercetin glycosides contributed to the inhibition of histamine release. Most quercetin in HWE existed in glycoside form and its quercetin content, obtained by acid hydrolysis, was about 200 μg/g. HWE and MFH significantly inhibited protein kinase C, which plays a pivotal role in the degranulation of chemical mediators. These results indicate that HWE can inhibit type-I allergic reactions.

Clinical Effects of a Hop Water Extract on Japanese Cedar Pollinosis during the Pollen Season: A Double-Blind, Placebo-Controlled Trial

The clinical effects of an oral administration of a hop water extract (HWE) on the improvement of Japanese cedar pollinosis (JCPsis) symptoms were investigated. In a double-blind, placebo-controlled trial, 39 subjects took a drink containing either 100 mg of HWE or a placebo for 12 weeks during the pollen season. Nasal symptoms (sneezing attacks, nasal discharge, and nasal obstruction) were assessed from the subjects’ diaries. A clinical examination and blood sampling were carried out before and 4, 8 and 12 weeks after the initiation of treatment. As a result, a significant difference was observed in the symptom score and in the symptom-medication score 10 weeks after the intervention in comparison with the placebo group. Improvements were observed in nasal swelling, nasal color, amount of nasal discharge, and characteristics of nasal discharge in the intervention group 12 weeks after the treatment. No significant eosinophil infiltration into the nasal discharge was apparent in the intervention group throughout the study period, although it was observed in the placebo group. These findings indicate that an oral administration of HWE may be effective in alleviating the allergic symptoms related to JCPsis.

Effect of Pitching Yeast and Wort Preparation on Flavor Stability of Beer

Abstract To confirm the role of fermentation conditions on flavor stability of beer and to brew a more stable beer, the effect of several fermentation conditions on the sulfite content in the finished beer and the flavor stability was studied using a pilot scale brewing process. Yeast strain significantly affected the sulfite content, chemiluminenscence (CL) production which serves as an index of the susceptibility of beer to staling, and flavor stability of the resulting beer. Lower dissolved oxygen in pitching wort, higher pitching rate of yeast and clearer pitching wort led to the higher level of sulfite content, the inhibition of CL production, and better flavor stability of the resulting beers. These fermentation conditions did not significantly injure the fermentation process and change the flavor character of the fresh beer with the exception of the yeast strain. It was, therefore, expected that the flavor stability of beer could be controlled by the fermentatiun conditions without harming the fermentation process and the flavor character of the fresh beer.

Role of fermentation conditions on flavor stability of beer

Abstract To clarify the role of wort fermentation conditions on the stability of the resulting beer, the flavor stability of beers brewed at several fermentation temperatures (6–30°C) in a pilot brewing plant (30 l) was studied using chemiluminescence analysis. Chemiluminescence (CL) production in fresh and stored beers increased with fermentation temperatures. Flavor stability of the beers increased with decreasing fermentation temperatures. Sulfite content in the fresh beer decreased with an increase in fermentation temperatures. When sulfite was added to beer, the CL production in beers before and after storage decreased and the flavor stability increased with the concentration of sulfite. These data showed that it was an advantage for beer flavor stability to increase the sulfite level during fermentation. In this pilot study, the CL producing activity had a negative relationship with sulfite content in beer and with flavor stability, indicating that the CL producing pattern of beer is useful indicator for the evaluation of beer stability in the development of a more stable beer.

Effects of a Hop Water Extract on the Compound 48/80-Stimulated Vascular Permeability in ICR Mice and Histamine Release from OVA-Sensitized BALB/c Mice

The antiallergic properties of a hop water extract (HWE) were studied by evaluating the Evans blue leakage from ICR mice caused by compound 48/80 stimulation, and the histamine release from ovalbumin (OVA)-sensitized BALB/c mice. An oral administration of HWE significantly inhibited the vascular permeability and histamine release. HWE itself did not have any influence on the total and antigen-specific immunoglobulin E (IgE) production in OVA-sensitized mice. These results indicate that HWE exerted an antiallergic effect by inhibiting the release of chemical mediators from mast cells and basophiles.

Characterization of 9-fatty acid hydroperoxide lyase-like activity in germinating barley seeds that transforms 9(S)-hydroperoxy-10(E),12(Z)-octadecadienoic acid into 2(E)-nonenal.

Previously, we reported that 2(E)-nonenal, having a low flavor threshold (0.1 ppb) and known as the major contributor to a cardboard flavor (stale flavor) in stored beer, is produced by lipoxygenase-1 and a newly found factor named 9-fatty acid hydroperoxide lyase-like (9-HPL-like) activity in malt. To assess the involvement of 9-HPL-like activity in beer staling, we compared the values of the wort nonenal potential, an index for predicting the staleness of beer, with the lipoxygenase and 9-HPL-like activity of 20 commercial malts. There was a significant correlation between the malt 9-HPL-like activity and the values of wort nonenal potential (r=0.53, P<0.05), while the correlation between malt lipoxygenase activity and the wort nonenal potential was statistically insignificant. Analysis of the partially purified 9-HPL-like activity from embryos of germinating barley seeds indicated that 9-HPL-like activity consisted of fatty acid hydroperoxide lyase and 3Z:2E isomerase.