Bitter-Tasting Sake Peptides Derived from the N-Terminus of the Rice Glutelin Acidic Subunit

Abstract

Five bitter-tasting peptides were isolated from charcoal-untreated sake, following a Sepabeads resin separation, an initial reverse-phase chromatography (RP-HPLC), a gel permeation-chromatography, and a second RP-HPLC. The isolated peptides consisted of six to thirteen amino acid residues. The N-termini were uniformly pyroglutamate residues. Based on the rice protein database, the peptides were derived from two di#erent N-termini of the rice glutelin acidic subunit. One of them was reported as a prolyl endopeptidase inhibitor. The thirteen amino acid peptides in charcoal-untreated ginjyo-type sakes were lower than that in charcoal-untreated jyunmai-type sakes. The thirteen amino acid peptides were not detected in the commercial ordinary-type sake analyzed. The concentration of analyzed peptides of nine to thirteen amino acid residues in charcoal-untreated sake exceeded their preliminary estimated sensory threshold values, suggesting that they contribute to the sensory quality of charcoal-untreated sake.

Identification of Low Molecular Weight Peptides in Chinese Rice Wine (Huang Jiu) by UPLC-ESI-MS/MS

“…A large number of the peptides identified in this experiment presented a higher hydrophobicity (Bull+Breese value, data not shown) that is closely related to the bitterness of peptides 23 , which indicates that they may exhibit a potential bitter taste. However, the five bitter-taste peptides reported by Hashizume et al 10 were not found in this experiment, possibly because the Chinese rice wine (Huang Jiu) was produced using significantly different materials, microorganisms and wine-making technology or for other unknown reasons compared with sake. However, the ACE-active peptides, VY and YW, were found in this experiment as also reported by Saito et al 31 who had screened for them and found them in sake and sake lees.…”

“…Hofmann's research group has found many key bitter and kokumi peptides in Gouda cheeses and edible beans 7,34,35 . Hashizume et al 10 reported that five peptides isolated from sake presented the unpleasant taste with an accompanying bitter taste.…”

“…In addition, they also contribute to the sensory characteristics of foodstuffs, because of their involvement in the development of sweet, sour, bitter and umami tastes 10,14 . Hofmann's research group has found many key bitter and kokumi peptides in Gouda cheeses and edible beans 7,34,35 .…”

Bitter peptides and bitter taste receptors

“…A wide variety of peptides derived from proteins have been found in various foodstuffs and fermentation products, such as miso (salted and fermented soybean paste) [18], soy sauce [19,20], fish sauce [21], natto (fermented soybeans) [22], katsuobushi (dried fish flakes) [23], cheese [24 -27], and sake [28,29]. Hydrolysis of proteins by proteolytic enzymes is also usually accompanied by the formation of a bitter taste [30 -33].…”

Late-maturing cooking riceSensyurakuhas excellent properties, equivalent to sake rice, for high-quality sake brewing

“…Especially, a low protein content is an important feature for high-quality sake brewing, because an excess amount of proteins (amino acids) causes a rough taste and deepening of the color of the refined sake, which are negative factors in terms of sensory evaluation. [1][2][3] Furthermore, the aroma of sake containing a high content of amino acids appears to deteriorate during storage. 1) As the germ and the surface fraction of the rice grain are abundant in proteins and lipids, the rice used for high-quality sake brewing is highly polished to reduce these negative factors for sake taste.…”