Characterization of Factors Involved in the Production of 2(E)-Nonenal during Mashing

Abstract

To characterize the factors involved in the production of volatile aldehydes during mashing, a model mashing experiment was done. After we inactivated the endogenous lipoxygenase (LOX) activity in the mash by mashing at 709 C for 30 min, further incubation with recombinant barley LOX-1 stimulated the accumulation of 2( E )-nonenal; however, this eŠect was signiˆcantly reduced by boiling the mash sample. The result suggests that both LOX-1 and a heat-stable enzymatic factor are involved in the production of 2( E )-nonenal during mashing. Malt contained fatty acid hydroperoxide lyase-like activity (HPL-like activity) that transformed 9-hydroperoxy-10( E ),12(Z )-octadecadienoic and 13-hydroperoxy-9(Z ),11( E )-octadecadienoic acid into 2( E )-nonenal and hexanal, respectively. Proteinase K sensitivity tests showed that they are distinct factors. 9-HPL-like activity survived through the mashing at 709 C for 30 min but was inactivated by boiling, suggesting it will be the heat-stable enzymatic factor found in the model mashing experiment.

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

“…Identification of OsHPL1 and OsHPL2 enabled a transgenic approach to analyze C 9 aldehydes in plant defensive reactions. In addition, since (2E)-nonenal is considered to be the aged flavor in cereal products, including rice and beer, 20,21) rice germplasms that lack OsHPL1 and/or OsHPL2 might contribute to the development of a new rice cultivar with improved food quality.…”

Rare allele of HvLox-1 associated with lipoxygenase activity in barley (Hordeum vulgare L.)

“…Barley HvLOX-1 involvement in lipid degradation and the formation of beer-deteriorating substances have been studied previously (Kuroda et al 2003). Furthermore, null LOX beer has become a highly desirable product, since it has significant stability of both flavor and foam, which allows the beer to remain fresh for longer.…”

“…In the lipid degradation pathway, the polyunsaturated fatty acid substrate is converted to 9-hydroperoxide (9-HPOD) and 13-hydroperoxide (13-HPOD) by the dioxygenase effect of lipoxygenase (Kuroda et al 2003; Kuroda et al 2005). Subsequently, 9-HPOD is converted to trans-2-nonenal (T2N) and trihydroxy octadecenoic acids (THODs) by HvHPL2 and its isoenzymes.…”

“…LOX-3 is considered irrelevant to beer quality given its low expression level in barley kernels and unclear product specificity (van Mechelen et al 1999). Collectively, LOX-1 is considered the main contributor to malt LOX activity (Doderer et al 1992; Kuroda et al 2003; Yang and Schwarz 1995). To date, several artificial and natural mutants of null LOX-1 activity have been screened out and used for the breeding of flavor-stable malting barley.…”

A method for production of γ-amino butyric acid (GABA) using barley bran supplemented with glutamate

“…The WGBB enables us easily to obtain wort with more GABA and higher quality in extract and total nitrogen. However, some components in barley grain or malt are negatively influenced on beer quality (Kobayashi et al, 2002;Kuroda, Furusho, Maeba, & Takashio, 2003). Therefore, in future work, detailed analysis of wort prepared using WGBB should be conducted.…”