Abstract
The generation of off-flavors in soybean homogenates such as n-hexanal via the lipoxygenase (LOX) pathway can be a problem in the processed food industry. Previous studies have examined the effect of using soybean varieties missing one or more of the 3 LOX isozymes on n-hexanal generation. A dynamic mathematical model of the soybean LOX pathway using ordinary differential equations was constructed using parameters estimated from existing data with the aim of predicting how n-hexanal generation could be reduced. Time-course simulations of LOX-null beans were run and compared with experimental results. Model L2, L3, and L12 beans were within the range relative to the wild type found experimentally, with L13 and L23 beans close to the experimental range. Model L1 beans produced much more n-hexanal relative to the wild type than those in experiments. Sensitivity analysis indicates that reducing the estimated Km parameter for LOX isozyme 3 (L-3) would improve the fit between model predictions and experimental results found in the literature. The model also predicts that increasing L-3 or reducing L-2 levels within beans may reduce n-hexanal generation.Practical Application: This work describes the use of mathematics to attempt to quantify the enzyme-catalyzed conversions of compounds in soybean homogenates into undesirable flavors, primarily from the compound n-hexanal. The effect of different soybean genotypes and enzyme kinetic constants was also studied, leading to recommendations on which combinations might minimize off-flavor levels and what further work might be carried out to substantiate these conclusions.
Highlights
The generation of off-flavors in soybean homogenates such as n-hexanal via the lipoxygenase (LOX) pathway can be a problem in the processed food industry
The preferred substrate of Hydroperoxide Lyase (HPL), 13HOD-S(Z,E), was modeled in the step of the LOX pathway, and so the relative concentrations in which it is formed in different bean genotypes are significant
The L-2 isozyme (L2) beans formed the most 13HOD-S(Z,E), closely followed by the L12, L23, and L123(wild type) beans, at around one-third lower concentrations the L1 beans, the L13 beans, and the L3 beans producing by far the lowest concentration
Summary
The generation of off-flavors in soybean homogenates such as n-hexanal via the lipoxygenase (LOX) pathway can be a problem in the processed food industry. It is believed that certain specific 13-hydroperoxide isomers formed go on to in many plants the off-flavors are generated by a range of aldehy- be cleaved by hydroperoxide lyase, a CYP74, to form n-hexanal des known as C6-aldehydes or green leaf volatiles (GLVs) (Matsui and 12-oxo-(Z)-9-dodecenoic acid (Matoba and others 1985b; 2006; Pulvera and others 2006). These GLVs are generated by the Pulvera and others 2006). Authors Mellor and trations of n-hexanal following homogenization (Takamura and others 1991; Zhuang and others 1991; Nishiba and others 1995) From some of these studies, kinetic parameters can be derived that can be used to model the biological system mathematically
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