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Reduction of off-flavor generation in soybean homogenates: a mathematical model.

Mellor N, Bligh F, Chandler I, Hodgman C - J. Food Sci. (2010)

Bottom Line: Time-course simulations of LOX- beans were run and compared with experimental results.Model L(2), L(3), and L(12) beans were within the range relative to the wild type found experimentally, with L(13) and L(23) beans close to the experimental range.Sensitivity analysis indicates that reducing the estimated K(m) parameter for LOX isozyme 3 (L-3) would improve the fit between model predictions and experimental results found in the literature.

View Article: PubMed Central - PubMed

Affiliation: CPIB, Multidisciplinary Centre for Integrative Biology, School of Biosciences, the Univ. of Nottingham, Sutton Bonington Campus, LE12 5RD, UK.

ABSTRACT

Unlabelled: 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- beans were run and compared with experimental results. Model L(2), L(3), and L(12) beans were within the range relative to the wild type found experimentally, with L(13) and L(23) beans close to the experimental range. Model L(1) beans produced much more n-hexanal relative to the wild type than those in experiments. Sensitivity analysis indicates that reducing the estimated K(m) 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.

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Comparison of model n-hexanal concentration for (A) various simulated  beans and (B) experimentally obtained results (Matoba and others 1985a), in which no standard errors were given.
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fig03: Comparison of model n-hexanal concentration for (A) various simulated beans and (B) experimentally obtained results (Matoba and others 1985a), in which no standard errors were given.

Mentions: Using the estimate of initial free LA of 67 nmol/mL, estimated using the value of 10 to 20 μmol/mL protein content given by Matoba and others (1985a) results in a model prediction of around 50 nmol/mL n-hexanal produced by wild-type beans. The value given in the paper is around 0.3 nmol/mL for wild-type Suzuyakata beans, more than a 10-fold decrease. This may be due to the degradation of free LA by other pathways, or an overestimation of initial LA or LOX concentrations. In order to compare the relative n-hexanal generation for different bean types between model and experimental data, the data were therefore plotted relative to the maximum wild-type value for both model predictions and experimental data, respectively. Figure 3A shows the comparison between different simulated LOX- beans, and Figure 3B shows the experimental results (taken directly from the paper itself, which gives no standard errors and a pH range of 6.5 to 7.0). Comparing the overall pattern of the results, some correlation is observed. The L13 (L-2 ) beans show clearly the lowest generation of n-hexanal in both model and experiment, with 0.4 and 0.6 times the peak wild-type value, respectively. The experimental data then show (in order of increasing peak n-hexanal) the L23, the L123 (wild type), and the L12 beans steadily increasing from an initial value to a peak after 60 min of around 0.8 (L23) and 1.2 (L12) times the peak wild-type value. The model predicts a similar order, with L12 beans producing slightly more n-hexanal than the wild type, and L23 slightly less, although the difference between the 3 curves appears smaller. There are 2 main qualitative differences between the experimental and model datasets. The 1st is the curves representing the L2 beans. Experimentally, these beans consistently produced the most n-hexanal throughout the time course, reaching a maximum value of around 1.8 times the wild-type value after 60 min. In contrast, in the model, while the peak value for L2 is still the highest predicted, it is much closer to the values predicted for the L12, wild type, and L13 beans, and for much of the time course, the predicted n-hexanal is lower than that of other beans. The experimental data for all beans show an initial base level of n-hexanal that is not accounted for in the model. For simplicity, initial n-hexanal concentration is set to zero in the model, but the experimental data give a mean initial concentration of around 0.14 times peak wild-type n-hexanal or 0.4 nmol/mL. In addition, Table 3 shows that in experiments where beans with none of the LOX isozymes present (L0), n-hexanal is still generated in concentrations comparable to the beans L1 and L3. It is possible that this is a steady state value of n-hexanal concentration prior to homogenization, when LA and LOX are isolated. After homogenization, LA and LOX are mixed, with the end result that n-hexanal concentration increases. Alternatively, there may be another metabolic pathway by which n-hexanal is generated.


Reduction of off-flavor generation in soybean homogenates: a mathematical model.

Mellor N, Bligh F, Chandler I, Hodgman C - J. Food Sci. (2010)

Comparison of model n-hexanal concentration for (A) various simulated  beans and (B) experimentally obtained results (Matoba and others 1985a), in which no standard errors were given.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2992688&req=5

fig03: Comparison of model n-hexanal concentration for (A) various simulated beans and (B) experimentally obtained results (Matoba and others 1985a), in which no standard errors were given.
Mentions: Using the estimate of initial free LA of 67 nmol/mL, estimated using the value of 10 to 20 μmol/mL protein content given by Matoba and others (1985a) results in a model prediction of around 50 nmol/mL n-hexanal produced by wild-type beans. The value given in the paper is around 0.3 nmol/mL for wild-type Suzuyakata beans, more than a 10-fold decrease. This may be due to the degradation of free LA by other pathways, or an overestimation of initial LA or LOX concentrations. In order to compare the relative n-hexanal generation for different bean types between model and experimental data, the data were therefore plotted relative to the maximum wild-type value for both model predictions and experimental data, respectively. Figure 3A shows the comparison between different simulated LOX- beans, and Figure 3B shows the experimental results (taken directly from the paper itself, which gives no standard errors and a pH range of 6.5 to 7.0). Comparing the overall pattern of the results, some correlation is observed. The L13 (L-2 ) beans show clearly the lowest generation of n-hexanal in both model and experiment, with 0.4 and 0.6 times the peak wild-type value, respectively. The experimental data then show (in order of increasing peak n-hexanal) the L23, the L123 (wild type), and the L12 beans steadily increasing from an initial value to a peak after 60 min of around 0.8 (L23) and 1.2 (L12) times the peak wild-type value. The model predicts a similar order, with L12 beans producing slightly more n-hexanal than the wild type, and L23 slightly less, although the difference between the 3 curves appears smaller. There are 2 main qualitative differences between the experimental and model datasets. The 1st is the curves representing the L2 beans. Experimentally, these beans consistently produced the most n-hexanal throughout the time course, reaching a maximum value of around 1.8 times the wild-type value after 60 min. In contrast, in the model, while the peak value for L2 is still the highest predicted, it is much closer to the values predicted for the L12, wild type, and L13 beans, and for much of the time course, the predicted n-hexanal is lower than that of other beans. The experimental data for all beans show an initial base level of n-hexanal that is not accounted for in the model. For simplicity, initial n-hexanal concentration is set to zero in the model, but the experimental data give a mean initial concentration of around 0.14 times peak wild-type n-hexanal or 0.4 nmol/mL. In addition, Table 3 shows that in experiments where beans with none of the LOX isozymes present (L0), n-hexanal is still generated in concentrations comparable to the beans L1 and L3. It is possible that this is a steady state value of n-hexanal concentration prior to homogenization, when LA and LOX are isolated. After homogenization, LA and LOX are mixed, with the end result that n-hexanal concentration increases. Alternatively, there may be another metabolic pathway by which n-hexanal is generated.

Bottom Line: Time-course simulations of LOX- beans were run and compared with experimental results.Model L(2), L(3), and L(12) beans were within the range relative to the wild type found experimentally, with L(13) and L(23) beans close to the experimental range.Sensitivity analysis indicates that reducing the estimated K(m) parameter for LOX isozyme 3 (L-3) would improve the fit between model predictions and experimental results found in the literature.

View Article: PubMed Central - PubMed

Affiliation: CPIB, Multidisciplinary Centre for Integrative Biology, School of Biosciences, the Univ. of Nottingham, Sutton Bonington Campus, LE12 5RD, UK.

ABSTRACT

Unlabelled: 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- beans were run and compared with experimental results. Model L(2), L(3), and L(12) beans were within the range relative to the wild type found experimentally, with L(13) and L(23) beans close to the experimental range. Model L(1) beans produced much more n-hexanal relative to the wild type than those in experiments. Sensitivity analysis indicates that reducing the estimated K(m) 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.

Show MeSH