Abstract
Consumption of glucosinolate-rich Brassicales vegetables is associated with a decreased risk of cancer with enzymatic hydrolysis of glucosinolates playing a key role. However, formation of health-promoting isothiocyanates is inhibited by the epithiospecifier protein in favour of nitriles and epithionitriles. Domestic processing conditions, such as changes in pH value, temperature or dilution, might also affect isothiocyanate formation. Therefore, the influences of these three factors were evaluated in accessions of Brassica rapa, Brassica oleracea, and Arabidopsis thaliana. Mathematical modelling was performed to determine optimal isothiocyanate formation conditions and to obtain knowledge on the kinetics of the reactions. At 22 °C and endogenous plant pH, nearly all investigated plants formed nitriles and epithionitriles instead of health-promoting isothiocyanates. Response surface models, however, clearly demonstrated that upon change in pH to domestic acidic (pH 4) or basic pH values (pH 8), isothiocyanate formation considerably increases. While temperature also affects this process, the pH value has the greatest impact. Further, a kinetic model showed that isothiocyanate formation strongly increases due to dilution. Finally, the results show that isothiocyanate intake can be strongly increased by optimizing the conditions of preparation of Brassicales vegetables.
Highlights
Harmful effects, especially in animal nutrition[15]
We evaluated whether the hydrolysis process of GLS in Brassica vegetables can be modified by dilution with water, artificial saliva or heat-treated plant homogenate, e.g. by changing the concentration of GLS, myrosinase and specifier proteins present in the environment during GLS hydrolysis
In addition to quantification of the GLS breakdown products under the different pH, temperature and dilution conditions, the plant materials were evaluated for their GLS content, myrosinase activity, epithiospecifier protein (ESP) activity and l-ascorbic acid content
Summary
Harmful effects, especially in animal nutrition[15]. in respect to a healthy human diet, it is of great interest to provide food rich in ITCs with low levels of nitriles and EPTs. The aim of the present study was to evaluate the effect of (1) “refrigerator” (4 °C), ambient (22 °C) and “chewing” temperature (37 °C) as well as (2) acidic (pH 4), medium (pH 6) and slightly basic pH values (pH 8), that are relevant for food preparation, on the profile of enzymatic breakdown products of GLS in selected Brassica vegetables For this purpose, Brassica rapa and Brassica oleracea were compared to the model plant A. thaliana. Alba) were evaluated since they differ in their GLS profile compared to BroccoCress The results of these studies were modelled, in order (1) to determine the impact of pH, temperature and dilution and to compare the various species belonging to the Brassicaceae family as regards their GLS metabolism as well as (2) to obtain knowledge on the kinetics of the hydrolysis and breakdown reactions as a first step in optimizing ITC formation, and intake, during the food preparation process
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