Genetic determinants of glucosinolate degradation during food processing in Brassica oleracea
Supervisors:Dr. Ing. R. Verkerk (PDQ)
Dr. Ir. M. Dekker (PDQ)
Dr. Ir. G. Bonnema (Plant Breeding)
Dr.ir. M. A.J. S van Boekel (PDQ)
February 2009 – February 2013
Royal Dutch Academy of Sciences (KNAW)
Nowadays there is growing awareness of nutritionists, food scientists, food industry and consumers on the relation between health and diet. Brassica vegetables have shown negative associations between the consumption and colon cancer risk in men and women. The protected effects of Brassicacea are ascribed to high levels of some glucosinolates (GLs). Various steps in the food production chain have a wide influence on the levels and bioavailability of these phytochemicals. In the cultivation stage genetic and environmental factors contribute significantly to the variation in GL levels. The following steps in the food production chain are storage and processing, which affect the cellular integrity and may result in GL degradation. Furthermore it was shown that thermal stability varies for different GLs and for different vegetable types (1).
AimThe aim of this thesis is to reveal genetic factors, which determine GL degradation. Possible influencing factors are morphological and biochemical traits, which are genetically determined. The objective of the research are:
- establishing genetic role in GL degradation;
- identification responsible QTL’s on genome;
- assessing biochemical factors that play a role in thermal degradation of GL
ResearchThe determination of the GL determination has been improved to analyse GLs with high throughput (2).
To determine the genetic role of thermal GL degradation, a public segregating doubled-haploid (DH) population developed by crossing broccoli and Chinese kale was used to study thermal stability of GLs. After harvesting of the leaves, the endogenous enzyme myrosinase, which hydrolyses GLs, was inactivated. Subsequently, heat treatment was performed over various times and the GL concentration were measured. It was shown on the parental lines that modelling with a first order kinetics is appropriate to estimate rate constants for the degradation speed (kd values) independently from the growing season. The degradation of structurally the same GLs did not differ between the parental lines, but was highly affected by the growing season (3).
The kd values for GL degradation were determined for each line of the DH population which were used to conduct quantitative trait loci (QTL) analysis. QTLs are regions within genomes that contain genes associated with a particular quantitative trait. QTLs could be identified on chromosome 9 and 7 for glucobrassicin (indolic GL) and on chromosome 9 for glucoraphanin (aliphatic GL). These results show, that thermal GL degradation is (partly) genetically regulated.
It is hypothesized that biochemical traits influence the thermal GL degradation and hence are the traits underlying the identified QTLs. A following metabolite analysis of the plant material and a correlation with GL degradation parameters could reveal these factors.
publications1. Dekker, M., Verkerk, R., and Hennig, K. (2009) Czech J. Food Sci. 27, 85-88
2. Hennig, K., Verkerk, R., Bonnema, G., and Dekker, M. (submitted ) Food Chem.
3. Hennig, K., Verkerk, R., Bonnema, G., and Dekker, M. (submitted Jan. 2012) J. Agric. Food Chem.