Development of vegetables with improved consumer quality : a case study in Brussels sprouts

J.E. van Doorn

Research output: Thesisinternal PhD, WU

Abstract

<p>In the last decade the vegetable production chain has changed from being production- driven into customer-driven, with special attention for consumer preferences. The current consumers want vegetables with additional value and demand convenient healthy vegetables with improved flavour and nutritional value.</p><p>The vegetable business chain has only partly anticipated to these new consumer demands due to practical limitations. For many crops, information with respect to relationships between quality traits and consumer satisfaction and their expression in the crop germplasm is not available, mainly due to a lack of consumer preference mapping, reliable assays for quality related traits and the recognition of quality produce in the business chain.</p><p>The members of the business chain can currently only partially can fulfill consumers wishes by means of branding of vegetables with specifications for freshness, uniformity, storability and production conditions but have no clear solution for the supply of vegetables with improved flavour, health-promoting activity or nutritional value.</p><p>In the thesis the development of Brussels sprouts with an optimal is described and methods to facilitate their production. Flavour of Brussels sprouts is determined by the glucosinolates sinigrin and progoitrin, sulphur-containing bitter glycosides as intact compounds or after enzymatic degradation. The development of tasty sprouts was initiated with the development of novel, large-scale assays for the determination of sinigrin, progoitrin and the sum of glucosinolates in Brussels sprouts.</p><p>Two specific ELISA assays created the possibility to screen the content of respectively sinigrin and progoitrin in parental lines and F1-hybrids of the breeding program on a large scale. The assay for the sum of glucosinolates was developed to avoid the time-consuming removal of glucose from Brussels sprouts samples by chromatography. In the new method glucose is removed by enzymatic degradation instead of chromatography.</p><p>The ELISAs for sinigrin and progoitrin and the assay for the sum of glucosinolates have been used to define the optimal variation in the content of glucosinolates in the breeding program of Brussels sprouts for the purpose of consumer preference studies. Multiple taste trials with consumers and experts have demonstrated that Brussels sprouts with a sum of sinigrin and progoitrin below 2.2 g kg <sup>-1</SUP>are appreciated by regular consumers. Sprouts with a sum of sinigrin and progoitrin below 0.6 g kg <sup>-1</SUP>are appreciated as non-bitter and in principle suitable for consumers who dislike bitterness.</p><p>The critical level of sinigrin and progoitin for consumer preference (2.2 g kg <sup>-1</SUP>) and minimum bitterness (0.6 g kg <sup>-1</SUP>) have been used as norms for the breeding of Brussels sprouts with improved flavour. The sinigrin and progoitrin of Brussels sprouts is determined for 60% by genotype and for 40% by growth conditions. The sinigrin and progoitrin content of Brussels sprouts varieties inherits proportionally to that of their corresponding parental lines with narrow-sense heritability values of 0.72 and 1.09 respectively. Selection pressure for a low sinigrin and progoitrin content has, remarkably, resulted in a low sum of both glucosinolates but not in a low relative level in the sum of glucosinolates. The assortment of F1-hybrids with a poor flavour has been replaced with tasty varieties in the past 10 years.</p><p>The significant influence of environmental conditions on the sinigrin and progoitrin content of varieties, and with that on flavour, was the reason for their further definition. It is impossible to produce Brussels sprouts with a predictable flavour when environmental factors with an influence on the glucosinolate content are not properly controlled. Rainfall, the soil sulphate concentration and the architecture of the root system have been characterized as the main parameters that influence the variation in the sinigrin and progoitrin content of Brussels sprouts varieties. The sum of sinigrin and progoitrin is highly correlated with the cumulative lateral root length, probably because this parameter is related with the sulphate uptake capacity of root systems. Armed with this knowledge, sprouts can be produced with a predictable glucosinolate content and an optimal flavour in the uncontrolled environment of farmers' fields.</p><p>Brussels sprouts are an example of a vegetable with a short shelf life because of their fast deterioration after harvest. Improvement of the shelf life of Brussels sprouts in the business chain would greatly improve the freshness and attractiveness for consumers.</p><p>In the thesis a Brussels sprout line is described and characterized with extended shelf life at room temperature. The expression of the trait is based on a complex interaction between the auxin and cytokinin metabolism, which in concert are responsible for a low ethylene production and an inhibited senescence process. The genitor for long shelf life can be used for multiple purposes but primarily could revolutionize the storability of harvested Brussels sprouts. The proper expression of the trait will result in enhancement of the post harvest shelf life from five days to two weeks. During the senescence process of sprouts, glucosinolates are degraded into compounds with enhanced bitterness such as goitrin. The shelf life genitor is expected to inhibit this post-harvest development of bitterness.</p><p>The methods developed in this thesis, the definitions of optimal flavour and bitterness, cultivars with good flavour (and in the near future storability), and recommendations for the production of tasty sprouts are a solid basis for the marketing and sales of sprouts with a reliable flavour for the members of the vegetable business chain. The definition and development of this knowledge is the responsibility of breeding companies, the branding and sales of tasty sprouts is a task for the other members of the business chain. The branding of tasty Brussels sprouts is an ideal test case to see whether the sales of vegetables with improved expression of consumer quality traits has a future in the business chain especially because the sales of sprouts has been under pressure in the last decade due to poor flavour.</p><p>The successful introduction of tasty sprouts on the market might accelerate the entry of other important quality traits in other crops. However, breeding companies will consider developments in the field of consumer quality trait breeding more carefully in the case of a lack of success. The results of this thesis have clearly demonstrated that breeding of crops with high internal quality is achievable.</p>
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
Supervisors/Advisors
  • Jongen, W.M.F., Promotor, External person
  • van der Plas, L.H.W., Promotor, External person
Award date29 Sep 1999
Place of PublicationS.l.
Print ISBNs9789058081223
Publication statusPublished - 1999

Keywords

  • brussels sprouts
  • consumer preferences

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