Transcript 4 - UNH Lutein Lab - University of New Hampshire

Sulfur Fertility Influences Kale Flavor But Not Carotenoid Content
David Kopsell,1 Dean Kopsell,1 Joanne Curran-Celentano,2 William Randle,3 Timothy Coolong,3 & Carl Sams4
1Department
of Plant Biology, The University of New Hampshire, Durham, NH; 2Department of Animal and Nutritional Sciences, The University of New Hampshire, Durham, NH;
3Department of Horticulture, The University of Georgia, Athens, GA; 4The Department of Plant Sciences and Landscape Systems, The University of Tennessee, Knoxville, TN
Project Summary
Materials and Methods
Conclusions
Dietary intake of carotenoids has been associated with
reduced disease risk. Kale (Brassica oleracea L. Acephala
Group) has the highest reported levels of the carotenoids
lutein and -carotene. Brassica vegetables also contain
glucosinolate (GS) and S-methyl-cysteine sulfoxide (MCSO)
that produce bitter, acrid flavors which consumers find
objectionable. Therefore, the objective of this study was to
investigate the influence of sulfur (S) fertility level on GS,
MCSO, and carotenoid accumulation in kale.
Plant Culture
‘Winterbor’, ‘Redbor’, and ‘Toscano’ kale were
greenhouse grown (22C day/14C night) under
natural photoperiods (lat. 4309’N) in 30 L of a halfstrength modified Hoagland’s nutrient solution.
Plants were grown under increasing S treatment
concentrations at 4, 8, 16, 32, and 64 mg S·L-1.
The experimental design was a split-plot, with
S treatment as the main plot and kale cultivar as the
subplot. Each treatment consisted of 5 plants per
cultivar replicated four times.
Consumers often cite the bitter flavor of raw Brassica
vegetables as unpleasant or objectionable. It is important
to consider the sensory response to foods when
developing strategies aimed at improving dietary quality
(7).
Glucosinolate and MCSO Determination
Glucoiberin, glucobrassicin, neoglucobrassicin, 4methoxyglucobrassicin, and 4-hydroxyglucobrassicin
were extracted from freeze dried kale leaf tissue and
quantified using high performance liquid
chromatography (HPLC; 4). Methyl cysteine
sulfoxide concentration was determined from dried
kale leaf tissue using HPLC (5).
The goal of this
study was to
measure the effect
of S fertility on:
• GS
• MCSO
• Lutein
• -carotene
accumulation in the
leaf tissues of three
kale cultivars.
On-farm demonstration
of influence of S on kale
flavor at Roots & Fruits
Farm, Dalton, NH.
Sinigrin
Neoglucobrassicin
4-hydroxy-glucobrassicin
30
25
Understanding the combined impact of production
practices on flavor and nutrition may help improve
consumer acceptance of phytonutritionally-enhanced
vegetable crops.
16
14
12
10
8
4
20
8
16
32
Leaf Tissue Sulfur
48
Sulfur treatment (mg/L)
'Winterbor'
-carotene
'Redbor'
'Toscano'
16
32
2
18
16
14
12
10
1.6
1.2
0.8
0.4
0
8
4
4
8
16
32
48
Sulfur treatment (mg/L)
8
48
Sulfur treatment (mg/L)
15
10
Experimental Results
5
0
4
8
16
32
48
Sulfur treatment (mg/L)
Methyl-Cysteine Sulfoxide
'Winterbor'
mg/g dry tissue
Green leafy vegetables are rich in dietary carotenoids,
and kale (B. oleracea L. Acephala Group) ranks high in
lutein and -carotene content. Because GS and MCSO
S-containing compounds in B. oleracea can impart
negative flavor attributes, understanding how they can
be lowered is important for consumer acceptability.
Glucoiberin
mg/100 g dry tissue
Dietary intake of lutein, -carotene, and other
carotenoids has been associated with reduced risk of
lung cancer and chronic eye diseases, including
cataract and age-related macular degeneration (3).
Glucosinolates
'Toscano'
18
Carotenoid & Pigment Determination
Carotenoids were quantified from freeze dried tissue
according to the method of Beecher and Howard
(USDA Food Composition Laboratory, Beltsville,
MD; 6).
Carotenoid pigments protect photosynthetic plant
structures by dissipating excess light energy (1) and
binding singlet oxygen to inhibit oxidative damage (2).
Examples of carotenoids include lutein and -carotene.
'Redbor'
The lower S treatment levels reduced GS and MCSO
content in kale. This should decrease the bitter and
unpleasant flavors associated with eating raw Brassica.
Lowering S fertility did not affect lutein and -carotene
levels, thereby preserving the health benefits of
carotenoid consumption.
% Sulfur in leaves
Sulfur (S) may be incorporated into a wide range of
secondary plant compounds, such as glucosinolates
(GS) and S-methyl-cysteine sulfoxide (MCSO),
responsible for characteristic odors and flavors of
Brassica vegetables.
'Winterbor'
mg/100 g fresh tissue
Introduction
Lutein
mg/100 g fresh tissue
‘Winterbor’, ‘Redbor’, and ‘Toscano’ kale were greenhousegrown using nutrient solution culture with S treatments of 4, 8,
16, 32, and 64 mg S·L-1. Levels of GS and MSCO decreased
in response to decreasing S in nutrient solution. However,
accumulation of lutein and -carotene were unaffected by S
treatment. Lowering S fertility in the production of kale should
decrease the negative flavors associated with high levels of
GS and MCSO without affecting carotenoid pigments levels.
‘Toscano’ kale
growing at
UNH Research
Greenhouse.
'Redbor'
'Toscano'
6
5
Sulfur Compounds
Percent S in kale leaf tissue increased linearly in
response to increasing S treatment. In general, the
concentration of most GS compounds decreased in
response to decreasing S treatments.
Methyl-cysteine sulfoxide decreased linearly in all
the cultivars in response to decreasing S availability.
Decreases in GS and MCSO compounds paralleled
decreases in leaf tissue %S.
Carotenoid Compounds
Lutein and -carotene pigments did not change in
response to decreasing S concentrations in nutrient
solutions. Values for lutein and -carotene were
within previously reported ranges for field grown
kale.
4
3
2
1
0
4
8
32
16
Sulfur treatment (mg/L)
48
Lower S fertility in kale production would provide
more palatable raw produce, while still providing
beneficial dietary lutein and -carotene.
Literature Cited
(1) Frank, H.A.; Cogdell, R.J. Carotenoids in photosynthesis. Photochem. Photobiol.
1996, 63, 257-264.
(2) Tracewell, C.A.; Vrettos, J.S.; Bautista, J.A.; Frank, H.A.; Brudvig, G.W.
Carotenoid photooxidation in photosystem II. Arch. Biochem. Biophysic. 2001,
385, 61-69.
(3) Le Marchand, L.; Hankin, J.H.; Kolonel, L.N.; Beecher, G.R.; Wilkens, L.R.; Zhao,
L.P. Intake of specific carotenoids and lung cancer risk. Cancer Epidemiol.
Biomarkers Prev. 1993, 2, 183-187.
(4) Hansen, M.; Møller, P.; Sørensen, H.; M. Cantwell de Trejo. Glucosinolates in
broccoli stored under controlled atmosphere. J. Amer. Soc. Hort. Sci. 1995, 120,
1069-1074.
(5) Edwards, S.J.; Musker, D.; Collin, H.A.; Britton, G. The analysis of the S-alk(en)ylL-cysteine sulphoxides (flavour precursors) from species of Allium by high
performance liquid chromatography. Phytochem. Anal. 1994, 5, 4-9.
(6) Khachik, F.; Beecher, G.R.; Whittaker, N.F. Separation, identification, and
quantification of the major carotenoid and chlorophyll constituents in extracts of
several green vegetables by liquid chromatography. J. Agr. Food Chem. 1986, 34,
603-616.
(7) Drewnowski, A. Taste preferences and food intake. Annu. Rev. Nutr. 1997, 17,
237-253.
Acknowledgements
This project was funded in part by the Cooperative State Research, Education,
and Extension Service, U.S. Department of Agriculture, under agreement No.
2001-52102-11254. This research has been accepted for publication by the
Journal of Agricultural and Food Chemistry from the American Chemical Society.