seasonal climate effects on root colour and compounds of red radish

Seasonal climate effects on root colour andcompounds of red radishM Schreiner,1* S Huyskens-Keil,2 P Peters,1 I Schonhof,1 A Krumbein1 and S Widell11Institute of Vegetable and Ornamental Crops Großbeeren/Erfurt eV, Theodor-Echtermeyer-Weg 1, D-14979 Großbeeren, Germany2Humboldt-University Berlin, Institute for Horticultural Sciences, Section Quality Dynamics/Postharvest Physiology, Lentzeallee 75,D-14195 Berlin, Germany

Abstract: ‘Nevadar’ radishes were grown throughout the year. Climate parameters (mean

temperature, mean irradiation) and quality characteristics of radishes fulfilling consumer quality

requirements, such as root colour, glucosinolates, monosaccharides and pectic substances, were

determined. The quality characteristics strongly differed depending on the seasonal climate

conditions. The seasonal dependence ranged from a slight climate influence (alkenyl glucosinolates

r2=0.23), over a moderate climate effect (indolyl glucosinolates r2=0.40, glucose r2=0.50) up to a

strongly distinctive climate influence (hue angle r2=0.77, chroma r2=0.72, fructose r2=0.81, pectic

substances r2=0.99). Therefore, according to consumer-oriented quality production of radish, the

temperature and irradiation influence should be taken into account in the production process.

Recommendations for quality production of radish will be the selection of bright red cultivars marked

by a high photosynthetic capacity (yield>0.80mV) at relatively low mean irradiation intensities

(50–100mmol m2s�1) and lower mean temperatures (11–13°C). Thus sufficient photochemical energy

can be provided for the synthesis of quality-determining compounds. For the production of bioactive

radishes showing particularly relatively high contents of indolyl glucosinolates, cultivation should be

carried out in spring and autumn. In summer cultivation, consumer preferences in taste can

particularly be satisfied with the desired contents of alkenyl glucosinolates and monosaccharides.

# 2002 Society of Chemical Industry

Keywords: seasonal climate effects; temperature; photosynthetic photon flux density; colour; carbohydrates;glucosinolates; pectic substances; radish; Raphanus sativus L var sativus

INTRODUCTIONThe national and international market is characterised

by surplus production of vegetable products, resulting

in strong competition. Only those products that fulfil

consumer quality requirements have good sales poten-

tial.1 Therefore, regarding customer-oriented quality

production, one has to decisively determine:

. the quality characteristics of a vegetable product

that meet customer expectations;

. the parameters influencing these quality characteris-

tics.

In terms of consumer preference, root colour is one

of the main quality characteristics of radish and is

regarded as an indicator of radish quality. Hence

product colour strongly affects consumer perception

of quality and is one of the major characteristics in

making purchasing decisions on fresh vegetables.2–5

This is also valid for radish roots. A consumer

acceptance test in Germany (Berlin and Brandenburg)

showed that consumers preferred bright-reddish

radishes. Moreover, these investigations revealed that

taste and texture of the radish roots are also essential

quality attributes for consumers.6 Therefore, in the

present study, root colour and taste- and texture-

determining quality characteristics of radishes, such as

glucosinolates, monosaccharides and pectic sub-

stances, were analysed owing to their sensory impor-

tance. According to Widell et al,7 glucosinolates

provide mainly the taste and aftertaste attributes

‘pungent’, ‘intensive’ and ‘burning’. The monosac-

charides glucose and fructose also influence the taste

attribute ‘intensive’. In addition, the mouthfeel im-

pression ‘firm’ is predominantly determined by pectic

substances.8

Radishes are grown throughout the year under

varying climate conditions.9 Thus an understanding

of the climate factors modulating radish root colour

and composition during the production process is

essential for total quality management aiming at

consumer-oriented radish quality.

The objectives of these investigations were:

. the determination of seasonal effects, with special

emphasis on the effects of temperature and photo-

(Received 23 July 2001; accepted 24 April 2002)

* Correspondence to: M Schreiner, Institute of Vegetable and Ornamental Crops Großbeeren/Erfurt eV, Theodor-Echtermeyer-Weg 1,D-14979 Großbeeren, GermanyE-mail: [email protected]

# 2002 Society of Chemical Industry. J Sci Food Agric 0022–5142/2002/$30.00 1325

Journal of the Science of Food and Agriculture J Sci Food Agric 82:1325–1333 (online: 2002)DOI: 10.1002/jsfa.1189

synthetic photon flux density, on radish root colour

and texture- and taste-influencing compounds;

. the development of recommendations for radish

production characterised by consumer-oriented

quality.

MATERIALS AND METHODSPlant materialBased on the results of the consumer acceptance test

of radishes in Germany,6 radishes of the cultivar

‘Nevadar’ with the preferred bright red colour served

as investigation material. This cultivar forms a red,

round tuber consisting mainly of a thickened hypoco-

tyl. In this paper the term root is used as it is generally

done in the horticultural literature. The plant material

originated from 10 growth sets (Table 1). From

November until March the radishes were cultivated

in the greenhouse; from April until October they were

field grown. Fertilisation, irrigation and plant protec-

tion corresponded to standard cultivation procedures

for radishes.

The developmental stage influences the content of

glucosinolates,10 pectic substances11 and monosac-

charides.12 Thus the radishes were harvested in a

narrow range of physiological development marked by

the BBCH stages 41–43. The BBCH stages are

defined according to Bleiholder et al,13 where the first

number of the digit code describes the principal

growth stage (1–9), ie the number 4 representing the

growth stage ‘development of harvestable vegetative

plant parts’. The second number characterises the

secondary growth stage; for example, the number 5

means that 50% of the expected root diameter is

developed.

The radishes were harvested according to German

quality standards for radishes14 and selected for

uniformity of root diameter (BBCH 41: 22�1mm;

BBCH 43: 24�1mm), root shape (round, not oval)

and visual appearance (freedom from defects and

disorders).

Climate parametersAs climate parameters, the mean temperature and

mean photosynthetic photon flux density (PPFD)

were determined 12 times per hour and summarised as

means over the production period (Fig 1). Summaris-

ing the values of mean temperature and mean PPFD

as mean values over the last week or the last 2 weeks

before harvest respectively showed the same tendency

as the summarised values over the entire production

period. Therefore, for characterising the seasonal

climate influence preharvest on the colour and

compounds of ‘Nevadar’ radish, only the mean values

over the entire production period were used.

Determination of quality characteristicsFor determining the seasonal climate effects on radish

root quality, the root colour and important sensory

quality characteristics such as glucosinolates, mono-

saccharides and pectic substances were measured and

analysed at harvest. According to Schouten et al,15 thechlorophyll fluorescence values characterises the effi-

ciency of photosystem II and therefore the energy

supply of the plant as prerequisite for the synthesis of

compounds. Hence the determination of compound

Table 1. Dates of sowing and harvest, harvest parameters and investigated characteristics of ‘Nevadar’ radish

Growth

set Sowing date Harvest date

BBCH

stage

Diameter

(mm) Investigated characteristics

1 16 Dec 1997 6 Feb 1998 43 24�1 Glucosinolates, monosaccharides, colour, chlorophyll fluorescence

2 27 Jan 1998 23 Mar 1998 43 24�1 Glucosinolates, monosaccharides, colour, chlorophyll fluorescence

3 11 Mar 1998 22 Apr 1998 43 24�1 Glucosinolates, monosaccharides, pectic substances, colour

4 8 Apr 1998 11 May 1998 43 24�1 Glucosinolates, monosaccharides, colour, chlorophyll fluorescence

5 6 May 1998 2 Jun 1998 43 24�1 Glucosinolates, monosaccharides, pectic substances, colour, chlorophyll fluorescence

6 3 Jul 1998 27 Jul 1998 43 24�1 Glucosinolates, monosaccharides, colour, chlorophyll fluorescence

7 3 Aug 1998 27 Aug 1998 43 24�1 Glucosinolates, monosaccharides, pectic substances, colour, chlorophyll fluorescence

8 24 Aug 1998 1 Oct 1998 43 24�1 Glucosinolates, monosaccharides, pectic substances, colour, chlorophyll fluorescence

9 29 Sep 1998 26 Nov 1998 41 22�1 Glucosinolates, monosaccharides, colour, chlorophyll fluorescence

10 4 Nov 1998 21 Jan 1999 43 24�1 Pectic substances, colour, chlorophyll fluorescence

Figure 1. Mean temperature and mean PPFDduring experimental period.

1326 J Sci Food Agric 82:1325–1333 (online: 2002)

M Schreiner et al

composition was accompanied by that of chlorophyll

fluorescence.

For the analysis of internal quality characteristics, a

mixed sample comprising 30 radish roots was pre-

pared. For the determination of glucosinolates and

monosaccharides, whole radish roots (n=30 for each

treatment) were frozen (�28°C), then freeze-dried

and finely ground. Root material for pectin analysis

(n=30 for each treatment) was diced, and 10g of each

sample was frozen with liquid nitrogen and kept at

�28°C until further analysis.

GlucosinolatesA modified HPLC method of Lange et al16 was used

for the determination of glucosinolates. A 0.5g portion

of freeze-dried root tissue was immersed for 1min in a

water bath at 75°C and extracted with 10ml of

methanol/water mixture (7:3 v/v, T =70°C), then

centrifuged with the addition of 2ml of 0.4M barium

acetate. After a second treatment of the residue the

extracts were combined and refilled to 25ml. A 5ml

aliquot of extract was applied to a DEAE-Sephadex A-

25 anion exchanger (Sigma Chemie) and washed with

10ml of doubly distilled water. After application of

250ml of cleaned arylsulphatase solution (Boehringer

Mannheim) and an incubation period of 12h the

desulphonated glucosinolates were eluted with 3ml of

doubly distilled water.

The analysis of the desulphoglucosinolates was

carried out with HPLC equipment from Bischoff

(HPLC compact pump, UV-vis detector LAMBDA

1000, automatic sample generator model, HPCL soft-

ware Starlet) on a Spherisorb ODS2 column (5mm,

250mm�4mm). It was processed with a gradient of

0–20% acetonitrile in water from 2 to 34min, followed

by 20% acetonitrile in water for 6min and then 100%

acetonitrile for 10min. The analysis was carried out

with a flow of 1.3ml min�1 and at a wavelength of

229nm. A sample of 10ml was used for analysis after

clarification with a 0.45mm filter. The glucosinolate

content was calculated using sinigrin as external

standard and the response factor of each compound

relative to sinigrin. Analyses were performed in three

replications per treatment.

MonosaccharidesGlucose and fructose were analysed enzymatically17 in

freeze-dried root tissue. Analyses were performed in

three replications per treatment.

Pectic substancesCell wall extraction of radish roots was conducted as

described by McComb and McCready18 and

Blumenkrantz and Asboe-Hansen19 and modified by

Huyskens.20 The frozen material was blended in an

Ultra-Turrax with 95% acetone and then boiled for

20min. After boiling, the suspension was vacuum

filtered. The residue on the filter paper was resus-

pended subsequently in 95vol% acetone, in 70vol%

ethanol and finally again in acetone (95vol%). The

final white residue on the filter paper was dried

overnight at 70°C. This fraction, the alcohol-insoluble

solids (AIS), was weighed and stored in a vacuum

desiccator over silica gel until further analysis.

The isolated AIS was fractionated into three pectin

fractions, the water-soluble pectin fraction (WSP), the

EDTA-soluble pectin fraction (EDTA-SP) and the

insoluble pectin fraction (ISP), and total pectic

substances (TSP) according to the method described

by Blumenkrantz and Asboe-Hansen.19 The colori-

metric determination of the pectin fractions was

conducted using the carbazole method described by

McComb and McReady.18 The amount of galacturo-

nic acid was measured in each fraction photometrically

at 520nm. Analyses were performed in five replica-

tions for each treatment.

Colour measurementRoot colour was measured with a Minolta LR 321

colorimeter (Minolta Camera Co, Osaka, Japan) using

a white standard and standardised light type D65.

Colour measurements were expressed in the L*a*b*scale, where L* indicates the luminescence, a* repre-

sents the green–red colour axis and b* the blue–yellow

axis. The average of 10 equatorial measurements on

40 roots was recorded for each sample. Two derived

functions were computed from the recorded L*, a*and b* values as follows:

. chroma

C ¼ ½ða*Þ2 þ ðb*Þ2�1=2

. hue angle

H ¼ tan�1ðb*=a*Þ

The chroma characterises the colour saturation; the

hue angle marks the colouration.

Chlorophyll fluorescence measurementMeasurement of the chlorophyll fluorescence was

conducted with a Mini-Pam (Walz, Effeltrich, Ger-

many) on the first pair of leaves after a 20min

adaptation to darkness under standardised conditions

(20°C air temperature, 60–65% relative air humidity).

Four measurements in the middle part of the leaf area

of 40 radishes were taken per sample. A pulse-modu-

lated light source was used. The intensity of the

measuring actinic light was about 0.02mmolm2s�1.

This allowed an accurate assessment of the minimal

fluorescence (Fo).21 Applying a saturating light pulse

(duration 30s, intensity 3000mmolm2s�1), the maxi-

mal fluorescence (Fm) was measured. This procedure

was repeated after light adaptation, and the current

fluorescence (F) and maximal fluorescence (Fm’) weredetected. The following derived functions were calcu-

lated from these chlorophyll fluorescence values as

follows:22

. quantum yield

yield ¼ ðFm � FoÞ=Fm

J Sci Food Agric 82:1325–1333 (online: 2002) 1327

Seasonal effects on root colour and compounds of red radish

. photochemical quenching coefficient

qP ¼ ðFm0 � FÞ=ðFm0 � FoÞ

Statistical AnalysesThe results were analysed by analysis of variance

and calculation of correlations and regression with

STATISTICA23 and TableCurve24 respectively. Sig-

nificant differences are marked by different letters.

The number of samples necessary for the colour

measurement was determined with CADEMO25

(p=0.05; coefficient of variation 20%).

RESULTS AND DISCUSSIONSeasonal climate effects on radish root colourThe variations in hue angle and chroma of the radish

roots at harvest were affected by seasonal climate

parameters. The red colouration (Fig 2), characterised

by hue angle, and the chroma (Fig 3) were most

intense at a high mean PPFD of 450mmolm2s�1. This

effect is presumably due to the PPFD dependence of

the biosynthesis of colour-giving anthocyanins in the

radish periderm,26,27 so that with increasing mean

PPFD the red colouration and chroma of the radish

roots were assumedly intensified via the amplified

synthesis of anthocyanins during cultivation. Simulta-

neously, lower mean temperatures around 11°Ccaused a more distinctive red shade than higher mean

temperatures in the range of 17°C. In several other

crops, anthocyanins are reported to be temperature-

sensitive; for example, in strawberries and other berry

fruits.28,29 This led to the assumption that the

synthesis of anthocyanins is not only PPFD- but also

temperature-dependent, although the PPFD and

temperature dependence was relatively moderate,

marked by regression coefficients of 0.39 for chroma

and 0.45 for hue angle.

In addition, the seasonal variations in hue angle and

chroma correlated with the glucose content of the

roots (Table 2), which is also affected by temperature

and irradiation (Table 3). The red colour of the radish

root periderm is due to the anthocyanin pelargonidin

3-sophoroside-5-glucoside.26,27 During anthocyanin

biosynthesis for glycosylation of anthocyanidins the

monosaccharide glucose is required, because pelargo-

nidin 3-sophoroside-5-glucoside is a glycosylated

compound.27,29 Owing to this biosynthetic require-

ment, the hue angle and hence the red shade were

presumably intensified with increasing glucose content

via amplified anthocyanin biosynthesis.

The photochemical quantum yield of photosystem

II (yield) and the photochemical quenching coefficient

(qP) also influenced the seasonal colour shade and

chroma (Table 2), probably by the provision of photo-

chemical energy for the synthesis of glucose, which is

essential for the synthesis of anthocyanins. Also,

temperature and PPFD effects on these chlorophyll

fluorescence values were significant (yield) or tenden-

tious (qP) (Table 3). It might be assumed that by the

climate-affected primary process of photosynthesis the

biosynthesis of glucose also influenced the seasonally

differentiated hue angle and chroma of radish roots.

The temperature and PPFD influences as well as the

climate-affected glucose content and chlorophyll

fluorescence values explain the variability in the

Figure 2. Hue angle of ‘Nevadar’ radish roots as a function of mean PPFDand mean temperature (p=0.01).

Figure 3. Chroma of ‘Nevadar’ radish roots as a function of mean PPFDand mean temperature (p=0.01).

Table 2. Correlation coefficients between colour valuesand glucose and chlorophyll fluorescence values of‘Nevadar’ radish (n=27, p=0.05)

Variable Hue angle Chroma

Glucose (mg kg�1 FW) 0.46 0.67

Yield (mV) 0.58 0.39

qP (mV) 0.58 0.45


M Schreiner et al

annual course of hue angle and chroma to the extent of

77 and 72% respectively (Table 4), demonstrating a

relatively large seasonal preharvest influence on the

colour expression of radish roots.

Seasonal climate effects on glucosinolatesIn ‘Nevadar’ radish roots the indolyl glucosinolates

glucobrassicin and 4-methoxy-glucobrassicin have

been identified.7 They showed a relatively moderate

temperature and PPFD dependence (r2=0.40) (Fig

4), whereas the alkenyl glucosinolates progoitrin,

glucoraphenin and glucoraphasatin were nearly un-

affected by irradiation and slightly influenced by air

temperature (r2=0.23) (Fig 5). This restricted effect

of climate factors on the indolyl and alkenyl glucosi-

nolates is presumably due the fact that the radish root

is only partly exposed to direct irradiation and hence

the irradiation influence was not sufficient to enhance

the glucosinolate synthesis as found in broccoli. In

contrast to the glucosinolates of radish, glucoraphanin,

the main glucosinolate of broccoli, showed a strong

irradiation and temperature dependence during the

growth of broccoli heads.30

Flavin monooxygenases are involved in the bio-

synthesis of glucosinolates. Their activities are light-

dependent.10 However, the enzyme activity is also

substantially affected by the temperature.31 Owing to

the partly limited light expansion of the radish root, the

temperature effect may be primarily influencing the

glucosinolate biosynthesis in radish, while the PPFD

influence showed only a secondary, slight effect or was

not effective at all (Figs 4 and 5). Thus the content of

Table 3. Glucose and chlorophyll fluorescence values of ‘Nevadar’ radish as a function of climate parameters (n=27)

Dependent variable Regression equation a

Multiple coefficient

of determination

Glucose (mg kg�1 FW) y ¼ 13:54� 353=x1 þ 2477=x21 � 5:86=x2 0.52**

Yield (mV) y ¼ 2:0� 0:20x1 þ 0:008x21 þ 2:42=x2 0.38*

qP (mV) y ¼ �12770� 2297x1 þ 92:36x1:51 þ 7557x1= ln x1 þ 9:42x2:5

2 0.31

a x1=mean temperature; x2=mean PPFD.

* Significant at p=0.05.

** Significant at p=0.01.

Table 4. Hue angle and chroma of ‘Nevadar’ radish as a function of direct and indirect seasonal effects (n=27)

Hue angle Chroma

Regression equationa y=14.70þ0.18x1�0.005x2þ2.61x3�0.23x4�2.77x5 y=�27.43�0.12x1þ0.013x2þ14.37x3�8.45x4�1.70x5Multiple coefficient of

determination

0.77** 0.72**

a x1=mean temperature; x2=mean PPFD; x3=glucose content; x4=yield; x5=qP.


Figure 4. Indolyl glucosinolates in ‘Nevadar’ radish roots as a function ofmean PPFD and mean temperature (p=0.05).

Figure 5. Alkenyl glucosinolates in ‘Nevadar’ radish roots as a function ofmean PPFD and mean temperature (p=0.05).



alkenyl glucosinolates was enhanced with increasing

mean temperature (Fig 4). In contrast, the indolyl

glucosinolate content showed an optimal curve with

respect to the mean temperature (Fig 5). Hence the

synthesis of indolyl glucosinolates in ‘Nevadar’ radish

was amplified at lower mean temperatures (13–15°C)

and moderate mean PPFDs (200–300mmolm2s�1).

Increased contents of indolyl glucosinolates were also

found in field-grown broccoli with higher global

irradiation.30,32

Unlike the colour expression of the radish root, the

glucosinolate metabolism was not influenced by the

glucose synthesis or by the photochemical energy

delivery. This definitely would be conceivable, since

the synthesis of glucosinolates requires, besides the

metabolic energy requirement, a glucose unit which is

attached via a thioester link to the R—C—N struc-

ture.33 This led to the assumption that, with a view to

the glucosinolate biosynthesis, glucose was never at a

minimum during the overall annual course.

Seasonal climate effects on pectic substancesIn January at a mean temperature of 11°C and a low

mean PPFD of 45mmolm2s�1 the radishes revealed a

high total pectin content, while in April at 12°C and an

increased mean PPFD a low content of total pectin

was detected in radish roots (Fig 6). The latter results

are consistent with experiments on radish by Hong

and Lee.34 Huyskens-Keil et al35 also reported that

annual accumulation and degradation processes of

pectic substances in carrot and radish were strongly

dependent on preharvest climate regimes. Sams11

described a negative correlation between high light

exposure, ie irradiation above photosynthetic satura-

tion levels, and fruit texture, which is strongly asso-

ciated with changes in the pectic cell wall compounds.

This effect might also have occurred in early-grown

radishes. Moreover, it is assumed that in spring-grown

radishes the cell wall synthesis or solubilisation of the

cell wall polymers was inhibited. Low-temperature

stress might have caused an inhibition of gibberelic

acid (GA3) activity,36 leading to an alteration in the

pectin pattern, by reducing the polygalacturonase

(PG) synthesis, as was found in tomato.37 PG is one

of the enzymes known to be responsible for pectin

hydrolysis in radishes and thus for accelerating or

retarding physiological processes.34

However, during the annual course, increasing

annual mean temperatures led to an accumulation of

pectic substances (Fig 6). For carrots and several fruit

products it is reported that firmness is promoted by

low temperatures,11,38 whereas in tomatoes high

temperatures enhanced GA3 activity and thus im-

proved fruit texture.37

In order to evaluate the present results with respect

to tissue firmness, further studies on pectolytic enzyme

activity as well as on polyuronide and neutral sugar

patterns, being closely related to quality-determining

textural properties,39,40 have to be conducted in

radishes.

Changes in the chlorophyll fluorescence parameter

‘yield’ (Fig 7) also corresponded analogously with

changes in total pectin of the radish root. It is assumed

that during the summer period an increased produc-

tion of triosephosphates and other carbohydrates—

due to an increased availability of photochemical

energy—occurred, leading to an enhanced accumula-

tion of pectic substances in summer.

The effects of temperature and PPFD as well as the

climate-affected photochemical quantum yield of

photosystem II explained the variability in total pectic

substances during the annual course to the extent of

99% (Table 5).

From the present results it is concluded that

Figure 6. Pectic substances in ‘Nevadar’ radish roots during annualcourse.

Figure 7. Annual course of chlorophyll fluorescence value yield of‘Nevadar’ radish leaves.

Table 5. Total content of pectic substances of‘Nevadar’ radish roots as a function of meantemperature, mean PPFD and climate-affectedchlorophyll fluorescence values (n=12)

Regression equationa y=�2.007�1.63x1�0.073x2þ89.69x3Multiple coefficient of determination 0.99**

a y=total content of pectic substances in roots; x1=mean temperature; x2=mean PPFD; x3=yield.



M Schreiner et al

preharvest climate parameters, specifically the combi-

nation of temperature and PPFD, may evoke different

physiological responses in radish via hormonal and/or

enzymatic actions, leading to an alteration in pectin

metabolism.

Seasonal climate effects on monosaccharidesOwing to the temperature and irradiation dependence

of photosynthesis,12 higher mean PPFDs of 300–

430mmol m2 s�1 in combination with mean tem-

peratures of 16–17°C promoted the photosynthetic

performance in preharvest, as characterised by the

quantum yield of photosystem II (Fig 7), which was

highest in the annual course under these climate

conditions. Thus the contents of glucose and fructose

in the radish roots also have to be explained. As

metabolites of photosynthesis, they were also highest

at the highest mean PPFD and mean temperature.

This effect is particularly distinctive for fructose, as

confirmed by the regression coefficient of 0.81 (Fig 8),

while the seasonal influence was not so strong for

glucose (r2=0.52; Table 3). This could be explained

by the fact that, in the Calvin cycle, fructose

1,6-phosphate, as a primary product, is formed by

triose phosphates, which will be converted then in

further steps to different monosaccharides or poly-

meric carbohydrates.41 Furthermore, high irradiation

combined with high temperature led to a strong degra-

dation of sucrose into glucose and fructose in radish

(Huyskens-Keil S, unpublished). This degradation of

sucrose could be caused by an amplified photorespira-

tion, since photorespiration is distinctively tempera-

ture- and light-dependent.12

CONCLUSIONS AND RECOMMENDATIONS FORRADISH PRODUCTIONThis investigation revealed that the formation of

quality characteristics relevant to consumers, such as

radish root colour and essential taste- and texture-

determining quality characteristics, strongly differed

depending on the seasonal climate conditions. The

seasonal dependence ranged from a slight climate

influence (alkenyl glucosinolates r2=0.23), over a

moderate climate effect (indolyl glucosinolates

r2=0.40, glucose r2=0.50) up to a strongly distinctive

climate influence (hue angle r2=0.77, chroma r2=0.72, fructose r2=0.81, pectic substances r2=0.99).

Therefore, according to consumer-oriented quality

production of radish, the temperature and PPFD

influence should be taken into account in the pro-

duction process and integrated in a corresponding

production management. Moreover, consumer prefer-

ences as well have to be taken into account.

A consumer acceptance test in Germany (Berlin and

Brandenburg) demonstrated that consumers preferred

bright-reddish radishes with hue angle values above

23° and chroma values above 35° to assure high

consumer acceptance.6 The ‘Nevadar’ radish fulfilled

these customer requirements during the entire year.

However, the combination of chroma values of 43–49

with a bright red colour tone (hue angle 21.4–22.5°)led to the most intense and bright-reddish coloured

radish. This combination of chroma and hue angle

values was found at higher mean PPFDs (300–

400mmol m2 s�1) and mean temperatures of 16–17°Cin May, July and August (Table 6).

In ‘Nevadar’ radish the predominantly taste-deter-

Figure 8. Fructose content of ‘Nevadar’ radish roots as a function of meanPPFD and mean temperature (p=0.05).

Table 6. Annual course of climate parameters and compounds of ‘Nevadar’ radish

Month

MT

(°C)PPFD

(mmol m2s�1)

Hue angle

(deg) Chroma

Alkenyl

glucosinolates

(mg kg�1 FW)

Indolyl

glucosinolates

(mg kg�1 FW)

Glucose

(mg kg�1 FW)

Fructose

(mg kg�1 FW)

Pectic

substances

(g kg�1 FW)

Yield

(mV)

qP

(mV)

Jan 11.1 45 18.44b 34.28c — — — — 4.12a 0.77b 0.50bc

Feb 12.1 67 18.16b 37.11bc 140.0b 10.3b 10.6b 6.9c — 0.78b 0.68ab

Mar 12.2 117 18.26b 41.04b 106.5bc 13.5a 13.6a 7.9bc — 0.79b 0.80ab

Apr 12.4 225 22.36a 43.68b 59.3d 8.2bc 10.5b 8.6a 2.48c — —

May 15.2 295 19.21b 37.21bc 117.0b 20.4a 10.0b 8.6ab — 0.79b 0.89a

Jun 16.5 432 20.69a 40.22b 116.1b 15.0a 10.9b 9.6a 3.06bc 0.82a 0.52b

Jul 17.0 406 22.47a 48.81a 72.8c 3.1c 13.0a 10.0a — 0.82a 0.52b

Aug 16.1 318 21.35a 43.22b 182.1a 7.4bc 12.0ab 8.0bc 3.28ab 0.82a 0.30c

Oct 13.4 199 17.51b 37.30bc 153.1ab 21.7a 8.9c 6.3c 2.486c 0.62c 0.95a

Nov 15.0 82 18.46b 35.53bc 101.8c 10.8b 9.2c 5.6c — 0.79b 0.58bc



mining alkenyl glucosinolate is glucoraphasatin. The

majority of German consumers in Berlin and

Brandenburg preferred a glucoraphasatin content of

90–130mg kg�1 fresh weight, since this glucoraphasa-

tin concentration has the desired expression of the

taste attribute ‘pungent’.7 ‘Nevadar’ radishes pro-

duced in March, May, June and November fulfilled

these consumer requirements (Table 6). The different

climate conditions in these months also demonstrated

the slight climate dependence of the alkenyl gluco-

sinolates.

Consumer preferences for ‘Nevadar’ radish with

regard to colour expression and taste can be satisfied

best within the early summer months. However, to

produce radishes not only under summer climate

conditions, those bright red cultivars should be

preferred which are marked by a high photosynthetic

capacity (yield >0.80mV) at relatively low irradiation

intensities (50–100mmol m2 s�1) and lower mean

temperatures (11–13°C). Thus photochemical energy

can be delivered sufficiently for the synthesis of colour-

determining compounds. This potential would be

indicated by cultivars with distinctive formation of

chlorophyllrich leaves. This has particularly to be

taken into account for greenhouse cultivation in winter

or for cultivation with fleece or films.

These recommendations are valid not only for the

desired colour expression but also for the monosac-

charides, because the monosacharide content was also

highest under climate conditions in summer (mean

PPFD 300–400mmolm2s�1, mean temperature

16–17°C) (Table 6). Monosaccharides are not only

essential metabolites for the synthesis of anthocyanins

and glucosinolates, they also determine the taste of

radish. Increased monosaccharide contents led to a

more intense taste expression in radish.6

To satisfy the increasing health consciousness of

consumers and thus the demand for functional foods,

the content of bioactive indolyl glucosinolates should

be increased by creating lower mean temperatures

(13–15°C) with moderate mean PPFDs (200–

300mmolm2s�1) in the production process. Increased

contents of indolyl glucosinolates were also found in

broccoli with higher global irradiation.30,32

The relatively low contents of total pectin during the

entire year were associated with a weak cell wall

integrity of the radish root. Studies have demonstrated

that the sensory texture impression ‘firm’ is also

determined by the pectin content of the radish root.8

However, further investigations have to be conducted

in order to confirm quantitative relations between

pectic substances and consumer preferences.

With respect to the climate effects on quality

characteristics, various consumer preferences can be

satisfied. For the production of bioactive radishes

showing particularly relatively high contents of indolyl

glucosinolates, cultivation should be carried out in

spring and autumn. In summer cultivation, consumer

preferences in colour and taste can particularly be

satisfied with the desired contents of alkenyl glucosi-

nolates and monosaccharides as well as by the desired

colour expression.

Additionally, the type of soil should be taken into

account for consumer-oriented radish production. To

enhance the content of monosaccharides and alkenyl

glucosinolates in early summer and autumn, radishes

should be grown in heat-saving soils such as humic

loamy or loess soils comprising only a relatively low

humus content to avoid undesired colour changes. In

summer, sandy soils with a high potential for heat

emission should be selected in order to prevent low

indolyl glucosinolate contents. For early cultivation in

March and April, fleece or films could be used

independently of the soil type for enhancing the

temperature.

REFERENCES1 Geiger W, Qualitatslehre. Friedrich Vieweg, Braunschweig

(1994).

2 Gironi F and Testoni A, The relation between colour and quality

of vegetables. Acta Hort 259:141–167 (1990).

3 Clydesdale FM, Gover R, Philipsen D and Fugardi C, The effect

of color on thirst quenching, sweetness, acceptability and flavor

intensity in fruit punch flavored beverages. J Food Qual 15:19–

38 (1992).

4 Francis FJ, Quality as influenced by color. Food Qual Pref 6:149–

155 (1995).

5 Kays S, Preharvest factors affecting appearance. Postharv Biol

Technol 15:233–247 (1999).

6 Schreiner M, Schonhof I, Widell S, Krumbein A, Peters P,

Auerswald H, Huyskens-Keil S and Linke M, Qualitat von

Radies, in Annual Report 1998 of the Institute of Vegetable and

Ornamental Crops Großbeeren/Erfurt eV. Institute of Vegetable

and Ornamental Crops Großbeeren/Erfurt eV, Großbeeren,

pp 39–46 (1999).

7 Widell S, Krumbein A and AuerswaldH, Glucosinolate in Radies

und sensorische Bewertung. Wissenschaftlichen Arbeitstagung

der Deutschen Gartenbauwissenschaftlichen Gesellschaft und des

BDGL 35:151 (1998).

8 Huyskens-Keil S, Schreiner M, Widell S and Peters P, Zer-

storungsfreie Qualitatsbestimmung bei Radies. Gemuse 7:406–

408 (1998).

9 Vogel G, Handbuch des Speziellen Gemusebaus. Eugen Ulmer,

Stuttgart, pp 406–420 (1996).

10 Wallsgrove RM and Bennett RN, The biosynthesis of gluco-

sinolates in Brassicas, in Amino Acids and Their Derivatives in

Higher Plants. Society for Experimental Biology Seminar 56, Ed by

Wallsgrove RM, Cambridge University Press, Cambridge, pp

243–259 (1995).

11 Sams CE, Preharvest factors affecting postharvest texture.

Postharv Biol Technol 15:249–254 (1999).

12 Larcher W, Okophysiologie der Pflanzen. Ulmer, Stuttgart, pp 71–

112 (1994).

13 Bleiholder H, Buhr L, Feller C, Hack H, HessM, Klose R,Meier

U, Stauss R, van den Boom T and Weber E, Growth Stages of

Mono- and Dicotyledonous Plants. BBCH-Monograph. Black-

well, Berlin, pp 101–104 (1997).

14 Bickelmann U, Leitfaden fur die Anwendung der EG-Qualitatsnor-

men fur Frische Obst, Gemuse und Citrusfruchte. Rheinischer

Landwirtschaftsverlag, Bonn, pp 47–85 (1996).

15 Schouten RE, Otma EC, van Kooten O and Tijskens LM,

Keeping quality of cucumber fruits predicted by biological age.

Postharv Biol Technol 12:175–181 (1997).

16 Lange R, Petrzika M, Raab B and Linow F, Zur Kenntnis der

Schwefelverbindungen in Raps – (Brassica napus) Varietaten

und Verarbeitungsprodukten. Nahrung 35:385–389 (1991).


M Schreiner et al

17 Boehringer Mannheim, Methoden der Enzymatischen Lebensmittel-

analytik. Boehringer Mannheim Gmb H, Mannheim (1986).

18 McComb E and McCready R, Colorimetric determination of

pectic substances. Anal Biochem 24:1630–1632 (1952).

19 Blumenkrantz N and Asboe-Hansen G, New method for quan-

titative determination of uronic acids. Anal Biochem 54:484–

489 (1973).

20 Huyskens S, Morphological, physiological and biochemical

aspects in the cultivation of two pantropical cucurbits: Luffa

acutangula L, Roxb and Momordica charantia L. Dissertation,

Rheinische Friedrich-Wilhelms-Universitat, Bonn (1991).

21 Van Kooten O and Snel J, The use of chlorophyll fluorescence

nomenclature in plant stress physiology. Photosynth Res

25:147–150 (1990).

22 Genty B, Briantais JM and Baker NR, The relationship between

the quantum yield of photosynthetic electron transport and

quenching of chlorophyll fluorescence. Biochim Biophys Acta

990:87–92 (1989).

23 StatSoft, Electronic Textbook StatSoft. StatSoft Inc, Tulsa, OK

(2001).

24 AISN Software, TableCurve 3D. Version 3.0. User’s Manual.

AISN Software Inc, Chicago, IL (1997).

25 Rasch R, Guiard V and Nurnberg G, Statistische Versuchsplanung:

Einfuhrung in die Methoden und Anwendungen des Dialogsystems

CADEMO. Gustav Fischer, Stuttgart (1992).

26 Mazza G and Miniati E, Radish, in Anthocyanins in Fruits,

Vegetables, and Grains, Ed by Mazza G and Miniati E, CRC

Press, Boca Raton, FL, pp 288–290 (1993).

27 Herrmann K, Inhaltsstoffe der Radieschen und Rettiche. Die

Industrielle Obst- und Gemuseverwertung 8:240–246 (1997).

28 Herrmann K, Vorkommen, Gehalte und Bedeutung von Inhalts-

stoffen des Obstes und Gemuses. II. Flavonoide: Catechine,

Proanthocyanide, Anthocyanide. Die Industrielle Obst- und

Gemuseverwertung 5/6:170–175 (1991).

29 Bohm H, Boeing H, Hempel J, Raab B and Kroke A, Flavonole,

Flavone und Anthocyane als naturliche Antioxidantien der

Nahrung und ihre mogliche Rolle bei der Pravention chron-

ischer Erkrankung. Z Emahrungswiss 37:147–163 (1998).

30 Schonhof I, Krumbein A and Gutezeit B, Vorerntemaßnahmen

zur Beeinflussung des Glucosinolatgehaltes in Brokkoli.

Wissenschaftlichen Arbeitstagung der Deutschen Gartenbauwissen-

schaftlichen Gesellschaft und des BDGL 36:56 (1999).

31 Ziegler H, Physiologie, in Lehrbuch der Botanik, Ed by Sitte P,

Noll F, Schenck H and Schimper AF, Gustav Fischer,

Stuttgart, pp 242–472 (1993).

32 Schonhof I, Krumbein A and Widell S, Glucosinolate in

Brassicaceae und Moglichkeiten ihrer Beeinflussung. Tagung

der Deutschen Gesellschaft fur Qualitatsforschung 35:47–56

(2000).

33 Fenwick GR and Heany RK, Glucosinolates and their break-

down products in cruciferous crops, foods and feedingstuffs.

Food Chem 11:249–271 (1983).

34 Hong SJ and Lee SK, Comparison of physiological characteris-

tics among radish cultivars after storage. J Korean Soc Hort Sci

36:812–817 (1995).

35 Huyskens-Keil S, Ulrichs C and Schreiner M, Cell wall carbo-

hydrate metabolism of perishable vegetables in pre- and post-

harvest. Acta Hort in preparation.

36 Libbert E, Lehrbuch der Pflanzenphysiologie. Gustav Fischer,

Stuttgart (1993).

37 Mignani I, Greve LC, Ben-Arie R, Stotz HU, Li C, Shackel KA

and Labavitch JM, The effect of GA3 and divalent cations on

aspects of pectin metabolism and tissue softening in ripening

tomato pericarp. Physiol Plant 93:108–115 (1995).

38 Ulrichs C and Huyskens-Keil S, Kohlenhydratmetabolismus von

Mohren mit Laub wahrend der Nachernte. Tagungsband der

Deutschen Gesellschaft fur Qualitatsforschung 33:22–26 (1997).

39 Tong C, Krueger D, Vickers Z and El-Shiekh A, Comparison of

softening-related changes during storage of ‘Honeycrisp’

apple, its parents, and ‘Delicious’. J Am Soc Hort Sci

124:407–415 (1999).

40 Sakurai N and Nevins DJ, Relationship between softening and

wall polysaccharides in avocado (Persea americana Mill) meso-

carp tissues. Plant Cell Physiol 38(5):43–49 (1998).

41 Heß D, Pflanzenphysiologie. Eugen Ulmer, Stuttgart (1999).



seasonal climate effects on root colour and compounds of red radish

Documents