Volatiles in distillates of fresh, dehydrated and freeze dried horseradish

Insl. Food Sci. Technol. J. Vol. Can. Inst. Vo/. 17. No. I. pp. 018-023. 1984

Volatiles in Distillates of Fresh, Dehydrated and Freeze Dried Horseradish G. Mazza Agriculture Canada, Research Station, Morden, Manitoba, ROG IJO

dens, and to date no major effort has been made to commercialize this potentially valuable crop. Consequently, we are studying production and utilization methods of Canadian grown horseradish for domestic and export markets. The main function of horseradish as a dietary component depends upon its characteristic flavour whose principal components have been shown to be allyl and 2-phenethyl isothiocyanate (Isaac and Kohlstaedt, 1962; Stoll and Seebeck, 1948). Stahmann et al. 1943. More recently, Gilbert and Nursten (1972) used gas chromatography-mass spectrometry (GC-MS), to study the essence of the volatile components of five samples of horseradish roots and reported the presence of 17 compounds. Five of these, allyl thiocyanate, allyl-2-butyl-, 4-pentenyl-, and 2-phenethyl isothiocyanates, were identified. Using paper, GC and UV spectroscopy, 2-butyl isothiocyanate was also previously identified in Japanese horseradish (Kojima et af. 1969). The list of known volatile constituents of horseradish was further expanded when Grob and Matile (1980), using capillary GC-MS analysis, identified a total of 30 glucosinolate-derived horseradish constituents. Traditionally horseradish has been consumed as a sauce containing comminuted root, acetic acid from vinegar and salt. More recent and increasingly important processed products include dehydrated and freezedried horseradish, used as an ingredient by manufacturers of such products as cocktail and fish sauces, horseradish mustard, or horseradish dressings and horseradish essence. Quantitative and qualitative studies on the effect of these postharvest processes on flavour, together with concentration and distribution of flavour components in the different portions of the plant are of importance but have hitherto received relatively little attention. The objectives of this study were to establish the identity of the flavour components present in locally grown horseradish, to determine the distribution pattern of flavour components in horseradish, and to study the effect of dehydration and freeze-drying on the flavour of the product as compared with that of fresh roots.

Abstract The steam-volatile constituents of locally grown horseradish (Armoracia lapathijolia, Gilib.) have been studied by gas (G.C.) and combined gas chromatography - mass chromatography (G.C-) spectrometry (GC-MS). Of the ten components idendified overall, six were isothiocyanates, two were nitriles, one was allyl thiocyanate and one was carbon disulfide. The distribution and concentration of flavor components in crowns, primary and secondary roots and rootlets differed from those in tops. The primary and secondary roodets roots and crowns accounted for the bulk of the weight of the root fraction as well as its essence content. Based on allyl isothiocyanate content, the quality of horseradish essence deteriorated as the distillation time was extended. Freeze drying and dehydration of sliced roots improved the recovery and quality of the essence. Some aspects of knowledge of the formation and decomposition of selected volatiles have been discussed as the basis of interpretation of the above findings.

Resume Les constituants volatils a la vapeur de raifort (Armonica lapathi/olia, Gelib.) produit localement ont eu: et<: etudies a I'aide de la chromatographie en phase vapeur avec ou sans spectrometrie de masse. Les dix constituants qui furent identifies sont six isothiocyanates, deux nitriles, un thiocyanate allylique et un disulfure de carbone. La distribution et la concentration des constituants aromatiques furent differentes dans les tetes par rapport aux couronnes, aux racines primaires et secondaires et aux radicelles. La majeure partie du poids de la fraction racine et des constituants volatils fut associes I'on se aux racines primaires et secondaires et aux couronnes. Si l'on I'huile base sur la teneur en isothiocyanate allylique, la qualite de l'huile Ie progres de la disaromatique de raifort va en se deteriorant avec le tillation. Il II a ete possible d'ameliorer le Ie rendement et la qualite de I'huile aromatique par lyophilisation et deshydratation des racines l'huile en tranches. Les resultats ci-hauts sont interpretes a la lumiece de certains aspects de la formation et de la decomposition de quelques constituants volatils.

Introduction Horseradish, )Armoracia lapathifoUa, lapathi/olia, Gilib. A. rusticana Gaertn, Mey. and Scherb), a member of the Cruciferae family, is cherished as a condiment in human diets on all the continents. In Japan alone, there are currently twenty nine manufacturers of horseradish products (Hashimoto, 1982), and in the U.S. the annual commercial production is estimated at 6 million kg (Rhodes, 1976). Canadian production of horseradish is, however, confined mainly to home gar-

Copyright" Copyright 10 1984 Canadian Institute of Food Science and Technology

18

Experimental plant materials lapathijo/ia, Gilib.) The horseradish (Armoracia lapathijolia, used for this study was grown on sandy loam soil at Agriculture Canada Research Station, Modern, Manitoba. Broadfen root cuttings (1-2 cm in diameter and 5-15 cm in length) were hand-planted in the spring of 1981 at plant spacing 40 cm and row spacing of 1 m. Weed control was achieved by the use of the postemergence herbicide Linuron Unuron at 2.5 kg/ha. Horseradish was fertilized with 850 kg 23-23-0 and 60 K20/ha. Insects (flea beetle) were controlled by kg KzO/ha. spraying with Belmark as required. Harvesting was done by hand from September 20 to October 14, 1982. The composition of horseradish crowns, primary roots, secondary roots, rootlets and tops or leaves was determined by carefully separating the five tissue fractions of plants at the time of harvest. The fresh weight of :ach fraction was recorded and the corresponding mOIsture contents and essence concentration and composition determined. Following harvest, the roots were stored in a refrigerated storage at 4°C and 90-95070 relativ7humidity. In a series of experiments, sliced (1 relative mm thick) freeze dried and dehydrated roots were used to determine the concentration and composition of the essence. Freeze drying was carried out in a Labdry-5 at a condenser temperature of conco freeze drY-5 - 60°C, a pressure less than 100 J.t and a shelf temperature of 25°C. Dehydration was accomplished in a Lab-Line/PRL hi-speed fluid bed dryer (Lab-Line Instruments, Inc., Melrose Park, Ill.) consisting of a blower connected to a heating unit and a stainless steel v.ertical v:rtical drying chamber with a stainless steel support filter at the bottom and a nylon filter bag at the top. A thermocouple planted after the heating unit and connected to a temperature controller enabled automatic control of the temperature of the drying air. One mm thick slides were dried with air at 50°C and 2.9 m/s air velocity. . Determination of moisture Horseradish moisture content was determined in a vacuum oven at 70°C and 49 mm Hg vacuum for 24 h by passing a slow current of dried air through the oven. Preparation of essence Fresh horseradish slices (500 g) were placed in a 5 L round-bottom double necked distilling flask (connected to a Crank Case distilling receiver, Canlab 1981 Cat. No. D6177, and a water condenser), allowed to stand for 30 min, mixed with 1.5 L distilled water (added through the condenser and distilling receiver) and hydrodistilled for 15-180 min. Freeze dried and dehydrated horseradish were handled similarly but the samples were rehydrated samples. rehydr~t~d for 30 min in the distilling hydrodistillation. Essence samples were pnor to hydrodlstlllation. flask prior collected sequentially after 15, 30, 60 and 120 min of extraction and after 30, 60, 120 and 180 min of continuous extraction.. Each essence sample was weighed

Ins!. Food Sei. Sci. Technol. Teehnol. J. Vol. 17, No. I, 1984 Can. Inst.

~nd analyzed separately. All analyses were done 3-6 times. tImes.

Gas chromatography ~ Varian .Aerograph series 2701 gas chromatograph, eqUIpped With eqUipped with a flame ionization detector, was used. The apparatus was fitted with a stainless column (3 m long, long,S5 mm o.d.) packed with 4% Carbowax and 1% diethylene glycol adipate (DGA) on Chomosorb W (60-80 mesh). Separation of the volatiles was also done on Carbowax 20M, 30 m x 0.25 mm i.d., glass c~pillary column and on 5% SP - 2340 (cyanopropyl c~~illary SIlIcone) sIlIcone) coated on Chromosorb WAW (100-120 mesh) and packed in a glass column (2 m long, 2.0 mm i.d.). The operating conditions for most runs were as follows: injection port 220°C; detector temperature 200°C; column temperature 80°C for 3 min and then programmed at 5°C/min to 200°C and holding at this temperature for 3 min, carrier gas flow 30 mL He min.-I-) (1 mL/min for the capillary column); injection min. volu~es 2 J.tl. The area of the peaks was integrated by CDS-Ill electronic module. a Vanan Aerograph CDS-lll Gas chromatography - mass spectrometry Mass spectra of the peaks were obtained by means of combined gas chromatography - mass spectrometry .(GC-MS) using an AEI MS 50 mass spectrometer In the Centroid mode and a Finnigan 1015 Quadrupole mass spectrometer with a BiemannWatson glass interface coupled with a Varian Aerograph gas chromatograph. Mass spectrometer parameters were as follows: ionization potential 70 eV; ionization current 40 J.tA; resolution, 1000; ~nd scan speed 3 s for a range of 1 to 800 m/e. Pure compounds used in chromatography and mass spectra comparison were obtained from Eastman Kodak Co. (Rochester, N.Y.) and from ICN Pharmaceuticals. Inc.• Inc.. K & K Labs Div. (Plainview, N.Y.).

Results and Discussion The characteristic flavour of horseradish is due to volatiles consisting mostly of sulfur compounds. The volatiles are absent in intact tissues. However, when the tissue is damaged, reaction between the enzyme(s) and flavour precursors (glucosinolates) occurs, resulting in the formation of flavour compounds as follows (VanEtten et al. 1969).

/'

S--C6 HIIOS S--C6HIIOs

R--C

~ N--O--SOzO-

::::.e (S-- ]:::::se

Thiog I:::. ida.: [R__ [R__( ThiOgl:::Sid8S:

N--O--S020-

S-- ]

:

N--

Glucosinolate

R--N

/

= =C =S

rsothiocyanate

Isothiocyanate

.

1~ !~ = = Nitrile Thiocyanate R--C :: N N

Nitrile

R--S--C :: N N Thiocyanate

+ S

In some instances the isothyocyanates initially formed undergo further transformations. For example, the

Mazza / 19

2

10

4

41

1000

1000

CH 2 CHCH 2

,/

67 CH CHCH CN ,'.. 2 2

500

~

], 0 20 100.0

500

II 30

40 41

.

,I 50

.I 60

70 99 M'

CH2cHCH2 /

~O

000

40

60

80

100

91

120

140

CH2CHCH2

~ 500

50D 500

9

Fig. 2. Mass spectra of some horseradish volatiles. b

a

o

4

8

12

Fig.l.

20

16

Retention time

24

28

(min.)

Gas chromatogram of steam distilled essence from fresh horseradish using a Carbowax 20M, 30 m x 0.25 mm i.d. glass capillary column. Peak numbers refer to components listed in Table I.

presence of carbon disufide may be accounted for by hydrolysis of the isothiocyanates (Bailey et al. 1961). A typical chromatogram of distilled horseradish essence separated on a 30 m x 0.25 mm Carbowax 20M narrow bore glass capillary column is shown in Figure 1. There were over 10 resolved constituents, 4 of which were major, with the rest being intermediate and minor constituents. The identified compounds, listed according to their order of elution on Carbowax, are presented in Table 1. In Figure 2 MS - fragmentation patterns for vinyl acetonitrile, allyl isothiocyanate, 3-phenyl 3-phenyI propionitrile

and 2-phenethyl isothiocyanate are presented. The mass spectra of unsaturated isothiocyanates were dominated by peaks corresponding to the allyl fragment at mle 41 and CH CHzNCS 2 NCS of mle 72. The aromatic isothiocyanate, 2-phenethyl isothiocyanate, displayed a very intense mle 91 peak as did the corresponding nitrile. Mass spectra of isothiocyanates and their mechanism of fragmentation were described by Kjaer et al. (1963). Figure 3 shows typical chromatograms from two essence fractions separated on a 3 m x 5 mm o.d. 4010 Carbowax and 1010 DGA on Chromosorb W. The volatiles present in the essence fraction collected after 30 min of distillation [curve (a)] were the same as those present in the fraction collected in the 60-120 min distillation period [curve (b)], and the same as those detected with the capillary column. However, the concentration of vinyl acetonitrile (peak no. 2), phenyl propionitrile (peak no. 9) and phenethyl isothiocyanate (peak no. 10) was higher in the essence fraction col-

Table I. Compounds identified in horseradish distillates. Component Formula I Carbon disulfide Vinyl acetonitrile 2 (3-Butenenitrile) 3 2-Buthyl isothiocyanate 4 Allyl isothiocyanate S 5 Allyl thiocyanate 6 3-Butenyl isothiocyanate 7 4-Pentenyl isothiocyanate 8 3-Methylthiopropyl isothiocyanate 9 3-Phenyl propionilrile propionitrile (hydrocinnamonitrile) 10 2-Phenethyl isothiocyanate __ _ . 1 Refers .to to peak number for curves in Figures I and 2. ~~efer.s 2 Id tT . ~ ~callon based on retention times, co-chromatography and MS data. 3 en ent~f~cauon dentlflcation based on MS data only. Identification

Molecular Weight 76

Identification b 2Z

67

b

liS 115

b

99

b

99

b

113

c3

127

c

147

c

131

b

163

b

3,

Mazza 20 II Mazza

J. InSf. lnst. Can. Sei. Sci. Teehnal. Technol. Alimenf. Aliment. Vol. 17, I, 1984 17. No. I.

leo 180

75

IJ i!

10

~ 50

"

50

25

10

12

Retention time (min.)

I' 10

I' 10

20

Fig. 3. Gas chromatogram of steam distilled essence from fresh horseradish using a stainless steel column (3 m x 5 mm o.d.) packed with 4070 Carbowax and 1070 DGA on Chromosorb I. W. Peak numbers refer to compounds listed in Table 1. Curve (a) is from essence fraction collected after 30 min of distillation. Curve (b) is from the 60-120 min essence fraction.

lected in the 60-120 min distillation period than in that collected in the 0-30 min period. Allyl isothiocyanate, on the other hand, was more abundant in the fraction collected in the 0-30 min 4070 Cardistillation period. Using the 3 m x 5 mm o.d. 4% bowax and 1% 1070 DGA on Chromosorb W column, the effect of distillation time on the composition of fresh horseradish essence was studied. With sequential collection of the essence, the concentration of allyl isothiocyanate decreased from over 90% of the fraction taken after 15 min of distillation to approximately 20% of the fraction obtained in the 60-120 min distillation period (Table 2). The 2-phenethyl isothiocyanate increased in concentration and approached 40% in the later fractions. The two nitriles also increased. Vinyl acetonitrile, for instance, increased 10 fold. This suggests that although allyl isothiocyanate has a higher boiling point (159°C) than vinyl acetonitriles (119°C) and phenethyl isothiocyanate (144°C) its relative volatility is higher than the nitriles and phenethyl isothiocyanate and thus left the water-solids-volatiles mixture before the other compounds. However, it is also possible that by the action of heat allyl isothiocyanate, and allyl thiocyanate, are converted into vinyl acetonitrile and sulfur or carbon disulfide, and phenyl

propionitrile is formed from the corresponding isothiocyanate. The composition of essences collected after 30, 60 and 180 min of continuous extraction (Table 2), as well as literature reports (VanEtten et al. 1969; Gilbert and Nursten 1972), support this supposition. As can be noted, 81.14 ± 2.02% of essence collected after 30 min of extraction was allyl isothiocyanate, 14.40 ± 2.50% was 2-phenethyl isothiocyanate, 4.50 ± 1.60% was vinyl acetonitrile, 1.90 ± 1.78% was allyl thiocyanate and less than 0.5% was 3-phenyl propionitrile. However, after 180 min of extraction the composition of the essence was 12.03 ± 1.10% allyl isothiocyanate, 62.70 ± 0.89% vinyl acetonitrile, 15.10 ± 3.37% 3-phenyl propionitrile, 7.58 ± 0.94% 2-phenethyl isothiocyanate and 0.94 ± 0.57% allyl thiocyanate. Thus the extent of distillation of horseradish tissue determines which volatiles predominate but a mixture of these appears to be always formed. In Table 3 are presented results of a dissection experiment of Broadfen horseradish plants whose tissue fractions were subjected to continuous distillation for 30 min. On a fresh weight basis, the essence content was very low in the tops and 1.32 - 1.85 g/kg in the roots. The volatile aroma components of essence extracted from the five plant fractions were similar, although the tops contained significantly less 2-phenethyl isothiocyanate and more allyl thiocyanate. The results presented in Table 3 are of importance in relation to marketing of horseradish roots. For instance, rootlets which constituted only 13.3% of the total root mass, are expensive to harvest, but the fact that there was no significant difference in essence content and composition between the thinner and the thicker roots, implies that their value/unit weight to the consumer should be the same, although the harvesting and cleaning cost to the producer will be higher. As for the observation that the tops or leaves contained less volatiles than the roots, probable explanations could be the location for synthesis of flavour precursors and the translocation of these from the leaves to the roots. Pate (1968) has demonstrated in studies of Pisum arvense L. that the initial biosynthetic step to amino acids and proteins, namely, reduction of nitrate and sulphate, takes place mainly in the leaves. Some reduction of inorganic salts absorbed by the roots take place there, with initial formation of

Table 2. Changes in composition of fresh horseradish essence with distillation time. Compound (area %j

Fraction (min)

o0-15 -I 5 15-30 30-60 60-120 0-30 0-60 0-180

Vinyl acetonitrile

Allyl isothiocyanate

Allyl thiocyanate

3-Phenyl propionitrile

2-Phenethyl isothiocyanate

3.03 ± 1.62 1 10.57 ± 0.06 14.86 } 3.33 35.60 ± 2.42 4.50 ± 1.6 14.85 ± 1.06 62.70 ± 0.89

93.60 I 2.35 67.20 ± 2.06 42.10 ± 4.51 23.62 ± 11.03 81.14 ± 2.02 65.95 ± 2.33 12.03 ± 1.10 LIO

2.33 ± 0.89 3.37 ± 1.09 0.90 ._ 0.49 1.25 ± 0.86 1.90 ± 1.78 2.90 ± 0.14 0.94 ± 0.57

0.50 1.80 2.00 4.36 0.20 0.90 15.10

3.13 15.70 38.58 38.66 14.40 13.30 7.58

± 0.50

© 0.82 ± 0.91

± 2.06 ± 0.14 ± 0.14

\ 3.37

± 1.02 ± 1.48

± 6.34

_. 7.79 ± 2.50 ± 1.84

± 0.94

'Standard deviation. I, 1984 Can. Ins!. Inst. Food Sci. Technol. J. Vol. 17, No. 1.

Mazza I 21

Table Table 3. Essence Essence content and composition of five horseradish tissue fractions distilled for 30 min. Major Components (area %) Tissue Tissue fraction fraction II 22 33 44 55

Description Tops Tops Crowns Primary roots Secondary roots Rootlets

Weight of tissue (kg)1

Proportion Mositure of total fresh content weight (%) (%) 2 2.980 ± 0.118 59.9 ± 4.5 77.4 ± 0.5 0.408 ± 0.044 8.2 ± 0.1 67.8 ± 0.4

-

Essence (g/kg FWB) 0.37 ± 0.01 1.54 ± 0.63

2·Phenethyl Vinyl Allyl Allyl 3-Phenyl 2-Phenethyl isothiocyanate acetonitrile isothiocyanate thiocyanate propionitrile isothiocyanate 0.09 1.30 ±± 0.09 4.85 ± 0.40 82.90 ± 6.79 4.80 ± 1.70 0.45 ± 0.09 ±3.36 6.90 ±3.36 9.40 ± 3.11 81.55 ± 0.92 4.00 ± 1.00 0.55 ± 0.10

0.762 ± 0.028

15.0 ± .6

63.7 ± 0.2 1.85 ± 0.27

4.50 ± 1.6

8'1.14 ± 2.02

1.90 ± 1.78 0.20 ± 0.10

2.50 14.40 ± 2.50

0.577 ± 0.239 0.273 ± 0.143

J11.3 1.3 ± 3.5 5.3 ± 2.2

61.2 ± 1.1 1.32 ± 0.23 62.2 ± 0.2 1.37 ± 0.65

3.45 ± 0.44 3.55 ± 0.64

0,83 80.58 ± 0.83 83.00 ± 5.66

0.13 ± 0.05 1.55 ± 0.57 0.13±0.05 2.10 ± 1.00 0.15±0.09

1.58 13.15 ± 1.58 8.35 ± 3.71

II weight weight of tissue/plant 22standard deviation standard deviation

amino acids. These reductive processes depend for their energy and carbon source on simple photosynthates, translocated from chlorophyll-containing leaves. A probable location for synthesis of flavour precursors in horseradish is the junction of the pathways of inorganic ion and of photosynthate, i.e. the crown, especially as relatively high flavour component concentrations were observed there. The role of the transport system is clearly important in relation to movement of these reactants and distribution of the flavour precursors throughout the plant. The flavour strength of fresh primary and secondary horseradish roots was also compared to that of dehydrated and freeze dried samples. The data, summarized in Table 4, show that the quantity of essence extracted from fresh material was lower than that extracted from dehydrated and freeze dried samples. Also, a comparison of the peak area percent revealed that the essence from freeze dried and dehydrated horseradish contained more allyl isothiocyanate, less 2-phenethyl isothiocyanate and practically the same content of the other volatiles. Fresh horseradish samples were kept in the distillation flask, at room temperature, for 30 min between the slicing and the distillation steps. The freeze dried and the dehydrated samples, on the other hand, were sliced, processed, placed in the distillation flask, rehydrated for 30 min and then distilled. Thus in the rehydrated dry samples, the enzymes and glucosinolates, released during cutting of the roots into 1 mm slices, were in contact with each other for a longer period of time and the temperature, pH and conditions of hydrolysis were different from those of the fresh samples. Thus, it is not surprising that the quantity and quality of the

essence from the two types of sample are different. However, the essence content of freeze dried and dehydrated samples was higher than that of the fresh samples. In the case of dehydrated onions, loss of 98070 have been reported volatiles in the order of 90 to 98010 (Friedman and Whenham, 1974; Mazza and LeMaguer, 1980). The difference in behaviour between horseradish and onion may be due to differences in properties of the volatile precursors and 'enzyme systems present in the two plants. In this regard, there is clear evidence that glucosinolases exist in most Cruciferae as isoenzymes. The evidence for lyase isoenzymes in Liliaeceae is not so clear, and some published results do show differences in properties (Schwimmer and Freedman, 1972). Therefore, despite the loss of some volatiles which undoubtedly takes place during dehydration and freeze drying of horseradish, the synthesis of volatiles which takes place during processing appears to be higher than the loss. Thus, in view of the fact that horseradish is consumed mainly for its flavour, the present observations suggest that the quality of processed products may be superior to that of fresh material. This may serve as a base for further investigations of the proprocessing effect as a practical and useful means of improving the quality and value of horseradish. Acknowledgements The author wishes to thank M. Hodgins and L.C. Kyle for technical assistance, Wayne Buchanan of the Chemistry Department, University of Manitoba and Walter Miles of the Mass Spectrometry Methodology WaIter Laboratory Services Division, Food Protection and Inspection Branch, Agriculture Canada, for assisting with the measurement of mass spectra and B.B.

Table 4. Comparison of of selected volatile concentration in fresh, freeze dried and dehydrated primary and secondary horseradish roots distilled Table distilled for 30 min. Essence OM g/kg DM Compound (area %)

Sample Sample Freeze Freeze dried dried Dehydrated Dehydrated

After 120 min of distillation

8.06 ± 0.71'1 8.06±0.71 7.07 ±± 0.56 ~~ 5.20 ± 0.37 Standard deviation. II Standard

22/ Mazz Mazza a

After 30 min of distillation

Vinyl acetonitrile

6.67 5.65 4.07

0.92 0.60 4.16

0.82 1.23 0.49

± ± ± ±

0.29 0.26 1.95

Allyl isothiocyanate 95.70 95.67 83.16

1.13 1.20 1.46

Allyl thiocyanate 1.21 1.23 2.02

± ± ±±

0.02 0.06 0.71

2-Phenethyl isothiocyanate 1.01 1.63 8.98

± ± ± ± ±

0.21 0.61 0.61 1.63

Others 1.21 l.2l 0.90 1.68 1.68

±± ±± ++

0.30 0.30 0.08 0.40 0.40

J. J. InSI. Inst. Can. Can. Sci. Sci. Technol. Technol. Alimenl. Aliment, Vol. VoL 17. 17, No. No. I. I, IY84 IY84

Chubey for suggestions in preparation of this manuscript.

References Bailey, S.D., M.L. Bazinet, J.L. Driscoll and A.1. McCarthy. 1961. The Volatile Sulfur Components of Cabbage. J. Food Sci. 26:163. Freedman, G.G. and R.J. Whenham. 1974. Changes in Onion (Allium cepa L.) Flavour Components Resulting From Some Post-harvest Processes. J. Sci. Fd. Agric. 25:499. Gilbert, J. and H.E. Nursten. 1972. Volatiles Constituents of Horseradish Roots. J. Sci. Food Agric. 23: 527. Grob, K., Jr. and P. Matile, 1980. Capillary GC of ~cosinolate­ derived horseradish constituents. Phytochem., 19:1789. Hashimoto, T. 1982. Personal communication. Isaac, O. and E. Kohlstaedt. 1962. Essential horseradish oils. Arch. Pharm. 295:165. Kjaer, A., M. Ohashi, J.M. Wilson and C. Djerassi. 1963. Mass Chern. Scand. 17:2143. spectra of isothiocyanates. ACTA Chem. Kojima, M. and I. Ichikawa. 1969. Gas chromatographic studies of aromatic components of Wasabi (Japanese Chern. Soc. Jap. 47:263. Chem. Chern. horseradish). J. Agric. Chem. Abs. 71:48458.

Can. [nsf. Inst. Food Sci. Se!. Technol. J. Vol. 17, No. I, 1984

Mazza, G. and M. LeMaguer. 1980. Volatiles Retention During the Dehydration of Onion (Allium cepa L.) Lebensm.-Wiss. u.-Technol. 12:333. Pate, J .S. 1968. Recent Aspects of Nitrogen Metabolism in Plants. E.J. Hewitt and C.V. Cutting, Eds., p. 219, Academy Press, London. Rhodes, A.M. 1976. Horseradish - Problems and Research in Illinois. In Crop Resources. Ed. D.S. Seigler. Academic Press, Inc., New York. P. 137-48. Schwimmer, S. and M. Friedman. 1972. Genesis of Volatiles Sulfurcontaining Food Flavours. The Flavour Industry (3): 137. J.C. Walker. 1943. Mustard oils Stahmann, M.A., K.P. Link and l.C. in crucifers and their relation to resistance of clubroot. J. Agric. Res. 67:49. Stoll, A. and E. S.eebeck. 1948. The isolation of sinigrin as the true, crystahzed mother substance of horseradish oil. Helv. crystalized Chim. Acta. 31:1439. VanEtten, C.H., M.E. Daxenbichler and LA. Wolff. 1969. Natural Glucosinolates (Thioglucosides) in Foods and Feeds. J. Agr. Food Chern. Chem. 17:483.

Accepted March 22, 1983

Mazza / 23