A thiourea‐UV assay for total glucosinolate content in rapeseed meals

Abstract

A rapid and sensitive method for the determination of the total glucosinolate content in rapeseed is described. The method is based on the specific UV absorbance of the thioureas and oxazolidine‐2‐thiones. Results obtained were confirmed by gas‐liquid chromatography. Recoveries varying from 94 to 103% were obtained for samples containing mixtures of isothiocyanate and oxazolidine‐2‐thione (a total of 0.25 to 0.78 mg per assay). The relative stadard deviation for rapeseed meals varied from 4 to 10% for the total glucosinolate content (expressed as 3‐butenylisothiocyanate) and depended on the size of sample taken. The relative standard deviation for oxazolidine‐2‐thione varied from 5 to 35% for the same meal. The lower limit of detection for rapeseed meal is of the order of 0.25 mg of 3‐butenylisothiocyanate per g.

The glucosinolate content of Brassica vegetables. A chemotaxonomic approach to cultivar identification

“…However, chemical reactions occurring between the volatiles prior to analysis necessitated the use of associated canonical variate analysis. In the present study the most obvious factors connecting the cultivars was the presence of four main glucosinolates (see Figure I ) which have been identified as allyl-(l), 3-butenyl-(2), 2-hydroxy-3-butenyl-(3) and 3-indolylmethyl-glucosinolate ( 10). In general the amounts of glucosinolates ( I ) and (10) were much greater than those of ( 2 ) and (3).…”

“…In the present study the most obvious factors connecting the cultivars was the presence of four main glucosinolates (see Figure I ) which have been identified as allyl-(l), 3-butenyl-(2), 2-hydroxy-3-butenyl-(3) and 3-indolylmethyl-glucosinolate ( 10). In general the amounts of glucosinolates ( I ) and (10) were much greater than those of ( 2 ) and (3). When the contents of these glucosinolates are expressed as a percentage of the total, the 'patterns' shown in Figure 2 were obtained.…”

Production of mustard protein isolates from oriental mustard seed (Brassica juncea L.)

“…This factor was adopted, as it is the standard used by the food and feed industry. The concentration of glucosinolate hydrolysis products was determined by the method of Wetter and Youngs (11). Because isocyanates are the primary breakdown products of benzyl glucosinolates, and as the flavor of the product depends on the isothiocyanates-determination of glucosinolate gives the best reflection of product quality.…”

Glucosinolate Profiles in the Seed, Root and Leaf Tissue of Cabbage, Mustard, Rapeseed, Radish and Swede

“…In the meals prepared from older varieties of rapeseed, the dominant glucosinolates were 2-hydroxy-3-but-enyl glucosinolate (2-hydroxy-3-butenyl-GS) but-3-enyl-GS and pent-4-enyl-GS. Methods used to measure these glucosinolates in the past were based on the measurement of their myrosinase hydrolysis products by gas chromatography (GC) and ultra-violet spectrometry (UV) (Appelqvist and Josefsson 1961 ;Wetter and Youngs 1976 (Minchinton et al 1982). Using this technique, two novel indole glucosinolates were isolated and identified (Truscott et al 1982a,b).…”