Glucosinolate of land cress (Coronopus didymus) and its enzymic degradation products as precursors of off-flavor in milk---a review

Abstract

Land cress (Coronopus didymus) is a cruciferous weed which imparts a burnt, unclean flavor to milk when ingested by dairy cows. This off-flavor, unlike many weed taints, is intensified by heat treatment and cannot be eliminated from milk or cream by conventional vacuum pasteurization techniques. Land cress contains the glucosinolate, glucotropaeolin, from which benzyl cyanide, benzyl isothiocyanate, and benzyl thiocyanate are liberated enzymically when the plant is crushed. Benzyl methyl sulfide and benzyl mercaptan have been considered responsible for the off-flavor, the former having been isolated from cress-tainted cream.Benzyl thiocyanate appears to be a key intermediate in offflavor formation. Complete elucidation of the chemical nature of the land cress off-flavor and its precursors has important practical value in the development of methods for control or removal of a taint which has caused significant economic loss to the dairy industries of several countries. Certain feeds and weeds consumed by dairy cows have long been recognized for their contribution to the appearance of abnormal and undesirable flavors in milk and its products. Several general reviews of this subject are available (Babcock, 1938; Conochie, 1950;Parks, 1967; Strobel et a/., 1953). Onions, fermented silage, alfalfa, cabbage, turnips, rape, beet tops, musty hay, and distillers' grains impart off-flavors to milk, but these can usually be avoided by controlled feeding practices. Many varieties of weeds, when ingested by cows, impart taints to milk, and in some cases only minimal consumption of a weed is required to produce a strong off-flavor. The consumption of weeds by dairy cows is more difficult to control than the basic feeding regime. Nevertheless, the incidence of weed taints in milk can be greatly reduced by good pasture management practices.

Tipping the Scales ‐ Specifier Proteins in Glucosinolate Hydrolysis

“…While the formation of simple nitriles and epithionitriles is widespread within glucosinolate-containing plants, organic thiocyanates are only generated in very few plant species including Coronopus didymus, Eruca sativa, Lepidium ruderale, L. sativum, and Thlaspi arvense (Brassicaceae) (15,33,34). Furthermore, only three glucosinolates, namely allylglucosinolate, 4-methylthiobutylglucosinolate, and benzylglucosinolate ( Fig.…”

Mechanisms of formation of aroma compounds in milk and milk products

“…Six benzyl compounds (disulphide, isothiocyanate, mercaptan, methyl sulphide, nitrile and thiocyanate) have been implicated. Benzyl thiocyanate, present in the crushed plant, contributes to the flavour of unheated cream, while benzyl a-toluenethiol, considered responsible for the scorched flavour(23), may be formed from the disulphide through reduction by SH-groups generated during heat-treatment (75).…”

Réponses électroantennographiques de deux parasitoïdes Ichneumonidés, Diadromus pulchellus et D. collaris, aux odeurs de végétaux, du phytophage‐hôte Acrolepiopsis assectella et du partenaire sexuel

“…Les m~mes constations justifient l'hypoth~se de l'installation possible de D. pulchellus sur ce phytophage (Lecomte & Thibout, 1984). Bien que les thiocyanates aient rarement 6t6 identifi6s dans les Cruci-f~res (Walker & Gray, 1970;Cole, 1976), le TCN-M aurait, par son action sur le comportement locomoteur de D. pulchellus (seul 6tudi6), un r61e important.…”

“…Seul diff~re le montage t~te-antenne. I2apex du dernier segment de l'antenne droite, seule utili-s6e, est coup6 et on l'introduit imm6diatement dans une micropipette remplie d'une solution de composition proche de celle de l'h6molymphe des insectes (Visser, 1979) (Walker & Gray, 1970;Cole, 1976), le dithi6pane, disulfure cyclique de structure mol6culaire voisine des autres disulfures, le dim6thyle sulfoxide (DMSO) produit de synth6se b. 1 atome de soufre.…”