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Sensory quality of turnip greens and turnip tops grown in northwestern Spain - page 9 / 31





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correlations between sensory traits with the content of phenolic compounds are showed

in Table 6. Data show that most correlations between glucosinolates and sensory traits

were low and non significant. The most remarkable was the negative relationship

between progoitrin with bitter and salty taste, aftertaste presistance, and stick to palate (-

0.69**, -0.60**, -0.74**, and -0.79**). Walters [23] found a very closely relationship

between bitter and sweet taste, which could be explained the negative values found in

our work for bitter or salty taste. Progoitrin is not the main glucosinolate found in leaves

of turnip greens but it has been often shown to be related to bitterness and taste

preference in Brussels sprouts [8, 12]. Progoitrin has been defined as a non-bitter

glucosinolate. However, it can be degraded enzymatically by the enzyme

thioglucosidase or by heat treatment to the extremely bitter compound goitrin [8].

The concentration of chlorogenic and sinapic acids affects considerably the

sensory quality of food, since they contribute to enzymatic browning of food products,

thus inducing their astringency and bitter taste [24]. Hydroxycinnamic acids are present

in high amounts in turnip greens. However, as far as we know, information about the

relationship between sensory traits characteristics of this crop such as bitterness, aroma

or taste with flavonoids and hydroxycinnamic acids is lacking. Thus, this work means a

real improvement in the study of nutritional quality of this crop. Some sensory traits

evaluated in turnip greens seem to have important relationships with some phenolic

compounds. For instance, moistness had positive and high correlations with total

phenolic compound content (R= 0.75**) and with total hydroxycinnamic acids (R=

0.74**) whereas stalk firmness had positive and high correlations with

hydroxycinnamic acids (R=0.85**). Even if glucosinolates and flavonoids are not

structural compounds of the plant, it seems that there are a kind of relationship among

plant structure and these compounds, which could be related to the plant health status

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