Volatile composition of red clover (Trifolium pratense L.) forages in Portugal: The influence of ripening stage and ensilage

The volatile organic compounds (VOCs) of three different red clover (Trifolium pratense L.) forages, fresh plant, hay and silage, were analyzed using GC and GC/MS. Comparing the volatile composition of hay and silage forages of red clover with the corresponding green plant, the effects of ripening and postharvest secondary metabolism can be noticed in hay and in ensilage. In hay, reductions of the percentages of alcohols, such as 3-methylbutanol and 1-hexanol, of aldehydes and of low boiling point ketones are observed. A sesquiterpene (β-farnesene; ca. 10%) and a phytol degradation product (6,10,14-trimethyl-2-pentadecanone; ca. 12%) were the most abundant compounds detected in hay. In silage, as a result of the fermentation of fresh red clover, esters (ca. 46%) are a more representative class of compounds.