XSLT test condition

Hi All,
I have difficulty in testing a variable matches "text/plain" and "text/html".
Based on the out come I need to disable-output-escaping="yes". Please
help , how to resolve the same.

	<xsl:template match="node()">
		<tr>
			<td><xsl:value-of select="name(.)" /></td>
			<td>
				<xsl:variable name="content_type"
select="normalize-space(preceding-sibling::Content-type[1])"/>
				<xsl:value-of select="$content_type"/>
				<xsl:choose>
				<xsl:when test="$content_type=$HTML">
				<xsl:value-of select="text()" disable-output-escaping="yes"/>
				</xsl:when>
				<xsl:otherwise>
				 <xsl:value-of select="text()"/>
				</xsl:otherwise>
			</xsl:choose>

			</td>
		</tr>
			<xsl:apply-templates />
	</xsl:template>


Thanks,
Senthil