$cache = Mage::app()->getCache();

if($cached_product_collection = $cache->load('product-collection-' . $this->getCategoryId()))
	$_productCollection = $cached_product_collection;
else{
	$_productCollection = $this->getLoadedProductCollection();
	$cache->save($_productCollection, 'product-collection-' . $this->getCategoryId(), array('product-collection'), 60*5);
}