(recasts with new quotes, details) By Martyn Herman ALCUDIA, Mallorca, Jan 10 (Reuters) - Team Sky unveiled the sleek black machine they hope will propel Chris Froome to a fourth Tour de France triumph but the contents of a humble jiffy bag was the main talking point as their Mallorca pre-season camp continued under a cloud on Tuesday. After a handful of media got the low-down on the latest bicycle to roll out of the Pinarello factory - the Dogma F10 -team boss Dave Brailsford was again weighed down by questions regarding the ongoing UK Anti-Doping (UKAD) investigation into a package delivered to Bradley Wiggins six years ago. Brailsford's appearance in front of a British Parliamentary committee last month, when he was cross-examined about what exactly was in the package which arrived at the 2011 Criterium du Dauphine, as well as his team's use of Therapeutic Use Exemptions (TUEs), failed to dispel suspicions of wrongdoing. More...