The companies had previously pleaded guilty to four health and safety breaches over the incident.
The blast happened after petroleum gas ignited in a pipe which had corroded in the cellar of the factory building.
Passing sentence on Tuesday, Lord Brodie said the fines were not intended as any sort of reparation for the lives lost, or injuries suffered in the explosion.
He said he had to balance the fine against the companies' intention to continue trading and also provide employment for the workforce.
Lord Brodie also told families of the victims and injured sitting in the back of the court that the lives of their loved ones 'were not capable of being expressed in terms of money.'
The court heard on Monday the first detailed official account of the accident.
The explosion was caused by a build-up of liquid petroleum gas (LPG) which leaked from pipework installed in 1969 - and may have been ignited when a labourer switched on a light in the basement.
A statement issued on behalf of the families of victims Annette Doyle, Peter Ferguson, Kenneth Murray, Tracey McErlane, Tim Smith, Ann Trench and Thomas McAulay branded the fine 'inadequate'.
It said: 'No amount of money can account for the loss of life or the decimation we have suffered in our lives. No court case will provide any explanation as to why they died'.
'Over the last day-and-a-half we have listened to how little it would have cost to replace the pipework that subsequently leaked, leading to the death of our loved ones'.
'Unfortunately the justice process that we have now completed probably raises more questions than it has answered.'
The statement ended: 'The current legal system is too restrictive and until company directors face personal prosecution for their negligence, families will never receive justice.'
The families also reiterated their desire for a full public inquiry into the blast, along with the fatal accident inquiry that is already planned.
The lord advocate is currently considering whether a public inquiry will be held and a decision is expected within a month.
Elish Angiolini said she was in the process of deciding what type of inquiry would be most appropriate and would consult the families of those who died as well as looking at issues identified during the police and health and safety executive investigations.
A statement issued by both companies following the verdict said their thoughts remained 'with those people most affected by the tragedy - the victims, their families, and all who were injured.'
It added: 'The information brought to light by the complex technical investigation and subsequent court proceedings will, we hope, have provided meaningful answers to many of the questions surrounding this terrible tragedy'.
'Since May 2004, all concerned have made enormous efforts to sustain the companies and to maintain the employment of our workforce'.
'The heroic input from so many who were injured in the blast, and the loyalty and support of many others, is the reason for the companies' survival to this day.'
It went on to welcome 'any form of inquiry that will properly establish all the facts and circumstances relating to the disaster.'
Stewart Campbell, director of the Health and Safety Executive in Scotland, said it was important that lessons were learned from the case.
'I would like to remind all users and suppliers of LPG of the risk from buried pipes carrying LPG, particularly when located near areas where gas can accumulate', he said.
'Everyone should ensure that problems which are out of sight are not out of mind'.
'The dangers posed by buried pipes can be overcome by a systematic approach to risk management and the findings of the investigation reinforce the need for effective arrangements for the maintenance, renewal or repositioning of buried pipes.'
He added: 'I would like to pay tribute to all my staff and those of HSL who have dedicated much of the last three years to the investigation and who responded magnificently to what has been an extremely testing investigation.'
Grahame Smith, general secretary of the Scottish Trade Unions Congress (STUC), called for individual directors to be held liable for the health and safety failures of their companies.
He said: 'No level of fine can adequately reflect the loss that these families have suffered. Our justice system appears to be totally inflexible in the sentences that judges can impose following breaches of health and safety legislation.'