An elderly muesli company boss who murdered his business partner, with whom he had a father-daughter-like relationship, has been sentenced to 17 years in jail.

In sentencing 76-year-old Peter Pavlis on Thursday, Supreme Court of Victoria Justice Lesley Taylor admitted there was a 'very real chance' the founder of The Muesli Company would die in jail.

On July 25, 2017 Pavlis fatally stabbed Jennifer Borchardt, 49, in the kitchen of her Richmond home, in a 'frenzied stabbing attack using a single edged weapon' out of 'jealousy or anger', the court heard.

Pavlis was like a father figure to Ms Borchardt, who had worked at the Muesli Company continuously since high school and had become a trusted co-owner.

He pleaded guilty to murder in July this year, however Justice Taylor said Pavlis' motive remained unclear.

'The horror of her last moments can barely be imagined. You were a man very much trusted by her,' she said.

Prosecutor Mark Rochford SC had said earlier that Pavlis may have become jealous of Ms Borchardt's relationship with her boyfriend.

Ms Borchardt had been living with her boyfriend Robert Hansen, who she'd met about six months earlier.

After the murder, Mr Hansen returned home to find Ms Borchardt's lifeless body on the floor, covered in blood.

Ms Borchardt died from multiple stab wounds to her neck and chest and had defensive wounds on her hands, an autopsy found.

The court heard that Pavlis tried to clean up the scene and avoid detection immediately after the killing but pleaded guilty at an early stage.

At a previous Supreme Court hearing, colleagues spoke of the heartbreak of losing Ms Borchardt.

'She trusted you and always wanted to protect you from any hurt or harm. Ironic, isn't it?' Rosa Cornelia told the court.

'I still can't understand for the life of me how you could've come to work that Tuesday as if nothing had happened.'

Ms Borchardt's aunt Carlie Smith described Pavlis' actions as those of someone who was 'pure evil'.

'It disgusts me. You left her lying there, helpless, afraid and dying,' she said.

After Ms Borchardt's supporters gave their emotional statements, Pavlis asked the judge if he could speak too.

'I'm sorry,' he said slowly as he stood in the dock, 'What I did I had no right to do. I still can't understand how I did it.

'She was a nice person and I couldn't have done anything without her.'

The killer will be eligible for parole after 12 years imprisonment.

The Muesli Company, started by Pavlis in 1984, operates from Thomastown and produces wholegrain breakfast cereals.