Mr Daifallah is accused of leaving a "trail of stench"
A shopper saw a man squirt a foul-smelling brown liquid over frozen chips in a Tesco store in Gloucestershire, Bristol Crown Court has been told.
Sahnoun Daifallah, 42, of Bibury Road, Gloucester, denies squirting a mixture of urine and faeces at four businesses last May.
Alison Harris told the court she was suspicious of the way the man was holding a laptop bag in the food aisle.
"I was taken aback... there was a strong smell of urine," she said.
"I became aware of him about three to six feet away from me in the chip aisle and thought he was suspicious because of the way he held his bag.
"I noticed a projectile spray from the bag on to the frozen food, like something from a sports bottle, it was instantaneous."
The court was told he then moved on to the wine section where a shop assistant also saw a fine vapour come out of the bag and on to the red wine and champagne, leaving a trail of brown fluid.
The store was closed for two days while it was cleaned, with the cost of repairing the damage running to £421,000.
Mr Daifallah is then said to have driven four miles to the Morrisons store in Abbeydale where an employee in the wine section noticed him acting strangely, before the smell and brown splatters were discovered
Two days earlier the Algerian-born chemist visited the Air Balloon Pub, in Birdlip, near Cheltenham moments before a stench and brown liquid was found sprayed around the pub, the court heard.
He is then alleged to have moved on to the Waterstones bookstore in Cirencester where the jury heard he spread the brown liquid over the toilet in the coffee shop.
It was not until the next morning staff noticed a large number of books had been sprayed, the court heard.
Mr Daifallah, who is defending himself, pleaded not guilty to four charges of contaminating goods and two charges of damaging property.
He also denies possession of material to contaminate goods and having an offensive weapon.
The case continues.