The new conglomerate is called Aryzta and follows more than five years of collaboration between the companies. Shares began trading in the new €2.5bn company on Friday on the Dublin and Zurich financial markets.
The move has been subject to ant-trust assessment but was approved earlier in the month after being mooted in June.
When a majority (91.3 per cent) of Hiestand’s shareholders agreed the move on Wednesday the final hurdle was cleared and the new company came into existence.
"Aryzta will be the leader in value-added baked goods, serving over 200,000 customers across the globe,” said IAWS chief executive, Owen Killian.
"We will seek to build on the excellent track record of IAWS and Hiestand to deliver significant value creation to IAWS and Hiestand shareholders and bring strategic benefits for employees and customers."
Killian said Aryzta aimed to double its per-share profit in five years.
However, a small band of Hiestand shareholders said they would mount legal action because they objected to the terms of the deal. IAWS stock owners will receive one Aryzta share for every two IAWS shares held while Hiestand investors will get 36 Aryzta shares for each share held.
It is estimated the global market for frozen baked goods is worth €30bn and growing at four per cent annually in North America and Europe and more than that in developing regions such as Asia and the Middle East.
The merger follows IAWS’s acquisition of Californian cookie company Otis Spunkmeyer in October 2006 for €250m.
IAWS also has operations in the UK and has a joint venture in Canada with coffee chain Tim Hortons to produce par-baked produce for its shops.
In the US it owns the boutique La Brea bakery.
Analysts noted the success Hiestand’s baguettes and croissants were having in winning market share from Europe’s artisan bakeries.
Under the terms of the deal Aryzta will be 83.3 per cent owned by the shareholders of IAWS, 8.7 per cent owned by free float shareholders of Hiestand and eight per cent by investment firm, Lion Capital.