How do food businesses determine the correct shelf life information for their products?
The responsibility of determining the shelf life of a food, and thus its best-before or use-by date, lies with the manufacturer or distributor.
Correct Food Systems can advise business on how to estimate and then test the safe shelf life of a Characteristics of the product,including the quality, form and consistency of ingredients, the moisture content, acidity levels, addition of preservatives all influence the safety of a food product, as does external factors like storage, transport and packaging of the food.
The most direct way of doing this is to conduct properly constructed storage trials on a sample of food under realistic, controlled conditions.
Correct Food Systems is not a food laboratory testing facility.
There are food testing laboratories in each state and territory that can conduct  microbiological tests for 

• Food-borne micro-organisms such as Listeria, Salmonella, Campylobacter, E.Coli, Yeasts and Moulds, Staphylococcus Aureus, Bacillus Cereus and others
• Total viable count or plate count

Some manufacturers include recommendations for handling the product after opening with regard to time and temperature.If thereare no instructions for use or storage after opening the onus is on the consumer to handle the product hygienically, store it at recommended temperatures and use it within a reasonable time, certainly within the time frame specified by the manufacturer for the unopened container.

NSW Food Authority has a useful publication to assist businesses to ascertain the shelf life and required date marking information for a product.

See our webpage "Shelflife testing"

Victoria's Health Department have published some useful factsheets and guidance material in 2017.
Whilst targetting food businesses in Victoria, the information is suitable and informative for food businesses in other states.
Each state has its own system of licencing,regulatory inspections and classification/ notification of food businesses, so please check with your local council authority or state health authority.
Information in these guidelines provide sound principles of safe food handling.

• Clean-up guidance for Listeria monocytogenes detection
  in food
  Useful guide to ensure that food businesses effectively clean and sanitise both the premises and their equipment to reduce the risk of further contamination, after a positive Listeria monocytogenes result.