GIycemic Index
Testing Services
GINZ Research Centre is an independent contract research organisation specialising in glycaemic index testing of commercial food products.
Our testing is conducted through controlled human clinical trials aligned with ISO 26642:2010 and internationally recognised glycaemic index methodology. We support New Zealand and international food manufacturers with clinically derived glycemic index values for product labelling, product development and commercial use.
How is GI Measured?
Glycaemic index (GI) is determined through controlled human clinical studies conducted in accordance with internationally recognised methodology.
Participants attend multiple testing sessions following an overnight fast. A reference glucose solution is tested on separate occasions, followed by the test food containing a defined amount of available carbohydrate (50g or 25g).
Blood glucose measurements are taken at regular intervals over a two-hour period. The glycaemic response of the test food is compared to the reference, and an average GI value is calculated across all participants.
GI values are then categorised as low (55 or less),
medium (55-69)or
high (70+) according to established classification ranges.
Determining the Available Carbohydrate in your Product
Before sending your test food to us, you need to have your food product tested for its Available Carbohydrate per 100 grams in a Food Laboratory. We use the value of this to calculate a 50 grams (or 25 grams) of digestible carbohydrate serving. This is the quantity of food that we feed to each participant. We cannot tell you how much test food we require until the laboratory analyses your food for direct determination of available carbohydrate.
Inform the Food Laboratory that you need the nutrient analyses for GI testing and get both Direct Determination of Available Carbohydrate as well as the Nutrition Information Panel.
How long does testing take and what documentation is provided?
The timeline for glycaemic index testing of a single product is typically approximately two weeks, from receipt of the test food and all required analytical data to delivery of the final report.
Prior to commencement, a service agreement is issued to confirm the scope of work, study design and timelines. A 50% deposit is required to initiate the project, at which point study preparation and procurement of testing materials will begin.
Testing is scheduled once available carbohydrate data from a food laboratory has been provided, as this is required to determine the appropriate test portion size.
Upon completion of testing, you will receive a detailed electronic report outlining the study methodology, data analysis and glycaemic index results.