Craig Lindsay, of Upper Hutt, asks :-

How much real grape is in our New Zealand wines and how much is required by law? Why don't they tell us?

Sue Blackmore, an oenologist (wine expert) at Lincoln University, responded.

A good question - what does go into wine? In quality wines made in New Zealand - the best possible (for the year) grapes! There are small additions to help maximise and maintain quality of the wine. Small additions to preserve the wine from oxidation (e.g. ascorbic acid, sulphur dioxide), possibly tiny additions of fining agents (e.g. egg whites) to remove phenols that may give astringency or bitterness and even a clay (bentonite) is sometimes added to remove troublesome unstable proteins from white wines that could cause a haze in the wine after it is bottled.

There have been world scandals involving inappropriate additions. In 1985 a small number of producers of Austrian wine were found to be adulterating their product with diethylene glycol in order to give the wine a sweeter and more full-bodied taste. The amount added was not high enough to be immediately toxic (one would have to ingest about 28 bottles per day for two weeks!); however, exports of Austrian wine collapsed and the industry took a long time to recover.

The New Zealand industry is self-policing with it being in everyone's interest to maintain the NZ Wine brand reputation for quality. There are also rules about what can go into our wine (or anything we consume) that are well defined by acts of parliament (e.g. the Wine Act of 2003) and policed by the Ministry of Primary Industries (previously NZ Food Safety Authority).

The rules have changed over time and certainly there has been considerable 'tightening up' over the last 40 years. If we look at relatively recent history - in 1981 the following amendments were made to the relevant Food and Drug regulations. 'The amount of grape juice used in the manufacture of any wine shall at least be 80% of the finished wine And Wine labelled as 'premium',' private bin', 'directors reserve' and the like must at least be 95% grape juice by volume'. Meaning that before 1981 winemakers could legally include more than 20% (and 5% respectively) of something else - possibly fruit juice. In 1983 the following amendment was made - All New Zealand wine must be made wholly from locally produced grapes and increased the required minimum from 80% to 100% grape juice was required for all wines. So since then all New Zealand wine must be made of 100% grape juice.