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Another whack of the dragons tail: Problems with label sugar contents for China

As a wine export destination, China appears very attractive: a huge and growing middle class, increasing disposable income and an emerging interest in Western culture – such as wine.

However, cracking the Middle Kingdom is not as easy as it seems. First a very low limit on manganese was announced early in 2014, and now restrictions governing the sugar content on labels, complicated by the use of antiquated testing methods by the Chinese authorities, has caused more headaches for still wines exported to China. In particular the use of a reducing sugar test by the Chinese, rather than the enzymatic test for glucose + fructose as commonly used in Australia, and the need to place a statement about sugar levels on labels are the cause of these problems.

Recent AGWA advice
The Australian Grape and Wine Authority (AGWA) recently sent two urgent notices to exporters about issues with sugar content label statements for wine destined to China. On the latest advice dated 17 October 2014 it recommended that “…to minimise the potential for compliance problems wine labels must include a descriptor such as “dry”, “medium dry” “sweet” etc.”. It also stated that “Given the difference in sugar testing methods between Australia and China the inclusion of the actual sugar level may present significant compliance problems in China”.

At first glance this does not appear to be a big problem, however there is a whack in the dragon’s tail and it is this – sugar content is tested by the Chinese authorities using older methods that can produce results that differ greatly from the more modern methods used in Australia, and the Chinese do not allow any tolerance for variation between these test results.

Chinese regulations
The Chinese regulations (1) state that a still wine must either have a statement such as “Dry” (up to 4 g/L of sugar) or “Semi Dry” (between 4 and 12 g/L of sugar); or the actual sugar content on the label. Please note a different classification is in place for sparkling wines.

The latest AGWA advice is that it is best to use the relevant statement (e.g. Dry or Semi-Dry) rather than placing the sugar content on the label (e.g. 2.5 g/L sugar).

According to Steve Guy (2), Compliance Manager at AWGA, there are 2 reasons why it is best not to place the actual sugar content on your labels:
1. there is no tolerance for differences between your sugar results and those of the Chinese testing authority, as there is for alcohol (which has a tolerance of +/- 1% v/v).
2. the Chinese authorities use a reducing sugar test rather than the more commonly used enzymatic test for glucose + fructose.

Reducing sugar tests
A relatively simple (and now well known) test for sugars was determined by Dr. Fehling in the mid-19th century. This involved an oxidation/reduction reaction involving copper (II) salts in alkaline solution with some sugars. The sugars that reacted in this test became known as “reducing sugars”. The popular Clinitest tablets use this chemistry in a simple way to check the level of reducing sugars.

This technique of reducing copper (II) salts by sugars in a titration with Fehling’s reagents was further improved by the English chemists Lane and Eynon in the 1920s, although this is still a labourious and cumbersome technique. In the mid-20th century Dr. Rebelein from Germany further improved the reducing sugar test, this technique is now known as the Rebelein titration.

Using the Rebelein (or Lane and Eynon) reducing sugar test will typically give a result of 1 to 2 g/L for dry wine (3). This figure will include the non-fermentable pentose sugars.
These reducing sugar tests are not the most accurate, and are certainly not the easiest or most efficient to perform. 

Enzymatic tests
Importantly, part of the reducing sugars – the fermentable sugars glucose and fructose, can be very accurately measured by enzymatic analysis. It is crucial to know the level of these sugars accurately because of their potential influence on the microbial stability of the wine. For example, yeasts such as Saccharomyces and Brettanomyces can grow and metabolise glucose and fructose at levels less than 2 g/L (4). So the enzymatic test for glucose and fructose is very popular in the New World. This is because it is easier and quicker to perform, and more precise, with better repeatability data than the reducing sugar tests.

Differences between Enzymatic and Reducing sugar test results
Vintessential Laboratories is ISO 17025 accredited for sugar testing by both enzymatic and reducing sugar techniques, although we mainly use enzymatic testing for the reasons stated above. An analysis of our results where both tests were performed on the same wine for multiple wines over the past 2 years shows that there is an average difference between the two techniques of 1.8 g/L, the reducing sugar test result always the higher. The smallest difference was 0.7 and the highest 3.4 g/L.

This suggests that the level of pentoses (the non-fermentable sugars) varies between wines, and more importantly can give a large difference between the tests of up to 3.4 g/L. That is, there can be up to 3.4 g/L difference between the current test methods used in Australia and that used in China, for the same wine.

During fermentation all the “fermentable sugars” can be consumed; using the modern technique of enzymatic analysis, a level of <0.10 g/L is commonly cited as a dry wine. However there will always be some left over pentose sugars that have not been fermented - importantly these are not measured by the modern enzymatic technique, but are measured by the older reducing sugar tests.

So herein lies one problem: the same wine may end up legitimately with say 3.0 g/L for sugars by the enzymatic test but get 5 g/L by the Rebelein test. Due to there being no tolerance for difference in sugar contents, the enzymatic test results should therefore not be used for label purposes for China.

Problems for wines near the label limits
As mentioned, the Chinese authorities require either a sugar content (e.g. 2.5 g/L) or a sugar statement (Dry, Semi-Dry etc.). AGWA have recommended that the sugar content not be included on the label; we strongly concur.

However there is an issue with the use of the statements, particularly where sugar levels are close to the boundary between styles (Dry is less than 4 g/L, Semi-dry is 4 to 12 g/L). The Chinese regulations also allow the acid level to be taken into account – this makes the situation even more complex. Please refer to the Export Market Guide for China from AGWA for details (1).

As an example, if your wine has a reducing sugar content of say 3.8 g/L as determined by an Australian ISO17025 accredited lab, it follows that you would choose the descriptor “Dry” for the sugar statement.  However due to inbuilt uncertainties in test methods there will always be some variation between repeat tests within the same laboratory. A typical uncertainty for the Rebelein test is around 0.5 g/L. This means that we could get 3.8 or 4.3 g/L and this is still within the acceptable tolerance for this test method. This demonstrates the lack of precision of this method, and why we don’t rely upon it!

This is the difference within one lab – commonly called repeatability. Statistically there is always a larger difference between 2 different labs – known as reproducibility.

The reproducibility for this test between Vintessential and the Chinese lab could be at least 0.5 g/L. So for the wine in the example above with (3.8g/L) the Chinese may get 4.3 g/L. According to ISO17025 rules, this is entirely acceptable. However it would mean that the Chinese would deem the wine to fit into the “Semi-Dry” category and your wine would not meet their regulations!

In these circumstances you would have the options of:
-labelling the wine as “Semi-Dry”
-checking the acid level to see if “Dry” is still valid
-blending the wine to a lower sugar level
-or not exporting that wine to China.

For successful and stress free exporting to China, we offer the following recommendations:

1: Wine bound for China should be tested for sugar content using a reducing sugar test by an accredited laboratory.

2: If your reducing sugar result is close to a limit defined by the Chinese regulations, e.g. “Dry” at 4 g/L sugar, then consider taking other options.

1. AGWA Export Market Grid for China,

2. Steve Guy, personal communication

3. Iland, P; Bruer, N; Edwards, G; Caloghiris, S; Wilkes, E; Chemical analysis of grapes and wine: techniques and concepts, 2nd Edition, Patrick Iland Wine Promotions Pty Ltd, South Australia, 2013, p 66

4. Zoecklein, B.W; Fugelsang, K.C; Gump, B.H; Nury, F.S; Wine Analysis and Production, Aspen Publishers Inc., New York, 1995, p 91

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