MW Topic of the Week: Technical Specifications

Time to get excited/scared about paper 3!

Here's a question from the 2019 exam: 

What are the key factors to consider in drawing up a technical specification for:
a white dessert wine bottled at source with 150 g/l of residual sugar; and an entry-level red wine imported in bulk with 4g/l of residual sugar.

Reading this question prompted me to do some digging on technical specifications - there are different document styles for bottled and bulk products. I've attached a technical specification sheet for bulk Australian Chardonnay/Viognier blend.

Our key understanding here is that the goal is to ensure that the bottled product will be stable when sold to the consumer, and that the bulk product will be stable when transferred for final treatment before bottling.

Who wants to chat microbes, dissolved oxygen, sulfur dioxide levels, and more!?


  • Sabrina, what would differ between the specifications of the two wines?

    I would say that both need to be sterile filtered (to .45 microns) because of the rs on both and probable lack of malo for the dessert wine. The red could wait until bottling, if transport was guaranteed stable, or Velcorin at bottling would be an option. Free sulfur (higher dosage level for higher pH red) would be similar, I would think. 

  • I'm totally there with you. I was a bit thrown through a loop because I wasn't sure what kind of filtration or treatments are common before bulk shipment. I know the wine should be microbially stable, but I don't know what kind of filtration or velcorin regimes are common.

  • I had some confusion with this question because I didn’t actually know how to define technical specification! In my mind, it is the analysis and appropriate values achieved at bottling or at bulk delivery in port. I may be off the mark here if technical specification for a bottled product is simply the tech sheet that is shared with the wholesalers, retailers, or consumers. I would love to hear thoughts on this.

    The key objective of the technical specification is that the wine arrives at the destination in a good quality and stable condition. For the dessert wine, the destination is the consumer. For the red wine, the destination is the facility for pre-bottling treatment. 

    I found this question easier to think through when I turned these examples into real wines in my mind. A white dessert wine with 150 g/L of RS is likely high quality and could be a 5-6 puttonyos Tokaji, a Sauternes, or maybe a German TBA. It may even be a boutique product. An entry level red with a tiny bit of RS could be something like Australian Riverland Shiraz. Both of these wines could possibly referment. It is worth mentioning that for a very high quality, possibly boutique dessert wine, the producer may not have a technical specification at all.

    Shared key factors

    • Microbiological stability. The dessert wine has 150 g/L of residual sugar and can referment in bottle. Additionally, the wine likely has malic acid which can also be consumed in bottle. To ensure stability, this wine should be sterile filtered at bottling. The red is also at risk for refermentation, especially if it undergoes equatorial travel. The wine should be filtered before transport and arrive in port with a clarity of <1 NTU (according to Blue H2O Filtration in Australia) so that the wine is ready for sterile bottling.
    • Heat and protein stability. Both wines should be heat and protein stable. The dessert wine will need to be heat and protein stable so that it does not show visual faults when it arrives to the consumer. The bulk red will need to be heat and protein stable when it is delivered because the finishing and bottling facility may not have the technology or time to stabilize the wine before bottling. 
    • Flavor freshness. Both wines will need to have an appropriate level of free sulfur dioxide to ensure freshness of flavor at the consumer and at delivery to bulk facility. For the bulk red, the sulfur dioxide will also act as an antimicrobial agent in transit as it is unlikely that the wine was sterile filtered before shipment. According to ETS Laboratories, molecular sulfur dioxide levels between 0.5-0.8 mg/L serve to inhibit microbial growth. For the dessert wine, a higher level of 1.0 mg/L of molecular sulfur dioxide is appropriate to provide freshness over a longer period of time as the wine is likely ageable for several decades.

    Factors specific to bulk wine

    • Additional analysis for bulk red. The bulk red wine has an entry level price point and the winery is likely interested in consistency of product. As a result, the technical specification will include other chemical analysis with tolerance ranges to ensure that the bulk wine is within the desired quality and style range. These analytes can include pH, titratable acidity, oxygen, carbon dioxide, and residual sugar. Additionally, other analysis such as copper may need to be performed to ensure that the bulk wine is compliant in the country of importation. For example, the legal level of residual copper for wines imported into the United States is 0.5 mg/L
  • Since it is a P3, I don't think it is a tech sheet, as that is a marketing tool. I found this website: but I haven't yet made use of the information. (Especially:

  • Sabrina,

    One point of confusion.  You discuss Heat and Protein stability as if they are different, but they're different names for the same thing.  Do you mean heat and cold stability?  The red will be heat stable by definition but both will need to be cold stabilized.  

    This may or may not be something people measure in reality but I wonder about things like dissolved oxygen and CO2 in bulk transport.  For example, if the wine picks up a bunch of DO when filling the shipping container it will quickly lose its FSO2.  Presumably, the wine should have minimal DO to begin with and should be transferred under gas.

    Similar thought, also on SO2/gas: How permeable/impermeable are the containers used for bulk shipping?  I've heard they can be essentially like massive bag-in-box deals, i.e. they are flexible plastic containers inside metal shipping containers. If so, they probably have some meaningful OTR and thus there will likely need to be more SO2 than just 0.5-0.8mg/L molecular.  One imagines there would need to be a buffer calculated approximately something like SO2BufferInppm=(ppmO2Ingress/Day*TravelDays)*4ppm S02/ppmO2.

    As for technical specifications, could pH play a factor here?  I'm specifically thinking again about the red wine. A red wine with sufficiently high pH would be both microbially and oxidatively at risk in a long enough transport scenario.  The pH is probably already covered by what you mentioned (tech specs for final product for consistency) but it would be important if the wine is undergoing a long transport.

  • Hi August. Sorry that I missed your comment (I didn't get a notification).

    I should have written heat/protein stable or chosen one word.

    I just got notes from a great bulk presentation by your friend Nova Cadamatre MW. :) She said Constellation adjusts to 60 mg/L FSO2 for overseas shipment.

    Yes to high pH wines being at risk. But not much we can do there!