MW Topic of the Week - Pre- and Post-Bottling Analysis

Hi all

A dive back into paper 3 with pre- and post-bottling analysis.

What analyses should be carried out at the winery pre- and post-bottling to ensure that a wine is in good condition and conforms to legal requirements for sale?

This is a bit of a two-fer, we should know the what/why on analysis, but we also need some good legal requirement examples. I'm going to search for EU requirements on sulfites and allergens.

Cheers,

Sabrina Lueck

  • You can tell I’m more than a bit behind on my studies. Here are my notes, 2 weeks late.

    Intro paragraph

    Establish that pre and post bottling analysis are often looking at similar things. Pre-bottling analysis is to see if something needs to be changed. Post-bottling analysis is to confirm and establish a final number for records.

    Note that for certain countries allergen statement is required on label. This statement is related to use of allergen, not final concentration. Therefore, analysis for residual compound is not required.

    Note that “should” doesn’t mean “always”. Many boutique wineries are light on analysis, especially if they produce red wines which are sugar and malic dry.

     

    Free and total sulfur dioxide concentration

    Why: sulfur dioxide is the key anti-oxidant compound present in the finished wine. Pre-bottling analysis will determine if the free sulfur dioxide concentration needs to be adjusted up to achieve a target value in bottle. Total sulfur dioxide values will determine if the wine is within the legal limits for the style and region. This is especially important for very sweet styles where high amounts of sulfur dioxide may have been used during the winemaking process and the total value may be approaching the legal limit. (Example: EU sweet botrytis styles including beerenauslese, trockenbeerenauslese, sauternes, and tokaji have a legal limit of 400 mg/L). (Counter example: some boutique producers of dry still styles do not analyze for total sulfur dioxide, Artifex Wine Co custom crush in Walla Walla, USA does not analyze for total sulfur as no wines are approaching the USA legal limit of 350 mg/L).

    Dissolved oxygen concentration

    Why: 1 mg/L of dissolved oxygen will consume 4 mg/L of free sulfur dioxide. If dissolved oxygen levels are too high, all free sulfur dioxide can be consumed and the wine is vulnerable to oxidation in bottle. (Example: a wine with 7 mg/L of dissolved oxygen will remove nearly all the free sulfur dioxide in a wine bottled at 30 mg/L of free.)

    Protein and tartrate stability

    Why: to ensure that the wine does not produce a haze or deposit in bottle under industry standard storage conditions. This analysis is only performed pre-bottling.

    Ethanol

    Why: This is mainly a confirmation of previous ethanol value for records. The wine was likely analyzed for ethanol during the blending process to ensure that the wine conforms to regional requirements.

    Residual sugar in wines with sweetness

    Why: To ensure that the wine conforms to the legal requirements for residual sugar in specific styles. (Example: EU sparkling wines have sweetness brackets, an “extra dry” sparkling wine must be 12-20 g/L.)

    Additional pre-bottling analysis for controlled chemicals/additives

    Why: To confirm that wine is within the legal limits for certain fining or stabilizing agents. (Example: the residual level of copper in the USA and Australia cannot exceed 1 mg/L. Antioxidant ascorbic acid cannot exceed 300 mg/L in Australian wines). Note: this analysis is optional if chemicals with legal limits are not used.

    Microbiology

    Why: To ensure the microbiological stability of the wine. If a dry wine is bottled unfiltered with microbes, there is still a risk of bloom in bottle by Brettanomyces (if Brett cells were present). Wines that undergo sterile filtration at bottling should have post-bottling microbiology checked to ensure sterility. (Example: E&J Gallo performs sterility testing on bottled wines and finds that 2% of bottles have microbial contamination)