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February (No. 493)


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Troubleshooting enzymatic analysis

Marco Vallesi , Director, Vintessential Laboratories


In many winery laboratories, the use of a spectrophotometer for analysis of parameters such as malic acid and residual sugars is an important routine quality-control check. The most common analysis involves the use of commercially-available enzymatic test kits that are highly specific to a particular parameter. It is required that a check standard be run with every batch of analyses to ensure integrity of the system and analytical technique, and a recovery of between 98-102% is considered satisfactory.

There are times when acceptable recovery is difficult to achieve. The reasons are manifold, and the remedies are not always easy to determine. In this article, we will look at common problems that you may encounter, and how they can be rectified. Three key areas will be covered:
  • equipment limitations
  • equipment maintenance checks
  • analytical technique.

In some cases, inconsistent results are not due to the analyst, but rather that the instrumentation is not fit for purpose, or may require basic maintenance. As such, part of this discussion will focus on basic operational specifications to which your system should comply, as well as some very simple performance checks.

NOTE: The complete article can be found in the February issue of The Australian & New Zealand Grapegrower & Winemaker.

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