D-Glucose and D-Fructose
D-Glucose and D-Fructose (Glu-Fru) represent the vast majority of naturally occurring sugars in grapes. They are fermentable and can be oxidized or reduced to form other derivatives in winemaking that are fundamental to wine’s matrix. Together, Glu-Fru can be used to estimate the potential alcohol of an unfermented must or characterize dryness at the end of fermentation. A symptom of many stuck fermentations is residual D-Fructose due to a slight preference in D-Glucose uptake during glycolysis, which is why many yeasts used for restarting stuck fermentations are “fructophilic”. Whether or not a winemaker decides to incorporate residual sugar into the finished wine is an important stylistic decision because sweetness changes flavor and mouthfeel characteristics such as sourness, bitterness, astringency, and body (Lawless and Heymann, 2010).
To learn more about Glu-Fru and its importance in winemaking, become a Bound member.
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FAQs
Frequently Asked Questions
Sample
- Use a 50 mL centrifuge tube with a Bound Sample Label attached.
- Sample your wine in a way that is most representative of the entire lot (i.e. practice flushing your sample valve, collecting after movements like pumpovers, stirring your barrel, etc.).
Label
- Label each sample appropriately with your Client ID, Sample Date, and Sample ID. Samples for Phenolics analysis also require a Crush Date, Varietal, and Appellation. The analysis cannot be performed without the applicable information for each sample.
- Mark the sample type. This is critical for applying the appropriate model for each sample. ”Juice” applies to grapes and juice samples before fermentation. ”Must” applies to samples undergoing primary or secondary fermentation. ”Wine” applies to samples after fermentation and includes SO2 analysis.
- In addition to sample type, you must also select the panel and/or the individual analyses for each sample. For panels, select “Standard” for our juice, must, and wine panels, or select “Phenolics” for our phenolics panel. These panels may be selected individually or in conjunction with one another. For individual analyses, write each parameter at the bottom of the label. A list of individual analyses is on our ANALYSES page.
Beginning the week of August 26th, 2024, clients will be able to submit samples directly to our lab, via the mail, or arrange for pickup at select locations.
To arrange for pickup, clients must be located near Santa Barbara, Goleta, Buellton, or Lompoc and notify us by 10 am for same-day retrieval. Please contact us for more information.
- We strive to provide same-day results for our clients and guarantee turnaround within 24 hours of sample receipt.
- Those that are not analyzed same-day are refrigerated overnight and analyzed first thing the next morning.
- Results are delivered via email in PDF format.
- Our invoices are sent via email and are due upon receipt.
- Your payment is securely processed through Bound’s website. Click the link in your email to be directed to our payment page.
To ensure their stability, we ask our clients either freeze or boil their juice / fermenting wine samples before shipment. Please note that boiling or freezing your samples may influence your results and we cannot guarantee their validity. Please contact Bound with any additional questions about sample preparation before shipment. We recommend expedited same-day to one-day shipping with a tracking number included.
Frozen
Samples can be placed in a freezer 24-hours in advance and shipped with an ice pack. Do not over-fill the polypropylene tubes or use glass containers as the frozen liquid will expand and could pose a safety concern. Freezing samples is a better alternative to boiling when analyzing compounds like ethanol, volatile acidity, free sulfur, and phenolics. Label each sample as "FROZEN".
Boiled
Samples can be boiled in their 50 mL polypropylene centrifuge tubes with a loosely fitted cap on top. Polypropylene tubes can be boiled up to 10 minutes, but be sure not to over boil as exposure to high temperatures can change your results. Label each sample as "BOILED".
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