Hanna Instruments HI 83746 User Manual

Page 3

The HI 83746 is an auto-diagnostic portable microprocessor meter that benefits from Hanna’s
years of experience as a manufacturer of analytical instruments. It has an advanced optical system
based on a special tungsten lamp and a narrow band interference filter that allows most accurate
and repeatable readings. All instruments are factory calibrated.
The auto-diagnostic feature of this meter ensures always optimal measurement conditions to
ensure most precise readings. The light level is automatically adjusted each time a zero-measurement
is made, and the temperature of the lamp is controlled to avoid overheating.

GENERAL DESCRIPTION

The determination of concentration of reducing sugars (RS) is one of the most important parameters
that need to be measured during the wine making process.
Following the increase of RS during maturation of grapes can help to decide when to start harvest.
Having the highest possible sugar content is important because this is the main parameter that
defines the commercial value of grapes.
During the alcoholic fermentation instead, the decrease of sugars can be followed to decide when
fermentation is completed, or allows making corrective actions if the content of RS is too low to
obtain the desired alcohol degree or sweetness.

The predominant RS in grape products are glucose and fructose (hexoses). After reaction with excess
alkaline cupric tartrate (Fehling reagents), the RS content can be determined colorimetricly. The
Fehling method is not an exact determination but an index of the reducing sugar concentration,
because the reaction depends upon the amount and kind of RS present. When the reducing sugar
content is known at the beginning of fermentation, the potential alcohol degree can be estimated
multiplying the sugar concentration (in g/L) by 0.06.
Phenols interfere in the Fehling reaction and therefore red wine must be decolorized prior to analysis.
Wine also contains non-fermentable reducing sugars like pentose which will also be analysed by this
method.

Typical content of reducing sugars in must and wine
Must

sweet must

20-25 %

200-250 g/L

normal

10-20 %

100-200 g/L

in fermentation

4-12.5 %

40-125 g/L

Wine

Sweet

2.5-12.5 %

25-125 g/L

Semi sweet

0.8-2.5 %

8-25 g/L

Almost dry

0.2-0.8 %

2-8 g/L

Dry

0-0.2 %

0-2 g/L

SIGNIFICANCE OF USE

Range

0.00-50.00 g/L

Resolution

0.25 g/L

Precision

±0.50 @ 10.00 g/L

Light Source

Tungsten lamp with narrow band interference filter @ 610 nm

Light Detector

Silicon Photocell

Method

Fehling Method

Environment

0 to 50°C (32 to 122°F); max 95% RH non-condensing

Battery Type

4 x 1,5 volt AA batteries / 12 to 20 VDC through voltage adapter

Dimensions

224 x 87 x 77 mm (8.7 x 3.3 x 3.1")

Weight

512 g (17,6 oz.)

REQUIRED REAGENTS
Code

Description

Quantity/test

HI 83746A-0

Fehling solution A

1 vial

HI 83746B-0

Fehling solution B

1 mL

OPTIONAL REAGENTS
Code

Description

Quantity/test

HI 93703-59

Charcoal

2 spoons

SPECIFICATIONS

Precision is how closely repeated measurements agree
with each other. Precision is usually expressed as
standard deviation (SD). Accuracy is defined as the
nearness of a test result to the true value.
Although good precision suggests good accuracy,
precise results can be inaccurate. The figure explains
these definitions.
In a laboratory using a standard solution of 10.00 g/L of
Reducing Sugars and a representative lot of reagent,
an operator obtained with a single instrument a
standard deviation of ±0.50 g/L

PRECISION AND ACCURACY