Methods for determining the degree of maturity of the grape for harvesting

Category: Oenology | Tags: #  #  
Methods of determining the degree of ripeness of grapes are divided into subjective and objective methods.

subjective methods

If we talk about subjective methods, we divide them according to the appearance of the berry (the strongest color and pronounced ash of the skin, the flesh becomes softer, the berries are easily torn from the stalk, the grapes are sweet and the grape juice is sticky …) and calculation according to one of the earlier phenophase (cycle of vegetative development of the vine).

objective methods

If we talk about objective methods, they are based on the chemical composition of the mast, through the index of maturity, phenolic maturity and aromatic maturity.
Grape ripeness index (index of maturity) is one of the most widespread methods. The maturity index is expressed as the ratio of the sugar content and the titratable acidity of the must.
Testing grape maturity

Sugars

The sugar content is measured using various refractometers. The most common sugars in must are glucose and fructose, generally in a ratio of 1: 1. Refractometers that measure in Brixes, measure the degree of sugar molecules that reflect light as it passes through a prism with the degree of refraction associated with the concentration of sugar. Sugars are easy to measure and are a common measurement in the wine industry, but it is not a good measure of maturity when used alone. It is important to know the concentration of sugar because 1 g of sugar during alcoholic fermentation produces 0.59 mL of ethanol.
Hanna Instruments has various of refractometers for wine makers. You can choose between 5 different refractometers. Meet them all!

HI96816

Digital Refractometer for Potential Alcohol (% V/V) Analysis in Wine, Must and Juice According to EEC
The HI96816 is a rugged, portable digital refractometer designed for potential alcohol measurement (% V/V) of wine, juice and must according to the European Economic Community Commission Regulation No 2676/90. The HI96816 features simple two-button operation and has a high accuracy of 0.2% V/V potential alcohol. All readings are automatically compensated for temperature variations according to the ICUMSA Methods Book standard and displayed within a 1.5 second response time. The sealed flint glass prism and stainless steel well, are easy to clean. Just wipe with a soft cloth in preparation for the next sample.

HI96814

Digital Refractometer for % Brix, °Oe and °KMW Sugar Analysis in Wine, Juice and Must
The HI96814 is a rugged, portable digital refractometer designed for sugar (% Brix, °Oe and °KMW) measurement of wine, juice and must. The HI96814 has a high accuracy of ±0.2% Brix, ± 1 °Oe and ±0.2 °KMW. All readings are automatically compensated for temperature variations according to the ICUMSA Methods Book standard.

HI96813

Digital Refractometer for % Brix and Potential
Alcohol (% V/V) Analysis in Wine, Must and Juice
The HI96813 is a rugged, portable digital refractometer designed for sugar (% Brix) measurement and potential alcohol measurement (% V/V) of wine, juice and must. The HI96813 features a high accuracy of ±0.2% Brix and 0.2% V/V potential alcohol. All readings are automatically compensated for temperature variations according to the ICUMSA Methods Book standard and displayed within a 1.5 second response time.

HI96812

Digital Refractometer for Sugar (°Baume) Analysis
in Wine, Must and Juice
The HI96812 is a rugged, portable digital refractometer designed for sugar (°Baume) measurement of wine, juice and must. The HI96812 features a high accuracy of ±0.1 °Baume and simple two-button operation: one button to calibrate and another to take a measurement.

HI96811

Digital Refractometer for Sugar (% Brix) Analysis
in Wine, Must and Juice
The HI96811 is a rugged, portable digital refractometer designed for sugar measurement of wine, juice and must. The HI96811 reports sugar content as % Brix and has a high accuracy of ±0.2%.
Titratable acidity (TA)
In grapes, the predominant acids are tartaric, malic and citric acids. Malic and tartaric acids contain more than 90% of the total acids present. The titratable acidity is determined titrametrically with NaOh solution, neutralizing all acids and their acid salts to an end-point of 8.2 pH for tartaric acid. Tartaric and malic acid are the most common in must. Titratable acidity is expressed as either the percentage acidity (% TA) or grams of acid per liter where 1 % TA is equivalent to 10 g/liter TA. Acid level generally fall between 0,6 and 0,8 grams of titratable acids/100mL (%TA) at harvest.
Measure titratable acidity and so much more with

HI931

Automatic Potentiometric Titrator
The Titrator is perfect for winemakers who need accurate results, ease-of-use, and the ability to expand the system as their analytical needs grow. It comes preloaded with methods for wine analysis, and with Hanna, you get the support you need to run them perfectly in your lab.
Titrate for a variety of measurements including pH, Total Acidity, Free & Total Sulfur Dioxide, Formol Number, Volatile Acids, Reducing Sugars, and many more.
Hanna’s Titrator can come preloaded with methods for wine analysis, and with Hanna, you get the support you need to run them perfectly in your lab.
For smaller wineries and hobbyists we have another mini solution.
>>> Meet

HI84502

Titrator for Measuring
Titratable Acidity in Wine
The HI84502 is a simple, fast, and affordable automatic mini titrator designed for testing total acidity levels in wine. Based on an acid-base titration method, this mini titrator uses an optimized preprogrammed method of analysis with a powerful algorithm that determines the completion of the titration reaction by the use of a specialized wine pH electrode. Analysis for titratable acidity with the HI84502 is not selective for acids of similar strength. In this method, a base of known concentration is used to understand the overall acid content of a sample and express it as the main acid present in wine, tartaric acid. This mini titrator is supplied complete with all the materials necessary to perform low and high range measurements of total acidity.
Initial Juice pH:
Juice pH increases during maturation and it can be measured with pH meter. The pH in the juice and wine is a measure of active acidity and thus acidity and pH are related. The pH value is important because it can influence a various factors in the wine, including microbial stability (spoilage), physical stability (protein, tartrate), oxidation level, SO2 activity, color and flavour. If the grapes are harvested at a below optimal juice pH, the wines can be sour and lack character. The pH value that is above 3,5 to 3,6, the wines can be “flat” in character and more prone to microbial infection, have less desirable flavors, and more oxidized and have less color.
For measuring pH in grape and wine Hanna Instruments has numerous solutions. Check them all!!

HI98169

pH meter for wine
HI98169 is a rugged, waterproof, portable pH meter for wine that measures pH and temperature of must in winemaking. This meter is supplied with a specialized pH probe that features an open junction with Clogging Prevention System (CPS・) technology. HI98169 is supplied with FC10483 pH electrode, pH 3.00 buffer solution sachets (2), pH 7.01 buffer solution sachets (2), HI700635 Cleaning solution for wine deposits sachet, HI700636 cleaning solution for wine stains sachet, 100 mL plastic beaker (2), HI920015 micro USB cable, 1.5V AA batteries (4), instruction manual, guidebook for winemakers, and quality certificate in a HI720169 hard carrying case with custom insert.
Choose from seven standard pH buffers and five custom values to obtain up to five point calibration and achieve high precision readings with a 0,001 pH resolution and a pH accuracy of ア0,002. The log-on-demand feature allows users to store up to 200 samples that can later be transferred to a PC with the HI920015 USB cable and HI92000 software.

HI99111

Portable pH Meter for Wine Analysis
HI99111 is a portable, microprocessor-based pH and temperature meter. Main features include: extended pH and temperature ranges; waterproof and compact casing; large dual-line display; low battery detection; automatic pH calibration at one or two points within two memorized buffer sets (standard or NIST); selectable temperature unit (°C or °F).
The FC10483 pH probe features an open junction with Clogging Prevention System (CPSTM) technology, has a builtin temperature sensor for simultaneous temperature compensated pH and temperature readings.
HI99111 is supplied with FC10483 pH/temperature probe with flat tip and Quick Connect DIN connector with 1m (3.3’) cable, pH 3.00 and 7.01 buffer sachets, HI700635 Cleaning solution for wine deposits sachets (2), HI700636 Cleaning solution for wine stains (2), 100 mL beaker, 1.5V AAA batteries (3), calibration certificate of meter, calibration certificate of probe, instruction manual and HI710142 rugged carrying case.

HI10482

pH Electrode for Wine HALO Bluetooth®
The HI10482 HALO is a Bluetooth Smart (Bluetooth 4.0) pH and temperature electrode with Hanna’s Clogging Prevention System (CPS).
This electrode has a unique ground glass junction coupled with a PTFE sleeve to prevent particulates within a sample from clogging the junction. In addition to the specialized junction, the HI10482s glass body and spherical sensing bulb make it ideal for use in a wide variety of applications. All readings are transmitted directly to the HI2202 edgeblu or a compatible Apple or Android device running the Hanna Lab App.
To help you determine the degree of maturity of grape for harvesting check what pH, Brix and TA values your grape should have.
Target values for pH, TA and Brix
Type of grape pH °Brix TA Final pH
Cabernet Sauvignon
3.3-3.4
24-26.5°
0.6-0.7
3.6-3.7
Merlot
3.2-3.4
23-25.5°
0.65-0.8
3.55-3.65
Cabernet Franc
3.2-3.4
23-25.5°
0.65-0.8
3.55-3.6
Malbec
3.2-3.4
23-26°
0.65-0.8
3.55-3.65
Pinot Noir
3.2-3.3
22-25°
0.65-0.8
3.5-3.55
Zinfandel
3.3-3.45
24-28°
0.6-0.75
3.65-3.75
Grenache
3.3-3.45
25-27°
0.6-0.75
3.65-3.75
Petite Sirah
3.3-3.5
25-27°
0.6-0.7
3.6-3.75
Tempranillo
3.3-3.5
24-27°
0.6-0.7
3.65-3.8
Sangiovese
3.2-3.4
23-26°
0.6-0.75
3.65-3.8
Normal Range for
Dry Red Wine:
3.2-3.4
22-27°
0.6-0.7
3.55-3.7
Riesling
2.9-3.2
20-24°
0.7-0.9
3.1-3.4
Gewurztraminer
2.9-3.2
20-24°
0.7-0.9
3.2-3.4
Sauvignon Blanc
2.9-3.3
20-24°
0.7-0.9
3.2-3.4
Pinot Griggio
2.9-3.2
20-24°
0.7-0.9
3.2-3.4
Chardonnay
3.0-3.3
22-25°
0.7-0.9
3.3-3.45
Concord
2.9-3.3
14-19°
0.8-1
3.2-3.45
Niagara
2.9-3.3
14-18°
0.8-1
3.2-3.45
Rosé
2.9-3.3
18-23°
0.7-1
3.2-3.5
Author:
Tajana Mokrović, mag.nutr.