Evaluation by refractometry of the sugar concentration in grape musts, concentrated grape musts and rectified concentrated grape musts (Type-I)

OIV-MA-AS2-02 Évaluation by refractometry of the sugar concentration in grape musts, concentrated grape musts and rectified concentrated grape musts

Type I method

Principle

The refractive index at 20°C, expressed either as an absolute value or as a percentage by mass of sucrose, is given in the appropriate table to provide a means of obtaining the sugar concentration in grams per liter and in grams per kilogram for grape musts, concentrated grape musts and rectified concentrated grape musts.

Apparatus

Abbe refractometer

The refractometer used must be fitted with a scale giving:

either percentage by mass of sucrose to 0.1%;
or refractive indices to four decimal places.

The refractometer must be equipped with a thermometer having a scale extending at least from +15°C to +25°C and with a system for circulating water that will enable measurements to be made at a temperature of 20 ± 5°C. The operating instructions for this instrument must be strictly adhered to, particularly with regard to calibration and the light source.

Preparation of the sample
1. Must and concentrated must

Pass the must, if necessary, through a dry gauze folded into four and, after discarding the first drops of the filtrate, carry out the determination on the filtered product.

3.2. Rectified concentrated must

Depending on the concentration, use either the rectified concentrated must itself or a solution obtained by making up 200 g of rectified concentrated must to 500 g with water, all weighings being carried out accurately.

Procedure

Bring the sample to a temperature close to 20°C.

Place a small test sample on the lower prism of the refractometer, taking care (because the prisms are pressed firmly against each other) that this test sample covers the glass surface uniformly. Carry out the measurement in accordance with the operating instructions of the instrument used.

Read the percentage by mass of sucrose to within 0.1 or read the refractive index to four decimal places.

Carry out at least two determinations on the same prepared sample. Note the temperature t°C.

Calculation

5.1. Temperature correction

Instruments graduated in percentage by mass of sucrose: use Table I to obtain the temperature correction.
Instruments graduated in refractive index: find the index measured at t°C in Table II to obtain (column 1) the corresponding value of the percentage by mass of sucrose at t°C. This value is corrected for temperature and expressed as a concentration at 20°C by means of Table I.
1. Sugar concentration in must and concentrated must

Find the percentage by mass of sucrose at 20°C in Table II and read from the same row the sugar concentration in grams per liter and grams per kilogram. The sugar concentration is expressed in terms of invert sugar to one decimal place.

5.3. Sugar concentration in rectified concentrated must

Find the percentage by mass of sucrose at 20°C in Table III and read from the same row the sugar concentration in grams per liter and grams per kilogram. The sugar concentration is expressed in terms of invert sugar to one decimal place. If the measurement was made on diluted rectified concentrated must, multiply the result by the dilution factor.

5.4. Refractive index of must, concentrated must and rectified concentrated must

Find the percentage by mass of sucrose at 20°C in Table II and read from the same row the refractive index at 20°C. This index is expressed to four decimal places.

Table I Correction to be made in the case where the percentage by mass of saccharose was determined at a temperature different by 20°C.

Temperature

Percentage by mass measured in %

°C

–0,82

–0,87

–0,92

–0,95

–0,99

–0,80

–0,82

–0,87

–0,90

–0,94

–0,74

–0,78

–0,82

–0,84

–0,88

–0,69

–0,73

–0,76

–0,79

–0,82

–0,64

–0,67

–0,71

–0,73

–0,75

–0,59

–0,62

–0,65

–0,67

–0,69

–0,71

–0,72

–0,73

–0,74

–0,75

–0,54

–0,57

–0,59

–0,61

–0,63

–0,64

–0,65

–0,66

–0,67

–0,68

–0,67

–0,49

–0,51

–0,53

–0,55

–0,56

–0,57

–0,58

–0,59

–0,60

–0,61

–0,60

–0,43

–0,45

–0,47

–0,48

–0,50

–0,51

–0,52

–0,53

–0,38

–0,39

–0,40

–0,42

–0,43

–0,44

–0,45

–0,46

–0,45

–0,32

–0,33

–0,34

–0,35

–0,36

–0,37

–0,38

–0,26

–0,27

–0,28

–0,29

–0,30

–0,31

–0,30

–0,20

–0,21

–0,22

–0,23

–0,13

–0,14

–0,15

–0,07

–0,08

R É F É R E N

C E

+0,07

+0,08

+0,14

+0,15

+0,16

+0,15

+0,21

+0,22

+0,23

+0,24

+0,23

+0,29

+0,30

+0,31

+0,32

+0,31

+0,36

+0,37

+0,38

+0,39

+0,40

+0,39

+0,44

+0,45

+0,46

+0,47

+0,48

+0,47

+0,46

+0,52

+0,53

+0,54

+0,55

+0,56

+0,55

+0,54

+0,60

+0,61

+0,62

+0,63

+0,64

+0,65

+0,64

+0,63

+0,62

+0,68

+0,69

+0,70

+0,71

+0,72

+0,73

+0,72

+0,71

+0,70

+0,77

+0,78

+0,79

+0,80

+0,81

+0,82

+0,81

+0,80

+0,79

+0,78

+0,85

+0,87

+0,88

+0,89

+0,90

+0,89

+0,88

+0,87

+0,86

+0,94

+0,95

+0,96

+0,97

+0,98

+0,99

+0,98

+0,97

+0,96

+0,95

+0,94

+1,03

+1,04

+1,05

+1,06

+1,07

+1,08

+1,07

+1,06

+1,05

+1,03

+1,02

+1,12

+1,19

+1,15

+1,16

+1,17

+1,16

+1,15

+1,14

+1,13

+1,12

+1,10

+1,22

+1,23

+1,24

+1,25

+1,26

+1,25

+1,24

+1,23

+1,21

+1,20

+1,18

+1,31

+1,32

+1,33

+1,34

+1,35

+1,34

+1,33

+1,32

+1,30

+1,28

+1,26

+1,41

+1,42

+1,43

+1,44

+1,43

+1,42

+1,40

+1,38

+1,36

+1,34

+1,51

+1,52

+1,53

+1,54

+1,53

+1,52

+1,51

+1,49

+1,47

+1,45

+1,42

+1,61

+1,62

+1,63

+1,62

+1,61

+1,60

+1,58

+1,56

+1,53

+1,50

+1,71

+1,72

+1,73

+1,72

+1,71

+1,70

+1,69

+1,67

+1,64

+1,62

+1,59

It is preferable that the variations in temperature in relation to 20°C do not exceed  5°C.

TABLE II

Table giving the sugar content of musts and concentrated musts in grammes per litre and in grammes per kilogramme, determined using a graduated refractometer, either in percentage by mass of saccharose at 20°C, or refractive index at 20°C. The mass density at 20°C is also given.

Saccharose	Refractive Index	Mass	Sugars in	Sugars in	ABV % vol at 20 °C
% (m/m)	at 20 °C	Density at 20 °C	g/l	g/kg	at 20 °C
10.0	1.34782	1.0391	82.2	79.1	4.89
10.1	1.34798	1.0395	83.3	80.1	4.95
10.2	1.34813	1.0399	84.3	81.1	5.01
10.3	1.34829	1.0403	85.4	82.1	5.08
10.4	1.34844	1.0407	86.5	83.1	5.14
10.5	1.34860	1.0411	87.5	84.1	5.20
10.6	1.34875	1.0415	88.6	85.0	5.27
10.7	1.34891	1.0419	89.6	86.0	5.32
10.8	1.34906	1.0423	90.7	87.0	5.39
10.9	1.34922	1.0427	91.8	88.0	5.46
11.0	1.34937	1.0431	92.8	89.0	5.52
11.1	1.34953	1.0436	93.9	90.0	5.58
11.2	1.34968	1.0440	95.0	91.0	5.65
11.3	1.34984	1.0444	96.0	92.0	5.71
11.4	1.34999	1.0448	97.1	92.9	5.77
11.5	1.35015	1.0452	98.2	93.9	5.84
11.6	1.35031	1.0456	99.3	94.9	5.90
11.7	1.35046	1.0460	100.3	95.9	5.96
11.8	1.35062	1.0464	101.4	96.9	6.03
11.9	1.35077	1.0468	102.5	97.9	6.09
12.0	1.35093	1.0472	103.5	98.9	6.15
12.1	1.35109	1.0477	104.6	99.9	6.22
12.2	1.35124	1.0481	105.7	100.8	6.28
12.3	1.35140	1.0485	106.8	101.8	6.35
12.4	1.35156	1.0489	107.8	102.8	6.41
12.5	1.35171	1.0493	108.9	103.8	6.47
12.6	1.35187	1.0497	110.0	104.8	6.54
12.7	1.35203	1.0501	111.1	105.8	6.60
12.8	1.35219	1.0506	112.2	106.8	6.67
12.9	1.35234	1.0510	113.2	107.8	6.73
13.0	1.35250	1.0514	114.3	108.7	6.79
13.1	1.35266	1.0518	115.4	109.7	6.86
13.2	1.35282	1.0522	116.5	110.7	6.92
13.3	1.35298	1.0527	117.6	111.7	6.99
13.4	1.35313	1.0531	118.7	112.7	7.05
13.5	1.35329	1.0535	119.7	113.7	7.11
13.6	1.35345	1.0539	120.8	114.7	7.18
13.7	1.35361	1.0543	121.9	115.6	7.24
13.8	1.35377	1.0548	123.0	116.6	7.31
13.9	1.35393	1.0552	124.1	117.6	7.38
14.0	1.35408	1.0556	125.2	118.6	7.44
14.1	1.35424	1.0560	126.3	119.6	7.51
14.2	1.35440	1.0564	127.4	120.6	7.57
14.3	1.35456	1.0569	128.5	121.6	7.64
14.4	1.35472	1.0573	129.6	122.5	7.70
14.5	1.35488	1.0577	130.6	123.5	7.76
14.6	1.35504	1.0581	131.7	124.5	7.83
14.7	1.35520	1.0586	132.8	125.5	7.89
14.8	1.35536	1.0590	133.9	126.5	7.96
14.9	1.35552	1.0594	135.0	127.5	8.02

TABLE II - (continued)

Saccharose	Refractive Index	Mass	Sugars in	Sugars in	ABV % vol at 20 °C
% (m/m)	at 20 °C	Density at 20 °C	g/l	g/kg	at 20 °C
15.0	1.35568	1.0598	136.1	128.4	8.09
15.1	1.35584	1.0603	137.2	129.4	8.15
15.2	1.35600	1.0607	138.3	130.4	8.22
15.3	1.35616	1.0611	139.4	131.4	8.28
15.4	1.35632	1.0616	140.5	132.4	8.35
15.5	1.35648	1.0620	141.6	133.4	8.42
15.6	1.35664	1.0624	142.7	134.3	8.48
15.7	1.35680	1.0628	143.8	135.3	8.55
15.8	1.35696	1.0633	144.9	136.3	8.61
15.9	1.35713	1.0637	146.0	137.3	8.68
16.0	1.35729	1.0641	147.1	138.3	8.74
16.1	1.35745	1.0646	148.2	139.3	8.81
16.2	1.35761	1.0650	149.3	140.2	8.87
16.3	1.35777	1.0654	150.5	141.2	8.94
16.4	1.35793	1.0659	151.6	142.2	9.01
16.5	1.35810	1.0663	152.7	143.2	9.07
16.6	1.35826	1.0667	153.8	144.2	9.14
16.7	1.35842	1.0672	154.9	145.1	9.21
16.8	1.35858	1.0676	156.0	146.1	9.27
16.9	1.35874	1.0680	157.1	147.1	9.34
17.0	1.35891	1.0685	158.2	148.1	9.40
17.1	1.35907	1.0689	159.3	149.1	9.47
17.2	1.35923	1.0693	160.4	150.0	9.53
17.3	1.35940	1.0698	161.6	151.0	9.60
17.4	1.35956	1.0702	162.7	152.0	9.67
17.5	1.35972	1.0707	163.8	153.0	9.73
17.6	1.35989	1.0711	164.9	154.0	9.80
17.7	1.36005	1.0715	166.0	154.9	9.87
17.8	1.36021	1.0720	167.1	155.9	9.93
17.9	1.36038	1.0724	168.3	156.9	10.00
18.0	1.36054	1.0729	169.4	157.9	10.07
18.1	1.36070	1.0733	170.5	158.9	10.13
18.2	1.36087	1.0737	171.6	159.8	10.20
18.3	1.36103	1.0742	172.7	160.8	10.26
18.4	1.36120	1.0746	173.9	161.8	10.33
18.5	1.36136	1.0751	175.0	162.8	10.40
18.6	1.36153	1.0755	176.1	163.7	10.47
18.7	1.36169	1.0760	177.2	164.7	10.53
18.8	1.36185	1.0764	178.4	165.7	10.60
18.9	1.36202	1.0768	179.5	166.7	10.67
19.0	1.36219	1.0773	180.6	167.6	10.73
19.1	1.36235	1.0777	181.7	168.6	10.80
19.2	1.36252	1.0782	182.9	169.6	10.87
19.3	1.36268	1.0786	184.0	170.6	10.94
19.4	1.36285	1.0791	185.1	171.5	11.00
19.5	1.36301	1.0795	186.2	172.5	11.07
19.6	1.36318	1.0800	187.4	173.5	11.14
19.7	1.36334	1.0804	188.5	174.5	11.20
19.8	1.36351	1.0809	189.6	175.4	11.27
19.9	1.36368	1.0813	190.8	176.4	11.34

TABLE II - (continued

Saccharose	Refractive Index	Mass	Sugars in	Sugars in	ABV % vol at 20 °C
% (m/m)	at 20 °C	Density at 20 °C	g/l	g/kg	at 20 °C
20.0	1.36384	1.0818	191.9	177.4	11.40
20.1	1.36401	1.0822	193.0	178.4	11.47
20.2	1.36418	1.0827	194.2	179.3	11.54
20.3	1.36434	1.0831	195.3	180.3	11.61
20.4	1.36451	1.0836	196.4	181.3	11.67
20.5	1.36468	1.0840	197.6	182.3	11.74
20.6	1.36484	1.0845	198.7	183.2	11.81
20.7	1.36501	1.0849	199.8	184.2	11.87
20.8	1.36518	1.0854	201.0	185.2	11.95
20.9	1.36535	1.0858	202.1	186.1	12.01
21.0	1.36551	1.0863	203.3	187.1	12.08
21.1	1.36568	1.0867	204.4	188.1	12.15
21.2	1.36585	1.0872	205.5	189.1	12.21
21.3	1.36602	1.0876	206.7	190.0	12.28
21.4	1.36619	1.0881	207.8	191.0	12.35
21.5	1.36635	1.0885	209.0	192.0	12.42
21.6	1.36652	1.0890	210.1	192.9	12.49
21.7	1.36669	1.0895	211.3	193.9	12.56
21.8	1.36686	1.0899	212.4	194.9	12.62
21.9	1.36703	1.0904	213.6	195.9	12.69
22.0	1.36720	1.0908	214.7	196.8	12.76
22.1	1.36737	1.0913	215.9	197.8	12.83
22.2	1.36754	1.0917	217.0	198.8	12.90
22.3	1.36771	1.0922	218.2	199.7	12.97
22.4	1.36787	1.0927	219.3	200.7	13.03
22.5	1.36804	1.0931	220.5	201.7	13.10
22.6	1.36821	1.0936	221.6	202.6	13.17
22.7	1.36838	1.0940	222.8	203.6	13.24
22.8	1.36855	1.0945	223.9	204.6	13.31
22.9	1.36872	1.0950	225.1	205.5	13.38
23.0	1.36889	1.0954	226.2	206.5	13.44
23.1	1.36906	1.0959	227.4	207.5	13.51
23.2	1.36924	1.0964	228.5	208.4	13.58
23.3	1.36941	1.0968	229.7	209.4	13.65
23.4	1.36958	1.0973	230.8	210.4	13.72
23.5	1.36975	1.0977	232.0	211.3	13.79
23.6	1.36992	1.0982	233.2	212.3	13.86
23.7	1.37009	1.0987	234.3	213.3	13.92
23.8	1.37026	1.0991	235.5	214.2	14.00
23.9	1.37043	1.0996	236.6	215.2	14.06
24.0	1.37060	1.1001	237.8	216.2	14.13
24.1	1.37078	1.1005	239.0	217.1	14.20
24.2	1.37095	1.1010	240.1	218.1	14.27
24.3	1.37112	1.1015	241.3	219.1	14.34
24.4	1.37129	1.1019	242.5	220.0	14.41
24.5	1.37146	1.1024	243.6	221.0	14.48
24.6	1.37164	1.1029	244.8	222.0	14.55
24.7	1.37181	1.1033	246.0	222.9	14.62
24.8	1.37198	1.1038	247.1	223.9	14.69
24.9	1.37216	1.1043	248.3	224.8	14.76

TABLE II - (continued

TABLE II - (continued)

Saccharose	Refractive Index	Mass	Sugars in	Sugars in	ABV % vol at 20 °C
% (m/m)	at 20 °C	Density at 20 °C	g/l	g/kg	at 20 °C
35.0	1.39032	1.1537	370.5	321.1	22.02
35.1	1.39051	1.1542	371.8	322.1	22.10
35.2	1.39070	1.1547	373.0	323.0	22.17
35.3	1.39088	1.1552	374.3	324.0	22.24
35.4	1.39107	1.1557	375.5	324.9	22.32
35.5	1.39126	1.1563	376.8	325.9	22.39
35.6	1.39145	1.1568	378.0	326.8	22.46
35.7	1.39164	1.1573	379.3	327.8	22.54
35.8	1.39182	1.1578	380.6	328.7	22.62
35.9	1.39201	1.1583	381.8	329.6	22.69
36.0	1.39220	1.1588	383.1	330.6	22.77
36.1	1.39239	1.1593	384.4	331.5	22.84
36.2	1.39258	1.1598	385.6	332.5	22.92
36.3	1.39277	1.1603	386.9	333.4	22.99
36.4	1.39296	1.1609	388.1	334.4	23.06
36.5	1.39314	1.1614	389.4	335.3	23.14
36.6	1.39333	1.1619	390.7	336.3	23.22
36.7	1.39352	1.1624	392.0	337.2	23.30
36.8	1.39371	1.1629	393.2	338.1	23.37
36.9	1.39390	1.1634	394.5	339.1	23.45
37.0	1.39409	1.1640	395.8	340.0	23.52
37.1	1.39428	1.1645	397.0	341.0	23.59
37.2	1.39447	1.1650	398.3	341.9	23.67
37.3	1.39466	1.1655	399.6	342.9	23.75
37.4	1.39485	1.1660	400.9	343.8	23.83
37.5	1.39504	1.1665	402.1	344.7	23.90
37.6	1.39524	1.1671	403.4	345.7	23.97
37.7	1.39543	1.1676	404.7	346.6	24.05
37.8	1.39562	1.1681	406.0	347.6	24.13
37.9	1.39581	1.1686	407.3	348.5	24.21
38.0	1.39600	1.1691	408.6	349.4	24.28
38.1	1.39619	1.1697	409.8	350.4	24.35
38.2	1.39638	1.1702	411.1	351.3	24.43
38.3	1.39658	1.1707	412.4	352.3	24.51
38.4	1.39677	1.1712	413.7	353.2	24.59
38.5	1.39696	1.1717	415.0	354.2	24.66
38.6	1.39715	1.1723	416.3	355.1	24.74
38.7	1.39734	1.1728	417.6	356.0	24.82
38.8	1.39754	1.1733	418.8	357.0	24.89
38.9	1.39773	1.1738	420.1	357.9	24.97
39.0	1.39792	1.1744	421.4	358.9	25.04
39.1	1.39812	1.1749	422.7	359.8	25.12
39.2	1.39831	1.1754	424.0	360.7	25.20
39.3	1.39850	1.1759	425.3	361.7	25.28
39.4	1.39870	1.1765	426.6	362.6	25.35
39.5	1.39889	1.1770	427.9	363.6	25.43
39.6	1.39908	1.1775	429.2	364.5	25.51
39.7	1.39928	1.1780	430.5	365.4	25.58
39.8	1.39947	1.1786	431.8	366.4	25.66
39.9	1.39967	1.1791	433.1	367.3	25.74

TABLE II - (continued)

Saccharose	Refractive Index	Mass	Sugars in	Sugars in	ABV % vol at 20 °C
% (m/m)	at 20 °C	Density at 20 °C	g/l	g/kg	at 20 °C
40.0	1.39986	1.1796	434.4	368.3	25.82
40.1	1.40006	1.1801	435.7	369.2	25.89
40.2	1.40025	1.1807	437.0	370.1	25.97
40.3	1.40044	1.1812	438.3	371.1	26.05
40.4	1.40064	1.1817	439.6	372.0	26.13
40.5	1.40083	1.1823	440.9	373.0	26.20
40.6	1.40103	1.1828	442.2	373.9	26.28
40.7	1.40123	1.1833	443.6	374.8	26.36
40.8	1.40142	1.1839	444.9	375.8	26.44
40.9	1.40162	1.1844	446.2	376.7	26.52
41.0	1.40181	1.1849	447.5	377.7	26.59
41.1	1.40201	1.1855	448.8	378.6	26.67
41.2	1.40221	1.1860	450.1	379.5	26.75
41.3	1.40240	1.1865	451.4	380.5	26.83
41.4	1.40260	1.1871	452.8	381.4	26.91
41.5	1.40280	1.1876	454.1	382.3	26.99
41.6	1.40299	1.1881	455.4	383.3	27.06
41.7	1.40319	1.1887	456.7	384.2	27.14
41.8	1.40339	1.1892	458.0	385.2	27.22
41.9	1.40358	1.1897	459.4	386.1	27.30
42.0	1.40378	1.1903	460.7	387.0	27.38
42.1	1.40398	1.1908	462.0	388.0	27.46
42.2	1.40418	1.1913	463.3	388.9	27.53
42.3	1.40437	1.1919	464.7	389.9	27.62
42.4	1.40457	1.1924	466.0	390.8	27.69
42.5	1.40477	1.1929	467.3	391.7	27.77
42.6	1.40497	1.1935	468.6	392.7	27.85
42.7	1.40517	1.1940	470.0	393.6	27.93
42.8	1.40537	1.1946	471.3	394.5	28.01
42.9	1.40557	1.1951	472.6	395.5	28.09
43.0	1.40576	1.1956	474.0	396.4	28.17
43.1	1.40596	1.1962	475.3	397.3	28.25
43.2	1.40616	1.1967	476.6	398.3	28.32
43.3	1.40636	1.1973	478.0	399.2	28.41
43.4	1.40656	1.1978	479.3	400.2	28.48
43.5	1.40676	1.1983	480.7	401.1	28.57
43.6	1.40696	1.1989	482.0	402.0	28.65
43.7	1.40716	1.1994	483.3	403.0	28.72
43.8	1.40736	1.2000	484.7	403.9	28.81
43.9	1.40756	1.2005	486.0	404.8	28.88
44.0	1.40776	1.2011	487.4	405.8	28.97
44.1	1.40796	1.2016	488.7	406.7	29.04
44.2	1.40817	1.2022	490.1	407.6	29.13
44.3	1.40837	1.2027	491.4	408.6	29.20
44.4	1.40857	1.2032	492.8	409.5	29.29
44.5	1.40877	1.2038	494.1	410.4	29.36
44.6	1.40897	1.2043	495.5	411.4	29.45
44.7	1.40917	1.2049	496.8	412.3	29.52
44.8	1.40937	1.2054	498.2	413.3	29.61
44.9	1.40958	1.2060	499.5	414.2	29.69

TABLE II (continued)

Saccharose

Refractive Index

Mass

Sugars in

ABV % vol

at 20 °C

Compendium of International Methods of Wine and Must Analysis

Evaluation by refractometry of the sugar concentration in grape musts, concentrated grape musts and rectified concentrated grape musts (Type-I)

OIV-MA-AS2-02 Évaluation by refractometry of the sugar concentration in grape musts, concentrated grape musts and rectified concentrated grape musts